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Revision 1.408 by root, Thu Dec 6 12:04:23 2012 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent - provide framework for multiple event loops	3	AnyEvent - the DBI of event loop programming
4		4
5	EV, Event, Coro::EV, Coro::Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event loops	5	EV, Event, Glib, Tk, Perl, Event::Lib, Irssi, rxvt-unicode, IO::Async, Qt,
		6	FLTK and POE are various supported event loops/environments.
6		7
7	=head1 SYNOPSIS	8	=head1 SYNOPSIS
8		9
9	use AnyEvent;	10	use AnyEvent;
10		11
		12	# if you prefer function calls, look at the AE manpage for
		13	# an alternative API.
		14
		15	# file handle or descriptor readable
11	my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub {	16	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
		17
		18	# one-shot or repeating timers
		19	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
		20	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...);
		21
		22	print AnyEvent->now; # prints current event loop time
		23	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
		24
		25	# POSIX signal
		26	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
		27
		28	# child process exit
		29	my $w = AnyEvent->child (pid => $pid, cb => sub {
		30	my ($pid, $status) = @_;
12	...	31	...
13	});	32	});
14		33
15	my $w = AnyEvent->timer (after => $seconds, cb => sub {	34	# called when event loop idle (if applicable)
16	...	35	my $w = AnyEvent->idle (cb => sub { ... });
17	});
18		36
19	my $w = AnyEvent->condvar; # stores whether a condition was flagged	37	my $w = AnyEvent->condvar; # stores whether a condition was flagged
		38	$w->send; # wake up current and all future recv's
20	$w->wait; # enters "main loop" till $condvar gets ->broadcast	39	$w->recv; # enters "main loop" till $condvar gets ->send
21	$w->broadcast; # wake up current and all future wait's	40	# use a condvar in callback mode:
		41	$w->cb (sub { $_[0]->recv });
		42
		43	=head1 INTRODUCTION/TUTORIAL
		44
		45	This manpage is mainly a reference manual. If you are interested
		46	in a tutorial or some gentle introduction, have a look at the
		47	L<AnyEvent::Intro> manpage.
		48
		49	=head1 SUPPORT
		50
		51	An FAQ document is available as L<AnyEvent::FAQ>.
		52
		53	There also is a mailinglist for discussing all things AnyEvent, and an IRC
		54	channel, too.
		55
		56	See the AnyEvent project page at the B<Schmorpforge Ta-Sa Software
		57	Repository>, at L<http://anyevent.schmorp.de>, for more info.
22		58
23	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)	59	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
24		60
25	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	61	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
26	nowadays. So what is different about AnyEvent?	62	nowadays. So what is different about AnyEvent?
27		63
28	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of	64	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
29	policy> and AnyEvent is I<small and efficient>.	65	policy> and AnyEvent is I<small and efficient>.
30		66
31	First and foremost, I<AnyEvent is not an event model> itself, it only	67	First and foremost, I<AnyEvent is not an event model> itself, it only
32	interfaces to whatever event model the main program happens to use in a	68	interfaces to whatever event model the main program happens to use, in a
33	pragmatic way. For event models and certain classes of immortals alike,	69	pragmatic way. For event models and certain classes of immortals alike,
34	the statement "there can only be one" is a bitter reality: In general,	70	the statement "there can only be one" is a bitter reality: In general,
35	only one event loop can be active at the same time in a process. AnyEvent	71	only one event loop can be active at the same time in a process. AnyEvent
36	helps hiding the differences between those event loops.	72	cannot change this, but it can hide the differences between those event
		73	loops.
37		74
38	The goal of AnyEvent is to offer module authors the ability to do event	75	The goal of AnyEvent is to offer module authors the ability to do event
39	programming (waiting for I/O or timer events) without subscribing to a	76	programming (waiting for I/O or timer events) without subscribing to a
40	religion, a way of living, and most importantly: without forcing your	77	religion, a way of living, and most importantly: without forcing your
41	module users into the same thing by forcing them to use the same event	78	module users into the same thing by forcing them to use the same event
42	model you use.	79	model you use.
43		80
44	For modules like POE or IO::Async (which is a total misnomer as it is	81	For modules like POE or IO::Async (which is a total misnomer as it is
45	actually doing all I/O I<synchronously>...), using them in your module is	82	actually doing all I/O I<synchronously>...), using them in your module is
46	like joining a cult: After you joined, you are dependent on them and you	83	like joining a cult: After you join, you are dependent on them and you
47	cannot use anything else, as it is simply incompatible to everything that	84	cannot use anything else, as they are simply incompatible to everything
48	isn't itself. What's worse, all the potential users of your module are	85	that isn't them. What's worse, all the potential users of your
49	I<also> forced to use the same event loop you use.	86	module are I<also> forced to use the same event loop you use.
50		87
51	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	88	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
52	fine. AnyEvent + Tk works fine etc. etc. but none of these work together	89	fine. AnyEvent + Tk works fine etc. etc. but none of these work together
53	with the rest: POE + IO::Async? no go. Tk + Event? no go. Again: if	90	with the rest: POE + EV? No go. Tk + Event? No go. Again: if your module
54	your module uses one of those, every user of your module has to use it,	91	uses one of those, every user of your module has to use it, too. But if
55	too. But if your module uses AnyEvent, it works transparently with all	92	your module uses AnyEvent, it works transparently with all event models it
56	event models it supports (including stuff like POE and IO::Async, as long	93	supports (including stuff like IO::Async, as long as those use one of the
57	as those use one of the supported event loops. It is trivial to add new	94	supported event loops. It is easy to add new event loops to AnyEvent, too,
58	event loops to AnyEvent, too, so it is future-proof).	95	so it is future-proof).
59		96
60	In addition to being free of having to use I<the one and only true event	97	In addition to being free of having to use I<the one and only true event
61	model>, AnyEvent also is free of bloat and policy: with POE or similar	98	model>, AnyEvent also is free of bloat and policy: with POE or similar
62	modules, you get an enourmous amount of code and strict rules you have to	99	modules, you get an enormous amount of code and strict rules you have to
63	follow. AnyEvent, on the other hand, is lean and up to the point, by only	100	follow. AnyEvent, on the other hand, is lean and to the point, by only
64	offering the functionality that is necessary, in as thin as a wrapper as	101	offering the functionality that is necessary, in as thin as a wrapper as
65	technically possible.	102	technically possible.
66		103
		104	Of course, AnyEvent comes with a big (and fully optional!) toolbox
		105	of useful functionality, such as an asynchronous DNS resolver, 100%
		106	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
		107	such as Windows) and lots of real-world knowledge and workarounds for
		108	platform bugs and differences.
		109
67	Of course, if you want lots of policy (this can arguably be somewhat	110	Now, if you I<do want> lots of policy (this can arguably be somewhat
68	useful) and you want to force your users to use the one and only event	111	useful) and you want to force your users to use the one and only event
69	model, you should I<not> use this module.	112	model, you should I<not> use this module.
70		113
71
72	=head1 DESCRIPTION	114	=head1 DESCRIPTION
73		115
74	L<AnyEvent> provides an identical interface to multiple event loops. This	116	L<AnyEvent> provides a uniform interface to various event loops. This
75	allows module authors to utilise an event loop without forcing module	117	allows module authors to use event loop functionality without forcing
76	users to use the same event loop (as only a single event loop can coexist	118	module users to use a specific event loop implementation (since more
77	peacefully at any one time).	119	than one event loop cannot coexist peacefully).
78		120
79	The interface itself is vaguely similar, but not identical to the L<Event>	121	The interface itself is vaguely similar, but not identical to the L<Event>
80	module.	122	module.
81		123
82	During the first call of any watcher-creation method, the module tries	124	During the first call of any watcher-creation method, the module tries
83	to detect the currently loaded event loop by probing whether one of the	125	to detect the currently loaded event loop by probing whether one of the
84	following modules is already loaded: L<Coro::EV>, L<Coro::Event>, L<EV>,	126	following modules is already loaded: L<EV>, L<AnyEvent::Loop>,
85	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,	127	L<Event>, L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>. The first one
86	L<POE>. The first one found is used. If none are found, the module tries	128	found is used. If none are detected, the module tries to load the first
87	to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl	129	four modules in the order given; but note that if L<EV> is not
88	adaptor should always succeed) in the order given. The first one that can	130	available, the pure-perl L<AnyEvent::Loop> should always work, so
89	be successfully loaded will be used. If, after this, still none could be	131	the other two are not normally tried.
90	found, AnyEvent will fall back to a pure-perl event loop, which is not
91	very efficient, but should work everywhere.
92		132
93	Because AnyEvent first checks for modules that are already loaded, loading	133	Because AnyEvent first checks for modules that are already loaded, loading
94	an event model explicitly before first using AnyEvent will likely make	134	an event model explicitly before first using AnyEvent will likely make
95	that model the default. For example:	135	that model the default. For example:
96		136
…		…
98	use AnyEvent;	138	use AnyEvent;
99		139
100	# .. AnyEvent will likely default to Tk	140	# .. AnyEvent will likely default to Tk
101		141
102	The I<likely> means that, if any module loads another event model and	142	The I<likely> means that, if any module loads another event model and
103	starts using it, all bets are off. Maybe you should tell their authors to	143	starts using it, all bets are off - this case should be very rare though,
104	use AnyEvent so their modules work together with others seamlessly...	144	as very few modules hardcode event loops without announcing this very
		145	loudly.
105		146
106	The pure-perl implementation of AnyEvent is called	147	The pure-perl implementation of AnyEvent is called C<AnyEvent::Loop>. Like
107	C<AnyEvent::Impl::Perl>. Like other event modules you can load it	148	other event modules you can load it explicitly and enjoy the high
108	explicitly.	149	availability of that event loop :)
109		150
110	=head1 WATCHERS	151	=head1 WATCHERS
111		152
112	AnyEvent has the central concept of a I<watcher>, which is an object that	153	AnyEvent has the central concept of a I<watcher>, which is an object that
113	stores relevant data for each kind of event you are waiting for, such as	154	stores relevant data for each kind of event you are waiting for, such as
114	the callback to call, the filehandle to watch, etc.	155	the callback to call, the file handle to watch, etc.
115		156
116	These watchers are normal Perl objects with normal Perl lifetime. After	157	These watchers are normal Perl objects with normal Perl lifetime. After
117	creating a watcher it will immediately "watch" for events and invoke the	158	creating a watcher it will immediately "watch" for events and invoke the
118	callback when the event occurs (of course, only when the event model	159	callback when the event occurs (of course, only when the event model
119	is in control).	160	is in control).
120		161
		162	Note that B<callbacks must not permanently change global variables>
		163	potentially in use by the event loop (such as C<$_> or C<$[>) and that B<<
		164	callbacks must not C<die> >>. The former is good programming practice in
		165	Perl and the latter stems from the fact that exception handling differs
		166	widely between event loops.
		167
121	To disable the watcher you have to destroy it (e.g. by setting the	168	To disable a watcher you have to destroy it (e.g. by setting the
122	variable you store it in to C<undef> or otherwise deleting all references	169	variable you store it in to C<undef> or otherwise deleting all references
123	to it).	170	to it).
124		171
125	All watchers are created by calling a method on the C<AnyEvent> class.	172	All watchers are created by calling a method on the C<AnyEvent> class.
126		173
127	Many watchers either are used with "recursion" (repeating timers for	174	Many watchers either are used with "recursion" (repeating timers for
128	example), or need to refer to their watcher object in other ways.	175	example), or need to refer to their watcher object in other ways.
129		176
130	An any way to achieve that is this pattern:	177	One way to achieve that is this pattern:
131		178
132	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	179	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
133	# you can use $w here, for example to undef it	180	# you can use $w here, for example to undef it
134	undef $w;	181	undef $w;
135	});	182	});
136		183
137	Note that C<my $w; $w => combination. This is necessary because in Perl,	184	Note that C<my $w; $w => combination. This is necessary because in Perl,
138	my variables are only visible after the statement in which they are	185	my variables are only visible after the statement in which they are
139	declared.	186	declared.
140		187
141	=head2 I/O WATCHERS	188	=head2 I/O WATCHERS
142		189
		190	$w = AnyEvent->io (
		191	fh => <filehandle_or_fileno>,
		192	poll => <"r" or "w">,
		193	cb => <callback>,
		194	);
		195
143	You can create an I/O watcher by calling the C<< AnyEvent->io >> method	196	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
144	with the following mandatory key-value pairs as arguments:	197	with the following mandatory key-value pairs as arguments:
145		198
146	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch	199	C<fh> is the Perl I<file handle> (or a naked file descriptor) to watch
		200	for events (AnyEvent might or might not keep a reference to this file
		201	handle). Note that only file handles pointing to things for which
		202	non-blocking operation makes sense are allowed. This includes sockets,
		203	most character devices, pipes, fifos and so on, but not for example files
		204	or block devices.
		205
147	for events. C<poll> must be a string that is either C<r> or C<w>,	206	C<poll> must be a string that is either C<r> or C<w>, which creates a
148	which creates a watcher waiting for "r"eadable or "w"ritable events,	207	watcher waiting for "r"eadable or "w"ritable events, respectively.
		208
149	respectively. C<cb> is the callback to invoke each time the file handle	209	C<cb> is the callback to invoke each time the file handle becomes ready.
150	becomes ready.
151		210
152	Although the callback might get passed parameters, their value and	211	Although the callback might get passed parameters, their value and
153	presence is undefined and you cannot rely on them. Portable AnyEvent	212	presence is undefined and you cannot rely on them. Portable AnyEvent
154	callbacks cannot use arguments passed to I/O watcher callbacks.	213	callbacks cannot use arguments passed to I/O watcher callbacks.
155		214
156	The I/O watcher might use the underlying file descriptor or a copy of it.	215	The I/O watcher might use the underlying file descriptor or a copy of it.
157	You must not close a file handle as long as any watcher is active on the	216	You must not close a file handle as long as any watcher is active on the
158	underlying file descriptor.	217	underlying file descriptor.
159		218
160	Some event loops issue spurious readyness notifications, so you should	219	Some event loops issue spurious readiness notifications, so you should
161	always use non-blocking calls when reading/writing from/to your file	220	always use non-blocking calls when reading/writing from/to your file
162	handles.	221	handles.
163		222
164	Example:
165
166	# wait for readability of STDIN, then read a line and disable the watcher	223	Example: wait for readability of STDIN, then read a line and disable the
		224	watcher.
		225
167	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	226	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
168	chomp (my $input = <STDIN>);	227	chomp (my $input = <STDIN>);
169	warn "read: $input\n";	228	warn "read: $input\n";
170	undef $w;	229	undef $w;
171	});	230	});
172		231
173	=head2 TIME WATCHERS	232	=head2 TIME WATCHERS
174		233
		234	$w = AnyEvent->timer (after => <seconds>, cb => <callback>);
		235
		236	$w = AnyEvent->timer (
		237	after => <fractional_seconds>,
		238	interval => <fractional_seconds>,
		239	cb => <callback>,
		240	);
		241
175	You can create a time watcher by calling the C<< AnyEvent->timer >>	242	You can create a time watcher by calling the C<< AnyEvent->timer >>
176	method with the following mandatory arguments:	243	method with the following mandatory arguments:
177		244
178	C<after> specifies after how many seconds (fractional values are	245	C<after> specifies after how many seconds (fractional values are
179	supported) the callback should be invoked. C<cb> is the callback to invoke	246	supported) the callback should be invoked. C<cb> is the callback to invoke
…		…
181		248
182	Although the callback might get passed parameters, their value and	249	Although the callback might get passed parameters, their value and
183	presence is undefined and you cannot rely on them. Portable AnyEvent	250	presence is undefined and you cannot rely on them. Portable AnyEvent
184	callbacks cannot use arguments passed to time watcher callbacks.	251	callbacks cannot use arguments passed to time watcher callbacks.
185		252
186	The timer callback will be invoked at most once: if you want a repeating	253	The callback will normally be invoked only once. If you specify another
187	timer you have to create a new watcher (this is a limitation by both Tk	254	parameter, C<interval>, as a strictly positive number (> 0), then the
188	and Glib).	255	callback will be invoked regularly at that interval (in fractional
		256	seconds) after the first invocation. If C<interval> is specified with a
		257	false value, then it is treated as if it were not specified at all.
189		258
190	Example:	259	The callback will be rescheduled before invoking the callback, but no
		260	attempt is made to avoid timer drift in most backends, so the interval is
		261	only approximate.
191		262
192	# fire an event after 7.7 seconds	263	Example: fire an event after 7.7 seconds.
		264
193	my $w = AnyEvent->timer (after => 7.7, cb => sub {	265	my $w = AnyEvent->timer (after => 7.7, cb => sub {
194	warn "timeout\n";	266	warn "timeout\n";
195	});	267	});
196		268
197	# to cancel the timer:	269	# to cancel the timer:
198	undef $w;	270	undef $w;
199		271
200	Example 2:
201
202	# fire an event after 0.5 seconds, then roughly every second	272	Example 2: fire an event after 0.5 seconds, then roughly every second.
203	my $w;
204		273
205	my $cb = sub {
206	# cancel the old timer while creating a new one
207	$w = AnyEvent->timer (after => 1, cb => $cb);	274	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		275	warn "timeout\n";
208	};	276	};
209
210	# start the "loop" by creating the first watcher
211	$w = AnyEvent->timer (after => 0.5, cb => $cb);
212		277
213	=head3 TIMING ISSUES	278	=head3 TIMING ISSUES
214		279
215	There are two ways to handle timers: based on real time (relative, "fire	280	There are two ways to handle timers: based on real time (relative, "fire
216	in 10 seconds") and based on wallclock time (absolute, "fire at 12	281	in 10 seconds") and based on wallclock time (absolute, "fire at 12
…		…
218		283
219	While most event loops expect timers to specified in a relative way, they	284	While most event loops expect timers to specified in a relative way, they
220	use absolute time internally. This makes a difference when your clock	285	use absolute time internally. This makes a difference when your clock
221	"jumps", for example, when ntp decides to set your clock backwards from	286	"jumps", for example, when ntp decides to set your clock backwards from
222	the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to	287	the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to
223	fire "after" a second might actually take six years to finally fire.	288	fire "after a second" might actually take six years to finally fire.
224		289
225	AnyEvent cannot compensate for this. The only event loop that is conscious	290	AnyEvent cannot compensate for this. The only event loop that is conscious
226	about these issues is L<EV>, which offers both relative (ev_timer, based	291	of these issues is L<EV>, which offers both relative (ev_timer, based
227	on true relative time) and absolute (ev_periodic, based on wallclock time)	292	on true relative time) and absolute (ev_periodic, based on wallclock time)
228	timers.	293	timers.
229		294
230	AnyEvent always prefers relative timers, if available, matching the	295	AnyEvent always prefers relative timers, if available, matching the
231	AnyEvent API.	296	AnyEvent API.
232		297
		298	AnyEvent has two additional methods that return the "current time":
		299
		300	=over 4
		301
		302	=item AnyEvent->time
		303
		304	This returns the "current wallclock time" as a fractional number of
		305	seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
		306	return, and the result is guaranteed to be compatible with those).
		307
		308	It progresses independently of any event loop processing, i.e. each call
		309	will check the system clock, which usually gets updated frequently.
		310
		311	=item AnyEvent->now
		312
		313	This also returns the "current wallclock time", but unlike C<time>, above,
		314	this value might change only once per event loop iteration, depending on
		315	the event loop (most return the same time as C<time>, above). This is the
		316	time that AnyEvent's timers get scheduled against.
		317
		318	I<In almost all cases (in all cases if you don't care), this is the
		319	function to call when you want to know the current time.>
		320
		321	This function is also often faster then C<< AnyEvent->time >>, and
		322	thus the preferred method if you want some timestamp (for example,
		323	L<AnyEvent::Handle> uses this to update its activity timeouts).
		324
		325	The rest of this section is only of relevance if you try to be very exact
		326	with your timing; you can skip it without a bad conscience.
		327
		328	For a practical example of when these times differ, consider L<Event::Lib>
		329	and L<EV> and the following set-up:
		330
		331	The event loop is running and has just invoked one of your callbacks at
		332	time=500 (assume no other callbacks delay processing). In your callback,
		333	you wait a second by executing C<sleep 1> (blocking the process for a
		334	second) and then (at time=501) you create a relative timer that fires
		335	after three seconds.
		336
		337	With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
		338	both return C<501>, because that is the current time, and the timer will
		339	be scheduled to fire at time=504 (C<501> + C<3>).
		340
		341	With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
		342	time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
		343	last event processing phase started. With L<EV>, your timer gets scheduled
		344	to run at time=503 (C<500> + C<3>).
		345
		346	In one sense, L<Event::Lib> is more exact, as it uses the current time
		347	regardless of any delays introduced by event processing. However, most
		348	callbacks do not expect large delays in processing, so this causes a
		349	higher drift (and a lot more system calls to get the current time).
		350
		351	In another sense, L<EV> is more exact, as your timer will be scheduled at
		352	the same time, regardless of how long event processing actually took.
		353
		354	In either case, if you care (and in most cases, you don't), then you
		355	can get whatever behaviour you want with any event loop, by taking the
		356	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
		357	account.
		358
		359	=item AnyEvent->now_update
		360
		361	Some event loops (such as L<EV> or L<AnyEvent::Loop>) cache the current
		362	time for each loop iteration (see the discussion of L<< AnyEvent->now >>,
		363	above).
		364
		365	When a callback runs for a long time (or when the process sleeps), then
		366	this "current" time will differ substantially from the real time, which
		367	might affect timers and time-outs.
		368
		369	When this is the case, you can call this method, which will update the
		370	event loop's idea of "current time".
		371
		372	A typical example would be a script in a web server (e.g. C<mod_perl>) -
		373	when mod_perl executes the script, then the event loop will have the wrong
		374	idea about the "current time" (being potentially far in the past, when the
		375	script ran the last time). In that case you should arrange a call to C<<
		376	AnyEvent->now_update >> each time the web server process wakes up again
		377	(e.g. at the start of your script, or in a handler).
		378
		379	Note that updating the time I<might> cause some events to be handled.
		380
		381	=back
		382
233	=head2 SIGNAL WATCHERS	383	=head2 SIGNAL WATCHERS
234		384
		385	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		386
235	You can watch for signals using a signal watcher, C<signal> is the signal	387	You can watch for signals using a signal watcher, C<signal> is the signal
236	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to	388	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
237	be invoked whenever a signal occurs.	389	callback to be invoked whenever a signal occurs.
238		390
239	Although the callback might get passed parameters, their value and	391	Although the callback might get passed parameters, their value and
240	presence is undefined and you cannot rely on them. Portable AnyEvent	392	presence is undefined and you cannot rely on them. Portable AnyEvent
241	callbacks cannot use arguments passed to signal watcher callbacks.	393	callbacks cannot use arguments passed to signal watcher callbacks.
242		394
243	Multiple signal occurances can be clumped together into one callback	395	Multiple signal occurrences can be clumped together into one callback
244	invocation, and callback invocation will be synchronous. synchronous means	396	invocation, and callback invocation will be synchronous. Synchronous means
245	that it might take a while until the signal gets handled by the process,	397	that it might take a while until the signal gets handled by the process,
246	but it is guarenteed not to interrupt any other callbacks.	398	but it is guaranteed not to interrupt any other callbacks.
247		399
248	The main advantage of using these watchers is that you can share a signal	400	The main advantage of using these watchers is that you can share a signal
249	between multiple watchers.	401	between multiple watchers, and AnyEvent will ensure that signals will not
		402	interrupt your program at bad times.
250		403
251	This watcher might use C<%SIG>, so programs overwriting those signals	404	This watcher might use C<%SIG> (depending on the event loop used),
252	directly will likely not work correctly.	405	so programs overwriting those signals directly will likely not work
		406	correctly.
253		407
254	Example: exit on SIGINT	408	Example: exit on SIGINT
255		409
256	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	410	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
257		411
		412	=head3 Restart Behaviour
		413
		414	While restart behaviour is up to the event loop implementation, most will
		415	not restart syscalls (that includes L<Async::Interrupt> and AnyEvent's
		416	pure perl implementation).
		417
		418	=head3 Safe/Unsafe Signals
		419
		420	Perl signals can be either "safe" (synchronous to opcode handling)
		421	or "unsafe" (asynchronous) - the former might delay signal delivery
		422	indefinitely, the latter might corrupt your memory.
		423
		424	AnyEvent signal handlers are, in addition, synchronous to the event loop,
		425	i.e. they will not interrupt your running perl program but will only be
		426	called as part of the normal event handling (just like timer, I/O etc.
		427	callbacks, too).
		428
		429	=head3 Signal Races, Delays and Workarounds
		430
		431	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support
		432	attaching callbacks to signals in a generic way, which is a pity,
		433	as you cannot do race-free signal handling in perl, requiring
		434	C libraries for this. AnyEvent will try to do its best, which
		435	means in some cases, signals will be delayed. The maximum time
		436	a signal might be delayed is 10 seconds by default, but can
		437	be overriden via C<$ENV{PERL_ANYEVENT_MAX_SIGNAL_LATENCY}> or
		438	C<$AnyEvent::MAX_SIGNAL_LATENCY> - see the L<ENVIRONMENT VARIABLES>
		439	section for details.
		440
		441	All these problems can be avoided by installing the optional
		442	L<Async::Interrupt> module, which works with most event loops. It will not
		443	work with inherently broken event loops such as L<Event> or L<Event::Lib>
		444	(and not with L<POE> currently). For those, you just have to suffer the
		445	delays.
		446
258	=head2 CHILD PROCESS WATCHERS	447	=head2 CHILD PROCESS WATCHERS
259		448
		449	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		450
260	You can also watch on a child process exit and catch its exit status.	451	You can also watch for a child process exit and catch its exit status.
261		452
262	The child process is specified by the C<pid> argument (if set to C<0>, it	453	The child process is specified by the C<pid> argument (on some backends,
263	watches for any child process exit). The watcher will trigger as often	454	using C<0> watches for any child process exit, on others this will
264	as status change for the child are received. This works by installing a	455	croak). The watcher will be triggered only when the child process has
265	signal handler for C<SIGCHLD>. The callback will be called with the pid	456	finished and an exit status is available, not on any trace events
266	and exit status (as returned by waitpid), so unlike other watcher types,	457	(stopped/continued).
267	you I<can> rely on child watcher callback arguments.	458
		459	The callback will be called with the pid and exit status (as returned by
		460	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		461	callback arguments.
		462
		463	This watcher type works by installing a signal handler for C<SIGCHLD>,
		464	and since it cannot be shared, nothing else should use SIGCHLD or reap
		465	random child processes (waiting for specific child processes, e.g. inside
		466	C<system>, is just fine).
268		467
269	There is a slight catch to child watchers, however: you usually start them	468	There is a slight catch to child watchers, however: you usually start them
270	I<after> the child process was created, and this means the process could	469	I<after> the child process was created, and this means the process could
271	have exited already (and no SIGCHLD will be sent anymore).	470	have exited already (and no SIGCHLD will be sent anymore).
272		471
273	Not all event models handle this correctly (POE doesn't), but even for	472	Not all event models handle this correctly (neither POE nor IO::Async do,
		473	see their AnyEvent::Impl manpages for details), but even for event models
274	event models that I<do> handle this correctly, they usually need to be	474	that I<do> handle this correctly, they usually need to be loaded before
275	loaded before the process exits (i.e. before you fork in the first place).	475	the process exits (i.e. before you fork in the first place). AnyEvent's
		476	pure perl event loop handles all cases correctly regardless of when you
		477	start the watcher.
276		478
277	This means you cannot create a child watcher as the very first thing in an	479	This means you cannot create a child watcher as the very first
278	AnyEvent program, you I<have> to create at least one watcher before you	480	thing in an AnyEvent program, you I<have> to create at least one
279	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).	481	watcher before you C<fork> the child (alternatively, you can call
		482	C<AnyEvent::detect>).
		483
		484	As most event loops do not support waiting for child events, they will be
		485	emulated by AnyEvent in most cases, in which case the latency and race
		486	problems mentioned in the description of signal watchers apply.
280		487
281	Example: fork a process and wait for it	488	Example: fork a process and wait for it
282		489
283	my $done = AnyEvent->condvar;	490	my $done = AnyEvent->condvar;
284		491
285	AnyEvent::detect; # force event module to be initialised
286
287	my $pid = fork or exit 5;	492	my $pid = fork or exit 5;
288		493
289	my $w = AnyEvent->child (	494	my $w = AnyEvent->child (
290	pid => $pid,	495	pid => $pid,
291	cb => sub {	496	cb => sub {
292	my ($pid, $status) = @_;	497	my ($pid, $status) = @_;
293	warn "pid $pid exited with status $status";	498	warn "pid $pid exited with status $status";
294	$done->broadcast;	499	$done->send;
295	},	500	},
296	);	501	);
297		502
298	# do something else, then wait for process exit	503	# do something else, then wait for process exit
299	$done->wait;	504	$done->recv;
		505
		506	=head2 IDLE WATCHERS
		507
		508	$w = AnyEvent->idle (cb => <callback>);
		509
		510	This will repeatedly invoke the callback after the process becomes idle,
		511	until either the watcher is destroyed or new events have been detected.
		512
		513	Idle watchers are useful when there is a need to do something, but it
		514	is not so important (or wise) to do it instantly. The callback will be
		515	invoked only when there is "nothing better to do", which is usually
		516	defined as "all outstanding events have been handled and no new events
		517	have been detected". That means that idle watchers ideally get invoked
		518	when the event loop has just polled for new events but none have been
		519	detected. Instead of blocking to wait for more events, the idle watchers
		520	will be invoked.
		521
		522	Unfortunately, most event loops do not really support idle watchers (only
		523	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		524	will simply call the callback "from time to time".
		525
		526	Example: read lines from STDIN, but only process them when the
		527	program is otherwise idle:
		528
		529	my @lines; # read data
		530	my $idle_w;
		531	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		532	push @lines, scalar <STDIN>;
		533
		534	# start an idle watcher, if not already done
		535	$idle_w ||= AnyEvent->idle (cb => sub {
		536	# handle only one line, when there are lines left
		537	if (my $line = shift @lines) {
		538	print "handled when idle: $line";
		539	} else {
		540	# otherwise disable the idle watcher again
		541	undef $idle_w;
		542	}
		543	});
		544	});
300		545
301	=head2 CONDITION VARIABLES	546	=head2 CONDITION VARIABLES
302		547
		548	$cv = AnyEvent->condvar;
		549
		550	$cv->send (<list>);
		551	my @res = $cv->recv;
		552
		553	If you are familiar with some event loops you will know that all of them
		554	require you to run some blocking "loop", "run" or similar function that
		555	will actively watch for new events and call your callbacks.
		556
		557	AnyEvent is slightly different: it expects somebody else to run the event
		558	loop and will only block when necessary (usually when told by the user).
		559
		560	The tool to do that is called a "condition variable", so called because
		561	they represent a condition that must become true.
		562
		563	Now is probably a good time to look at the examples further below.
		564
303	Condition variables can be created by calling the C<< AnyEvent->condvar >>	565	Condition variables can be created by calling the C<< AnyEvent->condvar
304	method without any arguments.	566	>> method, usually without arguments. The only argument pair allowed is
		567	C<cb>, which specifies a callback to be called when the condition variable
		568	becomes true, with the condition variable as the first argument (but not
		569	the results).
305		570
306	A condition variable waits for a condition - precisely that the C<<	571	After creation, the condition variable is "false" until it becomes "true"
307	->broadcast >> method has been called.	572	by calling the C<send> method (or calling the condition variable as if it
		573	were a callback, read about the caveats in the description for the C<<
		574	->send >> method).
308		575
309	They are very useful to signal that a condition has been fulfilled, for	576	Since condition variables are the most complex part of the AnyEvent API, here are
		577	some different mental models of what they are - pick the ones you can connect to:
		578
		579	=over 4
		580
		581	=item * Condition variables are like callbacks - you can call them (and pass them instead
		582	of callbacks). Unlike callbacks however, you can also wait for them to be called.
		583
		584	=item * Condition variables are signals - one side can emit or send them,
		585	the other side can wait for them, or install a handler that is called when
		586	the signal fires.
		587
		588	=item * Condition variables are like "Merge Points" - points in your program
		589	where you merge multiple independent results/control flows into one.
		590
		591	=item * Condition variables represent a transaction - functions that start
		592	some kind of transaction can return them, leaving the caller the choice
		593	between waiting in a blocking fashion, or setting a callback.
		594
		595	=item * Condition variables represent future values, or promises to deliver
		596	some result, long before the result is available.
		597
		598	=back
		599
		600	Condition variables are very useful to signal that something has finished,
310	example, if you write a module that does asynchronous http requests,	601	for example, if you write a module that does asynchronous http requests,
311	then a condition variable would be the ideal candidate to signal the	602	then a condition variable would be the ideal candidate to signal the
312	availability of results.	603	availability of results. The user can either act when the callback is
		604	called or can synchronously C<< ->recv >> for the results.
313		605
314	You can also use condition variables to block your main program until	606	You can also use them to simulate traditional event loops - for example,
315	an event occurs - for example, you could C<< ->wait >> in your main	607	you can block your main program until an event occurs - for example, you
316	program until the user clicks the Quit button in your app, which would C<<	608	could C<< ->recv >> in your main program until the user clicks the Quit
317	->broadcast >> the "quit" event.	609	button of your app, which would C<< ->send >> the "quit" event.
318		610
319	Note that condition variables recurse into the event loop - if you have	611	Note that condition variables recurse into the event loop - if you have
320	two pirces of code that call C<< ->wait >> in a round-robbin fashion, you	612	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
321	lose. Therefore, condition variables are good to export to your caller, but	613	lose. Therefore, condition variables are good to export to your caller, but
322	you should avoid making a blocking wait yourself, at least in callbacks,	614	you should avoid making a blocking wait yourself, at least in callbacks,
323	as this asks for trouble.	615	as this asks for trouble.
324		616
325	This object has two methods:	617	Condition variables are represented by hash refs in perl, and the keys
		618	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
		619	easy (it is often useful to build your own transaction class on top of
		620	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
		621	its C<new> method in your own C<new> method.
		622
		623	There are two "sides" to a condition variable - the "producer side" which
		624	eventually calls C<< -> send >>, and the "consumer side", which waits
		625	for the send to occur.
		626
		627	Example: wait for a timer.
		628
		629	# condition: "wait till the timer is fired"
		630	my $timer_fired = AnyEvent->condvar;
		631
		632	# create the timer - we could wait for, say
		633	# a handle becomign ready, or even an
		634	# AnyEvent::HTTP request to finish, but
		635	# in this case, we simply use a timer:
		636	my $w = AnyEvent->timer (
		637	after => 1,
		638	cb => sub { $timer_fired->send },
		639	);
		640
		641	# this "blocks" (while handling events) till the callback
		642	# calls ->send
		643	$timer_fired->recv;
		644
		645	Example: wait for a timer, but take advantage of the fact that condition
		646	variables are also callable directly.
		647
		648	my $done = AnyEvent->condvar;
		649	my $delay = AnyEvent->timer (after => 5, cb => $done);
		650	$done->recv;
		651
		652	Example: Imagine an API that returns a condvar and doesn't support
		653	callbacks. This is how you make a synchronous call, for example from
		654	the main program:
		655
		656	use AnyEvent::CouchDB;
		657
		658	...
		659
		660	my @info = $couchdb->info->recv;
		661
		662	And this is how you would just set a callback to be called whenever the
		663	results are available:
		664
		665	$couchdb->info->cb (sub {
		666	my @info = $_[0]->recv;
		667	});
		668
		669	=head3 METHODS FOR PRODUCERS
		670
		671	These methods should only be used by the producing side, i.e. the
		672	code/module that eventually sends the signal. Note that it is also
		673	the producer side which creates the condvar in most cases, but it isn't
		674	uncommon for the consumer to create it as well.
326		675
327	=over 4	676	=over 4
328		677
		678	=item $cv->send (...)
		679
		680	Flag the condition as ready - a running C<< ->recv >> and all further
		681	calls to C<recv> will (eventually) return after this method has been
		682	called. If nobody is waiting the send will be remembered.
		683
		684	If a callback has been set on the condition variable, it is called
		685	immediately from within send.
		686
		687	Any arguments passed to the C<send> call will be returned by all
		688	future C<< ->recv >> calls.
		689
		690	Condition variables are overloaded so one can call them directly (as if
		691	they were a code reference). Calling them directly is the same as calling
		692	C<send>.
		693
		694	=item $cv->croak ($error)
		695
		696	Similar to send, but causes all calls to C<< ->recv >> to invoke
		697	C<Carp::croak> with the given error message/object/scalar.
		698
		699	This can be used to signal any errors to the condition variable
		700	user/consumer. Doing it this way instead of calling C<croak> directly
		701	delays the error detection, but has the overwhelming advantage that it
		702	diagnoses the error at the place where the result is expected, and not
		703	deep in some event callback with no connection to the actual code causing
		704	the problem.
		705
		706	=item $cv->begin ([group callback])
		707
329	=item $cv->wait	708	=item $cv->end
330		709
331	Wait (blocking if necessary) until the C<< ->broadcast >> method has been	710	These two methods can be used to combine many transactions/events into
332	called on c<$cv>, while servicing other watchers normally.	711	one. For example, a function that pings many hosts in parallel might want
		712	to use a condition variable for the whole process.
333		713
		714	Every call to C<< ->begin >> will increment a counter, and every call to
		715	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
		716	>>, the (last) callback passed to C<begin> will be executed, passing the
		717	condvar as first argument. That callback is I<supposed> to call C<< ->send
		718	>>, but that is not required. If no group callback was set, C<send> will
		719	be called without any arguments.
		720
		721	You can think of C<< $cv->send >> giving you an OR condition (one call
		722	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		723	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		724
		725	Let's start with a simple example: you have two I/O watchers (for example,
		726	STDOUT and STDERR for a program), and you want to wait for both streams to
		727	close before activating a condvar:
		728
		729	my $cv = AnyEvent->condvar;
		730
		731	$cv->begin; # first watcher
		732	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		733	defined sysread $fh1, my $buf, 4096
		734	or $cv->end;
		735	});
		736
		737	$cv->begin; # second watcher
		738	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		739	defined sysread $fh2, my $buf, 4096
		740	or $cv->end;
		741	});
		742
		743	$cv->recv;
		744
		745	This works because for every event source (EOF on file handle), there is
		746	one call to C<begin>, so the condvar waits for all calls to C<end> before
		747	sending.
		748
		749	The ping example mentioned above is slightly more complicated, as the
		750	there are results to be passwd back, and the number of tasks that are
		751	begun can potentially be zero:
		752
		753	my $cv = AnyEvent->condvar;
		754
		755	my %result;
		756	$cv->begin (sub { shift->send (\%result) });
		757
		758	for my $host (@list_of_hosts) {
		759	$cv->begin;
		760	ping_host_then_call_callback $host, sub {
		761	$result{$host} = ...;
		762	$cv->end;
		763	};
		764	}
		765
		766	$cv->end;
		767
		768	...
		769
		770	my $results = $cv->recv;
		771
		772	This code fragment supposedly pings a number of hosts and calls
		773	C<send> after results for all then have have been gathered - in any
		774	order. To achieve this, the code issues a call to C<begin> when it starts
		775	each ping request and calls C<end> when it has received some result for
		776	it. Since C<begin> and C<end> only maintain a counter, the order in which
		777	results arrive is not relevant.
		778
		779	There is an additional bracketing call to C<begin> and C<end> outside the
		780	loop, which serves two important purposes: first, it sets the callback
		781	to be called once the counter reaches C<0>, and second, it ensures that
		782	C<send> is called even when C<no> hosts are being pinged (the loop
		783	doesn't execute once).
		784
		785	This is the general pattern when you "fan out" into multiple (but
		786	potentially zero) subrequests: use an outer C<begin>/C<end> pair to set
		787	the callback and ensure C<end> is called at least once, and then, for each
		788	subrequest you start, call C<begin> and for each subrequest you finish,
		789	call C<end>.
		790
		791	=back
		792
		793	=head3 METHODS FOR CONSUMERS
		794
		795	These methods should only be used by the consuming side, i.e. the
		796	code awaits the condition.
		797
		798	=over 4
		799
		800	=item $cv->recv
		801
		802	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
		803	>> methods have been called on C<$cv>, while servicing other watchers
		804	normally.
		805
334	You can only wait once on a condition - additional calls will return	806	You can only wait once on a condition - additional calls are valid but
335	immediately.	807	will return immediately.
		808
		809	If an error condition has been set by calling C<< ->croak >>, then this
		810	function will call C<croak>.
		811
		812	In list context, all parameters passed to C<send> will be returned,
		813	in scalar context only the first one will be returned.
		814
		815	Note that doing a blocking wait in a callback is not supported by any
		816	event loop, that is, recursive invocation of a blocking C<< ->recv
		817	>> is not allowed, and the C<recv> call will C<croak> if such a
		818	condition is detected. This condition can be slightly loosened by using
		819	L<Coro::AnyEvent>, which allows you to do a blocking C<< ->recv >> from
		820	any thread that doesn't run the event loop itself.
336		821
337	Not all event models support a blocking wait - some die in that case	822	Not all event models support a blocking wait - some die in that case
338	(programs might want to do that to stay interactive), so I<if you are	823	(programs might want to do that to stay interactive), so I<if you are
339	using this from a module, never require a blocking wait>, but let the	824	using this from a module, never require a blocking wait>. Instead, let the
340	caller decide whether the call will block or not (for example, by coupling	825	caller decide whether the call will block or not (for example, by coupling
341	condition variables with some kind of request results and supporting	826	condition variables with some kind of request results and supporting
342	callbacks so the caller knows that getting the result will not block,	827	callbacks so the caller knows that getting the result will not block,
343	while still suppporting blocking waits if the caller so desires).	828	while still supporting blocking waits if the caller so desires).
344		829
345	Another reason I<never> to C<< ->wait >> in a module is that you cannot	830	You can ensure that C<< ->recv >> never blocks by setting a callback and
346	sensibly have two C<< ->wait >>'s in parallel, as that would require	831	only calling C<< ->recv >> from within that callback (or at a later
347	multiple interpreters or coroutines/threads, none of which C<AnyEvent>	832	time). This will work even when the event loop does not support blocking
348	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and	833	waits otherwise.
349	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
350	from different coroutines, however).
351		834
352	=item $cv->broadcast	835	=item $bool = $cv->ready
353		836
354	Flag the condition as ready - a running C<< ->wait >> and all further	837	Returns true when the condition is "true", i.e. whether C<send> or
355	calls to C<wait> will (eventually) return after this method has been	838	C<croak> have been called.
356	called. If nobody is waiting the broadcast will be remembered..	839
		840	=item $cb = $cv->cb ($cb->($cv))
		841
		842	This is a mutator function that returns the callback set and optionally
		843	replaces it before doing so.
		844
		845	The callback will be called when the condition becomes "true", i.e. when
		846	C<send> or C<croak> are called, with the only argument being the
		847	condition variable itself. If the condition is already true, the
		848	callback is called immediately when it is set. Calling C<recv> inside
		849	the callback or at any later time is guaranteed not to block.
357		850
358	=back	851	=back
359		852
360	Example:	853	=head1 SUPPORTED EVENT LOOPS/BACKENDS
361		854
362	# wait till the result is ready	855	The available backend classes are (every class has its own manpage):
363	my $result_ready = AnyEvent->condvar;
364		856
365	# do something such as adding a timer	857	=over 4
366	# or socket watcher the calls $result_ready->broadcast
367	# when the "result" is ready.
368	# in this case, we simply use a timer:
369	my $w = AnyEvent->timer (
370	after => 1,
371	cb => sub { $result_ready->broadcast },
372	);
373		858
374	# this "blocks" (while handling events) till the watcher	859	=item Backends that are autoprobed when no other event loop can be found.
375	# calls broadcast	860
376	$result_ready->wait;	861	EV is the preferred backend when no other event loop seems to be in
		862	use. If EV is not installed, then AnyEvent will fall back to its own
		863	pure-perl implementation, which is available everywhere as it comes with
		864	AnyEvent itself.
		865
		866	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		867	AnyEvent::Impl::Perl pure-perl AnyEvent::Loop, fast and portable.
		868
		869	=item Backends that are transparently being picked up when they are used.
		870
		871	These will be used if they are already loaded when the first watcher
		872	is created, in which case it is assumed that the application is using
		873	them. This means that AnyEvent will automatically pick the right backend
		874	when the main program loads an event module before anything starts to
		875	create watchers. Nothing special needs to be done by the main program.
		876
		877	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		878	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		879	AnyEvent::Impl::Tk based on Tk, very broken.
		880	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		881	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		882	AnyEvent::Impl::Irssi used when running within irssi.
		883	AnyEvent::Impl::IOAsync based on IO::Async.
		884	AnyEvent::Impl::Cocoa based on Cocoa::EventLoop.
		885	AnyEvent::Impl::FLTK based on FLTK (fltk 2 binding).
		886
		887	=item Backends with special needs.
		888
		889	Qt requires the Qt::Application to be instantiated first, but will
		890	otherwise be picked up automatically. As long as the main program
		891	instantiates the application before any AnyEvent watchers are created,
		892	everything should just work.
		893
		894	AnyEvent::Impl::Qt based on Qt.
		895
		896	=item Event loops that are indirectly supported via other backends.
		897
		898	Some event loops can be supported via other modules:
		899
		900	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		901
		902	B<WxWidgets> has no support for watching file handles. However, you can
		903	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		904	polls 20 times per second, which was considered to be too horrible to even
		905	consider for AnyEvent.
		906
		907	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		908	backend, so it can be supported through POE.
		909
		910	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		911	load L<POE> when detecting them, in the hope that POE will pick them up,
		912	in which case everything will be automatic.
		913
		914	=back
377		915
378	=head1 GLOBAL VARIABLES AND FUNCTIONS	916	=head1 GLOBAL VARIABLES AND FUNCTIONS
379		917
		918	These are not normally required to use AnyEvent, but can be useful to
		919	write AnyEvent extension modules.
		920
380	=over 4	921	=over 4
381		922
382	=item $AnyEvent::MODEL	923	=item $AnyEvent::MODEL
383		924
384	Contains C<undef> until the first watcher is being created. Then it	925	Contains C<undef> until the first watcher is being created, before the
		926	backend has been autodetected.
		927
385	contains the event model that is being used, which is the name of the	928	Afterwards it contains the event model that is being used, which is the
386	Perl class implementing the model. This class is usually one of the	929	name of the Perl class implementing the model. This class is usually one
387	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	930	of the C<AnyEvent::Impl::xxx> modules, but can be any other class in the
388	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	931	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
389		932	will be C<urxvt::anyevent>).
390	The known classes so far are:
391
392	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
393	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
394	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
395	AnyEvent::Impl::Event based on Event, second best choice.
396	AnyEvent::Impl::Glib based on Glib, third-best choice.
397	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
398	AnyEvent::Impl::Tk based on Tk, very bad choice.
399	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
400	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
401	AnyEvent::Impl::POE based on POE, not generic enough for full support.
402
403	There is no support for WxWidgets, as WxWidgets has no support for
404	watching file handles. However, you can use WxWidgets through the
405	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
406	second, which was considered to be too horrible to even consider for
407	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
408	it's adaptor.
409
410	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
411	autodetecting them.
412		933
413	=item AnyEvent::detect	934	=item AnyEvent::detect
414		935
415	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	936	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
416	if necessary. You should only call this function right before you would	937	if necessary. You should only call this function right before you would
417	have created an AnyEvent watcher anyway, that is, as late as possible at	938	have created an AnyEvent watcher anyway, that is, as late as possible at
418	runtime.	939	runtime, and not e.g. during initialisation of your module.
		940
		941	The effect of calling this function is as if a watcher had been created
		942	(specifically, actions that happen "when the first watcher is created"
		943	happen when calling detetc as well).
		944
		945	If you need to do some initialisation before AnyEvent watchers are
		946	created, use C<post_detect>.
		947
		948	=item $guard = AnyEvent::post_detect { BLOCK }
		949
		950	Arranges for the code block to be executed as soon as the event model is
		951	autodetected (or immediately if that has already happened).
		952
		953	The block will be executed I<after> the actual backend has been detected
		954	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		955	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		956	other initialisations - see the sources of L<AnyEvent::Strict> or
		957	L<AnyEvent::AIO> to see how this is used.
		958
		959	The most common usage is to create some global watchers, without forcing
		960	event module detection too early, for example, L<AnyEvent::AIO> creates
		961	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		962	avoid autodetecting the event module at load time.
		963
		964	If called in scalar or list context, then it creates and returns an object
		965	that automatically removes the callback again when it is destroyed (or
		966	C<undef> when the hook was immediately executed). See L<AnyEvent::AIO> for
		967	a case where this is useful.
		968
		969	Example: Create a watcher for the IO::AIO module and store it in
		970	C<$WATCHER>, but do so only do so after the event loop is initialised.
		971
		972	our WATCHER;
		973
		974	my $guard = AnyEvent::post_detect {
		975	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		976	};
		977
		978	# the ||= is important in case post_detect immediately runs the block,
		979	# as to not clobber the newly-created watcher. assigning both watcher and
		980	# post_detect guard to the same variable has the advantage of users being
		981	# able to just C<undef $WATCHER> if the watcher causes them grief.
		982
		983	$WATCHER ||= $guard;
		984
		985	=item @AnyEvent::post_detect
		986
		987	If there are any code references in this array (you can C<push> to it
		988	before or after loading AnyEvent), then they will be called directly
		989	after the event loop has been chosen.
		990
		991	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		992	if it is defined then the event loop has already been detected, and the
		993	array will be ignored.
		994
		995	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		996	it, as it takes care of these details.
		997
		998	This variable is mainly useful for modules that can do something useful
		999	when AnyEvent is used and thus want to know when it is initialised, but do
		1000	not need to even load it by default. This array provides the means to hook
		1001	into AnyEvent passively, without loading it.
		1002
		1003	Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used
		1004	together, you could put this into Coro (this is the actual code used by
		1005	Coro to accomplish this):
		1006
		1007	if (defined $AnyEvent::MODEL) {
		1008	# AnyEvent already initialised, so load Coro::AnyEvent
		1009	require Coro::AnyEvent;
		1010	} else {
		1011	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent
		1012	# as soon as it is
		1013	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };
		1014	}
		1015
		1016	=item AnyEvent::postpone { BLOCK }
		1017
		1018	Arranges for the block to be executed as soon as possible, but not before
		1019	the call itself returns. In practise, the block will be executed just
		1020	before the event loop polls for new events, or shortly afterwards.
		1021
		1022	This function never returns anything (to make the C<return postpone { ...
		1023	}> idiom more useful.
		1024
		1025	To understand the usefulness of this function, consider a function that
		1026	asynchronously does something for you and returns some transaction
		1027	object or guard to let you cancel the operation. For example,
		1028	C<AnyEvent::Socket::tcp_connect>:
		1029
		1030	# start a conenction attempt unless one is active
		1031	$self->{connect_guard} ||= AnyEvent::Socket::tcp_connect "www.example.net", 80, sub {
		1032	delete $self->{connect_guard};
		1033	...
		1034	};
		1035
		1036	Imagine that this function could instantly call the callback, for
		1037	example, because it detects an obvious error such as a negative port
		1038	number. Invoking the callback before the function returns causes problems
		1039	however: the callback will be called and will try to delete the guard
		1040	object. But since the function hasn't returned yet, there is nothing to
		1041	delete. When the function eventually returns it will assign the guard
		1042	object to C<< $self->{connect_guard} >>, where it will likely never be
		1043	deleted, so the program thinks it is still trying to connect.
		1044
		1045	This is where C<AnyEvent::postpone> should be used. Instead of calling the
		1046	callback directly on error:
		1047
		1048	$cb->(undef), return # signal error to callback, BAD!
		1049	if $some_error_condition;
		1050
		1051	It should use C<postpone>:
		1052
		1053	AnyEvent::postpone { $cb->(undef) }, return # signal error to callback, later
		1054	if $some_error_condition;
		1055
		1056	=item AnyEvent::log $level, $msg[, @args]
		1057
		1058	Log the given C<$msg> at the given C<$level>.
		1059
		1060	If L<AnyEvent::Log> is not loaded then this function makes a simple test
		1061	to see whether the message will be logged. If the test succeeds it will
		1062	load AnyEvent::Log and call C<AnyEvent::Log::log> - consequently, look at
		1063	the L<AnyEvent::Log> documentation for details.
		1064
		1065	If the test fails it will simply return. Right now this happens when a
		1066	numerical loglevel is used and it is larger than the level specified via
		1067	C<$ENV{PERL_ANYEVENT_VERBOSE}>.
		1068
		1069	If you want to sprinkle loads of logging calls around your code, consider
		1070	creating a logger callback with the C<AnyEvent::Log::logger> function,
		1071	which can reduce typing, codesize and can reduce the logging overhead
		1072	enourmously.
419		1073
420	=back	1074	=back
421		1075
422	=head1 WHAT TO DO IN A MODULE	1076	=head1 WHAT TO DO IN A MODULE
423		1077
…		…
427	Be careful when you create watchers in the module body - AnyEvent will	1081	Be careful when you create watchers in the module body - AnyEvent will
428	decide which event module to use as soon as the first method is called, so	1082	decide which event module to use as soon as the first method is called, so
429	by calling AnyEvent in your module body you force the user of your module	1083	by calling AnyEvent in your module body you force the user of your module
430	to load the event module first.	1084	to load the event module first.
431		1085
432	Never call C<< ->wait >> on a condition variable unless you I<know> that	1086	Never call C<< ->recv >> on a condition variable unless you I<know> that
433	the C<< ->broadcast >> method has been called on it already. This is	1087	the C<< ->send >> method has been called on it already. This is
434	because it will stall the whole program, and the whole point of using	1088	because it will stall the whole program, and the whole point of using
435	events is to stay interactive.	1089	events is to stay interactive.
436		1090
437	It is fine, however, to call C<< ->wait >> when the user of your module	1091	It is fine, however, to call C<< ->recv >> when the user of your module
438	requests it (i.e. if you create a http request object ad have a method	1092	requests it (i.e. if you create a http request object ad have a method
439	called C<results> that returns the results, it should call C<< ->wait >>	1093	called C<results> that returns the results, it may call C<< ->recv >>
440	freely, as the user of your module knows what she is doing. always).	1094	freely, as the user of your module knows what she is doing. Always).
441		1095
442	=head1 WHAT TO DO IN THE MAIN PROGRAM	1096	=head1 WHAT TO DO IN THE MAIN PROGRAM
443		1097
444	There will always be a single main program - the only place that should	1098	There will always be a single main program - the only place that should
445	dictate which event model to use.	1099	dictate which event model to use.
446		1100
447	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	1101	If the program is not event-based, it need not do anything special, even
448	do anything special (it does not need to be event-based) and let AnyEvent	1102	when it depends on a module that uses an AnyEvent. If the program itself
449	decide which implementation to chose if some module relies on it.	1103	uses AnyEvent, but does not care which event loop is used, all it needs
		1104	to do is C<use AnyEvent>. In either case, AnyEvent will choose the best
		1105	available loop implementation.
450		1106
451	If the main program relies on a specific event model. For example, in	1107	If the main program relies on a specific event model - for example, in
452	Gtk2 programs you have to rely on the Glib module. You should load the	1108	Gtk2 programs you have to rely on the Glib module - you should load the
453	event module before loading AnyEvent or any module that uses it: generally	1109	event module before loading AnyEvent or any module that uses it: generally
454	speaking, you should load it as early as possible. The reason is that	1110	speaking, you should load it as early as possible. The reason is that
455	modules might create watchers when they are loaded, and AnyEvent will	1111	modules might create watchers when they are loaded, and AnyEvent will
456	decide on the event model to use as soon as it creates watchers, and it	1112	decide on the event model to use as soon as it creates watchers, and it
457	might chose the wrong one unless you load the correct one yourself.	1113	might choose the wrong one unless you load the correct one yourself.
458		1114
459	You can chose to use a rather inefficient pure-perl implementation by	1115	You can chose to use a pure-perl implementation by loading the
460	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	1116	C<AnyEvent::Loop> module, which gives you similar behaviour
461	behaviour everywhere, but letting AnyEvent chose is generally better.	1117	everywhere, but letting AnyEvent chose the model is generally better.
		1118
		1119	=head2 MAINLOOP EMULATION
		1120
		1121	Sometimes (often for short test scripts, or even standalone programs who
		1122	only want to use AnyEvent), you do not want to run a specific event loop.
		1123
		1124	In that case, you can use a condition variable like this:
		1125
		1126	AnyEvent->condvar->recv;
		1127
		1128	This has the effect of entering the event loop and looping forever.
		1129
		1130	Note that usually your program has some exit condition, in which case
		1131	it is better to use the "traditional" approach of storing a condition
		1132	variable somewhere, waiting for it, and sending it when the program should
		1133	exit cleanly.
		1134
		1135
		1136	=head1 OTHER MODULES
		1137
		1138	The following is a non-exhaustive list of additional modules that use
		1139	AnyEvent as a client and can therefore be mixed easily with other
		1140	AnyEvent modules and other event loops in the same program. Some of the
		1141	modules come as part of AnyEvent, the others are available via CPAN (see
		1142	L<http://search.cpan.org/search?m=module&q=anyevent%3A%3A*> for
		1143	a longer non-exhaustive list), and the list is heavily biased towards
		1144	modules of the AnyEvent author himself :)
		1145
		1146	=over 4
		1147
		1148	=item L<AnyEvent::Util>
		1149
		1150	Contains various utility functions that replace often-used blocking
		1151	functions such as C<inet_aton> with event/callback-based versions.
		1152
		1153	=item L<AnyEvent::Socket>
		1154
		1155	Provides various utility functions for (internet protocol) sockets,
		1156	addresses and name resolution. Also functions to create non-blocking tcp
		1157	connections or tcp servers, with IPv6 and SRV record support and more.
		1158
		1159	=item L<AnyEvent::Handle>
		1160
		1161	Provide read and write buffers, manages watchers for reads and writes,
		1162	supports raw and formatted I/O, I/O queued and fully transparent and
		1163	non-blocking SSL/TLS (via L<AnyEvent::TLS>).
		1164
		1165	=item L<AnyEvent::DNS>
		1166
		1167	Provides rich asynchronous DNS resolver capabilities.
		1168
		1169	=item L<AnyEvent::HTTP>, L<AnyEvent::IRC>, L<AnyEvent::XMPP>, L<AnyEvent::GPSD>, L<AnyEvent::IGS>, L<AnyEvent::FCP>
		1170
		1171	Implement event-based interfaces to the protocols of the same name (for
		1172	the curious, IGS is the International Go Server and FCP is the Freenet
		1173	Client Protocol).
		1174
		1175	=item L<AnyEvent::AIO>
		1176
		1177	Truly asynchronous (as opposed to non-blocking) I/O, should be in the
		1178	toolbox of every event programmer. AnyEvent::AIO transparently fuses
		1179	L<IO::AIO> and AnyEvent together, giving AnyEvent access to event-based
		1180	file I/O, and much more.
		1181
		1182	=item L<AnyEvent::Filesys::Notify>
		1183
		1184	AnyEvent is good for non-blocking stuff, but it can't detect file or
		1185	path changes (e.g. "watch this directory for new files", "watch this
		1186	file for changes"). The L<AnyEvent::Filesys::Notify> module promises to
		1187	do just that in a portbale fashion, supporting inotify on GNU/Linux and
		1188	some weird, without doubt broken, stuff on OS X to monitor files. It can
		1189	fall back to blocking scans at regular intervals transparently on other
		1190	platforms, so it's about as portable as it gets.
		1191
		1192	(I haven't used it myself, but I haven't heard anybody complaining about
		1193	it yet).
		1194
		1195	=item L<AnyEvent::DBI>
		1196
		1197	Executes L<DBI> requests asynchronously in a proxy process for you,
		1198	notifying you in an event-based way when the operation is finished.
		1199
		1200	=item L<AnyEvent::HTTPD>
		1201
		1202	A simple embedded webserver.
		1203
		1204	=item L<AnyEvent::FastPing>
		1205
		1206	The fastest ping in the west.
		1207
		1208	=item L<Coro>
		1209
		1210	Has special support for AnyEvent via L<Coro::AnyEvent>, which allows you
		1211	to simply invert the flow control - don't call us, we will call you:
		1212
		1213	async {
		1214	Coro::AnyEvent::sleep 5; # creates a 5s timer and waits for it
		1215	print "5 seconds later!\n";
		1216
		1217	Coro::AnyEvent::readable *STDIN; # uses an I/O watcher
		1218	my $line = <STDIN>; # works for ttys
		1219
		1220	AnyEvent::HTTP::http_get "url", Coro::rouse_cb;
		1221	my ($body, $hdr) = Coro::rouse_wait;
		1222	};
		1223
		1224	=back
462		1225
463	=cut	1226	=cut
464		1227
465	package AnyEvent;	1228	package AnyEvent;
466		1229
467	no warnings;	1230	# basically a tuned-down version of common::sense
468	use strict;	1231	sub common_sense {
		1232	# from common:.sense 3.5
		1233	local $^W;
		1234	${^WARNING_BITS} ^= ${^WARNING_BITS} ^ "\x3c\x3f\x33\x00\x0f\xf0\x0f\xc0\xf0\xfc\x33\x00";
		1235	# use strict vars subs - NO UTF-8, as Util.pm doesn't like this atm. (uts46data.pl)
		1236	$^H |= 0x00000600;
		1237	}
469		1238
		1239	BEGIN { AnyEvent::common_sense }
		1240
470	use Carp;	1241	use Carp ();
471		1242
472	our $VERSION = '3.3';	1243	our $VERSION = '7.04';
473	our $MODEL;	1244	our $MODEL;
474
475	our $AUTOLOAD;
476	our @ISA;	1245	our @ISA;
477
478	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
479
480	our @REGISTRY;	1246	our @REGISTRY;
		1247	our $VERBOSE;
		1248	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		1249	our $MAX_SIGNAL_LATENCY = $ENV{PERL_ANYEVENT_MAX_SIGNAL_LATENCY} || 10; # executes after the BEGIN block below (tainting!)
481		1250
		1251	BEGIN {
		1252	require "AnyEvent/constants.pl";
		1253
		1254	eval "sub TAINT (){" . (${^TAINT}*1) . "}";
		1255
		1256	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1257	if ${^TAINT};
		1258
		1259	$ENV{"PERL_ANYEVENT_$_"} = $ENV{"AE_$_"}
		1260	for grep s/^AE_// && !exists $ENV{"PERL_ANYEVENT_$_"}, keys %ENV;
		1261
		1262	@ENV{grep /^PERL_ANYEVENT_/, keys %ENV} = ()
		1263	if ${^TAINT};
		1264
		1265	# $ENV{PERL_ANYEVENT_xxx} now valid
		1266
		1267	$VERBOSE = length $ENV{PERL_ANYEVENT_VERBOSE} ? $ENV{PERL_ANYEVENT_VERBOSE}*1 : 4;
		1268
		1269	my $idx;
		1270	$PROTOCOL{$_} = ++$idx
		1271	for reverse split /\s*,\s*/,
		1272	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		1273	}
		1274
		1275	our @post_detect;
		1276
		1277	sub post_detect(&) {
		1278	my ($cb) = @_;
		1279
		1280	push @post_detect, $cb;
		1281
		1282	defined wantarray
		1283	? bless \$cb, "AnyEvent::Util::postdetect"
		1284	: ()
		1285	}
		1286
		1287	sub AnyEvent::Util::postdetect::DESTROY {
		1288	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		1289	}
		1290
		1291	our $POSTPONE_W;
		1292	our @POSTPONE;
		1293
		1294	sub _postpone_exec {
		1295	undef $POSTPONE_W;
		1296
		1297	&{ shift @POSTPONE }
		1298	while @POSTPONE;
		1299	}
		1300
		1301	sub postpone(&) {
		1302	push @POSTPONE, shift;
		1303
		1304	$POSTPONE_W ||= AE::timer (0, 0, \&_postpone_exec);
		1305
		1306	()
		1307	}
		1308
		1309	sub log($$;@) {
		1310	# only load the big bloated module when we actually are about to log something
		1311	if ($_[0] <= ($VERBOSE || 1)) { # also catches non-numeric levels(!) and fatal
		1312	local ($!, $@);
		1313	require AnyEvent::Log; # among other things, sets $VERBOSE to 9
		1314	# AnyEvent::Log overwrites this function
		1315	goto &log;
		1316	}
		1317
		1318	0 # not logged
		1319	}
		1320
		1321	sub _logger($;$) {
		1322	my ($level, $renabled) = @_;
		1323
		1324	$$renabled = $level <= $VERBOSE;
		1325
		1326	my $logger = [(caller)[0], $level, $renabled];
		1327
		1328	$AnyEvent::Log::LOGGER{$logger+0} = $logger;
		1329
		1330	# return unless defined wantarray;
		1331	#
		1332	# require AnyEvent::Util;
		1333	# my $guard = AnyEvent::Util::guard (sub {
		1334	# # "clean up"
		1335	# delete $LOGGER{$logger+0};
		1336	# });
		1337	#
		1338	# sub {
		1339	# return 0 unless $$renabled;
		1340	#
		1341	# $guard if 0; # keep guard alive, but don't cause runtime overhead
		1342	# require AnyEvent::Log unless $AnyEvent::Log::VERSION;
		1343	# package AnyEvent::Log;
		1344	# _log ($logger->[0], $level, @_) # logger->[0] has been converted at load time
		1345	# }
		1346	}
		1347
		1348	if (length $ENV{PERL_ANYEVENT_LOG}) {
		1349	require AnyEvent::Log; # AnyEvent::Log does the thing for us
		1350	}
		1351
482	my @models = (	1352	our @models = (
483	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
484	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
485	[EV:: => AnyEvent::Impl::EV::],	1353	[EV:: => AnyEvent::Impl::EV::],
		1354	[AnyEvent::Loop:: => AnyEvent::Impl::Perl::],
		1355	# everything below here will not (normally) be autoprobed
		1356	# as the pure perl backend should work everywhere
		1357	# and is usually faster
		1358	[Irssi:: => AnyEvent::Impl::Irssi::], # Irssi has a bogus "Event" package, so msut be near the top
486	[Event:: => AnyEvent::Impl::Event::],	1359	[Event:: => AnyEvent::Impl::Event::], # slow, stable
487	[Glib:: => AnyEvent::Impl::Glib::],	1360	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers
		1361	# everything below here should not be autoloaded
		1362	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
488	[Tk:: => AnyEvent::Impl::Tk::],	1363	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		1364	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		1365	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
489	[Wx:: => AnyEvent::Impl::POE::],	1366	[Wx:: => AnyEvent::Impl::POE::],
490	[Prima:: => AnyEvent::Impl::POE::],	1367	[Prima:: => AnyEvent::Impl::POE::],
491	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1368	[IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # a bitch to autodetect
492	# everything below here will not be autoprobed as the pureperl backend should work everywhere	1369	[Cocoa::EventLoop:: => AnyEvent::Impl::Cocoa::],
493	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy	1370	[FLTK:: => AnyEvent::Impl::FLTK::],
494	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
495	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
496	);	1371	);
497		1372
498	our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);	1373	our @isa_hook;
		1374
		1375	sub _isa_set {
		1376	my @pkg = ("AnyEvent", (map $_->[0], grep defined, @isa_hook), $MODEL);
		1377
		1378	@{"$pkg[$_-1]::ISA"} = $pkg[$_]
		1379	for 1 .. $#pkg;
		1380
		1381	grep $_ && $_->[1], @isa_hook
		1382	and AE::_reset ();
		1383	}
		1384
		1385	# used for hooking AnyEvent::Strict and AnyEvent::Debug::Wrap into the class hierarchy
		1386	sub _isa_hook($$;$) {
		1387	my ($i, $pkg, $reset_ae) = @_;
		1388
		1389	$isa_hook[$i] = $pkg ? [$pkg, $reset_ae] : undef;
		1390
		1391	_isa_set;
		1392	}
		1393
		1394	# all autoloaded methods reserve the complete glob, not just the method slot.
		1395	# due to bugs in perls method cache implementation.
		1396	our @methods = qw(io timer time now now_update signal child idle condvar);
499		1397
500	sub detect() {	1398	sub detect() {
		1399	return $MODEL if $MODEL; # some programs keep references to detect
		1400
		1401	# IO::Async::Loop::AnyEvent is extremely evil, refuse to work with it
		1402	# the author knows about the problems and what it does to AnyEvent as a whole
		1403	# (and the ability of others to use AnyEvent), but simply wants to abuse AnyEvent
		1404	# anyway.
		1405	AnyEvent::log fatal => "IO::Async::Loop::AnyEvent detected - that module is broken by\n"
		1406	. "design, abuses internals and breaks AnyEvent - will not continue."
		1407	if exists $INC{"IO/Async/Loop/AnyEvent.pm"};
		1408
		1409	local $!; # for good measure
		1410	local $SIG{__DIE__}; # we use eval
		1411
		1412	# free some memory
		1413	*detect = sub () { $MODEL };
		1414	# undef &func doesn't correctly update the method cache. grmbl.
		1415	# so we delete the whole glob. grmbl.
		1416	# otoh, perl doesn't let me undef an active usb, but it lets me free
		1417	# a glob with an active sub. hrm. i hope it works, but perl is
		1418	# usually buggy in this department. sigh.
		1419	delete @{"AnyEvent::"}{@methods};
		1420	undef @methods;
		1421
		1422	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z0-9:]+)$/) {
		1423	my $model = $1;
		1424	$model = "AnyEvent::Impl::$model" unless $model =~ s/::$//;
		1425	if (eval "require $model") {
		1426	AnyEvent::log 7 => "Loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.";
		1427	$MODEL = $model;
		1428	} else {
		1429	AnyEvent::log 4 => "Unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@";
		1430	}
		1431	}
		1432
		1433	# check for already loaded models
501	unless ($MODEL) {	1434	unless ($MODEL) {
502	no strict 'refs';	1435	for (@REGISTRY, @models) {
503		1436	my ($package, $model) = @$_;
504	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	1437	if (${"$package\::VERSION"} > 0) {
505	my $model = "AnyEvent::Impl::$1";
506	if (eval "require $model") {	1438	if (eval "require $model") {
		1439	AnyEvent::log 7 => "Autodetected model '$model', using it.";
507	$MODEL = $model;	1440	$MODEL = $model;
508	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	1441	last;
509	} else {	1442	} else {
510	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;	1443	AnyEvent::log 8 => "Detected event loop $package, but cannot load '$model', skipping: $@";
		1444	}
511	}	1445	}
512	}	1446	}
513		1447
514	# check for already loaded models
515	unless ($MODEL) {	1448	unless ($MODEL) {
		1449	# try to autoload a model
516	for (@REGISTRY, @models) {	1450	for (@REGISTRY, @models) {
517	my ($package, $model) = @$_;	1451	my ($package, $model) = @$_;
		1452	if (
		1453	eval "require $package"
518	if (${"$package\::VERSION"} > 0) {	1454	and ${"$package\::VERSION"} > 0
519	if (eval "require $model") {	1455	and eval "require $model"
		1456	) {
		1457	AnyEvent::log 7 => "Autoloaded model '$model', using it.";
520	$MODEL = $model;	1458	$MODEL = $model;
521	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;
522	last;	1459	last;
523	}
524	}	1460	}
525	}	1461	}
526		1462
527	unless ($MODEL) {	1463	$MODEL
528	# try to load a model	1464	or AnyEvent::log fatal => "Backend autodetection failed - did you properly install AnyEvent?";
		1465	}
		1466	}
529		1467
530	for (@REGISTRY, @models) {	1468	# free memory only needed for probing
531	my ($package, $model) = @$_;	1469	undef @models;
532	if (eval "require $package"	1470	undef @REGISTRY;
533	and ${"$package\::VERSION"} > 0	1471
534	and eval "require $model") {	1472	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
535	$MODEL = $model;	1473
536	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;	1474	# now nuke some methods that are overridden by the backend.
		1475	# SUPER usage is not allowed in these.
		1476	for (qw(time signal child idle)) {
		1477	undef &{"AnyEvent::Base::$_"}
		1478	if defined &{"$MODEL\::$_"};
		1479	}
		1480
		1481	_isa_set;
		1482
		1483	# we're officially open!
		1484
		1485	if ($ENV{PERL_ANYEVENT_STRICT}) {
		1486	require AnyEvent::Strict;
		1487	}
		1488
		1489	if ($ENV{PERL_ANYEVENT_DEBUG_WRAP}) {
		1490	require AnyEvent::Debug;
		1491	AnyEvent::Debug::wrap ($ENV{PERL_ANYEVENT_DEBUG_WRAP});
		1492	}
		1493
		1494	if (length $ENV{PERL_ANYEVENT_DEBUG_SHELL}) {
		1495	require AnyEvent::Socket;
		1496	require AnyEvent::Debug;
		1497
		1498	my $shell = $ENV{PERL_ANYEVENT_DEBUG_SHELL};
		1499	$shell =~ s/\$\$/$$/g;
		1500
		1501	my ($host, $service) = AnyEvent::Socket::parse_hostport ($shell);
		1502	$AnyEvent::Debug::SHELL = AnyEvent::Debug::shell ($host, $service);
		1503	}
		1504
		1505	# now the anyevent environment is set up as the user told us to, so
		1506	# call the actual user code - post detects
		1507
		1508	(shift @post_detect)->() while @post_detect;
		1509	undef @post_detect;
		1510
		1511	*post_detect = sub(&) {
		1512	shift->();
		1513
		1514	undef
		1515	};
		1516
		1517	$MODEL
		1518	}
		1519
		1520	for my $name (@methods) {
		1521	*$name = sub {
		1522	detect;
		1523	# we use goto because
		1524	# a) it makes the thunk more transparent
		1525	# b) it allows us to delete the thunk later
		1526	goto &{ UNIVERSAL::can AnyEvent => "SUPER::$name" }
		1527	};
		1528	}
		1529
		1530	# utility function to dup a filehandle. this is used by many backends
		1531	# to support binding more than one watcher per filehandle (they usually
		1532	# allow only one watcher per fd, so we dup it to get a different one).
		1533	sub _dupfh($$;$$) {
		1534	my ($poll, $fh, $r, $w) = @_;
		1535
		1536	# cygwin requires the fh mode to be matching, unix doesn't
		1537	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1538
		1539	open my $fh2, $mode, $fh
		1540	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1541
		1542	# we assume CLOEXEC is already set by perl in all important cases
		1543
		1544	($fh2, $rw)
		1545	}
		1546
		1547	=head1 SIMPLIFIED AE API
		1548
		1549	Starting with version 5.0, AnyEvent officially supports a second, much
		1550	simpler, API that is designed to reduce the calling, typing and memory
		1551	overhead by using function call syntax and a fixed number of parameters.
		1552
		1553	See the L<AE> manpage for details.
		1554
		1555	=cut
		1556
		1557	package AE;
		1558
		1559	our $VERSION = $AnyEvent::VERSION;
		1560
		1561	sub _reset() {
		1562	eval q{
		1563	# fall back to the main API by default - backends and AnyEvent::Base
		1564	# implementations can overwrite these.
		1565
		1566	sub io($$$) {
		1567	AnyEvent->io (fh => $_[0], poll => $_[1] ? "w" : "r", cb => $_[2])
		1568	}
		1569
		1570	sub timer($$$) {
		1571	AnyEvent->timer (after => $_[0], interval => $_[1], cb => $_[2])
		1572	}
		1573
		1574	sub signal($$) {
		1575	AnyEvent->signal (signal => $_[0], cb => $_[1])
		1576	}
		1577
		1578	sub child($$) {
		1579	AnyEvent->child (pid => $_[0], cb => $_[1])
		1580	}
		1581
		1582	sub idle($) {
		1583	AnyEvent->idle (cb => $_[0]);
		1584	}
		1585
		1586	sub cv(;&) {
		1587	AnyEvent->condvar (@_ ? (cb => $_[0]) : ())
		1588	}
		1589
		1590	sub now() {
		1591	AnyEvent->now
		1592	}
		1593
		1594	sub now_update() {
		1595	AnyEvent->now_update
		1596	}
		1597
		1598	sub time() {
		1599	AnyEvent->time
		1600	}
		1601
		1602	*postpone = \&AnyEvent::postpone;
		1603	*log = \&AnyEvent::log;
		1604	};
		1605	die if $@;
		1606	}
		1607
		1608	BEGIN { _reset }
		1609
		1610	package AnyEvent::Base;
		1611
		1612	# default implementations for many methods
		1613
		1614	sub time {
		1615	eval q{ # poor man's autoloading {}
		1616	# probe for availability of Time::HiRes
		1617	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1618	*time = sub { Time::HiRes::time () };
		1619	*AE::time = \& Time::HiRes::time ;
		1620	*now = \&time;
		1621	AnyEvent::log 8 => "using Time::HiRes for sub-second timing accuracy.";
		1622	# if (eval "use POSIX (); (POSIX::times())...
		1623	} else {
		1624	*time = sub { CORE::time };
		1625	*AE::time = sub (){ CORE::time };
		1626	*now = \&time;
		1627	AnyEvent::log 3 => "Using built-in time(), no sub-second resolution!";
		1628	}
		1629	};
		1630	die if $@;
		1631
		1632	&time
		1633	}
		1634
		1635	*now = \&time;
		1636	sub now_update { }
		1637
		1638	sub _poll {
		1639	Carp::croak "$AnyEvent::MODEL does not support blocking waits. Caught";
		1640	}
		1641
		1642	# default implementation for ->condvar
		1643	# in fact, the default should not be overwritten
		1644
		1645	sub condvar {
		1646	eval q{ # poor man's autoloading {}
		1647	*condvar = sub {
		1648	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
		1649	};
		1650
		1651	*AE::cv = sub (;&) {
		1652	bless { @_ ? (_ae_cb => shift) : () }, "AnyEvent::CondVar"
		1653	};
		1654	};
		1655	die if $@;
		1656
		1657	&condvar
		1658	}
		1659
		1660	# default implementation for ->signal
		1661
		1662	our $HAVE_ASYNC_INTERRUPT;
		1663
		1664	sub _have_async_interrupt() {
		1665	$HAVE_ASYNC_INTERRUPT = 1*(!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT}
		1666	&& eval "use Async::Interrupt 1.02 (); 1")
		1667	unless defined $HAVE_ASYNC_INTERRUPT;
		1668
		1669	$HAVE_ASYNC_INTERRUPT
		1670	}
		1671
		1672	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1673	our (%SIG_ASY, %SIG_ASY_W);
		1674	our ($SIG_COUNT, $SIG_TW);
		1675
		1676	# install a dummy wakeup watcher to reduce signal catching latency
		1677	# used by Impls
		1678	sub _sig_add() {
		1679	unless ($SIG_COUNT++) {
		1680	# try to align timer on a full-second boundary, if possible
		1681	my $NOW = AE::now;
		1682
		1683	$SIG_TW = AE::timer
		1684	$MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1685	$MAX_SIGNAL_LATENCY,
		1686	sub { } # just for the PERL_ASYNC_CHECK
		1687	;
		1688	}
		1689	}
		1690
		1691	sub _sig_del {
		1692	undef $SIG_TW
		1693	unless --$SIG_COUNT;
		1694	}
		1695
		1696	our $_sig_name_init; $_sig_name_init = sub {
		1697	eval q{ # poor man's autoloading {}
		1698	undef $_sig_name_init;
		1699
		1700	if (_have_async_interrupt) {
		1701	*sig2num = \&Async::Interrupt::sig2num;
		1702	*sig2name = \&Async::Interrupt::sig2name;
		1703	} else {
		1704	require Config;
		1705
		1706	my %signame2num;
		1707	@signame2num{ split ' ', $Config::Config{sig_name} }
		1708	= split ' ', $Config::Config{sig_num};
		1709
		1710	my @signum2name;
		1711	@signum2name[values %signame2num] = keys %signame2num;
		1712
		1713	*sig2num = sub($) {
		1714	$_[0] > 0 ? shift : $signame2num{+shift}
		1715	};
		1716	*sig2name = sub ($) {
		1717	$_[0] > 0 ? $signum2name[+shift] : shift
		1718	};
		1719	}
		1720	};
		1721	die if $@;
		1722	};
		1723
		1724	sub sig2num ($) { &$_sig_name_init; &sig2num }
		1725	sub sig2name($) { &$_sig_name_init; &sig2name }
		1726
		1727	sub signal {
		1728	eval q{ # poor man's autoloading {}
		1729	# probe for availability of Async::Interrupt
		1730	if (_have_async_interrupt) {
		1731	AnyEvent::log 8 => "Using Async::Interrupt for race-free signal handling.";
		1732
		1733	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1734	$SIG_IO = AE::io $SIGPIPE_R->fileno, 0, \&_signal_exec;
		1735
		1736	} else {
		1737	AnyEvent::log 8 => "Using emulated perl signal handling with latency timer.";
		1738
		1739	if (AnyEvent::WIN32) {
		1740	require AnyEvent::Util;
		1741
		1742	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1743	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R, 1) if $SIGPIPE_R;
		1744	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W, 1) if $SIGPIPE_W; # just in case
		1745	} else {
		1746	pipe $SIGPIPE_R, $SIGPIPE_W;
		1747	fcntl $SIGPIPE_R, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_R;
		1748	fcntl $SIGPIPE_W, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_W; # just in case
		1749
		1750	# not strictly required, as $^F is normally 2, but let's make sure...
		1751	fcntl $SIGPIPE_R, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1752	fcntl $SIGPIPE_W, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1753	}
		1754
		1755	$SIGPIPE_R
		1756	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1757
		1758	$SIG_IO = AE::io $SIGPIPE_R, 0, \&_signal_exec;
		1759	}
		1760
		1761	*signal = $HAVE_ASYNC_INTERRUPT
		1762	? sub {
		1763	my (undef, %arg) = @_;
		1764
		1765	# async::interrupt
		1766	my $signal = sig2num $arg{signal};
		1767	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1768
		1769	$SIG_ASY{$signal} ||= new Async::Interrupt
		1770	cb => sub { undef $SIG_EV{$signal} },
		1771	signal => $signal,
		1772	pipe => [$SIGPIPE_R->filenos],
		1773	pipe_autodrain => 0,
		1774	;
		1775
		1776	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1777	}
		1778	: sub {
		1779	my (undef, %arg) = @_;
		1780
		1781	# pure perl
		1782	my $signal = sig2name $arg{signal};
		1783	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1784
		1785	$SIG{$signal} ||= sub {
537	last;	1786	local $!;
		1787	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1788	undef $SIG_EV{$signal};
538	}	1789	};
		1790
		1791	# can't do signal processing without introducing races in pure perl,
		1792	# so limit the signal latency.
		1793	_sig_add;
		1794
		1795	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1796	}
		1797	;
		1798
		1799	*AnyEvent::Base::signal::DESTROY = sub {
		1800	my ($signal, $cb) = @{$_[0]};
		1801
		1802	_sig_del;
		1803
		1804	delete $SIG_CB{$signal}{$cb};
		1805
		1806	$HAVE_ASYNC_INTERRUPT
		1807	? delete $SIG_ASY{$signal}
		1808	: # delete doesn't work with older perls - they then
		1809	# print weird messages, or just unconditionally exit
		1810	# instead of getting the default action.
		1811	undef $SIG{$signal}
		1812	unless keys %{ $SIG_CB{$signal} };
		1813	};
		1814
		1815	*_signal_exec = sub {
		1816	$HAVE_ASYNC_INTERRUPT
		1817	? $SIGPIPE_R->drain
		1818	: sysread $SIGPIPE_R, (my $dummy), 9;
		1819
		1820	while (%SIG_EV) {
		1821	for (keys %SIG_EV) {
		1822	delete $SIG_EV{$_};
		1823	&$_ for values %{ $SIG_CB{$_} || {} };
539	}	1824	}
540
541	$MODEL
542	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV (or Coro+EV), Event (or Coro+Event) or Glib.";
543	}	1825	}
544	}	1826	};
545
546	unshift @ISA, $MODEL;
547	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
548	}
549
550	$MODEL
551	}
552
553	sub AUTOLOAD {
554	(my $func = $AUTOLOAD) =~ s/.*://;
555
556	$method{$func}
557	or croak "$func: not a valid method for AnyEvent objects";
558
559	detect unless $MODEL;
560
561	my $class = shift;
562	$class->$func (@_);
563	}
564
565	package AnyEvent::Base;
566
567	# default implementation for ->condvar, ->wait, ->broadcast
568
569	sub condvar {
570	bless \my $flag, "AnyEvent::Base::CondVar"
571	}
572
573	sub AnyEvent::Base::CondVar::broadcast {
574	${$_[0]}++;
575	}
576
577	sub AnyEvent::Base::CondVar::wait {
578	AnyEvent->one_event while !${$_[0]};
579	}
580
581	# default implementation for ->signal
582
583	our %SIG_CB;
584
585	sub signal {
586	my (undef, %arg) = @_;
587
588	my $signal = uc $arg{signal}
589	or Carp::croak "required option 'signal' is missing";
590
591	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
592	$SIG{$signal} ||= sub {
593	$_->() for values %{ $SIG_CB{$signal} || {} };
594	};	1827	};
		1828	die if $@;
595		1829
596	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1830	&signal
597	}
598
599	sub AnyEvent::Base::Signal::DESTROY {
600	my ($signal, $cb) = @{$_[0]};
601
602	delete $SIG_CB{$signal}{$cb};
603
604	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };
605	}	1831	}
606		1832
607	# default implementation for ->child	1833	# default implementation for ->child
608		1834
609	our %PID_CB;	1835	our %PID_CB;
610	our $CHLD_W;	1836	our $CHLD_W;
611	our $CHLD_DELAY_W;	1837	our $CHLD_DELAY_W;
612	our $PID_IDLE;
613	our $WNOHANG;
614		1838
615	sub _child_wait {	1839	# used by many Impl's
616	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1840	sub _emit_childstatus($$) {
		1841	my (undef, $rpid, $rstatus) = @_;
		1842
		1843	$_->($rpid, $rstatus)
617	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1844	for values %{ $PID_CB{$rpid} || {} },
618	(values %{ $PID_CB{0} || {} });	1845	values %{ $PID_CB{0} || {} };
		1846	}
		1847
		1848	sub child {
		1849	eval q{ # poor man's autoloading {}
		1850	*_sigchld = sub {
		1851	my $pid;
		1852
		1853	AnyEvent->_emit_childstatus ($pid, $?)
		1854	while ($pid = waitpid -1, WNOHANG) > 0;
		1855	};
		1856
		1857	*child = sub {
		1858	my (undef, %arg) = @_;
		1859
		1860	my $pid = $arg{pid};
		1861	my $cb = $arg{cb};
		1862
		1863	$PID_CB{$pid}{$cb+0} = $cb;
		1864
		1865	unless ($CHLD_W) {
		1866	$CHLD_W = AE::signal CHLD => \&_sigchld;
		1867	# child could be a zombie already, so make at least one round
		1868	&_sigchld;
		1869	}
		1870
		1871	bless [$pid, $cb+0], "AnyEvent::Base::child"
		1872	};
		1873
		1874	*AnyEvent::Base::child::DESTROY = sub {
		1875	my ($pid, $icb) = @{$_[0]};
		1876
		1877	delete $PID_CB{$pid}{$icb};
		1878	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
		1879
		1880	undef $CHLD_W unless keys %PID_CB;
		1881	};
		1882	};
		1883	die if $@;
		1884
		1885	&child
		1886	}
		1887
		1888	# idle emulation is done by simply using a timer, regardless
		1889	# of whether the process is idle or not, and not letting
		1890	# the callback use more than 50% of the time.
		1891	sub idle {
		1892	eval q{ # poor man's autoloading {}
		1893	*idle = sub {
		1894	my (undef, %arg) = @_;
		1895
		1896	my ($cb, $w, $rcb) = $arg{cb};
		1897
		1898	$rcb = sub {
		1899	if ($cb) {
		1900	$w = AE::time;
		1901	&$cb;
		1902	$w = AE::time - $w;
		1903
		1904	# never use more then 50% of the time for the idle watcher,
		1905	# within some limits
		1906	$w = 0.0001 if $w < 0.0001;
		1907	$w = 5 if $w > 5;
		1908
		1909	$w = AE::timer $w, 0, $rcb;
		1910	} else {
		1911	# clean up...
		1912	undef $w;
		1913	undef $rcb;
		1914	}
		1915	};
		1916
		1917	$w = AE::timer 0.05, 0, $rcb;
		1918
		1919	bless \\$cb, "AnyEvent::Base::idle"
		1920	};
		1921
		1922	*AnyEvent::Base::idle::DESTROY = sub {
		1923	undef $${$_[0]};
		1924	};
		1925	};
		1926	die if $@;
		1927
		1928	&idle
		1929	}
		1930
		1931	package AnyEvent::CondVar;
		1932
		1933	our @ISA = AnyEvent::CondVar::Base::;
		1934
		1935	# only to be used for subclassing
		1936	sub new {
		1937	my $class = shift;
		1938	bless AnyEvent->condvar (@_), $class
		1939	}
		1940
		1941	package AnyEvent::CondVar::Base;
		1942
		1943	#use overload
		1944	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1945	# fallback => 1;
		1946
		1947	# save 300+ kilobytes by dirtily hardcoding overloading
		1948	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1949	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1950	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1951	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1952
		1953	our $WAITING;
		1954
		1955	sub _send {
		1956	# nop
		1957	}
		1958
		1959	sub _wait {
		1960	AnyEvent->_poll until $_[0]{_ae_sent};
		1961	}
		1962
		1963	sub send {
		1964	my $cv = shift;
		1965	$cv->{_ae_sent} = [@_];
		1966	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1967	$cv->_send;
		1968	}
		1969
		1970	sub croak {
		1971	$_[0]{_ae_croak} = $_[1];
		1972	$_[0]->send;
		1973	}
		1974
		1975	sub ready {
		1976	$_[0]{_ae_sent}
		1977	}
		1978
		1979	sub recv {
		1980	unless ($_[0]{_ae_sent}) {
		1981	$WAITING
		1982	and Carp::croak "AnyEvent::CondVar: recursive blocking wait attempted";
		1983
		1984	local $WAITING = 1;
		1985	$_[0]->_wait;
619	}	1986	}
620		1987
621	undef $PID_IDLE;	1988	$_[0]{_ae_croak}
622	}	1989	and Carp::croak $_[0]{_ae_croak};
623		1990
624	sub _sigchld {	1991	wantarray
625	# make sure we deliver these changes "synchronous" with the event loop.	1992	? @{ $_[0]{_ae_sent} }
626	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {	1993	: $_[0]{_ae_sent}[0]
627	undef $CHLD_DELAY_W;
628	&_child_wait;
629	});
630	}	1994	}
631		1995
632	sub child {	1996	sub cb {
633	my (undef, %arg) = @_;	1997	my $cv = shift;
634		1998
635	defined (my $pid = $arg{pid} + 0)	1999	@_
636	or Carp::croak "required option 'pid' is missing";	2000	and $cv->{_ae_cb} = shift
		2001	and $cv->{_ae_sent}
		2002	and (delete $cv->{_ae_cb})->($cv);
637		2003
638	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	2004	$cv->{_ae_cb}
639
640	unless ($WNOHANG) {
641	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;
642	}
643
644	unless ($CHLD_W) {
645	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
646	# child could be a zombie already, so make at least one round
647	&_sigchld;
648	}
649
650	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"
651	}	2005	}
652		2006
653	sub AnyEvent::Base::Child::DESTROY {	2007	sub begin {
654	my ($pid, $cb) = @{$_[0]};	2008	++$_[0]{_ae_counter};
655		2009	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
656	delete $PID_CB{$pid}{$cb};
657	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
658
659	undef $CHLD_W unless keys %PID_CB;
660	}	2010	}
		2011
		2012	sub end {
		2013	return if --$_[0]{_ae_counter};
		2014	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		2015	}
		2016
		2017	# undocumented/compatibility with pre-3.4
		2018	*broadcast = \&send;
		2019	*wait = \&recv;
		2020
		2021	=head1 ERROR AND EXCEPTION HANDLING
		2022
		2023	In general, AnyEvent does not do any error handling - it relies on the
		2024	caller to do that if required. The L<AnyEvent::Strict> module (see also
		2025	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		2026	checking of all AnyEvent methods, however, which is highly useful during
		2027	development.
		2028
		2029	As for exception handling (i.e. runtime errors and exceptions thrown while
		2030	executing a callback), this is not only highly event-loop specific, but
		2031	also not in any way wrapped by this module, as this is the job of the main
		2032	program.
		2033
		2034	The pure perl event loop simply re-throws the exception (usually
		2035	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		2036	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		2037	so on.
		2038
		2039	=head1 ENVIRONMENT VARIABLES
		2040
		2041	AnyEvent supports a number of environment variables that tune the
		2042	runtime behaviour. They are usually evaluated when AnyEvent is
		2043	loaded, initialised, or a submodule that uses them is loaded. Many of
		2044	them also cause AnyEvent to load additional modules - for example,
		2045	C<PERL_ANYEVENT_DEBUG_WRAP> causes the L<AnyEvent::Debug> module to be
		2046	loaded.
		2047
		2048	All the environment variables documented here start with
		2049	C<PERL_ANYEVENT_>, which is what AnyEvent considers its own
		2050	namespace. Other modules are encouraged (but by no means required) to use
		2051	C<PERL_ANYEVENT_SUBMODULE> if they have registered the AnyEvent::Submodule
		2052	namespace on CPAN, for any submodule. For example, L<AnyEvent::HTTP> could
		2053	be expected to use C<PERL_ANYEVENT_HTTP_PROXY> (it should not access env
		2054	variables starting with C<AE_>, see below).
		2055
		2056	All variables can also be set via the C<AE_> prefix, that is, instead
		2057	of setting C<PERL_ANYEVENT_VERBOSE> you can also set C<AE_VERBOSE>. In
		2058	case there is a clash btween anyevent and another program that uses
		2059	C<AE_something> you can set the corresponding C<PERL_ANYEVENT_something>
		2060	variable to the empty string, as those variables take precedence.
		2061
		2062	When AnyEvent is first loaded, it copies all C<AE_xxx> env variables
		2063	to their C<PERL_ANYEVENT_xxx> counterpart unless that variable already
		2064	exists. If taint mode is on, then AnyEvent will remove I<all> environment
		2065	variables starting with C<PERL_ANYEVENT_> from C<%ENV> (or replace them
		2066	with C<undef> or the empty string, if the corresaponding C<AE_> variable
		2067	is set).
		2068
		2069	The exact algorithm is currently:
		2070
		2071	1. if taint mode enabled, delete all PERL_ANYEVENT_xyz variables from %ENV
		2072	2. copy over AE_xyz to PERL_ANYEVENT_xyz unless the latter alraedy exists
		2073	3. if taint mode enabled, set all PERL_ANYEVENT_xyz variables to undef.
		2074
		2075	This ensures that child processes will not see the C<AE_> variables.
		2076
		2077	The following environment variables are currently known to AnyEvent:
		2078
		2079	=over 4
		2080
		2081	=item C<PERL_ANYEVENT_VERBOSE>
		2082
		2083	By default, AnyEvent will log messages with loglevel C<4> (C<error>) or
		2084	higher (see L<AnyEvent::Log>). You can set this environment variable to a
		2085	numerical loglevel to make AnyEvent more (or less) talkative.
		2086
		2087	If you want to do more than just set the global logging level
		2088	you should have a look at C<PERL_ANYEVENT_LOG>, which allows much more
		2089	complex specifications.
		2090
		2091	When set to C<0> (C<off>), then no messages whatsoever will be logged with
		2092	everything else at defaults.
		2093
		2094	When set to C<5> or higher (C<warn>), AnyEvent warns about unexpected
		2095	conditions, such as not being able to load the event model specified by
		2096	C<PERL_ANYEVENT_MODEL>, or a guard callback throwing an exception - this
		2097	is the minimum recommended level for use during development.
		2098
		2099	When set to C<7> or higher (info), AnyEvent reports which event model it
		2100	chooses.
		2101
		2102	When set to C<8> or higher (debug), then AnyEvent will report extra
		2103	information on which optional modules it loads and how it implements
		2104	certain features.
		2105
		2106	=item C<PERL_ANYEVENT_LOG>
		2107
		2108	Accepts rather complex logging specifications. For example, you could log
		2109	all C<debug> messages of some module to stderr, warnings and above to
		2110	stderr, and errors and above to syslog, with:
		2111
		2112	PERL_ANYEVENT_LOG=Some::Module=debug,+log:filter=warn,+%syslog:%syslog=error,syslog
		2113
		2114	For the rather extensive details, see L<AnyEvent::Log>.
		2115
		2116	This variable is evaluated when AnyEvent (or L<AnyEvent::Log>) is loaded,
		2117	so will take effect even before AnyEvent has initialised itself.
		2118
		2119	Note that specifying this environment variable causes the L<AnyEvent::Log>
		2120	module to be loaded, while C<PERL_ANYEVENT_VERBOSE> does not, so only
		2121	using the latter saves a few hundred kB of memory unless a module
		2122	explicitly needs the extra features of AnyEvent::Log.
		2123
		2124	=item C<PERL_ANYEVENT_STRICT>
		2125
		2126	AnyEvent does not do much argument checking by default, as thorough
		2127	argument checking is very costly. Setting this variable to a true value
		2128	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		2129	check the arguments passed to most method calls. If it finds any problems,
		2130	it will croak.
		2131
		2132	In other words, enables "strict" mode.
		2133
		2134	Unlike C<use strict> (or its modern cousin, C<< use L<common::sense>
		2135	>>, it is definitely recommended to keep it off in production. Keeping
		2136	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		2137	can be very useful, however.
		2138
		2139	=item C<PERL_ANYEVENT_DEBUG_SHELL>
		2140
		2141	If this env variable is nonempty, then its contents will be interpreted by
		2142	C<AnyEvent::Socket::parse_hostport> and C<AnyEvent::Debug::shell> (after
		2143	replacing every occurance of C<$$> by the process pid). The shell object
		2144	is saved in C<$AnyEvent::Debug::SHELL>.
		2145
		2146	This happens when the first watcher is created.
		2147
		2148	For example, to bind a debug shell on a unix domain socket in
		2149	F<< /tmp/debug<pid>.sock >>, you could use this:
		2150
		2151	PERL_ANYEVENT_DEBUG_SHELL=/tmp/debug\$\$.sock perlprog
		2152	# connect with e.g.: socat readline /tmp/debug123.sock
		2153
		2154	Or to bind to tcp port 4545 on localhost:
		2155
		2156	PERL_ANYEVENT_DEBUG_SHELL=127.0.0.1:4545 perlprog
		2157	# connect with e.g.: telnet localhost 4545
		2158
		2159	Note that creating sockets in F</tmp> or on localhost is very unsafe on
		2160	multiuser systems.
		2161
		2162	=item C<PERL_ANYEVENT_DEBUG_WRAP>
		2163
		2164	Can be set to C<0>, C<1> or C<2> and enables wrapping of all watchers for
		2165	debugging purposes. See C<AnyEvent::Debug::wrap> for details.
		2166
		2167	=item C<PERL_ANYEVENT_MODEL>
		2168
		2169	This can be used to specify the event model to be used by AnyEvent, before
		2170	auto detection and -probing kicks in.
		2171
		2172	It normally is a string consisting entirely of ASCII letters (e.g. C<EV>
		2173	or C<IOAsync>). The string C<AnyEvent::Impl::> gets prepended and the
		2174	resulting module name is loaded and - if the load was successful - used as
		2175	event model backend. If it fails to load then AnyEvent will proceed with
		2176	auto detection and -probing.
		2177
		2178	If the string ends with C<::> instead (e.g. C<AnyEvent::Impl::EV::>) then
		2179	nothing gets prepended and the module name is used as-is (hint: C<::> at
		2180	the end of a string designates a module name and quotes it appropriately).
		2181
		2182	For example, to force the pure perl model (L<AnyEvent::Loop::Perl>) you
		2183	could start your program like this:
		2184
		2185	PERL_ANYEVENT_MODEL=Perl perl ...
		2186
		2187	=item C<PERL_ANYEVENT_IO_MODEL>
		2188
		2189	The current file I/O model - see L<AnyEvent::IO> for more info.
		2190
		2191	At the moment, only C<Perl> (small, pure-perl, synchronous) and
		2192	C<IOAIO> (truly asynchronous) are supported. The default is C<IOAIO> if
		2193	L<AnyEvent::AIO> can be loaded, otherwise it is C<Perl>.
		2194
		2195	=item C<PERL_ANYEVENT_PROTOCOLS>
		2196
		2197	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		2198	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		2199	of auto probing).
		2200
		2201	Must be set to a comma-separated list of protocols or address families,
		2202	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		2203	used, and preference will be given to protocols mentioned earlier in the
		2204	list.
		2205
		2206	This variable can effectively be used for denial-of-service attacks
		2207	against local programs (e.g. when setuid), although the impact is likely
		2208	small, as the program has to handle conenction and other failures anyways.
		2209
		2210	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		2211	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		2212	- only support IPv4, never try to resolve or contact IPv6
		2213	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		2214	IPv6, but prefer IPv6 over IPv4.
		2215
		2216	=item C<PERL_ANYEVENT_HOSTS>
		2217
		2218	This variable, if specified, overrides the F</etc/hosts> file used by
		2219	L<AnyEvent::Socket>C<::resolve_sockaddr>, i.e. hosts aliases will be read
		2220	from that file instead.
		2221
		2222	=item C<PERL_ANYEVENT_EDNS0>
		2223
		2224	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension for
		2225	DNS. This extension is generally useful to reduce DNS traffic, especially
		2226	when DNSSEC is involved, but some (broken) firewalls drop such DNS
		2227	packets, which is why it is off by default.
		2228
		2229	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		2230	EDNS0 in its DNS requests.
		2231
		2232	=item C<PERL_ANYEVENT_MAX_FORKS>
		2233
		2234	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		2235	will create in parallel.
		2236
		2237	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		2238
		2239	The default value for the C<max_outstanding> parameter for the default DNS
		2240	resolver - this is the maximum number of parallel DNS requests that are
		2241	sent to the DNS server.
		2242
		2243	=item C<PERL_ANYEVENT_MAX_SIGNAL_LATENCY>
		2244
		2245	Perl has inherently racy signal handling (you can basically choose between
		2246	losing signals and memory corruption) - pure perl event loops (including
		2247	C<AnyEvent::Loop>, when C<Async::Interrupt> isn't available) therefore
		2248	have to poll regularly to avoid losing signals.
		2249
		2250	Some event loops are racy, but don't poll regularly, and some event loops
		2251	are written in C but are still racy. For those event loops, AnyEvent
		2252	installs a timer that regularly wakes up the event loop.
		2253
		2254	By default, the interval for this timer is C<10> seconds, but you can
		2255	override this delay with this environment variable (or by setting
		2256	the C<$AnyEvent::MAX_SIGNAL_LATENCY> variable before creating signal
		2257	watchers).
		2258
		2259	Lower values increase CPU (and energy) usage, higher values can introduce
		2260	long delays when reaping children or waiting for signals.
		2261
		2262	The L<AnyEvent::Async> module, if available, will be used to avoid this
		2263	polling (with most event loops).
		2264
		2265	=item C<PERL_ANYEVENT_RESOLV_CONF>
		2266
		2267	The absolute path to a F<resolv.conf>-style file to use instead of
		2268	F</etc/resolv.conf> (or the OS-specific configuration) in the default
		2269	resolver, or the empty string to select the default configuration.
		2270
		2271	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		2272
		2273	When neither C<ca_file> nor C<ca_path> was specified during
		2274	L<AnyEvent::TLS> context creation, and either of these environment
		2275	variables are nonempty, they will be used to specify CA certificate
		2276	locations instead of a system-dependent default.
		2277
		2278	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		2279
		2280	When these are set to C<1>, then the respective modules are not
		2281	loaded. Mostly good for testing AnyEvent itself.
		2282
		2283	=back
661		2284
662	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	2285	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
663		2286
664	This is an advanced topic that you do not normally need to use AnyEvent in	2287	This is an advanced topic that you do not normally need to use AnyEvent in
665	a module. This section is only of use to event loop authors who want to	2288	a module. This section is only of use to event loop authors who want to
…		…
699		2322
700	I<rxvt-unicode> also cheats a bit by not providing blocking access to	2323	I<rxvt-unicode> also cheats a bit by not providing blocking access to
701	condition variables: code blocking while waiting for a condition will	2324	condition variables: code blocking while waiting for a condition will
702	C<die>. This still works with most modules/usages, and blocking calls must	2325	C<die>. This still works with most modules/usages, and blocking calls must
703	not be done in an interactive application, so it makes sense.	2326	not be done in an interactive application, so it makes sense.
704
705	=head1 ENVIRONMENT VARIABLES
706
707	The following environment variables are used by this module:
708
709	=over 4
710
711	=item C<PERL_ANYEVENT_VERBOSE>
712
713	By default, AnyEvent will be completely silent except in fatal
714	conditions. You can set this environment variable to make AnyEvent more
715	talkative.
716
717	When set to C<1> or higher, causes AnyEvent to warn about unexpected
718	conditions, such as not being able to load the event model specified by
719	C<PERL_ANYEVENT_MODEL>.
720
721	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
722	model it chooses.
723
724	=item C<PERL_ANYEVENT_MODEL>
725
726	This can be used to specify the event model to be used by AnyEvent, before
727	autodetection and -probing kicks in. It must be a string consisting
728	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
729	and the resulting module name is loaded and if the load was successful,
730	used as event model. If it fails to load AnyEvent will proceed with
731	autodetection and -probing.
732
733	This functionality might change in future versions.
734
735	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
736	could start your program like this:
737
738	PERL_ANYEVENT_MODEL=Perl perl ...
739
740	=back
741		2327
742	=head1 EXAMPLE PROGRAM	2328	=head1 EXAMPLE PROGRAM
743		2329
744	The following program uses an I/O watcher to read data from STDIN, a timer	2330	The following program uses an I/O watcher to read data from STDIN, a timer
745	to display a message once per second, and a condition variable to quit the	2331	to display a message once per second, and a condition variable to quit the
…		…
754	poll => 'r',	2340	poll => 'r',
755	cb => sub {	2341	cb => sub {
756	warn "io event <$_[0]>\n"; # will always output <r>	2342	warn "io event <$_[0]>\n"; # will always output <r>
757	chomp (my $input = <STDIN>); # read a line	2343	chomp (my $input = <STDIN>); # read a line
758	warn "read: $input\n"; # output what has been read	2344	warn "read: $input\n"; # output what has been read
759	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	2345	$cv->send if $input =~ /^q/i; # quit program if /^q/i
760	},	2346	},
761	);	2347	);
762		2348
763	my $time_watcher; # can only be used once
764
765	sub new_timer {
766	$timer = AnyEvent->timer (after => 1, cb => sub {	2349	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
767	warn "timeout\n"; # print 'timeout' about every second	2350	warn "timeout\n"; # print 'timeout' at most every second
768	&new_timer; # and restart the time
769	});	2351	});
770	}
771		2352
772	new_timer; # create first timer
773
774	$cv->wait; # wait until user enters /^q/i	2353	$cv->recv; # wait until user enters /^q/i
775		2354
776	=head1 REAL-WORLD EXAMPLE	2355	=head1 REAL-WORLD EXAMPLE
777		2356
778	Consider the L<Net::FCP> module. It features (among others) the following	2357	Consider the L<Net::FCP> module. It features (among others) the following
779	API calls, which are to freenet what HTTP GET requests are to http:	2358	API calls, which are to freenet what HTTP GET requests are to http:
…		…
829	syswrite $txn->{fh}, $txn->{request}	2408	syswrite $txn->{fh}, $txn->{request}
830	or die "connection or write error";	2409	or die "connection or write error";
831	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	2410	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
832		2411
833	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	2412	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
834	result and signals any possible waiters that the request ahs finished:	2413	result and signals any possible waiters that the request has finished:
835		2414
836	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	2415	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
837		2416
838	if (end-of-file or data complete) {	2417	if (end-of-file or data complete) {
839	$txn->{result} = $txn->{buf};	2418	$txn->{result} = $txn->{buf};
840	$txn->{finished}->broadcast;	2419	$txn->{finished}->send;
841	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	2420	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
842	}	2421	}
843		2422
844	The C<result> method, finally, just waits for the finished signal (if the	2423	The C<result> method, finally, just waits for the finished signal (if the
845	request was already finished, it doesn't wait, of course, and returns the	2424	request was already finished, it doesn't wait, of course, and returns the
846	data:	2425	data:
847		2426
848	$txn->{finished}->wait;	2427	$txn->{finished}->recv;
849	return $txn->{result};	2428	return $txn->{result};
850		2429
851	The actual code goes further and collects all errors (C<die>s, exceptions)	2430	The actual code goes further and collects all errors (C<die>s, exceptions)
852	that occured during request processing. The C<result> method detects	2431	that occurred during request processing. The C<result> method detects
853	whether an exception as thrown (it is stored inside the $txn object)	2432	whether an exception as thrown (it is stored inside the $txn object)
854	and just throws the exception, which means connection errors and other	2433	and just throws the exception, which means connection errors and other
855	problems get reported tot he code that tries to use the result, not in a	2434	problems get reported to the code that tries to use the result, not in a
856	random callback.	2435	random callback.
857		2436
858	All of this enables the following usage styles:	2437	All of this enables the following usage styles:
859		2438
860	1. Blocking:	2439	1. Blocking:
…		…
888		2467
889	my $quit = AnyEvent->condvar;	2468	my $quit = AnyEvent->condvar;
890		2469
891	$fcp->txn_client_get ($url)->cb (sub {	2470	$fcp->txn_client_get ($url)->cb (sub {
892	...	2471	...
893	$quit->broadcast;	2472	$quit->send;
894	});	2473	});
895		2474
896	$quit->wait;	2475	$quit->recv;
897		2476
898		2477
899	=head1 BENCHMARKS	2478	=head1 BENCHMARKS
900		2479
901	To give you an idea of the performance and overheads that AnyEvent adds	2480	To give you an idea of the performance and overheads that AnyEvent adds
…		…
903	of various event loops I prepared some benchmarks.	2482	of various event loops I prepared some benchmarks.
904		2483
905	=head2 BENCHMARKING ANYEVENT OVERHEAD	2484	=head2 BENCHMARKING ANYEVENT OVERHEAD
906		2485
907	Here is a benchmark of various supported event models used natively and	2486	Here is a benchmark of various supported event models used natively and
908	through anyevent. The benchmark creates a lot of timers (with a zero	2487	through AnyEvent. The benchmark creates a lot of timers (with a zero
909	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,	2488	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
910	which it is), lets them fire exactly once and destroys them again.	2489	which it is), lets them fire exactly once and destroys them again.
911		2490
912	Source code for this benchmark is found as F<eg/bench> in the AnyEvent	2491	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
913	distribution.	2492	distribution. It uses the L<AE> interface, which makes a real difference
		2493	for the EV and Perl backends only.
914		2494
915	=head3 Explanation of the columns	2495	=head3 Explanation of the columns
916		2496
917	I<watcher> is the number of event watchers created/destroyed. Since	2497	I<watcher> is the number of event watchers created/destroyed. Since
918	different event models feature vastly different performances, each event	2498	different event models feature vastly different performances, each event
…		…
930	all watchers, to avoid adding memory overhead. That means closure creation	2510	all watchers, to avoid adding memory overhead. That means closure creation
931	and memory usage is not included in the figures.	2511	and memory usage is not included in the figures.
932		2512
933	I<invoke> is the time, in microseconds, used to invoke a simple	2513	I<invoke> is the time, in microseconds, used to invoke a simple
934	callback. The callback simply counts down a Perl variable and after it was	2514	callback. The callback simply counts down a Perl variable and after it was
935	invoked "watcher" times, it would C<< ->broadcast >> a condvar once to	2515	invoked "watcher" times, it would C<< ->send >> a condvar once to
936	signal the end of this phase.	2516	signal the end of this phase.
937		2517
938	I<destroy> is the time, in microseconds, that it takes to destroy a single	2518	I<destroy> is the time, in microseconds, that it takes to destroy a single
939	watcher.	2519	watcher.
940		2520
941	=head3 Results	2521	=head3 Results
942		2522
943	name watchers bytes create invoke destroy comment	2523	name watchers bytes create invoke destroy comment
944	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	2524	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
945	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	2525	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
946	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	2526	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
947	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	2527	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
948	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	2528	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
949	Event/Any 16000 936 39.17 33.63 1.43 Event + AnyEvent watchers	2529	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
		2530	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
		2531	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
950	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	2532	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
951	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	2533	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
952	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	2534	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
953	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	2535	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
954		2536
955	=head3 Discussion	2537	=head3 Discussion
956		2538
957	The benchmark does I<not> measure scalability of the event loop very	2539	The benchmark does I<not> measure scalability of the event loop very
958	well. For example, a select-based event loop (such as the pure perl one)	2540	well. For example, a select-based event loop (such as the pure perl one)
…		…
970	benchmark machine, handling an event takes roughly 1600 CPU cycles with	2552	benchmark machine, handling an event takes roughly 1600 CPU cycles with
971	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU	2553	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
972	cycles with POE.	2554	cycles with POE.
973		2555
974	C<EV> is the sole leader regarding speed and memory use, which are both	2556	C<EV> is the sole leader regarding speed and memory use, which are both
975	maximal/minimal, respectively. Even when going through AnyEvent, it uses	2557	maximal/minimal, respectively. When using the L<AE> API there is zero
		2558	overhead (when going through the AnyEvent API create is about 5-6 times
		2559	slower, with other times being equal, so still uses far less memory than
976	far less memory than any other event loop and is still faster than Event	2560	any other event loop and is still faster than Event natively).
977	natively.
978		2561
979	The pure perl implementation is hit in a few sweet spots (both the	2562	The pure perl implementation is hit in a few sweet spots (both the
980	constant timeout and the use of a single fd hit optimisations in the perl	2563	constant timeout and the use of a single fd hit optimisations in the perl
981	interpreter and the backend itself). Nevertheless this shows that it	2564	interpreter and the backend itself). Nevertheless this shows that it
982	adds very little overhead in itself. Like any select-based backend its	2565	adds very little overhead in itself. Like any select-based backend its
983	performance becomes really bad with lots of file descriptors (and few of	2566	performance becomes really bad with lots of file descriptors (and few of
984	them active), of course, but this was not subject of this benchmark.	2567	them active), of course, but this was not subject of this benchmark.
985		2568
986	The C<Event> module has a relatively high setup and callback invocation	2569	The C<Event> module has a relatively high setup and callback invocation
987	cost, but overall scores in on the third place.	2570	cost, but overall scores in on the third place.
		2571
		2572	C<IO::Async> performs admirably well, about on par with C<Event>, even
		2573	when using its pure perl backend.
988		2574
989	C<Glib>'s memory usage is quite a bit higher, but it features a	2575	C<Glib>'s memory usage is quite a bit higher, but it features a
990	faster callback invocation and overall ends up in the same class as	2576	faster callback invocation and overall ends up in the same class as
991	C<Event>. However, Glib scales extremely badly, doubling the number of	2577	C<Event>. However, Glib scales extremely badly, doubling the number of
992	watchers increases the processing time by more than a factor of four,	2578	watchers increases the processing time by more than a factor of four,
…		…
1000	file descriptor is dup()ed for each watcher. This shows that the dup()	2586	file descriptor is dup()ed for each watcher. This shows that the dup()
1001	employed by some adaptors is not a big performance issue (it does incur a	2587	employed by some adaptors is not a big performance issue (it does incur a
1002	hidden memory cost inside the kernel which is not reflected in the figures	2588	hidden memory cost inside the kernel which is not reflected in the figures
1003	above).	2589	above).
1004		2590
1005	C<POE>, regardless of underlying event loop (whether using its pure	2591	C<POE>, regardless of underlying event loop (whether using its pure perl
1006	perl select-based backend or the Event module, the POE-EV backend	2592	select-based backend or the Event module, the POE-EV backend couldn't
1007	couldn't be tested because it wasn't working) shows abysmal performance	2593	be tested because it wasn't working) shows abysmal performance and
1008	and memory usage: Watchers use almost 30 times as much memory as	2594	memory usage with AnyEvent: Watchers use almost 30 times as much memory
1009	EV watchers, and 10 times as much memory as Event (the high memory	2595	as EV watchers, and 10 times as much memory as Event (the high memory
1010	requirements are caused by requiring a session for each watcher). Watcher	2596	requirements are caused by requiring a session for each watcher). Watcher
1011	invocation speed is almost 900 times slower than with AnyEvent's pure perl	2597	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		2598	implementation.
		2599
1012	implementation. The design of the POE adaptor class in AnyEvent can not	2600	The design of the POE adaptor class in AnyEvent can not really account
1013	really account for this, as session creation overhead is small compared	2601	for the performance issues, though, as session creation overhead is
1014	to execution of the state machine, which is coded pretty optimally within	2602	small compared to execution of the state machine, which is coded pretty
1015	L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow.	2603	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		2604	using multiple sessions is not a good approach, especially regarding
		2605	memory usage, even the author of POE could not come up with a faster
		2606	design).
1016		2607
1017	=head3 Summary	2608	=head3 Summary
1018		2609
1019	=over 4	2610	=over 4
1020		2611
…		…
1022	(even when used without AnyEvent), but most event loops have acceptable	2613	(even when used without AnyEvent), but most event loops have acceptable
1023	performance with or without AnyEvent.	2614	performance with or without AnyEvent.
1024		2615
1025	=item * The overhead AnyEvent adds is usually much smaller than the overhead of	2616	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
1026	the actual event loop, only with extremely fast event loops such as EV	2617	the actual event loop, only with extremely fast event loops such as EV
1027	adds AnyEvent significant overhead.	2618	does AnyEvent add significant overhead.
1028		2619
1029	=item * You should avoid POE like the plague if you want performance or	2620	=item * You should avoid POE like the plague if you want performance or
1030	reasonable memory usage.	2621	reasonable memory usage.
1031		2622
1032	=back	2623	=back
1033		2624
1034	=head2 BENCHMARKING THE LARGE SERVER CASE	2625	=head2 BENCHMARKING THE LARGE SERVER CASE
1035		2626
1036	This benchmark atcually benchmarks the event loop itself. It works by	2627	This benchmark actually benchmarks the event loop itself. It works by
1037	creating a number of "servers": each server consists of a socketpair, a	2628	creating a number of "servers": each server consists of a socket pair, a
1038	timeout watcher that gets reset on activity (but never fires), and an I/O	2629	timeout watcher that gets reset on activity (but never fires), and an I/O
1039	watcher waiting for input on one side of the socket. Each time the socket	2630	watcher waiting for input on one side of the socket. Each time the socket
1040	watcher reads a byte it will write that byte to a random other "server".	2631	watcher reads a byte it will write that byte to a random other "server".
1041		2632
1042	The effect is that there will be a lot of I/O watchers, only part of which	2633	The effect is that there will be a lot of I/O watchers, only part of which
1043	are active at any one point (so there is a constant number of active	2634	are active at any one point (so there is a constant number of active
1044	fds for each loop iterstaion, but which fds these are is random). The	2635	fds for each loop iteration, but which fds these are is random). The
1045	timeout is reset each time something is read because that reflects how	2636	timeout is reset each time something is read because that reflects how
1046	most timeouts work (and puts extra pressure on the event loops).	2637	most timeouts work (and puts extra pressure on the event loops).
1047		2638
1048	In this benchmark, we use 10000 socketpairs (20000 sockets), of which 100	2639	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
1049	(1%) are active. This mirrors the activity of large servers with many	2640	(1%) are active. This mirrors the activity of large servers with many
1050	connections, most of which are idle at any one point in time.	2641	connections, most of which are idle at any one point in time.
1051		2642
1052	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent	2643	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
1053	distribution.	2644	distribution. It uses the L<AE> interface, which makes a real difference
		2645	for the EV and Perl backends only.
1054		2646
1055	=head3 Explanation of the columns	2647	=head3 Explanation of the columns
1056		2648
1057	I<sockets> is the number of sockets, and twice the number of "servers" (as	2649	I<sockets> is the number of sockets, and twice the number of "servers" (as
1058	each server has a read and write socket end).	2650	each server has a read and write socket end).
1059		2651
1060	I<create> is the time it takes to create a socketpair (which is	2652	I<create> is the time it takes to create a socket pair (which is
1061	nontrivial) and two watchers: an I/O watcher and a timeout watcher.	2653	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
1062		2654
1063	I<request>, the most important value, is the time it takes to handle a	2655	I<request>, the most important value, is the time it takes to handle a
1064	single "request", that is, reading the token from the pipe and forwarding	2656	single "request", that is, reading the token from the pipe and forwarding
1065	it to another server. This includes deleting the old timeout and creating	2657	it to another server. This includes deleting the old timeout and creating
1066	a new one that moves the timeout into the future.	2658	a new one that moves the timeout into the future.
1067		2659
1068	=head3 Results	2660	=head3 Results
1069		2661
1070	name sockets create request	2662	name sockets create request
1071	EV 20000 69.01 11.16	2663	EV 20000 62.66 7.99
1072	Perl 20000 75.28 112.76	2664	Perl 20000 68.32 32.64
1073	Event 20000 212.62 257.32	2665	IOAsync 20000 174.06 101.15 epoll
1074	Glib 20000 651.16 1896.30	2666	IOAsync 20000 174.67 610.84 poll
		2667	Event 20000 202.69 242.91
		2668	Glib 20000 557.01 1689.52
1075	POE 20000 349.67 12317.24 uses POE::Loop::Event	2669	POE 20000 341.54 12086.32 uses POE::Loop::Event
1076		2670
1077	=head3 Discussion	2671	=head3 Discussion
1078		2672
1079	This benchmark I<does> measure scalability and overall performance of the	2673	This benchmark I<does> measure scalability and overall performance of the
1080	particular event loop.	2674	particular event loop.
…		…
1082	EV is again fastest. Since it is using epoll on my system, the setup time	2676	EV is again fastest. Since it is using epoll on my system, the setup time
1083	is relatively high, though.	2677	is relatively high, though.
1084		2678
1085	Perl surprisingly comes second. It is much faster than the C-based event	2679	Perl surprisingly comes second. It is much faster than the C-based event
1086	loops Event and Glib.	2680	loops Event and Glib.
		2681
		2682	IO::Async performs very well when using its epoll backend, and still quite
		2683	good compared to Glib when using its pure perl backend.
1087		2684
1088	Event suffers from high setup time as well (look at its code and you will	2685	Event suffers from high setup time as well (look at its code and you will
1089	understand why). Callback invocation also has a high overhead compared to	2686	understand why). Callback invocation also has a high overhead compared to
1090	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event	2687	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
1091	uses select or poll in basically all documented configurations.	2688	uses select or poll in basically all documented configurations.
…		…
1099		2696
1100	=head3 Summary	2697	=head3 Summary
1101		2698
1102	=over 4	2699	=over 4
1103		2700
1104	=item * The pure perl implementation performs extremely well, considering	2701	=item * The pure perl implementation performs extremely well.
1105	that it uses select.
1106		2702
1107	=item * Avoid Glib or POE in large projects where performance matters.	2703	=item * Avoid Glib or POE in large projects where performance matters.
1108		2704
1109	=back	2705	=back
1110		2706
…		…
1123		2719
1124	=head3 Results	2720	=head3 Results
1125		2721
1126	name sockets create request	2722	name sockets create request
1127	EV 16 20.00 6.54	2723	EV 16 20.00 6.54
		2724	Perl 16 25.75 12.62
1128	Event 16 81.27 35.86	2725	Event 16 81.27 35.86
1129	Glib 16 32.63 15.48	2726	Glib 16 32.63 15.48
1130	Perl 16 24.62 162.37
1131	POE 16 261.87 276.28 uses POE::Loop::Event	2727	POE 16 261.87 276.28 uses POE::Loop::Event
1132		2728
1133	=head3 Discussion	2729	=head3 Discussion
1134		2730
1135	The benchmark tries to test the performance of a typical small	2731	The benchmark tries to test the performance of a typical small
…		…
1139	speed most when you have lots of watchers, not when you only have a few of	2735	speed most when you have lots of watchers, not when you only have a few of
1140	them).	2736	them).
1141		2737
1142	EV is again fastest.	2738	EV is again fastest.
1143		2739
1144	The C-based event loops Event and Glib come in second this time, as the	2740	Perl again comes second. It is noticeably faster than the C-based event
1145	overhead of running an iteration is much smaller in C than in Perl (little	2741	loops Event and Glib, although the difference is too small to really
1146	code to execute in the inner loop, and perl's function calling overhead is	2742	matter.
1147	high, and updating all the data structures is costly).
1148
1149	The pure perl event loop is much slower, but still competitive.
1150		2743
1151	POE also performs much better in this case, but is is still far behind the	2744	POE also performs much better in this case, but is is still far behind the
1152	others.	2745	others.
1153		2746
1154	=head3 Summary	2747	=head3 Summary
…		…
1158	=item * C-based event loops perform very well with small number of	2751	=item * C-based event loops perform very well with small number of
1159	watchers, as the management overhead dominates.	2752	watchers, as the management overhead dominates.
1160		2753
1161	=back	2754	=back
1162		2755
		2756	=head2 THE IO::Lambda BENCHMARK
		2757
		2758	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2759	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2760	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2761	shouldn't come as a surprise to anybody). As such, the benchmark is
		2762	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2763	very optimal. But how would AnyEvent compare when used without the extra
		2764	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2765
		2766	The benchmark itself creates an echo-server, and then, for 500 times,
		2767	connects to the echo server, sends a line, waits for the reply, and then
		2768	creates the next connection. This is a rather bad benchmark, as it doesn't
		2769	test the efficiency of the framework or much non-blocking I/O, but it is a
		2770	benchmark nevertheless.
		2771
		2772	name runtime
		2773	Lambda/select 0.330 sec
		2774	+ optimized 0.122 sec
		2775	Lambda/AnyEvent 0.327 sec
		2776	+ optimized 0.138 sec
		2777	Raw sockets/select 0.077 sec
		2778	POE/select, components 0.662 sec
		2779	POE/select, raw sockets 0.226 sec
		2780	POE/select, optimized 0.404 sec
		2781
		2782	AnyEvent/select/nb 0.085 sec
		2783	AnyEvent/EV/nb 0.068 sec
		2784	+state machine 0.134 sec
		2785
		2786	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2787	benchmarks actually make blocking connects and use 100% blocking I/O,
		2788	defeating the purpose of an event-based solution. All of the newly
		2789	written AnyEvent benchmarks use 100% non-blocking connects (using
		2790	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2791	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2792	generally require a lot more bookkeeping and event handling than blocking
		2793	connects (which involve a single syscall only).
		2794
		2795	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2796	offers similar expressive power as POE and IO::Lambda, using conventional
		2797	Perl syntax. This means that both the echo server and the client are 100%
		2798	non-blocking, further placing it at a disadvantage.
		2799
		2800	As you can see, the AnyEvent + EV combination even beats the
		2801	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2802	backend easily beats IO::Lambda and POE.
		2803
		2804	And even the 100% non-blocking version written using the high-level (and
		2805	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda
		2806	higher level ("unoptimised") abstractions by a large margin, even though
		2807	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
		2808
		2809	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2810	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2811	part of the IO::Lambda distribution and were used without any changes.
		2812
		2813
		2814	=head1 SIGNALS
		2815
		2816	AnyEvent currently installs handlers for these signals:
		2817
		2818	=over 4
		2819
		2820	=item SIGCHLD
		2821
		2822	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2823	emulation for event loops that do not support them natively. Also, some
		2824	event loops install a similar handler.
		2825
		2826	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2827	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2828
		2829	=item SIGPIPE
		2830
		2831	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2832	when AnyEvent gets loaded.
		2833
		2834	The rationale for this is that AnyEvent users usually do not really depend
		2835	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2836	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2837	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2838	some random socket.
		2839
		2840	The rationale for installing a no-op handler as opposed to ignoring it is
		2841	that this way, the handler will be restored to defaults on exec.
		2842
		2843	Feel free to install your own handler, or reset it to defaults.
		2844
		2845	=back
		2846
		2847	=cut
		2848
		2849	undef $SIG{CHLD}
		2850	if $SIG{CHLD} eq 'IGNORE';
		2851
		2852	$SIG{PIPE} = sub { }
		2853	unless defined $SIG{PIPE};
		2854
		2855	=head1 RECOMMENDED/OPTIONAL MODULES
		2856
		2857	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2858	its built-in modules) are required to use it.
		2859
		2860	That does not mean that AnyEvent won't take advantage of some additional
		2861	modules if they are installed.
		2862
		2863	This section explains which additional modules will be used, and how they
		2864	affect AnyEvent's operation.
		2865
		2866	=over 4
		2867
		2868	=item L<Async::Interrupt>
		2869
		2870	This slightly arcane module is used to implement fast signal handling: To
		2871	my knowledge, there is no way to do completely race-free and quick
		2872	signal handling in pure perl. To ensure that signals still get
		2873	delivered, AnyEvent will start an interval timer to wake up perl (and
		2874	catch the signals) with some delay (default is 10 seconds, look for
		2875	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2876
		2877	If this module is available, then it will be used to implement signal
		2878	catching, which means that signals will not be delayed, and the event loop
		2879	will not be interrupted regularly, which is more efficient (and good for
		2880	battery life on laptops).
		2881
		2882	This affects not just the pure-perl event loop, but also other event loops
		2883	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2884
		2885	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2886	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2887	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2888	does nothing for those backends.
		2889
		2890	=item L<EV>
		2891
		2892	This module isn't really "optional", as it is simply one of the backend
		2893	event loops that AnyEvent can use. However, it is simply the best event
		2894	loop available in terms of features, speed and stability: It supports
		2895	the AnyEvent API optimally, implements all the watcher types in XS, does
		2896	automatic timer adjustments even when no monotonic clock is available,
		2897	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2898	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2899	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2900
		2901	If you only use backends that rely on another event loop (e.g. C<Tk>),
		2902	then this module will do nothing for you.
		2903
		2904	=item L<Guard>
		2905
		2906	The guard module, when used, will be used to implement
		2907	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2908	lot less memory), but otherwise doesn't affect guard operation much. It is
		2909	purely used for performance.
		2910
		2911	=item L<JSON> and L<JSON::XS>
		2912
		2913	One of these modules is required when you want to read or write JSON data
		2914	via L<AnyEvent::Handle>. L<JSON> is also written in pure-perl, but can take
		2915	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2916
		2917	=item L<Net::SSLeay>
		2918
		2919	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2920	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2921	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2922
		2923	=item L<Time::HiRes>
		2924
		2925	This module is part of perl since release 5.008. It will be used when the
		2926	chosen event library does not come with a timing source of its own. The
		2927	pure-perl event loop (L<AnyEvent::Loop>) will additionally load it to
		2928	try to use a monotonic clock for timing stability.
		2929
		2930	=back
		2931
1163		2932
1164	=head1 FORK	2933	=head1 FORK
1165		2934
1166	Most event libraries are not fork-safe. The ones who are usually are	2935	Most event libraries are not fork-safe. The ones who are usually are
1167	because they are so inefficient. Only L<EV> is fully fork-aware.	2936	because they rely on inefficient but fork-safe C<select> or C<poll> calls
		2937	- higher performance APIs such as BSD's kqueue or the dreaded Linux epoll
		2938	are usually badly thought-out hacks that are incompatible with fork in
		2939	one way or another. Only L<EV> is fully fork-aware and ensures that you
		2940	continue event-processing in both parent and child (or both, if you know
		2941	what you are doing).
		2942
		2943	This means that, in general, you cannot fork and do event processing in
		2944	the child if the event library was initialised before the fork (which
		2945	usually happens when the first AnyEvent watcher is created, or the library
		2946	is loaded).
1168		2947
1169	If you have to fork, you must either do so I<before> creating your first	2948	If you have to fork, you must either do so I<before> creating your first
1170	watcher OR you must not use AnyEvent at all in the child.	2949	watcher OR you must not use AnyEvent at all in the child OR you must do
		2950	something completely out of the scope of AnyEvent.
		2951
		2952	The problem of doing event processing in the parent I<and> the child
		2953	is much more complicated: even for backends that I<are> fork-aware or
		2954	fork-safe, their behaviour is not usually what you want: fork clones all
		2955	watchers, that means all timers, I/O watchers etc. are active in both
		2956	parent and child, which is almost never what you want. USing C<exec>
		2957	to start worker children from some kind of manage rprocess is usually
		2958	preferred, because it is much easier and cleaner, at the expense of having
		2959	to have another binary.
1171		2960
1172		2961
1173	=head1 SECURITY CONSIDERATIONS	2962	=head1 SECURITY CONSIDERATIONS
1174		2963
1175	AnyEvent can be forced to load any event model via	2964	AnyEvent can be forced to load any event model via
…		…
1180	specified in the variable.	2969	specified in the variable.
1181		2970
1182	You can make AnyEvent completely ignore this variable by deleting it	2971	You can make AnyEvent completely ignore this variable by deleting it
1183	before the first watcher gets created, e.g. with a C<BEGIN> block:	2972	before the first watcher gets created, e.g. with a C<BEGIN> block:
1184		2973
1185	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	2974	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1186		2975
1187	use AnyEvent;	2976	use AnyEvent;
		2977
		2978	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		2979	be used to probe what backend is used and gain other information (which is
		2980	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2981	$ENV{PERL_ANYEVENT_STRICT}.
		2982
		2983	Note that AnyEvent will remove I<all> environment variables starting with
		2984	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2985	enabled.
		2986
		2987
		2988	=head1 BUGS
		2989
		2990	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2991	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2992	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2993	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2994	pronounced).
1188		2995
1189		2996
1190	=head1 SEE ALSO	2997	=head1 SEE ALSO
1191		2998
1192	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	2999	Tutorial/Introduction: L<AnyEvent::Intro>.
1193	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,
1194	L<Event::Lib>, L<Qt>, L<POE>.
1195		3000
1196	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	3001	FAQ: L<AnyEvent::FAQ>.
		3002
		3003	Utility functions: L<AnyEvent::Util> (misc. grab-bag), L<AnyEvent::Log>
		3004	(simply logging).
		3005
		3006	Development/Debugging: L<AnyEvent::Strict> (stricter checking),
		3007	L<AnyEvent::Debug> (interactive shell, watcher tracing).
		3008
		3009	Supported event modules: L<AnyEvent::Loop>, L<EV>, L<EV::Glib>,
		3010	L<Glib::EV>, L<Event>, L<Glib::Event>, L<Glib>, L<Tk>, L<Event::Lib>,
		3011	L<Qt>, L<POE>, L<FLTK>.
		3012
		3013	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
		3014	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
		3015	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1197	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,	3016	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>, L<Anyevent::Impl::Irssi>,
1198	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,	3017	L<AnyEvent::Impl::FLTK>.
1199	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.
1200		3018
		3019	Non-blocking handles, pipes, stream sockets, TCP clients and
		3020	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
		3021
		3022	Asynchronous File I/O: L<AnyEvent::IO>.
		3023
		3024	Asynchronous DNS: L<AnyEvent::DNS>.
		3025
		3026	Thread support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
		3027
1201	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	3028	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::IRC>,
		3029	L<AnyEvent::HTTP>.
1202		3030
1203		3031
1204	=head1 AUTHOR	3032	=head1 AUTHOR
1205		3033
1206	Marc Lehmann <schmorp@schmorp.de>	3034	Marc Lehmann <schmorp@schmorp.de>
1207	http://home.schmorp.de/	3035	http://anyevent.schmorp.de
1208		3036
1209	=cut	3037	=cut
1210		3038
1211	1	3039	1
1212		3040

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