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Revision 1.415 by root, Wed Sep 25 11:16:25 2013 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, 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
20	$w->send; # wake up current and all future recv's	38	$w->send; # wake up current and all future recv's
21	$w->recv; # enters "main loop" till $condvar gets ->send	39	$w->recv; # enters "main loop" till $condvar gets ->send
		40	# use a condvar in callback mode:
		41	$w->cb (sub { $_[0]->recv });
		42
		43	=head1 INTRODUCTION/TUTORIAL
		44
		45	This manpage is mainly a reference manual. If you are interested
		46	in a tutorial or some gentle introduction, have a look at the
		47	L<AnyEvent::Intro> manpage.
		48
		49	=head1 SUPPORT
		50
		51	An FAQ document is available as L<AnyEvent::FAQ>.
		52
		53	There also is a mailinglist for discussing all things AnyEvent, and an IRC
		54	channel, too.
		55
		56	See the AnyEvent project page at the B<Schmorpforge Ta-Sa Software
		57	Repository>, at L<http://anyevent.schmorp.de>, for more info.
22		58
23	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)	59	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
24		60
25	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	61	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
26	nowadays. So what is different about AnyEvent?	62	nowadays. So what is different about AnyEvent?
27		63
28	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of	64	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
29	policy> and AnyEvent is I<small and efficient>.	65	policy> and AnyEvent is I<small and efficient>.
30		66
31	First and foremost, I<AnyEvent is not an event model> itself, it only	67	First and foremost, I<AnyEvent is not an event model> itself, it only
32	interfaces to whatever event model the main program happens to use in a	68	interfaces to whatever event model the main program happens to use, in a
33	pragmatic way. For event models and certain classes of immortals alike,	69	pragmatic way. For event models and certain classes of immortals alike,
34	the statement "there can only be one" is a bitter reality: In general,	70	the statement "there can only be one" is a bitter reality: In general,
35	only one event loop can be active at the same time in a process. AnyEvent	71	only one event loop can be active at the same time in a process. AnyEvent
36	helps hiding the differences between those event loops.	72	cannot change this, but it can hide the differences between those event
		73	loops.
37		74
38	The goal of AnyEvent is to offer module authors the ability to do event	75	The goal of AnyEvent is to offer module authors the ability to do event
39	programming (waiting for I/O or timer events) without subscribing to a	76	programming (waiting for I/O or timer events) without subscribing to a
40	religion, a way of living, and most importantly: without forcing your	77	religion, a way of living, and most importantly: without forcing your
41	module users into the same thing by forcing them to use the same event	78	module users into the same thing by forcing them to use the same event
42	model you use.	79	model you use.
43		80
44	For modules like POE or IO::Async (which is a total misnomer as it is	81	For modules like POE or IO::Async (which is a total misnomer as it is
45	actually doing all I/O I<synchronously>...), using them in your module is	82	actually doing all I/O I<synchronously>...), using them in your module is
46	like joining a cult: After you joined, you are dependent on them and you	83	like joining a cult: After you join, you are dependent on them and you
47	cannot use anything else, as it is simply incompatible to everything that	84	cannot use anything else, as they are simply incompatible to everything
48	isn't itself. What's worse, all the potential users of your module are	85	that isn't them. What's worse, all the potential users of your
49	I<also> forced to use the same event loop you use.	86	module are I<also> forced to use the same event loop you use.
50		87
51	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	88	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
52	fine. AnyEvent + Tk works fine etc. etc. but none of these work together	89	fine. AnyEvent + Tk works fine etc. etc. but none of these work together
53	with the rest: POE + IO::Async? no go. Tk + Event? no go. Again: if	90	with the rest: POE + EV? No go. Tk + Event? No go. Again: if your module
54	your module uses one of those, every user of your module has to use it,	91	uses one of those, every user of your module has to use it, too. But if
55	too. But if your module uses AnyEvent, it works transparently with all	92	your module uses AnyEvent, it works transparently with all event models it
56	event models it supports (including stuff like POE and IO::Async, as long	93	supports (including stuff like IO::Async, as long as those use one of the
57	as those use one of the supported event loops. It is trivial to add new	94	supported event loops. It is easy to add new event loops to AnyEvent, too,
58	event loops to AnyEvent, too, so it is future-proof).	95	so it is future-proof).
59		96
60	In addition to being free of having to use I<the one and only true event	97	In addition to being free of having to use I<the one and only true event
61	model>, AnyEvent also is free of bloat and policy: with POE or similar	98	model>, AnyEvent also is free of bloat and policy: with POE or similar
62	modules, you get an enourmous amount of code and strict rules you have to	99	modules, you get an enormous amount of code and strict rules you have to
63	follow. AnyEvent, on the other hand, is lean and up to the point, by only	100	follow. AnyEvent, on the other hand, is lean and to the point, by only
64	offering the functionality that is necessary, in as thin as a wrapper as	101	offering the functionality that is necessary, in as thin as a wrapper as
65	technically possible.	102	technically possible.
66		103
		104	Of course, AnyEvent comes with a big (and fully optional!) toolbox
		105	of useful functionality, such as an asynchronous DNS resolver, 100%
		106	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
		107	such as Windows) and lots of real-world knowledge and workarounds for
		108	platform bugs and differences.
		109
67	Of course, if you want lots of policy (this can arguably be somewhat	110	Now, if you I<do want> lots of policy (this can arguably be somewhat
68	useful) and you want to force your users to use the one and only event	111	useful) and you want to force your users to use the one and only event
69	model, you should I<not> use this module.	112	model, you should I<not> use this module.
70		113
71	=head1 DESCRIPTION	114	=head1 DESCRIPTION
72		115
73	L<AnyEvent> provides an identical interface to multiple event loops. This	116	L<AnyEvent> provides a uniform interface to various event loops. This
74	allows module authors to utilise an event loop without forcing module	117	allows module authors to use event loop functionality without forcing
75	users to use the same event loop (as only a single event loop can coexist	118	module users to use a specific event loop implementation (since more
76	peacefully at any one time).	119	than one event loop cannot coexist peacefully).
77		120
78	The interface itself is vaguely similar, but not identical to the L<Event>	121	The interface itself is vaguely similar, but not identical to the L<Event>
79	module.	122	module.
80		123
81	During the first call of any watcher-creation method, the module tries	124	During the first call of any watcher-creation method, the module tries
82	to detect the currently loaded event loop by probing whether one of the	125	to detect the currently loaded event loop by probing whether one of the
83	following modules is already loaded: L<EV>,	126	following modules is already loaded: L<EV>, L<AnyEvent::Loop>,
84	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,	127	L<Event>, L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>. The first one
85	L<POE>. The first one found is used. If none are found, the module tries	128	found is used. If none are detected, the module tries to load the first
86	to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl	129	four modules in the order given; but note that if L<EV> is not
87	adaptor should always succeed) in the order given. The first one that can	130	available, the pure-perl L<AnyEvent::Loop> should always work, so
88	be successfully loaded will be used. If, after this, still none could be	131	the other two are not normally tried.
89	found, AnyEvent will fall back to a pure-perl event loop, which is not
90	very efficient, but should work everywhere.
91		132
92	Because AnyEvent first checks for modules that are already loaded, loading	133	Because AnyEvent first checks for modules that are already loaded, loading
93	an event model explicitly before first using AnyEvent will likely make	134	an event model explicitly before first using AnyEvent will likely make
94	that model the default. For example:	135	that model the default. For example:
95		136
…		…
97	use AnyEvent;	138	use AnyEvent;
98		139
99	# .. AnyEvent will likely default to Tk	140	# .. AnyEvent will likely default to Tk
100		141
101	The I<likely> means that, if any module loads another event model and	142	The I<likely> means that, if any module loads another event model and
102	starts using it, all bets are off. Maybe you should tell their authors to	143	starts using it, all bets are off - this case should be very rare though,
103	use AnyEvent so their modules work together with others seamlessly...	144	as very few modules hardcode event loops without announcing this very
		145	loudly.
104		146
105	The pure-perl implementation of AnyEvent is called	147	The pure-perl implementation of AnyEvent is called C<AnyEvent::Loop>. Like
106	C<AnyEvent::Impl::Perl>. Like other event modules you can load it	148	other event modules you can load it explicitly and enjoy the high
107	explicitly.	149	availability of that event loop :)
108		150
109	=head1 WATCHERS	151	=head1 WATCHERS
110		152
111	AnyEvent has the central concept of a I<watcher>, which is an object that	153	AnyEvent has the central concept of a I<watcher>, which is an object that
112	stores relevant data for each kind of event you are waiting for, such as	154	stores relevant data for each kind of event you are waiting for, such as
113	the callback to call, the filehandle to watch, etc.	155	the callback to call, the file handle to watch, etc.
114		156
115	These watchers are normal Perl objects with normal Perl lifetime. After	157	These watchers are normal Perl objects with normal Perl lifetime. After
116	creating a watcher it will immediately "watch" for events and invoke the	158	creating a watcher it will immediately "watch" for events and invoke the
117	callback when the event occurs (of course, only when the event model	159	callback when the event occurs (of course, only when the event model
118	is in control).	160	is in control).
119		161
		162	Note that B<callbacks must not permanently change global variables>
		163	potentially in use by the event loop (such as C<$_> or C<$[>) and that B<<
		164	callbacks must not C<die> >>. The former is good programming practice in
		165	Perl and the latter stems from the fact that exception handling differs
		166	widely between event loops.
		167
120	To disable the watcher you have to destroy it (e.g. by setting the	168	To disable a watcher you have to destroy it (e.g. by setting the
121	variable you store it in to C<undef> or otherwise deleting all references	169	variable you store it in to C<undef> or otherwise deleting all references
122	to it).	170	to it).
123		171
124	All watchers are created by calling a method on the C<AnyEvent> class.	172	All watchers are created by calling a method on the C<AnyEvent> class.
125		173
126	Many watchers either are used with "recursion" (repeating timers for	174	Many watchers either are used with "recursion" (repeating timers for
127	example), or need to refer to their watcher object in other ways.	175	example), or need to refer to their watcher object in other ways.
128		176
129	An any way to achieve that is this pattern:	177	One way to achieve that is this pattern:
130		178
131	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	179	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
132	# you can use $w here, for example to undef it	180	# you can use $w here, for example to undef it
133	undef $w;	181	undef $w;
134	});	182	});
135		183
136	Note that C<my $w; $w => combination. This is necessary because in Perl,	184	Note that C<my $w; $w => combination. This is necessary because in Perl,
137	my variables are only visible after the statement in which they are	185	my variables are only visible after the statement in which they are
138	declared.	186	declared.
139		187
140	=head2 I/O WATCHERS	188	=head2 I/O WATCHERS
141		189
		190	$w = AnyEvent->io (
		191	fh => <filehandle_or_fileno>,
		192	poll => <"r" or "w">,
		193	cb => <callback>,
		194	);
		195
142	You can create an I/O watcher by calling the C<< AnyEvent->io >> method	196	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
143	with the following mandatory key-value pairs as arguments:	197	with the following mandatory key-value pairs as arguments:
144		198
145	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch	199	C<fh> is the Perl I<file handle> (or a naked file descriptor) to watch
		200	for events (AnyEvent might or might not keep a reference to this file
		201	handle). Note that only file handles pointing to things for which
		202	non-blocking operation makes sense are allowed. This includes sockets,
		203	most character devices, pipes, fifos and so on, but not for example files
		204	or block devices.
		205
146	for events. C<poll> must be a string that is either C<r> or C<w>,	206	C<poll> must be a string that is either C<r> or C<w>, which creates a
147	which creates a watcher waiting for "r"eadable or "w"ritable events,	207	watcher waiting for "r"eadable or "w"ritable events, respectively.
		208
148	respectively. C<cb> is the callback to invoke each time the file handle	209	C<cb> is the callback to invoke each time the file handle becomes ready.
149	becomes ready.
150		210
151	Although the callback might get passed parameters, their value and	211	Although the callback might get passed parameters, their value and
152	presence is undefined and you cannot rely on them. Portable AnyEvent	212	presence is undefined and you cannot rely on them. Portable AnyEvent
153	callbacks cannot use arguments passed to I/O watcher callbacks.	213	callbacks cannot use arguments passed to I/O watcher callbacks.
154		214
155	The I/O watcher might use the underlying file descriptor or a copy of it.	215	The I/O watcher might use the underlying file descriptor or a copy of it.
156	You must not close a file handle as long as any watcher is active on the	216	You must not close a file handle as long as any watcher is active on the
157	underlying file descriptor.	217	underlying file descriptor.
158		218
159	Some event loops issue spurious readyness notifications, so you should	219	Some event loops issue spurious readiness notifications, so you should
160	always use non-blocking calls when reading/writing from/to your file	220	always use non-blocking calls when reading/writing from/to your file
161	handles.	221	handles.
162		222
163	Example:
164
165	# wait for readability of STDIN, then read a line and disable the watcher	223	Example: wait for readability of STDIN, then read a line and disable the
		224	watcher.
		225
166	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	226	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
167	chomp (my $input = <STDIN>);	227	chomp (my $input = <STDIN>);
168	warn "read: $input\n";	228	warn "read: $input\n";
169	undef $w;	229	undef $w;
170	});	230	});
171		231
172	=head2 TIME WATCHERS	232	=head2 TIME WATCHERS
173		233
		234	$w = AnyEvent->timer (after => <seconds>, cb => <callback>);
		235
		236	$w = AnyEvent->timer (
		237	after => <fractional_seconds>,
		238	interval => <fractional_seconds>,
		239	cb => <callback>,
		240	);
		241
174	You can create a time watcher by calling the C<< AnyEvent->timer >>	242	You can create a time watcher by calling the C<< AnyEvent->timer >>
175	method with the following mandatory arguments:	243	method with the following mandatory arguments:
176		244
177	C<after> specifies after how many seconds (fractional values are	245	C<after> specifies after how many seconds (fractional values are
178	supported) the callback should be invoked. C<cb> is the callback to invoke	246	supported) the callback should be invoked. C<cb> is the callback to invoke
…		…
180		248
181	Although the callback might get passed parameters, their value and	249	Although the callback might get passed parameters, their value and
182	presence is undefined and you cannot rely on them. Portable AnyEvent	250	presence is undefined and you cannot rely on them. Portable AnyEvent
183	callbacks cannot use arguments passed to time watcher callbacks.	251	callbacks cannot use arguments passed to time watcher callbacks.
184		252
185	The timer callback will be invoked at most once: if you want a repeating	253	The callback will normally be invoked only once. If you specify another
186	timer you have to create a new watcher (this is a limitation by both Tk	254	parameter, C<interval>, as a strictly positive number (> 0), then the
187	and Glib).	255	callback will be invoked regularly at that interval (in fractional
		256	seconds) after the first invocation. If C<interval> is specified with a
		257	false value, then it is treated as if it were not specified at all.
188		258
189	Example:	259	The callback will be rescheduled before invoking the callback, but no
		260	attempt is made to avoid timer drift in most backends, so the interval is
		261	only approximate.
190		262
191	# fire an event after 7.7 seconds	263	Example: fire an event after 7.7 seconds.
		264
192	my $w = AnyEvent->timer (after => 7.7, cb => sub {	265	my $w = AnyEvent->timer (after => 7.7, cb => sub {
193	warn "timeout\n";	266	warn "timeout\n";
194	});	267	});
195		268
196	# to cancel the timer:	269	# to cancel the timer:
197	undef $w;	270	undef $w;
198		271
199	Example 2:
200
201	# fire an event after 0.5 seconds, then roughly every second	272	Example 2: fire an event after 0.5 seconds, then roughly every second.
202	my $w;
203		273
204	my $cb = sub {
205	# cancel the old timer while creating a new one
206	$w = AnyEvent->timer (after => 1, cb => $cb);	274	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		275	warn "timeout\n";
207	};	276	});
208
209	# start the "loop" by creating the first watcher
210	$w = AnyEvent->timer (after => 0.5, cb => $cb);
211		277
212	=head3 TIMING ISSUES	278	=head3 TIMING ISSUES
213		279
214	There are two ways to handle timers: based on real time (relative, "fire	280	There are two ways to handle timers: based on real time (relative, "fire
215	in 10 seconds") and based on wallclock time (absolute, "fire at 12	281	in 10 seconds") and based on wallclock time (absolute, "fire at 12
…		…
217		283
218	While most event loops expect timers to specified in a relative way, they	284	While most event loops expect timers to specified in a relative way, they
219	use absolute time internally. This makes a difference when your clock	285	use absolute time internally. This makes a difference when your clock
220	"jumps", for example, when ntp decides to set your clock backwards from	286	"jumps", for example, when ntp decides to set your clock backwards from
221	the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to	287	the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to
222	fire "after" a second might actually take six years to finally fire.	288	fire "after a second" might actually take six years to finally fire.
223		289
224	AnyEvent cannot compensate for this. The only event loop that is conscious	290	AnyEvent cannot compensate for this. The only event loop that is conscious
225	about these issues is L<EV>, which offers both relative (ev_timer, based	291	of these issues is L<EV>, which offers both relative (ev_timer, based
226	on true relative time) and absolute (ev_periodic, based on wallclock time)	292	on true relative time) and absolute (ev_periodic, based on wallclock time)
227	timers.	293	timers.
228		294
229	AnyEvent always prefers relative timers, if available, matching the	295	AnyEvent always prefers relative timers, if available, matching the
230	AnyEvent API.	296	AnyEvent API.
231		297
		298	AnyEvent has two additional methods that return the "current time":
		299
		300	=over 4
		301
		302	=item AnyEvent->time
		303
		304	This returns the "current wallclock time" as a fractional number of
		305	seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
		306	return, and the result is guaranteed to be compatible with those).
		307
		308	It progresses independently of any event loop processing, i.e. each call
		309	will check the system clock, which usually gets updated frequently.
		310
		311	=item AnyEvent->now
		312
		313	This also returns the "current wallclock time", but unlike C<time>, above,
		314	this value might change only once per event loop iteration, depending on
		315	the event loop (most return the same time as C<time>, above). This is the
		316	time that AnyEvent's timers get scheduled against.
		317
		318	I<In almost all cases (in all cases if you don't care), this is the
		319	function to call when you want to know the current time.>
		320
		321	This function is also often faster then C<< AnyEvent->time >>, and
		322	thus the preferred method if you want some timestamp (for example,
		323	L<AnyEvent::Handle> uses this to update its activity timeouts).
		324
		325	The rest of this section is only of relevance if you try to be very exact
		326	with your timing; you can skip it without a bad conscience.
		327
		328	For a practical example of when these times differ, consider L<Event::Lib>
		329	and L<EV> and the following set-up:
		330
		331	The event loop is running and has just invoked one of your callbacks at
		332	time=500 (assume no other callbacks delay processing). In your callback,
		333	you wait a second by executing C<sleep 1> (blocking the process for a
		334	second) and then (at time=501) you create a relative timer that fires
		335	after three seconds.
		336
		337	With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
		338	both return C<501>, because that is the current time, and the timer will
		339	be scheduled to fire at time=504 (C<501> + C<3>).
		340
		341	With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
		342	time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
		343	last event processing phase started. With L<EV>, your timer gets scheduled
		344	to run at time=503 (C<500> + C<3>).
		345
		346	In one sense, L<Event::Lib> is more exact, as it uses the current time
		347	regardless of any delays introduced by event processing. However, most
		348	callbacks do not expect large delays in processing, so this causes a
		349	higher drift (and a lot more system calls to get the current time).
		350
		351	In another sense, L<EV> is more exact, as your timer will be scheduled at
		352	the same time, regardless of how long event processing actually took.
		353
		354	In either case, if you care (and in most cases, you don't), then you
		355	can get whatever behaviour you want with any event loop, by taking the
		356	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
		357	account.
		358
		359	=item AnyEvent->now_update
		360
		361	Some event loops (such as L<EV> or L<AnyEvent::Loop>) cache the current
		362	time for each loop iteration (see the discussion of L<< AnyEvent->now >>,
		363	above).
		364
		365	When a callback runs for a long time (or when the process sleeps), then
		366	this "current" time will differ substantially from the real time, which
		367	might affect timers and time-outs.
		368
		369	When this is the case, you can call this method, which will update the
		370	event loop's idea of "current time".
		371
		372	A typical example would be a script in a web server (e.g. C<mod_perl>) -
		373	when mod_perl executes the script, then the event loop will have the wrong
		374	idea about the "current time" (being potentially far in the past, when the
		375	script ran the last time). In that case you should arrange a call to C<<
		376	AnyEvent->now_update >> each time the web server process wakes up again
		377	(e.g. at the start of your script, or in a handler).
		378
		379	Note that updating the time I<might> cause some events to be handled.
		380
		381	=back
		382
232	=head2 SIGNAL WATCHERS	383	=head2 SIGNAL WATCHERS
233		384
		385	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		386
234	You can watch for signals using a signal watcher, C<signal> is the signal	387	You can watch for signals using a signal watcher, C<signal> is the signal
235	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to	388	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
236	be invoked whenever a signal occurs.	389	callback to be invoked whenever a signal occurs.
237		390
238	Although the callback might get passed parameters, their value and	391	Although the callback might get passed parameters, their value and
239	presence is undefined and you cannot rely on them. Portable AnyEvent	392	presence is undefined and you cannot rely on them. Portable AnyEvent
240	callbacks cannot use arguments passed to signal watcher callbacks.	393	callbacks cannot use arguments passed to signal watcher callbacks.
241		394
242	Multiple signal occurances can be clumped together into one callback	395	Multiple signal occurrences can be clumped together into one callback
243	invocation, and callback invocation will be synchronous. synchronous means	396	invocation, and callback invocation will be synchronous. Synchronous means
244	that it might take a while until the signal gets handled by the process,	397	that it might take a while until the signal gets handled by the process,
245	but it is guarenteed not to interrupt any other callbacks.	398	but it is guaranteed not to interrupt any other callbacks.
246		399
247	The main advantage of using these watchers is that you can share a signal	400	The main advantage of using these watchers is that you can share a signal
248	between multiple watchers.	401	between multiple watchers, and AnyEvent will ensure that signals will not
		402	interrupt your program at bad times.
249		403
250	This watcher might use C<%SIG>, so programs overwriting those signals	404	This watcher might use C<%SIG> (depending on the event loop used),
251	directly will likely not work correctly.	405	so programs overwriting those signals directly will likely not work
		406	correctly.
252		407
253	Example: exit on SIGINT	408	Example: exit on SIGINT
254		409
255	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	410	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
256		411
		412	=head3 Restart Behaviour
		413
		414	While restart behaviour is up to the event loop implementation, most will
		415	not restart syscalls (that includes L<Async::Interrupt> and AnyEvent's
		416	pure perl implementation).
		417
		418	=head3 Safe/Unsafe Signals
		419
		420	Perl signals can be either "safe" (synchronous to opcode handling)
		421	or "unsafe" (asynchronous) - the former might delay signal delivery
		422	indefinitely, the latter might corrupt your memory.
		423
		424	AnyEvent signal handlers are, in addition, synchronous to the event loop,
		425	i.e. they will not interrupt your running perl program but will only be
		426	called as part of the normal event handling (just like timer, I/O etc.
		427	callbacks, too).
		428
		429	=head3 Signal Races, Delays and Workarounds
		430
		431	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support
		432	attaching callbacks to signals in a generic way, which is a pity,
		433	as you cannot do race-free signal handling in perl, requiring
		434	C libraries for this. AnyEvent will try to do its best, which
		435	means in some cases, signals will be delayed. The maximum time
		436	a signal might be delayed is 10 seconds by default, but can
		437	be overriden via C<$ENV{PERL_ANYEVENT_MAX_SIGNAL_LATENCY}> or
		438	C<$AnyEvent::MAX_SIGNAL_LATENCY> - see the L<ENVIRONMENT VARIABLES>
		439	section for details.
		440
		441	All these problems can be avoided by installing the optional
		442	L<Async::Interrupt> module, which works with most event loops. It will not
		443	work with inherently broken event loops such as L<Event> or L<Event::Lib>
		444	(and not with L<POE> currently). For those, you just have to suffer the
		445	delays.
		446
257	=head2 CHILD PROCESS WATCHERS	447	=head2 CHILD PROCESS WATCHERS
258		448
		449	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		450
259	You can also watch on a child process exit and catch its exit status.	451	You can also watch for a child process exit and catch its exit status.
260		452
261	The child process is specified by the C<pid> argument (if set to C<0>, it	453	The child process is specified by the C<pid> argument (on some backends,
262	watches for any child process exit). The watcher will trigger as often	454	using C<0> watches for any child process exit, on others this will
263	as status change for the child are received. This works by installing a	455	croak). The watcher will be triggered only when the child process has
264	signal handler for C<SIGCHLD>. The callback will be called with the pid	456	finished and an exit status is available, not on any trace events
265	and exit status (as returned by waitpid), so unlike other watcher types,	457	(stopped/continued).
266	you I<can> rely on child watcher callback arguments.	458
		459	The callback will be called with the pid and exit status (as returned by
		460	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		461	callback arguments.
		462
		463	This watcher type works by installing a signal handler for C<SIGCHLD>,
		464	and since it cannot be shared, nothing else should use SIGCHLD or reap
		465	random child processes (waiting for specific child processes, e.g. inside
		466	C<system>, is just fine).
267		467
268	There is a slight catch to child watchers, however: you usually start them	468	There is a slight catch to child watchers, however: you usually start them
269	I<after> the child process was created, and this means the process could	469	I<after> the child process was created, and this means the process could
270	have exited already (and no SIGCHLD will be sent anymore).	470	have exited already (and no SIGCHLD will be sent anymore).
271		471
272	Not all event models handle this correctly (POE doesn't), but even for	472	Not all event models handle this correctly (neither POE nor IO::Async do,
		473	see their AnyEvent::Impl manpages for details), but even for event models
273	event models that I<do> handle this correctly, they usually need to be	474	that I<do> handle this correctly, they usually need to be loaded before
274	loaded before the process exits (i.e. before you fork in the first place).	475	the process exits (i.e. before you fork in the first place). AnyEvent's
		476	pure perl event loop handles all cases correctly regardless of when you
		477	start the watcher.
275		478
276	This means you cannot create a child watcher as the very first thing in an	479	This means you cannot create a child watcher as the very first
277	AnyEvent program, you I<have> to create at least one watcher before you	480	thing in an AnyEvent program, you I<have> to create at least one
278	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).	481	watcher before you C<fork> the child (alternatively, you can call
		482	C<AnyEvent::detect>).
		483
		484	As most event loops do not support waiting for child events, they will be
		485	emulated by AnyEvent in most cases, in which case the latency and race
		486	problems mentioned in the description of signal watchers apply.
279		487
280	Example: fork a process and wait for it	488	Example: fork a process and wait for it
281		489
282	my $done = AnyEvent->condvar;	490	my $done = AnyEvent->condvar;
283		491
284	my $pid = fork or exit 5;	492	my $pid = fork or exit 5;
285		493
286	my $w = AnyEvent->child (	494	my $w = AnyEvent->child (
287	pid => $pid,	495	pid => $pid,
288	cb => sub {	496	cb => sub {
289	my ($pid, $status) = @_;	497	my ($pid, $status) = @_;
290	warn "pid $pid exited with status $status";	498	warn "pid $pid exited with status $status";
291	$done->send;	499	$done->send;
292	},	500	},
293	);	501	);
294		502
295	# do something else, then wait for process exit	503	# do something else, then wait for process exit
296	$done->recv;	504	$done->recv;
		505
		506	=head2 IDLE WATCHERS
		507
		508	$w = AnyEvent->idle (cb => <callback>);
		509
		510	This will repeatedly invoke the callback after the process becomes idle,
		511	until either the watcher is destroyed or new events have been detected.
		512
		513	Idle watchers are useful when there is a need to do something, but it
		514	is not so important (or wise) to do it instantly. The callback will be
		515	invoked only when there is "nothing better to do", which is usually
		516	defined as "all outstanding events have been handled and no new events
		517	have been detected". That means that idle watchers ideally get invoked
		518	when the event loop has just polled for new events but none have been
		519	detected. Instead of blocking to wait for more events, the idle watchers
		520	will be invoked.
		521
		522	Unfortunately, most event loops do not really support idle watchers (only
		523	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		524	will simply call the callback "from time to time".
		525
		526	Example: read lines from STDIN, but only process them when the
		527	program is otherwise idle:
		528
		529	my @lines; # read data
		530	my $idle_w;
		531	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		532	push @lines, scalar <STDIN>;
		533
		534	# start an idle watcher, if not already done
		535	$idle_w ||= AnyEvent->idle (cb => sub {
		536	# handle only one line, when there are lines left
		537	if (my $line = shift @lines) {
		538	print "handled when idle: $line";
		539	} else {
		540	# otherwise disable the idle watcher again
		541	undef $idle_w;
		542	}
		543	});
		544	});
297		545
298	=head2 CONDITION VARIABLES	546	=head2 CONDITION VARIABLES
		547
		548	$cv = AnyEvent->condvar;
		549
		550	$cv->send (<list>);
		551	my @res = $cv->recv;
299		552
300	If you are familiar with some event loops you will know that all of them	553	If you are familiar with some event loops you will know that all of them
301	require you to run some blocking "loop", "run" or similar function that	554	require you to run some blocking "loop", "run" or similar function that
302	will actively watch for new events and call your callbacks.	555	will actively watch for new events and call your callbacks.
303		556
304	AnyEvent is different, it expects somebody else to run the event loop and	557	AnyEvent is slightly different: it expects somebody else to run the event
305	will only block when necessary (usually when told by the user).	558	loop and will only block when necessary (usually when told by the user).
306		559
307	The instrument to do that is called a "condition variable", so called	560	The tool to do that is called a "condition variable", so called because
308	because they represent a condition that must become true.	561	they represent a condition that must become true.
		562
		563	Now is probably a good time to look at the examples further below.
309		564
310	Condition variables can be created by calling the C<< AnyEvent->condvar	565	Condition variables can be created by calling the C<< AnyEvent->condvar
311	>> method, usually without arguments. The only argument pair allowed is	566	>> method, usually without arguments. The only argument pair allowed is
312	C<cb>, which specifies a callback to be called when the condition variable	567	C<cb>, which specifies a callback to be called when the condition variable
313	becomes true.	568	becomes true, with the condition variable as the first argument (but not
		569	the results).
314		570
315	After creation, the conditon variable is "false" until it becomes "true"	571	After creation, the condition variable is "false" until it becomes "true"
316	by calling the C<send> method.	572	by calling the C<send> method (or calling the condition variable as if it
		573	were a callback, read about the caveats in the description for the C<<
		574	->send >> method).
317		575
318	Condition variables are similar to callbacks, except that you can	576	Since condition variables are the most complex part of the AnyEvent API, here are
319	optionally wait for them. They can also be called merge points - points	577	some different mental models of what they are - pick the ones you can connect to:
320	in time where multiple outstandign events have been processed. And yet	578
321	another way to call them is transations - each condition variable can be	579	=over 4
322	used to represent a transaction, which finishes at some point and delivers	580
323	a result.	581	=item * Condition variables are like callbacks - you can call them (and pass them instead
		582	of callbacks). Unlike callbacks however, you can also wait for them to be called.
		583
		584	=item * Condition variables are signals - one side can emit or send them,
		585	the other side can wait for them, or install a handler that is called when
		586	the signal fires.
		587
		588	=item * Condition variables are like "Merge Points" - points in your program
		589	where you merge multiple independent results/control flows into one.
		590
		591	=item * Condition variables represent a transaction - functions that start
		592	some kind of transaction can return them, leaving the caller the choice
		593	between waiting in a blocking fashion, or setting a callback.
		594
		595	=item * Condition variables represent future values, or promises to deliver
		596	some result, long before the result is available.
		597
		598	=back
324		599
325	Condition variables are very useful to signal that something has finished,	600	Condition variables are very useful to signal that something has finished,
326	for example, if you write a module that does asynchronous http requests,	601	for example, if you write a module that does asynchronous http requests,
327	then a condition variable would be the ideal candidate to signal the	602	then a condition variable would be the ideal candidate to signal the
328	availability of results. The user can either act when the callback is	603	availability of results. The user can either act when the callback is
…		…
332	you can block your main program until an event occurs - for example, you	607	you can block your main program until an event occurs - for example, you
333	could C<< ->recv >> in your main program until the user clicks the Quit	608	could C<< ->recv >> in your main program until the user clicks the Quit
334	button of your app, which would C<< ->send >> the "quit" event.	609	button of your app, which would C<< ->send >> the "quit" event.
335		610
336	Note that condition variables recurse into the event loop - if you have	611	Note that condition variables recurse into the event loop - if you have
337	two pieces of code that call C<< ->recv >> in a round-robbin fashion, you	612	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
338	lose. Therefore, condition variables are good to export to your caller, but	613	lose. Therefore, condition variables are good to export to your caller, but
339	you should avoid making a blocking wait yourself, at least in callbacks,	614	you should avoid making a blocking wait yourself, at least in callbacks,
340	as this asks for trouble.	615	as this asks for trouble.
341		616
342	Condition variables are represented by hash refs in perl, and the keys	617	Condition variables are represented by hash refs in perl, and the keys
343	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing	618	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
344	easy (it is often useful to build your own transaction class on top of	619	easy (it is often useful to build your own transaction class on top of
345	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call	620	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
346	it's C<new> method in your own C<new> method.	621	its C<new> method in your own C<new> method.
347		622
348	There are two "sides" to a condition variable - the "producer side" which	623	There are two "sides" to a condition variable - the "producer side" which
349	eventually calls C<< -> send >>, and the "consumer side", which waits	624	eventually calls C<< -> send >>, and the "consumer side", which waits
350	for the send to occur.	625	for the send to occur.
351		626
352	Example:	627	Example: wait for a timer.
353		628
354	# wait till the result is ready	629	# condition: "wait till the timer is fired"
355	my $result_ready = AnyEvent->condvar;	630	my $timer_fired = AnyEvent->condvar;
356		631
357	# do something such as adding a timer	632	# create the timer - we could wait for, say
358	# or socket watcher the calls $result_ready->send	633	# a handle becomign ready, or even an
359	# when the "result" is ready.	634	# AnyEvent::HTTP request to finish, but
360	# in this case, we simply use a timer:	635	# in this case, we simply use a timer:
361	my $w = AnyEvent->timer (	636	my $w = AnyEvent->timer (
362	after => 1,	637	after => 1,
363	cb => sub { $result_ready->send },	638	cb => sub { $timer_fired->send },
364	);	639	);
365		640
366	# this "blocks" (while handling events) till the callback	641	# this "blocks" (while handling events) till the callback
367	# calls send	642	# calls ->send
368	$result_ready->recv;	643	$timer_fired->recv;
		644
		645	Example: wait for a timer, but take advantage of the fact that condition
		646	variables are also callable directly.
		647
		648	my $done = AnyEvent->condvar;
		649	my $delay = AnyEvent->timer (after => 5, cb => $done);
		650	$done->recv;
		651
		652	Example: Imagine an API that returns a condvar and doesn't support
		653	callbacks. This is how you make a synchronous call, for example from
		654	the main program:
		655
		656	use AnyEvent::CouchDB;
		657
		658	...
		659
		660	my @info = $couchdb->info->recv;
		661
		662	And this is how you would just set a callback to be called whenever the
		663	results are available:
		664
		665	$couchdb->info->cb (sub {
		666	my @info = $_[0]->recv;
		667	});
369		668
370	=head3 METHODS FOR PRODUCERS	669	=head3 METHODS FOR PRODUCERS
371		670
372	These methods should only be used by the producing side, i.e. the	671	These methods should only be used by the producing side, i.e. the
373	code/module that eventually sends the signal. Note that it is also	672	code/module that eventually sends the signal. Note that it is also
…		…
386	immediately from within send.	685	immediately from within send.
387		686
388	Any arguments passed to the C<send> call will be returned by all	687	Any arguments passed to the C<send> call will be returned by all
389	future C<< ->recv >> calls.	688	future C<< ->recv >> calls.
390		689
		690	Condition variables are overloaded so one can call them directly (as if
		691	they were a code reference). Calling them directly is the same as calling
		692	C<send>.
		693
391	=item $cv->croak ($error)	694	=item $cv->croak ($error)
392		695
393	Similar to send, but causes all call's to C<< ->recv >> to invoke	696	Similar to send, but causes all calls to C<< ->recv >> to invoke
394	C<Carp::croak> with the given error message/object/scalar.	697	C<Carp::croak> with the given error message/object/scalar.
395		698
396	This can be used to signal any errors to the condition variable	699	This can be used to signal any errors to the condition variable
397	user/consumer.	700	user/consumer. Doing it this way instead of calling C<croak> directly
		701	delays the error detection, but has the overwhelming advantage that it
		702	diagnoses the error at the place where the result is expected, and not
		703	deep in some event callback with no connection to the actual code causing
		704	the problem.
398		705
399	=item $cv->begin ([group callback])	706	=item $cv->begin ([group callback])
400		707
401	=item $cv->end	708	=item $cv->end
402
403	These two methods are EXPERIMENTAL and MIGHT CHANGE.
404		709
405	These two methods can be used to combine many transactions/events into	710	These two methods can be used to combine many transactions/events into
406	one. For example, a function that pings many hosts in parallel might want	711	one. For example, a function that pings many hosts in parallel might want
407	to use a condition variable for the whole process.	712	to use a condition variable for the whole process.
408		713
409	Every call to C<< ->begin >> will increment a counter, and every call to	714	Every call to C<< ->begin >> will increment a counter, and every call to
410	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end	715	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
411	>>, the (last) callback passed to C<begin> will be executed. That callback	716	>>, the (last) callback passed to C<begin> will be executed, passing the
412	is I<supposed> to call C<< ->send >>, but that is not required. If no	717	condvar as first argument. That callback is I<supposed> to call C<< ->send
413	callback was set, C<send> will be called without any arguments.	718	>>, but that is not required. If no group callback was set, C<send> will
		719	be called without any arguments.
414		720
415	Let's clarify this with the ping example:	721	You can think of C<< $cv->send >> giving you an OR condition (one call
		722	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		723	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		724
		725	Let's start with a simple example: you have two I/O watchers (for example,
		726	STDOUT and STDERR for a program), and you want to wait for both streams to
		727	close before activating a condvar:
416		728
417	my $cv = AnyEvent->condvar;	729	my $cv = AnyEvent->condvar;
418		730
		731	$cv->begin; # first watcher
		732	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		733	defined sysread $fh1, my $buf, 4096
		734	or $cv->end;
		735	});
		736
		737	$cv->begin; # second watcher
		738	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		739	defined sysread $fh2, my $buf, 4096
		740	or $cv->end;
		741	});
		742
		743	$cv->recv;
		744
		745	This works because for every event source (EOF on file handle), there is
		746	one call to C<begin>, so the condvar waits for all calls to C<end> before
		747	sending.
		748
		749	The ping example mentioned above is slightly more complicated, as the
		750	there are results to be passed back, and the number of tasks that are
		751	begun can potentially be zero:
		752
		753	my $cv = AnyEvent->condvar;
		754
419	my %result;	755	my %result;
420	$cv->begin (sub { $cv->send (\%result) });	756	$cv->begin (sub { shift->send (\%result) });
421		757
422	for my $host (@list_of_hosts) {	758	for my $host (@list_of_hosts) {
423	$cv->begin;	759	$cv->begin;
424	ping_host_then_call_callback $host, sub {	760	ping_host_then_call_callback $host, sub {
425	$result{$host} = ...;	761	$result{$host} = ...;
…		…
427	};	763	};
428	}	764	}
429		765
430	$cv->end;	766	$cv->end;
431		767
		768	...
		769
		770	my $results = $cv->recv;
		771
432	This code fragment supposedly pings a number of hosts and calls	772	This code fragment supposedly pings a number of hosts and calls
433	C<send> after results for all then have have been gathered - in any	773	C<send> after results for all then have have been gathered - in any
434	order. To achieve this, the code issues a call to C<begin> when it starts	774	order. To achieve this, the code issues a call to C<begin> when it starts
435	each ping request and calls C<end> when it has received some result for	775	each ping request and calls C<end> when it has received some result for
436	it. Since C<begin> and C<end> only maintain a counter, the order in which	776	it. Since C<begin> and C<end> only maintain a counter, the order in which
…		…
440	loop, which serves two important purposes: first, it sets the callback	780	loop, which serves two important purposes: first, it sets the callback
441	to be called once the counter reaches C<0>, and second, it ensures that	781	to be called once the counter reaches C<0>, and second, it ensures that
442	C<send> is called even when C<no> hosts are being pinged (the loop	782	C<send> is called even when C<no> hosts are being pinged (the loop
443	doesn't execute once).	783	doesn't execute once).
444		784
445	This is the general pattern when you "fan out" into multiple subrequests:	785	This is the general pattern when you "fan out" into multiple (but
446	use an outer C<begin>/C<end> pair to set the callback and ensure C<end>	786	potentially zero) subrequests: use an outer C<begin>/C<end> pair to set
447	is called at least once, and then, for each subrequest you start, call	787	the callback and ensure C<end> is called at least once, and then, for each
448	C<begin> and for eahc subrequest you finish, call C<end>.	788	subrequest you start, call C<begin> and for each subrequest you finish,
		789	call C<end>.
449		790
450	=back	791	=back
451		792
452	=head3 METHODS FOR CONSUMERS	793	=head3 METHODS FOR CONSUMERS
453		794
…		…
457	=over 4	798	=over 4
458		799
459	=item $cv->recv	800	=item $cv->recv
460		801
461	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak	802	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
462	>> methods have been called on c<$cv>, while servicing other watchers	803	>> methods have been called on C<$cv>, while servicing other watchers
463	normally.	804	normally.
464		805
465	You can only wait once on a condition - additional calls are valid but	806	You can only wait once on a condition - additional calls are valid but
466	will return immediately.	807	will return immediately.
467		808
…		…
469	function will call C<croak>.	810	function will call C<croak>.
470		811
471	In list context, all parameters passed to C<send> will be returned,	812	In list context, all parameters passed to C<send> will be returned,
472	in scalar context only the first one will be returned.	813	in scalar context only the first one will be returned.
473		814
		815	Note that doing a blocking wait in a callback is not supported by any
		816	event loop, that is, recursive invocation of a blocking C<< ->recv >> is
		817	not allowed and the C<recv> call will C<croak> if such a condition is
		818	detected. This requirement can be dropped by relying on L<Coro::AnyEvent>
		819	, which allows you to do a blocking C<< ->recv >> from any thread
		820	that doesn't run the event loop itself. L<Coro::AnyEvent> is loaded
		821	automatically when L<Coro> is used with L<AnyEvent>, so code does not need
		822	to do anything special to take advantage of that: any code that would
		823	normally block your program because it calls C<recv>, be executed in an
		824	C<async> thread instead without blocking other threads.
		825
474	Not all event models support a blocking wait - some die in that case	826	Not all event models support a blocking wait - some die in that case
475	(programs might want to do that to stay interactive), so I<if you are	827	(programs might want to do that to stay interactive), so I<if you are
476	using this from a module, never require a blocking wait>, but let the	828	using this from a module, never require a blocking wait>. Instead, let the
477	caller decide whether the call will block or not (for example, by coupling	829	caller decide whether the call will block or not (for example, by coupling
478	condition variables with some kind of request results and supporting	830	condition variables with some kind of request results and supporting
479	callbacks so the caller knows that getting the result will not block,	831	callbacks so the caller knows that getting the result will not block,
480	while still suppporting blocking waits if the caller so desires).	832	while still supporting blocking waits if the caller so desires).
481		833
482	Another reason I<never> to C<< ->recv >> in a module is that you cannot
483	sensibly have two C<< ->recv >>'s in parallel, as that would require
484	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
485	can supply.
486
487	The L<Coro> module, however, I<can> and I<does> supply coroutines and, in
488	fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe
489	versions and also integrates coroutines into AnyEvent, making blocking
490	C<< ->recv >> calls perfectly safe as long as they are done from another
491	coroutine (one that doesn't run the event loop).
492
493	You can ensure that C<< -recv >> never blocks by setting a callback and	834	You can ensure that C<< ->recv >> never blocks by setting a callback and
494	only calling C<< ->recv >> from within that callback (or at a later	835	only calling C<< ->recv >> from within that callback (or at a later
495	time). This will work even when the event loop does not support blocking	836	time). This will work even when the event loop does not support blocking
496	waits otherwise.	837	waits otherwise.
497		838
498	=item $bool = $cv->ready	839	=item $bool = $cv->ready
499		840
500	Returns true when the condition is "true", i.e. whether C<send> or	841	Returns true when the condition is "true", i.e. whether C<send> or
501	C<croak> have been called.	842	C<croak> have been called.
502		843
503	=item $cb = $cv->cb ([new callback])	844	=item $cb = $cv->cb ($cb->($cv))
504		845
505	This is a mutator function that returns the callback set and optionally	846	This is a mutator function that returns the callback set and optionally
506	replaces it before doing so.	847	replaces it before doing so.
507		848
508	The callback will be called when the condition becomes "true", i.e. when	849	The callback will be called when the condition becomes "true", i.e. when
509	C<send> or C<croak> are called. Calling C<recv> inside the callback	850	C<send> or C<croak> are called, with the only argument being the
		851	condition variable itself. If the condition is already true, the
		852	callback is called immediately when it is set. Calling C<recv> inside
510	or at any later time is guaranteed not to block.	853	the callback or at any later time is guaranteed not to block.
511		854
512	=back	855	=back
513		856
		857	=head1 SUPPORTED EVENT LOOPS/BACKENDS
		858
		859	The available backend classes are (every class has its own manpage):
		860
		861	=over 4
		862
		863	=item Backends that are autoprobed when no other event loop can be found.
		864
		865	EV is the preferred backend when no other event loop seems to be in
		866	use. If EV is not installed, then AnyEvent will fall back to its own
		867	pure-perl implementation, which is available everywhere as it comes with
		868	AnyEvent itself.
		869
		870	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		871	AnyEvent::Impl::Perl pure-perl AnyEvent::Loop, fast and portable.
		872
		873	=item Backends that are transparently being picked up when they are used.
		874
		875	These will be used if they are already loaded when the first watcher
		876	is created, in which case it is assumed that the application is using
		877	them. This means that AnyEvent will automatically pick the right backend
		878	when the main program loads an event module before anything starts to
		879	create watchers. Nothing special needs to be done by the main program.
		880
		881	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		882	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		883	AnyEvent::Impl::Tk based on Tk, very broken.
		884	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		885	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		886	AnyEvent::Impl::Irssi used when running within irssi.
		887	AnyEvent::Impl::IOAsync based on IO::Async.
		888	AnyEvent::Impl::Cocoa based on Cocoa::EventLoop.
		889	AnyEvent::Impl::FLTK based on FLTK (fltk 2 binding).
		890
		891	=item Backends with special needs.
		892
		893	Qt requires the Qt::Application to be instantiated first, but will
		894	otherwise be picked up automatically. As long as the main program
		895	instantiates the application before any AnyEvent watchers are created,
		896	everything should just work.
		897
		898	AnyEvent::Impl::Qt based on Qt.
		899
		900	=item Event loops that are indirectly supported via other backends.
		901
		902	Some event loops can be supported via other modules:
		903
		904	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		905
		906	B<WxWidgets> has no support for watching file handles. However, you can
		907	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		908	polls 20 times per second, which was considered to be too horrible to even
		909	consider for AnyEvent.
		910
		911	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		912	backend, so it can be supported through POE.
		913
		914	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		915	load L<POE> when detecting them, in the hope that POE will pick them up,
		916	in which case everything will be automatic.
		917
		918	=back
		919
514	=head1 GLOBAL VARIABLES AND FUNCTIONS	920	=head1 GLOBAL VARIABLES AND FUNCTIONS
515		921
		922	These are not normally required to use AnyEvent, but can be useful to
		923	write AnyEvent extension modules.
		924
516	=over 4	925	=over 4
517		926
518	=item $AnyEvent::MODEL	927	=item $AnyEvent::MODEL
519		928
520	Contains C<undef> until the first watcher is being created. Then it	929	Contains C<undef> until the first watcher is being created, before the
		930	backend has been autodetected.
		931
521	contains the event model that is being used, which is the name of the	932	Afterwards it contains the event model that is being used, which is the
522	Perl class implementing the model. This class is usually one of the	933	name of the Perl class implementing the model. This class is usually one
523	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	934	of the C<AnyEvent::Impl::xxx> modules, but can be any other class in the
524	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	935	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
525		936	will be C<urxvt::anyevent>).
526	The known classes so far are:
527
528	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
529	AnyEvent::Impl::Event based on Event, second best choice.
530	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
531	AnyEvent::Impl::Glib based on Glib, third-best choice.
532	AnyEvent::Impl::Tk based on Tk, very bad choice.
533	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
534	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
535	AnyEvent::Impl::POE based on POE, not generic enough for full support.
536
537	There is no support for WxWidgets, as WxWidgets has no support for
538	watching file handles. However, you can use WxWidgets through the
539	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
540	second, which was considered to be too horrible to even consider for
541	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
542	it's adaptor.
543
544	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
545	autodetecting them.
546		937
547	=item AnyEvent::detect	938	=item AnyEvent::detect
548		939
549	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	940	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
550	if necessary. You should only call this function right before you would	941	if necessary. You should only call this function right before you would
551	have created an AnyEvent watcher anyway, that is, as late as possible at	942	have created an AnyEvent watcher anyway, that is, as late as possible at
552	runtime.	943	runtime, and not e.g. during initialisation of your module.
		944
		945	The effect of calling this function is as if a watcher had been created
		946	(specifically, actions that happen "when the first watcher is created"
		947	happen when calling detetc as well).
		948
		949	If you need to do some initialisation before AnyEvent watchers are
		950	created, use C<post_detect>.
553		951
554	=item $guard = AnyEvent::post_detect { BLOCK }	952	=item $guard = AnyEvent::post_detect { BLOCK }
555		953
556	Arranges for the code block to be executed as soon as the event model is	954	Arranges for the code block to be executed as soon as the event model is
557	autodetected (or immediately if this has already happened).	955	autodetected (or immediately if that has already happened).
		956
		957	The block will be executed I<after> the actual backend has been detected
		958	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		959	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		960	other initialisations - see the sources of L<AnyEvent::Strict> or
		961	L<AnyEvent::AIO> to see how this is used.
		962
		963	The most common usage is to create some global watchers, without forcing
		964	event module detection too early, for example, L<AnyEvent::AIO> creates
		965	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		966	avoid autodetecting the event module at load time.
558		967
559	If called in scalar or list context, then it creates and returns an object	968	If called in scalar or list context, then it creates and returns an object
560	that automatically removes the callback again when it is destroyed. See	969	that automatically removes the callback again when it is destroyed (or
		970	C<undef> when the hook was immediately executed). See L<AnyEvent::AIO> for
561	L<Coro::BDB> for a case where this is useful.	971	a case where this is useful.
		972
		973	Example: Create a watcher for the IO::AIO module and store it in
		974	C<$WATCHER>, but do so only do so after the event loop is initialised.
		975
		976	our WATCHER;
		977
		978	my $guard = AnyEvent::post_detect {
		979	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		980	};
		981
		982	# the ||= is important in case post_detect immediately runs the block,
		983	# as to not clobber the newly-created watcher. assigning both watcher and
		984	# post_detect guard to the same variable has the advantage of users being
		985	# able to just C<undef $WATCHER> if the watcher causes them grief.
		986
		987	$WATCHER ||= $guard;
562		988
563	=item @AnyEvent::post_detect	989	=item @AnyEvent::post_detect
564		990
565	If there are any code references in this array (you can C<push> to it	991	If there are any code references in this array (you can C<push> to it
566	before or after loading AnyEvent), then they will called directly after	992	before or after loading AnyEvent), then they will be called directly
567	the event loop has been chosen.	993	after the event loop has been chosen.
568		994
569	You should check C<$AnyEvent::MODEL> before adding to this array, though:	995	You should check C<$AnyEvent::MODEL> before adding to this array, though:
570	if it contains a true value then the event loop has already been detected,	996	if it is defined then the event loop has already been detected, and the
571	and the array will be ignored.	997	array will be ignored.
572		998
573	Best use C<AnyEvent::post_detect { BLOCK }> instead.	999	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		1000	it, as it takes care of these details.
		1001
		1002	This variable is mainly useful for modules that can do something useful
		1003	when AnyEvent is used and thus want to know when it is initialised, but do
		1004	not need to even load it by default. This array provides the means to hook
		1005	into AnyEvent passively, without loading it.
		1006
		1007	Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used
		1008	together, you could put this into Coro (this is the actual code used by
		1009	Coro to accomplish this):
		1010
		1011	if (defined $AnyEvent::MODEL) {
		1012	# AnyEvent already initialised, so load Coro::AnyEvent
		1013	require Coro::AnyEvent;
		1014	} else {
		1015	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent
		1016	# as soon as it is
		1017	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };
		1018	}
		1019
		1020	=item AnyEvent::postpone { BLOCK }
		1021
		1022	Arranges for the block to be executed as soon as possible, but not before
		1023	the call itself returns. In practise, the block will be executed just
		1024	before the event loop polls for new events, or shortly afterwards.
		1025
		1026	This function never returns anything (to make the C<return postpone { ...
		1027	}> idiom more useful.
		1028
		1029	To understand the usefulness of this function, consider a function that
		1030	asynchronously does something for you and returns some transaction
		1031	object or guard to let you cancel the operation. For example,
		1032	C<AnyEvent::Socket::tcp_connect>:
		1033
		1034	# start a conenction attempt unless one is active
		1035	$self->{connect_guard} ||= AnyEvent::Socket::tcp_connect "www.example.net", 80, sub {
		1036	delete $self->{connect_guard};
		1037	...
		1038	};
		1039
		1040	Imagine that this function could instantly call the callback, for
		1041	example, because it detects an obvious error such as a negative port
		1042	number. Invoking the callback before the function returns causes problems
		1043	however: the callback will be called and will try to delete the guard
		1044	object. But since the function hasn't returned yet, there is nothing to
		1045	delete. When the function eventually returns it will assign the guard
		1046	object to C<< $self->{connect_guard} >>, where it will likely never be
		1047	deleted, so the program thinks it is still trying to connect.
		1048
		1049	This is where C<AnyEvent::postpone> should be used. Instead of calling the
		1050	callback directly on error:
		1051
		1052	$cb->(undef), return # signal error to callback, BAD!
		1053	if $some_error_condition;
		1054
		1055	It should use C<postpone>:
		1056
		1057	AnyEvent::postpone { $cb->(undef) }, return # signal error to callback, later
		1058	if $some_error_condition;
		1059
		1060	=item AnyEvent::log $level, $msg[, @args]
		1061
		1062	Log the given C<$msg> at the given C<$level>.
		1063
		1064	If L<AnyEvent::Log> is not loaded then this function makes a simple test
		1065	to see whether the message will be logged. If the test succeeds it will
		1066	load AnyEvent::Log and call C<AnyEvent::Log::log> - consequently, look at
		1067	the L<AnyEvent::Log> documentation for details.
		1068
		1069	If the test fails it will simply return. Right now this happens when a
		1070	numerical loglevel is used and it is larger than the level specified via
		1071	C<$ENV{PERL_ANYEVENT_VERBOSE}>.
		1072
		1073	If you want to sprinkle loads of logging calls around your code, consider
		1074	creating a logger callback with the C<AnyEvent::Log::logger> function,
		1075	which can reduce typing, codesize and can reduce the logging overhead
		1076	enourmously.
574		1077
575	=back	1078	=back
576		1079
577	=head1 WHAT TO DO IN A MODULE	1080	=head1 WHAT TO DO IN A MODULE
578		1081
…		…
589	because it will stall the whole program, and the whole point of using	1092	because it will stall the whole program, and the whole point of using
590	events is to stay interactive.	1093	events is to stay interactive.
591		1094
592	It is fine, however, to call C<< ->recv >> when the user of your module	1095	It is fine, however, to call C<< ->recv >> when the user of your module
593	requests it (i.e. if you create a http request object ad have a method	1096	requests it (i.e. if you create a http request object ad have a method
594	called C<results> that returns the results, it should call C<< ->recv >>	1097	called C<results> that returns the results, it may call C<< ->recv >>
595	freely, as the user of your module knows what she is doing. always).	1098	freely, as the user of your module knows what she is doing. Always).
596		1099
597	=head1 WHAT TO DO IN THE MAIN PROGRAM	1100	=head1 WHAT TO DO IN THE MAIN PROGRAM
598		1101
599	There will always be a single main program - the only place that should	1102	There will always be a single main program - the only place that should
600	dictate which event model to use.	1103	dictate which event model to use.
601		1104
602	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	1105	If the program is not event-based, it need not do anything special, even
603	do anything special (it does not need to be event-based) and let AnyEvent	1106	when it depends on a module that uses an AnyEvent. If the program itself
604	decide which implementation to chose if some module relies on it.	1107	uses AnyEvent, but does not care which event loop is used, all it needs
		1108	to do is C<use AnyEvent>. In either case, AnyEvent will choose the best
		1109	available loop implementation.
605		1110
606	If the main program relies on a specific event model. For example, in	1111	If the main program relies on a specific event model - for example, in
607	Gtk2 programs you have to rely on the Glib module. You should load the	1112	Gtk2 programs you have to rely on the Glib module - you should load the
608	event module before loading AnyEvent or any module that uses it: generally	1113	event module before loading AnyEvent or any module that uses it: generally
609	speaking, you should load it as early as possible. The reason is that	1114	speaking, you should load it as early as possible. The reason is that
610	modules might create watchers when they are loaded, and AnyEvent will	1115	modules might create watchers when they are loaded, and AnyEvent will
611	decide on the event model to use as soon as it creates watchers, and it	1116	decide on the event model to use as soon as it creates watchers, and it
612	might chose the wrong one unless you load the correct one yourself.	1117	might choose the wrong one unless you load the correct one yourself.
613		1118
614	You can chose to use a rather inefficient pure-perl implementation by	1119	You can chose to use a pure-perl implementation by loading the
615	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	1120	C<AnyEvent::Loop> module, which gives you similar behaviour
616	behaviour everywhere, but letting AnyEvent chose is generally better.	1121	everywhere, but letting AnyEvent chose the model is generally better.
		1122
		1123	=head2 MAINLOOP EMULATION
		1124
		1125	Sometimes (often for short test scripts, or even standalone programs who
		1126	only want to use AnyEvent), you do not want to run a specific event loop.
		1127
		1128	In that case, you can use a condition variable like this:
		1129
		1130	AnyEvent->condvar->recv;
		1131
		1132	This has the effect of entering the event loop and looping forever.
		1133
		1134	Note that usually your program has some exit condition, in which case
		1135	it is better to use the "traditional" approach of storing a condition
		1136	variable somewhere, waiting for it, and sending it when the program should
		1137	exit cleanly.
		1138
617		1139
618	=head1 OTHER MODULES	1140	=head1 OTHER MODULES
619		1141
620	The following is a non-exhaustive list of additional modules that use	1142	The following is a non-exhaustive list of additional modules that use
621	AnyEvent and can therefore be mixed easily with other AnyEvent modules	1143	AnyEvent as a client and can therefore be mixed easily with other
622	in the same program. Some of the modules come with AnyEvent, some are	1144	AnyEvent modules and other event loops in the same program. Some of the
623	available via CPAN.	1145	modules come as part of AnyEvent, the others are available via CPAN (see
		1146	L<http://search.cpan.org/search?m=module&q=anyevent%3A%3A*> for
		1147	a longer non-exhaustive list), and the list is heavily biased towards
		1148	modules of the AnyEvent author himself :)
624		1149
625	=over 4	1150	=over 4
626		1151
627	=item L<AnyEvent::Util>	1152	=item L<AnyEvent::Util> (part of the AnyEvent distribution)
628		1153
629	Contains various utility functions that replace often-used but blocking	1154	Contains various utility functions that replace often-used blocking
630	functions such as C<inet_aton> by event-/callback-based versions.	1155	functions such as C<inet_aton> with event/callback-based versions.
631		1156
632	=item L<AnyEvent::Handle>	1157	=item L<AnyEvent::Socket> (part of the AnyEvent distribution)
633		1158
		1159	Provides various utility functions for (internet protocol) sockets,
		1160	addresses and name resolution. Also functions to create non-blocking tcp
		1161	connections or tcp servers, with IPv6 and SRV record support and more.
		1162
		1163	=item L<AnyEvent::Handle> (part of the AnyEvent distribution)
		1164
634	Provide read and write buffers and manages watchers for reads and writes.	1165	Provide read and write buffers, manages watchers for reads and writes,
		1166	supports raw and formatted I/O, I/O queued and fully transparent and
		1167	non-blocking SSL/TLS (via L<AnyEvent::TLS>).
		1168
		1169	=item L<AnyEvent::DNS> (part of the AnyEvent distribution)
		1170
		1171	Provides rich asynchronous DNS resolver capabilities.
		1172
		1173	=item L<AnyEvent::HTTP>, L<AnyEvent::IRC>, L<AnyEvent::XMPP>, L<AnyEvent::GPSD>, L<AnyEvent::IGS>, L<AnyEvent::FCP>
		1174
		1175	Implement event-based interfaces to the protocols of the same name (for
		1176	the curious, IGS is the International Go Server and FCP is the Freenet
		1177	Client Protocol).
		1178
		1179	=item L<AnyEvent::AIO> (part of the AnyEvent distribution)
		1180
		1181	Truly asynchronous (as opposed to non-blocking) I/O, should be in the
		1182	toolbox of every event programmer. AnyEvent::AIO transparently fuses
		1183	L<IO::AIO> and AnyEvent together, giving AnyEvent access to event-based
		1184	file I/O, and much more.
		1185
		1186	=item L<AnyEvent::Filesys::Notify>
		1187
		1188	AnyEvent is good for non-blocking stuff, but it can't detect file or
		1189	path changes (e.g. "watch this directory for new files", "watch this
		1190	file for changes"). The L<AnyEvent::Filesys::Notify> module promises to
		1191	do just that in a portbale fashion, supporting inotify on GNU/Linux and
		1192	some weird, without doubt broken, stuff on OS X to monitor files. It can
		1193	fall back to blocking scans at regular intervals transparently on other
		1194	platforms, so it's about as portable as it gets.
		1195
		1196	(I haven't used it myself, but I haven't heard anybody complaining about
		1197	it yet).
		1198
		1199	=item L<AnyEvent::DBI>
		1200
		1201	Executes L<DBI> requests asynchronously in a proxy process for you,
		1202	notifying you in an event-based way when the operation is finished.
635		1203
636	=item L<AnyEvent::HTTPD>	1204	=item L<AnyEvent::HTTPD>
637		1205
638	Provides a simple web application server framework.	1206	A simple embedded webserver.
639
640	=item L<AnyEvent::DNS>
641
642	Provides asynchronous DNS resolver capabilities, beyond what
643	L<AnyEvent::Util> offers.
644		1207
645	=item L<AnyEvent::FastPing>	1208	=item L<AnyEvent::FastPing>
646		1209
647	The fastest ping in the west.	1210	The fastest ping in the west.
648		1211
649	=item L<Net::IRC3>
650
651	AnyEvent based IRC client module family.
652
653	=item L<Net::XMPP2>
654
655	AnyEvent based XMPP (Jabber protocol) module family.
656
657	=item L<Net::FCP>
658
659	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
660	of AnyEvent.
661
662	=item L<Event::ExecFlow>
663
664	High level API for event-based execution flow control.
665
666	=item L<Coro>	1212	=item L<Coro>
667		1213
668	Has special support for AnyEvent via L<Coro::AnyEvent>.	1214	Has special support for AnyEvent via L<Coro::AnyEvent>, which allows you
		1215	to simply invert the flow control - don't call us, we will call you:
669		1216
670	=item L<AnyEvent::AIO>, L<IO::AIO>	1217	async {
		1218	Coro::AnyEvent::sleep 5; # creates a 5s timer and waits for it
		1219	print "5 seconds later!\n";
671		1220
672	Truly asynchronous I/O, should be in the toolbox of every event	1221	Coro::AnyEvent::readable *STDIN; # uses an I/O watcher
673	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent	1222	my $line = <STDIN>; # works for ttys
674	together.
675		1223
676	=item L<AnyEvent::BDB>, L<BDB>	1224	AnyEvent::HTTP::http_get "url", Coro::rouse_cb;
677		1225	my ($body, $hdr) = Coro::rouse_wait;
678	Truly asynchronous Berkeley DB access. AnyEvent::AIO transparently fuses	1226	};
679	IO::AIO and AnyEvent together.
680
681	=item L<IO::Lambda>
682
683	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
684		1227
685	=back	1228	=back
686		1229
687	=cut	1230	=cut
688		1231
689	package AnyEvent;	1232	package AnyEvent;
690		1233
691	no warnings;	1234	BEGIN {
692	use strict;	1235	require "AnyEvent/constants.pl";
		1236	&AnyEvent::common_sense;
		1237	}
693		1238
694	use Carp;	1239	use Carp ();
695		1240
696	our $VERSION = '3.41';	1241	our $VERSION = '7.05';
697	our $MODEL;	1242	our $MODEL;
698
699	our $AUTOLOAD;
700	our @ISA;	1243	our @ISA;
701
702	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
703
704	our @REGISTRY;	1244	our @REGISTRY;
		1245	our $VERBOSE;
		1246	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		1247	our $MAX_SIGNAL_LATENCY = $ENV{PERL_ANYEVENT_MAX_SIGNAL_LATENCY} || 10; # executes after the BEGIN block below (tainting!)
705		1248
		1249	BEGIN {
		1250	eval "sub TAINT (){" . (${^TAINT}*1) . "}";
		1251
		1252	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1253	if ${^TAINT};
		1254
		1255	$ENV{"PERL_ANYEVENT_$_"} = $ENV{"AE_$_"}
		1256	for grep s/^AE_// && !exists $ENV{"PERL_ANYEVENT_$_"}, keys %ENV;
		1257
		1258	@ENV{grep /^PERL_ANYEVENT_/, keys %ENV} = ()
		1259	if ${^TAINT};
		1260
		1261	# $ENV{PERL_ANYEVENT_xxx} now valid
		1262
		1263	$VERBOSE = length $ENV{PERL_ANYEVENT_VERBOSE} ? $ENV{PERL_ANYEVENT_VERBOSE}*1 : 4;
		1264
		1265	my $idx;
		1266	$PROTOCOL{$_} = ++$idx
		1267	for reverse split /\s*,\s*/,
		1268	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		1269	}
		1270
		1271	our @post_detect;
		1272
		1273	sub post_detect(&) {
		1274	my ($cb) = @_;
		1275
		1276	push @post_detect, $cb;
		1277
		1278	defined wantarray
		1279	? bless \$cb, "AnyEvent::Util::postdetect"
		1280	: ()
		1281	}
		1282
		1283	sub AnyEvent::Util::postdetect::DESTROY {
		1284	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		1285	}
		1286
		1287	our $POSTPONE_W;
		1288	our @POSTPONE;
		1289
		1290	sub _postpone_exec {
		1291	undef $POSTPONE_W;
		1292
		1293	&{ shift @POSTPONE }
		1294	while @POSTPONE;
		1295	}
		1296
		1297	sub postpone(&) {
		1298	push @POSTPONE, shift;
		1299
		1300	$POSTPONE_W ||= AE::timer (0, 0, \&_postpone_exec);
		1301
		1302	()
		1303	}
		1304
		1305	sub log($$;@) {
		1306	# only load the big bloated module when we actually are about to log something
		1307	if ($_[0] <= ($VERBOSE || 1)) { # also catches non-numeric levels(!) and fatal
		1308	local ($!, $@);
		1309	require AnyEvent::Log; # among other things, sets $VERBOSE to 9
		1310	# AnyEvent::Log overwrites this function
		1311	goto &log;
		1312	}
		1313
		1314	0 # not logged
		1315	}
		1316
		1317	sub _logger($;$) {
		1318	my ($level, $renabled) = @_;
		1319
		1320	$$renabled = $level <= $VERBOSE;
		1321
		1322	my $logger = [(caller)[0], $level, $renabled];
		1323
		1324	$AnyEvent::Log::LOGGER{$logger+0} = $logger;
		1325
		1326	# return unless defined wantarray;
		1327	#
		1328	# require AnyEvent::Util;
		1329	# my $guard = AnyEvent::Util::guard (sub {
		1330	# # "clean up"
		1331	# delete $LOGGER{$logger+0};
		1332	# });
		1333	#
		1334	# sub {
		1335	# return 0 unless $$renabled;
		1336	#
		1337	# $guard if 0; # keep guard alive, but don't cause runtime overhead
		1338	# require AnyEvent::Log unless $AnyEvent::Log::VERSION;
		1339	# package AnyEvent::Log;
		1340	# _log ($logger->[0], $level, @_) # logger->[0] has been converted at load time
		1341	# }
		1342	}
		1343
		1344	if (length $ENV{PERL_ANYEVENT_LOG}) {
		1345	require AnyEvent::Log; # AnyEvent::Log does the thing for us
		1346	}
		1347
706	my @models = (	1348	our @models = (
707	[EV:: => AnyEvent::Impl::EV::],	1349	[EV:: => AnyEvent::Impl::EV::],
		1350	[AnyEvent::Loop:: => AnyEvent::Impl::Perl::],
		1351	# everything below here will not (normally) be autoprobed
		1352	# as the pure perl backend should work everywhere
		1353	# and is usually faster
		1354	[Irssi:: => AnyEvent::Impl::Irssi::], # Irssi has a bogus "Event" package, so msut be near the top
708	[Event:: => AnyEvent::Impl::Event::],	1355	[Event:: => AnyEvent::Impl::Event::], # slow, stable
		1356	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers
		1357	# everything below here should not be autoloaded
		1358	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
709	[Tk:: => AnyEvent::Impl::Tk::],	1359	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		1360	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		1361	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
710	[Wx:: => AnyEvent::Impl::POE::],	1362	[Wx:: => AnyEvent::Impl::POE::],
711	[Prima:: => AnyEvent::Impl::POE::],	1363	[Prima:: => AnyEvent::Impl::POE::],
712	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1364	[IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # a bitch to autodetect
713	# everything below here will not be autoprobed as the pureperl backend should work everywhere	1365	[Cocoa::EventLoop:: => AnyEvent::Impl::Cocoa::],
714	[Glib:: => AnyEvent::Impl::Glib::],	1366	[FLTK:: => AnyEvent::Impl::FLTK::],
715	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
716	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
717	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
718	);	1367	);
719		1368
720	our %method = map +($_ => 1), qw(io timer signal child condvar one_event DESTROY);	1369	our @isa_hook;
721		1370
722	our @post_detect;	1371	sub _isa_set {
		1372	my @pkg = ("AnyEvent", (map $_->[0], grep defined, @isa_hook), $MODEL);
723		1373
		1374	@{"$pkg[$_-1]::ISA"} = $pkg[$_]
		1375	for 1 .. $#pkg;
		1376
		1377	grep $_ && $_->[1], @isa_hook
		1378	and AE::_reset ();
		1379	}
		1380
		1381	# used for hooking AnyEvent::Strict and AnyEvent::Debug::Wrap into the class hierarchy
		1382	sub _isa_hook($$;$) {
		1383	my ($i, $pkg, $reset_ae) = @_;
		1384
		1385	$isa_hook[$i] = $pkg ? [$pkg, $reset_ae] : undef;
		1386
		1387	_isa_set;
		1388	}
		1389
		1390	# all autoloaded methods reserve the complete glob, not just the method slot.
		1391	# due to bugs in perls method cache implementation.
		1392	our @methods = qw(io timer time now now_update signal child idle condvar);
		1393
724	sub post_detect(&) {	1394	sub detect() {
725	my ($cb) = @_;	1395	return $MODEL if $MODEL; # some programs keep references to detect
726		1396
727	if ($MODEL) {	1397	# IO::Async::Loop::AnyEvent is extremely evil, refuse to work with it
728	$cb->();	1398	# the author knows about the problems and what it does to AnyEvent as a whole
		1399	# (and the ability of others to use AnyEvent), but simply wants to abuse AnyEvent
		1400	# anyway.
		1401	AnyEvent::log fatal => "IO::Async::Loop::AnyEvent detected - that module is broken by\n"
		1402	. "design, abuses internals and breaks AnyEvent - will not continue."
		1403	if exists $INC{"IO/Async/Loop/AnyEvent.pm"};
729		1404
730	1	1405	local $!; # for good measure
		1406	local $SIG{__DIE__}; # we use eval
		1407
		1408	# free some memory
		1409	*detect = sub () { $MODEL };
		1410	# undef &func doesn't correctly update the method cache. grmbl.
		1411	# so we delete the whole glob. grmbl.
		1412	# otoh, perl doesn't let me undef an active usb, but it lets me free
		1413	# a glob with an active sub. hrm. i hope it works, but perl is
		1414	# usually buggy in this department. sigh.
		1415	delete @{"AnyEvent::"}{@methods};
		1416	undef @methods;
		1417
		1418	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z0-9:]+)$/) {
		1419	my $model = $1;
		1420	$model = "AnyEvent::Impl::$model" unless $model =~ s/::$//;
		1421	if (eval "require $model") {
		1422	AnyEvent::log 7 => "Loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.";
		1423	$MODEL = $model;
731	} else {	1424	} else {
732	push @post_detect, $cb;	1425	AnyEvent::log 4 => "Unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@";
733		1426	}
734	defined wantarray
735	? bless \$cb, "AnyEvent::Util::Guard"
736	: ()
737	}	1427	}
738	}
739		1428
740	sub AnyEvent::Util::Guard::DESTROY {	1429	# check for already loaded models
741	@post_detect = grep $_ != ${$_[0]}, @post_detect;
742	}
743
744	sub detect() {
745	unless ($MODEL) {	1430	unless ($MODEL) {
746	no strict 'refs';	1431	for (@REGISTRY, @models) {
747		1432	my ($package, $model) = @$_;
748	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	1433	if (${"$package\::VERSION"} > 0) {
749	my $model = "AnyEvent::Impl::$1";
750	if (eval "require $model") {	1434	if (eval "require $model") {
		1435	AnyEvent::log 7 => "Autodetected model '$model', using it.";
751	$MODEL = $model;	1436	$MODEL = $model;
752	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	1437	last;
753	} else {	1438	} else {
754	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;	1439	AnyEvent::log 8 => "Detected event loop $package, but cannot load '$model', skipping: $@";
		1440	}
755	}	1441	}
756	}	1442	}
757		1443
758	# check for already loaded models
759	unless ($MODEL) {	1444	unless ($MODEL) {
		1445	# try to autoload a model
760	for (@REGISTRY, @models) {	1446	for (@REGISTRY, @models) {
761	my ($package, $model) = @$_;	1447	my ($package, $model) = @$_;
		1448	if (
		1449	eval "require $package"
762	if (${"$package\::VERSION"} > 0) {	1450	and ${"$package\::VERSION"} > 0
763	if (eval "require $model") {	1451	and eval "require $model"
		1452	) {
		1453	AnyEvent::log 7 => "Autoloaded model '$model', using it.";
764	$MODEL = $model;	1454	$MODEL = $model;
765	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;
766	last;	1455	last;
767	}
768	}	1456	}
769	}	1457	}
770		1458
771	unless ($MODEL) {	1459	$MODEL
772	# try to load a model	1460	or AnyEvent::log fatal => "Backend autodetection failed - did you properly install AnyEvent?";
		1461	}
		1462	}
773		1463
774	for (@REGISTRY, @models) {	1464	# free memory only needed for probing
775	my ($package, $model) = @$_;	1465	undef @models;
776	if (eval "require $package"	1466	undef @REGISTRY;
777	and ${"$package\::VERSION"} > 0	1467
778	and eval "require $model") {	1468	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
779	$MODEL = $model;	1469
780	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;	1470	# now nuke some methods that are overridden by the backend.
		1471	# SUPER usage is not allowed in these.
		1472	for (qw(time signal child idle)) {
		1473	undef &{"AnyEvent::Base::$_"}
		1474	if defined &{"$MODEL\::$_"};
		1475	}
		1476
		1477	_isa_set;
		1478
		1479	# we're officially open!
		1480
		1481	if ($ENV{PERL_ANYEVENT_STRICT}) {
		1482	require AnyEvent::Strict;
		1483	}
		1484
		1485	if ($ENV{PERL_ANYEVENT_DEBUG_WRAP}) {
		1486	require AnyEvent::Debug;
		1487	AnyEvent::Debug::wrap ($ENV{PERL_ANYEVENT_DEBUG_WRAP});
		1488	}
		1489
		1490	if (length $ENV{PERL_ANYEVENT_DEBUG_SHELL}) {
		1491	require AnyEvent::Socket;
		1492	require AnyEvent::Debug;
		1493
		1494	my $shell = $ENV{PERL_ANYEVENT_DEBUG_SHELL};
		1495	$shell =~ s/\$\$/$$/g;
		1496
		1497	my ($host, $service) = AnyEvent::Socket::parse_hostport ($shell);
		1498	$AnyEvent::Debug::SHELL = AnyEvent::Debug::shell ($host, $service);
		1499	}
		1500
		1501	# now the anyevent environment is set up as the user told us to, so
		1502	# call the actual user code - post detects
		1503
		1504	(shift @post_detect)->() while @post_detect;
		1505	undef @post_detect;
		1506
		1507	*post_detect = sub(&) {
		1508	shift->();
		1509
		1510	undef
		1511	};
		1512
		1513	$MODEL
		1514	}
		1515
		1516	for my $name (@methods) {
		1517	*$name = sub {
		1518	detect;
		1519	# we use goto because
		1520	# a) it makes the thunk more transparent
		1521	# b) it allows us to delete the thunk later
		1522	goto &{ UNIVERSAL::can AnyEvent => "SUPER::$name" }
		1523	};
		1524	}
		1525
		1526	# utility function to dup a filehandle. this is used by many backends
		1527	# to support binding more than one watcher per filehandle (they usually
		1528	# allow only one watcher per fd, so we dup it to get a different one).
		1529	sub _dupfh($$;$$) {
		1530	my ($poll, $fh, $r, $w) = @_;
		1531
		1532	# cygwin requires the fh mode to be matching, unix doesn't
		1533	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1534
		1535	open my $fh2, $mode, $fh
		1536	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1537
		1538	# we assume CLOEXEC is already set by perl in all important cases
		1539
		1540	($fh2, $rw)
		1541	}
		1542
		1543	=head1 SIMPLIFIED AE API
		1544
		1545	Starting with version 5.0, AnyEvent officially supports a second, much
		1546	simpler, API that is designed to reduce the calling, typing and memory
		1547	overhead by using function call syntax and a fixed number of parameters.
		1548
		1549	See the L<AE> manpage for details.
		1550
		1551	=cut
		1552
		1553	package AE;
		1554
		1555	our $VERSION = $AnyEvent::VERSION;
		1556
		1557	sub _reset() {
		1558	eval q{
		1559	# fall back to the main API by default - backends and AnyEvent::Base
		1560	# implementations can overwrite these.
		1561
		1562	sub io($$$) {
		1563	AnyEvent->io (fh => $_[0], poll => $_[1] ? "w" : "r", cb => $_[2])
		1564	}
		1565
		1566	sub timer($$$) {
		1567	AnyEvent->timer (after => $_[0], interval => $_[1], cb => $_[2])
		1568	}
		1569
		1570	sub signal($$) {
		1571	AnyEvent->signal (signal => $_[0], cb => $_[1])
		1572	}
		1573
		1574	sub child($$) {
		1575	AnyEvent->child (pid => $_[0], cb => $_[1])
		1576	}
		1577
		1578	sub idle($) {
		1579	AnyEvent->idle (cb => $_[0]);
		1580	}
		1581
		1582	sub cv(;&) {
		1583	AnyEvent->condvar (@_ ? (cb => $_[0]) : ())
		1584	}
		1585
		1586	sub now() {
		1587	AnyEvent->now
		1588	}
		1589
		1590	sub now_update() {
		1591	AnyEvent->now_update
		1592	}
		1593
		1594	sub time() {
		1595	AnyEvent->time
		1596	}
		1597
		1598	*postpone = \&AnyEvent::postpone;
		1599	*log = \&AnyEvent::log;
		1600	};
		1601	die if $@;
		1602	}
		1603
		1604	BEGIN { _reset }
		1605
		1606	package AnyEvent::Base;
		1607
		1608	# default implementations for many methods
		1609
		1610	sub time {
		1611	eval q{ # poor man's autoloading {}
		1612	# probe for availability of Time::HiRes
		1613	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1614	*time = sub { Time::HiRes::time () };
		1615	*AE::time = \& Time::HiRes::time ;
		1616	*now = \&time;
		1617	AnyEvent::log 8 => "using Time::HiRes for sub-second timing accuracy.";
		1618	# if (eval "use POSIX (); (POSIX::times())...
		1619	} else {
		1620	*time = sub { CORE::time };
		1621	*AE::time = sub (){ CORE::time };
		1622	*now = \&time;
		1623	AnyEvent::log 3 => "Using built-in time(), no sub-second resolution!";
		1624	}
		1625	};
		1626	die if $@;
		1627
		1628	&time
		1629	}
		1630
		1631	*now = \&time;
		1632	sub now_update { }
		1633
		1634	sub _poll {
		1635	Carp::croak "$AnyEvent::MODEL does not support blocking waits. Caught";
		1636	}
		1637
		1638	# default implementation for ->condvar
		1639	# in fact, the default should not be overwritten
		1640
		1641	sub condvar {
		1642	eval q{ # poor man's autoloading {}
		1643	*condvar = sub {
		1644	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
		1645	};
		1646
		1647	*AE::cv = sub (;&) {
		1648	bless { @_ ? (_ae_cb => shift) : () }, "AnyEvent::CondVar"
		1649	};
		1650	};
		1651	die if $@;
		1652
		1653	&condvar
		1654	}
		1655
		1656	# default implementation for ->signal
		1657
		1658	our $HAVE_ASYNC_INTERRUPT;
		1659
		1660	sub _have_async_interrupt() {
		1661	$HAVE_ASYNC_INTERRUPT = 1*(!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT}
		1662	&& eval "use Async::Interrupt 1.02 (); 1")
		1663	unless defined $HAVE_ASYNC_INTERRUPT;
		1664
		1665	$HAVE_ASYNC_INTERRUPT
		1666	}
		1667
		1668	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1669	our (%SIG_ASY, %SIG_ASY_W);
		1670	our ($SIG_COUNT, $SIG_TW);
		1671
		1672	# install a dummy wakeup watcher to reduce signal catching latency
		1673	# used by Impls
		1674	sub _sig_add() {
		1675	unless ($SIG_COUNT++) {
		1676	# try to align timer on a full-second boundary, if possible
		1677	my $NOW = AE::now;
		1678
		1679	$SIG_TW = AE::timer
		1680	$MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1681	$MAX_SIGNAL_LATENCY,
		1682	sub { } # just for the PERL_ASYNC_CHECK
		1683	;
		1684	}
		1685	}
		1686
		1687	sub _sig_del {
		1688	undef $SIG_TW
		1689	unless --$SIG_COUNT;
		1690	}
		1691
		1692	our $_sig_name_init; $_sig_name_init = sub {
		1693	eval q{ # poor man's autoloading {}
		1694	undef $_sig_name_init;
		1695
		1696	if (_have_async_interrupt) {
		1697	*sig2num = \&Async::Interrupt::sig2num;
		1698	*sig2name = \&Async::Interrupt::sig2name;
		1699	} else {
		1700	require Config;
		1701
		1702	my %signame2num;
		1703	@signame2num{ split ' ', $Config::Config{sig_name} }
		1704	= split ' ', $Config::Config{sig_num};
		1705
		1706	my @signum2name;
		1707	@signum2name[values %signame2num] = keys %signame2num;
		1708
		1709	*sig2num = sub($) {
		1710	$_[0] > 0 ? shift : $signame2num{+shift}
		1711	};
		1712	*sig2name = sub ($) {
		1713	$_[0] > 0 ? $signum2name[+shift] : shift
		1714	};
		1715	}
		1716	};
		1717	die if $@;
		1718	};
		1719
		1720	sub sig2num ($) { &$_sig_name_init; &sig2num }
		1721	sub sig2name($) { &$_sig_name_init; &sig2name }
		1722
		1723	sub signal {
		1724	eval q{ # poor man's autoloading {}
		1725	# probe for availability of Async::Interrupt
		1726	if (_have_async_interrupt) {
		1727	AnyEvent::log 8 => "Using Async::Interrupt for race-free signal handling.";
		1728
		1729	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1730	$SIG_IO = AE::io $SIGPIPE_R->fileno, 0, \&_signal_exec;
		1731
		1732	} else {
		1733	AnyEvent::log 8 => "Using emulated perl signal handling with latency timer.";
		1734
		1735	if (AnyEvent::WIN32) {
		1736	require AnyEvent::Util;
		1737
		1738	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1739	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R, 1) if $SIGPIPE_R;
		1740	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W, 1) if $SIGPIPE_W; # just in case
		1741	} else {
		1742	pipe $SIGPIPE_R, $SIGPIPE_W;
		1743	fcntl $SIGPIPE_R, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_R;
		1744	fcntl $SIGPIPE_W, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_W; # just in case
		1745
		1746	# not strictly required, as $^F is normally 2, but let's make sure...
		1747	fcntl $SIGPIPE_R, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1748	fcntl $SIGPIPE_W, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1749	}
		1750
		1751	$SIGPIPE_R
		1752	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1753
		1754	$SIG_IO = AE::io $SIGPIPE_R, 0, \&_signal_exec;
		1755	}
		1756
		1757	*signal = $HAVE_ASYNC_INTERRUPT
		1758	? sub {
		1759	my (undef, %arg) = @_;
		1760
		1761	# async::interrupt
		1762	my $signal = sig2num $arg{signal};
		1763	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1764
		1765	$SIG_ASY{$signal} ||= new Async::Interrupt
		1766	cb => sub { undef $SIG_EV{$signal} },
		1767	signal => $signal,
		1768	pipe => [$SIGPIPE_R->filenos],
		1769	pipe_autodrain => 0,
		1770	;
		1771
		1772	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1773	}
		1774	: sub {
		1775	my (undef, %arg) = @_;
		1776
		1777	# pure perl
		1778	my $signal = sig2name $arg{signal};
		1779	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1780
		1781	$SIG{$signal} ||= sub {
781	last;	1782	local $!;
		1783	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1784	undef $SIG_EV{$signal};
782	}	1785	};
		1786
		1787	# can't do signal processing without introducing races in pure perl,
		1788	# so limit the signal latency.
		1789	_sig_add;
		1790
		1791	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1792	}
		1793	;
		1794
		1795	*AnyEvent::Base::signal::DESTROY = sub {
		1796	my ($signal, $cb) = @{$_[0]};
		1797
		1798	_sig_del;
		1799
		1800	delete $SIG_CB{$signal}{$cb};
		1801
		1802	$HAVE_ASYNC_INTERRUPT
		1803	? delete $SIG_ASY{$signal}
		1804	: # delete doesn't work with older perls - they then
		1805	# print weird messages, or just unconditionally exit
		1806	# instead of getting the default action.
		1807	undef $SIG{$signal}
		1808	unless keys %{ $SIG_CB{$signal} };
		1809	};
		1810
		1811	*_signal_exec = sub {
		1812	$HAVE_ASYNC_INTERRUPT
		1813	? $SIGPIPE_R->drain
		1814	: sysread $SIGPIPE_R, (my $dummy), 9;
		1815
		1816	while (%SIG_EV) {
		1817	for (keys %SIG_EV) {
		1818	delete $SIG_EV{$_};
		1819	&$_ for values %{ $SIG_CB{$_} || {} };
783	}	1820	}
784
785	$MODEL
786	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.";
787	}	1821	}
788	}	1822	};
789
790	unshift @ISA, $MODEL;
791	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
792
793	(shift @post_detect)->() while @post_detect;
794	}
795
796	$MODEL
797	}
798
799	sub AUTOLOAD {
800	(my $func = $AUTOLOAD) =~ s/.*://;
801
802	$method{$func}
803	or croak "$func: not a valid method for AnyEvent objects";
804
805	detect unless $MODEL;
806
807	my $class = shift;
808	$class->$func (@_);
809	}
810
811	package AnyEvent::Base;
812
813	# default implementation for ->condvar
814
815	sub condvar {
816	bless {}, AnyEvent::CondVar::
817	}
818
819	# default implementation for ->signal
820
821	our %SIG_CB;
822
823	sub signal {
824	my (undef, %arg) = @_;
825
826	my $signal = uc $arg{signal}
827	or Carp::croak "required option 'signal' is missing";
828
829	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
830	$SIG{$signal} ||= sub {
831	$_->() for values %{ $SIG_CB{$signal} || {} };
832	};	1823	};
		1824	die if $@;
833		1825
834	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1826	&signal
835	}
836
837	sub AnyEvent::Base::Signal::DESTROY {
838	my ($signal, $cb) = @{$_[0]};
839
840	delete $SIG_CB{$signal}{$cb};
841
842	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };
843	}	1827	}
844		1828
845	# default implementation for ->child	1829	# default implementation for ->child
846		1830
847	our %PID_CB;	1831	our %PID_CB;
848	our $CHLD_W;	1832	our $CHLD_W;
849	our $CHLD_DELAY_W;	1833	our $CHLD_DELAY_W;
850	our $PID_IDLE;
851	our $WNOHANG;
852		1834
853	sub _child_wait {	1835	# used by many Impl's
854	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1836	sub _emit_childstatus($$) {
		1837	my (undef, $rpid, $rstatus) = @_;
		1838
		1839	$_->($rpid, $rstatus)
855	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1840	for values %{ $PID_CB{$rpid} || {} },
856	(values %{ $PID_CB{0} || {} });	1841	values %{ $PID_CB{0} || {} };
857	}
858
859	undef $PID_IDLE;
860	}
861
862	sub _sigchld {
863	# make sure we deliver these changes "synchronous" with the event loop.
864	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {
865	undef $CHLD_DELAY_W;
866	&_child_wait;
867	});
868	}	1842	}
869		1843
870	sub child {	1844	sub child {
		1845	eval q{ # poor man's autoloading {}
		1846	*_sigchld = sub {
		1847	my $pid;
		1848
		1849	AnyEvent->_emit_childstatus ($pid, $?)
		1850	while ($pid = waitpid -1, WNOHANG) > 0;
		1851	};
		1852
		1853	*child = sub {
871	my (undef, %arg) = @_;	1854	my (undef, %arg) = @_;
872		1855
873	defined (my $pid = $arg{pid} + 0)	1856	my $pid = $arg{pid};
874	or Carp::croak "required option 'pid' is missing";	1857	my $cb = $arg{cb};
875		1858
876	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1859	$PID_CB{$pid}{$cb+0} = $cb;
877		1860
878	unless ($WNOHANG) {
879	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;
880	}
881
882	unless ($CHLD_W) {	1861	unless ($CHLD_W) {
883	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1862	$CHLD_W = AE::signal CHLD => \&_sigchld;
884	# child could be a zombie already, so make at least one round	1863	# child could be a zombie already, so make at least one round
885	&_sigchld;	1864	&_sigchld;
886	}	1865	}
887		1866
888	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	1867	bless [$pid, $cb+0], "AnyEvent::Base::child"
889	}	1868	};
890		1869
891	sub AnyEvent::Base::Child::DESTROY {	1870	*AnyEvent::Base::child::DESTROY = sub {
892	my ($pid, $cb) = @{$_[0]};	1871	my ($pid, $icb) = @{$_[0]};
893		1872
894	delete $PID_CB{$pid}{$cb};	1873	delete $PID_CB{$pid}{$icb};
895	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1874	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
896		1875
897	undef $CHLD_W unless keys %PID_CB;	1876	undef $CHLD_W unless keys %PID_CB;
		1877	};
		1878	};
		1879	die if $@;
		1880
		1881	&child
		1882	}
		1883
		1884	# idle emulation is done by simply using a timer, regardless
		1885	# of whether the process is idle or not, and not letting
		1886	# the callback use more than 50% of the time.
		1887	sub idle {
		1888	eval q{ # poor man's autoloading {}
		1889	*idle = sub {
		1890	my (undef, %arg) = @_;
		1891
		1892	my ($cb, $w, $rcb) = $arg{cb};
		1893
		1894	$rcb = sub {
		1895	if ($cb) {
		1896	$w = AE::time;
		1897	&$cb;
		1898	$w = AE::time - $w;
		1899
		1900	# never use more then 50% of the time for the idle watcher,
		1901	# within some limits
		1902	$w = 0.0001 if $w < 0.0001;
		1903	$w = 5 if $w > 5;
		1904
		1905	$w = AE::timer $w, 0, $rcb;
		1906	} else {
		1907	# clean up...
		1908	undef $w;
		1909	undef $rcb;
		1910	}
		1911	};
		1912
		1913	$w = AE::timer 0.05, 0, $rcb;
		1914
		1915	bless \\$cb, "AnyEvent::Base::idle"
		1916	};
		1917
		1918	*AnyEvent::Base::idle::DESTROY = sub {
		1919	undef $${$_[0]};
		1920	};
		1921	};
		1922	die if $@;
		1923
		1924	&idle
898	}	1925	}
899		1926
900	package AnyEvent::CondVar;	1927	package AnyEvent::CondVar;
901		1928
902	our @ISA = AnyEvent::CondVar::Base::;	1929	our @ISA = AnyEvent::CondVar::Base::;
903		1930
		1931	# only to be used for subclassing
		1932	sub new {
		1933	my $class = shift;
		1934	bless AnyEvent->condvar (@_), $class
		1935	}
		1936
904	package AnyEvent::CondVar::Base;	1937	package AnyEvent::CondVar::Base;
		1938
		1939	#use overload
		1940	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1941	# fallback => 1;
		1942
		1943	# save 300+ kilobytes by dirtily hardcoding overloading
		1944	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1945	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1946	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1947	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1948
		1949	our $WAITING;
905		1950
906	sub _send {	1951	sub _send {
907	# nop	1952	# nop
		1953	}
		1954
		1955	sub _wait {
		1956	AnyEvent->_poll until $_[0]{_ae_sent};
908	}	1957	}
909		1958
910	sub send {	1959	sub send {
911	my $cv = shift;	1960	my $cv = shift;
912	$cv->{_ae_sent} = [@_];	1961	$cv->{_ae_sent} = [@_];
…		…
921		1970
922	sub ready {	1971	sub ready {
923	$_[0]{_ae_sent}	1972	$_[0]{_ae_sent}
924	}	1973	}
925		1974
926	sub _wait {
927	AnyEvent->one_event while !$_[0]{_ae_sent};
928	}
929
930	sub recv {	1975	sub recv {
		1976	unless ($_[0]{_ae_sent}) {
		1977	$WAITING
		1978	and Carp::croak "AnyEvent::CondVar: recursive blocking wait attempted";
		1979
		1980	local $WAITING = 1;
931	$_[0]->_wait;	1981	$_[0]->_wait;
		1982	}
932		1983
933	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};	1984	$_[0]{_ae_croak}
934	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]	1985	and Carp::croak $_[0]{_ae_croak};
		1986
		1987	wantarray
		1988	? @{ $_[0]{_ae_sent} }
		1989	: $_[0]{_ae_sent}[0]
935	}	1990	}
936		1991
937	sub cb {	1992	sub cb {
938	$_[0]{_ae_cb} = $_[1] if @_ > 1;	1993	my $cv = shift;
		1994
		1995	@_
		1996	and $cv->{_ae_cb} = shift
		1997	and $cv->{_ae_sent}
		1998	and (delete $cv->{_ae_cb})->($cv);
		1999
939	$_[0]{_ae_cb}	2000	$cv->{_ae_cb}
940	}	2001	}
941		2002
942	sub begin {	2003	sub begin {
943	++$_[0]{_ae_counter};	2004	++$_[0]{_ae_counter};
944	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;	2005	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
945	}	2006	}
946		2007
947	sub end {	2008	sub end {
948	return if --$_[0]{_ae_counter};	2009	return if --$_[0]{_ae_counter};
949	&{ $_[0]{_ae_end_cb} } if $_[0]{_ae_end_cb};	2010	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
950	}	2011	}
951		2012
952	# undocumented/compatibility with pre-3.4	2013	# undocumented/compatibility with pre-3.4
953	*broadcast = \&send;	2014	*broadcast = \&send;
954	*wait = \&_wait;	2015	*wait = \&recv;
		2016
		2017	=head1 ERROR AND EXCEPTION HANDLING
		2018
		2019	In general, AnyEvent does not do any error handling - it relies on the
		2020	caller to do that if required. The L<AnyEvent::Strict> module (see also
		2021	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		2022	checking of all AnyEvent methods, however, which is highly useful during
		2023	development.
		2024
		2025	As for exception handling (i.e. runtime errors and exceptions thrown while
		2026	executing a callback), this is not only highly event-loop specific, but
		2027	also not in any way wrapped by this module, as this is the job of the main
		2028	program.
		2029
		2030	The pure perl event loop simply re-throws the exception (usually
		2031	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		2032	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		2033	so on.
		2034
		2035	=head1 ENVIRONMENT VARIABLES
		2036
		2037	AnyEvent supports a number of environment variables that tune the
		2038	runtime behaviour. They are usually evaluated when AnyEvent is
		2039	loaded, initialised, or a submodule that uses them is loaded. Many of
		2040	them also cause AnyEvent to load additional modules - for example,
		2041	C<PERL_ANYEVENT_DEBUG_WRAP> causes the L<AnyEvent::Debug> module to be
		2042	loaded.
		2043
		2044	All the environment variables documented here start with
		2045	C<PERL_ANYEVENT_>, which is what AnyEvent considers its own
		2046	namespace. Other modules are encouraged (but by no means required) to use
		2047	C<PERL_ANYEVENT_SUBMODULE> if they have registered the AnyEvent::Submodule
		2048	namespace on CPAN, for any submodule. For example, L<AnyEvent::HTTP> could
		2049	be expected to use C<PERL_ANYEVENT_HTTP_PROXY> (it should not access env
		2050	variables starting with C<AE_>, see below).
		2051
		2052	All variables can also be set via the C<AE_> prefix, that is, instead
		2053	of setting C<PERL_ANYEVENT_VERBOSE> you can also set C<AE_VERBOSE>. In
		2054	case there is a clash btween anyevent and another program that uses
		2055	C<AE_something> you can set the corresponding C<PERL_ANYEVENT_something>
		2056	variable to the empty string, as those variables take precedence.
		2057
		2058	When AnyEvent is first loaded, it copies all C<AE_xxx> env variables
		2059	to their C<PERL_ANYEVENT_xxx> counterpart unless that variable already
		2060	exists. If taint mode is on, then AnyEvent will remove I<all> environment
		2061	variables starting with C<PERL_ANYEVENT_> from C<%ENV> (or replace them
		2062	with C<undef> or the empty string, if the corresaponding C<AE_> variable
		2063	is set).
		2064
		2065	The exact algorithm is currently:
		2066
		2067	1. if taint mode enabled, delete all PERL_ANYEVENT_xyz variables from %ENV
		2068	2. copy over AE_xyz to PERL_ANYEVENT_xyz unless the latter alraedy exists
		2069	3. if taint mode enabled, set all PERL_ANYEVENT_xyz variables to undef.
		2070
		2071	This ensures that child processes will not see the C<AE_> variables.
		2072
		2073	The following environment variables are currently known to AnyEvent:
		2074
		2075	=over 4
		2076
		2077	=item C<PERL_ANYEVENT_VERBOSE>
		2078
		2079	By default, AnyEvent will log messages with loglevel C<4> (C<error>) or
		2080	higher (see L<AnyEvent::Log>). You can set this environment variable to a
		2081	numerical loglevel to make AnyEvent more (or less) talkative.
		2082
		2083	If you want to do more than just set the global logging level
		2084	you should have a look at C<PERL_ANYEVENT_LOG>, which allows much more
		2085	complex specifications.
		2086
		2087	When set to C<0> (C<off>), then no messages whatsoever will be logged with
		2088	everything else at defaults.
		2089
		2090	When set to C<5> or higher (C<warn>), AnyEvent warns about unexpected
		2091	conditions, such as not being able to load the event model specified by
		2092	C<PERL_ANYEVENT_MODEL>, or a guard callback throwing an exception - this
		2093	is the minimum recommended level for use during development.
		2094
		2095	When set to C<7> or higher (info), AnyEvent reports which event model it
		2096	chooses.
		2097
		2098	When set to C<8> or higher (debug), then AnyEvent will report extra
		2099	information on which optional modules it loads and how it implements
		2100	certain features.
		2101
		2102	=item C<PERL_ANYEVENT_LOG>
		2103
		2104	Accepts rather complex logging specifications. For example, you could log
		2105	all C<debug> messages of some module to stderr, warnings and above to
		2106	stderr, and errors and above to syslog, with:
		2107
		2108	PERL_ANYEVENT_LOG=Some::Module=debug,+log:filter=warn,+%syslog:%syslog=error,syslog
		2109
		2110	For the rather extensive details, see L<AnyEvent::Log>.
		2111
		2112	This variable is evaluated when AnyEvent (or L<AnyEvent::Log>) is loaded,
		2113	so will take effect even before AnyEvent has initialised itself.
		2114
		2115	Note that specifying this environment variable causes the L<AnyEvent::Log>
		2116	module to be loaded, while C<PERL_ANYEVENT_VERBOSE> does not, so only
		2117	using the latter saves a few hundred kB of memory unless a module
		2118	explicitly needs the extra features of AnyEvent::Log.
		2119
		2120	=item C<PERL_ANYEVENT_STRICT>
		2121
		2122	AnyEvent does not do much argument checking by default, as thorough
		2123	argument checking is very costly. Setting this variable to a true value
		2124	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		2125	check the arguments passed to most method calls. If it finds any problems,
		2126	it will croak.
		2127
		2128	In other words, enables "strict" mode.
		2129
		2130	Unlike C<use strict> (or its modern cousin, C<< use L<common::sense>
		2131	>>, it is definitely recommended to keep it off in production. Keeping
		2132	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		2133	can be very useful, however.
		2134
		2135	=item C<PERL_ANYEVENT_DEBUG_SHELL>
		2136
		2137	If this env variable is nonempty, then its contents will be interpreted by
		2138	C<AnyEvent::Socket::parse_hostport> and C<AnyEvent::Debug::shell> (after
		2139	replacing every occurance of C<$$> by the process pid). The shell object
		2140	is saved in C<$AnyEvent::Debug::SHELL>.
		2141
		2142	This happens when the first watcher is created.
		2143
		2144	For example, to bind a debug shell on a unix domain socket in
		2145	F<< /tmp/debug<pid>.sock >>, you could use this:
		2146
		2147	PERL_ANYEVENT_DEBUG_SHELL=/tmp/debug\$\$.sock perlprog
		2148	# connect with e.g.: socat readline /tmp/debug123.sock
		2149
		2150	Or to bind to tcp port 4545 on localhost:
		2151
		2152	PERL_ANYEVENT_DEBUG_SHELL=127.0.0.1:4545 perlprog
		2153	# connect with e.g.: telnet localhost 4545
		2154
		2155	Note that creating sockets in F</tmp> or on localhost is very unsafe on
		2156	multiuser systems.
		2157
		2158	=item C<PERL_ANYEVENT_DEBUG_WRAP>
		2159
		2160	Can be set to C<0>, C<1> or C<2> and enables wrapping of all watchers for
		2161	debugging purposes. See C<AnyEvent::Debug::wrap> for details.
		2162
		2163	=item C<PERL_ANYEVENT_MODEL>
		2164
		2165	This can be used to specify the event model to be used by AnyEvent, before
		2166	auto detection and -probing kicks in.
		2167
		2168	It normally is a string consisting entirely of ASCII letters (e.g. C<EV>
		2169	or C<IOAsync>). The string C<AnyEvent::Impl::> gets prepended and the
		2170	resulting module name is loaded and - if the load was successful - used as
		2171	event model backend. If it fails to load then AnyEvent will proceed with
		2172	auto detection and -probing.
		2173
		2174	If the string ends with C<::> instead (e.g. C<AnyEvent::Impl::EV::>) then
		2175	nothing gets prepended and the module name is used as-is (hint: C<::> at
		2176	the end of a string designates a module name and quotes it appropriately).
		2177
		2178	For example, to force the pure perl model (L<AnyEvent::Loop::Perl>) you
		2179	could start your program like this:
		2180
		2181	PERL_ANYEVENT_MODEL=Perl perl ...
		2182
		2183	=item C<PERL_ANYEVENT_IO_MODEL>
		2184
		2185	The current file I/O model - see L<AnyEvent::IO> for more info.
		2186
		2187	At the moment, only C<Perl> (small, pure-perl, synchronous) and
		2188	C<IOAIO> (truly asynchronous) are supported. The default is C<IOAIO> if
		2189	L<AnyEvent::AIO> can be loaded, otherwise it is C<Perl>.
		2190
		2191	=item C<PERL_ANYEVENT_PROTOCOLS>
		2192
		2193	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		2194	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		2195	of auto probing).
		2196
		2197	Must be set to a comma-separated list of protocols or address families,
		2198	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		2199	used, and preference will be given to protocols mentioned earlier in the
		2200	list.
		2201
		2202	This variable can effectively be used for denial-of-service attacks
		2203	against local programs (e.g. when setuid), although the impact is likely
		2204	small, as the program has to handle conenction and other failures anyways.
		2205
		2206	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		2207	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		2208	- only support IPv4, never try to resolve or contact IPv6
		2209	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		2210	IPv6, but prefer IPv6 over IPv4.
		2211
		2212	=item C<PERL_ANYEVENT_HOSTS>
		2213
		2214	This variable, if specified, overrides the F</etc/hosts> file used by
		2215	L<AnyEvent::Socket>C<::resolve_sockaddr>, i.e. hosts aliases will be read
		2216	from that file instead.
		2217
		2218	=item C<PERL_ANYEVENT_EDNS0>
		2219
		2220	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension for
		2221	DNS. This extension is generally useful to reduce DNS traffic, especially
		2222	when DNSSEC is involved, but some (broken) firewalls drop such DNS
		2223	packets, which is why it is off by default.
		2224
		2225	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		2226	EDNS0 in its DNS requests.
		2227
		2228	=item C<PERL_ANYEVENT_MAX_FORKS>
		2229
		2230	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		2231	will create in parallel.
		2232
		2233	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		2234
		2235	The default value for the C<max_outstanding> parameter for the default DNS
		2236	resolver - this is the maximum number of parallel DNS requests that are
		2237	sent to the DNS server.
		2238
		2239	=item C<PERL_ANYEVENT_MAX_SIGNAL_LATENCY>
		2240
		2241	Perl has inherently racy signal handling (you can basically choose between
		2242	losing signals and memory corruption) - pure perl event loops (including
		2243	C<AnyEvent::Loop>, when C<Async::Interrupt> isn't available) therefore
		2244	have to poll regularly to avoid losing signals.
		2245
		2246	Some event loops are racy, but don't poll regularly, and some event loops
		2247	are written in C but are still racy. For those event loops, AnyEvent
		2248	installs a timer that regularly wakes up the event loop.
		2249
		2250	By default, the interval for this timer is C<10> seconds, but you can
		2251	override this delay with this environment variable (or by setting
		2252	the C<$AnyEvent::MAX_SIGNAL_LATENCY> variable before creating signal
		2253	watchers).
		2254
		2255	Lower values increase CPU (and energy) usage, higher values can introduce
		2256	long delays when reaping children or waiting for signals.
		2257
		2258	The L<AnyEvent::Async> module, if available, will be used to avoid this
		2259	polling (with most event loops).
		2260
		2261	=item C<PERL_ANYEVENT_RESOLV_CONF>
		2262
		2263	The absolute path to a F<resolv.conf>-style file to use instead of
		2264	F</etc/resolv.conf> (or the OS-specific configuration) in the default
		2265	resolver, or the empty string to select the default configuration.
		2266
		2267	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		2268
		2269	When neither C<ca_file> nor C<ca_path> was specified during
		2270	L<AnyEvent::TLS> context creation, and either of these environment
		2271	variables are nonempty, they will be used to specify CA certificate
		2272	locations instead of a system-dependent default.
		2273
		2274	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		2275
		2276	When these are set to C<1>, then the respective modules are not
		2277	loaded. Mostly good for testing AnyEvent itself.
		2278
		2279	=back
955		2280
956	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	2281	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
957		2282
958	This is an advanced topic that you do not normally need to use AnyEvent in	2283	This is an advanced topic that you do not normally need to use AnyEvent in
959	a module. This section is only of use to event loop authors who want to	2284	a module. This section is only of use to event loop authors who want to
…		…
993		2318
994	I<rxvt-unicode> also cheats a bit by not providing blocking access to	2319	I<rxvt-unicode> also cheats a bit by not providing blocking access to
995	condition variables: code blocking while waiting for a condition will	2320	condition variables: code blocking while waiting for a condition will
996	C<die>. This still works with most modules/usages, and blocking calls must	2321	C<die>. This still works with most modules/usages, and blocking calls must
997	not be done in an interactive application, so it makes sense.	2322	not be done in an interactive application, so it makes sense.
998
999	=head1 ENVIRONMENT VARIABLES
1000
1001	The following environment variables are used by this module:
1002
1003	=over 4
1004
1005	=item C<PERL_ANYEVENT_VERBOSE>
1006
1007	By default, AnyEvent will be completely silent except in fatal
1008	conditions. You can set this environment variable to make AnyEvent more
1009	talkative.
1010
1011	When set to C<1> or higher, causes AnyEvent to warn about unexpected
1012	conditions, such as not being able to load the event model specified by
1013	C<PERL_ANYEVENT_MODEL>.
1014
1015	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
1016	model it chooses.
1017
1018	=item C<PERL_ANYEVENT_MODEL>
1019
1020	This can be used to specify the event model to be used by AnyEvent, before
1021	autodetection and -probing kicks in. It must be a string consisting
1022	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
1023	and the resulting module name is loaded and if the load was successful,
1024	used as event model. If it fails to load AnyEvent will proceed with
1025	autodetection and -probing.
1026
1027	This functionality might change in future versions.
1028
1029	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
1030	could start your program like this:
1031
1032	PERL_ANYEVENT_MODEL=Perl perl ...
1033
1034	=back
1035		2323
1036	=head1 EXAMPLE PROGRAM	2324	=head1 EXAMPLE PROGRAM
1037		2325
1038	The following program uses an I/O watcher to read data from STDIN, a timer	2326	The following program uses an I/O watcher to read data from STDIN, a timer
1039	to display a message once per second, and a condition variable to quit the	2327	to display a message once per second, and a condition variable to quit the
…		…
1048	poll => 'r',	2336	poll => 'r',
1049	cb => sub {	2337	cb => sub {
1050	warn "io event <$_[0]>\n"; # will always output <r>	2338	warn "io event <$_[0]>\n"; # will always output <r>
1051	chomp (my $input = <STDIN>); # read a line	2339	chomp (my $input = <STDIN>); # read a line
1052	warn "read: $input\n"; # output what has been read	2340	warn "read: $input\n"; # output what has been read
1053	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	2341	$cv->send if $input =~ /^q/i; # quit program if /^q/i
1054	},	2342	},
1055	);	2343	);
1056		2344
1057	my $time_watcher; # can only be used once
1058
1059	sub new_timer {
1060	$timer = AnyEvent->timer (after => 1, cb => sub {	2345	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
1061	warn "timeout\n"; # print 'timeout' about every second	2346	warn "timeout\n"; # print 'timeout' at most every second
1062	&new_timer; # and restart the time
1063	});	2347	});
1064	}
1065		2348
1066	new_timer; # create first timer
1067
1068	$cv->wait; # wait until user enters /^q/i	2349	$cv->recv; # wait until user enters /^q/i
1069		2350
1070	=head1 REAL-WORLD EXAMPLE	2351	=head1 REAL-WORLD EXAMPLE
1071		2352
1072	Consider the L<Net::FCP> module. It features (among others) the following	2353	Consider the L<Net::FCP> module. It features (among others) the following
1073	API calls, which are to freenet what HTTP GET requests are to http:	2354	API calls, which are to freenet what HTTP GET requests are to http:
…		…
1123	syswrite $txn->{fh}, $txn->{request}	2404	syswrite $txn->{fh}, $txn->{request}
1124	or die "connection or write error";	2405	or die "connection or write error";
1125	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	2406	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
1126		2407
1127	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	2408	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
1128	result and signals any possible waiters that the request ahs finished:	2409	result and signals any possible waiters that the request has finished:
1129		2410
1130	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	2411	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
1131		2412
1132	if (end-of-file or data complete) {	2413	if (end-of-file or data complete) {
1133	$txn->{result} = $txn->{buf};	2414	$txn->{result} = $txn->{buf};
1134	$txn->{finished}->broadcast;	2415	$txn->{finished}->send;
1135	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	2416	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
1136	}	2417	}
1137		2418
1138	The C<result> method, finally, just waits for the finished signal (if the	2419	The C<result> method, finally, just waits for the finished signal (if the
1139	request was already finished, it doesn't wait, of course, and returns the	2420	request was already finished, it doesn't wait, of course, and returns the
1140	data:	2421	data:
1141		2422
1142	$txn->{finished}->wait;	2423	$txn->{finished}->recv;
1143	return $txn->{result};	2424	return $txn->{result};
1144		2425
1145	The actual code goes further and collects all errors (C<die>s, exceptions)	2426	The actual code goes further and collects all errors (C<die>s, exceptions)
1146	that occured during request processing. The C<result> method detects	2427	that occurred during request processing. The C<result> method detects
1147	whether an exception as thrown (it is stored inside the $txn object)	2428	whether an exception as thrown (it is stored inside the $txn object)
1148	and just throws the exception, which means connection errors and other	2429	and just throws the exception, which means connection errors and other
1149	problems get reported tot he code that tries to use the result, not in a	2430	problems get reported to the code that tries to use the result, not in a
1150	random callback.	2431	random callback.
1151		2432
1152	All of this enables the following usage styles:	2433	All of this enables the following usage styles:
1153		2434
1154	1. Blocking:	2435	1. Blocking:
…		…
1182		2463
1183	my $quit = AnyEvent->condvar;	2464	my $quit = AnyEvent->condvar;
1184		2465
1185	$fcp->txn_client_get ($url)->cb (sub {	2466	$fcp->txn_client_get ($url)->cb (sub {
1186	...	2467	...
1187	$quit->broadcast;	2468	$quit->send;
1188	});	2469	});
1189		2470
1190	$quit->wait;	2471	$quit->recv;
1191		2472
1192		2473
1193	=head1 BENCHMARKS	2474	=head1 BENCHMARKS
1194		2475
1195	To give you an idea of the performance and overheads that AnyEvent adds	2476	To give you an idea of the performance and overheads that AnyEvent adds
…		…
1197	of various event loops I prepared some benchmarks.	2478	of various event loops I prepared some benchmarks.
1198		2479
1199	=head2 BENCHMARKING ANYEVENT OVERHEAD	2480	=head2 BENCHMARKING ANYEVENT OVERHEAD
1200		2481
1201	Here is a benchmark of various supported event models used natively and	2482	Here is a benchmark of various supported event models used natively and
1202	through anyevent. The benchmark creates a lot of timers (with a zero	2483	through AnyEvent. The benchmark creates a lot of timers (with a zero
1203	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,	2484	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
1204	which it is), lets them fire exactly once and destroys them again.	2485	which it is), lets them fire exactly once and destroys them again.
1205		2486
1206	Source code for this benchmark is found as F<eg/bench> in the AnyEvent	2487	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
1207	distribution.	2488	distribution. It uses the L<AE> interface, which makes a real difference
		2489	for the EV and Perl backends only.
1208		2490
1209	=head3 Explanation of the columns	2491	=head3 Explanation of the columns
1210		2492
1211	I<watcher> is the number of event watchers created/destroyed. Since	2493	I<watcher> is the number of event watchers created/destroyed. Since
1212	different event models feature vastly different performances, each event	2494	different event models feature vastly different performances, each event
…		…
1224	all watchers, to avoid adding memory overhead. That means closure creation	2506	all watchers, to avoid adding memory overhead. That means closure creation
1225	and memory usage is not included in the figures.	2507	and memory usage is not included in the figures.
1226		2508
1227	I<invoke> is the time, in microseconds, used to invoke a simple	2509	I<invoke> is the time, in microseconds, used to invoke a simple
1228	callback. The callback simply counts down a Perl variable and after it was	2510	callback. The callback simply counts down a Perl variable and after it was
1229	invoked "watcher" times, it would C<< ->broadcast >> a condvar once to	2511	invoked "watcher" times, it would C<< ->send >> a condvar once to
1230	signal the end of this phase.	2512	signal the end of this phase.
1231		2513
1232	I<destroy> is the time, in microseconds, that it takes to destroy a single	2514	I<destroy> is the time, in microseconds, that it takes to destroy a single
1233	watcher.	2515	watcher.
1234		2516
1235	=head3 Results	2517	=head3 Results
1236		2518
1237	name watchers bytes create invoke destroy comment	2519	name watchers bytes create invoke destroy comment
1238	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	2520	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
1239	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	2521	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
1240	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	2522	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
1241	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	2523	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
1242	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	2524	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
1243	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers	2525	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
		2526	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
		2527	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
1244	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	2528	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
1245	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	2529	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
1246	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	2530	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
1247	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	2531	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
1248		2532
1249	=head3 Discussion	2533	=head3 Discussion
1250		2534
1251	The benchmark does I<not> measure scalability of the event loop very	2535	The benchmark does I<not> measure scalability of the event loop very
1252	well. For example, a select-based event loop (such as the pure perl one)	2536	well. For example, a select-based event loop (such as the pure perl one)
…		…
1264	benchmark machine, handling an event takes roughly 1600 CPU cycles with	2548	benchmark machine, handling an event takes roughly 1600 CPU cycles with
1265	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU	2549	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
1266	cycles with POE.	2550	cycles with POE.
1267		2551
1268	C<EV> is the sole leader regarding speed and memory use, which are both	2552	C<EV> is the sole leader regarding speed and memory use, which are both
1269	maximal/minimal, respectively. Even when going through AnyEvent, it uses	2553	maximal/minimal, respectively. When using the L<AE> API there is zero
		2554	overhead (when going through the AnyEvent API create is about 5-6 times
		2555	slower, with other times being equal, so still uses far less memory than
1270	far less memory than any other event loop and is still faster than Event	2556	any other event loop and is still faster than Event natively).
1271	natively.
1272		2557
1273	The pure perl implementation is hit in a few sweet spots (both the	2558	The pure perl implementation is hit in a few sweet spots (both the
1274	constant timeout and the use of a single fd hit optimisations in the perl	2559	constant timeout and the use of a single fd hit optimisations in the perl
1275	interpreter and the backend itself). Nevertheless this shows that it	2560	interpreter and the backend itself). Nevertheless this shows that it
1276	adds very little overhead in itself. Like any select-based backend its	2561	adds very little overhead in itself. Like any select-based backend its
1277	performance becomes really bad with lots of file descriptors (and few of	2562	performance becomes really bad with lots of file descriptors (and few of
1278	them active), of course, but this was not subject of this benchmark.	2563	them active), of course, but this was not subject of this benchmark.
1279		2564
1280	The C<Event> module has a relatively high setup and callback invocation	2565	The C<Event> module has a relatively high setup and callback invocation
1281	cost, but overall scores in on the third place.	2566	cost, but overall scores in on the third place.
		2567
		2568	C<IO::Async> performs admirably well, about on par with C<Event>, even
		2569	when using its pure perl backend.
1282		2570
1283	C<Glib>'s memory usage is quite a bit higher, but it features a	2571	C<Glib>'s memory usage is quite a bit higher, but it features a
1284	faster callback invocation and overall ends up in the same class as	2572	faster callback invocation and overall ends up in the same class as
1285	C<Event>. However, Glib scales extremely badly, doubling the number of	2573	C<Event>. However, Glib scales extremely badly, doubling the number of
1286	watchers increases the processing time by more than a factor of four,	2574	watchers increases the processing time by more than a factor of four,
…		…
1321	(even when used without AnyEvent), but most event loops have acceptable	2609	(even when used without AnyEvent), but most event loops have acceptable
1322	performance with or without AnyEvent.	2610	performance with or without AnyEvent.
1323		2611
1324	=item * The overhead AnyEvent adds is usually much smaller than the overhead of	2612	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
1325	the actual event loop, only with extremely fast event loops such as EV	2613	the actual event loop, only with extremely fast event loops such as EV
1326	adds AnyEvent significant overhead.	2614	does AnyEvent add significant overhead.
1327		2615
1328	=item * You should avoid POE like the plague if you want performance or	2616	=item * You should avoid POE like the plague if you want performance or
1329	reasonable memory usage.	2617	reasonable memory usage.
1330		2618
1331	=back	2619	=back
1332		2620
1333	=head2 BENCHMARKING THE LARGE SERVER CASE	2621	=head2 BENCHMARKING THE LARGE SERVER CASE
1334		2622
1335	This benchmark atcually benchmarks the event loop itself. It works by	2623	This benchmark actually benchmarks the event loop itself. It works by
1336	creating a number of "servers": each server consists of a socketpair, a	2624	creating a number of "servers": each server consists of a socket pair, a
1337	timeout watcher that gets reset on activity (but never fires), and an I/O	2625	timeout watcher that gets reset on activity (but never fires), and an I/O
1338	watcher waiting for input on one side of the socket. Each time the socket	2626	watcher waiting for input on one side of the socket. Each time the socket
1339	watcher reads a byte it will write that byte to a random other "server".	2627	watcher reads a byte it will write that byte to a random other "server".
1340		2628
1341	The effect is that there will be a lot of I/O watchers, only part of which	2629	The effect is that there will be a lot of I/O watchers, only part of which
1342	are active at any one point (so there is a constant number of active	2630	are active at any one point (so there is a constant number of active
1343	fds for each loop iterstaion, but which fds these are is random). The	2631	fds for each loop iteration, but which fds these are is random). The
1344	timeout is reset each time something is read because that reflects how	2632	timeout is reset each time something is read because that reflects how
1345	most timeouts work (and puts extra pressure on the event loops).	2633	most timeouts work (and puts extra pressure on the event loops).
1346		2634
1347	In this benchmark, we use 10000 socketpairs (20000 sockets), of which 100	2635	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
1348	(1%) are active. This mirrors the activity of large servers with many	2636	(1%) are active. This mirrors the activity of large servers with many
1349	connections, most of which are idle at any one point in time.	2637	connections, most of which are idle at any one point in time.
1350		2638
1351	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent	2639	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
1352	distribution.	2640	distribution. It uses the L<AE> interface, which makes a real difference
		2641	for the EV and Perl backends only.
1353		2642
1354	=head3 Explanation of the columns	2643	=head3 Explanation of the columns
1355		2644
1356	I<sockets> is the number of sockets, and twice the number of "servers" (as	2645	I<sockets> is the number of sockets, and twice the number of "servers" (as
1357	each server has a read and write socket end).	2646	each server has a read and write socket end).
1358		2647
1359	I<create> is the time it takes to create a socketpair (which is	2648	I<create> is the time it takes to create a socket pair (which is
1360	nontrivial) and two watchers: an I/O watcher and a timeout watcher.	2649	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
1361		2650
1362	I<request>, the most important value, is the time it takes to handle a	2651	I<request>, the most important value, is the time it takes to handle a
1363	single "request", that is, reading the token from the pipe and forwarding	2652	single "request", that is, reading the token from the pipe and forwarding
1364	it to another server. This includes deleting the old timeout and creating	2653	it to another server. This includes deleting the old timeout and creating
1365	a new one that moves the timeout into the future.	2654	a new one that moves the timeout into the future.
1366		2655
1367	=head3 Results	2656	=head3 Results
1368		2657
1369	name sockets create request	2658	name sockets create request
1370	EV 20000 69.01 11.16	2659	EV 20000 62.66 7.99
1371	Perl 20000 73.32 35.87	2660	Perl 20000 68.32 32.64
1372	Event 20000 212.62 257.32	2661	IOAsync 20000 174.06 101.15 epoll
1373	Glib 20000 651.16 1896.30	2662	IOAsync 20000 174.67 610.84 poll
		2663	Event 20000 202.69 242.91
		2664	Glib 20000 557.01 1689.52
1374	POE 20000 349.67 12317.24 uses POE::Loop::Event	2665	POE 20000 341.54 12086.32 uses POE::Loop::Event
1375		2666
1376	=head3 Discussion	2667	=head3 Discussion
1377		2668
1378	This benchmark I<does> measure scalability and overall performance of the	2669	This benchmark I<does> measure scalability and overall performance of the
1379	particular event loop.	2670	particular event loop.
…		…
1381	EV is again fastest. Since it is using epoll on my system, the setup time	2672	EV is again fastest. Since it is using epoll on my system, the setup time
1382	is relatively high, though.	2673	is relatively high, though.
1383		2674
1384	Perl surprisingly comes second. It is much faster than the C-based event	2675	Perl surprisingly comes second. It is much faster than the C-based event
1385	loops Event and Glib.	2676	loops Event and Glib.
		2677
		2678	IO::Async performs very well when using its epoll backend, and still quite
		2679	good compared to Glib when using its pure perl backend.
1386		2680
1387	Event suffers from high setup time as well (look at its code and you will	2681	Event suffers from high setup time as well (look at its code and you will
1388	understand why). Callback invocation also has a high overhead compared to	2682	understand why). Callback invocation also has a high overhead compared to
1389	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event	2683	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
1390	uses select or poll in basically all documented configurations.	2684	uses select or poll in basically all documented configurations.
…		…
1437	speed most when you have lots of watchers, not when you only have a few of	2731	speed most when you have lots of watchers, not when you only have a few of
1438	them).	2732	them).
1439		2733
1440	EV is again fastest.	2734	EV is again fastest.
1441		2735
1442	Perl again comes second. It is noticably faster than the C-based event	2736	Perl again comes second. It is noticeably faster than the C-based event
1443	loops Event and Glib, although the difference is too small to really	2737	loops Event and Glib, although the difference is too small to really
1444	matter.	2738	matter.
1445		2739
1446	POE also performs much better in this case, but is is still far behind the	2740	POE also performs much better in this case, but is is still far behind the
1447	others.	2741	others.
…		…
1453	=item * C-based event loops perform very well with small number of	2747	=item * C-based event loops perform very well with small number of
1454	watchers, as the management overhead dominates.	2748	watchers, as the management overhead dominates.
1455		2749
1456	=back	2750	=back
1457		2751
		2752	=head2 THE IO::Lambda BENCHMARK
		2753
		2754	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2755	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2756	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2757	shouldn't come as a surprise to anybody). As such, the benchmark is
		2758	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2759	very optimal. But how would AnyEvent compare when used without the extra
		2760	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2761
		2762	The benchmark itself creates an echo-server, and then, for 500 times,
		2763	connects to the echo server, sends a line, waits for the reply, and then
		2764	creates the next connection. This is a rather bad benchmark, as it doesn't
		2765	test the efficiency of the framework or much non-blocking I/O, but it is a
		2766	benchmark nevertheless.
		2767
		2768	name runtime
		2769	Lambda/select 0.330 sec
		2770	+ optimized 0.122 sec
		2771	Lambda/AnyEvent 0.327 sec
		2772	+ optimized 0.138 sec
		2773	Raw sockets/select 0.077 sec
		2774	POE/select, components 0.662 sec
		2775	POE/select, raw sockets 0.226 sec
		2776	POE/select, optimized 0.404 sec
		2777
		2778	AnyEvent/select/nb 0.085 sec
		2779	AnyEvent/EV/nb 0.068 sec
		2780	+state machine 0.134 sec
		2781
		2782	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2783	benchmarks actually make blocking connects and use 100% blocking I/O,
		2784	defeating the purpose of an event-based solution. All of the newly
		2785	written AnyEvent benchmarks use 100% non-blocking connects (using
		2786	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2787	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2788	generally require a lot more bookkeeping and event handling than blocking
		2789	connects (which involve a single syscall only).
		2790
		2791	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2792	offers similar expressive power as POE and IO::Lambda, using conventional
		2793	Perl syntax. This means that both the echo server and the client are 100%
		2794	non-blocking, further placing it at a disadvantage.
		2795
		2796	As you can see, the AnyEvent + EV combination even beats the
		2797	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2798	backend easily beats IO::Lambda and POE.
		2799
		2800	And even the 100% non-blocking version written using the high-level (and
		2801	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda
		2802	higher level ("unoptimised") abstractions by a large margin, even though
		2803	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
		2804
		2805	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2806	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2807	part of the IO::Lambda distribution and were used without any changes.
		2808
		2809
		2810	=head1 SIGNALS
		2811
		2812	AnyEvent currently installs handlers for these signals:
		2813
		2814	=over 4
		2815
		2816	=item SIGCHLD
		2817
		2818	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2819	emulation for event loops that do not support them natively. Also, some
		2820	event loops install a similar handler.
		2821
		2822	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2823	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2824
		2825	=item SIGPIPE
		2826
		2827	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2828	when AnyEvent gets loaded.
		2829
		2830	The rationale for this is that AnyEvent users usually do not really depend
		2831	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2832	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2833	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2834	some random socket.
		2835
		2836	The rationale for installing a no-op handler as opposed to ignoring it is
		2837	that this way, the handler will be restored to defaults on exec.
		2838
		2839	Feel free to install your own handler, or reset it to defaults.
		2840
		2841	=back
		2842
		2843	=cut
		2844
		2845	undef $SIG{CHLD}
		2846	if $SIG{CHLD} eq 'IGNORE';
		2847
		2848	$SIG{PIPE} = sub { }
		2849	unless defined $SIG{PIPE};
		2850
		2851	=head1 RECOMMENDED/OPTIONAL MODULES
		2852
		2853	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2854	its built-in modules) are required to use it.
		2855
		2856	That does not mean that AnyEvent won't take advantage of some additional
		2857	modules if they are installed.
		2858
		2859	This section explains which additional modules will be used, and how they
		2860	affect AnyEvent's operation.
		2861
		2862	=over 4
		2863
		2864	=item L<Async::Interrupt>
		2865
		2866	This slightly arcane module is used to implement fast signal handling: To
		2867	my knowledge, there is no way to do completely race-free and quick
		2868	signal handling in pure perl. To ensure that signals still get
		2869	delivered, AnyEvent will start an interval timer to wake up perl (and
		2870	catch the signals) with some delay (default is 10 seconds, look for
		2871	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2872
		2873	If this module is available, then it will be used to implement signal
		2874	catching, which means that signals will not be delayed, and the event loop
		2875	will not be interrupted regularly, which is more efficient (and good for
		2876	battery life on laptops).
		2877
		2878	This affects not just the pure-perl event loop, but also other event loops
		2879	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2880
		2881	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2882	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2883	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2884	does nothing for those backends.
		2885
		2886	=item L<EV>
		2887
		2888	This module isn't really "optional", as it is simply one of the backend
		2889	event loops that AnyEvent can use. However, it is simply the best event
		2890	loop available in terms of features, speed and stability: It supports
		2891	the AnyEvent API optimally, implements all the watcher types in XS, does
		2892	automatic timer adjustments even when no monotonic clock is available,
		2893	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2894	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2895	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2896
		2897	If you only use backends that rely on another event loop (e.g. C<Tk>),
		2898	then this module will do nothing for you.
		2899
		2900	=item L<Guard>
		2901
		2902	The guard module, when used, will be used to implement
		2903	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2904	lot less memory), but otherwise doesn't affect guard operation much. It is
		2905	purely used for performance.
		2906
		2907	=item L<JSON> and L<JSON::XS>
		2908
		2909	One of these modules is required when you want to read or write JSON data
		2910	via L<AnyEvent::Handle>. L<JSON> is also written in pure-perl, but can take
		2911	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2912
		2913	=item L<Net::SSLeay>
		2914
		2915	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2916	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2917	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2918
		2919	=item L<Time::HiRes>
		2920
		2921	This module is part of perl since release 5.008. It will be used when the
		2922	chosen event library does not come with a timing source of its own. The
		2923	pure-perl event loop (L<AnyEvent::Loop>) will additionally load it to
		2924	try to use a monotonic clock for timing stability.
		2925
		2926	=item L<AnyEvent::AIO> (and L<IO::AIO>)
		2927
		2928	The default implementation of L<AnyEvent::IO> is to do I/O synchronously,
		2929	stopping programs while they access the disk, which is fine for a lot of
		2930	programs.
		2931
		2932	Installing AnyEvent::AIO (and its IO::AIO dependency) makes it switch to
		2933	a true asynchronous implementation, so event processing can continue even
		2934	while waiting for disk I/O.
		2935
		2936	=back
		2937
1458		2938
1459	=head1 FORK	2939	=head1 FORK
1460		2940
1461	Most event libraries are not fork-safe. The ones who are usually are	2941	Most event libraries are not fork-safe. The ones who are usually are
1462	because they rely on inefficient but fork-safe C<select> or C<poll>	2942	because they rely on inefficient but fork-safe C<select> or C<poll> calls
1463	calls. Only L<EV> is fully fork-aware.	2943	- higher performance APIs such as BSD's kqueue or the dreaded Linux epoll
		2944	are usually badly thought-out hacks that are incompatible with fork in
		2945	one way or another. Only L<EV> is fully fork-aware and ensures that you
		2946	continue event-processing in both parent and child (or both, if you know
		2947	what you are doing).
		2948
		2949	This means that, in general, you cannot fork and do event processing in
		2950	the child if the event library was initialised before the fork (which
		2951	usually happens when the first AnyEvent watcher is created, or the library
		2952	is loaded).
1464		2953
1465	If you have to fork, you must either do so I<before> creating your first	2954	If you have to fork, you must either do so I<before> creating your first
1466	watcher OR you must not use AnyEvent at all in the child.	2955	watcher OR you must not use AnyEvent at all in the child OR you must do
		2956	something completely out of the scope of AnyEvent.
		2957
		2958	The problem of doing event processing in the parent I<and> the child
		2959	is much more complicated: even for backends that I<are> fork-aware or
		2960	fork-safe, their behaviour is not usually what you want: fork clones all
		2961	watchers, that means all timers, I/O watchers etc. are active in both
		2962	parent and child, which is almost never what you want. USing C<exec>
		2963	to start worker children from some kind of manage rprocess is usually
		2964	preferred, because it is much easier and cleaner, at the expense of having
		2965	to have another binary.
1467		2966
1468		2967
1469	=head1 SECURITY CONSIDERATIONS	2968	=head1 SECURITY CONSIDERATIONS
1470		2969
1471	AnyEvent can be forced to load any event model via	2970	AnyEvent can be forced to load any event model via
…		…
1476	specified in the variable.	2975	specified in the variable.
1477		2976
1478	You can make AnyEvent completely ignore this variable by deleting it	2977	You can make AnyEvent completely ignore this variable by deleting it
1479	before the first watcher gets created, e.g. with a C<BEGIN> block:	2978	before the first watcher gets created, e.g. with a C<BEGIN> block:
1480		2979
1481	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	2980	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1482		2981
1483	use AnyEvent;	2982	use AnyEvent;
1484		2983
1485	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can	2984	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1486	be used to probe what backend is used and gain other information (which is	2985	be used to probe what backend is used and gain other information (which is
1487	probably even less useful to an attacker than PERL_ANYEVENT_MODEL).	2986	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2987	$ENV{PERL_ANYEVENT_STRICT}.
		2988
		2989	Note that AnyEvent will remove I<all> environment variables starting with
		2990	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2991	enabled.
		2992
		2993
		2994	=head1 BUGS
		2995
		2996	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2997	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2998	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2999	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		3000	pronounced).
1488		3001
1489		3002
1490	=head1 SEE ALSO	3003	=head1 SEE ALSO
1491		3004
1492	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,	3005	Tutorial/Introduction: L<AnyEvent::Intro>.
1493	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.	3006
		3007	FAQ: L<AnyEvent::FAQ>.
		3008
		3009	Utility functions: L<AnyEvent::Util> (misc. grab-bag), L<AnyEvent::Log>
		3010	(simply logging).
		3011
		3012	Development/Debugging: L<AnyEvent::Strict> (stricter checking),
		3013	L<AnyEvent::Debug> (interactive shell, watcher tracing).
		3014
		3015	Supported event modules: L<AnyEvent::Loop>, L<EV>, L<EV::Glib>,
		3016	L<Glib::EV>, L<Event>, L<Glib::Event>, L<Glib>, L<Tk>, L<Event::Lib>,
		3017	L<Qt>, L<POE>, L<FLTK>.
1494		3018
1495	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,	3019	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
1496	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,	3020	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
1497	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,	3021	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
		3022	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>, L<Anyevent::Impl::Irssi>,
1498	L<AnyEvent::Impl::POE>.	3023	L<AnyEvent::Impl::FLTK>.
1499		3024
		3025	Non-blocking handles, pipes, stream sockets, TCP clients and
		3026	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
		3027
		3028	Asynchronous File I/O: L<AnyEvent::IO>.
		3029
		3030	Asynchronous DNS: L<AnyEvent::DNS>.
		3031
1500	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,	3032	Thread support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
1501		3033
1502	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	3034	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::IRC>,
		3035	L<AnyEvent::HTTP>.
1503		3036
1504		3037
1505	=head1 AUTHOR	3038	=head1 AUTHOR
1506		3039
1507	Marc Lehmann <schmorp@schmorp.de>	3040	Marc Lehmann <schmorp@schmorp.de>
1508	http://home.schmorp.de/	3041	http://anyevent.schmorp.de
1509		3042
1510	=cut	3043	=cut
1511		3044
1512	1	3045	1
1513		3046

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