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Revision 1.385 by root, Mon Sep 5 08:51:14 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	#TODO#
72
73	Net::IRC3
74	AnyEvent::HTTPD
75	AnyEvent::DNS
76	IO::AnyEvent
77	Net::FPing
78	Net::XMPP2
79	Coro
80
81	AnyEvent::IRC
82	AnyEvent::HTTPD
83	AnyEvent::DNS
84	AnyEvent::Handle
85	AnyEvent::Socket
86	AnyEvent::FPing
87	AnyEvent::XMPP
88	AnyEvent::SNMP
89	Coro
90
91	=head1 DESCRIPTION	114	=head1 DESCRIPTION
92		115
93	L<AnyEvent> provides an identical interface to multiple event loops. This	116	L<AnyEvent> provides a uniform interface to various event loops. This
94	allows module authors to utilise an event loop without forcing module	117	allows module authors to use event loop functionality without forcing
95	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
96	peacefully at any one time).	119	than one event loop cannot coexist peacefully).
97		120
98	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>
99	module.	122	module.
100		123
101	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
102	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
103	following modules is already loaded: L<Coro::EV>, L<Coro::Event>, L<EV>,	126	following modules is already loaded: L<EV>, L<AnyEvent::Loop>,
104	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
105	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
106	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
107	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
108	be successfully loaded will be used. If, after this, still none could be	131	the other two are not normally tried.
109	found, AnyEvent will fall back to a pure-perl event loop, which is not
110	very efficient, but should work everywhere.
111		132
112	Because AnyEvent first checks for modules that are already loaded, loading	133	Because AnyEvent first checks for modules that are already loaded, loading
113	an event model explicitly before first using AnyEvent will likely make	134	an event model explicitly before first using AnyEvent will likely make
114	that model the default. For example:	135	that model the default. For example:
115		136
…		…
117	use AnyEvent;	138	use AnyEvent;
118		139
119	# .. AnyEvent will likely default to Tk	140	# .. AnyEvent will likely default to Tk
120		141
121	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
122	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,
123	use AnyEvent so their modules work together with others seamlessly...	144	as very few modules hardcode event loops without announcing this very
		145	loudly.
124		146
125	The pure-perl implementation of AnyEvent is called	147	The pure-perl implementation of AnyEvent is called C<AnyEvent::Loop>. Like
126	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
127	explicitly.	149	availability of that event loop :)
128		150
129	=head1 WATCHERS	151	=head1 WATCHERS
130		152
131	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
132	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
133	the callback to call, the filehandle to watch, etc.	155	the callback to call, the file handle to watch, etc.
134		156
135	These watchers are normal Perl objects with normal Perl lifetime. After	157	These watchers are normal Perl objects with normal Perl lifetime. After
136	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
137	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
138	is in control).	160	is in control).
139		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
140	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
141	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
142	to it).	170	to it).
143		171
144	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.
145		173
146	Many watchers either are used with "recursion" (repeating timers for	174	Many watchers either are used with "recursion" (repeating timers for
147	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.
148		176
149	An any way to achieve that is this pattern:	177	One way to achieve that is this pattern:
150		178
151	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	179	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
152	# you can use $w here, for example to undef it	180	# you can use $w here, for example to undef it
153	undef $w;	181	undef $w;
154	});	182	});
155		183
156	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,
157	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
158	declared.	186	declared.
159		187
160	=head2 I/O WATCHERS	188	=head2 I/O WATCHERS
161		189
		190	$w = AnyEvent->io (
		191	fh => <filehandle_or_fileno>,
		192	poll => <"r" or "w">,
		193	cb => <callback>,
		194	);
		195
162	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
163	with the following mandatory key-value pairs as arguments:	197	with the following mandatory key-value pairs as arguments:
164		198
165	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
166	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
167	which creates a watcher waiting for "r"eadable or "w"ritable events,	207	watcher waiting for "r"eadable or "w"ritable events, respectively.
		208
168	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.
169	becomes ready.
170		210
171	Although the callback might get passed parameters, their value and	211	Although the callback might get passed parameters, their value and
172	presence is undefined and you cannot rely on them. Portable AnyEvent	212	presence is undefined and you cannot rely on them. Portable AnyEvent
173	callbacks cannot use arguments passed to I/O watcher callbacks.	213	callbacks cannot use arguments passed to I/O watcher callbacks.
174		214
175	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.
176	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
177	underlying file descriptor.	217	underlying file descriptor.
178		218
179	Some event loops issue spurious readyness notifications, so you should	219	Some event loops issue spurious readiness notifications, so you should
180	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
181	handles.	221	handles.
182		222
183	Example:
184
185	# 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
186	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	226	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
187	chomp (my $input = <STDIN>);	227	chomp (my $input = <STDIN>);
188	warn "read: $input\n";	228	warn "read: $input\n";
189	undef $w;	229	undef $w;
190	});	230	});
191		231
192	=head2 TIME WATCHERS	232	=head2 TIME WATCHERS
193		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
194	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 >>
195	method with the following mandatory arguments:	243	method with the following mandatory arguments:
196		244
197	C<after> specifies after how many seconds (fractional values are	245	C<after> specifies after how many seconds (fractional values are
198	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
…		…
200		248
201	Although the callback might get passed parameters, their value and	249	Although the callback might get passed parameters, their value and
202	presence is undefined and you cannot rely on them. Portable AnyEvent	250	presence is undefined and you cannot rely on them. Portable AnyEvent
203	callbacks cannot use arguments passed to time watcher callbacks.	251	callbacks cannot use arguments passed to time watcher callbacks.
204		252
205	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
206	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
207	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.
208		258
209	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.
210		262
211	# fire an event after 7.7 seconds	263	Example: fire an event after 7.7 seconds.
		264
212	my $w = AnyEvent->timer (after => 7.7, cb => sub {	265	my $w = AnyEvent->timer (after => 7.7, cb => sub {
213	warn "timeout\n";	266	warn "timeout\n";
214	});	267	});
215		268
216	# to cancel the timer:	269	# to cancel the timer:
217	undef $w;	270	undef $w;
218		271
219	Example 2:
220
221	# 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.
222	my $w;
223		273
224	my $cb = sub {
225	# cancel the old timer while creating a new one
226	$w = AnyEvent->timer (after => 1, cb => $cb);	274	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		275	warn "timeout\n";
227	};	276	};
228
229	# start the "loop" by creating the first watcher
230	$w = AnyEvent->timer (after => 0.5, cb => $cb);
231		277
232	=head3 TIMING ISSUES	278	=head3 TIMING ISSUES
233		279
234	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
235	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
…		…
237		283
238	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
239	use absolute time internally. This makes a difference when your clock	285	use absolute time internally. This makes a difference when your clock
240	"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
241	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
242	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.
243		289
244	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
245	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
246	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)
247	timers.	293	timers.
248		294
249	AnyEvent always prefers relative timers, if available, matching the	295	AnyEvent always prefers relative timers, if available, matching the
250	AnyEvent API.	296	AnyEvent API.
251		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
252	=head2 SIGNAL WATCHERS	383	=head2 SIGNAL WATCHERS
253		384
		385	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		386
254	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
255	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
256	be invoked whenever a signal occurs.	389	callback to be invoked whenever a signal occurs.
257		390
258	Although the callback might get passed parameters, their value and	391	Although the callback might get passed parameters, their value and
259	presence is undefined and you cannot rely on them. Portable AnyEvent	392	presence is undefined and you cannot rely on them. Portable AnyEvent
260	callbacks cannot use arguments passed to signal watcher callbacks.	393	callbacks cannot use arguments passed to signal watcher callbacks.
261		394
262	Multiple signal occurances can be clumped together into one callback	395	Multiple signal occurrences can be clumped together into one callback
263	invocation, and callback invocation will be synchronous. synchronous means	396	invocation, and callback invocation will be synchronous. Synchronous means
264	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,
265	but it is guarenteed not to interrupt any other callbacks.	398	but it is guaranteed not to interrupt any other callbacks.
266		399
267	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
268	between multiple watchers.	401	between multiple watchers, and AnyEvent will ensure that signals will not
		402	interrupt your program at bad times.
269		403
270	This watcher might use C<%SIG>, so programs overwriting those signals	404	This watcher might use C<%SIG> (depending on the event loop used),
271	directly will likely not work correctly.	405	so programs overwriting those signals directly will likely not work
		406	correctly.
272		407
273	Example: exit on SIGINT	408	Example: exit on SIGINT
274		409
275	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	410	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
276		411
		412	=head3 Restart Behaviour
		413
		414	While restart behaviour is up to the event loop implementation, most will
		415	not restart syscalls (that includes L<Async::Interrupt> and AnyEvent's
		416	pure perl implementation).
		417
		418	=head3 Safe/Unsafe Signals
		419
		420	Perl signals can be either "safe" (synchronous to opcode handling) or
		421	"unsafe" (asynchronous) - the former might get delayed indefinitely, the
		422	latter might corrupt your memory.
		423
		424	AnyEvent signal handlers are, in addition, synchronous to the event loop,
		425	i.e. they will not interrupt your running perl program but will only be
		426	called as part of the normal event handling (just like timer, I/O etc.
		427	callbacks, too).
		428
		429	=head3 Signal Races, Delays and Workarounds
		430
		431	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		432	callbacks to signals in a generic way, which is a pity, as you cannot
		433	do race-free signal handling in perl, requiring C libraries for
		434	this. AnyEvent will try to do its best, which means in some cases,
		435	signals will be delayed. The maximum time a signal might be delayed is
		436	specified in C<$AnyEvent::MAX_SIGNAL_LATENCY> (default: 10 seconds). This
		437	variable can be changed only before the first signal watcher is created,
		438	and should be left alone otherwise. This variable determines how often
		439	AnyEvent polls for signals (in case a wake-up was missed). Higher values
		440	will cause fewer spurious wake-ups, which is better for power and CPU
		441	saving.
		442
		443	All these problems can be avoided by installing the optional
		444	L<Async::Interrupt> module, which works with most event loops. It will not
		445	work with inherently broken event loops such as L<Event> or L<Event::Lib>
		446	(and not with L<POE> currently, as POE does its own workaround with
		447	one-second latency). For those, you just have to suffer the delays.
		448
277	=head2 CHILD PROCESS WATCHERS	449	=head2 CHILD PROCESS WATCHERS
278		450
		451	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		452
279	You can also watch on a child process exit and catch its exit status.	453	You can also watch for a child process exit and catch its exit status.
280		454
281	The child process is specified by the C<pid> argument (if set to C<0>, it	455	The child process is specified by the C<pid> argument (on some backends,
282	watches for any child process exit). The watcher will trigger as often	456	using C<0> watches for any child process exit, on others this will
283	as status change for the child are received. This works by installing a	457	croak). The watcher will be triggered only when the child process has
284	signal handler for C<SIGCHLD>. The callback will be called with the pid	458	finished and an exit status is available, not on any trace events
285	and exit status (as returned by waitpid), so unlike other watcher types,	459	(stopped/continued).
286	you I<can> rely on child watcher callback arguments.	460
		461	The callback will be called with the pid and exit status (as returned by
		462	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		463	callback arguments.
		464
		465	This watcher type works by installing a signal handler for C<SIGCHLD>,
		466	and since it cannot be shared, nothing else should use SIGCHLD or reap
		467	random child processes (waiting for specific child processes, e.g. inside
		468	C<system>, is just fine).
287		469
288	There is a slight catch to child watchers, however: you usually start them	470	There is a slight catch to child watchers, however: you usually start them
289	I<after> the child process was created, and this means the process could	471	I<after> the child process was created, and this means the process could
290	have exited already (and no SIGCHLD will be sent anymore).	472	have exited already (and no SIGCHLD will be sent anymore).
291		473
292	Not all event models handle this correctly (POE doesn't), but even for	474	Not all event models handle this correctly (neither POE nor IO::Async do,
		475	see their AnyEvent::Impl manpages for details), but even for event models
293	event models that I<do> handle this correctly, they usually need to be	476	that I<do> handle this correctly, they usually need to be loaded before
294	loaded before the process exits (i.e. before you fork in the first place).	477	the process exits (i.e. before you fork in the first place). AnyEvent's
		478	pure perl event loop handles all cases correctly regardless of when you
		479	start the watcher.
295		480
296	This means you cannot create a child watcher as the very first thing in an	481	This means you cannot create a child watcher as the very first
297	AnyEvent program, you I<have> to create at least one watcher before you	482	thing in an AnyEvent program, you I<have> to create at least one
298	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).	483	watcher before you C<fork> the child (alternatively, you can call
		484	C<AnyEvent::detect>).
		485
		486	As most event loops do not support waiting for child events, they will be
		487	emulated by AnyEvent in most cases, in which case the latency and race
		488	problems mentioned in the description of signal watchers apply.
299		489
300	Example: fork a process and wait for it	490	Example: fork a process and wait for it
301		491
302	my $done = AnyEvent->condvar;	492	my $done = AnyEvent->condvar;
303		493
304	AnyEvent::detect; # force event module to be initialised
305
306	my $pid = fork or exit 5;	494	my $pid = fork or exit 5;
307		495
308	my $w = AnyEvent->child (	496	my $w = AnyEvent->child (
309	pid => $pid,	497	pid => $pid,
310	cb => sub {	498	cb => sub {
311	my ($pid, $status) = @_;	499	my ($pid, $status) = @_;
312	warn "pid $pid exited with status $status";	500	warn "pid $pid exited with status $status";
313	$done->broadcast;	501	$done->send;
314	},	502	},
315	);	503	);
316		504
317	# do something else, then wait for process exit	505	# do something else, then wait for process exit
318	$done->wait;	506	$done->recv;
		507
		508	=head2 IDLE WATCHERS
		509
		510	$w = AnyEvent->idle (cb => <callback>);
		511
		512	This will repeatedly invoke the callback after the process becomes idle,
		513	until either the watcher is destroyed or new events have been detected.
		514
		515	Idle watchers are useful when there is a need to do something, but it
		516	is not so important (or wise) to do it instantly. The callback will be
		517	invoked only when there is "nothing better to do", which is usually
		518	defined as "all outstanding events have been handled and no new events
		519	have been detected". That means that idle watchers ideally get invoked
		520	when the event loop has just polled for new events but none have been
		521	detected. Instead of blocking to wait for more events, the idle watchers
		522	will be invoked.
		523
		524	Unfortunately, most event loops do not really support idle watchers (only
		525	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		526	will simply call the callback "from time to time".
		527
		528	Example: read lines from STDIN, but only process them when the
		529	program is otherwise idle:
		530
		531	my @lines; # read data
		532	my $idle_w;
		533	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		534	push @lines, scalar <STDIN>;
		535
		536	# start an idle watcher, if not already done
		537	$idle_w ||= AnyEvent->idle (cb => sub {
		538	# handle only one line, when there are lines left
		539	if (my $line = shift @lines) {
		540	print "handled when idle: $line";
		541	} else {
		542	# otherwise disable the idle watcher again
		543	undef $idle_w;
		544	}
		545	});
		546	});
319		547
320	=head2 CONDITION VARIABLES	548	=head2 CONDITION VARIABLES
321		549
		550	$cv = AnyEvent->condvar;
		551
		552	$cv->send (<list>);
		553	my @res = $cv->recv;
		554
		555	If you are familiar with some event loops you will know that all of them
		556	require you to run some blocking "loop", "run" or similar function that
		557	will actively watch for new events and call your callbacks.
		558
		559	AnyEvent is slightly different: it expects somebody else to run the event
		560	loop and will only block when necessary (usually when told by the user).
		561
		562	The tool to do that is called a "condition variable", so called because
		563	they represent a condition that must become true.
		564
		565	Now is probably a good time to look at the examples further below.
		566
322	Condition variables can be created by calling the C<< AnyEvent->condvar >>	567	Condition variables can be created by calling the C<< AnyEvent->condvar
323	method without any arguments.	568	>> method, usually without arguments. The only argument pair allowed is
		569	C<cb>, which specifies a callback to be called when the condition variable
		570	becomes true, with the condition variable as the first argument (but not
		571	the results).
324		572
325	A condition variable waits for a condition - precisely that the C<<	573	After creation, the condition variable is "false" until it becomes "true"
326	->broadcast >> method has been called.	574	by calling the C<send> method (or calling the condition variable as if it
		575	were a callback, read about the caveats in the description for the C<<
		576	->send >> method).
327		577
328	They are very useful to signal that a condition has been fulfilled, for	578	Since condition variables are the most complex part of the AnyEvent API, here are
		579	some different mental models of what they are - pick the ones you can connect to:
		580
		581	=over 4
		582
		583	=item * Condition variables are like callbacks - you can call them (and pass them instead
		584	of callbacks). Unlike callbacks however, you can also wait for them to be called.
		585
		586	=item * Condition variables are signals - one side can emit or send them,
		587	the other side can wait for them, or install a handler that is called when
		588	the signal fires.
		589
		590	=item * Condition variables are like "Merge Points" - points in your program
		591	where you merge multiple independent results/control flows into one.
		592
		593	=item * Condition variables represent a transaction - functions that start
		594	some kind of transaction can return them, leaving the caller the choice
		595	between waiting in a blocking fashion, or setting a callback.
		596
		597	=item * Condition variables represent future values, or promises to deliver
		598	some result, long before the result is available.
		599
		600	=back
		601
		602	Condition variables are very useful to signal that something has finished,
329	example, if you write a module that does asynchronous http requests,	603	for example, if you write a module that does asynchronous http requests,
330	then a condition variable would be the ideal candidate to signal the	604	then a condition variable would be the ideal candidate to signal the
331	availability of results.	605	availability of results. The user can either act when the callback is
		606	called or can synchronously C<< ->recv >> for the results.
332		607
333	You can also use condition variables to block your main program until	608	You can also use them to simulate traditional event loops - for example,
334	an event occurs - for example, you could C<< ->wait >> in your main	609	you can block your main program until an event occurs - for example, you
335	program until the user clicks the Quit button in your app, which would C<<	610	could C<< ->recv >> in your main program until the user clicks the Quit
336	->broadcast >> the "quit" event.	611	button of your app, which would C<< ->send >> the "quit" event.
337		612
338	Note that condition variables recurse into the event loop - if you have	613	Note that condition variables recurse into the event loop - if you have
339	two pirces of code that call C<< ->wait >> in a round-robbin fashion, you	614	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
340	lose. Therefore, condition variables are good to export to your caller, but	615	lose. Therefore, condition variables are good to export to your caller, but
341	you should avoid making a blocking wait yourself, at least in callbacks,	616	you should avoid making a blocking wait yourself, at least in callbacks,
342	as this asks for trouble.	617	as this asks for trouble.
343		618
344	This object has two methods:	619	Condition variables are represented by hash refs in perl, and the keys
		620	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
		621	easy (it is often useful to build your own transaction class on top of
		622	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
		623	its C<new> method in your own C<new> method.
		624
		625	There are two "sides" to a condition variable - the "producer side" which
		626	eventually calls C<< -> send >>, and the "consumer side", which waits
		627	for the send to occur.
		628
		629	Example: wait for a timer.
		630
		631	# condition: "wait till the timer is fired"
		632	my $timer_fired = AnyEvent->condvar;
		633
		634	# create the timer - we could wait for, say
		635	# a handle becomign ready, or even an
		636	# AnyEvent::HTTP request to finish, but
		637	# in this case, we simply use a timer:
		638	my $w = AnyEvent->timer (
		639	after => 1,
		640	cb => sub { $timer_fired->send },
		641	);
		642
		643	# this "blocks" (while handling events) till the callback
		644	# calls ->send
		645	$timer_fired->recv;
		646
		647	Example: wait for a timer, but take advantage of the fact that condition
		648	variables are also callable directly.
		649
		650	my $done = AnyEvent->condvar;
		651	my $delay = AnyEvent->timer (after => 5, cb => $done);
		652	$done->recv;
		653
		654	Example: Imagine an API that returns a condvar and doesn't support
		655	callbacks. This is how you make a synchronous call, for example from
		656	the main program:
		657
		658	use AnyEvent::CouchDB;
		659
		660	...
		661
		662	my @info = $couchdb->info->recv;
		663
		664	And this is how you would just set a callback to be called whenever the
		665	results are available:
		666
		667	$couchdb->info->cb (sub {
		668	my @info = $_[0]->recv;
		669	});
		670
		671	=head3 METHODS FOR PRODUCERS
		672
		673	These methods should only be used by the producing side, i.e. the
		674	code/module that eventually sends the signal. Note that it is also
		675	the producer side which creates the condvar in most cases, but it isn't
		676	uncommon for the consumer to create it as well.
345		677
346	=over 4	678	=over 4
347		679
		680	=item $cv->send (...)
		681
		682	Flag the condition as ready - a running C<< ->recv >> and all further
		683	calls to C<recv> will (eventually) return after this method has been
		684	called. If nobody is waiting the send will be remembered.
		685
		686	If a callback has been set on the condition variable, it is called
		687	immediately from within send.
		688
		689	Any arguments passed to the C<send> call will be returned by all
		690	future C<< ->recv >> calls.
		691
		692	Condition variables are overloaded so one can call them directly (as if
		693	they were a code reference). Calling them directly is the same as calling
		694	C<send>.
		695
		696	=item $cv->croak ($error)
		697
		698	Similar to send, but causes all calls to C<< ->recv >> to invoke
		699	C<Carp::croak> with the given error message/object/scalar.
		700
		701	This can be used to signal any errors to the condition variable
		702	user/consumer. Doing it this way instead of calling C<croak> directly
		703	delays the error detection, but has the overwhelming advantage that it
		704	diagnoses the error at the place where the result is expected, and not
		705	deep in some event callback with no connection to the actual code causing
		706	the problem.
		707
		708	=item $cv->begin ([group callback])
		709
348	=item $cv->wait	710	=item $cv->end
349		711
350	Wait (blocking if necessary) until the C<< ->broadcast >> method has been	712	These two methods can be used to combine many transactions/events into
351	called on c<$cv>, while servicing other watchers normally.	713	one. For example, a function that pings many hosts in parallel might want
		714	to use a condition variable for the whole process.
352		715
		716	Every call to C<< ->begin >> will increment a counter, and every call to
		717	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
		718	>>, the (last) callback passed to C<begin> will be executed, passing the
		719	condvar as first argument. That callback is I<supposed> to call C<< ->send
		720	>>, but that is not required. If no group callback was set, C<send> will
		721	be called without any arguments.
		722
		723	You can think of C<< $cv->send >> giving you an OR condition (one call
		724	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		725	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		726
		727	Let's start with a simple example: you have two I/O watchers (for example,
		728	STDOUT and STDERR for a program), and you want to wait for both streams to
		729	close before activating a condvar:
		730
		731	my $cv = AnyEvent->condvar;
		732
		733	$cv->begin; # first watcher
		734	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		735	defined sysread $fh1, my $buf, 4096
		736	or $cv->end;
		737	});
		738
		739	$cv->begin; # second watcher
		740	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		741	defined sysread $fh2, my $buf, 4096
		742	or $cv->end;
		743	});
		744
		745	$cv->recv;
		746
		747	This works because for every event source (EOF on file handle), there is
		748	one call to C<begin>, so the condvar waits for all calls to C<end> before
		749	sending.
		750
		751	The ping example mentioned above is slightly more complicated, as the
		752	there are results to be passwd back, and the number of tasks that are
		753	begun can potentially be zero:
		754
		755	my $cv = AnyEvent->condvar;
		756
		757	my %result;
		758	$cv->begin (sub { shift->send (\%result) });
		759
		760	for my $host (@list_of_hosts) {
		761	$cv->begin;
		762	ping_host_then_call_callback $host, sub {
		763	$result{$host} = ...;
		764	$cv->end;
		765	};
		766	}
		767
		768	$cv->end;
		769
		770	This code fragment supposedly pings a number of hosts and calls
		771	C<send> after results for all then have have been gathered - in any
		772	order. To achieve this, the code issues a call to C<begin> when it starts
		773	each ping request and calls C<end> when it has received some result for
		774	it. Since C<begin> and C<end> only maintain a counter, the order in which
		775	results arrive is not relevant.
		776
		777	There is an additional bracketing call to C<begin> and C<end> outside the
		778	loop, which serves two important purposes: first, it sets the callback
		779	to be called once the counter reaches C<0>, and second, it ensures that
		780	C<send> is called even when C<no> hosts are being pinged (the loop
		781	doesn't execute once).
		782
		783	This is the general pattern when you "fan out" into multiple (but
		784	potentially zero) subrequests: use an outer C<begin>/C<end> pair to set
		785	the callback and ensure C<end> is called at least once, and then, for each
		786	subrequest you start, call C<begin> and for each subrequest you finish,
		787	call C<end>.
		788
		789	=back
		790
		791	=head3 METHODS FOR CONSUMERS
		792
		793	These methods should only be used by the consuming side, i.e. the
		794	code awaits the condition.
		795
		796	=over 4
		797
		798	=item $cv->recv
		799
		800	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
		801	>> methods have been called on C<$cv>, while servicing other watchers
		802	normally.
		803
353	You can only wait once on a condition - additional calls will return	804	You can only wait once on a condition - additional calls are valid but
354	immediately.	805	will return immediately.
		806
		807	If an error condition has been set by calling C<< ->croak >>, then this
		808	function will call C<croak>.
		809
		810	In list context, all parameters passed to C<send> will be returned,
		811	in scalar context only the first one will be returned.
		812
		813	Note that doing a blocking wait in a callback is not supported by any
		814	event loop, that is, recursive invocation of a blocking C<< ->recv
		815	>> is not allowed, and the C<recv> call will C<croak> if such a
		816	condition is detected. This condition can be slightly loosened by using
		817	L<Coro::AnyEvent>, which allows you to do a blocking C<< ->recv >> from
		818	any thread that doesn't run the event loop itself.
355		819
356	Not all event models support a blocking wait - some die in that case	820	Not all event models support a blocking wait - some die in that case
357	(programs might want to do that to stay interactive), so I<if you are	821	(programs might want to do that to stay interactive), so I<if you are
358	using this from a module, never require a blocking wait>, but let the	822	using this from a module, never require a blocking wait>. Instead, let the
359	caller decide whether the call will block or not (for example, by coupling	823	caller decide whether the call will block or not (for example, by coupling
360	condition variables with some kind of request results and supporting	824	condition variables with some kind of request results and supporting
361	callbacks so the caller knows that getting the result will not block,	825	callbacks so the caller knows that getting the result will not block,
362	while still suppporting blocking waits if the caller so desires).	826	while still supporting blocking waits if the caller so desires).
363		827
364	Another reason I<never> to C<< ->wait >> in a module is that you cannot	828	You can ensure that C<< ->recv >> never blocks by setting a callback and
365	sensibly have two C<< ->wait >>'s in parallel, as that would require	829	only calling C<< ->recv >> from within that callback (or at a later
366	multiple interpreters or coroutines/threads, none of which C<AnyEvent>	830	time). This will work even when the event loop does not support blocking
367	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and	831	waits otherwise.
368	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
369	from different coroutines, however).
370		832
371	=item $cv->broadcast	833	=item $bool = $cv->ready
372		834
373	Flag the condition as ready - a running C<< ->wait >> and all further	835	Returns true when the condition is "true", i.e. whether C<send> or
374	calls to C<wait> will (eventually) return after this method has been	836	C<croak> have been called.
375	called. If nobody is waiting the broadcast will be remembered..	837
		838	=item $cb = $cv->cb ($cb->($cv))
		839
		840	This is a mutator function that returns the callback set and optionally
		841	replaces it before doing so.
		842
		843	The callback will be called when the condition becomes "true", i.e. when
		844	C<send> or C<croak> are called, with the only argument being the
		845	condition variable itself. If the condition is already true, the
		846	callback is called immediately when it is set. Calling C<recv> inside
		847	the callback or at any later time is guaranteed not to block.
376		848
377	=back	849	=back
378		850
379	Example:	851	=head1 SUPPORTED EVENT LOOPS/BACKENDS
380		852
381	# wait till the result is ready	853	The available backend classes are (every class has its own manpage):
382	my $result_ready = AnyEvent->condvar;
383		854
384	# do something such as adding a timer	855	=over 4
385	# or socket watcher the calls $result_ready->broadcast
386	# when the "result" is ready.
387	# in this case, we simply use a timer:
388	my $w = AnyEvent->timer (
389	after => 1,
390	cb => sub { $result_ready->broadcast },
391	);
392		856
393	# this "blocks" (while handling events) till the watcher	857	=item Backends that are autoprobed when no other event loop can be found.
394	# calls broadcast	858
395	$result_ready->wait;	859	EV is the preferred backend when no other event loop seems to be in
		860	use. If EV is not installed, then AnyEvent will fall back to its own
		861	pure-perl implementation, which is available everywhere as it comes with
		862	AnyEvent itself.
		863
		864	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		865	AnyEvent::Impl::Perl pure-perl AnyEvent::Loop, fast and portable.
		866
		867	=item Backends that are transparently being picked up when they are used.
		868
		869	These will be used if they are already loaded when the first watcher
		870	is created, in which case it is assumed that the application is using
		871	them. This means that AnyEvent will automatically pick the right backend
		872	when the main program loads an event module before anything starts to
		873	create watchers. Nothing special needs to be done by the main program.
		874
		875	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		876	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		877	AnyEvent::Impl::Tk based on Tk, very broken.
		878	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		879	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		880	AnyEvent::Impl::Irssi used when running within irssi.
		881	AnyEvent::Impl::IOAsync based on IO::Async.
		882	AnyEvent::Impl::Cocoa based on Cocoa::EventLoop.
		883	AnyEvent::Impl::FLTK based on FLTK (fltk 2 binding).
		884
		885	=item Backends with special needs.
		886
		887	Qt requires the Qt::Application to be instantiated first, but will
		888	otherwise be picked up automatically. As long as the main program
		889	instantiates the application before any AnyEvent watchers are created,
		890	everything should just work.
		891
		892	AnyEvent::Impl::Qt based on Qt.
		893
		894	=item Event loops that are indirectly supported via other backends.
		895
		896	Some event loops can be supported via other modules:
		897
		898	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		899
		900	B<WxWidgets> has no support for watching file handles. However, you can
		901	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		902	polls 20 times per second, which was considered to be too horrible to even
		903	consider for AnyEvent.
		904
		905	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		906	backend, so it can be supported through POE.
		907
		908	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		909	load L<POE> when detecting them, in the hope that POE will pick them up,
		910	in which case everything will be automatic.
		911
		912	=back
396		913
397	=head1 GLOBAL VARIABLES AND FUNCTIONS	914	=head1 GLOBAL VARIABLES AND FUNCTIONS
398		915
		916	These are not normally required to use AnyEvent, but can be useful to
		917	write AnyEvent extension modules.
		918
399	=over 4	919	=over 4
400		920
401	=item $AnyEvent::MODEL	921	=item $AnyEvent::MODEL
402		922
403	Contains C<undef> until the first watcher is being created. Then it	923	Contains C<undef> until the first watcher is being created, before the
		924	backend has been autodetected.
		925
404	contains the event model that is being used, which is the name of the	926	Afterwards it contains the event model that is being used, which is the
405	Perl class implementing the model. This class is usually one of the	927	name of the Perl class implementing the model. This class is usually one
406	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	928	of the C<AnyEvent::Impl::xxx> modules, but can be any other class in the
407	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	929	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
408		930	will be C<urxvt::anyevent>).
409	The known classes so far are:
410
411	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
412	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
413	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
414	AnyEvent::Impl::Event based on Event, second best choice.
415	AnyEvent::Impl::Glib based on Glib, third-best choice.
416	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
417	AnyEvent::Impl::Tk based on Tk, very bad choice.
418	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
419	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
420	AnyEvent::Impl::POE based on POE, not generic enough for full support.
421
422	There is no support for WxWidgets, as WxWidgets has no support for
423	watching file handles. However, you can use WxWidgets through the
424	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
425	second, which was considered to be too horrible to even consider for
426	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
427	it's adaptor.
428
429	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
430	autodetecting them.
431		931
432	=item AnyEvent::detect	932	=item AnyEvent::detect
433		933
434	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	934	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
435	if necessary. You should only call this function right before you would	935	if necessary. You should only call this function right before you would
436	have created an AnyEvent watcher anyway, that is, as late as possible at	936	have created an AnyEvent watcher anyway, that is, as late as possible at
437	runtime.	937	runtime, and not e.g. during initialisation of your module.
		938
		939	The effect of calling this function is as if a watcher had been created
		940	(specifically, actions that happen "when the first watcher is created"
		941	happen when calling detetc as well).
		942
		943	If you need to do some initialisation before AnyEvent watchers are
		944	created, use C<post_detect>.
		945
		946	=item $guard = AnyEvent::post_detect { BLOCK }
		947
		948	Arranges for the code block to be executed as soon as the event model is
		949	autodetected (or immediately if that has already happened).
		950
		951	The block will be executed I<after> the actual backend has been detected
		952	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		953	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		954	other initialisations - see the sources of L<AnyEvent::Strict> or
		955	L<AnyEvent::AIO> to see how this is used.
		956
		957	The most common usage is to create some global watchers, without forcing
		958	event module detection too early, for example, L<AnyEvent::AIO> creates
		959	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		960	avoid autodetecting the event module at load time.
		961
		962	If called in scalar or list context, then it creates and returns an object
		963	that automatically removes the callback again when it is destroyed (or
		964	C<undef> when the hook was immediately executed). See L<AnyEvent::AIO> for
		965	a case where this is useful.
		966
		967	Example: Create a watcher for the IO::AIO module and store it in
		968	C<$WATCHER>, but do so only do so after the event loop is initialised.
		969
		970	our WATCHER;
		971
		972	my $guard = AnyEvent::post_detect {
		973	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		974	};
		975
		976	# the ||= is important in case post_detect immediately runs the block,
		977	# as to not clobber the newly-created watcher. assigning both watcher and
		978	# post_detect guard to the same variable has the advantage of users being
		979	# able to just C<undef $WATCHER> if the watcher causes them grief.
		980
		981	$WATCHER ||= $guard;
		982
		983	=item @AnyEvent::post_detect
		984
		985	If there are any code references in this array (you can C<push> to it
		986	before or after loading AnyEvent), then they will be called directly
		987	after the event loop has been chosen.
		988
		989	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		990	if it is defined then the event loop has already been detected, and the
		991	array will be ignored.
		992
		993	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		994	it, as it takes care of these details.
		995
		996	This variable is mainly useful for modules that can do something useful
		997	when AnyEvent is used and thus want to know when it is initialised, but do
		998	not need to even load it by default. This array provides the means to hook
		999	into AnyEvent passively, without loading it.
		1000
		1001	Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used
		1002	together, you could put this into Coro (this is the actual code used by
		1003	Coro to accomplish this):
		1004
		1005	if (defined $AnyEvent::MODEL) {
		1006	# AnyEvent already initialised, so load Coro::AnyEvent
		1007	require Coro::AnyEvent;
		1008	} else {
		1009	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent
		1010	# as soon as it is
		1011	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };
		1012	}
		1013
		1014	=item AnyEvent::postpone { BLOCK }
		1015
		1016	Arranges for the block to be executed as soon as possible, but not before
		1017	the call itself returns. In practise, the block will be executed just
		1018	before the event loop polls for new events, or shortly afterwards.
		1019
		1020	This function never returns anything (to make the C<return postpone { ...
		1021	}> idiom more useful.
		1022
		1023	To understand the usefulness of this function, consider a function that
		1024	asynchronously does something for you and returns some transaction
		1025	object or guard to let you cancel the operation. For example,
		1026	C<AnyEvent::Socket::tcp_connect>:
		1027
		1028	# start a conenction attempt unless one is active
		1029	$self->{connect_guard} ||= AnyEvent::Socket::tcp_connect "www.example.net", 80, sub {
		1030	delete $self->{connect_guard};
		1031	...
		1032	};
		1033
		1034	Imagine that this function could instantly call the callback, for
		1035	example, because it detects an obvious error such as a negative port
		1036	number. Invoking the callback before the function returns causes problems
		1037	however: the callback will be called and will try to delete the guard
		1038	object. But since the function hasn't returned yet, there is nothing to
		1039	delete. When the function eventually returns it will assign the guard
		1040	object to C<< $self->{connect_guard} >>, where it will likely never be
		1041	deleted, so the program thinks it is still trying to connect.
		1042
		1043	This is where C<AnyEvent::postpone> should be used. Instead of calling the
		1044	callback directly on error:
		1045
		1046	$cb->(undef), return # signal error to callback, BAD!
		1047	if $some_error_condition;
		1048
		1049	It should use C<postpone>:
		1050
		1051	AnyEvent::postpone { $cb->(undef) }, return # signal error to callback, later
		1052	if $some_error_condition;
		1053
		1054	=item AnyEvent::log $level, $msg[, @args]
		1055
		1056	Log the given C<$msg> at the given C<$level>.
		1057
		1058	If L<AnyEvent::Log> is not loaded then this function makes a simple test
		1059	to see whether the message will be logged. If the test succeeds it will
		1060	load AnyEvent::Log and call C<AnyEvent::Log::log> - consequently, look at
		1061	the L<AnyEvent::Log> documentation for details.
		1062
		1063	If the test fails it will simply return. Right now this happens when a
		1064	numerical loglevel is used and it is larger than the level specified via
		1065	C<$ENV{PERL_ANYEVENT_VERBOSE}>.
		1066
		1067	If you want to sprinkle loads of logging calls around your code, consider
		1068	creating a logger callback with the C<AnyEvent::Log::logger> function,
		1069	which can reduce typing, codesize and can reduce the logging overhead
		1070	enourmously.
438		1071
439	=back	1072	=back
440		1073
441	=head1 WHAT TO DO IN A MODULE	1074	=head1 WHAT TO DO IN A MODULE
442		1075
…		…
446	Be careful when you create watchers in the module body - AnyEvent will	1079	Be careful when you create watchers in the module body - AnyEvent will
447	decide which event module to use as soon as the first method is called, so	1080	decide which event module to use as soon as the first method is called, so
448	by calling AnyEvent in your module body you force the user of your module	1081	by calling AnyEvent in your module body you force the user of your module
449	to load the event module first.	1082	to load the event module first.
450		1083
451	Never call C<< ->wait >> on a condition variable unless you I<know> that	1084	Never call C<< ->recv >> on a condition variable unless you I<know> that
452	the C<< ->broadcast >> method has been called on it already. This is	1085	the C<< ->send >> method has been called on it already. This is
453	because it will stall the whole program, and the whole point of using	1086	because it will stall the whole program, and the whole point of using
454	events is to stay interactive.	1087	events is to stay interactive.
455		1088
456	It is fine, however, to call C<< ->wait >> when the user of your module	1089	It is fine, however, to call C<< ->recv >> when the user of your module
457	requests it (i.e. if you create a http request object ad have a method	1090	requests it (i.e. if you create a http request object ad have a method
458	called C<results> that returns the results, it should call C<< ->wait >>	1091	called C<results> that returns the results, it may call C<< ->recv >>
459	freely, as the user of your module knows what she is doing. always).	1092	freely, as the user of your module knows what she is doing. Always).
460		1093
461	=head1 WHAT TO DO IN THE MAIN PROGRAM	1094	=head1 WHAT TO DO IN THE MAIN PROGRAM
462		1095
463	There will always be a single main program - the only place that should	1096	There will always be a single main program - the only place that should
464	dictate which event model to use.	1097	dictate which event model to use.
465		1098
466	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	1099	If the program is not event-based, it need not do anything special, even
467	do anything special (it does not need to be event-based) and let AnyEvent	1100	when it depends on a module that uses an AnyEvent. If the program itself
468	decide which implementation to chose if some module relies on it.	1101	uses AnyEvent, but does not care which event loop is used, all it needs
		1102	to do is C<use AnyEvent>. In either case, AnyEvent will choose the best
		1103	available loop implementation.
469		1104
470	If the main program relies on a specific event model. For example, in	1105	If the main program relies on a specific event model - for example, in
471	Gtk2 programs you have to rely on the Glib module. You should load the	1106	Gtk2 programs you have to rely on the Glib module - you should load the
472	event module before loading AnyEvent or any module that uses it: generally	1107	event module before loading AnyEvent or any module that uses it: generally
473	speaking, you should load it as early as possible. The reason is that	1108	speaking, you should load it as early as possible. The reason is that
474	modules might create watchers when they are loaded, and AnyEvent will	1109	modules might create watchers when they are loaded, and AnyEvent will
475	decide on the event model to use as soon as it creates watchers, and it	1110	decide on the event model to use as soon as it creates watchers, and it
476	might chose the wrong one unless you load the correct one yourself.	1111	might choose the wrong one unless you load the correct one yourself.
477		1112
478	You can chose to use a rather inefficient pure-perl implementation by	1113	You can chose to use a pure-perl implementation by loading the
479	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	1114	C<AnyEvent::Loop> module, which gives you similar behaviour
480	behaviour everywhere, but letting AnyEvent chose is generally better.	1115	everywhere, but letting AnyEvent chose the model is generally better.
		1116
		1117	=head2 MAINLOOP EMULATION
		1118
		1119	Sometimes (often for short test scripts, or even standalone programs who
		1120	only want to use AnyEvent), you do not want to run a specific event loop.
		1121
		1122	In that case, you can use a condition variable like this:
		1123
		1124	AnyEvent->condvar->recv;
		1125
		1126	This has the effect of entering the event loop and looping forever.
		1127
		1128	Note that usually your program has some exit condition, in which case
		1129	it is better to use the "traditional" approach of storing a condition
		1130	variable somewhere, waiting for it, and sending it when the program should
		1131	exit cleanly.
		1132
		1133
		1134	=head1 OTHER MODULES
		1135
		1136	The following is a non-exhaustive list of additional modules that use
		1137	AnyEvent as a client and can therefore be mixed easily with other
		1138	AnyEvent modules and other event loops in the same program. Some of the
		1139	modules come as part of AnyEvent, the others are available via CPAN (see
		1140	L<http://search.cpan.org/search?m=module&q=anyevent%3A%3A*> for
		1141	a longer non-exhaustive list), and the list is heavily biased towards
		1142	modules of the AnyEvent author himself :)
		1143
		1144	=over 4
		1145
		1146	=item L<AnyEvent::Util>
		1147
		1148	Contains various utility functions that replace often-used blocking
		1149	functions such as C<inet_aton> with event/callback-based versions.
		1150
		1151	=item L<AnyEvent::Socket>
		1152
		1153	Provides various utility functions for (internet protocol) sockets,
		1154	addresses and name resolution. Also functions to create non-blocking tcp
		1155	connections or tcp servers, with IPv6 and SRV record support and more.
		1156
		1157	=item L<AnyEvent::Handle>
		1158
		1159	Provide read and write buffers, manages watchers for reads and writes,
		1160	supports raw and formatted I/O, I/O queued and fully transparent and
		1161	non-blocking SSL/TLS (via L<AnyEvent::TLS>).
		1162
		1163	=item L<AnyEvent::DNS>
		1164
		1165	Provides rich asynchronous DNS resolver capabilities.
		1166
		1167	=item L<AnyEvent::HTTP>, L<AnyEvent::IRC>, L<AnyEvent::XMPP>, L<AnyEvent::GPSD>, L<AnyEvent::IGS>, L<AnyEvent::FCP>
		1168
		1169	Implement event-based interfaces to the protocols of the same name (for
		1170	the curious, IGS is the International Go Server and FCP is the Freenet
		1171	Client Protocol).
		1172
		1173	=item L<AnyEvent::AIO>
		1174
		1175	Truly asynchronous (as opposed to non-blocking) I/O, should be in the
		1176	toolbox of every event programmer. AnyEvent::AIO transparently fuses
		1177	L<IO::AIO> and AnyEvent together, giving AnyEvent access to event-based
		1178	file I/O, and much more.
		1179
		1180	=item L<AnyEvent::Filesys::Notify>
		1181
		1182	AnyEvent is good for non-blocking stuff, but it can't detect file or
		1183	path changes (e.g. "watch this directory for new files", "watch this
		1184	file for changes"). The L<AnyEvent::Filesys::Notify> module promises to
		1185	do just that in a portbale fashion, supporting inotify on GNU/Linux and
		1186	some weird, without doubt broken, stuff on OS X to monitor files. It can
		1187	fall back to blocking scans at regular intervals transparently on other
		1188	platforms, so it's about as portable as it gets.
		1189
		1190	(I haven't used it myself, but I haven't heard anybody complaining about
		1191	it yet).
		1192
		1193	=item L<AnyEvent::DBI>
		1194
		1195	Executes L<DBI> requests asynchronously in a proxy process for you,
		1196	notifying you in an event-based way when the operation is finished.
		1197
		1198	=item L<AnyEvent::HTTPD>
		1199
		1200	A simple embedded webserver.
		1201
		1202	=item L<AnyEvent::FastPing>
		1203
		1204	The fastest ping in the west.
		1205
		1206	=item L<Coro>
		1207
		1208	Has special support for AnyEvent via L<Coro::AnyEvent>, which allows you
		1209	to simply invert the flow control - don't call us, we will call you:
		1210
		1211	async {
		1212	Coro::AnyEvent::sleep 5; # creates a 5s timer and waits for it
		1213	print "5 seconds later!\n";
		1214
		1215	Coro::AnyEvent::readable *STDIN; # uses an I/O watcher
		1216	my $line = <STDIN>; # works for ttys
		1217
		1218	AnyEvent::HTTP::http_get "url", Coro::rouse_cb;
		1219	my ($body, $hdr) = Coro::rouse_wait;
		1220	};
		1221
		1222	=back
481		1223
482	=cut	1224	=cut
483		1225
484	package AnyEvent;	1226	package AnyEvent;
485		1227
486	no warnings;	1228	# basically a tuned-down version of common::sense
487	use strict;	1229	sub common_sense {
		1230	# from common:.sense 3.4
		1231	${^WARNING_BITS} ^= ${^WARNING_BITS} ^ "\x3c\x3f\x33\x00\x0f\xf0\x0f\xc0\xf0\xfc\x33\x00";
		1232	# use strict vars subs - NO UTF-8, as Util.pm doesn't like this atm. (uts46data.pl)
		1233	$^H |= 0x00000600;
		1234	}
488		1235
		1236	BEGIN { AnyEvent::common_sense }
		1237
489	use Carp;	1238	use Carp ();
490		1239
491	our $VERSION = '3.3';	1240	our $VERSION = '6.02';
492	our $MODEL;	1241	our $MODEL;
493
494	our $AUTOLOAD;
495	our @ISA;	1242	our @ISA;
496
497	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
498
499	our @REGISTRY;	1243	our @REGISTRY;
		1244	our $VERBOSE;
		1245	our $MAX_SIGNAL_LATENCY = 10;
		1246	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
500		1247
		1248	BEGIN {
		1249	require "AnyEvent/constants.pl";
		1250
		1251	eval "sub TAINT (){" . (${^TAINT}*1) . "}";
		1252
		1253	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1254	if ${^TAINT};
		1255
		1256	$ENV{"PERL_ANYEVENT_$_"} = $ENV{"AE_$_"}
		1257	for grep s/^AE_// && !exists $ENV{"PERL_ANYEVENT_$_"}, keys %ENV;
		1258
		1259	@ENV{grep /^PERL_ANYEVENT_/, keys %ENV} = ()
		1260	if ${^TAINT};
		1261
		1262	# $ENV{PERL_ANYEVENT_xxx} now valid
		1263
		1264	$VERBOSE = length $ENV{PERL_ANYEVENT_VERBOSE} ? $ENV{PERL_ANYEVENT_VERBOSE}*1 : 4;
		1265
		1266	my $idx;
		1267	$PROTOCOL{$_} = ++$idx
		1268	for reverse split /\s*,\s*/,
		1269	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		1270	}
		1271
		1272	our @post_detect;
		1273
		1274	sub post_detect(&) {
		1275	my ($cb) = @_;
		1276
		1277	push @post_detect, $cb;
		1278
		1279	defined wantarray
		1280	? bless \$cb, "AnyEvent::Util::postdetect"
		1281	: ()
		1282	}
		1283
		1284	sub AnyEvent::Util::postdetect::DESTROY {
		1285	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		1286	}
		1287
		1288	our $POSTPONE_W;
		1289	our @POSTPONE;
		1290
		1291	sub _postpone_exec {
		1292	undef $POSTPONE_W;
		1293
		1294	&{ shift @POSTPONE }
		1295	while @POSTPONE;
		1296	}
		1297
		1298	sub postpone(&) {
		1299	push @POSTPONE, shift;
		1300
		1301	$POSTPONE_W ||= AE::timer (0, 0, \&_postpone_exec);
		1302
		1303	()
		1304	}
		1305
		1306	sub log($$;@) {
		1307	# only load the big bloated module when we actually are about to log something
		1308	if ($_[0] <= ($VERBOSE || 1)) { # also catches non-numeric levels(!) and fatal
		1309	require AnyEvent::Log; # among other things, sets $VERBOSE to 9
		1310	# AnyEvent::Log overwrites this function
		1311	goto &log;
		1312	}
		1313
		1314	0 # not logged
		1315	}
		1316
		1317	sub logger($;$) {
		1318	package AnyEvent::Log;
		1319
		1320	my ($level, $renabled) = @_;
		1321
		1322	$$renabled = $level <= $VERBOSE;
		1323
		1324	my $pkg = (caller)[0];
		1325
		1326	my $logger = [$pkg, $level, $renabled];
		1327
		1328	our %LOGGER;
		1329	$LOGGER{$logger+0} = $logger;
		1330
		1331	require AnyEvent::Util;
		1332	my $guard = AnyEvent::Util::guard (sub {
		1333	# "clean up"
		1334	delete $LOGGER{$logger+0};
		1335	});
		1336
		1337	sub {
		1338	return 0 unless $$renabled;
		1339
		1340	$guard if 0; # keep guard alive, but don't cause runtime overhead
		1341	require AnyEvent::Log unless $AnyEvent::Log::VERSION;
		1342	package AnyEvent::Log;
		1343	_log ($logger->[0], $level, @_) # logger->[0] has been converted at load time
		1344	}
		1345	}
		1346
		1347	if (length $ENV{PERL_ANYEVENT_LOG}) {
		1348	require AnyEvent::Log; # AnyEvent::Log does the thing for us
		1349	}
		1350
501	my @models = (	1351	our @models = (
502	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
503	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
504	[EV:: => AnyEvent::Impl::EV::],	1352	[EV:: => AnyEvent::Impl::EV::],
		1353	[AnyEvent::Loop:: => AnyEvent::Impl::Perl::],
		1354	# everything below here will not (normally) be autoprobed
		1355	# as the pure perl backend should work everywhere
		1356	# and is usually faster
		1357	[Irssi:: => AnyEvent::Impl::Irssi::], # Irssi has a bogus "Event" package, so msut be near the top
505	[Event:: => AnyEvent::Impl::Event::],	1358	[Event:: => AnyEvent::Impl::Event::], # slow, stable
506	[Glib:: => AnyEvent::Impl::Glib::],	1359	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers
		1360	# everything below here should not be autoloaded
		1361	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
507	[Tk:: => AnyEvent::Impl::Tk::],	1362	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		1363	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		1364	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
508	[Wx:: => AnyEvent::Impl::POE::],	1365	[Wx:: => AnyEvent::Impl::POE::],
509	[Prima:: => AnyEvent::Impl::POE::],	1366	[Prima:: => AnyEvent::Impl::POE::],
510	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1367	[IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # a bitch to autodetect
511	# everything below here will not be autoprobed as the pureperl backend should work everywhere	1368	[Cocoa::EventLoop:: => AnyEvent::Impl::Cocoa::],
512	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy	1369	[FLTK:: => AnyEvent::Impl::FLTK::],
513	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
514	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
515	);	1370	);
516		1371
517	our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);	1372	our @isa_hook;
		1373
		1374	sub _isa_set {
		1375	my @pkg = ("AnyEvent", (map $_->[0], grep defined, @isa_hook), $MODEL);
		1376
		1377	@{"$pkg[$_-1]::ISA"} = $pkg[$_]
		1378	for 1 .. $#pkg;
		1379
		1380	grep $_ && $_->[1], @isa_hook
		1381	and AE::_reset ();
		1382	}
		1383
		1384	# used for hooking AnyEvent::Strict and AnyEvent::Debug::Wrap into the class hierarchy
		1385	sub _isa_hook($$;$) {
		1386	my ($i, $pkg, $reset_ae) = @_;
		1387
		1388	$isa_hook[$i] = $pkg ? [$pkg, $reset_ae] : undef;
		1389
		1390	_isa_set;
		1391	}
		1392
		1393	# all autoloaded methods reserve the complete glob, not just the method slot.
		1394	# due to bugs in perls method cache implementation.
		1395	our @methods = qw(io timer time now now_update signal child idle condvar);
518		1396
519	sub detect() {	1397	sub detect() {
		1398	return $MODEL if $MODEL; # some programs keep references to detect
		1399
		1400	local $!; # for good measure
		1401	local $SIG{__DIE__}; # we use eval
		1402
		1403	# free some memory
		1404	*detect = sub () { $MODEL };
		1405	# undef &func doesn't correctly update the method cache. grmbl.
		1406	# so we delete the whole glob. grmbl.
		1407	# otoh, perl doesn't let me undef an active usb, but it lets me free
		1408	# a glob with an active sub. hrm. i hope it works, but perl is
		1409	# usually buggy in this department. sigh.
		1410	delete @{"AnyEvent::"}{@methods};
		1411	undef @methods;
		1412
		1413	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z0-9:]+)$/) {
		1414	my $model = $1;
		1415	$model = "AnyEvent::Impl::$model" unless $model =~ s/::$//;
		1416	if (eval "require $model") {
		1417	AnyEvent::log 7 => "loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.";
		1418	$MODEL = $model;
		1419	} else {
		1420	AnyEvent::log 4 => "unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@";
		1421	}
		1422	}
		1423
		1424	# check for already loaded models
520	unless ($MODEL) {	1425	unless ($MODEL) {
521	no strict 'refs';	1426	for (@REGISTRY, @models) {
522		1427	my ($package, $model) = @$_;
523	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	1428	if (${"$package\::VERSION"} > 0) {
524	my $model = "AnyEvent::Impl::$1";
525	if (eval "require $model") {	1429	if (eval "require $model") {
		1430	AnyEvent::log 7 => "autodetected model '$model', using it.";
526	$MODEL = $model;	1431	$MODEL = $model;
527	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	1432	last;
528	} else {	1433	}
529	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;
530	}	1434	}
531	}	1435	}
532		1436
533	# check for already loaded models
534	unless ($MODEL) {	1437	unless ($MODEL) {
		1438	# try to autoload a model
535	for (@REGISTRY, @models) {	1439	for (@REGISTRY, @models) {
536	my ($package, $model) = @$_;	1440	my ($package, $model) = @$_;
		1441	if (
		1442	eval "require $package"
537	if (${"$package\::VERSION"} > 0) {	1443	and ${"$package\::VERSION"} > 0
538	if (eval "require $model") {	1444	and eval "require $model"
		1445	) {
		1446	AnyEvent::log 7 => "autoloaded model '$model', using it.";
539	$MODEL = $model;	1447	$MODEL = $model;
540	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;
541	last;	1448	last;
542	}
543	}	1449	}
544	}	1450	}
545		1451
546	unless ($MODEL) {	1452	$MODEL
547	# try to load a model	1453	or AnyEvent::log fatal => "AnyEvent: backend autodetection failed - did you properly install AnyEvent?";
		1454	}
		1455	}
548		1456
549	for (@REGISTRY, @models) {	1457	# free memory only needed for probing
550	my ($package, $model) = @$_;	1458	undef @models;
551	if (eval "require $package"	1459	undef @REGISTRY;
552	and ${"$package\::VERSION"} > 0	1460
553	and eval "require $model") {	1461	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
554	$MODEL = $model;	1462
555	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;	1463	# now nuke some methods that are overridden by the backend.
		1464	# SUPER usage is not allowed in these.
		1465	for (qw(time signal child idle)) {
		1466	undef &{"AnyEvent::Base::$_"}
		1467	if defined &{"$MODEL\::$_"};
		1468	}
		1469
		1470	_isa_set;
		1471
		1472	# we're officially open!
		1473
		1474	if ($ENV{PERL_ANYEVENT_STRICT}) {
		1475	require AnyEvent::Strict;
		1476	}
		1477
		1478	if ($ENV{PERL_ANYEVENT_DEBUG_WRAP}) {
		1479	require AnyEvent::Debug;
		1480	AnyEvent::Debug::wrap ($ENV{PERL_ANYEVENT_DEBUG_WRAP});
		1481	}
		1482
		1483	if (length $ENV{PERL_ANYEVENT_DEBUG_SHELL}) {
		1484	require AnyEvent::Socket;
		1485	require AnyEvent::Debug;
		1486
		1487	my $shell = $ENV{PERL_ANYEVENT_DEBUG_SHELL};
		1488	$shell =~ s/\$\$/$$/g;
		1489
		1490	my ($host, $service) = AnyEvent::Socket::parse_hostport ($shell);
		1491	$AnyEvent::Debug::SHELL = AnyEvent::Debug::shell ($host, $service);
		1492	}
		1493
		1494	# now the anyevent environment is set up as the user told us to, so
		1495	# call the actual user code - post detects
		1496
		1497	(shift @post_detect)->() while @post_detect;
		1498	undef @post_detect;
		1499
		1500	*post_detect = sub(&) {
		1501	shift->();
		1502
		1503	undef
		1504	};
		1505
		1506	$MODEL
		1507	}
		1508
		1509	for my $name (@methods) {
		1510	*$name = sub {
		1511	detect;
		1512	# we use goto because
		1513	# a) it makes the thunk more transparent
		1514	# b) it allows us to delete the thunk later
		1515	goto &{ UNIVERSAL::can AnyEvent => "SUPER::$name" }
		1516	};
		1517	}
		1518
		1519	# utility function to dup a filehandle. this is used by many backends
		1520	# to support binding more than one watcher per filehandle (they usually
		1521	# allow only one watcher per fd, so we dup it to get a different one).
		1522	sub _dupfh($$;$$) {
		1523	my ($poll, $fh, $r, $w) = @_;
		1524
		1525	# cygwin requires the fh mode to be matching, unix doesn't
		1526	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1527
		1528	open my $fh2, $mode, $fh
		1529	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1530
		1531	# we assume CLOEXEC is already set by perl in all important cases
		1532
		1533	($fh2, $rw)
		1534	}
		1535
		1536	=head1 SIMPLIFIED AE API
		1537
		1538	Starting with version 5.0, AnyEvent officially supports a second, much
		1539	simpler, API that is designed to reduce the calling, typing and memory
		1540	overhead by using function call syntax and a fixed number of parameters.
		1541
		1542	See the L<AE> manpage for details.
		1543
		1544	=cut
		1545
		1546	package AE;
		1547
		1548	our $VERSION = $AnyEvent::VERSION;
		1549
		1550	sub _reset() {
		1551	eval q{
		1552	# fall back to the main API by default - backends and AnyEvent::Base
		1553	# implementations can overwrite these.
		1554
		1555	sub io($$$) {
		1556	AnyEvent->io (fh => $_[0], poll => $_[1] ? "w" : "r", cb => $_[2])
		1557	}
		1558
		1559	sub timer($$$) {
		1560	AnyEvent->timer (after => $_[0], interval => $_[1], cb => $_[2])
		1561	}
		1562
		1563	sub signal($$) {
		1564	AnyEvent->signal (signal => $_[0], cb => $_[1])
		1565	}
		1566
		1567	sub child($$) {
		1568	AnyEvent->child (pid => $_[0], cb => $_[1])
		1569	}
		1570
		1571	sub idle($) {
		1572	AnyEvent->idle (cb => $_[0]);
		1573	}
		1574
		1575	sub cv(;&) {
		1576	AnyEvent->condvar (@_ ? (cb => $_[0]) : ())
		1577	}
		1578
		1579	sub now() {
		1580	AnyEvent->now
		1581	}
		1582
		1583	sub now_update() {
		1584	AnyEvent->now_update
		1585	}
		1586
		1587	sub time() {
		1588	AnyEvent->time
		1589	}
		1590
		1591	*postpone = \&AnyEvent::postpone;
		1592	*log = \&AnyEvent::log;
		1593	};
		1594	die if $@;
		1595	}
		1596
		1597	BEGIN { _reset }
		1598
		1599	package AnyEvent::Base;
		1600
		1601	# default implementations for many methods
		1602
		1603	sub time {
		1604	eval q{ # poor man's autoloading {}
		1605	# probe for availability of Time::HiRes
		1606	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1607	*time = sub { Time::HiRes::time () };
		1608	*AE::time = \& Time::HiRes::time ;
		1609	*now = \&time;
		1610	AnyEvent::log 8 => "AnyEvent: using Time::HiRes for sub-second timing accuracy.";
		1611	# if (eval "use POSIX (); (POSIX::times())...
		1612	} else {
		1613	*time = sub { CORE::time };
		1614	*AE::time = sub (){ CORE::time };
		1615	*now = \&time;
		1616	AnyEvent::log 3 => "using built-in time(), WARNING, no sub-second resolution!";
		1617	}
		1618	};
		1619	die if $@;
		1620
		1621	&time
		1622	}
		1623
		1624	*now = \&time;
		1625	sub now_update { }
		1626
		1627	sub _poll {
		1628	Carp::croak "$AnyEvent::MODEL does not support blocking waits. Caught";
		1629	}
		1630
		1631	# default implementation for ->condvar
		1632	# in fact, the default should not be overwritten
		1633
		1634	sub condvar {
		1635	eval q{ # poor man's autoloading {}
		1636	*condvar = sub {
		1637	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
		1638	};
		1639
		1640	*AE::cv = sub (;&) {
		1641	bless { @_ ? (_ae_cb => shift) : () }, "AnyEvent::CondVar"
		1642	};
		1643	};
		1644	die if $@;
		1645
		1646	&condvar
		1647	}
		1648
		1649	# default implementation for ->signal
		1650
		1651	our $HAVE_ASYNC_INTERRUPT;
		1652
		1653	sub _have_async_interrupt() {
		1654	$HAVE_ASYNC_INTERRUPT = 1*(!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT}
		1655	&& eval "use Async::Interrupt 1.02 (); 1")
		1656	unless defined $HAVE_ASYNC_INTERRUPT;
		1657
		1658	$HAVE_ASYNC_INTERRUPT
		1659	}
		1660
		1661	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1662	our (%SIG_ASY, %SIG_ASY_W);
		1663	our ($SIG_COUNT, $SIG_TW);
		1664
		1665	# install a dummy wakeup watcher to reduce signal catching latency
		1666	# used by Impls
		1667	sub _sig_add() {
		1668	unless ($SIG_COUNT++) {
		1669	# try to align timer on a full-second boundary, if possible
		1670	my $NOW = AE::now;
		1671
		1672	$SIG_TW = AE::timer
		1673	$MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1674	$MAX_SIGNAL_LATENCY,
		1675	sub { } # just for the PERL_ASYNC_CHECK
		1676	;
		1677	}
		1678	}
		1679
		1680	sub _sig_del {
		1681	undef $SIG_TW
		1682	unless --$SIG_COUNT;
		1683	}
		1684
		1685	our $_sig_name_init; $_sig_name_init = sub {
		1686	eval q{ # poor man's autoloading {}
		1687	undef $_sig_name_init;
		1688
		1689	if (_have_async_interrupt) {
		1690	*sig2num = \&Async::Interrupt::sig2num;
		1691	*sig2name = \&Async::Interrupt::sig2name;
		1692	} else {
		1693	require Config;
		1694
		1695	my %signame2num;
		1696	@signame2num{ split ' ', $Config::Config{sig_name} }
		1697	= split ' ', $Config::Config{sig_num};
		1698
		1699	my @signum2name;
		1700	@signum2name[values %signame2num] = keys %signame2num;
		1701
		1702	*sig2num = sub($) {
		1703	$_[0] > 0 ? shift : $signame2num{+shift}
		1704	};
		1705	*sig2name = sub ($) {
		1706	$_[0] > 0 ? $signum2name[+shift] : shift
		1707	};
		1708	}
		1709	};
		1710	die if $@;
		1711	};
		1712
		1713	sub sig2num ($) { &$_sig_name_init; &sig2num }
		1714	sub sig2name($) { &$_sig_name_init; &sig2name }
		1715
		1716	sub signal {
		1717	eval q{ # poor man's autoloading {}
		1718	# probe for availability of Async::Interrupt
		1719	if (_have_async_interrupt) {
		1720	AnyEvent::log 8 => "using Async::Interrupt for race-free signal handling.";
		1721
		1722	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1723	$SIG_IO = AE::io $SIGPIPE_R->fileno, 0, \&_signal_exec;
		1724
		1725	} else {
		1726	AnyEvent::log 8 => "using emulated perl signal handling with latency timer.";
		1727
		1728	if (AnyEvent::WIN32) {
		1729	require AnyEvent::Util;
		1730
		1731	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1732	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R, 1) if $SIGPIPE_R;
		1733	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W, 1) if $SIGPIPE_W; # just in case
		1734	} else {
		1735	pipe $SIGPIPE_R, $SIGPIPE_W;
		1736	fcntl $SIGPIPE_R, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_R;
		1737	fcntl $SIGPIPE_W, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_W; # just in case
		1738
		1739	# not strictly required, as $^F is normally 2, but let's make sure...
		1740	fcntl $SIGPIPE_R, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1741	fcntl $SIGPIPE_W, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1742	}
		1743
		1744	$SIGPIPE_R
		1745	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1746
		1747	$SIG_IO = AE::io $SIGPIPE_R, 0, \&_signal_exec;
		1748	}
		1749
		1750	*signal = $HAVE_ASYNC_INTERRUPT
		1751	? sub {
		1752	my (undef, %arg) = @_;
		1753
		1754	# async::interrupt
		1755	my $signal = sig2num $arg{signal};
		1756	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1757
		1758	$SIG_ASY{$signal} ||= new Async::Interrupt
		1759	cb => sub { undef $SIG_EV{$signal} },
		1760	signal => $signal,
		1761	pipe => [$SIGPIPE_R->filenos],
		1762	pipe_autodrain => 0,
		1763	;
		1764
		1765	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1766	}
		1767	: sub {
		1768	my (undef, %arg) = @_;
		1769
		1770	# pure perl
		1771	my $signal = sig2name $arg{signal};
		1772	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1773
		1774	$SIG{$signal} ||= sub {
556	last;	1775	local $!;
		1776	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1777	undef $SIG_EV{$signal};
557	}	1778	};
		1779
		1780	# can't do signal processing without introducing races in pure perl,
		1781	# so limit the signal latency.
		1782	_sig_add;
		1783
		1784	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1785	}
		1786	;
		1787
		1788	*AnyEvent::Base::signal::DESTROY = sub {
		1789	my ($signal, $cb) = @{$_[0]};
		1790
		1791	_sig_del;
		1792
		1793	delete $SIG_CB{$signal}{$cb};
		1794
		1795	$HAVE_ASYNC_INTERRUPT
		1796	? delete $SIG_ASY{$signal}
		1797	: # delete doesn't work with older perls - they then
		1798	# print weird messages, or just unconditionally exit
		1799	# instead of getting the default action.
		1800	undef $SIG{$signal}
		1801	unless keys %{ $SIG_CB{$signal} };
		1802	};
		1803
		1804	*_signal_exec = sub {
		1805	$HAVE_ASYNC_INTERRUPT
		1806	? $SIGPIPE_R->drain
		1807	: sysread $SIGPIPE_R, (my $dummy), 9;
		1808
		1809	while (%SIG_EV) {
		1810	for (keys %SIG_EV) {
		1811	delete $SIG_EV{$_};
		1812	&$_ for values %{ $SIG_CB{$_} || {} };
558	}	1813	}
559
560	$MODEL
561	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.";
562	}	1814	}
563	}	1815	};
564
565	unshift @ISA, $MODEL;
566	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
567	}
568
569	$MODEL
570	}
571
572	sub AUTOLOAD {
573	(my $func = $AUTOLOAD) =~ s/.*://;
574
575	$method{$func}
576	or croak "$func: not a valid method for AnyEvent objects";
577
578	detect unless $MODEL;
579
580	my $class = shift;
581	$class->$func (@_);
582	}
583
584	package AnyEvent::Base;
585
586	# default implementation for ->condvar, ->wait, ->broadcast
587
588	sub condvar {
589	bless \my $flag, "AnyEvent::Base::CondVar"
590	}
591
592	sub AnyEvent::Base::CondVar::broadcast {
593	${$_[0]}++;
594	}
595
596	sub AnyEvent::Base::CondVar::wait {
597	AnyEvent->one_event while !${$_[0]};
598	}
599
600	# default implementation for ->signal
601
602	our %SIG_CB;
603
604	sub signal {
605	my (undef, %arg) = @_;
606
607	my $signal = uc $arg{signal}
608	or Carp::croak "required option 'signal' is missing";
609
610	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
611	$SIG{$signal} ||= sub {
612	$_->() for values %{ $SIG_CB{$signal} || {} };
613	};	1816	};
		1817	die if $@;
614		1818
615	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1819	&signal
616	}
617
618	sub AnyEvent::Base::Signal::DESTROY {
619	my ($signal, $cb) = @{$_[0]};
620
621	delete $SIG_CB{$signal}{$cb};
622
623	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };
624	}	1820	}
625		1821
626	# default implementation for ->child	1822	# default implementation for ->child
627		1823
628	our %PID_CB;	1824	our %PID_CB;
629	our $CHLD_W;	1825	our $CHLD_W;
630	our $CHLD_DELAY_W;	1826	our $CHLD_DELAY_W;
631	our $PID_IDLE;
632	our $WNOHANG;
633		1827
634	sub _child_wait {	1828	# used by many Impl's
635	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1829	sub _emit_childstatus($$) {
		1830	my (undef, $rpid, $rstatus) = @_;
		1831
		1832	$_->($rpid, $rstatus)
636	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1833	for values %{ $PID_CB{$rpid} || {} },
637	(values %{ $PID_CB{0} || {} });	1834	values %{ $PID_CB{0} || {} };
		1835	}
		1836
		1837	sub child {
		1838	eval q{ # poor man's autoloading {}
		1839	*_sigchld = sub {
		1840	my $pid;
		1841
		1842	AnyEvent->_emit_childstatus ($pid, $?)
		1843	while ($pid = waitpid -1, WNOHANG) > 0;
		1844	};
		1845
		1846	*child = sub {
		1847	my (undef, %arg) = @_;
		1848
		1849	my $pid = $arg{pid};
		1850	my $cb = $arg{cb};
		1851
		1852	$PID_CB{$pid}{$cb+0} = $cb;
		1853
		1854	unless ($CHLD_W) {
		1855	$CHLD_W = AE::signal CHLD => \&_sigchld;
		1856	# child could be a zombie already, so make at least one round
		1857	&_sigchld;
		1858	}
		1859
		1860	bless [$pid, $cb+0], "AnyEvent::Base::child"
		1861	};
		1862
		1863	*AnyEvent::Base::child::DESTROY = sub {
		1864	my ($pid, $icb) = @{$_[0]};
		1865
		1866	delete $PID_CB{$pid}{$icb};
		1867	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
		1868
		1869	undef $CHLD_W unless keys %PID_CB;
		1870	};
		1871	};
		1872	die if $@;
		1873
		1874	&child
		1875	}
		1876
		1877	# idle emulation is done by simply using a timer, regardless
		1878	# of whether the process is idle or not, and not letting
		1879	# the callback use more than 50% of the time.
		1880	sub idle {
		1881	eval q{ # poor man's autoloading {}
		1882	*idle = sub {
		1883	my (undef, %arg) = @_;
		1884
		1885	my ($cb, $w, $rcb) = $arg{cb};
		1886
		1887	$rcb = sub {
		1888	if ($cb) {
		1889	$w = AE::time;
		1890	&$cb;
		1891	$w = AE::time - $w;
		1892
		1893	# never use more then 50% of the time for the idle watcher,
		1894	# within some limits
		1895	$w = 0.0001 if $w < 0.0001;
		1896	$w = 5 if $w > 5;
		1897
		1898	$w = AE::timer $w, 0, $rcb;
		1899	} else {
		1900	# clean up...
		1901	undef $w;
		1902	undef $rcb;
		1903	}
		1904	};
		1905
		1906	$w = AE::timer 0.05, 0, $rcb;
		1907
		1908	bless \\$cb, "AnyEvent::Base::idle"
		1909	};
		1910
		1911	*AnyEvent::Base::idle::DESTROY = sub {
		1912	undef $${$_[0]};
		1913	};
		1914	};
		1915	die if $@;
		1916
		1917	&idle
		1918	}
		1919
		1920	package AnyEvent::CondVar;
		1921
		1922	our @ISA = AnyEvent::CondVar::Base::;
		1923
		1924	# only to be used for subclassing
		1925	sub new {
		1926	my $class = shift;
		1927	bless AnyEvent->condvar (@_), $class
		1928	}
		1929
		1930	package AnyEvent::CondVar::Base;
		1931
		1932	#use overload
		1933	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1934	# fallback => 1;
		1935
		1936	# save 300+ kilobytes by dirtily hardcoding overloading
		1937	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1938	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1939	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1940	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1941
		1942	our $WAITING;
		1943
		1944	sub _send {
		1945	# nop
		1946	}
		1947
		1948	sub _wait {
		1949	AnyEvent->_poll until $_[0]{_ae_sent};
		1950	}
		1951
		1952	sub send {
		1953	my $cv = shift;
		1954	$cv->{_ae_sent} = [@_];
		1955	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1956	$cv->_send;
		1957	}
		1958
		1959	sub croak {
		1960	$_[0]{_ae_croak} = $_[1];
		1961	$_[0]->send;
		1962	}
		1963
		1964	sub ready {
		1965	$_[0]{_ae_sent}
		1966	}
		1967
		1968	sub recv {
		1969	unless ($_[0]{_ae_sent}) {
		1970	$WAITING
		1971	and Carp::croak "AnyEvent::CondVar: recursive blocking wait attempted";
		1972
		1973	local $WAITING = 1;
		1974	$_[0]->_wait;
638	}	1975	}
639		1976
640	undef $PID_IDLE;	1977	$_[0]{_ae_croak}
641	}	1978	and Carp::croak $_[0]{_ae_croak};
642		1979
643	sub _sigchld {	1980	wantarray
644	# make sure we deliver these changes "synchronous" with the event loop.	1981	? @{ $_[0]{_ae_sent} }
645	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {	1982	: $_[0]{_ae_sent}[0]
646	undef $CHLD_DELAY_W;
647	&_child_wait;
648	});
649	}	1983	}
650		1984
651	sub child {	1985	sub cb {
652	my (undef, %arg) = @_;	1986	my $cv = shift;
653		1987
654	defined (my $pid = $arg{pid} + 0)	1988	@_
655	or Carp::croak "required option 'pid' is missing";	1989	and $cv->{_ae_cb} = shift
		1990	and $cv->{_ae_sent}
		1991	and (delete $cv->{_ae_cb})->($cv);
656		1992
657	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1993	$cv->{_ae_cb}
658
659	unless ($WNOHANG) {
660	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;
661	}
662
663	unless ($CHLD_W) {
664	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
665	# child could be a zombie already, so make at least one round
666	&_sigchld;
667	}
668
669	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"
670	}	1994	}
671		1995
672	sub AnyEvent::Base::Child::DESTROY {	1996	sub begin {
673	my ($pid, $cb) = @{$_[0]};	1997	++$_[0]{_ae_counter};
674		1998	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
675	delete $PID_CB{$pid}{$cb};
676	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
677
678	undef $CHLD_W unless keys %PID_CB;
679	}	1999	}
		2000
		2001	sub end {
		2002	return if --$_[0]{_ae_counter};
		2003	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		2004	}
		2005
		2006	# undocumented/compatibility with pre-3.4
		2007	*broadcast = \&send;
		2008	*wait = \&recv;
		2009
		2010	=head1 ERROR AND EXCEPTION HANDLING
		2011
		2012	In general, AnyEvent does not do any error handling - it relies on the
		2013	caller to do that if required. The L<AnyEvent::Strict> module (see also
		2014	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		2015	checking of all AnyEvent methods, however, which is highly useful during
		2016	development.
		2017
		2018	As for exception handling (i.e. runtime errors and exceptions thrown while
		2019	executing a callback), this is not only highly event-loop specific, but
		2020	also not in any way wrapped by this module, as this is the job of the main
		2021	program.
		2022
		2023	The pure perl event loop simply re-throws the exception (usually
		2024	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		2025	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		2026	so on.
		2027
		2028	=head1 ENVIRONMENT VARIABLES
		2029
		2030	AnyEvent supports a number of environment variables that tune the
		2031	runtime behaviour. They are usually evaluated when AnyEvent is
		2032	loaded, initialised, or a submodule that uses them is loaded. Many of
		2033	them also cause AnyEvent to load additional modules - for example,
		2034	C<PERL_ANYEVENT_DEBUG_WRAP> causes the L<AnyEvent::Debug> module to be
		2035	loaded.
		2036
		2037	All the environment variables documented here start with
		2038	C<PERL_ANYEVENT_>, which is what AnyEvent considers its own
		2039	namespace. Other modules are encouraged (but by no means required) to use
		2040	C<PERL_ANYEVENT_SUBMODULE> if they have registered the AnyEvent::Submodule
		2041	namespace on CPAN, for any submodule. For example, L<AnyEvent::HTTP> could
		2042	be expected to use C<PERL_ANYEVENT_HTTP_PROXY> (it should not access env
		2043	variables starting with C<AE_>, see below).
		2044
		2045	All variables can also be set via the C<AE_> prefix, that is, instead
		2046	of setting C<PERL_ANYEVENT_VERBOSE> you can also set C<AE_VERBOSE>. In
		2047	case there is a clash btween anyevent and another program that uses
		2048	C<AE_something> you can set the corresponding C<PERL_ANYEVENT_something>
		2049	variable to the empty string, as those variables take precedence.
		2050
		2051	When AnyEvent is first loaded, it copies all C<AE_xxx> env variables
		2052	to their C<PERL_ANYEVENT_xxx> counterpart unless that variable already
		2053	exists. If taint mode is on, then AnyEvent will remove I<all> environment
		2054	variables starting with C<PERL_ANYEVENT_> from C<%ENV> (or replace them
		2055	with C<undef> or the empty string, if the corresaponding C<AE_> variable
		2056	is set).
		2057
		2058	The exact algorithm is currently:
		2059
		2060	1. if taint mode enabled, delete all PERL_ANYEVENT_xyz variables from %ENV
		2061	2. copy over AE_xyz to PERL_ANYEVENT_xyz unless the latter alraedy exists
		2062	3. if taint mode enabled, set all PERL_ANYEVENT_xyz variables to undef.
		2063
		2064	This ensures that child processes will not see the C<AE_> variables.
		2065
		2066	The following environment variables are currently known to AnyEvent:
		2067
		2068	=over 4
		2069
		2070	=item C<PERL_ANYEVENT_VERBOSE>
		2071
		2072	By default, AnyEvent will only log messages with loglevel C<3>
		2073	(C<critical>) or higher (see L<AnyEvent::Log>). You can set this
		2074	environment variable to a numerical loglevel to make AnyEvent more (or
		2075	less) talkative.
		2076
		2077	If you want to do more than just set the global logging level
		2078	you should have a look at C<PERL_ANYEVENT_LOG>, which allows much more
		2079	complex specifications.
		2080
		2081	When set to C<0> (C<off>), then no messages whatsoever will be logged with
		2082	the default logging settings.
		2083
		2084	When set to C<5> or higher (C<warn>), causes AnyEvent to warn about
		2085	unexpected conditions, such as not being able to load the event model
		2086	specified by C<PERL_ANYEVENT_MODEL>, or a guard callback throwing an
		2087	exception - this is the minimum recommended level.
		2088
		2089	When set to C<7> or higher (info), cause AnyEvent to report which event model it
		2090	chooses.
		2091
		2092	When set to C<8> or higher (debug), then AnyEvent will report extra information on
		2093	which optional modules it loads and how it implements certain features.
		2094
		2095	=item C<PERL_ANYEVENT_LOG>
		2096
		2097	Accepts rather complex logging specifications. For example, you could log
		2098	all C<debug> messages of some module to stderr, warnings and above to
		2099	stderr, and errors and above to syslog, with:
		2100
		2101	PERL_ANYEVENT_LOG=Some::Module=debug,+log:filter=warn,+%syslog:%syslog=error,syslog
		2102
		2103	For the rather extensive details, see L<AnyEvent::Log>.
		2104
		2105	This variable is evaluated when AnyEvent (or L<AnyEvent::Log>) is loaded,
		2106	so will take effect even before AnyEvent has initialised itself.
		2107
		2108	Note that specifying this environment variable causes the L<AnyEvent::Log>
		2109	module to be loaded, while C<PERL_ANYEVENT_VERBOSE> does not, so only
		2110	using the latter saves a few hundred kB of memory until the first message
		2111	is being logged.
		2112
		2113	=item C<PERL_ANYEVENT_STRICT>
		2114
		2115	AnyEvent does not do much argument checking by default, as thorough
		2116	argument checking is very costly. Setting this variable to a true value
		2117	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		2118	check the arguments passed to most method calls. If it finds any problems,
		2119	it will croak.
		2120
		2121	In other words, enables "strict" mode.
		2122
		2123	Unlike C<use strict> (or its modern cousin, C<< use L<common::sense>
		2124	>>, it is definitely recommended to keep it off in production. Keeping
		2125	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		2126	can be very useful, however.
		2127
		2128	=item C<PERL_ANYEVENT_DEBUG_SHELL>
		2129
		2130	If this env variable is nonempty, then its contents will be interpreted by
		2131	C<AnyEvent::Socket::parse_hostport> and C<AnyEvent::Debug::shell> (after
		2132	replacing every occurance of C<$$> by the process pid). The shell object
		2133	is saved in C<$AnyEvent::Debug::SHELL>.
		2134
		2135	This happens when the first watcher is created.
		2136
		2137	For example, to bind a debug shell on a unix domain socket in
		2138	F<< /tmp/debug<pid>.sock >>, you could use this:
		2139
		2140	PERL_ANYEVENT_DEBUG_SHELL=/tmp/debug\$\$.sock perlprog
		2141	# connect with e.g.: socat readline /tmp/debug123.sock
		2142
		2143	Or to bind to tcp port 4545 on localhost:
		2144
		2145	PERL_ANYEVENT_DEBUG_SHELL=127.0.0.1:4545 perlprog
		2146	# connect with e.g.: telnet localhost 4545
		2147
		2148	Note that creating sockets in F</tmp> or on localhost is very unsafe on
		2149	multiuser systems.
		2150
		2151	=item C<PERL_ANYEVENT_DEBUG_WRAP>
		2152
		2153	Can be set to C<0>, C<1> or C<2> and enables wrapping of all watchers for
		2154	debugging purposes. See C<AnyEvent::Debug::wrap> for details.
		2155
		2156	=item C<PERL_ANYEVENT_MODEL>
		2157
		2158	This can be used to specify the event model to be used by AnyEvent, before
		2159	auto detection and -probing kicks in.
		2160
		2161	It normally is a string consisting entirely of ASCII letters (e.g. C<EV>
		2162	or C<IOAsync>). The string C<AnyEvent::Impl::> gets prepended and the
		2163	resulting module name is loaded and - if the load was successful - used as
		2164	event model backend. If it fails to load then AnyEvent will proceed with
		2165	auto detection and -probing.
		2166
		2167	If the string ends with C<::> instead (e.g. C<AnyEvent::Impl::EV::>) then
		2168	nothing gets prepended and the module name is used as-is (hint: C<::> at
		2169	the end of a string designates a module name and quotes it appropriately).
		2170
		2171	For example, to force the pure perl model (L<AnyEvent::Loop::Perl>) you
		2172	could start your program like this:
		2173
		2174	PERL_ANYEVENT_MODEL=Perl perl ...
		2175
		2176	=item C<PERL_ANYEVENT_PROTOCOLS>
		2177
		2178	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		2179	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		2180	of auto probing).
		2181
		2182	Must be set to a comma-separated list of protocols or address families,
		2183	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		2184	used, and preference will be given to protocols mentioned earlier in the
		2185	list.
		2186
		2187	This variable can effectively be used for denial-of-service attacks
		2188	against local programs (e.g. when setuid), although the impact is likely
		2189	small, as the program has to handle conenction and other failures anyways.
		2190
		2191	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		2192	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		2193	- only support IPv4, never try to resolve or contact IPv6
		2194	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		2195	IPv6, but prefer IPv6 over IPv4.
		2196
		2197	=item C<PERL_ANYEVENT_HOSTS>
		2198
		2199	This variable, if specified, overrides the F</etc/hosts> file used by
		2200	L<AnyEvent::Socket>C<::resolve_sockaddr>, i.e. hosts aliases will be read
		2201	from that file instead.
		2202
		2203	=item C<PERL_ANYEVENT_EDNS0>
		2204
		2205	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension for
		2206	DNS. This extension is generally useful to reduce DNS traffic, especially
		2207	when DNSSEC is involved, but some (broken) firewalls drop such DNS
		2208	packets, which is why it is off by default.
		2209
		2210	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		2211	EDNS0 in its DNS requests.
		2212
		2213	=item C<PERL_ANYEVENT_MAX_FORKS>
		2214
		2215	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		2216	will create in parallel.
		2217
		2218	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		2219
		2220	The default value for the C<max_outstanding> parameter for the default DNS
		2221	resolver - this is the maximum number of parallel DNS requests that are
		2222	sent to the DNS server.
		2223
		2224	=item C<PERL_ANYEVENT_RESOLV_CONF>
		2225
		2226	The absolute path to a F<resolv.conf>-style file to use instead of
		2227	F</etc/resolv.conf> (or the OS-specific configuration) in the default
		2228	resolver, or the empty string to select the default configuration.
		2229
		2230	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		2231
		2232	When neither C<ca_file> nor C<ca_path> was specified during
		2233	L<AnyEvent::TLS> context creation, and either of these environment
		2234	variables are nonempty, they will be used to specify CA certificate
		2235	locations instead of a system-dependent default.
		2236
		2237	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		2238
		2239	When these are set to C<1>, then the respective modules are not
		2240	loaded. Mostly good for testing AnyEvent itself.
		2241
		2242	=back
680		2243
681	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	2244	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
682		2245
683	This is an advanced topic that you do not normally need to use AnyEvent in	2246	This is an advanced topic that you do not normally need to use AnyEvent in
684	a module. This section is only of use to event loop authors who want to	2247	a module. This section is only of use to event loop authors who want to
…		…
718		2281
719	I<rxvt-unicode> also cheats a bit by not providing blocking access to	2282	I<rxvt-unicode> also cheats a bit by not providing blocking access to
720	condition variables: code blocking while waiting for a condition will	2283	condition variables: code blocking while waiting for a condition will
721	C<die>. This still works with most modules/usages, and blocking calls must	2284	C<die>. This still works with most modules/usages, and blocking calls must
722	not be done in an interactive application, so it makes sense.	2285	not be done in an interactive application, so it makes sense.
723
724	=head1 ENVIRONMENT VARIABLES
725
726	The following environment variables are used by this module:
727
728	=over 4
729
730	=item C<PERL_ANYEVENT_VERBOSE>
731
732	By default, AnyEvent will be completely silent except in fatal
733	conditions. You can set this environment variable to make AnyEvent more
734	talkative.
735
736	When set to C<1> or higher, causes AnyEvent to warn about unexpected
737	conditions, such as not being able to load the event model specified by
738	C<PERL_ANYEVENT_MODEL>.
739
740	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
741	model it chooses.
742
743	=item C<PERL_ANYEVENT_MODEL>
744
745	This can be used to specify the event model to be used by AnyEvent, before
746	autodetection and -probing kicks in. It must be a string consisting
747	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
748	and the resulting module name is loaded and if the load was successful,
749	used as event model. If it fails to load AnyEvent will proceed with
750	autodetection and -probing.
751
752	This functionality might change in future versions.
753
754	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
755	could start your program like this:
756
757	PERL_ANYEVENT_MODEL=Perl perl ...
758
759	=back
760		2286
761	=head1 EXAMPLE PROGRAM	2287	=head1 EXAMPLE PROGRAM
762		2288
763	The following program uses an I/O watcher to read data from STDIN, a timer	2289	The following program uses an I/O watcher to read data from STDIN, a timer
764	to display a message once per second, and a condition variable to quit the	2290	to display a message once per second, and a condition variable to quit the
…		…
773	poll => 'r',	2299	poll => 'r',
774	cb => sub {	2300	cb => sub {
775	warn "io event <$_[0]>\n"; # will always output <r>	2301	warn "io event <$_[0]>\n"; # will always output <r>
776	chomp (my $input = <STDIN>); # read a line	2302	chomp (my $input = <STDIN>); # read a line
777	warn "read: $input\n"; # output what has been read	2303	warn "read: $input\n"; # output what has been read
778	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	2304	$cv->send if $input =~ /^q/i; # quit program if /^q/i
779	},	2305	},
780	);	2306	);
781		2307
782	my $time_watcher; # can only be used once
783
784	sub new_timer {
785	$timer = AnyEvent->timer (after => 1, cb => sub {	2308	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
786	warn "timeout\n"; # print 'timeout' about every second	2309	warn "timeout\n"; # print 'timeout' at most every second
787	&new_timer; # and restart the time
788	});	2310	});
789	}
790		2311
791	new_timer; # create first timer
792
793	$cv->wait; # wait until user enters /^q/i	2312	$cv->recv; # wait until user enters /^q/i
794		2313
795	=head1 REAL-WORLD EXAMPLE	2314	=head1 REAL-WORLD EXAMPLE
796		2315
797	Consider the L<Net::FCP> module. It features (among others) the following	2316	Consider the L<Net::FCP> module. It features (among others) the following
798	API calls, which are to freenet what HTTP GET requests are to http:	2317	API calls, which are to freenet what HTTP GET requests are to http:
…		…
848	syswrite $txn->{fh}, $txn->{request}	2367	syswrite $txn->{fh}, $txn->{request}
849	or die "connection or write error";	2368	or die "connection or write error";
850	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	2369	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
851		2370
852	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	2371	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
853	result and signals any possible waiters that the request ahs finished:	2372	result and signals any possible waiters that the request has finished:
854		2373
855	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	2374	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
856		2375
857	if (end-of-file or data complete) {	2376	if (end-of-file or data complete) {
858	$txn->{result} = $txn->{buf};	2377	$txn->{result} = $txn->{buf};
859	$txn->{finished}->broadcast;	2378	$txn->{finished}->send;
860	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	2379	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
861	}	2380	}
862		2381
863	The C<result> method, finally, just waits for the finished signal (if the	2382	The C<result> method, finally, just waits for the finished signal (if the
864	request was already finished, it doesn't wait, of course, and returns the	2383	request was already finished, it doesn't wait, of course, and returns the
865	data:	2384	data:
866		2385
867	$txn->{finished}->wait;	2386	$txn->{finished}->recv;
868	return $txn->{result};	2387	return $txn->{result};
869		2388
870	The actual code goes further and collects all errors (C<die>s, exceptions)	2389	The actual code goes further and collects all errors (C<die>s, exceptions)
871	that occured during request processing. The C<result> method detects	2390	that occurred during request processing. The C<result> method detects
872	whether an exception as thrown (it is stored inside the $txn object)	2391	whether an exception as thrown (it is stored inside the $txn object)
873	and just throws the exception, which means connection errors and other	2392	and just throws the exception, which means connection errors and other
874	problems get reported tot he code that tries to use the result, not in a	2393	problems get reported to the code that tries to use the result, not in a
875	random callback.	2394	random callback.
876		2395
877	All of this enables the following usage styles:	2396	All of this enables the following usage styles:
878		2397
879	1. Blocking:	2398	1. Blocking:
…		…
907		2426
908	my $quit = AnyEvent->condvar;	2427	my $quit = AnyEvent->condvar;
909		2428
910	$fcp->txn_client_get ($url)->cb (sub {	2429	$fcp->txn_client_get ($url)->cb (sub {
911	...	2430	...
912	$quit->broadcast;	2431	$quit->send;
913	});	2432	});
914		2433
915	$quit->wait;	2434	$quit->recv;
916		2435
917		2436
918	=head1 BENCHMARKS	2437	=head1 BENCHMARKS
919		2438
920	To give you an idea of the performance and overheads that AnyEvent adds	2439	To give you an idea of the performance and overheads that AnyEvent adds
…		…
922	of various event loops I prepared some benchmarks.	2441	of various event loops I prepared some benchmarks.
923		2442
924	=head2 BENCHMARKING ANYEVENT OVERHEAD	2443	=head2 BENCHMARKING ANYEVENT OVERHEAD
925		2444
926	Here is a benchmark of various supported event models used natively and	2445	Here is a benchmark of various supported event models used natively and
927	through anyevent. The benchmark creates a lot of timers (with a zero	2446	through AnyEvent. The benchmark creates a lot of timers (with a zero
928	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,	2447	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
929	which it is), lets them fire exactly once and destroys them again.	2448	which it is), lets them fire exactly once and destroys them again.
930		2449
931	Source code for this benchmark is found as F<eg/bench> in the AnyEvent	2450	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
932	distribution.	2451	distribution. It uses the L<AE> interface, which makes a real difference
		2452	for the EV and Perl backends only.
933		2453
934	=head3 Explanation of the columns	2454	=head3 Explanation of the columns
935		2455
936	I<watcher> is the number of event watchers created/destroyed. Since	2456	I<watcher> is the number of event watchers created/destroyed. Since
937	different event models feature vastly different performances, each event	2457	different event models feature vastly different performances, each event
…		…
949	all watchers, to avoid adding memory overhead. That means closure creation	2469	all watchers, to avoid adding memory overhead. That means closure creation
950	and memory usage is not included in the figures.	2470	and memory usage is not included in the figures.
951		2471
952	I<invoke> is the time, in microseconds, used to invoke a simple	2472	I<invoke> is the time, in microseconds, used to invoke a simple
953	callback. The callback simply counts down a Perl variable and after it was	2473	callback. The callback simply counts down a Perl variable and after it was
954	invoked "watcher" times, it would C<< ->broadcast >> a condvar once to	2474	invoked "watcher" times, it would C<< ->send >> a condvar once to
955	signal the end of this phase.	2475	signal the end of this phase.
956		2476
957	I<destroy> is the time, in microseconds, that it takes to destroy a single	2477	I<destroy> is the time, in microseconds, that it takes to destroy a single
958	watcher.	2478	watcher.
959		2479
960	=head3 Results	2480	=head3 Results
961		2481
962	name watchers bytes create invoke destroy comment	2482	name watchers bytes create invoke destroy comment
963	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	2483	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
964	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	2484	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
965	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	2485	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
966	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	2486	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
967	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	2487	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
968	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers	2488	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
		2489	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
		2490	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
969	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	2491	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
970	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	2492	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
971	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	2493	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
972	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	2494	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
973		2495
974	=head3 Discussion	2496	=head3 Discussion
975		2497
976	The benchmark does I<not> measure scalability of the event loop very	2498	The benchmark does I<not> measure scalability of the event loop very
977	well. For example, a select-based event loop (such as the pure perl one)	2499	well. For example, a select-based event loop (such as the pure perl one)
…		…
989	benchmark machine, handling an event takes roughly 1600 CPU cycles with	2511	benchmark machine, handling an event takes roughly 1600 CPU cycles with
990	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU	2512	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
991	cycles with POE.	2513	cycles with POE.
992		2514
993	C<EV> is the sole leader regarding speed and memory use, which are both	2515	C<EV> is the sole leader regarding speed and memory use, which are both
994	maximal/minimal, respectively. Even when going through AnyEvent, it uses	2516	maximal/minimal, respectively. When using the L<AE> API there is zero
		2517	overhead (when going through the AnyEvent API create is about 5-6 times
		2518	slower, with other times being equal, so still uses far less memory than
995	far less memory than any other event loop and is still faster than Event	2519	any other event loop and is still faster than Event natively).
996	natively.
997		2520
998	The pure perl implementation is hit in a few sweet spots (both the	2521	The pure perl implementation is hit in a few sweet spots (both the
999	constant timeout and the use of a single fd hit optimisations in the perl	2522	constant timeout and the use of a single fd hit optimisations in the perl
1000	interpreter and the backend itself). Nevertheless this shows that it	2523	interpreter and the backend itself). Nevertheless this shows that it
1001	adds very little overhead in itself. Like any select-based backend its	2524	adds very little overhead in itself. Like any select-based backend its
1002	performance becomes really bad with lots of file descriptors (and few of	2525	performance becomes really bad with lots of file descriptors (and few of
1003	them active), of course, but this was not subject of this benchmark.	2526	them active), of course, but this was not subject of this benchmark.
1004		2527
1005	The C<Event> module has a relatively high setup and callback invocation	2528	The C<Event> module has a relatively high setup and callback invocation
1006	cost, but overall scores in on the third place.	2529	cost, but overall scores in on the third place.
		2530
		2531	C<IO::Async> performs admirably well, about on par with C<Event>, even
		2532	when using its pure perl backend.
1007		2533
1008	C<Glib>'s memory usage is quite a bit higher, but it features a	2534	C<Glib>'s memory usage is quite a bit higher, but it features a
1009	faster callback invocation and overall ends up in the same class as	2535	faster callback invocation and overall ends up in the same class as
1010	C<Event>. However, Glib scales extremely badly, doubling the number of	2536	C<Event>. However, Glib scales extremely badly, doubling the number of
1011	watchers increases the processing time by more than a factor of four,	2537	watchers increases the processing time by more than a factor of four,
…		…
1019	file descriptor is dup()ed for each watcher. This shows that the dup()	2545	file descriptor is dup()ed for each watcher. This shows that the dup()
1020	employed by some adaptors is not a big performance issue (it does incur a	2546	employed by some adaptors is not a big performance issue (it does incur a
1021	hidden memory cost inside the kernel which is not reflected in the figures	2547	hidden memory cost inside the kernel which is not reflected in the figures
1022	above).	2548	above).
1023		2549
1024	C<POE>, regardless of underlying event loop (whether using its pure	2550	C<POE>, regardless of underlying event loop (whether using its pure perl
1025	perl select-based backend or the Event module, the POE-EV backend	2551	select-based backend or the Event module, the POE-EV backend couldn't
1026	couldn't be tested because it wasn't working) shows abysmal performance	2552	be tested because it wasn't working) shows abysmal performance and
1027	and memory usage: Watchers use almost 30 times as much memory as	2553	memory usage with AnyEvent: Watchers use almost 30 times as much memory
1028	EV watchers, and 10 times as much memory as Event (the high memory	2554	as EV watchers, and 10 times as much memory as Event (the high memory
1029	requirements are caused by requiring a session for each watcher). Watcher	2555	requirements are caused by requiring a session for each watcher). Watcher
1030	invocation speed is almost 900 times slower than with AnyEvent's pure perl	2556	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		2557	implementation.
		2558
1031	implementation. The design of the POE adaptor class in AnyEvent can not	2559	The design of the POE adaptor class in AnyEvent can not really account
1032	really account for this, as session creation overhead is small compared	2560	for the performance issues, though, as session creation overhead is
1033	to execution of the state machine, which is coded pretty optimally within	2561	small compared to execution of the state machine, which is coded pretty
1034	L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow.	2562	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		2563	using multiple sessions is not a good approach, especially regarding
		2564	memory usage, even the author of POE could not come up with a faster
		2565	design).
1035		2566
1036	=head3 Summary	2567	=head3 Summary
1037		2568
1038	=over 4	2569	=over 4
1039		2570
…		…
1041	(even when used without AnyEvent), but most event loops have acceptable	2572	(even when used without AnyEvent), but most event loops have acceptable
1042	performance with or without AnyEvent.	2573	performance with or without AnyEvent.
1043		2574
1044	=item * The overhead AnyEvent adds is usually much smaller than the overhead of	2575	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
1045	the actual event loop, only with extremely fast event loops such as EV	2576	the actual event loop, only with extremely fast event loops such as EV
1046	adds AnyEvent significant overhead.	2577	does AnyEvent add significant overhead.
1047		2578
1048	=item * You should avoid POE like the plague if you want performance or	2579	=item * You should avoid POE like the plague if you want performance or
1049	reasonable memory usage.	2580	reasonable memory usage.
1050		2581
1051	=back	2582	=back
1052		2583
1053	=head2 BENCHMARKING THE LARGE SERVER CASE	2584	=head2 BENCHMARKING THE LARGE SERVER CASE
1054		2585
1055	This benchmark atcually benchmarks the event loop itself. It works by	2586	This benchmark actually benchmarks the event loop itself. It works by
1056	creating a number of "servers": each server consists of a socketpair, a	2587	creating a number of "servers": each server consists of a socket pair, a
1057	timeout watcher that gets reset on activity (but never fires), and an I/O	2588	timeout watcher that gets reset on activity (but never fires), and an I/O
1058	watcher waiting for input on one side of the socket. Each time the socket	2589	watcher waiting for input on one side of the socket. Each time the socket
1059	watcher reads a byte it will write that byte to a random other "server".	2590	watcher reads a byte it will write that byte to a random other "server".
1060		2591
1061	The effect is that there will be a lot of I/O watchers, only part of which	2592	The effect is that there will be a lot of I/O watchers, only part of which
1062	are active at any one point (so there is a constant number of active	2593	are active at any one point (so there is a constant number of active
1063	fds for each loop iterstaion, but which fds these are is random). The	2594	fds for each loop iteration, but which fds these are is random). The
1064	timeout is reset each time something is read because that reflects how	2595	timeout is reset each time something is read because that reflects how
1065	most timeouts work (and puts extra pressure on the event loops).	2596	most timeouts work (and puts extra pressure on the event loops).
1066		2597
1067	In this benchmark, we use 10000 socketpairs (20000 sockets), of which 100	2598	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
1068	(1%) are active. This mirrors the activity of large servers with many	2599	(1%) are active. This mirrors the activity of large servers with many
1069	connections, most of which are idle at any one point in time.	2600	connections, most of which are idle at any one point in time.
1070		2601
1071	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent	2602	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
1072	distribution.	2603	distribution. It uses the L<AE> interface, which makes a real difference
		2604	for the EV and Perl backends only.
1073		2605
1074	=head3 Explanation of the columns	2606	=head3 Explanation of the columns
1075		2607
1076	I<sockets> is the number of sockets, and twice the number of "servers" (as	2608	I<sockets> is the number of sockets, and twice the number of "servers" (as
1077	each server has a read and write socket end).	2609	each server has a read and write socket end).
1078		2610
1079	I<create> is the time it takes to create a socketpair (which is	2611	I<create> is the time it takes to create a socket pair (which is
1080	nontrivial) and two watchers: an I/O watcher and a timeout watcher.	2612	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
1081		2613
1082	I<request>, the most important value, is the time it takes to handle a	2614	I<request>, the most important value, is the time it takes to handle a
1083	single "request", that is, reading the token from the pipe and forwarding	2615	single "request", that is, reading the token from the pipe and forwarding
1084	it to another server. This includes deleting the old timeout and creating	2616	it to another server. This includes deleting the old timeout and creating
1085	a new one that moves the timeout into the future.	2617	a new one that moves the timeout into the future.
1086		2618
1087	=head3 Results	2619	=head3 Results
1088		2620
1089	name sockets create request	2621	name sockets create request
1090	EV 20000 69.01 11.16	2622	EV 20000 62.66 7.99
1091	Perl 20000 75.28 112.76	2623	Perl 20000 68.32 32.64
1092	Event 20000 212.62 257.32	2624	IOAsync 20000 174.06 101.15 epoll
1093	Glib 20000 651.16 1896.30	2625	IOAsync 20000 174.67 610.84 poll
		2626	Event 20000 202.69 242.91
		2627	Glib 20000 557.01 1689.52
1094	POE 20000 349.67 12317.24 uses POE::Loop::Event	2628	POE 20000 341.54 12086.32 uses POE::Loop::Event
1095		2629
1096	=head3 Discussion	2630	=head3 Discussion
1097		2631
1098	This benchmark I<does> measure scalability and overall performance of the	2632	This benchmark I<does> measure scalability and overall performance of the
1099	particular event loop.	2633	particular event loop.
…		…
1101	EV is again fastest. Since it is using epoll on my system, the setup time	2635	EV is again fastest. Since it is using epoll on my system, the setup time
1102	is relatively high, though.	2636	is relatively high, though.
1103		2637
1104	Perl surprisingly comes second. It is much faster than the C-based event	2638	Perl surprisingly comes second. It is much faster than the C-based event
1105	loops Event and Glib.	2639	loops Event and Glib.
		2640
		2641	IO::Async performs very well when using its epoll backend, and still quite
		2642	good compared to Glib when using its pure perl backend.
1106		2643
1107	Event suffers from high setup time as well (look at its code and you will	2644	Event suffers from high setup time as well (look at its code and you will
1108	understand why). Callback invocation also has a high overhead compared to	2645	understand why). Callback invocation also has a high overhead compared to
1109	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event	2646	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
1110	uses select or poll in basically all documented configurations.	2647	uses select or poll in basically all documented configurations.
…		…
1118		2655
1119	=head3 Summary	2656	=head3 Summary
1120		2657
1121	=over 4	2658	=over 4
1122		2659
1123	=item * The pure perl implementation performs extremely well, considering	2660	=item * The pure perl implementation performs extremely well.
1124	that it uses select.
1125		2661
1126	=item * Avoid Glib or POE in large projects where performance matters.	2662	=item * Avoid Glib or POE in large projects where performance matters.
1127		2663
1128	=back	2664	=back
1129		2665
…		…
1142		2678
1143	=head3 Results	2679	=head3 Results
1144		2680
1145	name sockets create request	2681	name sockets create request
1146	EV 16 20.00 6.54	2682	EV 16 20.00 6.54
		2683	Perl 16 25.75 12.62
1147	Event 16 81.27 35.86	2684	Event 16 81.27 35.86
1148	Glib 16 32.63 15.48	2685	Glib 16 32.63 15.48
1149	Perl 16 24.62 162.37
1150	POE 16 261.87 276.28 uses POE::Loop::Event	2686	POE 16 261.87 276.28 uses POE::Loop::Event
1151		2687
1152	=head3 Discussion	2688	=head3 Discussion
1153		2689
1154	The benchmark tries to test the performance of a typical small	2690	The benchmark tries to test the performance of a typical small
…		…
1158	speed most when you have lots of watchers, not when you only have a few of	2694	speed most when you have lots of watchers, not when you only have a few of
1159	them).	2695	them).
1160		2696
1161	EV is again fastest.	2697	EV is again fastest.
1162		2698
1163	The C-based event loops Event and Glib come in second this time, as the	2699	Perl again comes second. It is noticeably faster than the C-based event
1164	overhead of running an iteration is much smaller in C than in Perl (little	2700	loops Event and Glib, although the difference is too small to really
1165	code to execute in the inner loop, and perl's function calling overhead is	2701	matter.
1166	high, and updating all the data structures is costly).
1167
1168	The pure perl event loop is much slower, but still competitive.
1169		2702
1170	POE also performs much better in this case, but is is still far behind the	2703	POE also performs much better in this case, but is is still far behind the
1171	others.	2704	others.
1172		2705
1173	=head3 Summary	2706	=head3 Summary
…		…
1177	=item * C-based event loops perform very well with small number of	2710	=item * C-based event loops perform very well with small number of
1178	watchers, as the management overhead dominates.	2711	watchers, as the management overhead dominates.
1179		2712
1180	=back	2713	=back
1181		2714
		2715	=head2 THE IO::Lambda BENCHMARK
		2716
		2717	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2718	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2719	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2720	shouldn't come as a surprise to anybody). As such, the benchmark is
		2721	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2722	very optimal. But how would AnyEvent compare when used without the extra
		2723	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2724
		2725	The benchmark itself creates an echo-server, and then, for 500 times,
		2726	connects to the echo server, sends a line, waits for the reply, and then
		2727	creates the next connection. This is a rather bad benchmark, as it doesn't
		2728	test the efficiency of the framework or much non-blocking I/O, but it is a
		2729	benchmark nevertheless.
		2730
		2731	name runtime
		2732	Lambda/select 0.330 sec
		2733	+ optimized 0.122 sec
		2734	Lambda/AnyEvent 0.327 sec
		2735	+ optimized 0.138 sec
		2736	Raw sockets/select 0.077 sec
		2737	POE/select, components 0.662 sec
		2738	POE/select, raw sockets 0.226 sec
		2739	POE/select, optimized 0.404 sec
		2740
		2741	AnyEvent/select/nb 0.085 sec
		2742	AnyEvent/EV/nb 0.068 sec
		2743	+state machine 0.134 sec
		2744
		2745	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2746	benchmarks actually make blocking connects and use 100% blocking I/O,
		2747	defeating the purpose of an event-based solution. All of the newly
		2748	written AnyEvent benchmarks use 100% non-blocking connects (using
		2749	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2750	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2751	generally require a lot more bookkeeping and event handling than blocking
		2752	connects (which involve a single syscall only).
		2753
		2754	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2755	offers similar expressive power as POE and IO::Lambda, using conventional
		2756	Perl syntax. This means that both the echo server and the client are 100%
		2757	non-blocking, further placing it at a disadvantage.
		2758
		2759	As you can see, the AnyEvent + EV combination even beats the
		2760	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2761	backend easily beats IO::Lambda and POE.
		2762
		2763	And even the 100% non-blocking version written using the high-level (and
		2764	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda
		2765	higher level ("unoptimised") abstractions by a large margin, even though
		2766	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
		2767
		2768	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2769	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2770	part of the IO::Lambda distribution and were used without any changes.
		2771
		2772
		2773	=head1 SIGNALS
		2774
		2775	AnyEvent currently installs handlers for these signals:
		2776
		2777	=over 4
		2778
		2779	=item SIGCHLD
		2780
		2781	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2782	emulation for event loops that do not support them natively. Also, some
		2783	event loops install a similar handler.
		2784
		2785	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2786	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2787
		2788	=item SIGPIPE
		2789
		2790	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2791	when AnyEvent gets loaded.
		2792
		2793	The rationale for this is that AnyEvent users usually do not really depend
		2794	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2795	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2796	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2797	some random socket.
		2798
		2799	The rationale for installing a no-op handler as opposed to ignoring it is
		2800	that this way, the handler will be restored to defaults on exec.
		2801
		2802	Feel free to install your own handler, or reset it to defaults.
		2803
		2804	=back
		2805
		2806	=cut
		2807
		2808	undef $SIG{CHLD}
		2809	if $SIG{CHLD} eq 'IGNORE';
		2810
		2811	$SIG{PIPE} = sub { }
		2812	unless defined $SIG{PIPE};
		2813
		2814	=head1 RECOMMENDED/OPTIONAL MODULES
		2815
		2816	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2817	its built-in modules) are required to use it.
		2818
		2819	That does not mean that AnyEvent won't take advantage of some additional
		2820	modules if they are installed.
		2821
		2822	This section explains which additional modules will be used, and how they
		2823	affect AnyEvent's operation.
		2824
		2825	=over 4
		2826
		2827	=item L<Async::Interrupt>
		2828
		2829	This slightly arcane module is used to implement fast signal handling: To
		2830	my knowledge, there is no way to do completely race-free and quick
		2831	signal handling in pure perl. To ensure that signals still get
		2832	delivered, AnyEvent will start an interval timer to wake up perl (and
		2833	catch the signals) with some delay (default is 10 seconds, look for
		2834	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2835
		2836	If this module is available, then it will be used to implement signal
		2837	catching, which means that signals will not be delayed, and the event loop
		2838	will not be interrupted regularly, which is more efficient (and good for
		2839	battery life on laptops).
		2840
		2841	This affects not just the pure-perl event loop, but also other event loops
		2842	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2843
		2844	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2845	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2846	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2847	does nothing for those backends.
		2848
		2849	=item L<EV>
		2850
		2851	This module isn't really "optional", as it is simply one of the backend
		2852	event loops that AnyEvent can use. However, it is simply the best event
		2853	loop available in terms of features, speed and stability: It supports
		2854	the AnyEvent API optimally, implements all the watcher types in XS, does
		2855	automatic timer adjustments even when no monotonic clock is available,
		2856	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2857	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2858	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2859
		2860	If you only use backends that rely on another event loop (e.g. C<Tk>),
		2861	then this module will do nothing for you.
		2862
		2863	=item L<Guard>
		2864
		2865	The guard module, when used, will be used to implement
		2866	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2867	lot less memory), but otherwise doesn't affect guard operation much. It is
		2868	purely used for performance.
		2869
		2870	=item L<JSON> and L<JSON::XS>
		2871
		2872	One of these modules is required when you want to read or write JSON data
		2873	via L<AnyEvent::Handle>. L<JSON> is also written in pure-perl, but can take
		2874	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2875
		2876	=item L<Net::SSLeay>
		2877
		2878	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2879	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2880	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2881
		2882	=item L<Time::HiRes>
		2883
		2884	This module is part of perl since release 5.008. It will be used when the
		2885	chosen event library does not come with a timing source of its own. The
		2886	pure-perl event loop (L<AnyEvent::Loop>) will additionally load it to
		2887	try to use a monotonic clock for timing stability.
		2888
		2889	=back
		2890
1182		2891
1183	=head1 FORK	2892	=head1 FORK
1184		2893
1185	Most event libraries are not fork-safe. The ones who are usually are	2894	Most event libraries are not fork-safe. The ones who are usually are
1186	because they are so inefficient. Only L<EV> is fully fork-aware.	2895	because they rely on inefficient but fork-safe C<select> or C<poll> calls
		2896	- higher performance APIs such as BSD's kqueue or the dreaded Linux epoll
		2897	are usually badly thought-out hacks that are incompatible with fork in
		2898	one way or another. Only L<EV> is fully fork-aware and ensures that you
		2899	continue event-processing in both parent and child (or both, if you know
		2900	what you are doing).
		2901
		2902	This means that, in general, you cannot fork and do event processing in
		2903	the child if the event library was initialised before the fork (which
		2904	usually happens when the first AnyEvent watcher is created, or the library
		2905	is loaded).
1187		2906
1188	If you have to fork, you must either do so I<before> creating your first	2907	If you have to fork, you must either do so I<before> creating your first
1189	watcher OR you must not use AnyEvent at all in the child.	2908	watcher OR you must not use AnyEvent at all in the child OR you must do
		2909	something completely out of the scope of AnyEvent.
		2910
		2911	The problem of doing event processing in the parent I<and> the child
		2912	is much more complicated: even for backends that I<are> fork-aware or
		2913	fork-safe, their behaviour is not usually what you want: fork clones all
		2914	watchers, that means all timers, I/O watchers etc. are active in both
		2915	parent and child, which is almost never what you want. USing C<exec>
		2916	to start worker children from some kind of manage rprocess is usually
		2917	preferred, because it is much easier and cleaner, at the expense of having
		2918	to have another binary.
1190		2919
1191		2920
1192	=head1 SECURITY CONSIDERATIONS	2921	=head1 SECURITY CONSIDERATIONS
1193		2922
1194	AnyEvent can be forced to load any event model via	2923	AnyEvent can be forced to load any event model via
…		…
1199	specified in the variable.	2928	specified in the variable.
1200		2929
1201	You can make AnyEvent completely ignore this variable by deleting it	2930	You can make AnyEvent completely ignore this variable by deleting it
1202	before the first watcher gets created, e.g. with a C<BEGIN> block:	2931	before the first watcher gets created, e.g. with a C<BEGIN> block:
1203		2932
1204	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	2933	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1205		2934
1206	use AnyEvent;	2935	use AnyEvent;
		2936
		2937	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		2938	be used to probe what backend is used and gain other information (which is
		2939	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2940	$ENV{PERL_ANYEVENT_STRICT}.
		2941
		2942	Note that AnyEvent will remove I<all> environment variables starting with
		2943	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2944	enabled.
		2945
		2946
		2947	=head1 BUGS
		2948
		2949	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2950	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2951	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2952	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2953	pronounced).
1207		2954
1208		2955
1209	=head1 SEE ALSO	2956	=head1 SEE ALSO
1210		2957
1211	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	2958	Tutorial/Introduction: L<AnyEvent::Intro>.
1212	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,
1213	L<Event::Lib>, L<Qt>, L<POE>.
1214		2959
1215	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	2960	FAQ: L<AnyEvent::FAQ>.
		2961
		2962	Utility functions: L<AnyEvent::Util> (misc. grab-bag), L<AnyEvent::Log>
		2963	(simply logging).
		2964
		2965	Development/Debugging: L<AnyEvent::Strict> (stricter checking),
		2966	L<AnyEvent::Debug> (interactive shell, watcher tracing).
		2967
		2968	Supported event modules: L<AnyEvent::Loop>, L<EV>, L<EV::Glib>,
		2969	L<Glib::EV>, L<Event>, L<Glib::Event>, L<Glib>, L<Tk>, L<Event::Lib>,
		2970	L<Qt>, L<POE>, L<FLTK>.
		2971
		2972	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
		2973	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
		2974	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1216	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,	2975	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>, L<Anyevent::Impl::Irssi>,
1217	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,	2976	L<AnyEvent::Impl::FLTK>.
1218	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.
1219		2977
		2978	Non-blocking handles, pipes, stream sockets, TCP clients and
		2979	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
		2980
		2981	Asynchronous DNS: L<AnyEvent::DNS>.
		2982
		2983	Thread support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
		2984
1220	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	2985	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::IRC>,
		2986	L<AnyEvent::HTTP>.
1221		2987
1222		2988
1223	=head1 AUTHOR	2989	=head1 AUTHOR
1224		2990
1225	Marc Lehmann <schmorp@schmorp.de>	2991	Marc Lehmann <schmorp@schmorp.de>
1226	http://home.schmorp.de/	2992	http://home.schmorp.de/
1227		2993
1228	=cut	2994	=cut
1229		2995
1230	1	2996	1
1231		2997

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