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Revision 1.418 by root, Tue Jan 21 16:48:34 2014 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent - provide framework for multiple event loops	3	AnyEvent - the DBI of event loop programming
4		4
5	EV, Event, Coro::EV, Coro::Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event loops	5	EV, Event, Glib, Tk, 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<Tk>, L<AnyEvent::Impl::Perl>, 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 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 IO WATCHERS	188	=head2 I/O WATCHERS
		189
		190	$w = AnyEvent->io (
		191	fh => <filehandle_or_fileno>,
		192	poll => <"r" or "w">,
		193	cb => <callback>,
		194	);
142		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 for	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	events. C<poll> must be a string that is either C<r> or C<w>, which	206	C<poll> must be a string that is either C<r> or C<w>, which creates a
148	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	As long as the I/O watcher exists it will keep the file descriptor or a	211	Although the callback might get passed parameters, their value and
153	copy of it alive/open.	212	presence is undefined and you cannot rely on them. Portable AnyEvent
		213	callbacks cannot use arguments passed to I/O watcher callbacks.
154		214
		215	The I/O watcher might use the underlying file descriptor or a copy of it.
155	It is not allowed to close a file handle as long as any watcher is active	216	You must not close a file handle as long as any watcher is active on the
156	on the underlying file descriptor.	217	underlying file descriptor.
157		218
158	Some event loops issue spurious readyness notifications, so you should	219	Some event loops issue spurious readiness notifications, so you should
159	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
160	handles.	221	handles.
161		222
162	Example:
163
164	# 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
165	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	226	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
166	chomp (my $input = <STDIN>);	227	chomp (my $input = <STDIN>);
167	warn "read: $input\n";	228	warn "read: $input\n";
168	undef $w;	229	undef $w;
169	});	230	});
170		231
171	=head2 TIME WATCHERS	232	=head2 TIME WATCHERS
172		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
173	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 >>
174	method with the following mandatory arguments:	243	method with the following mandatory arguments:
175		244
176	C<after> specifies after how many seconds (fractional values are	245	C<after> specifies after how many seconds (fractional values are
177	supported) should the timer activate. C<cb> the callback to invoke in that	246	supported) the callback should be invoked. C<cb> is the callback to invoke
178	case.	247	in that case.
179		248
180	The timer callback will be invoked at most once: if you want a repeating	249	Although the callback might get passed parameters, their value and
181	timer you have to create a new watcher (this is a limitation by both Tk	250	presence is undefined and you cannot rely on them. Portable AnyEvent
182	and Glib).	251	callbacks cannot use arguments passed to time watcher callbacks.
183		252
184	Example:	253	The callback will normally be invoked only once. If you specify another
		254	parameter, C<interval>, as a strictly positive number (> 0), then the
		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.
185		258
		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.
		262
186	# fire an event after 7.7 seconds	263	Example: fire an event after 7.7 seconds.
		264
187	my $w = AnyEvent->timer (after => 7.7, cb => sub {	265	my $w = AnyEvent->timer (after => 7.7, cb => sub {
188	warn "timeout\n";	266	warn "timeout\n";
189	});	267	});
190		268
191	# to cancel the timer:	269	# to cancel the timer:
192	undef $w;	270	undef $w;
193		271
194	Example 2:
195
196	# 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.
197	my $w;
198		273
199	my $cb = sub {
200	# cancel the old timer while creating a new one
201	$w = AnyEvent->timer (after => 1, cb => $cb);	274	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		275	warn "timeout\n";
202	};	276	});
203
204	# start the "loop" by creating the first watcher
205	$w = AnyEvent->timer (after => 0.5, cb => $cb);
206		277
207	=head3 TIMING ISSUES	278	=head3 TIMING ISSUES
208		279
209	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
210	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
…		…
212		283
213	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
214	use absolute time internally. This makes a difference when your clock	285	use absolute time internally. This makes a difference when your clock
215	"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
216	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
217	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.
218		289
219	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
220	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
221	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)
222	timers.	293	timers.
223		294
224	AnyEvent always prefers relative timers, if available, matching the	295	AnyEvent always prefers relative timers, if available, matching the
225	AnyEvent API.	296	AnyEvent API.
226		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
227	=head2 SIGNAL WATCHERS	383	=head2 SIGNAL WATCHERS
228		384
		385	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		386
229	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
230	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
231	be invoked whenever a signal occurs.	389	callback to be invoked whenever a signal occurs.
232		390
		391	Although the callback might get passed parameters, their value and
		392	presence is undefined and you cannot rely on them. Portable AnyEvent
		393	callbacks cannot use arguments passed to signal watcher callbacks.
		394
233	Multiple signal occurances can be clumped together into one callback	395	Multiple signal occurrences can be clumped together into one callback
234	invocation, and callback invocation will be synchronous. synchronous means	396	invocation, and callback invocation will be synchronous. Synchronous means
235	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,
236	but it is guarenteed not to interrupt any other callbacks.	398	but it is guaranteed not to interrupt any other callbacks.
237		399
238	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
239	between multiple watchers.	401	between multiple watchers, and AnyEvent will ensure that signals will not
		402	interrupt your program at bad times.
240		403
241	This watcher might use C<%SIG>, so programs overwriting those signals	404	This watcher might use C<%SIG> (depending on the event loop used),
242	directly will likely not work correctly.	405	so programs overwriting those signals directly will likely not work
		406	correctly.
243		407
244	Example: exit on SIGINT	408	Example: exit on SIGINT
245		409
246	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	410	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
247		411
		412	=head3 Restart Behaviour
		413
		414	While restart behaviour is up to the event loop implementation, most will
		415	not restart syscalls (that includes L<Async::Interrupt> and AnyEvent's
		416	pure perl implementation).
		417
		418	=head3 Safe/Unsafe Signals
		419
		420	Perl signals can be either "safe" (synchronous to opcode handling)
		421	or "unsafe" (asynchronous) - the former might delay signal delivery
		422	indefinitely, the latter might corrupt your memory.
		423
		424	AnyEvent signal handlers are, in addition, synchronous to the event loop,
		425	i.e. they will not interrupt your running perl program but will only be
		426	called as part of the normal event handling (just like timer, I/O etc.
		427	callbacks, too).
		428
		429	=head3 Signal Races, Delays and Workarounds
		430
		431	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support
		432	attaching callbacks to signals in a generic way, which is a pity,
		433	as you cannot do race-free signal handling in perl, requiring
		434	C libraries for this. AnyEvent will try to do its best, which
		435	means in some cases, signals will be delayed. The maximum time
		436	a signal might be delayed is 10 seconds by default, but can
		437	be overriden via C<$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
248	=head2 CHILD PROCESS WATCHERS	447	=head2 CHILD PROCESS WATCHERS
249		448
		449	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		450
250	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.
251		452
252	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,
253	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
254	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
255	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
256	and exit status (as returned by waitpid).	457	(stopped/continued).
257		458
258	Example: wait for pid 1333	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.
259		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).
		467
		468	There is a slight catch to child watchers, however: you usually start them
		469	I<after> the child process was created, and this means the process could
		470	have exited already (and no SIGCHLD will be sent anymore).
		471
		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
		474	that I<do> handle this correctly, they usually need to be loaded before
		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.
		478
		479	This means you cannot create a child watcher as the very first
		480	thing in an AnyEvent program, you I<have> to create at least one
		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.
		487
		488	Example: fork a process and wait for it
		489
		490	my $done = AnyEvent->condvar;
		491
		492	# this forks and immediately calls exit in the child. this
		493	# normally has all sorts of bad consequences for your parent,
		494	# so take this as an example only. always fork and exec,
		495	# or call POSIX::_exit, in real code.
		496	my $pid = fork or exit 5;
		497
260	my $w = AnyEvent->child (	498	my $w = AnyEvent->child (
261	pid => 1333,	499	pid => $pid,
262	cb => sub {	500	cb => sub {
263	my ($pid, $status) = @_;	501	my ($pid, $status) = @_;
264	warn "pid $pid exited with status $status";	502	warn "pid $pid exited with status $status";
		503	$done->send;
265	},	504	},
266	);	505	);
		506
		507	# do something else, then wait for process exit
		508	$done->recv;
		509
		510	=head2 IDLE WATCHERS
		511
		512	$w = AnyEvent->idle (cb => <callback>);
		513
		514	This will repeatedly invoke the callback after the process becomes idle,
		515	until either the watcher is destroyed or new events have been detected.
		516
		517	Idle watchers are useful when there is a need to do something, but it
		518	is not so important (or wise) to do it instantly. The callback will be
		519	invoked only when there is "nothing better to do", which is usually
		520	defined as "all outstanding events have been handled and no new events
		521	have been detected". That means that idle watchers ideally get invoked
		522	when the event loop has just polled for new events but none have been
		523	detected. Instead of blocking to wait for more events, the idle watchers
		524	will be invoked.
		525
		526	Unfortunately, most event loops do not really support idle watchers (only
		527	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		528	will simply call the callback "from time to time".
		529
		530	Example: read lines from STDIN, but only process them when the
		531	program is otherwise idle:
		532
		533	my @lines; # read data
		534	my $idle_w;
		535	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		536	push @lines, scalar <STDIN>;
		537
		538	# start an idle watcher, if not already done
		539	$idle_w ||= AnyEvent->idle (cb => sub {
		540	# handle only one line, when there are lines left
		541	if (my $line = shift @lines) {
		542	print "handled when idle: $line";
		543	} else {
		544	# otherwise disable the idle watcher again
		545	undef $idle_w;
		546	}
		547	});
		548	});
267		549
268	=head2 CONDITION VARIABLES	550	=head2 CONDITION VARIABLES
269		551
		552	$cv = AnyEvent->condvar;
		553
		554	$cv->send (<list>);
		555	my @res = $cv->recv;
		556
		557	If you are familiar with some event loops you will know that all of them
		558	require you to run some blocking "loop", "run" or similar function that
		559	will actively watch for new events and call your callbacks.
		560
		561	AnyEvent is slightly different: it expects somebody else to run the event
		562	loop and will only block when necessary (usually when told by the user).
		563
		564	The tool to do that is called a "condition variable", so called because
		565	they represent a condition that must become true.
		566
		567	Now is probably a good time to look at the examples further below.
		568
270	Condition variables can be created by calling the C<< AnyEvent->condvar >>	569	Condition variables can be created by calling the C<< AnyEvent->condvar
271	method without any arguments.	570	>> method, usually without arguments. The only argument pair allowed is
		571	C<cb>, which specifies a callback to be called when the condition variable
		572	becomes true, with the condition variable as the first argument (but not
		573	the results).
272		574
273	A condition variable waits for a condition - precisely that the C<<	575	After creation, the condition variable is "false" until it becomes "true"
274	->broadcast >> method has been called.	576	by calling the C<send> method (or calling the condition variable as if it
		577	were a callback, read about the caveats in the description for the C<<
		578	->send >> method).
275		579
276	They are very useful to signal that a condition has been fulfilled, for	580	Since condition variables are the most complex part of the AnyEvent API, here are
		581	some different mental models of what they are - pick the ones you can connect to:
		582
		583	=over 4
		584
		585	=item * Condition variables are like callbacks - you can call them (and pass them instead
		586	of callbacks). Unlike callbacks however, you can also wait for them to be called.
		587
		588	=item * Condition variables are signals - one side can emit or send them,
		589	the other side can wait for them, or install a handler that is called when
		590	the signal fires.
		591
		592	=item * Condition variables are like "Merge Points" - points in your program
		593	where you merge multiple independent results/control flows into one.
		594
		595	=item * Condition variables represent a transaction - functions that start
		596	some kind of transaction can return them, leaving the caller the choice
		597	between waiting in a blocking fashion, or setting a callback.
		598
		599	=item * Condition variables represent future values, or promises to deliver
		600	some result, long before the result is available.
		601
		602	=back
		603
		604	Condition variables are very useful to signal that something has finished,
277	example, if you write a module that does asynchronous http requests,	605	for example, if you write a module that does asynchronous http requests,
278	then a condition variable would be the ideal candidate to signal the	606	then a condition variable would be the ideal candidate to signal the
279	availability of results.	607	availability of results. The user can either act when the callback is
		608	called or can synchronously C<< ->recv >> for the results.
280		609
281	You can also use condition variables to block your main program until	610	You can also use them to simulate traditional event loops - for example,
282	an event occurs - for example, you could C<< ->wait >> in your main	611	you can block your main program until an event occurs - for example, you
283	program until the user clicks the Quit button in your app, which would C<<	612	could C<< ->recv >> in your main program until the user clicks the Quit
284	->broadcast >> the "quit" event.	613	button of your app, which would C<< ->send >> the "quit" event.
285		614
286	Note that condition variables recurse into the event loop - if you have	615	Note that condition variables recurse into the event loop - if you have
287	two pirces of code that call C<< ->wait >> in a round-robbin fashion, you	616	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
288	lose. Therefore, condition variables are good to export to your caller, but	617	lose. Therefore, condition variables are good to export to your caller, but
289	you should avoid making a blocking wait yourself, at least in callbacks,	618	you should avoid making a blocking wait yourself, at least in callbacks,
290	as this asks for trouble.	619	as this asks for trouble.
291		620
292	This object has two methods:	621	Condition variables are represented by hash refs in perl, and the keys
		622	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
		623	easy (it is often useful to build your own transaction class on top of
		624	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
		625	its C<new> method in your own C<new> method.
		626
		627	There are two "sides" to a condition variable - the "producer side" which
		628	eventually calls C<< -> send >>, and the "consumer side", which waits
		629	for the send to occur.
		630
		631	Example: wait for a timer.
		632
		633	# condition: "wait till the timer is fired"
		634	my $timer_fired = AnyEvent->condvar;
		635
		636	# create the timer - we could wait for, say
		637	# a handle becomign ready, or even an
		638	# AnyEvent::HTTP request to finish, but
		639	# in this case, we simply use a timer:
		640	my $w = AnyEvent->timer (
		641	after => 1,
		642	cb => sub { $timer_fired->send },
		643	);
		644
		645	# this "blocks" (while handling events) till the callback
		646	# calls ->send
		647	$timer_fired->recv;
		648
		649	Example: wait for a timer, but take advantage of the fact that condition
		650	variables are also callable directly.
		651
		652	my $done = AnyEvent->condvar;
		653	my $delay = AnyEvent->timer (after => 5, cb => $done);
		654	$done->recv;
		655
		656	Example: Imagine an API that returns a condvar and doesn't support
		657	callbacks. This is how you make a synchronous call, for example from
		658	the main program:
		659
		660	use AnyEvent::CouchDB;
		661
		662	...
		663
		664	my @info = $couchdb->info->recv;
		665
		666	And this is how you would just set a callback to be called whenever the
		667	results are available:
		668
		669	$couchdb->info->cb (sub {
		670	my @info = $_[0]->recv;
		671	});
		672
		673	=head3 METHODS FOR PRODUCERS
		674
		675	These methods should only be used by the producing side, i.e. the
		676	code/module that eventually sends the signal. Note that it is also
		677	the producer side which creates the condvar in most cases, but it isn't
		678	uncommon for the consumer to create it as well.
293		679
294	=over 4	680	=over 4
295		681
		682	=item $cv->send (...)
		683
		684	Flag the condition as ready - a running C<< ->recv >> and all further
		685	calls to C<recv> will (eventually) return after this method has been
		686	called. If nobody is waiting the send will be remembered.
		687
		688	If a callback has been set on the condition variable, it is called
		689	immediately from within send.
		690
		691	Any arguments passed to the C<send> call will be returned by all
		692	future C<< ->recv >> calls.
		693
		694	Condition variables are overloaded so one can call them directly (as if
		695	they were a code reference). Calling them directly is the same as calling
		696	C<send>.
		697
		698	=item $cv->croak ($error)
		699
		700	Similar to send, but causes all calls to C<< ->recv >> to invoke
		701	C<Carp::croak> with the given error message/object/scalar.
		702
		703	This can be used to signal any errors to the condition variable
		704	user/consumer. Doing it this way instead of calling C<croak> directly
		705	delays the error detection, but has the overwhelming advantage that it
		706	diagnoses the error at the place where the result is expected, and not
		707	deep in some event callback with no connection to the actual code causing
		708	the problem.
		709
		710	=item $cv->begin ([group callback])
		711
296	=item $cv->wait	712	=item $cv->end
297		713
298	Wait (blocking if necessary) until the C<< ->broadcast >> method has been	714	These two methods can be used to combine many transactions/events into
299	called on c<$cv>, while servicing other watchers normally.	715	one. For example, a function that pings many hosts in parallel might want
		716	to use a condition variable for the whole process.
300		717
		718	Every call to C<< ->begin >> will increment a counter, and every call to
		719	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
		720	>>, the (last) callback passed to C<begin> will be executed, passing the
		721	condvar as first argument. That callback is I<supposed> to call C<< ->send
		722	>>, but that is not required. If no group callback was set, C<send> will
		723	be called without any arguments.
		724
		725	You can think of C<< $cv->send >> giving you an OR condition (one call
		726	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		727	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		728
		729	Let's start with a simple example: you have two I/O watchers (for example,
		730	STDOUT and STDERR for a program), and you want to wait for both streams to
		731	close before activating a condvar:
		732
		733	my $cv = AnyEvent->condvar;
		734
		735	$cv->begin; # first watcher
		736	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		737	defined sysread $fh1, my $buf, 4096
		738	or $cv->end;
		739	});
		740
		741	$cv->begin; # second watcher
		742	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		743	defined sysread $fh2, my $buf, 4096
		744	or $cv->end;
		745	});
		746
		747	$cv->recv;
		748
		749	This works because for every event source (EOF on file handle), there is
		750	one call to C<begin>, so the condvar waits for all calls to C<end> before
		751	sending.
		752
		753	The ping example mentioned above is slightly more complicated, as the
		754	there are results to be passed back, and the number of tasks that are
		755	begun can potentially be zero:
		756
		757	my $cv = AnyEvent->condvar;
		758
		759	my %result;
		760	$cv->begin (sub { shift->send (\%result) });
		761
		762	for my $host (@list_of_hosts) {
		763	$cv->begin;
		764	ping_host_then_call_callback $host, sub {
		765	$result{$host} = ...;
		766	$cv->end;
		767	};
		768	}
		769
		770	$cv->end;
		771
		772	...
		773
		774	my $results = $cv->recv;
		775
		776	This code fragment supposedly pings a number of hosts and calls
		777	C<send> after results for all then have have been gathered - in any
		778	order. To achieve this, the code issues a call to C<begin> when it starts
		779	each ping request and calls C<end> when it has received some result for
		780	it. Since C<begin> and C<end> only maintain a counter, the order in which
		781	results arrive is not relevant.
		782
		783	There is an additional bracketing call to C<begin> and C<end> outside the
		784	loop, which serves two important purposes: first, it sets the callback
		785	to be called once the counter reaches C<0>, and second, it ensures that
		786	C<send> is called even when C<no> hosts are being pinged (the loop
		787	doesn't execute once).
		788
		789	This is the general pattern when you "fan out" into multiple (but
		790	potentially zero) subrequests: use an outer C<begin>/C<end> pair to set
		791	the callback and ensure C<end> is called at least once, and then, for each
		792	subrequest you start, call C<begin> and for each subrequest you finish,
		793	call C<end>.
		794
		795	=back
		796
		797	=head3 METHODS FOR CONSUMERS
		798
		799	These methods should only be used by the consuming side, i.e. the
		800	code awaits the condition.
		801
		802	=over 4
		803
		804	=item $cv->recv
		805
		806	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
		807	>> methods have been called on C<$cv>, while servicing other watchers
		808	normally.
		809
301	You can only wait once on a condition - additional calls will return	810	You can only wait once on a condition - additional calls are valid but
302	immediately.	811	will return immediately.
		812
		813	If an error condition has been set by calling C<< ->croak >>, then this
		814	function will call C<croak>.
		815
		816	In list context, all parameters passed to C<send> will be returned,
		817	in scalar context only the first one will be returned.
		818
		819	Note that doing a blocking wait in a callback is not supported by any
		820	event loop, that is, recursive invocation of a blocking C<< ->recv >> is
		821	not allowed and the C<recv> call will C<croak> if such a condition is
		822	detected. This requirement can be dropped by relying on L<Coro::AnyEvent>
		823	, which allows you to do a blocking C<< ->recv >> from any thread
		824	that doesn't run the event loop itself. L<Coro::AnyEvent> is loaded
		825	automatically when L<Coro> is used with L<AnyEvent>, so code does not need
		826	to do anything special to take advantage of that: any code that would
		827	normally block your program because it calls C<recv>, be executed in an
		828	C<async> thread instead without blocking other threads.
303		829
304	Not all event models support a blocking wait - some die in that case	830	Not all event models support a blocking wait - some die in that case
305	(programs might want to do that to stay interactive), so I<if you are	831	(programs might want to do that to stay interactive), so I<if you are
306	using this from a module, never require a blocking wait>, but let the	832	using this from a module, never require a blocking wait>. Instead, let the
307	caller decide whether the call will block or not (for example, by coupling	833	caller decide whether the call will block or not (for example, by coupling
308	condition variables with some kind of request results and supporting	834	condition variables with some kind of request results and supporting
309	callbacks so the caller knows that getting the result will not block,	835	callbacks so the caller knows that getting the result will not block,
310	while still suppporting blocking waits if the caller so desires).	836	while still supporting blocking waits if the caller so desires).
311		837
312	Another reason I<never> to C<< ->wait >> in a module is that you cannot	838	You can ensure that C<< ->recv >> never blocks by setting a callback and
313	sensibly have two C<< ->wait >>'s in parallel, as that would require	839	only calling C<< ->recv >> from within that callback (or at a later
314	multiple interpreters or coroutines/threads, none of which C<AnyEvent>	840	time). This will work even when the event loop does not support blocking
315	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and	841	waits otherwise.
316	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
317	from different coroutines, however).
318		842
319	=item $cv->broadcast	843	=item $bool = $cv->ready
320		844
321	Flag the condition as ready - a running C<< ->wait >> and all further	845	Returns true when the condition is "true", i.e. whether C<send> or
322	calls to C<wait> will (eventually) return after this method has been	846	C<croak> have been called.
323	called. If nobody is waiting the broadcast will be remembered..	847
		848	=item $cb = $cv->cb ($cb->($cv))
		849
		850	This is a mutator function that returns the callback set and optionally
		851	replaces it before doing so.
		852
		853	The callback will be called when the condition becomes "true", i.e. when
		854	C<send> or C<croak> are called, with the only argument being the
		855	condition variable itself. If the condition is already true, the
		856	callback is called immediately when it is set. Calling C<recv> inside
		857	the callback or at any later time is guaranteed not to block.
324		858
325	=back	859	=back
326		860
327	Example:	861	=head1 SUPPORTED EVENT LOOPS/BACKENDS
328		862
329	# wait till the result is ready	863	The available backend classes are (every class has its own manpage):
330	my $result_ready = AnyEvent->condvar;
331		864
332	# do something such as adding a timer	865	=over 4
333	# or socket watcher the calls $result_ready->broadcast
334	# when the "result" is ready.
335	# in this case, we simply use a timer:
336	my $w = AnyEvent->timer (
337	after => 1,
338	cb => sub { $result_ready->broadcast },
339	);
340		866
341	# this "blocks" (while handling events) till the watcher	867	=item Backends that are autoprobed when no other event loop can be found.
342	# calls broadcast	868
343	$result_ready->wait;	869	EV is the preferred backend when no other event loop seems to be in
		870	use. If EV is not installed, then AnyEvent will fall back to its own
		871	pure-perl implementation, which is available everywhere as it comes with
		872	AnyEvent itself.
		873
		874	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		875	AnyEvent::Impl::Perl pure-perl AnyEvent::Loop, fast and portable.
		876
		877	=item Backends that are transparently being picked up when they are used.
		878
		879	These will be used if they are already loaded when the first watcher
		880	is created, in which case it is assumed that the application is using
		881	them. This means that AnyEvent will automatically pick the right backend
		882	when the main program loads an event module before anything starts to
		883	create watchers. Nothing special needs to be done by the main program.
		884
		885	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		886	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		887	AnyEvent::Impl::Tk based on Tk, very broken.
		888	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		889	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		890	AnyEvent::Impl::Irssi used when running within irssi.
		891	AnyEvent::Impl::IOAsync based on IO::Async.
		892	AnyEvent::Impl::Cocoa based on Cocoa::EventLoop.
		893	AnyEvent::Impl::FLTK based on FLTK (fltk 2 binding).
		894
		895	=item Backends with special needs.
		896
		897	Qt requires the Qt::Application to be instantiated first, but will
		898	otherwise be picked up automatically. As long as the main program
		899	instantiates the application before any AnyEvent watchers are created,
		900	everything should just work.
		901
		902	AnyEvent::Impl::Qt based on Qt.
		903
		904	=item Event loops that are indirectly supported via other backends.
		905
		906	Some event loops can be supported via other modules:
		907
		908	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		909
		910	B<WxWidgets> has no support for watching file handles. However, you can
		911	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		912	polls 20 times per second, which was considered to be too horrible to even
		913	consider for AnyEvent.
		914
		915	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		916	backend, so it can be supported through POE.
		917
		918	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		919	load L<POE> when detecting them, in the hope that POE will pick them up,
		920	in which case everything will be automatic.
		921
		922	=back
344		923
345	=head1 GLOBAL VARIABLES AND FUNCTIONS	924	=head1 GLOBAL VARIABLES AND FUNCTIONS
346		925
		926	These are not normally required to use AnyEvent, but can be useful to
		927	write AnyEvent extension modules.
		928
347	=over 4	929	=over 4
348		930
349	=item $AnyEvent::MODEL	931	=item $AnyEvent::MODEL
350		932
351	Contains C<undef> until the first watcher is being created. Then it	933	Contains C<undef> until the first watcher is being created, before the
		934	backend has been autodetected.
		935
352	contains the event model that is being used, which is the name of the	936	Afterwards it contains the event model that is being used, which is the
353	Perl class implementing the model. This class is usually one of the	937	name of the Perl class implementing the model. This class is usually one
354	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	938	of the C<AnyEvent::Impl::xxx> modules, but can be any other class in the
355	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	939	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
356		940	will be C<urxvt::anyevent>).
357	The known classes so far are:
358
359	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
360	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
361	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
362	AnyEvent::Impl::Event based on Event, second best choice.
363	AnyEvent::Impl::Glib based on Glib, third-best choice.
364	AnyEvent::Impl::Tk based on Tk, very bad choice.
365	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
366	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
367	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
368	AnyEvent::Impl::POE based on POE, not generic enough for full support.
369
370	There is no support for WxWidgets, as WxWidgets has no support for
371	watching file handles. However, you can use WxWidgets through the
372	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
373	second, which was considered to be too horrible to even consider for
374	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
375	it's adaptor.
376
377	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
378	autodetecting them.
379		941
380	=item AnyEvent::detect	942	=item AnyEvent::detect
381		943
382	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	944	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
383	if necessary. You should only call this function right before you would	945	if necessary. You should only call this function right before you would
384	have created an AnyEvent watcher anyway, that is, as late as possible at	946	have created an AnyEvent watcher anyway, that is, as late as possible at
385	runtime.	947	runtime, and not e.g. during initialisation of your module.
		948
		949	The effect of calling this function is as if a watcher had been created
		950	(specifically, actions that happen "when the first watcher is created"
		951	happen when calling detetc as well).
		952
		953	If you need to do some initialisation before AnyEvent watchers are
		954	created, use C<post_detect>.
		955
		956	=item $guard = AnyEvent::post_detect { BLOCK }
		957
		958	Arranges for the code block to be executed as soon as the event model is
		959	autodetected (or immediately if that has already happened).
		960
		961	The block will be executed I<after> the actual backend has been detected
		962	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		963	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		964	other initialisations - see the sources of L<AnyEvent::Strict> or
		965	L<AnyEvent::AIO> to see how this is used.
		966
		967	The most common usage is to create some global watchers, without forcing
		968	event module detection too early, for example, L<AnyEvent::AIO> creates
		969	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		970	avoid autodetecting the event module at load time.
		971
		972	If called in scalar or list context, then it creates and returns an object
		973	that automatically removes the callback again when it is destroyed (or
		974	C<undef> when the hook was immediately executed). See L<AnyEvent::AIO> for
		975	a case where this is useful.
		976
		977	Example: Create a watcher for the IO::AIO module and store it in
		978	C<$WATCHER>, but do so only do so after the event loop is initialised.
		979
		980	our WATCHER;
		981
		982	my $guard = AnyEvent::post_detect {
		983	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		984	};
		985
		986	# the ||= is important in case post_detect immediately runs the block,
		987	# as to not clobber the newly-created watcher. assigning both watcher and
		988	# post_detect guard to the same variable has the advantage of users being
		989	# able to just C<undef $WATCHER> if the watcher causes them grief.
		990
		991	$WATCHER ||= $guard;
		992
		993	=item @AnyEvent::post_detect
		994
		995	If there are any code references in this array (you can C<push> to it
		996	before or after loading AnyEvent), then they will be called directly
		997	after the event loop has been chosen.
		998
		999	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		1000	if it is defined then the event loop has already been detected, and the
		1001	array will be ignored.
		1002
		1003	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		1004	it, as it takes care of these details.
		1005
		1006	This variable is mainly useful for modules that can do something useful
		1007	when AnyEvent is used and thus want to know when it is initialised, but do
		1008	not need to even load it by default. This array provides the means to hook
		1009	into AnyEvent passively, without loading it.
		1010
		1011	Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used
		1012	together, you could put this into Coro (this is the actual code used by
		1013	Coro to accomplish this):
		1014
		1015	if (defined $AnyEvent::MODEL) {
		1016	# AnyEvent already initialised, so load Coro::AnyEvent
		1017	require Coro::AnyEvent;
		1018	} else {
		1019	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent
		1020	# as soon as it is
		1021	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };
		1022	}
		1023
		1024	=item AnyEvent::postpone { BLOCK }
		1025
		1026	Arranges for the block to be executed as soon as possible, but not before
		1027	the call itself returns. In practise, the block will be executed just
		1028	before the event loop polls for new events, or shortly afterwards.
		1029
		1030	This function never returns anything (to make the C<return postpone { ...
		1031	}> idiom more useful.
		1032
		1033	To understand the usefulness of this function, consider a function that
		1034	asynchronously does something for you and returns some transaction
		1035	object or guard to let you cancel the operation. For example,
		1036	C<AnyEvent::Socket::tcp_connect>:
		1037
		1038	# start a connection attempt unless one is active
		1039	$self->{connect_guard} ||= AnyEvent::Socket::tcp_connect "www.example.net", 80, sub {
		1040	delete $self->{connect_guard};
		1041	...
		1042	};
		1043
		1044	Imagine that this function could instantly call the callback, for
		1045	example, because it detects an obvious error such as a negative port
		1046	number. Invoking the callback before the function returns causes problems
		1047	however: the callback will be called and will try to delete the guard
		1048	object. But since the function hasn't returned yet, there is nothing to
		1049	delete. When the function eventually returns it will assign the guard
		1050	object to C<< $self->{connect_guard} >>, where it will likely never be
		1051	deleted, so the program thinks it is still trying to connect.
		1052
		1053	This is where C<AnyEvent::postpone> should be used. Instead of calling the
		1054	callback directly on error:
		1055
		1056	$cb->(undef), return # signal error to callback, BAD!
		1057	if $some_error_condition;
		1058
		1059	It should use C<postpone>:
		1060
		1061	AnyEvent::postpone { $cb->(undef) }, return # signal error to callback, later
		1062	if $some_error_condition;
		1063
		1064	=item AnyEvent::log $level, $msg[, @args]
		1065
		1066	Log the given C<$msg> at the given C<$level>.
		1067
		1068	If L<AnyEvent::Log> is not loaded then this function makes a simple test
		1069	to see whether the message will be logged. If the test succeeds it will
		1070	load AnyEvent::Log and call C<AnyEvent::Log::log> - consequently, look at
		1071	the L<AnyEvent::Log> documentation for details.
		1072
		1073	If the test fails it will simply return. Right now this happens when a
		1074	numerical loglevel is used and it is larger than the level specified via
		1075	C<$ENV{PERL_ANYEVENT_VERBOSE}>.
		1076
		1077	If you want to sprinkle loads of logging calls around your code, consider
		1078	creating a logger callback with the C<AnyEvent::Log::logger> function,
		1079	which can reduce typing, codesize and can reduce the logging overhead
		1080	enourmously.
386		1081
387	=back	1082	=back
388		1083
389	=head1 WHAT TO DO IN A MODULE	1084	=head1 WHAT TO DO IN A MODULE
390		1085
…		…
394	Be careful when you create watchers in the module body - AnyEvent will	1089	Be careful when you create watchers in the module body - AnyEvent will
395	decide which event module to use as soon as the first method is called, so	1090	decide which event module to use as soon as the first method is called, so
396	by calling AnyEvent in your module body you force the user of your module	1091	by calling AnyEvent in your module body you force the user of your module
397	to load the event module first.	1092	to load the event module first.
398		1093
399	Never call C<< ->wait >> on a condition variable unless you I<know> that	1094	Never call C<< ->recv >> on a condition variable unless you I<know> that
400	the C<< ->broadcast >> method has been called on it already. This is	1095	the C<< ->send >> method has been called on it already. This is
401	because it will stall the whole program, and the whole point of using	1096	because it will stall the whole program, and the whole point of using
402	events is to stay interactive.	1097	events is to stay interactive.
403		1098
404	It is fine, however, to call C<< ->wait >> when the user of your module	1099	It is fine, however, to call C<< ->recv >> when the user of your module
405	requests it (i.e. if you create a http request object ad have a method	1100	requests it (i.e. if you create a http request object ad have a method
406	called C<results> that returns the results, it should call C<< ->wait >>	1101	called C<results> that returns the results, it may call C<< ->recv >>
407	freely, as the user of your module knows what she is doing. always).	1102	freely, as the user of your module knows what she is doing. Always).
408		1103
409	=head1 WHAT TO DO IN THE MAIN PROGRAM	1104	=head1 WHAT TO DO IN THE MAIN PROGRAM
410		1105
411	There will always be a single main program - the only place that should	1106	There will always be a single main program - the only place that should
412	dictate which event model to use.	1107	dictate which event model to use.
413		1108
414	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	1109	If the program is not event-based, it need not do anything special, even
415	do anything special (it does not need to be event-based) and let AnyEvent	1110	when it depends on a module that uses an AnyEvent. If the program itself
416	decide which implementation to chose if some module relies on it.	1111	uses AnyEvent, but does not care which event loop is used, all it needs
		1112	to do is C<use AnyEvent>. In either case, AnyEvent will choose the best
		1113	available loop implementation.
417		1114
418	If the main program relies on a specific event model. For example, in	1115	If the main program relies on a specific event model - for example, in
419	Gtk2 programs you have to rely on the Glib module. You should load the	1116	Gtk2 programs you have to rely on the Glib module - you should load the
420	event module before loading AnyEvent or any module that uses it: generally	1117	event module before loading AnyEvent or any module that uses it: generally
421	speaking, you should load it as early as possible. The reason is that	1118	speaking, you should load it as early as possible. The reason is that
422	modules might create watchers when they are loaded, and AnyEvent will	1119	modules might create watchers when they are loaded, and AnyEvent will
423	decide on the event model to use as soon as it creates watchers, and it	1120	decide on the event model to use as soon as it creates watchers, and it
424	might chose the wrong one unless you load the correct one yourself.	1121	might choose the wrong one unless you load the correct one yourself.
425		1122
426	You can chose to use a rather inefficient pure-perl implementation by	1123	You can chose to use a pure-perl implementation by loading the
427	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	1124	C<AnyEvent::Loop> module, which gives you similar behaviour
428	behaviour everywhere, but letting AnyEvent chose is generally better.	1125	everywhere, but letting AnyEvent chose the model is generally better.
		1126
		1127	=head2 MAINLOOP EMULATION
		1128
		1129	Sometimes (often for short test scripts, or even standalone programs who
		1130	only want to use AnyEvent), you do not want to run a specific event loop.
		1131
		1132	In that case, you can use a condition variable like this:
		1133
		1134	AnyEvent->condvar->recv;
		1135
		1136	This has the effect of entering the event loop and looping forever.
		1137
		1138	Note that usually your program has some exit condition, in which case
		1139	it is better to use the "traditional" approach of storing a condition
		1140	variable somewhere, waiting for it, and sending it when the program should
		1141	exit cleanly.
		1142
		1143
		1144	=head1 OTHER MODULES
		1145
		1146	The following is a non-exhaustive list of additional modules that use
		1147	AnyEvent as a client and can therefore be mixed easily with other
		1148	AnyEvent modules and other event loops in the same program. Some of the
		1149	modules come as part of AnyEvent, the others are available via CPAN (see
		1150	L<http://search.cpan.org/search?m=module&q=anyevent%3A%3A*> for
		1151	a longer non-exhaustive list), and the list is heavily biased towards
		1152	modules of the AnyEvent author himself :)
		1153
		1154	=over 4
		1155
		1156	=item L<AnyEvent::Util> (part of the AnyEvent distribution)
		1157
		1158	Contains various utility functions that replace often-used blocking
		1159	functions such as C<inet_aton> with event/callback-based versions.
		1160
		1161	=item L<AnyEvent::Socket> (part of the AnyEvent distribution)
		1162
		1163	Provides various utility functions for (internet protocol) sockets,
		1164	addresses and name resolution. Also functions to create non-blocking tcp
		1165	connections or tcp servers, with IPv6 and SRV record support and more.
		1166
		1167	=item L<AnyEvent::Handle> (part of the AnyEvent distribution)
		1168
		1169	Provide read and write buffers, manages watchers for reads and writes,
		1170	supports raw and formatted I/O, I/O queued and fully transparent and
		1171	non-blocking SSL/TLS (via L<AnyEvent::TLS>).
		1172
		1173	=item L<AnyEvent::DNS> (part of the AnyEvent distribution)
		1174
		1175	Provides rich asynchronous DNS resolver capabilities.
		1176
		1177	=item L<AnyEvent::HTTP>, L<AnyEvent::IRC>, L<AnyEvent::XMPP>, L<AnyEvent::GPSD>, L<AnyEvent::IGS>, L<AnyEvent::FCP>
		1178
		1179	Implement event-based interfaces to the protocols of the same name (for
		1180	the curious, IGS is the International Go Server and FCP is the Freenet
		1181	Client Protocol).
		1182
		1183	=item L<AnyEvent::AIO> (part of the AnyEvent distribution)
		1184
		1185	Truly asynchronous (as opposed to non-blocking) I/O, should be in the
		1186	toolbox of every event programmer. AnyEvent::AIO transparently fuses
		1187	L<IO::AIO> and AnyEvent together, giving AnyEvent access to event-based
		1188	file I/O, and much more.
		1189
		1190	=item L<AnyEvent::Fork>, L<AnyEvent::Fork::RPC>, L<AnyEvent::Fork::Pool>, L<AnyEvent::Fork::Remote>
		1191
		1192	These let you safely fork new subprocesses, either locally or
		1193	remotely (e.g.v ia ssh), using some RPC protocol or not, without
		1194	the limitations normally imposed by fork (AnyEvent works fine for
		1195	example). Dynamically-resized worker pools are obviously included as well.
		1196
		1197	And they are quite tiny and fast as well - "abusing" L<AnyEvent::Fork>
		1198	just to exec external programs can easily beat using C<fork> and C<exec>
		1199	(or even C<system>) in most programs.
		1200
		1201	=item L<AnyEvent::Filesys::Notify>
		1202
		1203	AnyEvent is good for non-blocking stuff, but it can't detect file or
		1204	path changes (e.g. "watch this directory for new files", "watch this
		1205	file for changes"). The L<AnyEvent::Filesys::Notify> module promises to
		1206	do just that in a portbale fashion, supporting inotify on GNU/Linux and
		1207	some weird, without doubt broken, stuff on OS X to monitor files. It can
		1208	fall back to blocking scans at regular intervals transparently on other
		1209	platforms, so it's about as portable as it gets.
		1210
		1211	(I haven't used it myself, but it seems the biggest problem with it is
		1212	it quite bad performance).
		1213
		1214	=item L<AnyEvent::DBI>
		1215
		1216	Executes L<DBI> requests asynchronously in a proxy process for you,
		1217	notifying you in an event-based way when the operation is finished.
		1218
		1219	=item L<AnyEvent::FastPing>
		1220
		1221	The fastest ping in the west.
		1222
		1223	=item L<Coro>
		1224
		1225	Has special support for AnyEvent via L<Coro::AnyEvent>, which allows you
		1226	to simply invert the flow control - don't call us, we will call you:
		1227
		1228	async {
		1229	Coro::AnyEvent::sleep 5; # creates a 5s timer and waits for it
		1230	print "5 seconds later!\n";
		1231
		1232	Coro::AnyEvent::readable *STDIN; # uses an I/O watcher
		1233	my $line = <STDIN>; # works for ttys
		1234
		1235	AnyEvent::HTTP::http_get "url", Coro::rouse_cb;
		1236	my ($body, $hdr) = Coro::rouse_wait;
		1237	};
		1238
		1239	=back
429		1240
430	=cut	1241	=cut
431		1242
432	package AnyEvent;	1243	package AnyEvent;
433		1244
434	no warnings;	1245	BEGIN {
435	use strict;	1246	require "AnyEvent/constants.pl";
		1247	&AnyEvent::common_sense;
		1248	}
436		1249
437	use Carp;	1250	use Carp ();
438		1251
439	our $VERSION = '3.3';	1252	our $VERSION = '7.07';
440	our $MODEL;	1253	our $MODEL;
441
442	our $AUTOLOAD;
443	our @ISA;	1254	our @ISA;
444
445	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
446
447	our @REGISTRY;	1255	our @REGISTRY;
		1256	our $VERBOSE;
		1257	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		1258	our $MAX_SIGNAL_LATENCY = $ENV{PERL_ANYEVENT_MAX_SIGNAL_LATENCY} || 10; # executes after the BEGIN block below (tainting!)
448		1259
		1260	BEGIN {
		1261	eval "sub TAINT (){" . (${^TAINT}*1) . "}";
		1262
		1263	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1264	if ${^TAINT};
		1265
		1266	$ENV{"PERL_ANYEVENT_$_"} = $ENV{"AE_$_"}
		1267	for grep s/^AE_// && !exists $ENV{"PERL_ANYEVENT_$_"}, keys %ENV;
		1268
		1269	@ENV{grep /^PERL_ANYEVENT_/, keys %ENV} = ()
		1270	if ${^TAINT};
		1271
		1272	# $ENV{PERL_ANYEVENT_xxx} now valid
		1273
		1274	$VERBOSE = length $ENV{PERL_ANYEVENT_VERBOSE} ? $ENV{PERL_ANYEVENT_VERBOSE}*1 : 4;
		1275
		1276	my $idx;
		1277	$PROTOCOL{$_} = ++$idx
		1278	for reverse split /\s*,\s*/,
		1279	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		1280	}
		1281
		1282	our @post_detect;
		1283
		1284	sub post_detect(&) {
		1285	my ($cb) = @_;
		1286
		1287	push @post_detect, $cb;
		1288
		1289	defined wantarray
		1290	? bless \$cb, "AnyEvent::Util::postdetect"
		1291	: ()
		1292	}
		1293
		1294	sub AnyEvent::Util::postdetect::DESTROY {
		1295	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		1296	}
		1297
		1298	our $POSTPONE_W;
		1299	our @POSTPONE;
		1300
		1301	sub _postpone_exec {
		1302	undef $POSTPONE_W;
		1303
		1304	&{ shift @POSTPONE }
		1305	while @POSTPONE;
		1306	}
		1307
		1308	sub postpone(&) {
		1309	push @POSTPONE, shift;
		1310
		1311	$POSTPONE_W ||= AE::timer (0, 0, \&_postpone_exec);
		1312
		1313	()
		1314	}
		1315
		1316	sub log($$;@) {
		1317	# only load the big bloated module when we actually are about to log something
		1318	if ($_[0] <= ($VERBOSE || 1)) { # also catches non-numeric levels(!) and fatal
		1319	local ($!, $@);
		1320	require AnyEvent::Log; # among other things, sets $VERBOSE to 9
		1321	# AnyEvent::Log overwrites this function
		1322	goto &log;
		1323	}
		1324
		1325	0 # not logged
		1326	}
		1327
		1328	sub _logger($;$) {
		1329	my ($level, $renabled) = @_;
		1330
		1331	$$renabled = $level <= $VERBOSE;
		1332
		1333	my $logger = [(caller)[0], $level, $renabled];
		1334
		1335	$AnyEvent::Log::LOGGER{$logger+0} = $logger;
		1336
		1337	# return unless defined wantarray;
		1338	#
		1339	# require AnyEvent::Util;
		1340	# my $guard = AnyEvent::Util::guard (sub {
		1341	# # "clean up"
		1342	# delete $LOGGER{$logger+0};
		1343	# });
		1344	#
		1345	# sub {
		1346	# return 0 unless $$renabled;
		1347	#
		1348	# $guard if 0; # keep guard alive, but don't cause runtime overhead
		1349	# require AnyEvent::Log unless $AnyEvent::Log::VERSION;
		1350	# package AnyEvent::Log;
		1351	# _log ($logger->[0], $level, @_) # logger->[0] has been converted at load time
		1352	# }
		1353	}
		1354
		1355	if (length $ENV{PERL_ANYEVENT_LOG}) {
		1356	require AnyEvent::Log; # AnyEvent::Log does the thing for us
		1357	}
		1358
449	my @models = (	1359	our @models = (
450	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
451	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
452	[EV:: => AnyEvent::Impl::EV::],	1360	[EV:: => AnyEvent::Impl::EV::],
		1361	[AnyEvent::Loop:: => AnyEvent::Impl::Perl::],
		1362	# everything below here will not (normally) be autoprobed
		1363	# as the pure perl backend should work everywhere
		1364	# and is usually faster
		1365	[Irssi:: => AnyEvent::Impl::Irssi::], # Irssi has a bogus "Event" package, so msut be near the top
453	[Event:: => AnyEvent::Impl::Event::],	1366	[Event:: => AnyEvent::Impl::Event::], # slow, stable
454	[Glib:: => AnyEvent::Impl::Glib::],	1367	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers
		1368	# everything below here should not be autoloaded
		1369	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
455	[Tk:: => AnyEvent::Impl::Tk::],	1370	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		1371	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		1372	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
456	[Wx:: => AnyEvent::Impl::POE::],	1373	[Wx:: => AnyEvent::Impl::POE::],
457	[Prima:: => AnyEvent::Impl::POE::],	1374	[Prima:: => AnyEvent::Impl::POE::],
458	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1375	[IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # a bitch to autodetect
459	# everything below here will not be autoprobed as the pureperl backend should work everywhere	1376	[Cocoa::EventLoop:: => AnyEvent::Impl::Cocoa::],
460	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy	1377	[FLTK:: => AnyEvent::Impl::FLTK::],
461	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
462	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
463	);	1378	);
464		1379
465	our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);	1380	our @isa_hook;
		1381
		1382	sub _isa_set {
		1383	my @pkg = ("AnyEvent", (map $_->[0], grep defined, @isa_hook), $MODEL);
		1384
		1385	@{"$pkg[$_-1]::ISA"} = $pkg[$_]
		1386	for 1 .. $#pkg;
		1387
		1388	grep $_ && $_->[1], @isa_hook
		1389	and AE::_reset ();
		1390	}
		1391
		1392	# used for hooking AnyEvent::Strict and AnyEvent::Debug::Wrap into the class hierarchy
		1393	sub _isa_hook($$;$) {
		1394	my ($i, $pkg, $reset_ae) = @_;
		1395
		1396	$isa_hook[$i] = $pkg ? [$pkg, $reset_ae] : undef;
		1397
		1398	_isa_set;
		1399	}
		1400
		1401	# all autoloaded methods reserve the complete glob, not just the method slot.
		1402	# due to bugs in perls method cache implementation.
		1403	our @methods = qw(io timer time now now_update signal child idle condvar);
466		1404
467	sub detect() {	1405	sub detect() {
		1406	return $MODEL if $MODEL; # some programs keep references to detect
		1407
		1408	# IO::Async::Loop::AnyEvent is extremely evil, refuse to work with it
		1409	# the author knows about the problems and what it does to AnyEvent as a whole
		1410	# (and the ability of others to use AnyEvent), but simply wants to abuse AnyEvent
		1411	# anyway.
		1412	AnyEvent::log fatal => "IO::Async::Loop::AnyEvent detected - that module is broken by\n"
		1413	. "design, abuses internals and breaks AnyEvent - will not continue."
		1414	if exists $INC{"IO/Async/Loop/AnyEvent.pm"};
		1415
		1416	local $!; # for good measure
		1417	local $SIG{__DIE__}; # we use eval
		1418
		1419	# free some memory
		1420	*detect = sub () { $MODEL };
		1421	# undef &func doesn't correctly update the method cache. grmbl.
		1422	# so we delete the whole glob. grmbl.
		1423	# otoh, perl doesn't let me undef an active usb, but it lets me free
		1424	# a glob with an active sub. hrm. i hope it works, but perl is
		1425	# usually buggy in this department. sigh.
		1426	delete @{"AnyEvent::"}{@methods};
		1427	undef @methods;
		1428
		1429	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z0-9:]+)$/) {
		1430	my $model = $1;
		1431	$model = "AnyEvent::Impl::$model" unless $model =~ s/::$//;
		1432	if (eval "require $model") {
		1433	AnyEvent::log 7 => "Loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.";
		1434	$MODEL = $model;
		1435	} else {
		1436	AnyEvent::log 4 => "Unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@";
		1437	}
		1438	}
		1439
		1440	# check for already loaded models
468	unless ($MODEL) {	1441	unless ($MODEL) {
469	no strict 'refs';	1442	for (@REGISTRY, @models) {
470		1443	my ($package, $model) = @$_;
471	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	1444	if (${"$package\::VERSION"} > 0) {
472	my $model = "AnyEvent::Impl::$1";
473	if (eval "require $model") {	1445	if (eval "require $model") {
		1446	AnyEvent::log 7 => "Autodetected model '$model', using it.";
474	$MODEL = $model;	1447	$MODEL = $model;
475	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	1448	last;
476	} else {	1449	} else {
477	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;	1450	AnyEvent::log 8 => "Detected event loop $package, but cannot load '$model', skipping: $@";
		1451	}
478	}	1452	}
479	}	1453	}
480		1454
481	# check for already loaded models
482	unless ($MODEL) {	1455	unless ($MODEL) {
		1456	# try to autoload a model
483	for (@REGISTRY, @models) {	1457	for (@REGISTRY, @models) {
484	my ($package, $model) = @$_;	1458	my ($package, $model) = @$_;
		1459	if (
		1460	eval "require $package"
485	if (${"$package\::VERSION"} > 0) {	1461	and ${"$package\::VERSION"} > 0
486	if (eval "require $model") {	1462	and eval "require $model"
		1463	) {
		1464	AnyEvent::log 7 => "Autoloaded model '$model', using it.";
487	$MODEL = $model;	1465	$MODEL = $model;
488	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;
489	last;	1466	last;
490	}
491	}	1467	}
492	}	1468	}
493		1469
494	unless ($MODEL) {	1470	$MODEL
495	# try to load a model	1471	or AnyEvent::log fatal => "Backend autodetection failed - did you properly install AnyEvent?";
		1472	}
		1473	}
496		1474
497	for (@REGISTRY, @models) {	1475	# free memory only needed for probing
498	my ($package, $model) = @$_;	1476	undef @models;
499	if (eval "require $package"	1477	undef @REGISTRY;
500	and ${"$package\::VERSION"} > 0	1478
501	and eval "require $model") {	1479	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
502	$MODEL = $model;	1480
503	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;	1481	# now nuke some methods that are overridden by the backend.
		1482	# SUPER usage is not allowed in these.
		1483	for (qw(time signal child idle)) {
		1484	undef &{"AnyEvent::Base::$_"}
		1485	if defined &{"$MODEL\::$_"};
		1486	}
		1487
		1488	_isa_set;
		1489
		1490	# we're officially open!
		1491
		1492	if ($ENV{PERL_ANYEVENT_STRICT}) {
		1493	require AnyEvent::Strict;
		1494	}
		1495
		1496	if ($ENV{PERL_ANYEVENT_DEBUG_WRAP}) {
		1497	require AnyEvent::Debug;
		1498	AnyEvent::Debug::wrap ($ENV{PERL_ANYEVENT_DEBUG_WRAP});
		1499	}
		1500
		1501	if (length $ENV{PERL_ANYEVENT_DEBUG_SHELL}) {
		1502	require AnyEvent::Socket;
		1503	require AnyEvent::Debug;
		1504
		1505	my $shell = $ENV{PERL_ANYEVENT_DEBUG_SHELL};
		1506	$shell =~ s/\$\$/$$/g;
		1507
		1508	my ($host, $service) = AnyEvent::Socket::parse_hostport ($shell);
		1509	$AnyEvent::Debug::SHELL = AnyEvent::Debug::shell ($host, $service);
		1510	}
		1511
		1512	# now the anyevent environment is set up as the user told us to, so
		1513	# call the actual user code - post detects
		1514
		1515	(shift @post_detect)->() while @post_detect;
		1516	undef @post_detect;
		1517
		1518	*post_detect = sub(&) {
		1519	shift->();
		1520
		1521	undef
		1522	};
		1523
		1524	$MODEL
		1525	}
		1526
		1527	for my $name (@methods) {
		1528	*$name = sub {
		1529	detect;
		1530	# we use goto because
		1531	# a) it makes the thunk more transparent
		1532	# b) it allows us to delete the thunk later
		1533	goto &{ UNIVERSAL::can AnyEvent => "SUPER::$name" }
		1534	};
		1535	}
		1536
		1537	# utility function to dup a filehandle. this is used by many backends
		1538	# to support binding more than one watcher per filehandle (they usually
		1539	# allow only one watcher per fd, so we dup it to get a different one).
		1540	sub _dupfh($$;$$) {
		1541	my ($poll, $fh, $r, $w) = @_;
		1542
		1543	# cygwin requires the fh mode to be matching, unix doesn't
		1544	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1545
		1546	open my $fh2, $mode, $fh
		1547	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1548
		1549	# we assume CLOEXEC is already set by perl in all important cases
		1550
		1551	($fh2, $rw)
		1552	}
		1553
		1554	=head1 SIMPLIFIED AE API
		1555
		1556	Starting with version 5.0, AnyEvent officially supports a second, much
		1557	simpler, API that is designed to reduce the calling, typing and memory
		1558	overhead by using function call syntax and a fixed number of parameters.
		1559
		1560	See the L<AE> manpage for details.
		1561
		1562	=cut
		1563
		1564	package AE;
		1565
		1566	our $VERSION = $AnyEvent::VERSION;
		1567
		1568	sub _reset() {
		1569	eval q{
		1570	# fall back to the main API by default - backends and AnyEvent::Base
		1571	# implementations can overwrite these.
		1572
		1573	sub io($$$) {
		1574	AnyEvent->io (fh => $_[0], poll => $_[1] ? "w" : "r", cb => $_[2])
		1575	}
		1576
		1577	sub timer($$$) {
		1578	AnyEvent->timer (after => $_[0], interval => $_[1], cb => $_[2])
		1579	}
		1580
		1581	sub signal($$) {
		1582	AnyEvent->signal (signal => $_[0], cb => $_[1])
		1583	}
		1584
		1585	sub child($$) {
		1586	AnyEvent->child (pid => $_[0], cb => $_[1])
		1587	}
		1588
		1589	sub idle($) {
		1590	AnyEvent->idle (cb => $_[0]);
		1591	}
		1592
		1593	sub cv(;&) {
		1594	AnyEvent->condvar (@_ ? (cb => $_[0]) : ())
		1595	}
		1596
		1597	sub now() {
		1598	AnyEvent->now
		1599	}
		1600
		1601	sub now_update() {
		1602	AnyEvent->now_update
		1603	}
		1604
		1605	sub time() {
		1606	AnyEvent->time
		1607	}
		1608
		1609	*postpone = \&AnyEvent::postpone;
		1610	*log = \&AnyEvent::log;
		1611	};
		1612	die if $@;
		1613	}
		1614
		1615	BEGIN { _reset }
		1616
		1617	package AnyEvent::Base;
		1618
		1619	# default implementations for many methods
		1620
		1621	sub time {
		1622	eval q{ # poor man's autoloading {}
		1623	# probe for availability of Time::HiRes
		1624	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1625	*time = sub { Time::HiRes::time () };
		1626	*AE::time = \& Time::HiRes::time ;
		1627	*now = \&time;
		1628	AnyEvent::log 8 => "using Time::HiRes for sub-second timing accuracy.";
		1629	# if (eval "use POSIX (); (POSIX::times())...
		1630	} else {
		1631	*time = sub { CORE::time };
		1632	*AE::time = sub (){ CORE::time };
		1633	*now = \&time;
		1634	AnyEvent::log 3 => "Using built-in time(), no sub-second resolution!";
		1635	}
		1636	};
		1637	die if $@;
		1638
		1639	&time
		1640	}
		1641
		1642	*now = \&time;
		1643	sub now_update { }
		1644
		1645	sub _poll {
		1646	Carp::croak "$AnyEvent::MODEL does not support blocking waits. Caught";
		1647	}
		1648
		1649	# default implementation for ->condvar
		1650	# in fact, the default should not be overwritten
		1651
		1652	sub condvar {
		1653	eval q{ # poor man's autoloading {}
		1654	*condvar = sub {
		1655	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
		1656	};
		1657
		1658	*AE::cv = sub (;&) {
		1659	bless { @_ ? (_ae_cb => shift) : () }, "AnyEvent::CondVar"
		1660	};
		1661	};
		1662	die if $@;
		1663
		1664	&condvar
		1665	}
		1666
		1667	# default implementation for ->signal
		1668
		1669	our $HAVE_ASYNC_INTERRUPT;
		1670
		1671	sub _have_async_interrupt() {
		1672	$HAVE_ASYNC_INTERRUPT = 1*(!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT}
		1673	&& eval "use Async::Interrupt 1.02 (); 1")
		1674	unless defined $HAVE_ASYNC_INTERRUPT;
		1675
		1676	$HAVE_ASYNC_INTERRUPT
		1677	}
		1678
		1679	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1680	our (%SIG_ASY, %SIG_ASY_W);
		1681	our ($SIG_COUNT, $SIG_TW);
		1682
		1683	# install a dummy wakeup watcher to reduce signal catching latency
		1684	# used by Impls
		1685	sub _sig_add() {
		1686	unless ($SIG_COUNT++) {
		1687	# try to align timer on a full-second boundary, if possible
		1688	my $NOW = AE::now;
		1689
		1690	$SIG_TW = AE::timer
		1691	$MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1692	$MAX_SIGNAL_LATENCY,
		1693	sub { } # just for the PERL_ASYNC_CHECK
		1694	;
		1695	}
		1696	}
		1697
		1698	sub _sig_del {
		1699	undef $SIG_TW
		1700	unless --$SIG_COUNT;
		1701	}
		1702
		1703	our $_sig_name_init; $_sig_name_init = sub {
		1704	eval q{ # poor man's autoloading {}
		1705	undef $_sig_name_init;
		1706
		1707	if (_have_async_interrupt) {
		1708	*sig2num = \&Async::Interrupt::sig2num;
		1709	*sig2name = \&Async::Interrupt::sig2name;
		1710	} else {
		1711	require Config;
		1712
		1713	my %signame2num;
		1714	@signame2num{ split ' ', $Config::Config{sig_name} }
		1715	= split ' ', $Config::Config{sig_num};
		1716
		1717	my @signum2name;
		1718	@signum2name[values %signame2num] = keys %signame2num;
		1719
		1720	*sig2num = sub($) {
		1721	$_[0] > 0 ? shift : $signame2num{+shift}
		1722	};
		1723	*sig2name = sub ($) {
		1724	$_[0] > 0 ? $signum2name[+shift] : shift
		1725	};
		1726	}
		1727	};
		1728	die if $@;
		1729	};
		1730
		1731	sub sig2num ($) { &$_sig_name_init; &sig2num }
		1732	sub sig2name($) { &$_sig_name_init; &sig2name }
		1733
		1734	sub signal {
		1735	eval q{ # poor man's autoloading {}
		1736	# probe for availability of Async::Interrupt
		1737	if (_have_async_interrupt) {
		1738	AnyEvent::log 8 => "Using Async::Interrupt for race-free signal handling.";
		1739
		1740	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1741	$SIG_IO = AE::io $SIGPIPE_R->fileno, 0, \&_signal_exec;
		1742
		1743	} else {
		1744	AnyEvent::log 8 => "Using emulated perl signal handling with latency timer.";
		1745
		1746	if (AnyEvent::WIN32) {
		1747	require AnyEvent::Util;
		1748
		1749	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1750	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R, 1) if $SIGPIPE_R;
		1751	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W, 1) if $SIGPIPE_W; # just in case
		1752	} else {
		1753	pipe $SIGPIPE_R, $SIGPIPE_W;
		1754	fcntl $SIGPIPE_R, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_R;
		1755	fcntl $SIGPIPE_W, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_W; # just in case
		1756
		1757	# not strictly required, as $^F is normally 2, but let's make sure...
		1758	fcntl $SIGPIPE_R, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1759	fcntl $SIGPIPE_W, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1760	}
		1761
		1762	$SIGPIPE_R
		1763	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1764
		1765	$SIG_IO = AE::io $SIGPIPE_R, 0, \&_signal_exec;
		1766	}
		1767
		1768	*signal = $HAVE_ASYNC_INTERRUPT
		1769	? sub {
		1770	my (undef, %arg) = @_;
		1771
		1772	# async::interrupt
		1773	my $signal = sig2num $arg{signal};
		1774	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1775
		1776	$SIG_ASY{$signal} ||= new Async::Interrupt
		1777	cb => sub { undef $SIG_EV{$signal} },
		1778	signal => $signal,
		1779	pipe => [$SIGPIPE_R->filenos],
		1780	pipe_autodrain => 0,
		1781	;
		1782
		1783	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1784	}
		1785	: sub {
		1786	my (undef, %arg) = @_;
		1787
		1788	# pure perl
		1789	my $signal = sig2name $arg{signal};
		1790	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1791
		1792	$SIG{$signal} ||= sub {
504	last;	1793	local $!;
		1794	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1795	undef $SIG_EV{$signal};
505	}	1796	};
		1797
		1798	# can't do signal processing without introducing races in pure perl,
		1799	# so limit the signal latency.
		1800	_sig_add;
		1801
		1802	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1803	}
		1804	;
		1805
		1806	*AnyEvent::Base::signal::DESTROY = sub {
		1807	my ($signal, $cb) = @{$_[0]};
		1808
		1809	_sig_del;
		1810
		1811	delete $SIG_CB{$signal}{$cb};
		1812
		1813	$HAVE_ASYNC_INTERRUPT
		1814	? delete $SIG_ASY{$signal}
		1815	: # delete doesn't work with older perls - they then
		1816	# print weird messages, or just unconditionally exit
		1817	# instead of getting the default action.
		1818	undef $SIG{$signal}
		1819	unless keys %{ $SIG_CB{$signal} };
		1820	};
		1821
		1822	*_signal_exec = sub {
		1823	$HAVE_ASYNC_INTERRUPT
		1824	? $SIGPIPE_R->drain
		1825	: sysread $SIGPIPE_R, (my $dummy), 9;
		1826
		1827	while (%SIG_EV) {
		1828	for (keys %SIG_EV) {
		1829	delete $SIG_EV{$_};
		1830	&$_ for values %{ $SIG_CB{$_} || {} };
506	}	1831	}
507
508	$MODEL
509	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.";
510	}	1832	}
511	}	1833	};
512
513	unshift @ISA, $MODEL;
514	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
515	}
516
517	$MODEL
518	}
519
520	sub AUTOLOAD {
521	(my $func = $AUTOLOAD) =~ s/.*://;
522
523	$method{$func}
524	or croak "$func: not a valid method for AnyEvent objects";
525
526	detect unless $MODEL;
527
528	my $class = shift;
529	$class->$func (@_);
530	}
531
532	package AnyEvent::Base;
533
534	# default implementation for ->condvar, ->wait, ->broadcast
535
536	sub condvar {
537	bless \my $flag, "AnyEvent::Base::CondVar"
538	}
539
540	sub AnyEvent::Base::CondVar::broadcast {
541	${$_[0]}++;
542	}
543
544	sub AnyEvent::Base::CondVar::wait {
545	AnyEvent->one_event while !${$_[0]};
546	}
547
548	# default implementation for ->signal
549
550	our %SIG_CB;
551
552	sub signal {
553	my (undef, %arg) = @_;
554
555	my $signal = uc $arg{signal}
556	or Carp::croak "required option 'signal' is missing";
557
558	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
559	$SIG{$signal} ||= sub {
560	$_->() for values %{ $SIG_CB{$signal} || {} };
561	};	1834	};
		1835	die if $@;
562		1836
563	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1837	&signal
564	}
565
566	sub AnyEvent::Base::Signal::DESTROY {
567	my ($signal, $cb) = @{$_[0]};
568
569	delete $SIG_CB{$signal}{$cb};
570
571	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };
572	}	1838	}
573		1839
574	# default implementation for ->child	1840	# default implementation for ->child
575		1841
576	our %PID_CB;	1842	our %PID_CB;
577	our $CHLD_W;	1843	our $CHLD_W;
578	our $CHLD_DELAY_W;	1844	our $CHLD_DELAY_W;
579	our $PID_IDLE;
580	our $WNOHANG;
581		1845
582	sub _child_wait {	1846	# used by many Impl's
583	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1847	sub _emit_childstatus($$) {
		1848	my (undef, $rpid, $rstatus) = @_;
		1849
		1850	$_->($rpid, $rstatus)
584	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1851	for values %{ $PID_CB{$rpid} || {} },
585	(values %{ $PID_CB{0} || {} });	1852	values %{ $PID_CB{0} || {} };
		1853	}
		1854
		1855	sub child {
		1856	eval q{ # poor man's autoloading {}
		1857	*_sigchld = sub {
		1858	my $pid;
		1859
		1860	AnyEvent->_emit_childstatus ($pid, $?)
		1861	while ($pid = waitpid -1, WNOHANG) > 0;
		1862	};
		1863
		1864	*child = sub {
		1865	my (undef, %arg) = @_;
		1866
		1867	my $pid = $arg{pid};
		1868	my $cb = $arg{cb};
		1869
		1870	$PID_CB{$pid}{$cb+0} = $cb;
		1871
		1872	unless ($CHLD_W) {
		1873	$CHLD_W = AE::signal CHLD => \&_sigchld;
		1874	# child could be a zombie already, so make at least one round
		1875	&_sigchld;
		1876	}
		1877
		1878	bless [$pid, $cb+0], "AnyEvent::Base::child"
		1879	};
		1880
		1881	*AnyEvent::Base::child::DESTROY = sub {
		1882	my ($pid, $icb) = @{$_[0]};
		1883
		1884	delete $PID_CB{$pid}{$icb};
		1885	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
		1886
		1887	undef $CHLD_W unless keys %PID_CB;
		1888	};
		1889	};
		1890	die if $@;
		1891
		1892	&child
		1893	}
		1894
		1895	# idle emulation is done by simply using a timer, regardless
		1896	# of whether the process is idle or not, and not letting
		1897	# the callback use more than 50% of the time.
		1898	sub idle {
		1899	eval q{ # poor man's autoloading {}
		1900	*idle = sub {
		1901	my (undef, %arg) = @_;
		1902
		1903	my ($cb, $w, $rcb) = $arg{cb};
		1904
		1905	$rcb = sub {
		1906	if ($cb) {
		1907	$w = AE::time;
		1908	&$cb;
		1909	$w = AE::time - $w;
		1910
		1911	# never use more then 50% of the time for the idle watcher,
		1912	# within some limits
		1913	$w = 0.0001 if $w < 0.0001;
		1914	$w = 5 if $w > 5;
		1915
		1916	$w = AE::timer $w, 0, $rcb;
		1917	} else {
		1918	# clean up...
		1919	undef $w;
		1920	undef $rcb;
		1921	}
		1922	};
		1923
		1924	$w = AE::timer 0.05, 0, $rcb;
		1925
		1926	bless \\$cb, "AnyEvent::Base::idle"
		1927	};
		1928
		1929	*AnyEvent::Base::idle::DESTROY = sub {
		1930	undef $${$_[0]};
		1931	};
		1932	};
		1933	die if $@;
		1934
		1935	&idle
		1936	}
		1937
		1938	package AnyEvent::CondVar;
		1939
		1940	our @ISA = AnyEvent::CondVar::Base::;
		1941
		1942	# only to be used for subclassing
		1943	sub new {
		1944	my $class = shift;
		1945	bless AnyEvent->condvar (@_), $class
		1946	}
		1947
		1948	package AnyEvent::CondVar::Base;
		1949
		1950	#use overload
		1951	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1952	# fallback => 1;
		1953
		1954	# save 300+ kilobytes by dirtily hardcoding overloading
		1955	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1956	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1957	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1958	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1959
		1960	our $WAITING;
		1961
		1962	sub _send {
		1963	# nop
		1964	}
		1965
		1966	sub _wait {
		1967	AnyEvent->_poll until $_[0]{_ae_sent};
		1968	}
		1969
		1970	sub send {
		1971	my $cv = shift;
		1972	$cv->{_ae_sent} = [@_];
		1973	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1974	$cv->_send;
		1975	}
		1976
		1977	sub croak {
		1978	$_[0]{_ae_croak} = $_[1];
		1979	$_[0]->send;
		1980	}
		1981
		1982	sub ready {
		1983	$_[0]{_ae_sent}
		1984	}
		1985
		1986	sub recv {
		1987	unless ($_[0]{_ae_sent}) {
		1988	$WAITING
		1989	and Carp::croak "AnyEvent::CondVar: recursive blocking wait attempted";
		1990
		1991	local $WAITING = 1;
		1992	$_[0]->_wait;
586	}	1993	}
587		1994
588	undef $PID_IDLE;	1995	$_[0]{_ae_croak}
589	}	1996	and Carp::croak $_[0]{_ae_croak};
590		1997
591	sub _sigchld {	1998	wantarray
592	# make sure we deliver these changes "synchronous" with the event loop.	1999	? @{ $_[0]{_ae_sent} }
593	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {	2000	: $_[0]{_ae_sent}[0]
594	undef $CHLD_DELAY_W;
595	&_child_wait;
596	});
597	}	2001	}
598		2002
599	sub child {	2003	sub cb {
600	my (undef, %arg) = @_;	2004	my $cv = shift;
601		2005
602	defined (my $pid = $arg{pid} + 0)	2006	@_
603	or Carp::croak "required option 'pid' is missing";	2007	and $cv->{_ae_cb} = shift
		2008	and $cv->{_ae_sent}
		2009	and (delete $cv->{_ae_cb})->($cv);
604		2010
605	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	2011	$cv->{_ae_cb}
606
607	unless ($WNOHANG) {
608	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;
609	}
610
611	unless ($CHLD_W) {
612	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
613	# child could be a zombie already, so make at least one round
614	&_sigchld;
615	}
616
617	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"
618	}	2012	}
619		2013
620	sub AnyEvent::Base::Child::DESTROY {	2014	sub begin {
621	my ($pid, $cb) = @{$_[0]};	2015	++$_[0]{_ae_counter};
622		2016	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
623	delete $PID_CB{$pid}{$cb};
624	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
625
626	undef $CHLD_W unless keys %PID_CB;
627	}	2017	}
		2018
		2019	sub end {
		2020	return if --$_[0]{_ae_counter};
		2021	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		2022	}
		2023
		2024	# undocumented/compatibility with pre-3.4
		2025	*broadcast = \&send;
		2026	*wait = \&recv;
		2027
		2028	=head1 ERROR AND EXCEPTION HANDLING
		2029
		2030	In general, AnyEvent does not do any error handling - it relies on the
		2031	caller to do that if required. The L<AnyEvent::Strict> module (see also
		2032	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		2033	checking of all AnyEvent methods, however, which is highly useful during
		2034	development.
		2035
		2036	As for exception handling (i.e. runtime errors and exceptions thrown while
		2037	executing a callback), this is not only highly event-loop specific, but
		2038	also not in any way wrapped by this module, as this is the job of the main
		2039	program.
		2040
		2041	The pure perl event loop simply re-throws the exception (usually
		2042	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		2043	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		2044	so on.
		2045
		2046	=head1 ENVIRONMENT VARIABLES
		2047
		2048	AnyEvent supports a number of environment variables that tune the
		2049	runtime behaviour. They are usually evaluated when AnyEvent is
		2050	loaded, initialised, or a submodule that uses them is loaded. Many of
		2051	them also cause AnyEvent to load additional modules - for example,
		2052	C<PERL_ANYEVENT_DEBUG_WRAP> causes the L<AnyEvent::Debug> module to be
		2053	loaded.
		2054
		2055	All the environment variables documented here start with
		2056	C<PERL_ANYEVENT_>, which is what AnyEvent considers its own
		2057	namespace. Other modules are encouraged (but by no means required) to use
		2058	C<PERL_ANYEVENT_SUBMODULE> if they have registered the AnyEvent::Submodule
		2059	namespace on CPAN, for any submodule. For example, L<AnyEvent::HTTP> could
		2060	be expected to use C<PERL_ANYEVENT_HTTP_PROXY> (it should not access env
		2061	variables starting with C<AE_>, see below).
		2062
		2063	All variables can also be set via the C<AE_> prefix, that is, instead
		2064	of setting C<PERL_ANYEVENT_VERBOSE> you can also set C<AE_VERBOSE>. In
		2065	case there is a clash btween anyevent and another program that uses
		2066	C<AE_something> you can set the corresponding C<PERL_ANYEVENT_something>
		2067	variable to the empty string, as those variables take precedence.
		2068
		2069	When AnyEvent is first loaded, it copies all C<AE_xxx> env variables
		2070	to their C<PERL_ANYEVENT_xxx> counterpart unless that variable already
		2071	exists. If taint mode is on, then AnyEvent will remove I<all> environment
		2072	variables starting with C<PERL_ANYEVENT_> from C<%ENV> (or replace them
		2073	with C<undef> or the empty string, if the corresaponding C<AE_> variable
		2074	is set).
		2075
		2076	The exact algorithm is currently:
		2077
		2078	1. if taint mode enabled, delete all PERL_ANYEVENT_xyz variables from %ENV
		2079	2. copy over AE_xyz to PERL_ANYEVENT_xyz unless the latter alraedy exists
		2080	3. if taint mode enabled, set all PERL_ANYEVENT_xyz variables to undef.
		2081
		2082	This ensures that child processes will not see the C<AE_> variables.
		2083
		2084	The following environment variables are currently known to AnyEvent:
		2085
		2086	=over 4
		2087
		2088	=item C<PERL_ANYEVENT_VERBOSE>
		2089
		2090	By default, AnyEvent will log messages with loglevel C<4> (C<error>) or
		2091	higher (see L<AnyEvent::Log>). You can set this environment variable to a
		2092	numerical loglevel to make AnyEvent more (or less) talkative.
		2093
		2094	If you want to do more than just set the global logging level
		2095	you should have a look at C<PERL_ANYEVENT_LOG>, which allows much more
		2096	complex specifications.
		2097
		2098	When set to C<0> (C<off>), then no messages whatsoever will be logged with
		2099	everything else at defaults.
		2100
		2101	When set to C<5> or higher (C<warn>), AnyEvent warns about unexpected
		2102	conditions, such as not being able to load the event model specified by
		2103	C<PERL_ANYEVENT_MODEL>, or a guard callback throwing an exception - this
		2104	is the minimum recommended level for use during development.
		2105
		2106	When set to C<7> or higher (info), AnyEvent reports which event model it
		2107	chooses.
		2108
		2109	When set to C<8> or higher (debug), then AnyEvent will report extra
		2110	information on which optional modules it loads and how it implements
		2111	certain features.
		2112
		2113	=item C<PERL_ANYEVENT_LOG>
		2114
		2115	Accepts rather complex logging specifications. For example, you could log
		2116	all C<debug> messages of some module to stderr, warnings and above to
		2117	stderr, and errors and above to syslog, with:
		2118
		2119	PERL_ANYEVENT_LOG=Some::Module=debug,+log:filter=warn,+%syslog:%syslog=error,syslog
		2120
		2121	For the rather extensive details, see L<AnyEvent::Log>.
		2122
		2123	This variable is evaluated when AnyEvent (or L<AnyEvent::Log>) is loaded,
		2124	so will take effect even before AnyEvent has initialised itself.
		2125
		2126	Note that specifying this environment variable causes the L<AnyEvent::Log>
		2127	module to be loaded, while C<PERL_ANYEVENT_VERBOSE> does not, so only
		2128	using the latter saves a few hundred kB of memory unless a module
		2129	explicitly needs the extra features of AnyEvent::Log.
		2130
		2131	=item C<PERL_ANYEVENT_STRICT>
		2132
		2133	AnyEvent does not do much argument checking by default, as thorough
		2134	argument checking is very costly. Setting this variable to a true value
		2135	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		2136	check the arguments passed to most method calls. If it finds any problems,
		2137	it will croak.
		2138
		2139	In other words, enables "strict" mode.
		2140
		2141	Unlike C<use strict> (or its modern cousin, C<< use L<common::sense>
		2142	>>, it is definitely recommended to keep it off in production. Keeping
		2143	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		2144	can be very useful, however.
		2145
		2146	=item C<PERL_ANYEVENT_DEBUG_SHELL>
		2147
		2148	If this env variable is nonempty, then its contents will be interpreted by
		2149	C<AnyEvent::Socket::parse_hostport> and C<AnyEvent::Debug::shell> (after
		2150	replacing every occurance of C<$$> by the process pid). The shell object
		2151	is saved in C<$AnyEvent::Debug::SHELL>.
		2152
		2153	This happens when the first watcher is created.
		2154
		2155	For example, to bind a debug shell on a unix domain socket in
		2156	F<< /tmp/debug<pid>.sock >>, you could use this:
		2157
		2158	PERL_ANYEVENT_DEBUG_SHELL=/tmp/debug\$\$.sock perlprog
		2159	# connect with e.g.: socat readline /tmp/debug123.sock
		2160
		2161	Or to bind to tcp port 4545 on localhost:
		2162
		2163	PERL_ANYEVENT_DEBUG_SHELL=127.0.0.1:4545 perlprog
		2164	# connect with e.g.: telnet localhost 4545
		2165
		2166	Note that creating sockets in F</tmp> or on localhost is very unsafe on
		2167	multiuser systems.
		2168
		2169	=item C<PERL_ANYEVENT_DEBUG_WRAP>
		2170
		2171	Can be set to C<0>, C<1> or C<2> and enables wrapping of all watchers for
		2172	debugging purposes. See C<AnyEvent::Debug::wrap> for details.
		2173
		2174	=item C<PERL_ANYEVENT_MODEL>
		2175
		2176	This can be used to specify the event model to be used by AnyEvent, before
		2177	auto detection and -probing kicks in.
		2178
		2179	It normally is a string consisting entirely of ASCII letters (e.g. C<EV>
		2180	or C<IOAsync>). The string C<AnyEvent::Impl::> gets prepended and the
		2181	resulting module name is loaded and - if the load was successful - used as
		2182	event model backend. If it fails to load then AnyEvent will proceed with
		2183	auto detection and -probing.
		2184
		2185	If the string ends with C<::> instead (e.g. C<AnyEvent::Impl::EV::>) then
		2186	nothing gets prepended and the module name is used as-is (hint: C<::> at
		2187	the end of a string designates a module name and quotes it appropriately).
		2188
		2189	For example, to force the pure perl model (L<AnyEvent::Loop::Perl>) you
		2190	could start your program like this:
		2191
		2192	PERL_ANYEVENT_MODEL=Perl perl ...
		2193
		2194	=item C<PERL_ANYEVENT_IO_MODEL>
		2195
		2196	The current file I/O model - see L<AnyEvent::IO> for more info.
		2197
		2198	At the moment, only C<Perl> (small, pure-perl, synchronous) and
		2199	C<IOAIO> (truly asynchronous) are supported. The default is C<IOAIO> if
		2200	L<AnyEvent::AIO> can be loaded, otherwise it is C<Perl>.
		2201
		2202	=item C<PERL_ANYEVENT_PROTOCOLS>
		2203
		2204	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		2205	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		2206	of auto probing).
		2207
		2208	Must be set to a comma-separated list of protocols or address families,
		2209	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		2210	used, and preference will be given to protocols mentioned earlier in the
		2211	list.
		2212
		2213	This variable can effectively be used for denial-of-service attacks
		2214	against local programs (e.g. when setuid), although the impact is likely
		2215	small, as the program has to handle connection and other failures anyways.
		2216
		2217	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		2218	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		2219	- only support IPv4, never try to resolve or contact IPv6
		2220	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		2221	IPv6, but prefer IPv6 over IPv4.
		2222
		2223	=item C<PERL_ANYEVENT_HOSTS>
		2224
		2225	This variable, if specified, overrides the F</etc/hosts> file used by
		2226	L<AnyEvent::Socket>C<::resolve_sockaddr>, i.e. hosts aliases will be read
		2227	from that file instead.
		2228
		2229	=item C<PERL_ANYEVENT_EDNS0>
		2230
		2231	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension for
		2232	DNS. This extension is generally useful to reduce DNS traffic, especially
		2233	when DNSSEC is involved, but some (broken) firewalls drop such DNS
		2234	packets, which is why it is off by default.
		2235
		2236	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		2237	EDNS0 in its DNS requests.
		2238
		2239	=item C<PERL_ANYEVENT_MAX_FORKS>
		2240
		2241	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		2242	will create in parallel.
		2243
		2244	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		2245
		2246	The default value for the C<max_outstanding> parameter for the default DNS
		2247	resolver - this is the maximum number of parallel DNS requests that are
		2248	sent to the DNS server.
		2249
		2250	=item C<PERL_ANYEVENT_MAX_SIGNAL_LATENCY>
		2251
		2252	Perl has inherently racy signal handling (you can basically choose between
		2253	losing signals and memory corruption) - pure perl event loops (including
		2254	C<AnyEvent::Loop>, when C<Async::Interrupt> isn't available) therefore
		2255	have to poll regularly to avoid losing signals.
		2256
		2257	Some event loops are racy, but don't poll regularly, and some event loops
		2258	are written in C but are still racy. For those event loops, AnyEvent
		2259	installs a timer that regularly wakes up the event loop.
		2260
		2261	By default, the interval for this timer is C<10> seconds, but you can
		2262	override this delay with this environment variable (or by setting
		2263	the C<$AnyEvent::MAX_SIGNAL_LATENCY> variable before creating signal
		2264	watchers).
		2265
		2266	Lower values increase CPU (and energy) usage, higher values can introduce
		2267	long delays when reaping children or waiting for signals.
		2268
		2269	The L<AnyEvent::Async> module, if available, will be used to avoid this
		2270	polling (with most event loops).
		2271
		2272	=item C<PERL_ANYEVENT_RESOLV_CONF>
		2273
		2274	The absolute path to a F<resolv.conf>-style file to use instead of
		2275	F</etc/resolv.conf> (or the OS-specific configuration) in the default
		2276	resolver, or the empty string to select the default configuration.
		2277
		2278	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		2279
		2280	When neither C<ca_file> nor C<ca_path> was specified during
		2281	L<AnyEvent::TLS> context creation, and either of these environment
		2282	variables are nonempty, they will be used to specify CA certificate
		2283	locations instead of a system-dependent default.
		2284
		2285	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		2286
		2287	When these are set to C<1>, then the respective modules are not
		2288	loaded. Mostly good for testing AnyEvent itself.
		2289
		2290	=back
628		2291
629	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	2292	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
630		2293
631	This is an advanced topic that you do not normally need to use AnyEvent in	2294	This is an advanced topic that you do not normally need to use AnyEvent in
632	a module. This section is only of use to event loop authors who want to	2295	a module. This section is only of use to event loop authors who want to
…		…
667	I<rxvt-unicode> also cheats a bit by not providing blocking access to	2330	I<rxvt-unicode> also cheats a bit by not providing blocking access to
668	condition variables: code blocking while waiting for a condition will	2331	condition variables: code blocking while waiting for a condition will
669	C<die>. This still works with most modules/usages, and blocking calls must	2332	C<die>. This still works with most modules/usages, and blocking calls must
670	not be done in an interactive application, so it makes sense.	2333	not be done in an interactive application, so it makes sense.
671		2334
672	=head1 ENVIRONMENT VARIABLES
673
674	The following environment variables are used by this module:
675
676	=over 4
677
678	=item C<PERL_ANYEVENT_VERBOSE>
679
680	By default, AnyEvent will be completely silent except in fatal
681	conditions. You can set this environment variable to make AnyEvent more
682	talkative.
683
684	When set to C<1> or higher, causes AnyEvent to warn about unexpected
685	conditions, such as not being able to load the event model specified by
686	C<PERL_ANYEVENT_MODEL>.
687
688	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
689	model it chooses.
690
691	=item C<PERL_ANYEVENT_MODEL>
692
693	This can be used to specify the event model to be used by AnyEvent, before
694	autodetection and -probing kicks in. It must be a string consisting
695	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
696	and the resulting module name is loaded and if the load was successful,
697	used as event model. If it fails to load AnyEvent will proceed with
698	autodetection and -probing.
699
700	This functionality might change in future versions.
701
702	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
703	could start your program like this:
704
705	PERL_ANYEVENT_MODEL=Perl perl ...
706
707	=back
708
709	=head1 EXAMPLE PROGRAM	2335	=head1 EXAMPLE PROGRAM
710		2336
711	The following program uses an IO watcher to read data from STDIN, a timer	2337	The following program uses an I/O watcher to read data from STDIN, a timer
712	to display a message once per second, and a condition variable to quit the	2338	to display a message once per second, and a condition variable to quit the
713	program when the user enters quit:	2339	program when the user enters quit:
714		2340
715	use AnyEvent;	2341	use AnyEvent;
716		2342
…		…
721	poll => 'r',	2347	poll => 'r',
722	cb => sub {	2348	cb => sub {
723	warn "io event <$_[0]>\n"; # will always output <r>	2349	warn "io event <$_[0]>\n"; # will always output <r>
724	chomp (my $input = <STDIN>); # read a line	2350	chomp (my $input = <STDIN>); # read a line
725	warn "read: $input\n"; # output what has been read	2351	warn "read: $input\n"; # output what has been read
726	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	2352	$cv->send if $input =~ /^q/i; # quit program if /^q/i
727	},	2353	},
728	);	2354	);
729		2355
730	my $time_watcher; # can only be used once
731
732	sub new_timer {
733	$timer = AnyEvent->timer (after => 1, cb => sub {	2356	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
734	warn "timeout\n"; # print 'timeout' about every second	2357	warn "timeout\n"; # print 'timeout' at most every second
735	&new_timer; # and restart the time
736	});	2358	});
737	}
738		2359
739	new_timer; # create first timer
740
741	$cv->wait; # wait until user enters /^q/i	2360	$cv->recv; # wait until user enters /^q/i
742		2361
743	=head1 REAL-WORLD EXAMPLE	2362	=head1 REAL-WORLD EXAMPLE
744		2363
745	Consider the L<Net::FCP> module. It features (among others) the following	2364	Consider the L<Net::FCP> module. It features (among others) the following
746	API calls, which are to freenet what HTTP GET requests are to http:	2365	API calls, which are to freenet what HTTP GET requests are to http:
…		…
796	syswrite $txn->{fh}, $txn->{request}	2415	syswrite $txn->{fh}, $txn->{request}
797	or die "connection or write error";	2416	or die "connection or write error";
798	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	2417	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
799		2418
800	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	2419	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
801	result and signals any possible waiters that the request ahs finished:	2420	result and signals any possible waiters that the request has finished:
802		2421
803	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	2422	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
804		2423
805	if (end-of-file or data complete) {	2424	if (end-of-file or data complete) {
806	$txn->{result} = $txn->{buf};	2425	$txn->{result} = $txn->{buf};
807	$txn->{finished}->broadcast;	2426	$txn->{finished}->send;
808	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	2427	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
809	}	2428	}
810		2429
811	The C<result> method, finally, just waits for the finished signal (if the	2430	The C<result> method, finally, just waits for the finished signal (if the
812	request was already finished, it doesn't wait, of course, and returns the	2431	request was already finished, it doesn't wait, of course, and returns the
813	data:	2432	data:
814		2433
815	$txn->{finished}->wait;	2434	$txn->{finished}->recv;
816	return $txn->{result};	2435	return $txn->{result};
817		2436
818	The actual code goes further and collects all errors (C<die>s, exceptions)	2437	The actual code goes further and collects all errors (C<die>s, exceptions)
819	that occured during request processing. The C<result> method detects	2438	that occurred during request processing. The C<result> method detects
820	whether an exception as thrown (it is stored inside the $txn object)	2439	whether an exception as thrown (it is stored inside the $txn object)
821	and just throws the exception, which means connection errors and other	2440	and just throws the exception, which means connection errors and other
822	problems get reported tot he code that tries to use the result, not in a	2441	problems get reported to the code that tries to use the result, not in a
823	random callback.	2442	random callback.
824		2443
825	All of this enables the following usage styles:	2444	All of this enables the following usage styles:
826		2445
827	1. Blocking:	2446	1. Blocking:
…		…
855		2474
856	my $quit = AnyEvent->condvar;	2475	my $quit = AnyEvent->condvar;
857		2476
858	$fcp->txn_client_get ($url)->cb (sub {	2477	$fcp->txn_client_get ($url)->cb (sub {
859	...	2478	...
860	$quit->broadcast;	2479	$quit->send;
861	});	2480	});
862		2481
863	$quit->wait;	2482	$quit->recv;
864		2483
865		2484
866	=head1 BENCHMARK	2485	=head1 BENCHMARKS
867		2486
868	To give you an idea of the performance and overheads that AnyEvent adds	2487	To give you an idea of the performance and overheads that AnyEvent adds
869	over the backends directly, here is a benchmark of various supported event	2488	over the event loops themselves and to give you an impression of the speed
870	models natively and with anyevent. The benchmark creates a lot of timers	2489	of various event loops I prepared some benchmarks.
		2490
		2491	=head2 BENCHMARKING ANYEVENT OVERHEAD
		2492
		2493	Here is a benchmark of various supported event models used natively and
		2494	through AnyEvent. The benchmark creates a lot of timers (with a zero
871	(with a zero timeout) and io watchers (watching STDOUT, a pty, to become	2495	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
872	writable, which it is), lets them fire exactly once and destroys them	2496	which it is), lets them fire exactly once and destroys them again.
873	again.
874		2497
875	Explanation of the fields:	2498	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
		2499	distribution. It uses the L<AE> interface, which makes a real difference
		2500	for the EV and Perl backends only.
876		2501
		2502	=head3 Explanation of the columns
		2503
877	I<watcher> is the number of event watchers created/destroyed. Sicne	2504	I<watcher> is the number of event watchers created/destroyed. Since
878	different event models have vastly different performance each backend was	2505	different event models feature vastly different performances, each event
879	handed a number of watchers so that overall runtime is acceptable and	2506	loop was given a number of watchers so that overall runtime is acceptable
880	similar to all backends (and keep them from crashing).	2507	and similar between tested event loop (and keep them from crashing): Glib
		2508	would probably take thousands of years if asked to process the same number
		2509	of watchers as EV in this benchmark.
881		2510
882	I<bytes> is the number of bytes (as measured by resident set size) used by	2511	I<bytes> is the number of bytes (as measured by the resident set size,
883	each watcher.	2512	RSS) consumed by each watcher. This method of measuring captures both C
		2513	and Perl-based overheads.
884		2514
885	I<create> is the time, in microseconds, to create a single watcher.	2515	I<create> is the time, in microseconds (millionths of seconds), that it
		2516	takes to create a single watcher. The callback is a closure shared between
		2517	all watchers, to avoid adding memory overhead. That means closure creation
		2518	and memory usage is not included in the figures.
886		2519
887	I<invoke> is the time, in microseconds, used to invoke a simple callback	2520	I<invoke> is the time, in microseconds, used to invoke a simple
888	that simply counts down.	2521	callback. The callback simply counts down a Perl variable and after it was
		2522	invoked "watcher" times, it would C<< ->send >> a condvar once to
		2523	signal the end of this phase.
889		2524
890	I<destroy> is the time, in microseconds, to destroy a single watcher.	2525	I<destroy> is the time, in microseconds, that it takes to destroy a single
		2526	watcher.
891		2527
		2528	=head3 Results
		2529
892	name watcher bytes create invoke destroy comment	2530	name watchers bytes create invoke destroy comment
893	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	2531	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
894	EV/Any 100000 610 3.52 0.91 0.75	2532	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
895	CoroEV/Any 100000 610 3.49 0.92 0.75 coroutines + Coro::Signal	2533	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
896	Perl/Any 10000 654 4.64 1.22 0.77 pure perl implementation	2534	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
897	Event/Event 10000 523 28.05 21.38 5.22 Event native interface	2535	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
898	Event/Any 10000 943 34.43 20.48 1.39	2536	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
		2537	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
		2538	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
899	Glib/Any 16000 1357 96.99 12.55 55.51 quadratic behaviour	2539	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
900	Tk/Any 2000 1855 27.01 66.61 14.03 SEGV with >> 2000 watchers	2540	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
901	POE/Select 2000 6343 94.69 807.65 562.69 POE::Loop::Select	2541	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
902	POE/Event 2000 6644 108.15 768.19 14.33 POE::Loop::Event	2542	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
903		2543
904	Discussion: The benchmark does I<not> bench scalability of the	2544	=head3 Discussion
		2545
		2546	The benchmark does I<not> measure scalability of the event loop very
905	backend. For example a select-based backend (such as the pureperl one) can	2547	well. For example, a select-based event loop (such as the pure perl one)
906	never compete with a backend using epoll. In this benchmark, only a single	2548	can never compete with an event loop that uses epoll when the number of
907	filehandle is used.	2549	file descriptors grows high. In this benchmark, all events become ready at
		2550	the same time, so select/poll-based implementations get an unnatural speed
		2551	boost.
908		2552
		2553	Also, note that the number of watchers usually has a nonlinear effect on
		2554	overall speed, that is, creating twice as many watchers doesn't take twice
		2555	the time - usually it takes longer. This puts event loops tested with a
		2556	higher number of watchers at a disadvantage.
		2557
		2558	To put the range of results into perspective, consider that on the
		2559	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		2560	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		2561	cycles with POE.
		2562
909	EV is the sole leader regarding speed and memory use, which are both	2563	C<EV> is the sole leader regarding speed and memory use, which are both
910	maximal/minimal. Even when going through AnyEvent, there is only one event	2564	maximal/minimal, respectively. When using the L<AE> API there is zero
911	loop that uses less memory (the Event module natively), and no faster	2565	overhead (when going through the AnyEvent API create is about 5-6 times
912	event model.	2566	slower, with other times being equal, so still uses far less memory than
		2567	any other event loop and is still faster than Event natively).
913		2568
914	The pure perl implementation is hit in a few sweet spots (both the	2569	The pure perl implementation is hit in a few sweet spots (both the
915	zero timeout and the use of a single fd hit optimisations in the perl	2570	constant timeout and the use of a single fd hit optimisations in the perl
916	interpreter and the backend itself), but it shows that it adds very little	2571	interpreter and the backend itself). Nevertheless this shows that it
917	overhead in itself. Like any select-based backend it's performance becomes	2572	adds very little overhead in itself. Like any select-based backend its
918	really bad with lots of file descriptors.	2573	performance becomes really bad with lots of file descriptors (and few of
		2574	them active), of course, but this was not subject of this benchmark.
919		2575
920	The Event module has a relatively high setup and callback invocation cost,	2576	The C<Event> module has a relatively high setup and callback invocation
921	but overall scores on the third place.	2577	cost, but overall scores in on the third place.
922		2578
923	Glib has a little higher memory cost, a bit fster callback invocation and	2579	C<IO::Async> performs admirably well, about on par with C<Event>, even
924	has a similar speed as Event.	2580	when using its pure perl backend.
925		2581
		2582	C<Glib>'s memory usage is quite a bit higher, but it features a
		2583	faster callback invocation and overall ends up in the same class as
		2584	C<Event>. However, Glib scales extremely badly, doubling the number of
		2585	watchers increases the processing time by more than a factor of four,
		2586	making it completely unusable when using larger numbers of watchers
		2587	(note that only a single file descriptor was used in the benchmark, so
		2588	inefficiencies of C<poll> do not account for this).
		2589
926	The Tk backend works relatively well, the fact that it crashes with	2590	The C<Tk> adaptor works relatively well. The fact that it crashes with
927	more than 2000 watchers is a big setback, however, as correctness takes	2591	more than 2000 watchers is a big setback, however, as correctness takes
928	precedence over speed.	2592	precedence over speed. Nevertheless, its performance is surprising, as the
		2593	file descriptor is dup()ed for each watcher. This shows that the dup()
		2594	employed by some adaptors is not a big performance issue (it does incur a
		2595	hidden memory cost inside the kernel which is not reflected in the figures
		2596	above).
929		2597
930	POE, regardless of backend (wether it's pure perl select backend or the	2598	C<POE>, regardless of underlying event loop (whether using its pure perl
931	Event backend) shows abysmal performance and memory usage: Watchers use	2599	select-based backend or the Event module, the POE-EV backend couldn't
932	almost 30 times as much memory as EV watchers, and 10 times as much memory	2600	be tested because it wasn't working) shows abysmal performance and
933	as both Event or EV via AnyEvent.	2601	memory usage with AnyEvent: Watchers use almost 30 times as much memory
		2602	as EV watchers, and 10 times as much memory as Event (the high memory
		2603	requirements are caused by requiring a session for each watcher). Watcher
		2604	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		2605	implementation.
934		2606
		2607	The design of the POE adaptor class in AnyEvent can not really account
		2608	for the performance issues, though, as session creation overhead is
		2609	small compared to execution of the state machine, which is coded pretty
		2610	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		2611	using multiple sessions is not a good approach, especially regarding
		2612	memory usage, even the author of POE could not come up with a faster
		2613	design).
		2614
		2615	=head3 Summary
		2616
		2617	=over 4
		2618
935	Summary: using EV through AnyEvent is faster than any other event	2619	=item * Using EV through AnyEvent is faster than any other event loop
936	loop. The overhead AnyEvent adds can be very small, and you should avoid	2620	(even when used without AnyEvent), but most event loops have acceptable
937	POE like the plague if you want performance or reasonable memory usage.	2621	performance with or without AnyEvent.
		2622
		2623	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
		2624	the actual event loop, only with extremely fast event loops such as EV
		2625	does AnyEvent add significant overhead.
		2626
		2627	=item * You should avoid POE like the plague if you want performance or
		2628	reasonable memory usage.
		2629
		2630	=back
		2631
		2632	=head2 BENCHMARKING THE LARGE SERVER CASE
		2633
		2634	This benchmark actually benchmarks the event loop itself. It works by
		2635	creating a number of "servers": each server consists of a socket pair, a
		2636	timeout watcher that gets reset on activity (but never fires), and an I/O
		2637	watcher waiting for input on one side of the socket. Each time the socket
		2638	watcher reads a byte it will write that byte to a random other "server".
		2639
		2640	The effect is that there will be a lot of I/O watchers, only part of which
		2641	are active at any one point (so there is a constant number of active
		2642	fds for each loop iteration, but which fds these are is random). The
		2643	timeout is reset each time something is read because that reflects how
		2644	most timeouts work (and puts extra pressure on the event loops).
		2645
		2646	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
		2647	(1%) are active. This mirrors the activity of large servers with many
		2648	connections, most of which are idle at any one point in time.
		2649
		2650	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		2651	distribution. It uses the L<AE> interface, which makes a real difference
		2652	for the EV and Perl backends only.
		2653
		2654	=head3 Explanation of the columns
		2655
		2656	I<sockets> is the number of sockets, and twice the number of "servers" (as
		2657	each server has a read and write socket end).
		2658
		2659	I<create> is the time it takes to create a socket pair (which is
		2660	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		2661
		2662	I<request>, the most important value, is the time it takes to handle a
		2663	single "request", that is, reading the token from the pipe and forwarding
		2664	it to another server. This includes deleting the old timeout and creating
		2665	a new one that moves the timeout into the future.
		2666
		2667	=head3 Results
		2668
		2669	name sockets create request
		2670	EV 20000 62.66 7.99
		2671	Perl 20000 68.32 32.64
		2672	IOAsync 20000 174.06 101.15 epoll
		2673	IOAsync 20000 174.67 610.84 poll
		2674	Event 20000 202.69 242.91
		2675	Glib 20000 557.01 1689.52
		2676	POE 20000 341.54 12086.32 uses POE::Loop::Event
		2677
		2678	=head3 Discussion
		2679
		2680	This benchmark I<does> measure scalability and overall performance of the
		2681	particular event loop.
		2682
		2683	EV is again fastest. Since it is using epoll on my system, the setup time
		2684	is relatively high, though.
		2685
		2686	Perl surprisingly comes second. It is much faster than the C-based event
		2687	loops Event and Glib.
		2688
		2689	IO::Async performs very well when using its epoll backend, and still quite
		2690	good compared to Glib when using its pure perl backend.
		2691
		2692	Event suffers from high setup time as well (look at its code and you will
		2693	understand why). Callback invocation also has a high overhead compared to
		2694	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		2695	uses select or poll in basically all documented configurations.
		2696
		2697	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		2698	clearly fails to perform with many filehandles or in busy servers.
		2699
		2700	POE is still completely out of the picture, taking over 1000 times as long
		2701	as EV, and over 100 times as long as the Perl implementation, even though
		2702	it uses a C-based event loop in this case.
		2703
		2704	=head3 Summary
		2705
		2706	=over 4
		2707
		2708	=item * The pure perl implementation performs extremely well.
		2709
		2710	=item * Avoid Glib or POE in large projects where performance matters.
		2711
		2712	=back
		2713
		2714	=head2 BENCHMARKING SMALL SERVERS
		2715
		2716	While event loops should scale (and select-based ones do not...) even to
		2717	large servers, most programs we (or I :) actually write have only a few
		2718	I/O watchers.
		2719
		2720	In this benchmark, I use the same benchmark program as in the large server
		2721	case, but it uses only eight "servers", of which three are active at any
		2722	one time. This should reflect performance for a small server relatively
		2723	well.
		2724
		2725	The columns are identical to the previous table.
		2726
		2727	=head3 Results
		2728
		2729	name sockets create request
		2730	EV 16 20.00 6.54
		2731	Perl 16 25.75 12.62
		2732	Event 16 81.27 35.86
		2733	Glib 16 32.63 15.48
		2734	POE 16 261.87 276.28 uses POE::Loop::Event
		2735
		2736	=head3 Discussion
		2737
		2738	The benchmark tries to test the performance of a typical small
		2739	server. While knowing how various event loops perform is interesting, keep
		2740	in mind that their overhead in this case is usually not as important, due
		2741	to the small absolute number of watchers (that is, you need efficiency and
		2742	speed most when you have lots of watchers, not when you only have a few of
		2743	them).
		2744
		2745	EV is again fastest.
		2746
		2747	Perl again comes second. It is noticeably faster than the C-based event
		2748	loops Event and Glib, although the difference is too small to really
		2749	matter.
		2750
		2751	POE also performs much better in this case, but is is still far behind the
		2752	others.
		2753
		2754	=head3 Summary
		2755
		2756	=over 4
		2757
		2758	=item * C-based event loops perform very well with small number of
		2759	watchers, as the management overhead dominates.
		2760
		2761	=back
		2762
		2763	=head2 THE IO::Lambda BENCHMARK
		2764
		2765	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2766	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2767	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2768	shouldn't come as a surprise to anybody). As such, the benchmark is
		2769	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2770	very optimal. But how would AnyEvent compare when used without the extra
		2771	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2772
		2773	The benchmark itself creates an echo-server, and then, for 500 times,
		2774	connects to the echo server, sends a line, waits for the reply, and then
		2775	creates the next connection. This is a rather bad benchmark, as it doesn't
		2776	test the efficiency of the framework or much non-blocking I/O, but it is a
		2777	benchmark nevertheless.
		2778
		2779	name runtime
		2780	Lambda/select 0.330 sec
		2781	+ optimized 0.122 sec
		2782	Lambda/AnyEvent 0.327 sec
		2783	+ optimized 0.138 sec
		2784	Raw sockets/select 0.077 sec
		2785	POE/select, components 0.662 sec
		2786	POE/select, raw sockets 0.226 sec
		2787	POE/select, optimized 0.404 sec
		2788
		2789	AnyEvent/select/nb 0.085 sec
		2790	AnyEvent/EV/nb 0.068 sec
		2791	+state machine 0.134 sec
		2792
		2793	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2794	benchmarks actually make blocking connects and use 100% blocking I/O,
		2795	defeating the purpose of an event-based solution. All of the newly
		2796	written AnyEvent benchmarks use 100% non-blocking connects (using
		2797	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2798	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2799	generally require a lot more bookkeeping and event handling than blocking
		2800	connects (which involve a single syscall only).
		2801
		2802	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2803	offers similar expressive power as POE and IO::Lambda, using conventional
		2804	Perl syntax. This means that both the echo server and the client are 100%
		2805	non-blocking, further placing it at a disadvantage.
		2806
		2807	As you can see, the AnyEvent + EV combination even beats the
		2808	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2809	backend easily beats IO::Lambda and POE.
		2810
		2811	And even the 100% non-blocking version written using the high-level (and
		2812	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda
		2813	higher level ("unoptimised") abstractions by a large margin, even though
		2814	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
		2815
		2816	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2817	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2818	part of the IO::Lambda distribution and were used without any changes.
		2819
		2820
		2821	=head1 SIGNALS
		2822
		2823	AnyEvent currently installs handlers for these signals:
		2824
		2825	=over 4
		2826
		2827	=item SIGCHLD
		2828
		2829	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2830	emulation for event loops that do not support them natively. Also, some
		2831	event loops install a similar handler.
		2832
		2833	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2834	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2835
		2836	=item SIGPIPE
		2837
		2838	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2839	when AnyEvent gets loaded.
		2840
		2841	The rationale for this is that AnyEvent users usually do not really depend
		2842	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2843	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2844	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2845	some random socket.
		2846
		2847	The rationale for installing a no-op handler as opposed to ignoring it is
		2848	that this way, the handler will be restored to defaults on exec.
		2849
		2850	Feel free to install your own handler, or reset it to defaults.
		2851
		2852	=back
		2853
		2854	=cut
		2855
		2856	undef $SIG{CHLD}
		2857	if $SIG{CHLD} eq 'IGNORE';
		2858
		2859	$SIG{PIPE} = sub { }
		2860	unless defined $SIG{PIPE};
		2861
		2862	=head1 RECOMMENDED/OPTIONAL MODULES
		2863
		2864	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2865	its built-in modules) are required to use it.
		2866
		2867	That does not mean that AnyEvent won't take advantage of some additional
		2868	modules if they are installed.
		2869
		2870	This section explains which additional modules will be used, and how they
		2871	affect AnyEvent's operation.
		2872
		2873	=over 4
		2874
		2875	=item L<Async::Interrupt>
		2876
		2877	This slightly arcane module is used to implement fast signal handling: To
		2878	my knowledge, there is no way to do completely race-free and quick
		2879	signal handling in pure perl. To ensure that signals still get
		2880	delivered, AnyEvent will start an interval timer to wake up perl (and
		2881	catch the signals) with some delay (default is 10 seconds, look for
		2882	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2883
		2884	If this module is available, then it will be used to implement signal
		2885	catching, which means that signals will not be delayed, and the event loop
		2886	will not be interrupted regularly, which is more efficient (and good for
		2887	battery life on laptops).
		2888
		2889	This affects not just the pure-perl event loop, but also other event loops
		2890	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2891
		2892	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2893	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2894	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2895	does nothing for those backends.
		2896
		2897	=item L<EV>
		2898
		2899	This module isn't really "optional", as it is simply one of the backend
		2900	event loops that AnyEvent can use. However, it is simply the best event
		2901	loop available in terms of features, speed and stability: It supports
		2902	the AnyEvent API optimally, implements all the watcher types in XS, does
		2903	automatic timer adjustments even when no monotonic clock is available,
		2904	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2905	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2906	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2907
		2908	If you only use backends that rely on another event loop (e.g. C<Tk>),
		2909	then this module will do nothing for you.
		2910
		2911	=item L<Guard>
		2912
		2913	The guard module, when used, will be used to implement
		2914	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2915	lot less memory), but otherwise doesn't affect guard operation much. It is
		2916	purely used for performance.
		2917
		2918	=item L<JSON> and L<JSON::XS>
		2919
		2920	One of these modules is required when you want to read or write JSON data
		2921	via L<AnyEvent::Handle>. L<JSON> is also written in pure-perl, but can take
		2922	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2923
		2924	=item L<Net::SSLeay>
		2925
		2926	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2927	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2928	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2929
		2930	=item L<Time::HiRes>
		2931
		2932	This module is part of perl since release 5.008. It will be used when the
		2933	chosen event library does not come with a timing source of its own. The
		2934	pure-perl event loop (L<AnyEvent::Loop>) will additionally load it to
		2935	try to use a monotonic clock for timing stability.
		2936
		2937	=item L<AnyEvent::AIO> (and L<IO::AIO>)
		2938
		2939	The default implementation of L<AnyEvent::IO> is to do I/O synchronously,
		2940	stopping programs while they access the disk, which is fine for a lot of
		2941	programs.
		2942
		2943	Installing AnyEvent::AIO (and its IO::AIO dependency) makes it switch to
		2944	a true asynchronous implementation, so event processing can continue even
		2945	while waiting for disk I/O.
		2946
		2947	=back
938		2948
939		2949
940	=head1 FORK	2950	=head1 FORK
941		2951
942	Most event libraries are not fork-safe. The ones who are usually are	2952	Most event libraries are not fork-safe. The ones who are usually are
943	because they are so inefficient. Only L<EV> is fully fork-aware.	2953	because they rely on inefficient but fork-safe C<select> or C<poll> calls
		2954	- higher performance APIs such as BSD's kqueue or the dreaded Linux epoll
		2955	are usually badly thought-out hacks that are incompatible with fork in
		2956	one way or another. Only L<EV> is fully fork-aware and ensures that you
		2957	continue event-processing in both parent and child (or both, if you know
		2958	what you are doing).
		2959
		2960	This means that, in general, you cannot fork and do event processing in
		2961	the child if the event library was initialised before the fork (which
		2962	usually happens when the first AnyEvent watcher is created, or the library
		2963	is loaded).
944		2964
945	If you have to fork, you must either do so I<before> creating your first	2965	If you have to fork, you must either do so I<before> creating your first
946	watcher OR you must not use AnyEvent at all in the child.	2966	watcher OR you must not use AnyEvent at all in the child OR you must do
		2967	something completely out of the scope of AnyEvent (see below).
		2968
		2969	The problem of doing event processing in the parent I<and> the child
		2970	is much more complicated: even for backends that I<are> fork-aware or
		2971	fork-safe, their behaviour is not usually what you want: fork clones all
		2972	watchers, that means all timers, I/O watchers etc. are active in both
		2973	parent and child, which is almost never what you want. Using C<exec>
		2974	to start worker children from some kind of manage prrocess is usually
		2975	preferred, because it is much easier and cleaner, at the expense of having
		2976	to have another binary.
		2977
		2978	In addition to logical problems with fork, there are also implementation
		2979	problems. For example, on POSIX systems, you cannot fork at all in Perl
		2980	code if a thread (I am talking of pthreads here) was ever created in the
		2981	process, and this is just the tip of the iceberg. In general, using fork
		2982	from Perl is difficult, and attempting to use fork without an exec to
		2983	implement some kind of parallel processing is almost certainly doomed.
		2984
		2985	To safely fork and exec, you should use a module such as
		2986	L<Proc::FastSpawn> that let's you safely fork and exec new processes.
		2987
		2988	If you want to do multiprocessing using processes, you can
		2989	look at the L<AnyEvent::Fork> module (and some related modules
		2990	such as L<AnyEvent::Fork::RPC>, L<AnyEvent::Fork::Pool> and
		2991	L<AnyEvent::Fork::Remote>). This module allows you to safely create
		2992	subprocesses without any limitations - you can use X11 toolkits or
		2993	AnyEvent in the children created by L<AnyEvent::Fork> safely and without
		2994	any special precautions.
947		2995
948		2996
949	=head1 SECURITY CONSIDERATIONS	2997	=head1 SECURITY CONSIDERATIONS
950		2998
951	AnyEvent can be forced to load any event model via	2999	AnyEvent can be forced to load any event model via
…		…
956	specified in the variable.	3004	specified in the variable.
957		3005
958	You can make AnyEvent completely ignore this variable by deleting it	3006	You can make AnyEvent completely ignore this variable by deleting it
959	before the first watcher gets created, e.g. with a C<BEGIN> block:	3007	before the first watcher gets created, e.g. with a C<BEGIN> block:
960		3008
961	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	3009	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
962		3010
963	use AnyEvent;	3011	use AnyEvent;
		3012
		3013	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		3014	be used to probe what backend is used and gain other information (which is
		3015	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		3016	$ENV{PERL_ANYEVENT_STRICT}.
		3017
		3018	Note that AnyEvent will remove I<all> environment variables starting with
		3019	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		3020	enabled.
		3021
		3022
		3023	=head1 BUGS
		3024
		3025	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		3026	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		3027	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		3028	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		3029	pronounced).
964		3030
965		3031
966	=head1 SEE ALSO	3032	=head1 SEE ALSO
967		3033
968	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	3034	Tutorial/Introduction: L<AnyEvent::Intro>.
969	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,
970	L<Event::Lib>, L<Qt>, L<POE>.
971		3035
972	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	3036	FAQ: L<AnyEvent::FAQ>.
		3037
		3038	Utility functions: L<AnyEvent::Util> (misc. grab-bag), L<AnyEvent::Log>
		3039	(simply logging).
		3040
		3041	Development/Debugging: L<AnyEvent::Strict> (stricter checking),
		3042	L<AnyEvent::Debug> (interactive shell, watcher tracing).
		3043
		3044	Supported event modules: L<AnyEvent::Loop>, L<EV>, L<EV::Glib>,
		3045	L<Glib::EV>, L<Event>, L<Glib::Event>, L<Glib>, L<Tk>, L<Event::Lib>,
		3046	L<Qt>, L<POE>, L<FLTK>.
		3047
		3048	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
		3049	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
		3050	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
973	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,	3051	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>, L<Anyevent::Impl::Irssi>,
974	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,	3052	L<AnyEvent::Impl::FLTK>.
975	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.
976		3053
		3054	Non-blocking handles, pipes, stream sockets, TCP clients and
		3055	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
		3056
		3057	Asynchronous File I/O: L<AnyEvent::IO>.
		3058
		3059	Asynchronous DNS: L<AnyEvent::DNS>.
		3060
		3061	Thread support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
		3062
977	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	3063	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::IRC>,
		3064	L<AnyEvent::HTTP>.
978		3065
979		3066
980	=head1 AUTHOR	3067	=head1 AUTHOR
981		3068
982	Marc Lehmann <schmorp@schmorp.de>	3069	Marc Lehmann <schmorp@schmorp.de>
983	http://home.schmorp.de/	3070	http://anyevent.schmorp.de
984		3071
985	=cut	3072	=cut
986		3073
987	1	3074	1
988		3075

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