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Revision 1.389 by root, Tue Oct 4 05:34:50 2011 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent - provide framework for multiple event loops	3	AnyEvent - the DBI of event loop programming
4		4
5	EV, Event, Coro::EV, Coro::Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event loops	5	EV, Event, Glib, Tk, Perl, Event::Lib, Irssi, rxvt-unicode, IO::Async, Qt,
		6	FLTK and POE are various supported event loops/environments.
6		7
7	=head1 SYNOPSIS	8	=head1 SYNOPSIS
8		9
9	use AnyEvent;	10	use AnyEvent;
10		11
		12	# if you prefer function calls, look at the AE manpage for
		13	# an alternative API.
		14
		15	# file handle or descriptor readable
11	my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub {	16	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
		17
		18	# one-shot or repeating timers
		19	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
		20	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...);
		21
		22	print AnyEvent->now; # prints current event loop time
		23	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
		24
		25	# POSIX signal
		26	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
		27
		28	# child process exit
		29	my $w = AnyEvent->child (pid => $pid, cb => sub {
		30	my ($pid, $status) = @_;
12	...	31	...
13	});	32	});
14		33
15	my $w = AnyEvent->timer (after => $seconds, cb => sub {	34	# called when event loop idle (if applicable)
16	...	35	my $w = AnyEvent->idle (cb => sub { ... });
17	});
18		36
19	my $w = AnyEvent->condvar; # stores whether a condition was flagged	37	my $w = AnyEvent->condvar; # stores whether a condition was flagged
		38	$w->send; # wake up current and all future recv's
20	$w->wait; # enters "main loop" till $condvar gets ->broadcast	39	$w->recv; # enters "main loop" till $condvar gets ->send
21	$w->broadcast; # wake up current and all future wait's	40	# use a condvar in callback mode:
		41	$w->cb (sub { $_[0]->recv });
		42
		43	=head1 INTRODUCTION/TUTORIAL
		44
		45	This manpage is mainly a reference manual. If you are interested
		46	in a tutorial or some gentle introduction, have a look at the
		47	L<AnyEvent::Intro> manpage.
		48
		49	=head1 SUPPORT
		50
		51	An FAQ document is available as L<AnyEvent::FAQ>.
		52
		53	There also is a mailinglist for discussing all things AnyEvent, and an IRC
		54	channel, too.
		55
		56	See the AnyEvent project page at the B<Schmorpforge Ta-Sa Software
		57	Repository>, at L<http://anyevent.schmorp.de>, for more info.
22		58
23	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)	59	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
24		60
25	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	61	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
26	nowadays. So what is different about AnyEvent?	62	nowadays. So what is different about AnyEvent?
27		63
28	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of	64	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
29	policy> and AnyEvent is I<small and efficient>.	65	policy> and AnyEvent is I<small and efficient>.
30		66
31	First and foremost, I<AnyEvent is not an event model> itself, it only	67	First and foremost, I<AnyEvent is not an event model> itself, it only
32	interfaces to whatever event model the main program happens to use in a	68	interfaces to whatever event model the main program happens to use, in a
33	pragmatic way. For event models and certain classes of immortals alike,	69	pragmatic way. For event models and certain classes of immortals alike,
34	the statement "there can only be one" is a bitter reality: In general,	70	the statement "there can only be one" is a bitter reality: In general,
35	only one event loop can be active at the same time in a process. AnyEvent	71	only one event loop can be active at the same time in a process. AnyEvent
36	helps hiding the differences between those event loops.	72	cannot change this, but it can hide the differences between those event
		73	loops.
37		74
38	The goal of AnyEvent is to offer module authors the ability to do event	75	The goal of AnyEvent is to offer module authors the ability to do event
39	programming (waiting for I/O or timer events) without subscribing to a	76	programming (waiting for I/O or timer events) without subscribing to a
40	religion, a way of living, and most importantly: without forcing your	77	religion, a way of living, and most importantly: without forcing your
41	module users into the same thing by forcing them to use the same event	78	module users into the same thing by forcing them to use the same event
42	model you use.	79	model you use.
43		80
44	For modules like POE or IO::Async (which is a total misnomer as it is	81	For modules like POE or IO::Async (which is a total misnomer as it is
45	actually doing all I/O I<synchronously>...), using them in your module is	82	actually doing all I/O I<synchronously>...), using them in your module is
46	like joining a cult: After you joined, you are dependent on them and you	83	like joining a cult: After you join, you are dependent on them and you
47	cannot use anything else, as it is simply incompatible to everything that	84	cannot use anything else, as they are simply incompatible to everything
48	isn't itself. What's worse, all the potential users of your module are	85	that isn't them. What's worse, all the potential users of your
49	I<also> forced to use the same event loop you use.	86	module are I<also> forced to use the same event loop you use.
50		87
51	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	88	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
52	fine. AnyEvent + Tk works fine etc. etc. but none of these work together	89	fine. AnyEvent + Tk works fine etc. etc. but none of these work together
53	with the rest: POE + IO::Async? no go. Tk + Event? no go. Again: if	90	with the rest: POE + EV? No go. Tk + Event? No go. Again: if your module
54	your module uses one of those, every user of your module has to use it,	91	uses one of those, every user of your module has to use it, too. But if
55	too. But if your module uses AnyEvent, it works transparently with all	92	your module uses AnyEvent, it works transparently with all event models it
56	event models it supports (including stuff like POE and IO::Async, as long	93	supports (including stuff like IO::Async, as long as those use one of the
57	as those use one of the supported event loops. It is trivial to add new	94	supported event loops. It is easy to add new event loops to AnyEvent, too,
58	event loops to AnyEvent, too, so it is future-proof).	95	so it is future-proof).
59		96
60	In addition to being free of having to use I<the one and only true event	97	In addition to being free of having to use I<the one and only true event
61	model>, AnyEvent also is free of bloat and policy: with POE or similar	98	model>, AnyEvent also is free of bloat and policy: with POE or similar
62	modules, you get an enourmous amount of code and strict rules you have to	99	modules, you get an enormous amount of code and strict rules you have to
63	follow. AnyEvent, on the other hand, is lean and up to the point, by only	100	follow. AnyEvent, on the other hand, is lean and to the point, by only
64	offering the functionality that is necessary, in as thin as a wrapper as	101	offering the functionality that is necessary, in as thin as a wrapper as
65	technically possible.	102	technically possible.
66		103
		104	Of course, AnyEvent comes with a big (and fully optional!) toolbox
		105	of useful functionality, such as an asynchronous DNS resolver, 100%
		106	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
		107	such as Windows) and lots of real-world knowledge and workarounds for
		108	platform bugs and differences.
		109
67	Of course, if you want lots of policy (this can arguably be somewhat	110	Now, if you I<do want> lots of policy (this can arguably be somewhat
68	useful) and you want to force your users to use the one and only event	111	useful) and you want to force your users to use the one and only event
69	model, you should I<not> use this module.	112	model, you should I<not> use this module.
70		113
71
72	=head1 DESCRIPTION	114	=head1 DESCRIPTION
73		115
74	L<AnyEvent> provides an identical interface to multiple event loops. This	116	L<AnyEvent> provides a uniform interface to various event loops. This
75	allows module authors to utilise an event loop without forcing module	117	allows module authors to use event loop functionality without forcing
76	users to use the same event loop (as only a single event loop can coexist	118	module users to use a specific event loop implementation (since more
77	peacefully at any one time).	119	than one event loop cannot coexist peacefully).
78		120
79	The interface itself is vaguely similar, but not identical to the L<Event>	121	The interface itself is vaguely similar, but not identical to the L<Event>
80	module.	122	module.
81		123
82	During the first call of any watcher-creation method, the module tries	124	During the first call of any watcher-creation method, the module tries
83	to detect the currently loaded event loop by probing whether one of the	125	to detect the currently loaded event loop by probing whether one of the
84	following modules is already loaded: L<Coro::EV>, L<Coro::Event>, L<EV>,	126	following modules is already loaded: L<EV>, L<AnyEvent::Loop>,
85	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
86	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
87	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
88	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
89	be successfully loaded will be used. If, after this, still none could be	131	the other two are not normally tried.
90	found, AnyEvent will fall back to a pure-perl event loop, which is not
91	very efficient, but should work everywhere.
92		132
93	Because AnyEvent first checks for modules that are already loaded, loading	133	Because AnyEvent first checks for modules that are already loaded, loading
94	an event model explicitly before first using AnyEvent will likely make	134	an event model explicitly before first using AnyEvent will likely make
95	that model the default. For example:	135	that model the default. For example:
96		136
…		…
98	use AnyEvent;	138	use AnyEvent;
99		139
100	# .. AnyEvent will likely default to Tk	140	# .. AnyEvent will likely default to Tk
101		141
102	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
103	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,
104	use AnyEvent so their modules work together with others seamlessly...	144	as very few modules hardcode event loops without announcing this very
		145	loudly.
105		146
106	The pure-perl implementation of AnyEvent is called	147	The pure-perl implementation of AnyEvent is called C<AnyEvent::Loop>. Like
107	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
108	explicitly.	149	availability of that event loop :)
109		150
110	=head1 WATCHERS	151	=head1 WATCHERS
111		152
112	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
113	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
114	the callback to call, the filehandle to watch, etc.	155	the callback to call, the file handle to watch, etc.
115		156
116	These watchers are normal Perl objects with normal Perl lifetime. After	157	These watchers are normal Perl objects with normal Perl lifetime. After
117	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
118	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
119	is in control).	160	is in control).
120		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
121	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
122	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
123	to it).	170	to it).
124		171
125	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.
126		173
127	Many watchers either are used with "recursion" (repeating timers for	174	Many watchers either are used with "recursion" (repeating timers for
128	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.
129		176
130	An any way to achieve that is this pattern:	177	One way to achieve that is this pattern:
131		178
132	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	179	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
133	# you can use $w here, for example to undef it	180	# you can use $w here, for example to undef it
134	undef $w;	181	undef $w;
135	});	182	});
136		183
137	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,
138	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
139	declared.	186	declared.
140		187
141	=head2 I/O WATCHERS	188	=head2 I/O WATCHERS
142		189
		190	$w = AnyEvent->io (
		191	fh => <filehandle_or_fileno>,
		192	poll => <"r" or "w">,
		193	cb => <callback>,
		194	);
		195
143	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
144	with the following mandatory key-value pairs as arguments:	197	with the following mandatory key-value pairs as arguments:
145		198
146	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
147	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
148	which creates a watcher waiting for "r"eadable or "w"ritable events,	207	watcher waiting for "r"eadable or "w"ritable events, respectively.
		208
149	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.
150	becomes ready.
151		210
152	Although the callback might get passed parameters, their value and	211	Although the callback might get passed parameters, their value and
153	presence is undefined and you cannot rely on them. Portable AnyEvent	212	presence is undefined and you cannot rely on them. Portable AnyEvent
154	callbacks cannot use arguments passed to I/O watcher callbacks.	213	callbacks cannot use arguments passed to I/O watcher callbacks.
155		214
156	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.
157	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
158	underlying file descriptor.	217	underlying file descriptor.
159		218
160	Some event loops issue spurious readyness notifications, so you should	219	Some event loops issue spurious readiness notifications, so you should
161	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
162	handles.	221	handles.
163		222
164	Example:
165
166	# 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
167	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	226	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
168	chomp (my $input = <STDIN>);	227	chomp (my $input = <STDIN>);
169	warn "read: $input\n";	228	warn "read: $input\n";
170	undef $w;	229	undef $w;
171	});	230	});
172		231
173	=head2 TIME WATCHERS	232	=head2 TIME WATCHERS
174		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
175	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 >>
176	method with the following mandatory arguments:	243	method with the following mandatory arguments:
177		244
178	C<after> specifies after how many seconds (fractional values are	245	C<after> specifies after how many seconds (fractional values are
179	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
…		…
181		248
182	Although the callback might get passed parameters, their value and	249	Although the callback might get passed parameters, their value and
183	presence is undefined and you cannot rely on them. Portable AnyEvent	250	presence is undefined and you cannot rely on them. Portable AnyEvent
184	callbacks cannot use arguments passed to time watcher callbacks.	251	callbacks cannot use arguments passed to time watcher callbacks.
185		252
186	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
187	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
188	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.
189		258
190	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.
191		262
192	# fire an event after 7.7 seconds	263	Example: fire an event after 7.7 seconds.
		264
193	my $w = AnyEvent->timer (after => 7.7, cb => sub {	265	my $w = AnyEvent->timer (after => 7.7, cb => sub {
194	warn "timeout\n";	266	warn "timeout\n";
195	});	267	});
196		268
197	# to cancel the timer:	269	# to cancel the timer:
198	undef $w;	270	undef $w;
199		271
200	Example 2:
201
202	# 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.
203	my $w;
204		273
205	my $cb = sub {
206	# cancel the old timer while creating a new one
207	$w = AnyEvent->timer (after => 1, cb => $cb);	274	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		275	warn "timeout\n";
208	};	276	};
209
210	# start the "loop" by creating the first watcher
211	$w = AnyEvent->timer (after => 0.5, cb => $cb);
212		277
213	=head3 TIMING ISSUES	278	=head3 TIMING ISSUES
214		279
215	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
216	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
…		…
218		283
219	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
220	use absolute time internally. This makes a difference when your clock	285	use absolute time internally. This makes a difference when your clock
221	"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
222	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
223	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.
224		289
225	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
226	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
227	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)
228	timers.	293	timers.
229		294
230	AnyEvent always prefers relative timers, if available, matching the	295	AnyEvent always prefers relative timers, if available, matching the
231	AnyEvent API.	296	AnyEvent API.
232		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
233	=head2 SIGNAL WATCHERS	383	=head2 SIGNAL WATCHERS
234		384
		385	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		386
235	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
236	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
237	be invoked whenever a signal occurs.	389	callback to be invoked whenever a signal occurs.
238		390
239	Although the callback might get passed parameters, their value and	391	Although the callback might get passed parameters, their value and
240	presence is undefined and you cannot rely on them. Portable AnyEvent	392	presence is undefined and you cannot rely on them. Portable AnyEvent
241	callbacks cannot use arguments passed to signal watcher callbacks.	393	callbacks cannot use arguments passed to signal watcher callbacks.
242		394
243	Multiple signal occurances can be clumped together into one callback	395	Multiple signal occurrences can be clumped together into one callback
244	invocation, and callback invocation will be synchronous. synchronous means	396	invocation, and callback invocation will be synchronous. Synchronous means
245	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,
246	but it is guarenteed not to interrupt any other callbacks.	398	but it is guaranteed not to interrupt any other callbacks.
247		399
248	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
249	between multiple watchers.	401	between multiple watchers, and AnyEvent will ensure that signals will not
		402	interrupt your program at bad times.
250		403
251	This watcher might use C<%SIG>, so programs overwriting those signals	404	This watcher might use C<%SIG> (depending on the event loop used),
252	directly will likely not work correctly.	405	so programs overwriting those signals directly will likely not work
		406	correctly.
253		407
254	Example: exit on SIGINT	408	Example: exit on SIGINT
255		409
256	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	410	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
257		411
		412	=head3 Restart Behaviour
		413
		414	While restart behaviour is up to the event loop implementation, most will
		415	not restart syscalls (that includes L<Async::Interrupt> and AnyEvent's
		416	pure perl implementation).
		417
		418	=head3 Safe/Unsafe Signals
		419
		420	Perl signals can be either "safe" (synchronous to opcode handling)
		421	or "unsafe" (asynchronous) - the former might delay signal delivery
		422	indefinitely, the latter might corrupt your memory.
		423
		424	AnyEvent signal handlers are, in addition, synchronous to the event loop,
		425	i.e. they will not interrupt your running perl program but will only be
		426	called as part of the normal event handling (just like timer, I/O etc.
		427	callbacks, too).
		428
		429	=head3 Signal Races, Delays and Workarounds
		430
		431	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support
		432	attaching callbacks to signals in a generic way, which is a pity,
		433	as you cannot do race-free signal handling in perl, requiring
		434	C libraries for this. AnyEvent will try to do its best, which
		435	means in some cases, signals will be delayed. The maximum time
		436	a signal might be delayed is 10 seconds by default, but can
		437	be overriden via C<$ENV{PERL_ANYEVENT_MAX_SIGNAL_LATENCY}> or
		438	C<$AnyEvent::MAX_SIGNAL_LATENCY> - see the Ö<ENVIRONMENT VARIABLES>
		439	section for details.
		440
		441	All these problems can be avoided by installing the optional
		442	L<Async::Interrupt> module, which works with most event loops. It will not
		443	work with inherently broken event loops such as L<Event> or L<Event::Lib>
		444	(and not with L<POE> currently). For those, you just have to suffer the
		445	delays.
		446
258	=head2 CHILD PROCESS WATCHERS	447	=head2 CHILD PROCESS WATCHERS
259		448
		449	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		450
260	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.
261		452
262	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,
263	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
264	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
265	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
266	and exit status (as returned by waitpid), so unlike other watcher types,	457	(stopped/continued).
267	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).
268		467
269	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
270	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
271	have exited already (and no SIGCHLD will be sent anymore).	470	have exited already (and no SIGCHLD will be sent anymore).
272		471
273	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
274	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
275	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.
276		478
277	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
278	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
279	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.
280		487
281	Example: fork a process and wait for it	488	Example: fork a process and wait for it
282		489
283	my $done = AnyEvent->condvar;	490	my $done = AnyEvent->condvar;
284		491
285	AnyEvent::detect; # force event module to be initialised
286
287	my $pid = fork or exit 5;	492	my $pid = fork or exit 5;
288		493
289	my $w = AnyEvent->child (	494	my $w = AnyEvent->child (
290	pid => $pid,	495	pid => $pid,
291	cb => sub {	496	cb => sub {
292	my ($pid, $status) = @_;	497	my ($pid, $status) = @_;
293	warn "pid $pid exited with status $status";	498	warn "pid $pid exited with status $status";
294	$done->broadcast;	499	$done->send;
295	},	500	},
296	);	501	);
297		502
298	# do something else, then wait for process exit	503	# do something else, then wait for process exit
299	$done->wait;	504	$done->recv;
		505
		506	=head2 IDLE WATCHERS
		507
		508	$w = AnyEvent->idle (cb => <callback>);
		509
		510	This will repeatedly invoke the callback after the process becomes idle,
		511	until either the watcher is destroyed or new events have been detected.
		512
		513	Idle watchers are useful when there is a need to do something, but it
		514	is not so important (or wise) to do it instantly. The callback will be
		515	invoked only when there is "nothing better to do", which is usually
		516	defined as "all outstanding events have been handled and no new events
		517	have been detected". That means that idle watchers ideally get invoked
		518	when the event loop has just polled for new events but none have been
		519	detected. Instead of blocking to wait for more events, the idle watchers
		520	will be invoked.
		521
		522	Unfortunately, most event loops do not really support idle watchers (only
		523	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		524	will simply call the callback "from time to time".
		525
		526	Example: read lines from STDIN, but only process them when the
		527	program is otherwise idle:
		528
		529	my @lines; # read data
		530	my $idle_w;
		531	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		532	push @lines, scalar <STDIN>;
		533
		534	# start an idle watcher, if not already done
		535	$idle_w ||= AnyEvent->idle (cb => sub {
		536	# handle only one line, when there are lines left
		537	if (my $line = shift @lines) {
		538	print "handled when idle: $line";
		539	} else {
		540	# otherwise disable the idle watcher again
		541	undef $idle_w;
		542	}
		543	});
		544	});
300		545
301	=head2 CONDITION VARIABLES	546	=head2 CONDITION VARIABLES
302		547
		548	$cv = AnyEvent->condvar;
		549
		550	$cv->send (<list>);
		551	my @res = $cv->recv;
		552
		553	If you are familiar with some event loops you will know that all of them
		554	require you to run some blocking "loop", "run" or similar function that
		555	will actively watch for new events and call your callbacks.
		556
		557	AnyEvent is slightly different: it expects somebody else to run the event
		558	loop and will only block when necessary (usually when told by the user).
		559
		560	The tool to do that is called a "condition variable", so called because
		561	they represent a condition that must become true.
		562
		563	Now is probably a good time to look at the examples further below.
		564
303	Condition variables can be created by calling the C<< AnyEvent->condvar >>	565	Condition variables can be created by calling the C<< AnyEvent->condvar
304	method without any arguments.	566	>> method, usually without arguments. The only argument pair allowed is
		567	C<cb>, which specifies a callback to be called when the condition variable
		568	becomes true, with the condition variable as the first argument (but not
		569	the results).
305		570
306	A condition variable waits for a condition - precisely that the C<<	571	After creation, the condition variable is "false" until it becomes "true"
307	->broadcast >> method has been called.	572	by calling the C<send> method (or calling the condition variable as if it
		573	were a callback, read about the caveats in the description for the C<<
		574	->send >> method).
308		575
309	They are very useful to signal that a condition has been fulfilled, for	576	Since condition variables are the most complex part of the AnyEvent API, here are
		577	some different mental models of what they are - pick the ones you can connect to:
		578
		579	=over 4
		580
		581	=item * Condition variables are like callbacks - you can call them (and pass them instead
		582	of callbacks). Unlike callbacks however, you can also wait for them to be called.
		583
		584	=item * Condition variables are signals - one side can emit or send them,
		585	the other side can wait for them, or install a handler that is called when
		586	the signal fires.
		587
		588	=item * Condition variables are like "Merge Points" - points in your program
		589	where you merge multiple independent results/control flows into one.
		590
		591	=item * Condition variables represent a transaction - functions that start
		592	some kind of transaction can return them, leaving the caller the choice
		593	between waiting in a blocking fashion, or setting a callback.
		594
		595	=item * Condition variables represent future values, or promises to deliver
		596	some result, long before the result is available.
		597
		598	=back
		599
		600	Condition variables are very useful to signal that something has finished,
310	example, if you write a module that does asynchronous http requests,	601	for example, if you write a module that does asynchronous http requests,
311	then a condition variable would be the ideal candidate to signal the	602	then a condition variable would be the ideal candidate to signal the
312	availability of results.	603	availability of results. The user can either act when the callback is
		604	called or can synchronously C<< ->recv >> for the results.
313		605
314	You can also use condition variables to block your main program until	606	You can also use them to simulate traditional event loops - for example,
315	an event occurs - for example, you could C<< ->wait >> in your main	607	you can block your main program until an event occurs - for example, you
316	program until the user clicks the Quit button in your app, which would C<<	608	could C<< ->recv >> in your main program until the user clicks the Quit
317	->broadcast >> the "quit" event.	609	button of your app, which would C<< ->send >> the "quit" event.
318		610
319	Note that condition variables recurse into the event loop - if you have	611	Note that condition variables recurse into the event loop - if you have
320	two pirces of code that call C<< ->wait >> in a round-robbin fashion, you	612	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
321	lose. Therefore, condition variables are good to export to your caller, but	613	lose. Therefore, condition variables are good to export to your caller, but
322	you should avoid making a blocking wait yourself, at least in callbacks,	614	you should avoid making a blocking wait yourself, at least in callbacks,
323	as this asks for trouble.	615	as this asks for trouble.
324		616
325	This object has two methods:	617	Condition variables are represented by hash refs in perl, and the keys
		618	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
		619	easy (it is often useful to build your own transaction class on top of
		620	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
		621	its C<new> method in your own C<new> method.
		622
		623	There are two "sides" to a condition variable - the "producer side" which
		624	eventually calls C<< -> send >>, and the "consumer side", which waits
		625	for the send to occur.
		626
		627	Example: wait for a timer.
		628
		629	# condition: "wait till the timer is fired"
		630	my $timer_fired = AnyEvent->condvar;
		631
		632	# create the timer - we could wait for, say
		633	# a handle becomign ready, or even an
		634	# AnyEvent::HTTP request to finish, but
		635	# in this case, we simply use a timer:
		636	my $w = AnyEvent->timer (
		637	after => 1,
		638	cb => sub { $timer_fired->send },
		639	);
		640
		641	# this "blocks" (while handling events) till the callback
		642	# calls ->send
		643	$timer_fired->recv;
		644
		645	Example: wait for a timer, but take advantage of the fact that condition
		646	variables are also callable directly.
		647
		648	my $done = AnyEvent->condvar;
		649	my $delay = AnyEvent->timer (after => 5, cb => $done);
		650	$done->recv;
		651
		652	Example: Imagine an API that returns a condvar and doesn't support
		653	callbacks. This is how you make a synchronous call, for example from
		654	the main program:
		655
		656	use AnyEvent::CouchDB;
		657
		658	...
		659
		660	my @info = $couchdb->info->recv;
		661
		662	And this is how you would just set a callback to be called whenever the
		663	results are available:
		664
		665	$couchdb->info->cb (sub {
		666	my @info = $_[0]->recv;
		667	});
		668
		669	=head3 METHODS FOR PRODUCERS
		670
		671	These methods should only be used by the producing side, i.e. the
		672	code/module that eventually sends the signal. Note that it is also
		673	the producer side which creates the condvar in most cases, but it isn't
		674	uncommon for the consumer to create it as well.
326		675
327	=over 4	676	=over 4
328		677
		678	=item $cv->send (...)
		679
		680	Flag the condition as ready - a running C<< ->recv >> and all further
		681	calls to C<recv> will (eventually) return after this method has been
		682	called. If nobody is waiting the send will be remembered.
		683
		684	If a callback has been set on the condition variable, it is called
		685	immediately from within send.
		686
		687	Any arguments passed to the C<send> call will be returned by all
		688	future C<< ->recv >> calls.
		689
		690	Condition variables are overloaded so one can call them directly (as if
		691	they were a code reference). Calling them directly is the same as calling
		692	C<send>.
		693
		694	=item $cv->croak ($error)
		695
		696	Similar to send, but causes all calls to C<< ->recv >> to invoke
		697	C<Carp::croak> with the given error message/object/scalar.
		698
		699	This can be used to signal any errors to the condition variable
		700	user/consumer. Doing it this way instead of calling C<croak> directly
		701	delays the error detection, but has the overwhelming advantage that it
		702	diagnoses the error at the place where the result is expected, and not
		703	deep in some event callback with no connection to the actual code causing
		704	the problem.
		705
		706	=item $cv->begin ([group callback])
		707
329	=item $cv->wait	708	=item $cv->end
330		709
331	Wait (blocking if necessary) until the C<< ->broadcast >> method has been	710	These two methods can be used to combine many transactions/events into
332	called on c<$cv>, while servicing other watchers normally.	711	one. For example, a function that pings many hosts in parallel might want
		712	to use a condition variable for the whole process.
333		713
		714	Every call to C<< ->begin >> will increment a counter, and every call to
		715	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
		716	>>, the (last) callback passed to C<begin> will be executed, passing the
		717	condvar as first argument. That callback is I<supposed> to call C<< ->send
		718	>>, but that is not required. If no group callback was set, C<send> will
		719	be called without any arguments.
		720
		721	You can think of C<< $cv->send >> giving you an OR condition (one call
		722	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		723	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		724
		725	Let's start with a simple example: you have two I/O watchers (for example,
		726	STDOUT and STDERR for a program), and you want to wait for both streams to
		727	close before activating a condvar:
		728
		729	my $cv = AnyEvent->condvar;
		730
		731	$cv->begin; # first watcher
		732	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		733	defined sysread $fh1, my $buf, 4096
		734	or $cv->end;
		735	});
		736
		737	$cv->begin; # second watcher
		738	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		739	defined sysread $fh2, my $buf, 4096
		740	or $cv->end;
		741	});
		742
		743	$cv->recv;
		744
		745	This works because for every event source (EOF on file handle), there is
		746	one call to C<begin>, so the condvar waits for all calls to C<end> before
		747	sending.
		748
		749	The ping example mentioned above is slightly more complicated, as the
		750	there are results to be passwd back, and the number of tasks that are
		751	begun can potentially be zero:
		752
		753	my $cv = AnyEvent->condvar;
		754
		755	my %result;
		756	$cv->begin (sub { shift->send (\%result) });
		757
		758	for my $host (@list_of_hosts) {
		759	$cv->begin;
		760	ping_host_then_call_callback $host, sub {
		761	$result{$host} = ...;
		762	$cv->end;
		763	};
		764	}
		765
		766	$cv->end;
		767
		768	This code fragment supposedly pings a number of hosts and calls
		769	C<send> after results for all then have have been gathered - in any
		770	order. To achieve this, the code issues a call to C<begin> when it starts
		771	each ping request and calls C<end> when it has received some result for
		772	it. Since C<begin> and C<end> only maintain a counter, the order in which
		773	results arrive is not relevant.
		774
		775	There is an additional bracketing call to C<begin> and C<end> outside the
		776	loop, which serves two important purposes: first, it sets the callback
		777	to be called once the counter reaches C<0>, and second, it ensures that
		778	C<send> is called even when C<no> hosts are being pinged (the loop
		779	doesn't execute once).
		780
		781	This is the general pattern when you "fan out" into multiple (but
		782	potentially zero) subrequests: use an outer C<begin>/C<end> pair to set
		783	the callback and ensure C<end> is called at least once, and then, for each
		784	subrequest you start, call C<begin> and for each subrequest you finish,
		785	call C<end>.
		786
		787	=back
		788
		789	=head3 METHODS FOR CONSUMERS
		790
		791	These methods should only be used by the consuming side, i.e. the
		792	code awaits the condition.
		793
		794	=over 4
		795
		796	=item $cv->recv
		797
		798	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
		799	>> methods have been called on C<$cv>, while servicing other watchers
		800	normally.
		801
334	You can only wait once on a condition - additional calls will return	802	You can only wait once on a condition - additional calls are valid but
335	immediately.	803	will return immediately.
		804
		805	If an error condition has been set by calling C<< ->croak >>, then this
		806	function will call C<croak>.
		807
		808	In list context, all parameters passed to C<send> will be returned,
		809	in scalar context only the first one will be returned.
		810
		811	Note that doing a blocking wait in a callback is not supported by any
		812	event loop, that is, recursive invocation of a blocking C<< ->recv
		813	>> is not allowed, and the C<recv> call will C<croak> if such a
		814	condition is detected. This condition can be slightly loosened by using
		815	L<Coro::AnyEvent>, which allows you to do a blocking C<< ->recv >> from
		816	any thread that doesn't run the event loop itself.
336		817
337	Not all event models support a blocking wait - some die in that case	818	Not all event models support a blocking wait - some die in that case
338	(programs might want to do that to stay interactive), so I<if you are	819	(programs might want to do that to stay interactive), so I<if you are
339	using this from a module, never require a blocking wait>, but let the	820	using this from a module, never require a blocking wait>. Instead, let the
340	caller decide whether the call will block or not (for example, by coupling	821	caller decide whether the call will block or not (for example, by coupling
341	condition variables with some kind of request results and supporting	822	condition variables with some kind of request results and supporting
342	callbacks so the caller knows that getting the result will not block,	823	callbacks so the caller knows that getting the result will not block,
343	while still suppporting blocking waits if the caller so desires).	824	while still supporting blocking waits if the caller so desires).
344		825
345	Another reason I<never> to C<< ->wait >> in a module is that you cannot	826	You can ensure that C<< ->recv >> never blocks by setting a callback and
346	sensibly have two C<< ->wait >>'s in parallel, as that would require	827	only calling C<< ->recv >> from within that callback (or at a later
347	multiple interpreters or coroutines/threads, none of which C<AnyEvent>	828	time). This will work even when the event loop does not support blocking
348	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and	829	waits otherwise.
349	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
350	from different coroutines, however).
351		830
352	=item $cv->broadcast	831	=item $bool = $cv->ready
353		832
354	Flag the condition as ready - a running C<< ->wait >> and all further	833	Returns true when the condition is "true", i.e. whether C<send> or
355	calls to C<wait> will (eventually) return after this method has been	834	C<croak> have been called.
356	called. If nobody is waiting the broadcast will be remembered..	835
		836	=item $cb = $cv->cb ($cb->($cv))
		837
		838	This is a mutator function that returns the callback set and optionally
		839	replaces it before doing so.
		840
		841	The callback will be called when the condition becomes "true", i.e. when
		842	C<send> or C<croak> are called, with the only argument being the
		843	condition variable itself. If the condition is already true, the
		844	callback is called immediately when it is set. Calling C<recv> inside
		845	the callback or at any later time is guaranteed not to block.
357		846
358	=back	847	=back
359		848
360	Example:	849	=head1 SUPPORTED EVENT LOOPS/BACKENDS
361		850
362	# wait till the result is ready	851	The available backend classes are (every class has its own manpage):
363	my $result_ready = AnyEvent->condvar;
364		852
365	# do something such as adding a timer	853	=over 4
366	# or socket watcher the calls $result_ready->broadcast
367	# when the "result" is ready.
368	# in this case, we simply use a timer:
369	my $w = AnyEvent->timer (
370	after => 1,
371	cb => sub { $result_ready->broadcast },
372	);
373		854
374	# this "blocks" (while handling events) till the watcher	855	=item Backends that are autoprobed when no other event loop can be found.
375	# calls broadcast	856
376	$result_ready->wait;	857	EV is the preferred backend when no other event loop seems to be in
		858	use. If EV is not installed, then AnyEvent will fall back to its own
		859	pure-perl implementation, which is available everywhere as it comes with
		860	AnyEvent itself.
		861
		862	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		863	AnyEvent::Impl::Perl pure-perl AnyEvent::Loop, fast and portable.
		864
		865	=item Backends that are transparently being picked up when they are used.
		866
		867	These will be used if they are already loaded when the first watcher
		868	is created, in which case it is assumed that the application is using
		869	them. This means that AnyEvent will automatically pick the right backend
		870	when the main program loads an event module before anything starts to
		871	create watchers. Nothing special needs to be done by the main program.
		872
		873	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		874	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		875	AnyEvent::Impl::Tk based on Tk, very broken.
		876	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		877	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		878	AnyEvent::Impl::Irssi used when running within irssi.
		879	AnyEvent::Impl::IOAsync based on IO::Async.
		880	AnyEvent::Impl::Cocoa based on Cocoa::EventLoop.
		881	AnyEvent::Impl::FLTK based on FLTK (fltk 2 binding).
		882
		883	=item Backends with special needs.
		884
		885	Qt requires the Qt::Application to be instantiated first, but will
		886	otherwise be picked up automatically. As long as the main program
		887	instantiates the application before any AnyEvent watchers are created,
		888	everything should just work.
		889
		890	AnyEvent::Impl::Qt based on Qt.
		891
		892	=item Event loops that are indirectly supported via other backends.
		893
		894	Some event loops can be supported via other modules:
		895
		896	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		897
		898	B<WxWidgets> has no support for watching file handles. However, you can
		899	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		900	polls 20 times per second, which was considered to be too horrible to even
		901	consider for AnyEvent.
		902
		903	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		904	backend, so it can be supported through POE.
		905
		906	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		907	load L<POE> when detecting them, in the hope that POE will pick them up,
		908	in which case everything will be automatic.
		909
		910	=back
377		911
378	=head1 GLOBAL VARIABLES AND FUNCTIONS	912	=head1 GLOBAL VARIABLES AND FUNCTIONS
379		913
		914	These are not normally required to use AnyEvent, but can be useful to
		915	write AnyEvent extension modules.
		916
380	=over 4	917	=over 4
381		918
382	=item $AnyEvent::MODEL	919	=item $AnyEvent::MODEL
383		920
384	Contains C<undef> until the first watcher is being created. Then it	921	Contains C<undef> until the first watcher is being created, before the
		922	backend has been autodetected.
		923
385	contains the event model that is being used, which is the name of the	924	Afterwards it contains the event model that is being used, which is the
386	Perl class implementing the model. This class is usually one of the	925	name of the Perl class implementing the model. This class is usually one
387	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	926	of the C<AnyEvent::Impl::xxx> modules, but can be any other class in the
388	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	927	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
389		928	will be C<urxvt::anyevent>).
390	The known classes so far are:
391
392	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
393	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
394	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
395	AnyEvent::Impl::Event based on Event, second best choice.
396	AnyEvent::Impl::Glib based on Glib, third-best choice.
397	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
398	AnyEvent::Impl::Tk based on Tk, very bad choice.
399	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
400	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
401	AnyEvent::Impl::POE based on POE, not generic enough for full support.
402
403	There is no support for WxWidgets, as WxWidgets has no support for
404	watching file handles. However, you can use WxWidgets through the
405	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
406	second, which was considered to be too horrible to even consider for
407	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
408	it's adaptor.
409
410	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
411	autodetecting them.
412		929
413	=item AnyEvent::detect	930	=item AnyEvent::detect
414		931
415	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	932	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
416	if necessary. You should only call this function right before you would	933	if necessary. You should only call this function right before you would
417	have created an AnyEvent watcher anyway, that is, as late as possible at	934	have created an AnyEvent watcher anyway, that is, as late as possible at
418	runtime.	935	runtime, and not e.g. during initialisation of your module.
		936
		937	The effect of calling this function is as if a watcher had been created
		938	(specifically, actions that happen "when the first watcher is created"
		939	happen when calling detetc as well).
		940
		941	If you need to do some initialisation before AnyEvent watchers are
		942	created, use C<post_detect>.
		943
		944	=item $guard = AnyEvent::post_detect { BLOCK }
		945
		946	Arranges for the code block to be executed as soon as the event model is
		947	autodetected (or immediately if that has already happened).
		948
		949	The block will be executed I<after> the actual backend has been detected
		950	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		951	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		952	other initialisations - see the sources of L<AnyEvent::Strict> or
		953	L<AnyEvent::AIO> to see how this is used.
		954
		955	The most common usage is to create some global watchers, without forcing
		956	event module detection too early, for example, L<AnyEvent::AIO> creates
		957	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		958	avoid autodetecting the event module at load time.
		959
		960	If called in scalar or list context, then it creates and returns an object
		961	that automatically removes the callback again when it is destroyed (or
		962	C<undef> when the hook was immediately executed). See L<AnyEvent::AIO> for
		963	a case where this is useful.
		964
		965	Example: Create a watcher for the IO::AIO module and store it in
		966	C<$WATCHER>, but do so only do so after the event loop is initialised.
		967
		968	our WATCHER;
		969
		970	my $guard = AnyEvent::post_detect {
		971	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		972	};
		973
		974	# the ||= is important in case post_detect immediately runs the block,
		975	# as to not clobber the newly-created watcher. assigning both watcher and
		976	# post_detect guard to the same variable has the advantage of users being
		977	# able to just C<undef $WATCHER> if the watcher causes them grief.
		978
		979	$WATCHER ||= $guard;
		980
		981	=item @AnyEvent::post_detect
		982
		983	If there are any code references in this array (you can C<push> to it
		984	before or after loading AnyEvent), then they will be called directly
		985	after the event loop has been chosen.
		986
		987	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		988	if it is defined then the event loop has already been detected, and the
		989	array will be ignored.
		990
		991	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		992	it, as it takes care of these details.
		993
		994	This variable is mainly useful for modules that can do something useful
		995	when AnyEvent is used and thus want to know when it is initialised, but do
		996	not need to even load it by default. This array provides the means to hook
		997	into AnyEvent passively, without loading it.
		998
		999	Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used
		1000	together, you could put this into Coro (this is the actual code used by
		1001	Coro to accomplish this):
		1002
		1003	if (defined $AnyEvent::MODEL) {
		1004	# AnyEvent already initialised, so load Coro::AnyEvent
		1005	require Coro::AnyEvent;
		1006	} else {
		1007	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent
		1008	# as soon as it is
		1009	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };
		1010	}
		1011
		1012	=item AnyEvent::postpone { BLOCK }
		1013
		1014	Arranges for the block to be executed as soon as possible, but not before
		1015	the call itself returns. In practise, the block will be executed just
		1016	before the event loop polls for new events, or shortly afterwards.
		1017
		1018	This function never returns anything (to make the C<return postpone { ...
		1019	}> idiom more useful.
		1020
		1021	To understand the usefulness of this function, consider a function that
		1022	asynchronously does something for you and returns some transaction
		1023	object or guard to let you cancel the operation. For example,
		1024	C<AnyEvent::Socket::tcp_connect>:
		1025
		1026	# start a conenction attempt unless one is active
		1027	$self->{connect_guard} ||= AnyEvent::Socket::tcp_connect "www.example.net", 80, sub {
		1028	delete $self->{connect_guard};
		1029	...
		1030	};
		1031
		1032	Imagine that this function could instantly call the callback, for
		1033	example, because it detects an obvious error such as a negative port
		1034	number. Invoking the callback before the function returns causes problems
		1035	however: the callback will be called and will try to delete the guard
		1036	object. But since the function hasn't returned yet, there is nothing to
		1037	delete. When the function eventually returns it will assign the guard
		1038	object to C<< $self->{connect_guard} >>, where it will likely never be
		1039	deleted, so the program thinks it is still trying to connect.
		1040
		1041	This is where C<AnyEvent::postpone> should be used. Instead of calling the
		1042	callback directly on error:
		1043
		1044	$cb->(undef), return # signal error to callback, BAD!
		1045	if $some_error_condition;
		1046
		1047	It should use C<postpone>:
		1048
		1049	AnyEvent::postpone { $cb->(undef) }, return # signal error to callback, later
		1050	if $some_error_condition;
		1051
		1052	=item AnyEvent::log $level, $msg[, @args]
		1053
		1054	Log the given C<$msg> at the given C<$level>.
		1055
		1056	If L<AnyEvent::Log> is not loaded then this function makes a simple test
		1057	to see whether the message will be logged. If the test succeeds it will
		1058	load AnyEvent::Log and call C<AnyEvent::Log::log> - consequently, look at
		1059	the L<AnyEvent::Log> documentation for details.
		1060
		1061	If the test fails it will simply return. Right now this happens when a
		1062	numerical loglevel is used and it is larger than the level specified via
		1063	C<$ENV{PERL_ANYEVENT_VERBOSE}>.
		1064
		1065	If you want to sprinkle loads of logging calls around your code, consider
		1066	creating a logger callback with the C<AnyEvent::Log::logger> function,
		1067	which can reduce typing, codesize and can reduce the logging overhead
		1068	enourmously.
419		1069
420	=back	1070	=back
421		1071
422	=head1 WHAT TO DO IN A MODULE	1072	=head1 WHAT TO DO IN A MODULE
423		1073
…		…
427	Be careful when you create watchers in the module body - AnyEvent will	1077	Be careful when you create watchers in the module body - AnyEvent will
428	decide which event module to use as soon as the first method is called, so	1078	decide which event module to use as soon as the first method is called, so
429	by calling AnyEvent in your module body you force the user of your module	1079	by calling AnyEvent in your module body you force the user of your module
430	to load the event module first.	1080	to load the event module first.
431		1081
432	Never call C<< ->wait >> on a condition variable unless you I<know> that	1082	Never call C<< ->recv >> on a condition variable unless you I<know> that
433	the C<< ->broadcast >> method has been called on it already. This is	1083	the C<< ->send >> method has been called on it already. This is
434	because it will stall the whole program, and the whole point of using	1084	because it will stall the whole program, and the whole point of using
435	events is to stay interactive.	1085	events is to stay interactive.
436		1086
437	It is fine, however, to call C<< ->wait >> when the user of your module	1087	It is fine, however, to call C<< ->recv >> when the user of your module
438	requests it (i.e. if you create a http request object ad have a method	1088	requests it (i.e. if you create a http request object ad have a method
439	called C<results> that returns the results, it should call C<< ->wait >>	1089	called C<results> that returns the results, it may call C<< ->recv >>
440	freely, as the user of your module knows what she is doing. always).	1090	freely, as the user of your module knows what she is doing. Always).
441		1091
442	=head1 WHAT TO DO IN THE MAIN PROGRAM	1092	=head1 WHAT TO DO IN THE MAIN PROGRAM
443		1093
444	There will always be a single main program - the only place that should	1094	There will always be a single main program - the only place that should
445	dictate which event model to use.	1095	dictate which event model to use.
446		1096
447	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	1097	If the program is not event-based, it need not do anything special, even
448	do anything special (it does not need to be event-based) and let AnyEvent	1098	when it depends on a module that uses an AnyEvent. If the program itself
449	decide which implementation to chose if some module relies on it.	1099	uses AnyEvent, but does not care which event loop is used, all it needs
		1100	to do is C<use AnyEvent>. In either case, AnyEvent will choose the best
		1101	available loop implementation.
450		1102
451	If the main program relies on a specific event model. For example, in	1103	If the main program relies on a specific event model - for example, in
452	Gtk2 programs you have to rely on the Glib module. You should load the	1104	Gtk2 programs you have to rely on the Glib module - you should load the
453	event module before loading AnyEvent or any module that uses it: generally	1105	event module before loading AnyEvent or any module that uses it: generally
454	speaking, you should load it as early as possible. The reason is that	1106	speaking, you should load it as early as possible. The reason is that
455	modules might create watchers when they are loaded, and AnyEvent will	1107	modules might create watchers when they are loaded, and AnyEvent will
456	decide on the event model to use as soon as it creates watchers, and it	1108	decide on the event model to use as soon as it creates watchers, and it
457	might chose the wrong one unless you load the correct one yourself.	1109	might choose the wrong one unless you load the correct one yourself.
458		1110
459	You can chose to use a rather inefficient pure-perl implementation by	1111	You can chose to use a pure-perl implementation by loading the
460	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	1112	C<AnyEvent::Loop> module, which gives you similar behaviour
461	behaviour everywhere, but letting AnyEvent chose is generally better.	1113	everywhere, but letting AnyEvent chose the model is generally better.
		1114
		1115	=head2 MAINLOOP EMULATION
		1116
		1117	Sometimes (often for short test scripts, or even standalone programs who
		1118	only want to use AnyEvent), you do not want to run a specific event loop.
		1119
		1120	In that case, you can use a condition variable like this:
		1121
		1122	AnyEvent->condvar->recv;
		1123
		1124	This has the effect of entering the event loop and looping forever.
		1125
		1126	Note that usually your program has some exit condition, in which case
		1127	it is better to use the "traditional" approach of storing a condition
		1128	variable somewhere, waiting for it, and sending it when the program should
		1129	exit cleanly.
		1130
		1131
		1132	=head1 OTHER MODULES
		1133
		1134	The following is a non-exhaustive list of additional modules that use
		1135	AnyEvent as a client and can therefore be mixed easily with other
		1136	AnyEvent modules and other event loops in the same program. Some of the
		1137	modules come as part of AnyEvent, the others are available via CPAN (see
		1138	L<http://search.cpan.org/search?m=module&q=anyevent%3A%3A*> for
		1139	a longer non-exhaustive list), and the list is heavily biased towards
		1140	modules of the AnyEvent author himself :)
		1141
		1142	=over 4
		1143
		1144	=item L<AnyEvent::Util>
		1145
		1146	Contains various utility functions that replace often-used blocking
		1147	functions such as C<inet_aton> with event/callback-based versions.
		1148
		1149	=item L<AnyEvent::Socket>
		1150
		1151	Provides various utility functions for (internet protocol) sockets,
		1152	addresses and name resolution. Also functions to create non-blocking tcp
		1153	connections or tcp servers, with IPv6 and SRV record support and more.
		1154
		1155	=item L<AnyEvent::Handle>
		1156
		1157	Provide read and write buffers, manages watchers for reads and writes,
		1158	supports raw and formatted I/O, I/O queued and fully transparent and
		1159	non-blocking SSL/TLS (via L<AnyEvent::TLS>).
		1160
		1161	=item L<AnyEvent::DNS>
		1162
		1163	Provides rich asynchronous DNS resolver capabilities.
		1164
		1165	=item L<AnyEvent::HTTP>, L<AnyEvent::IRC>, L<AnyEvent::XMPP>, L<AnyEvent::GPSD>, L<AnyEvent::IGS>, L<AnyEvent::FCP>
		1166
		1167	Implement event-based interfaces to the protocols of the same name (for
		1168	the curious, IGS is the International Go Server and FCP is the Freenet
		1169	Client Protocol).
		1170
		1171	=item L<AnyEvent::AIO>
		1172
		1173	Truly asynchronous (as opposed to non-blocking) I/O, should be in the
		1174	toolbox of every event programmer. AnyEvent::AIO transparently fuses
		1175	L<IO::AIO> and AnyEvent together, giving AnyEvent access to event-based
		1176	file I/O, and much more.
		1177
		1178	=item L<AnyEvent::Filesys::Notify>
		1179
		1180	AnyEvent is good for non-blocking stuff, but it can't detect file or
		1181	path changes (e.g. "watch this directory for new files", "watch this
		1182	file for changes"). The L<AnyEvent::Filesys::Notify> module promises to
		1183	do just that in a portbale fashion, supporting inotify on GNU/Linux and
		1184	some weird, without doubt broken, stuff on OS X to monitor files. It can
		1185	fall back to blocking scans at regular intervals transparently on other
		1186	platforms, so it's about as portable as it gets.
		1187
		1188	(I haven't used it myself, but I haven't heard anybody complaining about
		1189	it yet).
		1190
		1191	=item L<AnyEvent::DBI>
		1192
		1193	Executes L<DBI> requests asynchronously in a proxy process for you,
		1194	notifying you in an event-based way when the operation is finished.
		1195
		1196	=item L<AnyEvent::HTTPD>
		1197
		1198	A simple embedded webserver.
		1199
		1200	=item L<AnyEvent::FastPing>
		1201
		1202	The fastest ping in the west.
		1203
		1204	=item L<Coro>
		1205
		1206	Has special support for AnyEvent via L<Coro::AnyEvent>, which allows you
		1207	to simply invert the flow control - don't call us, we will call you:
		1208
		1209	async {
		1210	Coro::AnyEvent::sleep 5; # creates a 5s timer and waits for it
		1211	print "5 seconds later!\n";
		1212
		1213	Coro::AnyEvent::readable *STDIN; # uses an I/O watcher
		1214	my $line = <STDIN>; # works for ttys
		1215
		1216	AnyEvent::HTTP::http_get "url", Coro::rouse_cb;
		1217	my ($body, $hdr) = Coro::rouse_wait;
		1218	};
		1219
		1220	=back
462		1221
463	=cut	1222	=cut
464		1223
465	package AnyEvent;	1224	package AnyEvent;
466		1225
467	no warnings;	1226	# basically a tuned-down version of common::sense
468	use strict;	1227	sub common_sense {
		1228	# from common:.sense 3.4
		1229	${^WARNING_BITS} ^= ${^WARNING_BITS} ^ "\x3c\x3f\x33\x00\x0f\xf0\x0f\xc0\xf0\xfc\x33\x00";
		1230	# use strict vars subs - NO UTF-8, as Util.pm doesn't like this atm. (uts46data.pl)
		1231	$^H |= 0x00000600;
		1232	}
469		1233
		1234	BEGIN { AnyEvent::common_sense }
		1235
470	use Carp;	1236	use Carp ();
471		1237
472	our $VERSION = '3.3';	1238	our $VERSION = '6.02';
473	our $MODEL;	1239	our $MODEL;
474
475	our $AUTOLOAD;
476	our @ISA;	1240	our @ISA;
477
478	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
479
480	our @REGISTRY;	1241	our @REGISTRY;
		1242	our $VERBOSE;
		1243	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		1244	our $MAX_SIGNAL_LATENCY = $ENV{PERL_ANYEVENT_MAX_SIGNAL_LATENCY} || 10; # executes after the BEGIN block below (tainting!)
481		1245
		1246	BEGIN {
		1247	require "AnyEvent/constants.pl";
		1248
		1249	eval "sub TAINT (){" . (${^TAINT}*1) . "}";
		1250
		1251	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1252	if ${^TAINT};
		1253
		1254	$ENV{"PERL_ANYEVENT_$_"} = $ENV{"AE_$_"}
		1255	for grep s/^AE_// && !exists $ENV{"PERL_ANYEVENT_$_"}, keys %ENV;
		1256
		1257	@ENV{grep /^PERL_ANYEVENT_/, keys %ENV} = ()
		1258	if ${^TAINT};
		1259
		1260	# $ENV{PERL_ANYEVENT_xxx} now valid
		1261
		1262	$VERBOSE = length $ENV{PERL_ANYEVENT_VERBOSE} ? $ENV{PERL_ANYEVENT_VERBOSE}*1 : 4;
		1263
		1264	my $idx;
		1265	$PROTOCOL{$_} = ++$idx
		1266	for reverse split /\s*,\s*/,
		1267	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		1268	}
		1269
		1270	our @post_detect;
		1271
		1272	sub post_detect(&) {
		1273	my ($cb) = @_;
		1274
		1275	push @post_detect, $cb;
		1276
		1277	defined wantarray
		1278	? bless \$cb, "AnyEvent::Util::postdetect"
		1279	: ()
		1280	}
		1281
		1282	sub AnyEvent::Util::postdetect::DESTROY {
		1283	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		1284	}
		1285
		1286	our $POSTPONE_W;
		1287	our @POSTPONE;
		1288
		1289	sub _postpone_exec {
		1290	undef $POSTPONE_W;
		1291
		1292	&{ shift @POSTPONE }
		1293	while @POSTPONE;
		1294	}
		1295
		1296	sub postpone(&) {
		1297	push @POSTPONE, shift;
		1298
		1299	$POSTPONE_W ||= AE::timer (0, 0, \&_postpone_exec);
		1300
		1301	()
		1302	}
		1303
		1304	sub log($$;@) {
		1305	# only load the big bloated module when we actually are about to log something
		1306	if ($_[0] <= ($VERBOSE || 1)) { # also catches non-numeric levels(!) and fatal
		1307	local ($!, $@);
		1308	require AnyEvent::Log; # among other things, sets $VERBOSE to 9
		1309	# AnyEvent::Log overwrites this function
		1310	goto &log;
		1311	}
		1312
		1313	0 # not logged
		1314	}
		1315
		1316	sub _logger($;$) {
		1317	my ($level, $renabled) = @_;
		1318
		1319	$$renabled = $level <= $VERBOSE;
		1320
		1321	my $logger = [(caller)[0], $level, $renabled];
		1322
		1323	$AnyEvent::Log::LOGGER{$logger+0} = $logger;
		1324
		1325	# return unless defined wantarray;
		1326	#
		1327	# require AnyEvent::Util;
		1328	# my $guard = AnyEvent::Util::guard (sub {
		1329	# # "clean up"
		1330	# delete $LOGGER{$logger+0};
		1331	# });
		1332	#
		1333	# sub {
		1334	# return 0 unless $$renabled;
		1335	#
		1336	# $guard if 0; # keep guard alive, but don't cause runtime overhead
		1337	# require AnyEvent::Log unless $AnyEvent::Log::VERSION;
		1338	# package AnyEvent::Log;
		1339	# _log ($logger->[0], $level, @_) # logger->[0] has been converted at load time
		1340	# }
		1341	}
		1342
		1343	if (length $ENV{PERL_ANYEVENT_LOG}) {
		1344	require AnyEvent::Log; # AnyEvent::Log does the thing for us
		1345	}
		1346
482	my @models = (	1347	our @models = (
483	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
484	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
485	[EV:: => AnyEvent::Impl::EV::],	1348	[EV:: => AnyEvent::Impl::EV::],
		1349	[AnyEvent::Loop:: => AnyEvent::Impl::Perl::],
		1350	# everything below here will not (normally) be autoprobed
		1351	# as the pure perl backend should work everywhere
		1352	# and is usually faster
		1353	[Irssi:: => AnyEvent::Impl::Irssi::], # Irssi has a bogus "Event" package, so msut be near the top
486	[Event:: => AnyEvent::Impl::Event::],	1354	[Event:: => AnyEvent::Impl::Event::], # slow, stable
487	[Glib:: => AnyEvent::Impl::Glib::],	1355	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers
		1356	# everything below here should not be autoloaded
		1357	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
488	[Tk:: => AnyEvent::Impl::Tk::],	1358	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		1359	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		1360	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
489	[Wx:: => AnyEvent::Impl::POE::],	1361	[Wx:: => AnyEvent::Impl::POE::],
490	[Prima:: => AnyEvent::Impl::POE::],	1362	[Prima:: => AnyEvent::Impl::POE::],
491	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1363	[IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # a bitch to autodetect
492	# everything below here will not be autoprobed as the pureperl backend should work everywhere	1364	[Cocoa::EventLoop:: => AnyEvent::Impl::Cocoa::],
493	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy	1365	[FLTK:: => AnyEvent::Impl::FLTK::],
494	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
495	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
496	);	1366	);
497		1367
498	our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);	1368	our @isa_hook;
		1369
		1370	sub _isa_set {
		1371	my @pkg = ("AnyEvent", (map $_->[0], grep defined, @isa_hook), $MODEL);
		1372
		1373	@{"$pkg[$_-1]::ISA"} = $pkg[$_]
		1374	for 1 .. $#pkg;
		1375
		1376	grep $_ && $_->[1], @isa_hook
		1377	and AE::_reset ();
		1378	}
		1379
		1380	# used for hooking AnyEvent::Strict and AnyEvent::Debug::Wrap into the class hierarchy
		1381	sub _isa_hook($$;$) {
		1382	my ($i, $pkg, $reset_ae) = @_;
		1383
		1384	$isa_hook[$i] = $pkg ? [$pkg, $reset_ae] : undef;
		1385
		1386	_isa_set;
		1387	}
		1388
		1389	# all autoloaded methods reserve the complete glob, not just the method slot.
		1390	# due to bugs in perls method cache implementation.
		1391	our @methods = qw(io timer time now now_update signal child idle condvar);
499		1392
500	sub detect() {	1393	sub detect() {
		1394	return $MODEL if $MODEL; # some programs keep references to detect
		1395
		1396	# IO::Async::Loop::AnyEvent is extremely evil, refuse to work with it
		1397	# the author knows about the problems and what it does to AnyEvent as a whole
		1398	# (and the ability of others to use AnyEvent), but simply wants to abuse AnyEvent
		1399	# anyway.
		1400	AnyEvent::log fatal => "AnyEvent: IO::Async::Loop::AnyEvent detected - this module is broken by design,\n"
		1401	. "abuses internals and breaks AnyEvent, will not continue."
		1402	if exists $INC{"IO/Async/Loop/AnyEvent.pm"};
		1403
		1404	local $!; # for good measure
		1405	local $SIG{__DIE__}; # we use eval
		1406
		1407	# free some memory
		1408	*detect = sub () { $MODEL };
		1409	# undef &func doesn't correctly update the method cache. grmbl.
		1410	# so we delete the whole glob. grmbl.
		1411	# otoh, perl doesn't let me undef an active usb, but it lets me free
		1412	# a glob with an active sub. hrm. i hope it works, but perl is
		1413	# usually buggy in this department. sigh.
		1414	delete @{"AnyEvent::"}{@methods};
		1415	undef @methods;
		1416
		1417	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z0-9:]+)$/) {
		1418	my $model = $1;
		1419	$model = "AnyEvent::Impl::$model" unless $model =~ s/::$//;
		1420	if (eval "require $model") {
		1421	AnyEvent::log 7 => "loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.";
		1422	$MODEL = $model;
		1423	} else {
		1424	AnyEvent::log 4 => "unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@";
		1425	}
		1426	}
		1427
		1428	# check for already loaded models
501	unless ($MODEL) {	1429	unless ($MODEL) {
502	no strict 'refs';	1430	for (@REGISTRY, @models) {
503		1431	my ($package, $model) = @$_;
504	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	1432	if (${"$package\::VERSION"} > 0) {
505	my $model = "AnyEvent::Impl::$1";
506	if (eval "require $model") {	1433	if (eval "require $model") {
		1434	AnyEvent::log 7 => "autodetected model '$model', using it.";
507	$MODEL = $model;	1435	$MODEL = $model;
508	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	1436	last;
509	} else {	1437	}
510	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;
511	}	1438	}
512	}	1439	}
513		1440
514	# check for already loaded models
515	unless ($MODEL) {	1441	unless ($MODEL) {
		1442	# try to autoload a model
516	for (@REGISTRY, @models) {	1443	for (@REGISTRY, @models) {
517	my ($package, $model) = @$_;	1444	my ($package, $model) = @$_;
		1445	if (
		1446	eval "require $package"
518	if (${"$package\::VERSION"} > 0) {	1447	and ${"$package\::VERSION"} > 0
519	if (eval "require $model") {	1448	and eval "require $model"
		1449	) {
		1450	AnyEvent::log 7 => "autoloaded model '$model', using it.";
520	$MODEL = $model;	1451	$MODEL = $model;
521	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;
522	last;	1452	last;
523	}
524	}	1453	}
525	}	1454	}
526		1455
527	unless ($MODEL) {	1456	$MODEL
528	# try to load a model	1457	or AnyEvent::log fatal => "AnyEvent: backend autodetection failed - did you properly install AnyEvent?";
		1458	}
		1459	}
529		1460
530	for (@REGISTRY, @models) {	1461	# free memory only needed for probing
531	my ($package, $model) = @$_;	1462	undef @models;
532	if (eval "require $package"	1463	undef @REGISTRY;
533	and ${"$package\::VERSION"} > 0	1464
534	and eval "require $model") {	1465	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
535	$MODEL = $model;	1466
536	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;	1467	# now nuke some methods that are overridden by the backend.
		1468	# SUPER usage is not allowed in these.
		1469	for (qw(time signal child idle)) {
		1470	undef &{"AnyEvent::Base::$_"}
		1471	if defined &{"$MODEL\::$_"};
		1472	}
		1473
		1474	_isa_set;
		1475
		1476	# we're officially open!
		1477
		1478	if ($ENV{PERL_ANYEVENT_STRICT}) {
		1479	require AnyEvent::Strict;
		1480	}
		1481
		1482	if ($ENV{PERL_ANYEVENT_DEBUG_WRAP}) {
		1483	require AnyEvent::Debug;
		1484	AnyEvent::Debug::wrap ($ENV{PERL_ANYEVENT_DEBUG_WRAP});
		1485	}
		1486
		1487	if (length $ENV{PERL_ANYEVENT_DEBUG_SHELL}) {
		1488	require AnyEvent::Socket;
		1489	require AnyEvent::Debug;
		1490
		1491	my $shell = $ENV{PERL_ANYEVENT_DEBUG_SHELL};
		1492	$shell =~ s/\$\$/$$/g;
		1493
		1494	my ($host, $service) = AnyEvent::Socket::parse_hostport ($shell);
		1495	$AnyEvent::Debug::SHELL = AnyEvent::Debug::shell ($host, $service);
		1496	}
		1497
		1498	# now the anyevent environment is set up as the user told us to, so
		1499	# call the actual user code - post detects
		1500
		1501	(shift @post_detect)->() while @post_detect;
		1502	undef @post_detect;
		1503
		1504	*post_detect = sub(&) {
		1505	shift->();
		1506
		1507	undef
		1508	};
		1509
		1510	$MODEL
		1511	}
		1512
		1513	for my $name (@methods) {
		1514	*$name = sub {
		1515	detect;
		1516	# we use goto because
		1517	# a) it makes the thunk more transparent
		1518	# b) it allows us to delete the thunk later
		1519	goto &{ UNIVERSAL::can AnyEvent => "SUPER::$name" }
		1520	};
		1521	}
		1522
		1523	# utility function to dup a filehandle. this is used by many backends
		1524	# to support binding more than one watcher per filehandle (they usually
		1525	# allow only one watcher per fd, so we dup it to get a different one).
		1526	sub _dupfh($$;$$) {
		1527	my ($poll, $fh, $r, $w) = @_;
		1528
		1529	# cygwin requires the fh mode to be matching, unix doesn't
		1530	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1531
		1532	open my $fh2, $mode, $fh
		1533	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1534
		1535	# we assume CLOEXEC is already set by perl in all important cases
		1536
		1537	($fh2, $rw)
		1538	}
		1539
		1540	=head1 SIMPLIFIED AE API
		1541
		1542	Starting with version 5.0, AnyEvent officially supports a second, much
		1543	simpler, API that is designed to reduce the calling, typing and memory
		1544	overhead by using function call syntax and a fixed number of parameters.
		1545
		1546	See the L<AE> manpage for details.
		1547
		1548	=cut
		1549
		1550	package AE;
		1551
		1552	our $VERSION = $AnyEvent::VERSION;
		1553
		1554	sub _reset() {
		1555	eval q{
		1556	# fall back to the main API by default - backends and AnyEvent::Base
		1557	# implementations can overwrite these.
		1558
		1559	sub io($$$) {
		1560	AnyEvent->io (fh => $_[0], poll => $_[1] ? "w" : "r", cb => $_[2])
		1561	}
		1562
		1563	sub timer($$$) {
		1564	AnyEvent->timer (after => $_[0], interval => $_[1], cb => $_[2])
		1565	}
		1566
		1567	sub signal($$) {
		1568	AnyEvent->signal (signal => $_[0], cb => $_[1])
		1569	}
		1570
		1571	sub child($$) {
		1572	AnyEvent->child (pid => $_[0], cb => $_[1])
		1573	}
		1574
		1575	sub idle($) {
		1576	AnyEvent->idle (cb => $_[0]);
		1577	}
		1578
		1579	sub cv(;&) {
		1580	AnyEvent->condvar (@_ ? (cb => $_[0]) : ())
		1581	}
		1582
		1583	sub now() {
		1584	AnyEvent->now
		1585	}
		1586
		1587	sub now_update() {
		1588	AnyEvent->now_update
		1589	}
		1590
		1591	sub time() {
		1592	AnyEvent->time
		1593	}
		1594
		1595	*postpone = \&AnyEvent::postpone;
		1596	*log = \&AnyEvent::log;
		1597	};
		1598	die if $@;
		1599	}
		1600
		1601	BEGIN { _reset }
		1602
		1603	package AnyEvent::Base;
		1604
		1605	# default implementations for many methods
		1606
		1607	sub time {
		1608	eval q{ # poor man's autoloading {}
		1609	# probe for availability of Time::HiRes
		1610	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1611	*time = sub { Time::HiRes::time () };
		1612	*AE::time = \& Time::HiRes::time ;
		1613	*now = \&time;
		1614	AnyEvent::log 8 => "AnyEvent: using Time::HiRes for sub-second timing accuracy.";
		1615	# if (eval "use POSIX (); (POSIX::times())...
		1616	} else {
		1617	*time = sub { CORE::time };
		1618	*AE::time = sub (){ CORE::time };
		1619	*now = \&time;
		1620	AnyEvent::log 3 => "using built-in time(), WARNING, no sub-second resolution!";
		1621	}
		1622	};
		1623	die if $@;
		1624
		1625	&time
		1626	}
		1627
		1628	*now = \&time;
		1629	sub now_update { }
		1630
		1631	sub _poll {
		1632	Carp::croak "$AnyEvent::MODEL does not support blocking waits. Caught";
		1633	}
		1634
		1635	# default implementation for ->condvar
		1636	# in fact, the default should not be overwritten
		1637
		1638	sub condvar {
		1639	eval q{ # poor man's autoloading {}
		1640	*condvar = sub {
		1641	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
		1642	};
		1643
		1644	*AE::cv = sub (;&) {
		1645	bless { @_ ? (_ae_cb => shift) : () }, "AnyEvent::CondVar"
		1646	};
		1647	};
		1648	die if $@;
		1649
		1650	&condvar
		1651	}
		1652
		1653	# default implementation for ->signal
		1654
		1655	our $HAVE_ASYNC_INTERRUPT;
		1656
		1657	sub _have_async_interrupt() {
		1658	$HAVE_ASYNC_INTERRUPT = 1*(!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT}
		1659	&& eval "use Async::Interrupt 1.02 (); 1")
		1660	unless defined $HAVE_ASYNC_INTERRUPT;
		1661
		1662	$HAVE_ASYNC_INTERRUPT
		1663	}
		1664
		1665	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1666	our (%SIG_ASY, %SIG_ASY_W);
		1667	our ($SIG_COUNT, $SIG_TW);
		1668
		1669	# install a dummy wakeup watcher to reduce signal catching latency
		1670	# used by Impls
		1671	sub _sig_add() {
		1672	unless ($SIG_COUNT++) {
		1673	# try to align timer on a full-second boundary, if possible
		1674	my $NOW = AE::now;
		1675
		1676	$SIG_TW = AE::timer
		1677	$MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1678	$MAX_SIGNAL_LATENCY,
		1679	sub { } # just for the PERL_ASYNC_CHECK
		1680	;
		1681	}
		1682	}
		1683
		1684	sub _sig_del {
		1685	undef $SIG_TW
		1686	unless --$SIG_COUNT;
		1687	}
		1688
		1689	our $_sig_name_init; $_sig_name_init = sub {
		1690	eval q{ # poor man's autoloading {}
		1691	undef $_sig_name_init;
		1692
		1693	if (_have_async_interrupt) {
		1694	*sig2num = \&Async::Interrupt::sig2num;
		1695	*sig2name = \&Async::Interrupt::sig2name;
		1696	} else {
		1697	require Config;
		1698
		1699	my %signame2num;
		1700	@signame2num{ split ' ', $Config::Config{sig_name} }
		1701	= split ' ', $Config::Config{sig_num};
		1702
		1703	my @signum2name;
		1704	@signum2name[values %signame2num] = keys %signame2num;
		1705
		1706	*sig2num = sub($) {
		1707	$_[0] > 0 ? shift : $signame2num{+shift}
		1708	};
		1709	*sig2name = sub ($) {
		1710	$_[0] > 0 ? $signum2name[+shift] : shift
		1711	};
		1712	}
		1713	};
		1714	die if $@;
		1715	};
		1716
		1717	sub sig2num ($) { &$_sig_name_init; &sig2num }
		1718	sub sig2name($) { &$_sig_name_init; &sig2name }
		1719
		1720	sub signal {
		1721	eval q{ # poor man's autoloading {}
		1722	# probe for availability of Async::Interrupt
		1723	if (_have_async_interrupt) {
		1724	AnyEvent::log 8 => "using Async::Interrupt for race-free signal handling.";
		1725
		1726	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1727	$SIG_IO = AE::io $SIGPIPE_R->fileno, 0, \&_signal_exec;
		1728
		1729	} else {
		1730	AnyEvent::log 8 => "using emulated perl signal handling with latency timer.";
		1731
		1732	if (AnyEvent::WIN32) {
		1733	require AnyEvent::Util;
		1734
		1735	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1736	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R, 1) if $SIGPIPE_R;
		1737	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W, 1) if $SIGPIPE_W; # just in case
		1738	} else {
		1739	pipe $SIGPIPE_R, $SIGPIPE_W;
		1740	fcntl $SIGPIPE_R, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_R;
		1741	fcntl $SIGPIPE_W, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_W; # just in case
		1742
		1743	# not strictly required, as $^F is normally 2, but let's make sure...
		1744	fcntl $SIGPIPE_R, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1745	fcntl $SIGPIPE_W, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1746	}
		1747
		1748	$SIGPIPE_R
		1749	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1750
		1751	$SIG_IO = AE::io $SIGPIPE_R, 0, \&_signal_exec;
		1752	}
		1753
		1754	*signal = $HAVE_ASYNC_INTERRUPT
		1755	? sub {
		1756	my (undef, %arg) = @_;
		1757
		1758	# async::interrupt
		1759	my $signal = sig2num $arg{signal};
		1760	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1761
		1762	$SIG_ASY{$signal} ||= new Async::Interrupt
		1763	cb => sub { undef $SIG_EV{$signal} },
		1764	signal => $signal,
		1765	pipe => [$SIGPIPE_R->filenos],
		1766	pipe_autodrain => 0,
		1767	;
		1768
		1769	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1770	}
		1771	: sub {
		1772	my (undef, %arg) = @_;
		1773
		1774	# pure perl
		1775	my $signal = sig2name $arg{signal};
		1776	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1777
		1778	$SIG{$signal} ||= sub {
537	last;	1779	local $!;
		1780	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1781	undef $SIG_EV{$signal};
538	}	1782	};
		1783
		1784	# can't do signal processing without introducing races in pure perl,
		1785	# so limit the signal latency.
		1786	_sig_add;
		1787
		1788	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1789	}
		1790	;
		1791
		1792	*AnyEvent::Base::signal::DESTROY = sub {
		1793	my ($signal, $cb) = @{$_[0]};
		1794
		1795	_sig_del;
		1796
		1797	delete $SIG_CB{$signal}{$cb};
		1798
		1799	$HAVE_ASYNC_INTERRUPT
		1800	? delete $SIG_ASY{$signal}
		1801	: # delete doesn't work with older perls - they then
		1802	# print weird messages, or just unconditionally exit
		1803	# instead of getting the default action.
		1804	undef $SIG{$signal}
		1805	unless keys %{ $SIG_CB{$signal} };
		1806	};
		1807
		1808	*_signal_exec = sub {
		1809	$HAVE_ASYNC_INTERRUPT
		1810	? $SIGPIPE_R->drain
		1811	: sysread $SIGPIPE_R, (my $dummy), 9;
		1812
		1813	while (%SIG_EV) {
		1814	for (keys %SIG_EV) {
		1815	delete $SIG_EV{$_};
		1816	&$_ for values %{ $SIG_CB{$_} || {} };
539	}	1817	}
540
541	$MODEL
542	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.";
543	}	1818	}
544	}	1819	};
545
546	unshift @ISA, $MODEL;
547	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
548	}
549
550	$MODEL
551	}
552
553	sub AUTOLOAD {
554	(my $func = $AUTOLOAD) =~ s/.*://;
555
556	$method{$func}
557	or croak "$func: not a valid method for AnyEvent objects";
558
559	detect unless $MODEL;
560
561	my $class = shift;
562	$class->$func (@_);
563	}
564
565	package AnyEvent::Base;
566
567	# default implementation for ->condvar, ->wait, ->broadcast
568
569	sub condvar {
570	bless \my $flag, "AnyEvent::Base::CondVar"
571	}
572
573	sub AnyEvent::Base::CondVar::broadcast {
574	${$_[0]}++;
575	}
576
577	sub AnyEvent::Base::CondVar::wait {
578	AnyEvent->one_event while !${$_[0]};
579	}
580
581	# default implementation for ->signal
582
583	our %SIG_CB;
584
585	sub signal {
586	my (undef, %arg) = @_;
587
588	my $signal = uc $arg{signal}
589	or Carp::croak "required option 'signal' is missing";
590
591	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
592	$SIG{$signal} ||= sub {
593	$_->() for values %{ $SIG_CB{$signal} || {} };
594	};	1820	};
		1821	die if $@;
595		1822
596	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1823	&signal
597	}
598
599	sub AnyEvent::Base::Signal::DESTROY {
600	my ($signal, $cb) = @{$_[0]};
601
602	delete $SIG_CB{$signal}{$cb};
603
604	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };
605	}	1824	}
606		1825
607	# default implementation for ->child	1826	# default implementation for ->child
608		1827
609	our %PID_CB;	1828	our %PID_CB;
610	our $CHLD_W;	1829	our $CHLD_W;
611	our $CHLD_DELAY_W;	1830	our $CHLD_DELAY_W;
612	our $PID_IDLE;
613	our $WNOHANG;
614		1831
615	sub _child_wait {	1832	# used by many Impl's
616	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1833	sub _emit_childstatus($$) {
		1834	my (undef, $rpid, $rstatus) = @_;
		1835
		1836	$_->($rpid, $rstatus)
617	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1837	for values %{ $PID_CB{$rpid} || {} },
618	(values %{ $PID_CB{0} || {} });	1838	values %{ $PID_CB{0} || {} };
		1839	}
		1840
		1841	sub child {
		1842	eval q{ # poor man's autoloading {}
		1843	*_sigchld = sub {
		1844	my $pid;
		1845
		1846	AnyEvent->_emit_childstatus ($pid, $?)
		1847	while ($pid = waitpid -1, WNOHANG) > 0;
		1848	};
		1849
		1850	*child = sub {
		1851	my (undef, %arg) = @_;
		1852
		1853	my $pid = $arg{pid};
		1854	my $cb = $arg{cb};
		1855
		1856	$PID_CB{$pid}{$cb+0} = $cb;
		1857
		1858	unless ($CHLD_W) {
		1859	$CHLD_W = AE::signal CHLD => \&_sigchld;
		1860	# child could be a zombie already, so make at least one round
		1861	&_sigchld;
		1862	}
		1863
		1864	bless [$pid, $cb+0], "AnyEvent::Base::child"
		1865	};
		1866
		1867	*AnyEvent::Base::child::DESTROY = sub {
		1868	my ($pid, $icb) = @{$_[0]};
		1869
		1870	delete $PID_CB{$pid}{$icb};
		1871	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
		1872
		1873	undef $CHLD_W unless keys %PID_CB;
		1874	};
		1875	};
		1876	die if $@;
		1877
		1878	&child
		1879	}
		1880
		1881	# idle emulation is done by simply using a timer, regardless
		1882	# of whether the process is idle or not, and not letting
		1883	# the callback use more than 50% of the time.
		1884	sub idle {
		1885	eval q{ # poor man's autoloading {}
		1886	*idle = sub {
		1887	my (undef, %arg) = @_;
		1888
		1889	my ($cb, $w, $rcb) = $arg{cb};
		1890
		1891	$rcb = sub {
		1892	if ($cb) {
		1893	$w = AE::time;
		1894	&$cb;
		1895	$w = AE::time - $w;
		1896
		1897	# never use more then 50% of the time for the idle watcher,
		1898	# within some limits
		1899	$w = 0.0001 if $w < 0.0001;
		1900	$w = 5 if $w > 5;
		1901
		1902	$w = AE::timer $w, 0, $rcb;
		1903	} else {
		1904	# clean up...
		1905	undef $w;
		1906	undef $rcb;
		1907	}
		1908	};
		1909
		1910	$w = AE::timer 0.05, 0, $rcb;
		1911
		1912	bless \\$cb, "AnyEvent::Base::idle"
		1913	};
		1914
		1915	*AnyEvent::Base::idle::DESTROY = sub {
		1916	undef $${$_[0]};
		1917	};
		1918	};
		1919	die if $@;
		1920
		1921	&idle
		1922	}
		1923
		1924	package AnyEvent::CondVar;
		1925
		1926	our @ISA = AnyEvent::CondVar::Base::;
		1927
		1928	# only to be used for subclassing
		1929	sub new {
		1930	my $class = shift;
		1931	bless AnyEvent->condvar (@_), $class
		1932	}
		1933
		1934	package AnyEvent::CondVar::Base;
		1935
		1936	#use overload
		1937	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1938	# fallback => 1;
		1939
		1940	# save 300+ kilobytes by dirtily hardcoding overloading
		1941	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1942	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1943	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1944	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1945
		1946	our $WAITING;
		1947
		1948	sub _send {
		1949	# nop
		1950	}
		1951
		1952	sub _wait {
		1953	AnyEvent->_poll until $_[0]{_ae_sent};
		1954	}
		1955
		1956	sub send {
		1957	my $cv = shift;
		1958	$cv->{_ae_sent} = [@_];
		1959	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1960	$cv->_send;
		1961	}
		1962
		1963	sub croak {
		1964	$_[0]{_ae_croak} = $_[1];
		1965	$_[0]->send;
		1966	}
		1967
		1968	sub ready {
		1969	$_[0]{_ae_sent}
		1970	}
		1971
		1972	sub recv {
		1973	unless ($_[0]{_ae_sent}) {
		1974	$WAITING
		1975	and Carp::croak "AnyEvent::CondVar: recursive blocking wait attempted";
		1976
		1977	local $WAITING = 1;
		1978	$_[0]->_wait;
619	}	1979	}
620		1980
621	undef $PID_IDLE;	1981	$_[0]{_ae_croak}
622	}	1982	and Carp::croak $_[0]{_ae_croak};
623		1983
624	sub _sigchld {	1984	wantarray
625	# make sure we deliver these changes "synchronous" with the event loop.	1985	? @{ $_[0]{_ae_sent} }
626	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {	1986	: $_[0]{_ae_sent}[0]
627	undef $CHLD_DELAY_W;
628	&_child_wait;
629	});
630	}	1987	}
631		1988
632	sub child {	1989	sub cb {
633	my (undef, %arg) = @_;	1990	my $cv = shift;
634		1991
635	defined (my $pid = $arg{pid} + 0)	1992	@_
636	or Carp::croak "required option 'pid' is missing";	1993	and $cv->{_ae_cb} = shift
		1994	and $cv->{_ae_sent}
		1995	and (delete $cv->{_ae_cb})->($cv);
637		1996
638	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1997	$cv->{_ae_cb}
639
640	unless ($WNOHANG) {
641	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;
642	}
643
644	unless ($CHLD_W) {
645	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
646	# child could be a zombie already, so make at least one round
647	&_sigchld;
648	}
649
650	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"
651	}	1998	}
652		1999
653	sub AnyEvent::Base::Child::DESTROY {	2000	sub begin {
654	my ($pid, $cb) = @{$_[0]};	2001	++$_[0]{_ae_counter};
655		2002	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
656	delete $PID_CB{$pid}{$cb};
657	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
658
659	undef $CHLD_W unless keys %PID_CB;
660	}	2003	}
		2004
		2005	sub end {
		2006	return if --$_[0]{_ae_counter};
		2007	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		2008	}
		2009
		2010	# undocumented/compatibility with pre-3.4
		2011	*broadcast = \&send;
		2012	*wait = \&recv;
		2013
		2014	=head1 ERROR AND EXCEPTION HANDLING
		2015
		2016	In general, AnyEvent does not do any error handling - it relies on the
		2017	caller to do that if required. The L<AnyEvent::Strict> module (see also
		2018	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		2019	checking of all AnyEvent methods, however, which is highly useful during
		2020	development.
		2021
		2022	As for exception handling (i.e. runtime errors and exceptions thrown while
		2023	executing a callback), this is not only highly event-loop specific, but
		2024	also not in any way wrapped by this module, as this is the job of the main
		2025	program.
		2026
		2027	The pure perl event loop simply re-throws the exception (usually
		2028	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		2029	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		2030	so on.
		2031
		2032	=head1 ENVIRONMENT VARIABLES
		2033
		2034	AnyEvent supports a number of environment variables that tune the
		2035	runtime behaviour. They are usually evaluated when AnyEvent is
		2036	loaded, initialised, or a submodule that uses them is loaded. Many of
		2037	them also cause AnyEvent to load additional modules - for example,
		2038	C<PERL_ANYEVENT_DEBUG_WRAP> causes the L<AnyEvent::Debug> module to be
		2039	loaded.
		2040
		2041	All the environment variables documented here start with
		2042	C<PERL_ANYEVENT_>, which is what AnyEvent considers its own
		2043	namespace. Other modules are encouraged (but by no means required) to use
		2044	C<PERL_ANYEVENT_SUBMODULE> if they have registered the AnyEvent::Submodule
		2045	namespace on CPAN, for any submodule. For example, L<AnyEvent::HTTP> could
		2046	be expected to use C<PERL_ANYEVENT_HTTP_PROXY> (it should not access env
		2047	variables starting with C<AE_>, see below).
		2048
		2049	All variables can also be set via the C<AE_> prefix, that is, instead
		2050	of setting C<PERL_ANYEVENT_VERBOSE> you can also set C<AE_VERBOSE>. In
		2051	case there is a clash btween anyevent and another program that uses
		2052	C<AE_something> you can set the corresponding C<PERL_ANYEVENT_something>
		2053	variable to the empty string, as those variables take precedence.
		2054
		2055	When AnyEvent is first loaded, it copies all C<AE_xxx> env variables
		2056	to their C<PERL_ANYEVENT_xxx> counterpart unless that variable already
		2057	exists. If taint mode is on, then AnyEvent will remove I<all> environment
		2058	variables starting with C<PERL_ANYEVENT_> from C<%ENV> (or replace them
		2059	with C<undef> or the empty string, if the corresaponding C<AE_> variable
		2060	is set).
		2061
		2062	The exact algorithm is currently:
		2063
		2064	1. if taint mode enabled, delete all PERL_ANYEVENT_xyz variables from %ENV
		2065	2. copy over AE_xyz to PERL_ANYEVENT_xyz unless the latter alraedy exists
		2066	3. if taint mode enabled, set all PERL_ANYEVENT_xyz variables to undef.
		2067
		2068	This ensures that child processes will not see the C<AE_> variables.
		2069
		2070	The following environment variables are currently known to AnyEvent:
		2071
		2072	=over 4
		2073
		2074	=item C<PERL_ANYEVENT_VERBOSE>
		2075
		2076	By default, AnyEvent will only log messages with loglevel C<3>
		2077	(C<critical>) or higher (see L<AnyEvent::Log>). You can set this
		2078	environment variable to a numerical loglevel to make AnyEvent more (or
		2079	less) talkative.
		2080
		2081	If you want to do more than just set the global logging level
		2082	you should have a look at C<PERL_ANYEVENT_LOG>, which allows much more
		2083	complex specifications.
		2084
		2085	When set to C<0> (C<off>), then no messages whatsoever will be logged with
		2086	the default logging settings.
		2087
		2088	When set to C<5> or higher (C<warn>), causes AnyEvent to warn about
		2089	unexpected conditions, such as not being able to load the event model
		2090	specified by C<PERL_ANYEVENT_MODEL>, or a guard callback throwing an
		2091	exception - this is the minimum recommended level.
		2092
		2093	When set to C<7> or higher (info), cause AnyEvent to report which event model it
		2094	chooses.
		2095
		2096	When set to C<8> or higher (debug), then AnyEvent will report extra information on
		2097	which optional modules it loads and how it implements certain features.
		2098
		2099	=item C<PERL_ANYEVENT_LOG>
		2100
		2101	Accepts rather complex logging specifications. For example, you could log
		2102	all C<debug> messages of some module to stderr, warnings and above to
		2103	stderr, and errors and above to syslog, with:
		2104
		2105	PERL_ANYEVENT_LOG=Some::Module=debug,+log:filter=warn,+%syslog:%syslog=error,syslog
		2106
		2107	For the rather extensive details, see L<AnyEvent::Log>.
		2108
		2109	This variable is evaluated when AnyEvent (or L<AnyEvent::Log>) is loaded,
		2110	so will take effect even before AnyEvent has initialised itself.
		2111
		2112	Note that specifying this environment variable causes the L<AnyEvent::Log>
		2113	module to be loaded, while C<PERL_ANYEVENT_VERBOSE> does not, so only
		2114	using the latter saves a few hundred kB of memory until the first message
		2115	is being logged.
		2116
		2117	=item C<PERL_ANYEVENT_STRICT>
		2118
		2119	AnyEvent does not do much argument checking by default, as thorough
		2120	argument checking is very costly. Setting this variable to a true value
		2121	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		2122	check the arguments passed to most method calls. If it finds any problems,
		2123	it will croak.
		2124
		2125	In other words, enables "strict" mode.
		2126
		2127	Unlike C<use strict> (or its modern cousin, C<< use L<common::sense>
		2128	>>, it is definitely recommended to keep it off in production. Keeping
		2129	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		2130	can be very useful, however.
		2131
		2132	=item C<PERL_ANYEVENT_DEBUG_SHELL>
		2133
		2134	If this env variable is nonempty, then its contents will be interpreted by
		2135	C<AnyEvent::Socket::parse_hostport> and C<AnyEvent::Debug::shell> (after
		2136	replacing every occurance of C<$$> by the process pid). The shell object
		2137	is saved in C<$AnyEvent::Debug::SHELL>.
		2138
		2139	This happens when the first watcher is created.
		2140
		2141	For example, to bind a debug shell on a unix domain socket in
		2142	F<< /tmp/debug<pid>.sock >>, you could use this:
		2143
		2144	PERL_ANYEVENT_DEBUG_SHELL=/tmp/debug\$\$.sock perlprog
		2145	# connect with e.g.: socat readline /tmp/debug123.sock
		2146
		2147	Or to bind to tcp port 4545 on localhost:
		2148
		2149	PERL_ANYEVENT_DEBUG_SHELL=127.0.0.1:4545 perlprog
		2150	# connect with e.g.: telnet localhost 4545
		2151
		2152	Note that creating sockets in F</tmp> or on localhost is very unsafe on
		2153	multiuser systems.
		2154
		2155	=item C<PERL_ANYEVENT_DEBUG_WRAP>
		2156
		2157	Can be set to C<0>, C<1> or C<2> and enables wrapping of all watchers for
		2158	debugging purposes. See C<AnyEvent::Debug::wrap> for details.
		2159
		2160	=item C<PERL_ANYEVENT_MODEL>
		2161
		2162	This can be used to specify the event model to be used by AnyEvent, before
		2163	auto detection and -probing kicks in.
		2164
		2165	It normally is a string consisting entirely of ASCII letters (e.g. C<EV>
		2166	or C<IOAsync>). The string C<AnyEvent::Impl::> gets prepended and the
		2167	resulting module name is loaded and - if the load was successful - used as
		2168	event model backend. If it fails to load then AnyEvent will proceed with
		2169	auto detection and -probing.
		2170
		2171	If the string ends with C<::> instead (e.g. C<AnyEvent::Impl::EV::>) then
		2172	nothing gets prepended and the module name is used as-is (hint: C<::> at
		2173	the end of a string designates a module name and quotes it appropriately).
		2174
		2175	For example, to force the pure perl model (L<AnyEvent::Loop::Perl>) you
		2176	could start your program like this:
		2177
		2178	PERL_ANYEVENT_MODEL=Perl perl ...
		2179
		2180	=item C<PERL_ANYEVENT_PROTOCOLS>
		2181
		2182	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		2183	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		2184	of auto probing).
		2185
		2186	Must be set to a comma-separated list of protocols or address families,
		2187	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		2188	used, and preference will be given to protocols mentioned earlier in the
		2189	list.
		2190
		2191	This variable can effectively be used for denial-of-service attacks
		2192	against local programs (e.g. when setuid), although the impact is likely
		2193	small, as the program has to handle conenction and other failures anyways.
		2194
		2195	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		2196	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		2197	- only support IPv4, never try to resolve or contact IPv6
		2198	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		2199	IPv6, but prefer IPv6 over IPv4.
		2200
		2201	=item C<PERL_ANYEVENT_HOSTS>
		2202
		2203	This variable, if specified, overrides the F</etc/hosts> file used by
		2204	L<AnyEvent::Socket>C<::resolve_sockaddr>, i.e. hosts aliases will be read
		2205	from that file instead.
		2206
		2207	=item C<PERL_ANYEVENT_EDNS0>
		2208
		2209	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension for
		2210	DNS. This extension is generally useful to reduce DNS traffic, especially
		2211	when DNSSEC is involved, but some (broken) firewalls drop such DNS
		2212	packets, which is why it is off by default.
		2213
		2214	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		2215	EDNS0 in its DNS requests.
		2216
		2217	=item C<PERL_ANYEVENT_MAX_FORKS>
		2218
		2219	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		2220	will create in parallel.
		2221
		2222	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		2223
		2224	The default value for the C<max_outstanding> parameter for the default DNS
		2225	resolver - this is the maximum number of parallel DNS requests that are
		2226	sent to the DNS server.
		2227
		2228	=item C<PERL_ANYEVENT_MAX_SIGNAL_LATENCY>
		2229
		2230	Perl has inherently racy signal handling (you can basically choose between
		2231	losing signals and memory corruption) - pure perl event loops (including
		2232	C<AnyEvent::Loop>, when C<Async::Interrupt> isn't available) therefore
		2233	have to poll regularly to avoid losing signals.
		2234
		2235	Some event loops are racy, but don't poll regularly, and some event loops
		2236	are written in C but are still racy. For those event loops, AnyEvent
		2237	installs a timer that regularly wakes up the event loop.
		2238
		2239	By default, the interval for this timer is C<10> seconds, but you can
		2240	override this delay with this environment variable (or by setting
		2241	the C<$AnyEvent::MAX_SIGNAL_LATENCY> variable before creating signal
		2242	watchers).
		2243
		2244	Lower values increase CPU (and energy) usage, higher values can introduce
		2245	long delays when reaping children or waiting for signals.
		2246
		2247	The L<AnyEvent::Async> module, if available, will be used to avoid this
		2248	polling (with most event loops).
		2249
		2250	=item C<PERL_ANYEVENT_RESOLV_CONF>
		2251
		2252	The absolute path to a F<resolv.conf>-style file to use instead of
		2253	F</etc/resolv.conf> (or the OS-specific configuration) in the default
		2254	resolver, or the empty string to select the default configuration.
		2255
		2256	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		2257
		2258	When neither C<ca_file> nor C<ca_path> was specified during
		2259	L<AnyEvent::TLS> context creation, and either of these environment
		2260	variables are nonempty, they will be used to specify CA certificate
		2261	locations instead of a system-dependent default.
		2262
		2263	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		2264
		2265	When these are set to C<1>, then the respective modules are not
		2266	loaded. Mostly good for testing AnyEvent itself.
		2267
		2268	=back
661		2269
662	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	2270	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
663		2271
664	This is an advanced topic that you do not normally need to use AnyEvent in	2272	This is an advanced topic that you do not normally need to use AnyEvent in
665	a module. This section is only of use to event loop authors who want to	2273	a module. This section is only of use to event loop authors who want to
…		…
699		2307
700	I<rxvt-unicode> also cheats a bit by not providing blocking access to	2308	I<rxvt-unicode> also cheats a bit by not providing blocking access to
701	condition variables: code blocking while waiting for a condition will	2309	condition variables: code blocking while waiting for a condition will
702	C<die>. This still works with most modules/usages, and blocking calls must	2310	C<die>. This still works with most modules/usages, and blocking calls must
703	not be done in an interactive application, so it makes sense.	2311	not be done in an interactive application, so it makes sense.
704
705	=head1 ENVIRONMENT VARIABLES
706
707	The following environment variables are used by this module:
708
709	=over 4
710
711	=item C<PERL_ANYEVENT_VERBOSE>
712
713	By default, AnyEvent will be completely silent except in fatal
714	conditions. You can set this environment variable to make AnyEvent more
715	talkative.
716
717	When set to C<1> or higher, causes AnyEvent to warn about unexpected
718	conditions, such as not being able to load the event model specified by
719	C<PERL_ANYEVENT_MODEL>.
720
721	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
722	model it chooses.
723
724	=item C<PERL_ANYEVENT_MODEL>
725
726	This can be used to specify the event model to be used by AnyEvent, before
727	autodetection and -probing kicks in. It must be a string consisting
728	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
729	and the resulting module name is loaded and if the load was successful,
730	used as event model. If it fails to load AnyEvent will proceed with
731	autodetection and -probing.
732
733	This functionality might change in future versions.
734
735	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
736	could start your program like this:
737
738	PERL_ANYEVENT_MODEL=Perl perl ...
739
740	=back
741		2312
742	=head1 EXAMPLE PROGRAM	2313	=head1 EXAMPLE PROGRAM
743		2314
744	The following program uses an I/O watcher to read data from STDIN, a timer	2315	The following program uses an I/O watcher to read data from STDIN, a timer
745	to display a message once per second, and a condition variable to quit the	2316	to display a message once per second, and a condition variable to quit the
…		…
754	poll => 'r',	2325	poll => 'r',
755	cb => sub {	2326	cb => sub {
756	warn "io event <$_[0]>\n"; # will always output <r>	2327	warn "io event <$_[0]>\n"; # will always output <r>
757	chomp (my $input = <STDIN>); # read a line	2328	chomp (my $input = <STDIN>); # read a line
758	warn "read: $input\n"; # output what has been read	2329	warn "read: $input\n"; # output what has been read
759	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	2330	$cv->send if $input =~ /^q/i; # quit program if /^q/i
760	},	2331	},
761	);	2332	);
762		2333
763	my $time_watcher; # can only be used once
764
765	sub new_timer {
766	$timer = AnyEvent->timer (after => 1, cb => sub {	2334	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
767	warn "timeout\n"; # print 'timeout' about every second	2335	warn "timeout\n"; # print 'timeout' at most every second
768	&new_timer; # and restart the time
769	});	2336	});
770	}
771		2337
772	new_timer; # create first timer
773
774	$cv->wait; # wait until user enters /^q/i	2338	$cv->recv; # wait until user enters /^q/i
775		2339
776	=head1 REAL-WORLD EXAMPLE	2340	=head1 REAL-WORLD EXAMPLE
777		2341
778	Consider the L<Net::FCP> module. It features (among others) the following	2342	Consider the L<Net::FCP> module. It features (among others) the following
779	API calls, which are to freenet what HTTP GET requests are to http:	2343	API calls, which are to freenet what HTTP GET requests are to http:
…		…
829	syswrite $txn->{fh}, $txn->{request}	2393	syswrite $txn->{fh}, $txn->{request}
830	or die "connection or write error";	2394	or die "connection or write error";
831	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	2395	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
832		2396
833	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	2397	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
834	result and signals any possible waiters that the request ahs finished:	2398	result and signals any possible waiters that the request has finished:
835		2399
836	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	2400	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
837		2401
838	if (end-of-file or data complete) {	2402	if (end-of-file or data complete) {
839	$txn->{result} = $txn->{buf};	2403	$txn->{result} = $txn->{buf};
840	$txn->{finished}->broadcast;	2404	$txn->{finished}->send;
841	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	2405	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
842	}	2406	}
843		2407
844	The C<result> method, finally, just waits for the finished signal (if the	2408	The C<result> method, finally, just waits for the finished signal (if the
845	request was already finished, it doesn't wait, of course, and returns the	2409	request was already finished, it doesn't wait, of course, and returns the
846	data:	2410	data:
847		2411
848	$txn->{finished}->wait;	2412	$txn->{finished}->recv;
849	return $txn->{result};	2413	return $txn->{result};
850		2414
851	The actual code goes further and collects all errors (C<die>s, exceptions)	2415	The actual code goes further and collects all errors (C<die>s, exceptions)
852	that occured during request processing. The C<result> method detects	2416	that occurred during request processing. The C<result> method detects
853	whether an exception as thrown (it is stored inside the $txn object)	2417	whether an exception as thrown (it is stored inside the $txn object)
854	and just throws the exception, which means connection errors and other	2418	and just throws the exception, which means connection errors and other
855	problems get reported tot he code that tries to use the result, not in a	2419	problems get reported to the code that tries to use the result, not in a
856	random callback.	2420	random callback.
857		2421
858	All of this enables the following usage styles:	2422	All of this enables the following usage styles:
859		2423
860	1. Blocking:	2424	1. Blocking:
…		…
888		2452
889	my $quit = AnyEvent->condvar;	2453	my $quit = AnyEvent->condvar;
890		2454
891	$fcp->txn_client_get ($url)->cb (sub {	2455	$fcp->txn_client_get ($url)->cb (sub {
892	...	2456	...
893	$quit->broadcast;	2457	$quit->send;
894	});	2458	});
895		2459
896	$quit->wait;	2460	$quit->recv;
897		2461
898		2462
899	=head1 BENCHMARK	2463	=head1 BENCHMARKS
900		2464
901	To give you an idea of the performance and overheads that AnyEvent adds	2465	To give you an idea of the performance and overheads that AnyEvent adds
902	over the event loops themselves (and to give you an impression of the	2466	over the event loops themselves and to give you an impression of the speed
903	speed of various event loops), here is a benchmark of various supported	2467	of various event loops I prepared some benchmarks.
904	event models natively and with anyevent. The benchmark creates a lot of	2468
905	timers (with a zero timeout) and I/O watchers (watching STDOUT, a pty, to	2469	=head2 BENCHMARKING ANYEVENT OVERHEAD
		2470
		2471	Here is a benchmark of various supported event models used natively and
		2472	through AnyEvent. The benchmark creates a lot of timers (with a zero
		2473	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
906	become writable, which it is), lets them fire exactly once and destroys	2474	which it is), lets them fire exactly once and destroys them again.
907	them again.
908		2475
909	Rewriting the benchmark to use many different sockets instead of using	2476	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
910	the same filehandle for all I/O watchers results in a much longer runtime	2477	distribution. It uses the L<AE> interface, which makes a real difference
911	(socket creation is expensive), but qualitatively the same figures, so it	2478	for the EV and Perl backends only.
912	was not used.
913		2479
914	=head2 Explanation of the columns	2480	=head3 Explanation of the columns
915		2481
916	I<watcher> is the number of event watchers created/destroyed. Since	2482	I<watcher> is the number of event watchers created/destroyed. Since
917	different event models feature vastly different performances, each event	2483	different event models feature vastly different performances, each event
918	loop was given a number of watchers so that overall runtime is acceptable	2484	loop was given a number of watchers so that overall runtime is acceptable
919	and similar between tested event loop (and keep them from crashing): Glib	2485	and similar between tested event loop (and keep them from crashing): Glib
…		…
929	all watchers, to avoid adding memory overhead. That means closure creation	2495	all watchers, to avoid adding memory overhead. That means closure creation
930	and memory usage is not included in the figures.	2496	and memory usage is not included in the figures.
931		2497
932	I<invoke> is the time, in microseconds, used to invoke a simple	2498	I<invoke> is the time, in microseconds, used to invoke a simple
933	callback. The callback simply counts down a Perl variable and after it was	2499	callback. The callback simply counts down a Perl variable and after it was
934	invoked "watcher" times, it would C<< ->broadcast >> a condvar once to	2500	invoked "watcher" times, it would C<< ->send >> a condvar once to
935	signal the end of this phase.	2501	signal the end of this phase.
936		2502
937	I<destroy> is the time, in microseconds, that it takes to destroy a single	2503	I<destroy> is the time, in microseconds, that it takes to destroy a single
938	watcher.	2504	watcher.
939		2505
940	=head2 Results	2506	=head3 Results
941		2507
942	name watchers bytes create invoke destroy comment	2508	name watchers bytes create invoke destroy comment
943	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	2509	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
944	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	2510	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
945	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	2511	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
946	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	2512	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
947	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	2513	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
948	Event/Any 16000 936 39.17 33.63 1.43 Event + AnyEvent watchers	2514	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
		2515	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
		2516	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
949	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	2517	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
950	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	2518	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
951	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	2519	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
952	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	2520	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
953		2521
954	=head2 Discussion	2522	=head3 Discussion
955		2523
956	The benchmark does I<not> measure scalability of the event loop very	2524	The benchmark does I<not> measure scalability of the event loop very
957	well. For example, a select-based event loop (such as the pure perl one)	2525	well. For example, a select-based event loop (such as the pure perl one)
958	can never compete with an event loop that uses epoll when the number of	2526	can never compete with an event loop that uses epoll when the number of
959	file descriptors grows high. In this benchmark, all events become ready at	2527	file descriptors grows high. In this benchmark, all events become ready at
960	the same time, so select/poll-based implementations get an unnatural speed	2528	the same time, so select/poll-based implementations get an unnatural speed
961	boost.	2529	boost.
962		2530
		2531	Also, note that the number of watchers usually has a nonlinear effect on
		2532	overall speed, that is, creating twice as many watchers doesn't take twice
		2533	the time - usually it takes longer. This puts event loops tested with a
		2534	higher number of watchers at a disadvantage.
		2535
		2536	To put the range of results into perspective, consider that on the
		2537	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		2538	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		2539	cycles with POE.
		2540
963	C<EV> is the sole leader regarding speed and memory use, which are both	2541	C<EV> is the sole leader regarding speed and memory use, which are both
964	maximal/minimal, respectively. Even when going through AnyEvent, it uses	2542	maximal/minimal, respectively. When using the L<AE> API there is zero
		2543	overhead (when going through the AnyEvent API create is about 5-6 times
		2544	slower, with other times being equal, so still uses far less memory than
965	far less memory than any other event loop and is still faster than Event	2545	any other event loop and is still faster than Event natively).
966	natively.
967		2546
968	The pure perl implementation is hit in a few sweet spots (both the	2547	The pure perl implementation is hit in a few sweet spots (both the
969	zero timeout and the use of a single fd hit optimisations in the perl	2548	constant timeout and the use of a single fd hit optimisations in the perl
970	interpreter and the backend itself, and all watchers become ready at the	2549	interpreter and the backend itself). Nevertheless this shows that it
971	same time). Nevertheless this shows that it adds very little overhead in	2550	adds very little overhead in itself. Like any select-based backend its
972	itself. Like any select-based backend its performance becomes really bad	2551	performance becomes really bad with lots of file descriptors (and few of
973	with lots of file descriptors (and few of them active), of course, but	2552	them active), of course, but this was not subject of this benchmark.
974	this was not subject of this benchmark.
975		2553
976	The C<Event> module has a relatively high setup and callback invocation cost,	2554	The C<Event> module has a relatively high setup and callback invocation
977	but overall scores on the third place.	2555	cost, but overall scores in on the third place.
978		2556
		2557	C<IO::Async> performs admirably well, about on par with C<Event>, even
		2558	when using its pure perl backend.
		2559
979	C<Glib>'s memory usage is quite a bit bit higher, but it features a	2560	C<Glib>'s memory usage is quite a bit higher, but it features a
980	faster callback invocation and overall ends up in the same class as	2561	faster callback invocation and overall ends up in the same class as
981	C<Event>. However, Glib scales extremely badly, doubling the number of	2562	C<Event>. However, Glib scales extremely badly, doubling the number of
982	watchers increases the processing time by more than a factor of four,	2563	watchers increases the processing time by more than a factor of four,
983	making it completely unusable when using larger numbers of watchers	2564	making it completely unusable when using larger numbers of watchers
984	(note that only a single file descriptor was used in the benchmark, so	2565	(note that only a single file descriptor was used in the benchmark, so
…		…
987	The C<Tk> adaptor works relatively well. The fact that it crashes with	2568	The C<Tk> adaptor works relatively well. The fact that it crashes with
988	more than 2000 watchers is a big setback, however, as correctness takes	2569	more than 2000 watchers is a big setback, however, as correctness takes
989	precedence over speed. Nevertheless, its performance is surprising, as the	2570	precedence over speed. Nevertheless, its performance is surprising, as the
990	file descriptor is dup()ed for each watcher. This shows that the dup()	2571	file descriptor is dup()ed for each watcher. This shows that the dup()
991	employed by some adaptors is not a big performance issue (it does incur a	2572	employed by some adaptors is not a big performance issue (it does incur a
992	hidden memory cost inside the kernel, though, that is not reflected in the	2573	hidden memory cost inside the kernel which is not reflected in the figures
993	figures above).	2574	above).
994		2575
995	C<POE>, regardless of underlying event loop (wether using its pure perl	2576	C<POE>, regardless of underlying event loop (whether using its pure perl
996	select-based backend or the Event module) shows abysmal performance and	2577	select-based backend or the Event module, the POE-EV backend couldn't
		2578	be tested because it wasn't working) shows abysmal performance and
997	memory usage: Watchers use almost 30 times as much memory as EV watchers,	2579	memory usage with AnyEvent: Watchers use almost 30 times as much memory
998	and 10 times as much memory as both Event or EV via AnyEvent. Watcher	2580	as EV watchers, and 10 times as much memory as Event (the high memory
		2581	requirements are caused by requiring a session for each watcher). Watcher
999	invocation is almost 900 times slower than with AnyEvent's pure perl	2582	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		2583	implementation.
		2584
1000	implementation. The design of the POE adaptor class in AnyEvent can not	2585	The design of the POE adaptor class in AnyEvent can not really account
1001	really account for this, as session creation overhead is small compared	2586	for the performance issues, though, as session creation overhead is
1002	to execution of the state machine, which is coded pretty optimally within	2587	small compared to execution of the state machine, which is coded pretty
1003	L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow.	2588	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		2589	using multiple sessions is not a good approach, especially regarding
		2590	memory usage, even the author of POE could not come up with a faster
		2591	design).
1004		2592
1005	=head2 Summary	2593	=head3 Summary
1006		2594
		2595	=over 4
		2596
1007	Using EV through AnyEvent is faster than any other event loop, but most	2597	=item * Using EV through AnyEvent is faster than any other event loop
1008	event loops have acceptable performance with or without AnyEvent.	2598	(even when used without AnyEvent), but most event loops have acceptable
		2599	performance with or without AnyEvent.
1009		2600
1010	The overhead AnyEvent adds is usually much smaller than the overhead of	2601	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
1011	the actual event loop, only with extremely fast event loops such as the EV	2602	the actual event loop, only with extremely fast event loops such as EV
1012	adds AnyEvent significant overhead.	2603	does AnyEvent add significant overhead.
1013		2604
1014	And you should simply avoid POE like the plague if you want performance or	2605	=item * You should avoid POE like the plague if you want performance or
1015	reasonable memory usage.	2606	reasonable memory usage.
1016		2607
		2608	=back
		2609
		2610	=head2 BENCHMARKING THE LARGE SERVER CASE
		2611
		2612	This benchmark actually benchmarks the event loop itself. It works by
		2613	creating a number of "servers": each server consists of a socket pair, a
		2614	timeout watcher that gets reset on activity (but never fires), and an I/O
		2615	watcher waiting for input on one side of the socket. Each time the socket
		2616	watcher reads a byte it will write that byte to a random other "server".
		2617
		2618	The effect is that there will be a lot of I/O watchers, only part of which
		2619	are active at any one point (so there is a constant number of active
		2620	fds for each loop iteration, but which fds these are is random). The
		2621	timeout is reset each time something is read because that reflects how
		2622	most timeouts work (and puts extra pressure on the event loops).
		2623
		2624	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
		2625	(1%) are active. This mirrors the activity of large servers with many
		2626	connections, most of which are idle at any one point in time.
		2627
		2628	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		2629	distribution. It uses the L<AE> interface, which makes a real difference
		2630	for the EV and Perl backends only.
		2631
		2632	=head3 Explanation of the columns
		2633
		2634	I<sockets> is the number of sockets, and twice the number of "servers" (as
		2635	each server has a read and write socket end).
		2636
		2637	I<create> is the time it takes to create a socket pair (which is
		2638	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		2639
		2640	I<request>, the most important value, is the time it takes to handle a
		2641	single "request", that is, reading the token from the pipe and forwarding
		2642	it to another server. This includes deleting the old timeout and creating
		2643	a new one that moves the timeout into the future.
		2644
		2645	=head3 Results
		2646
		2647	name sockets create request
		2648	EV 20000 62.66 7.99
		2649	Perl 20000 68.32 32.64
		2650	IOAsync 20000 174.06 101.15 epoll
		2651	IOAsync 20000 174.67 610.84 poll
		2652	Event 20000 202.69 242.91
		2653	Glib 20000 557.01 1689.52
		2654	POE 20000 341.54 12086.32 uses POE::Loop::Event
		2655
		2656	=head3 Discussion
		2657
		2658	This benchmark I<does> measure scalability and overall performance of the
		2659	particular event loop.
		2660
		2661	EV is again fastest. Since it is using epoll on my system, the setup time
		2662	is relatively high, though.
		2663
		2664	Perl surprisingly comes second. It is much faster than the C-based event
		2665	loops Event and Glib.
		2666
		2667	IO::Async performs very well when using its epoll backend, and still quite
		2668	good compared to Glib when using its pure perl backend.
		2669
		2670	Event suffers from high setup time as well (look at its code and you will
		2671	understand why). Callback invocation also has a high overhead compared to
		2672	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		2673	uses select or poll in basically all documented configurations.
		2674
		2675	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		2676	clearly fails to perform with many filehandles or in busy servers.
		2677
		2678	POE is still completely out of the picture, taking over 1000 times as long
		2679	as EV, and over 100 times as long as the Perl implementation, even though
		2680	it uses a C-based event loop in this case.
		2681
		2682	=head3 Summary
		2683
		2684	=over 4
		2685
		2686	=item * The pure perl implementation performs extremely well.
		2687
		2688	=item * Avoid Glib or POE in large projects where performance matters.
		2689
		2690	=back
		2691
		2692	=head2 BENCHMARKING SMALL SERVERS
		2693
		2694	While event loops should scale (and select-based ones do not...) even to
		2695	large servers, most programs we (or I :) actually write have only a few
		2696	I/O watchers.
		2697
		2698	In this benchmark, I use the same benchmark program as in the large server
		2699	case, but it uses only eight "servers", of which three are active at any
		2700	one time. This should reflect performance for a small server relatively
		2701	well.
		2702
		2703	The columns are identical to the previous table.
		2704
		2705	=head3 Results
		2706
		2707	name sockets create request
		2708	EV 16 20.00 6.54
		2709	Perl 16 25.75 12.62
		2710	Event 16 81.27 35.86
		2711	Glib 16 32.63 15.48
		2712	POE 16 261.87 276.28 uses POE::Loop::Event
		2713
		2714	=head3 Discussion
		2715
		2716	The benchmark tries to test the performance of a typical small
		2717	server. While knowing how various event loops perform is interesting, keep
		2718	in mind that their overhead in this case is usually not as important, due
		2719	to the small absolute number of watchers (that is, you need efficiency and
		2720	speed most when you have lots of watchers, not when you only have a few of
		2721	them).
		2722
		2723	EV is again fastest.
		2724
		2725	Perl again comes second. It is noticeably faster than the C-based event
		2726	loops Event and Glib, although the difference is too small to really
		2727	matter.
		2728
		2729	POE also performs much better in this case, but is is still far behind the
		2730	others.
		2731
		2732	=head3 Summary
		2733
		2734	=over 4
		2735
		2736	=item * C-based event loops perform very well with small number of
		2737	watchers, as the management overhead dominates.
		2738
		2739	=back
		2740
		2741	=head2 THE IO::Lambda BENCHMARK
		2742
		2743	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2744	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2745	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2746	shouldn't come as a surprise to anybody). As such, the benchmark is
		2747	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2748	very optimal. But how would AnyEvent compare when used without the extra
		2749	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2750
		2751	The benchmark itself creates an echo-server, and then, for 500 times,
		2752	connects to the echo server, sends a line, waits for the reply, and then
		2753	creates the next connection. This is a rather bad benchmark, as it doesn't
		2754	test the efficiency of the framework or much non-blocking I/O, but it is a
		2755	benchmark nevertheless.
		2756
		2757	name runtime
		2758	Lambda/select 0.330 sec
		2759	+ optimized 0.122 sec
		2760	Lambda/AnyEvent 0.327 sec
		2761	+ optimized 0.138 sec
		2762	Raw sockets/select 0.077 sec
		2763	POE/select, components 0.662 sec
		2764	POE/select, raw sockets 0.226 sec
		2765	POE/select, optimized 0.404 sec
		2766
		2767	AnyEvent/select/nb 0.085 sec
		2768	AnyEvent/EV/nb 0.068 sec
		2769	+state machine 0.134 sec
		2770
		2771	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2772	benchmarks actually make blocking connects and use 100% blocking I/O,
		2773	defeating the purpose of an event-based solution. All of the newly
		2774	written AnyEvent benchmarks use 100% non-blocking connects (using
		2775	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2776	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2777	generally require a lot more bookkeeping and event handling than blocking
		2778	connects (which involve a single syscall only).
		2779
		2780	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2781	offers similar expressive power as POE and IO::Lambda, using conventional
		2782	Perl syntax. This means that both the echo server and the client are 100%
		2783	non-blocking, further placing it at a disadvantage.
		2784
		2785	As you can see, the AnyEvent + EV combination even beats the
		2786	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2787	backend easily beats IO::Lambda and POE.
		2788
		2789	And even the 100% non-blocking version written using the high-level (and
		2790	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda
		2791	higher level ("unoptimised") abstractions by a large margin, even though
		2792	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
		2793
		2794	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2795	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2796	part of the IO::Lambda distribution and were used without any changes.
		2797
		2798
		2799	=head1 SIGNALS
		2800
		2801	AnyEvent currently installs handlers for these signals:
		2802
		2803	=over 4
		2804
		2805	=item SIGCHLD
		2806
		2807	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2808	emulation for event loops that do not support them natively. Also, some
		2809	event loops install a similar handler.
		2810
		2811	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2812	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2813
		2814	=item SIGPIPE
		2815
		2816	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2817	when AnyEvent gets loaded.
		2818
		2819	The rationale for this is that AnyEvent users usually do not really depend
		2820	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2821	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2822	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2823	some random socket.
		2824
		2825	The rationale for installing a no-op handler as opposed to ignoring it is
		2826	that this way, the handler will be restored to defaults on exec.
		2827
		2828	Feel free to install your own handler, or reset it to defaults.
		2829
		2830	=back
		2831
		2832	=cut
		2833
		2834	undef $SIG{CHLD}
		2835	if $SIG{CHLD} eq 'IGNORE';
		2836
		2837	$SIG{PIPE} = sub { }
		2838	unless defined $SIG{PIPE};
		2839
		2840	=head1 RECOMMENDED/OPTIONAL MODULES
		2841
		2842	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2843	its built-in modules) are required to use it.
		2844
		2845	That does not mean that AnyEvent won't take advantage of some additional
		2846	modules if they are installed.
		2847
		2848	This section explains which additional modules will be used, and how they
		2849	affect AnyEvent's operation.
		2850
		2851	=over 4
		2852
		2853	=item L<Async::Interrupt>
		2854
		2855	This slightly arcane module is used to implement fast signal handling: To
		2856	my knowledge, there is no way to do completely race-free and quick
		2857	signal handling in pure perl. To ensure that signals still get
		2858	delivered, AnyEvent will start an interval timer to wake up perl (and
		2859	catch the signals) with some delay (default is 10 seconds, look for
		2860	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2861
		2862	If this module is available, then it will be used to implement signal
		2863	catching, which means that signals will not be delayed, and the event loop
		2864	will not be interrupted regularly, which is more efficient (and good for
		2865	battery life on laptops).
		2866
		2867	This affects not just the pure-perl event loop, but also other event loops
		2868	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2869
		2870	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2871	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2872	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2873	does nothing for those backends.
		2874
		2875	=item L<EV>
		2876
		2877	This module isn't really "optional", as it is simply one of the backend
		2878	event loops that AnyEvent can use. However, it is simply the best event
		2879	loop available in terms of features, speed and stability: It supports
		2880	the AnyEvent API optimally, implements all the watcher types in XS, does
		2881	automatic timer adjustments even when no monotonic clock is available,
		2882	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2883	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2884	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2885
		2886	If you only use backends that rely on another event loop (e.g. C<Tk>),
		2887	then this module will do nothing for you.
		2888
		2889	=item L<Guard>
		2890
		2891	The guard module, when used, will be used to implement
		2892	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2893	lot less memory), but otherwise doesn't affect guard operation much. It is
		2894	purely used for performance.
		2895
		2896	=item L<JSON> and L<JSON::XS>
		2897
		2898	One of these modules is required when you want to read or write JSON data
		2899	via L<AnyEvent::Handle>. L<JSON> is also written in pure-perl, but can take
		2900	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2901
		2902	=item L<Net::SSLeay>
		2903
		2904	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2905	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2906	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2907
		2908	=item L<Time::HiRes>
		2909
		2910	This module is part of perl since release 5.008. It will be used when the
		2911	chosen event library does not come with a timing source of its own. The
		2912	pure-perl event loop (L<AnyEvent::Loop>) will additionally load it to
		2913	try to use a monotonic clock for timing stability.
		2914
		2915	=back
		2916
1017		2917
1018	=head1 FORK	2918	=head1 FORK
1019		2919
1020	Most event libraries are not fork-safe. The ones who are usually are	2920	Most event libraries are not fork-safe. The ones who are usually are
1021	because they are so inefficient. Only L<EV> is fully fork-aware.	2921	because they rely on inefficient but fork-safe C<select> or C<poll> calls
		2922	- higher performance APIs such as BSD's kqueue or the dreaded Linux epoll
		2923	are usually badly thought-out hacks that are incompatible with fork in
		2924	one way or another. Only L<EV> is fully fork-aware and ensures that you
		2925	continue event-processing in both parent and child (or both, if you know
		2926	what you are doing).
		2927
		2928	This means that, in general, you cannot fork and do event processing in
		2929	the child if the event library was initialised before the fork (which
		2930	usually happens when the first AnyEvent watcher is created, or the library
		2931	is loaded).
1022		2932
1023	If you have to fork, you must either do so I<before> creating your first	2933	If you have to fork, you must either do so I<before> creating your first
1024	watcher OR you must not use AnyEvent at all in the child.	2934	watcher OR you must not use AnyEvent at all in the child OR you must do
		2935	something completely out of the scope of AnyEvent.
		2936
		2937	The problem of doing event processing in the parent I<and> the child
		2938	is much more complicated: even for backends that I<are> fork-aware or
		2939	fork-safe, their behaviour is not usually what you want: fork clones all
		2940	watchers, that means all timers, I/O watchers etc. are active in both
		2941	parent and child, which is almost never what you want. USing C<exec>
		2942	to start worker children from some kind of manage rprocess is usually
		2943	preferred, because it is much easier and cleaner, at the expense of having
		2944	to have another binary.
1025		2945
1026		2946
1027	=head1 SECURITY CONSIDERATIONS	2947	=head1 SECURITY CONSIDERATIONS
1028		2948
1029	AnyEvent can be forced to load any event model via	2949	AnyEvent can be forced to load any event model via
…		…
1034	specified in the variable.	2954	specified in the variable.
1035		2955
1036	You can make AnyEvent completely ignore this variable by deleting it	2956	You can make AnyEvent completely ignore this variable by deleting it
1037	before the first watcher gets created, e.g. with a C<BEGIN> block:	2957	before the first watcher gets created, e.g. with a C<BEGIN> block:
1038		2958
1039	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	2959	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1040		2960
1041	use AnyEvent;	2961	use AnyEvent;
		2962
		2963	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		2964	be used to probe what backend is used and gain other information (which is
		2965	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2966	$ENV{PERL_ANYEVENT_STRICT}.
		2967
		2968	Note that AnyEvent will remove I<all> environment variables starting with
		2969	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2970	enabled.
		2971
		2972
		2973	=head1 BUGS
		2974
		2975	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2976	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2977	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2978	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2979	pronounced).
1042		2980
1043		2981
1044	=head1 SEE ALSO	2982	=head1 SEE ALSO
1045		2983
1046	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	2984	Tutorial/Introduction: L<AnyEvent::Intro>.
1047	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,
1048	L<Event::Lib>, L<Qt>, L<POE>.
1049		2985
1050	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	2986	FAQ: L<AnyEvent::FAQ>.
		2987
		2988	Utility functions: L<AnyEvent::Util> (misc. grab-bag), L<AnyEvent::Log>
		2989	(simply logging).
		2990
		2991	Development/Debugging: L<AnyEvent::Strict> (stricter checking),
		2992	L<AnyEvent::Debug> (interactive shell, watcher tracing).
		2993
		2994	Supported event modules: L<AnyEvent::Loop>, L<EV>, L<EV::Glib>,
		2995	L<Glib::EV>, L<Event>, L<Glib::Event>, L<Glib>, L<Tk>, L<Event::Lib>,
		2996	L<Qt>, L<POE>, L<FLTK>.
		2997
		2998	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
		2999	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
		3000	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1051	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,	3001	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>, L<Anyevent::Impl::Irssi>,
1052	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,	3002	L<AnyEvent::Impl::FLTK>.
1053	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.
1054		3003
		3004	Non-blocking handles, pipes, stream sockets, TCP clients and
		3005	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
		3006
		3007	Asynchronous DNS: L<AnyEvent::DNS>.
		3008
		3009	Thread support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
		3010
1055	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	3011	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::IRC>,
		3012	L<AnyEvent::HTTP>.
1056		3013
1057		3014
1058	=head1 AUTHOR	3015	=head1 AUTHOR
1059		3016
1060	Marc Lehmann <schmorp@schmorp.de>	3017	Marc Lehmann <schmorp@schmorp.de>
1061	http://home.schmorp.de/	3018	http://home.schmorp.de/
1062		3019
1063	=cut	3020	=cut
1064		3021
1065	1	3022	1
1066		3023

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