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Revision 1.95 by root, Sat Apr 26 11:06:45 2008 UTC vs.
Revision 1.376 by root, Thu Aug 25 06:34:11 2011 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent - provide framework for multiple event loops	3	AnyEvent - the DBI of event loop programming
4		4
5	EV, Event, Coro::EV, Coro::Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event loops	5	EV, Event, Glib, Tk, Perl, Event::Lib, Irssi, rxvt-unicode, IO::Async, Qt,
		6	FLTK and POE are various supported event loops/environments.
6		7
7	=head1 SYNOPSIS	8	=head1 SYNOPSIS
8		9
9	use AnyEvent;	10	use AnyEvent;
10		11
		12	# if you prefer function calls, look at the AE manpage for
		13	# an alternative API.
		14
		15	# file handle or descriptor readable
11	my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub {	16	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
		17
		18	# one-shot or repeating timers
		19	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
		20	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...);
		21
		22	print AnyEvent->now; # prints current event loop time
		23	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
		24
		25	# POSIX signal
		26	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
		27
		28	# child process exit
		29	my $w = AnyEvent->child (pid => $pid, cb => sub {
		30	my ($pid, $status) = @_;
12	...	31	...
13	});	32	});
14		33
15	my $w = AnyEvent->timer (after => $seconds, cb => sub {	34	# called when event loop idle (if applicable)
16	...	35	my $w = AnyEvent->idle (cb => sub { ... });
17	});
18		36
19	my $w = AnyEvent->condvar; # stores whether a condition was flagged	37	my $w = AnyEvent->condvar; # stores whether a condition was flagged
		38	$w->send; # wake up current and all future recv's
20	$w->wait; # enters "main loop" till $condvar gets ->broadcast	39	$w->recv; # enters "main loop" till $condvar gets ->send
21	$w->broadcast; # wake up current and all future wait's	40	# use a condvar in callback mode:
		41	$w->cb (sub { $_[0]->recv });
		42
		43	=head1 INTRODUCTION/TUTORIAL
		44
		45	This manpage is mainly a reference manual. If you are interested
		46	in a tutorial or some gentle introduction, have a look at the
		47	L<AnyEvent::Intro> manpage.
		48
		49	=head1 SUPPORT
		50
		51	An FAQ document is available as L<AnyEvent::FAQ>.
		52
		53	There also is a mailinglist for discussing all things AnyEvent, and an IRC
		54	channel, too.
		55
		56	See the AnyEvent project page at the B<Schmorpforge Ta-Sa Software
		57	Repository>, at L<http://anyevent.schmorp.de>, for more info.
22		58
23	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)	59	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
24		60
25	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	61	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
26	nowadays. So what is different about AnyEvent?	62	nowadays. So what is different about AnyEvent?
27		63
28	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of	64	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
29	policy> and AnyEvent is I<small and efficient>.	65	policy> and AnyEvent is I<small and efficient>.
30		66
31	First and foremost, I<AnyEvent is not an event model> itself, it only	67	First and foremost, I<AnyEvent is not an event model> itself, it only
32	interfaces to whatever event model the main program happens to use in a	68	interfaces to whatever event model the main program happens to use, in a
33	pragmatic way. For event models and certain classes of immortals alike,	69	pragmatic way. For event models and certain classes of immortals alike,
34	the statement "there can only be one" is a bitter reality: In general,	70	the statement "there can only be one" is a bitter reality: In general,
35	only one event loop can be active at the same time in a process. AnyEvent	71	only one event loop can be active at the same time in a process. AnyEvent
36	helps hiding the differences between those event loops.	72	cannot change this, but it can hide the differences between those event
		73	loops.
37		74
38	The goal of AnyEvent is to offer module authors the ability to do event	75	The goal of AnyEvent is to offer module authors the ability to do event
39	programming (waiting for I/O or timer events) without subscribing to a	76	programming (waiting for I/O or timer events) without subscribing to a
40	religion, a way of living, and most importantly: without forcing your	77	religion, a way of living, and most importantly: without forcing your
41	module users into the same thing by forcing them to use the same event	78	module users into the same thing by forcing them to use the same event
42	model you use.	79	model you use.
43		80
44	For modules like POE or IO::Async (which is a total misnomer as it is	81	For modules like POE or IO::Async (which is a total misnomer as it is
45	actually doing all I/O I<synchronously>...), using them in your module is	82	actually doing all I/O I<synchronously>...), using them in your module is
46	like joining a cult: After you joined, you are dependent on them and you	83	like joining a cult: After you join, you are dependent on them and you
47	cannot use anything else, as it is simply incompatible to everything that	84	cannot use anything else, as they are simply incompatible to everything
48	isn't itself. What's worse, all the potential users of your module are	85	that isn't them. What's worse, all the potential users of your
49	I<also> forced to use the same event loop you use.	86	module are I<also> forced to use the same event loop you use.
50		87
51	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	88	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
52	fine. AnyEvent + Tk works fine etc. etc. but none of these work together	89	fine. AnyEvent + Tk works fine etc. etc. but none of these work together
53	with the rest: POE + IO::Async? no go. Tk + Event? no go. Again: if	90	with the rest: POE + EV? No go. Tk + Event? No go. Again: if your module
54	your module uses one of those, every user of your module has to use it,	91	uses one of those, every user of your module has to use it, too. But if
55	too. But if your module uses AnyEvent, it works transparently with all	92	your module uses AnyEvent, it works transparently with all event models it
56	event models it supports (including stuff like POE and IO::Async, as long	93	supports (including stuff like IO::Async, as long as those use one of the
57	as those use one of the supported event loops. It is trivial to add new	94	supported event loops. It is easy to add new event loops to AnyEvent, too,
58	event loops to AnyEvent, too, so it is future-proof).	95	so it is future-proof).
59		96
60	In addition to being free of having to use I<the one and only true event	97	In addition to being free of having to use I<the one and only true event
61	model>, AnyEvent also is free of bloat and policy: with POE or similar	98	model>, AnyEvent also is free of bloat and policy: with POE or similar
62	modules, you get an enourmous amount of code and strict rules you have to	99	modules, you get an enormous amount of code and strict rules you have to
63	follow. AnyEvent, on the other hand, is lean and up to the point, by only	100	follow. AnyEvent, on the other hand, is lean and to the point, by only
64	offering the functionality that is necessary, in as thin as a wrapper as	101	offering the functionality that is necessary, in as thin as a wrapper as
65	technically possible.	102	technically possible.
66		103
		104	Of course, AnyEvent comes with a big (and fully optional!) toolbox
		105	of useful functionality, such as an asynchronous DNS resolver, 100%
		106	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
		107	such as Windows) and lots of real-world knowledge and workarounds for
		108	platform bugs and differences.
		109
67	Of course, if you want lots of policy (this can arguably be somewhat	110	Now, if you I<do want> lots of policy (this can arguably be somewhat
68	useful) and you want to force your users to use the one and only event	111	useful) and you want to force your users to use the one and only event
69	model, you should I<not> use this module.	112	model, you should I<not> use this module.
70		113
71
72	=head1 DESCRIPTION	114	=head1 DESCRIPTION
73		115
74	L<AnyEvent> provides an identical interface to multiple event loops. This	116	L<AnyEvent> provides a uniform interface to various event loops. This
75	allows module authors to utilise an event loop without forcing module	117	allows module authors to use event loop functionality without forcing
76	users to use the same event loop (as only a single event loop can coexist	118	module users to use a specific event loop implementation (since more
77	peacefully at any one time).	119	than one event loop cannot coexist peacefully).
78		120
79	The interface itself is vaguely similar, but not identical to the L<Event>	121	The interface itself is vaguely similar, but not identical to the L<Event>
80	module.	122	module.
81		123
82	During the first call of any watcher-creation method, the module tries	124	During the first call of any watcher-creation method, the module tries
83	to detect the currently loaded event loop by probing whether one of the	125	to detect the currently loaded event loop by probing whether one of the
84	following modules is already loaded: L<Coro::EV>, L<Coro::Event>, L<EV>,	126	following modules is already loaded: L<EV>, L<AnyEvent::Loop>,
85	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,	127	L<Event>, L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>. The first one
86	L<POE>. The first one found is used. If none are found, the module tries	128	found is used. If none are detected, the module tries to load the first
87	to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl	129	four modules in the order given; but note that if L<EV> is not
88	adaptor should always succeed) in the order given. The first one that can	130	available, the pure-perl L<AnyEvent::Loop> should always work, so
89	be successfully loaded will be used. If, after this, still none could be	131	the other two are not normally tried.
90	found, AnyEvent will fall back to a pure-perl event loop, which is not
91	very efficient, but should work everywhere.
92		132
93	Because AnyEvent first checks for modules that are already loaded, loading	133	Because AnyEvent first checks for modules that are already loaded, loading
94	an event model explicitly before first using AnyEvent will likely make	134	an event model explicitly before first using AnyEvent will likely make
95	that model the default. For example:	135	that model the default. For example:
96		136
…		…
98	use AnyEvent;	138	use AnyEvent;
99		139
100	# .. AnyEvent will likely default to Tk	140	# .. AnyEvent will likely default to Tk
101		141
102	The I<likely> means that, if any module loads another event model and	142	The I<likely> means that, if any module loads another event model and
103	starts using it, all bets are off. Maybe you should tell their authors to	143	starts using it, all bets are off - this case should be very rare though,
104	use AnyEvent so their modules work together with others seamlessly...	144	as very few modules hardcode event loops without announcing this very
		145	loudly.
105		146
106	The pure-perl implementation of AnyEvent is called	147	The pure-perl implementation of AnyEvent is called C<AnyEvent::Loop>. Like
107	C<AnyEvent::Impl::Perl>. Like other event modules you can load it	148	other event modules you can load it explicitly and enjoy the high
108	explicitly.	149	availability of that event loop :)
109		150
110	=head1 WATCHERS	151	=head1 WATCHERS
111		152
112	AnyEvent has the central concept of a I<watcher>, which is an object that	153	AnyEvent has the central concept of a I<watcher>, which is an object that
113	stores relevant data for each kind of event you are waiting for, such as	154	stores relevant data for each kind of event you are waiting for, such as
114	the callback to call, the filehandle to watch, etc.	155	the callback to call, the file handle to watch, etc.
115		156
116	These watchers are normal Perl objects with normal Perl lifetime. After	157	These watchers are normal Perl objects with normal Perl lifetime. After
117	creating a watcher it will immediately "watch" for events and invoke the	158	creating a watcher it will immediately "watch" for events and invoke the
118	callback when the event occurs (of course, only when the event model	159	callback when the event occurs (of course, only when the event model
119	is in control).	160	is in control).
120		161
		162	Note that B<callbacks must not permanently change global variables>
		163	potentially in use by the event loop (such as C<$_> or C<$[>) and that B<<
		164	callbacks must not C<die> >>. The former is good programming practice in
		165	Perl and the latter stems from the fact that exception handling differs
		166	widely between event loops.
		167
121	To disable the watcher you have to destroy it (e.g. by setting the	168	To disable a watcher you have to destroy it (e.g. by setting the
122	variable you store it in to C<undef> or otherwise deleting all references	169	variable you store it in to C<undef> or otherwise deleting all references
123	to it).	170	to it).
124		171
125	All watchers are created by calling a method on the C<AnyEvent> class.	172	All watchers are created by calling a method on the C<AnyEvent> class.
126		173
127	Many watchers either are used with "recursion" (repeating timers for	174	Many watchers either are used with "recursion" (repeating timers for
128	example), or need to refer to their watcher object in other ways.	175	example), or need to refer to their watcher object in other ways.
129		176
130	An any way to achieve that is this pattern:	177	One way to achieve that is this pattern:
131		178
132	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	179	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
133	# you can use $w here, for example to undef it	180	# you can use $w here, for example to undef it
134	undef $w;	181	undef $w;
135	});	182	});
136		183
137	Note that C<my $w; $w => combination. This is necessary because in Perl,	184	Note that C<my $w; $w => combination. This is necessary because in Perl,
138	my variables are only visible after the statement in which they are	185	my variables are only visible after the statement in which they are
139	declared.	186	declared.
140		187
141	=head2 I/O WATCHERS	188	=head2 I/O WATCHERS
142		189
		190	$w = AnyEvent->io (
		191	fh => <filehandle_or_fileno>,
		192	poll => <"r" or "w">,
		193	cb => <callback>,
		194	);
		195
143	You can create an I/O watcher by calling the C<< AnyEvent->io >> method	196	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
144	with the following mandatory key-value pairs as arguments:	197	with the following mandatory key-value pairs as arguments:
145		198
146	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch	199	C<fh> is the Perl I<file handle> (or a naked file descriptor) to watch
		200	for events (AnyEvent might or might not keep a reference to this file
		201	handle). Note that only file handles pointing to things for which
		202	non-blocking operation makes sense are allowed. This includes sockets,
		203	most character devices, pipes, fifos and so on, but not for example files
		204	or block devices.
		205
147	for events. C<poll> must be a string that is either C<r> or C<w>,	206	C<poll> must be a string that is either C<r> or C<w>, which creates a
148	which creates a watcher waiting for "r"eadable or "w"ritable events,	207	watcher waiting for "r"eadable or "w"ritable events, respectively.
		208
149	respectively. C<cb> is the callback to invoke each time the file handle	209	C<cb> is the callback to invoke each time the file handle becomes ready.
150	becomes ready.
151		210
152	Although the callback might get passed parameters, their value and	211	Although the callback might get passed parameters, their value and
153	presence is undefined and you cannot rely on them. Portable AnyEvent	212	presence is undefined and you cannot rely on them. Portable AnyEvent
154	callbacks cannot use arguments passed to I/O watcher callbacks.	213	callbacks cannot use arguments passed to I/O watcher callbacks.
155		214
156	The I/O watcher might use the underlying file descriptor or a copy of it.	215	The I/O watcher might use the underlying file descriptor or a copy of it.
157	You must not close a file handle as long as any watcher is active on the	216	You must not close a file handle as long as any watcher is active on the
158	underlying file descriptor.	217	underlying file descriptor.
159		218
160	Some event loops issue spurious readyness notifications, so you should	219	Some event loops issue spurious readiness notifications, so you should
161	always use non-blocking calls when reading/writing from/to your file	220	always use non-blocking calls when reading/writing from/to your file
162	handles.	221	handles.
163		222
164	Example:
165
166	# wait for readability of STDIN, then read a line and disable the watcher	223	Example: wait for readability of STDIN, then read a line and disable the
		224	watcher.
		225
167	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	226	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
168	chomp (my $input = <STDIN>);	227	chomp (my $input = <STDIN>);
169	warn "read: $input\n";	228	warn "read: $input\n";
170	undef $w;	229	undef $w;
171	});	230	});
172		231
173	=head2 TIME WATCHERS	232	=head2 TIME WATCHERS
174		233
		234	$w = AnyEvent->timer (after => <seconds>, cb => <callback>);
		235
		236	$w = AnyEvent->timer (
		237	after => <fractional_seconds>,
		238	interval => <fractional_seconds>,
		239	cb => <callback>,
		240	);
		241
175	You can create a time watcher by calling the C<< AnyEvent->timer >>	242	You can create a time watcher by calling the C<< AnyEvent->timer >>
176	method with the following mandatory arguments:	243	method with the following mandatory arguments:
177		244
178	C<after> specifies after how many seconds (fractional values are	245	C<after> specifies after how many seconds (fractional values are
179	supported) the callback should be invoked. C<cb> is the callback to invoke	246	supported) the callback should be invoked. C<cb> is the callback to invoke
…		…
181		248
182	Although the callback might get passed parameters, their value and	249	Although the callback might get passed parameters, their value and
183	presence is undefined and you cannot rely on them. Portable AnyEvent	250	presence is undefined and you cannot rely on them. Portable AnyEvent
184	callbacks cannot use arguments passed to time watcher callbacks.	251	callbacks cannot use arguments passed to time watcher callbacks.
185		252
186	The timer callback will be invoked at most once: if you want a repeating	253	The callback will normally be invoked only once. If you specify another
187	timer you have to create a new watcher (this is a limitation by both Tk	254	parameter, C<interval>, as a strictly positive number (> 0), then the
188	and Glib).	255	callback will be invoked regularly at that interval (in fractional
		256	seconds) after the first invocation. If C<interval> is specified with a
		257	false value, then it is treated as if it were not specified at all.
189		258
190	Example:	259	The callback will be rescheduled before invoking the callback, but no
		260	attempt is made to avoid timer drift in most backends, so the interval is
		261	only approximate.
191		262
192	# fire an event after 7.7 seconds	263	Example: fire an event after 7.7 seconds.
		264
193	my $w = AnyEvent->timer (after => 7.7, cb => sub {	265	my $w = AnyEvent->timer (after => 7.7, cb => sub {
194	warn "timeout\n";	266	warn "timeout\n";
195	});	267	});
196		268
197	# to cancel the timer:	269	# to cancel the timer:
198	undef $w;	270	undef $w;
199		271
200	Example 2:
201
202	# fire an event after 0.5 seconds, then roughly every second	272	Example 2: fire an event after 0.5 seconds, then roughly every second.
203	my $w;
204		273
205	my $cb = sub {
206	# cancel the old timer while creating a new one
207	$w = AnyEvent->timer (after => 1, cb => $cb);	274	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		275	warn "timeout\n";
208	};	276	};
209
210	# start the "loop" by creating the first watcher
211	$w = AnyEvent->timer (after => 0.5, cb => $cb);
212		277
213	=head3 TIMING ISSUES	278	=head3 TIMING ISSUES
214		279
215	There are two ways to handle timers: based on real time (relative, "fire	280	There are two ways to handle timers: based on real time (relative, "fire
216	in 10 seconds") and based on wallclock time (absolute, "fire at 12	281	in 10 seconds") and based on wallclock time (absolute, "fire at 12
…		…
218		283
219	While most event loops expect timers to specified in a relative way, they	284	While most event loops expect timers to specified in a relative way, they
220	use absolute time internally. This makes a difference when your clock	285	use absolute time internally. This makes a difference when your clock
221	"jumps", for example, when ntp decides to set your clock backwards from	286	"jumps", for example, when ntp decides to set your clock backwards from
222	the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to	287	the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to
223	fire "after" a second might actually take six years to finally fire.	288	fire "after a second" might actually take six years to finally fire.
224		289
225	AnyEvent cannot compensate for this. The only event loop that is conscious	290	AnyEvent cannot compensate for this. The only event loop that is conscious
226	about these issues is L<EV>, which offers both relative (ev_timer, based	291	of these issues is L<EV>, which offers both relative (ev_timer, based
227	on true relative time) and absolute (ev_periodic, based on wallclock time)	292	on true relative time) and absolute (ev_periodic, based on wallclock time)
228	timers.	293	timers.
229		294
230	AnyEvent always prefers relative timers, if available, matching the	295	AnyEvent always prefers relative timers, if available, matching the
231	AnyEvent API.	296	AnyEvent API.
232		297
		298	AnyEvent has two additional methods that return the "current time":
		299
		300	=over 4
		301
		302	=item AnyEvent->time
		303
		304	This returns the "current wallclock time" as a fractional number of
		305	seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
		306	return, and the result is guaranteed to be compatible with those).
		307
		308	It progresses independently of any event loop processing, i.e. each call
		309	will check the system clock, which usually gets updated frequently.
		310
		311	=item AnyEvent->now
		312
		313	This also returns the "current wallclock time", but unlike C<time>, above,
		314	this value might change only once per event loop iteration, depending on
		315	the event loop (most return the same time as C<time>, above). This is the
		316	time that AnyEvent's timers get scheduled against.
		317
		318	I<In almost all cases (in all cases if you don't care), this is the
		319	function to call when you want to know the current time.>
		320
		321	This function is also often faster then C<< AnyEvent->time >>, and
		322	thus the preferred method if you want some timestamp (for example,
		323	L<AnyEvent::Handle> uses this to update its activity timeouts).
		324
		325	The rest of this section is only of relevance if you try to be very exact
		326	with your timing; you can skip it without a bad conscience.
		327
		328	For a practical example of when these times differ, consider L<Event::Lib>
		329	and L<EV> and the following set-up:
		330
		331	The event loop is running and has just invoked one of your callbacks at
		332	time=500 (assume no other callbacks delay processing). In your callback,
		333	you wait a second by executing C<sleep 1> (blocking the process for a
		334	second) and then (at time=501) you create a relative timer that fires
		335	after three seconds.
		336
		337	With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
		338	both return C<501>, because that is the current time, and the timer will
		339	be scheduled to fire at time=504 (C<501> + C<3>).
		340
		341	With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
		342	time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
		343	last event processing phase started. With L<EV>, your timer gets scheduled
		344	to run at time=503 (C<500> + C<3>).
		345
		346	In one sense, L<Event::Lib> is more exact, as it uses the current time
		347	regardless of any delays introduced by event processing. However, most
		348	callbacks do not expect large delays in processing, so this causes a
		349	higher drift (and a lot more system calls to get the current time).
		350
		351	In another sense, L<EV> is more exact, as your timer will be scheduled at
		352	the same time, regardless of how long event processing actually took.
		353
		354	In either case, if you care (and in most cases, you don't), then you
		355	can get whatever behaviour you want with any event loop, by taking the
		356	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
		357	account.
		358
		359	=item AnyEvent->now_update
		360
		361	Some event loops (such as L<EV> or L<AnyEvent::Loop>) cache the current
		362	time for each loop iteration (see the discussion of L<< AnyEvent->now >>,
		363	above).
		364
		365	When a callback runs for a long time (or when the process sleeps), then
		366	this "current" time will differ substantially from the real time, which
		367	might affect timers and time-outs.
		368
		369	When this is the case, you can call this method, which will update the
		370	event loop's idea of "current time".
		371
		372	A typical example would be a script in a web server (e.g. C<mod_perl>) -
		373	when mod_perl executes the script, then the event loop will have the wrong
		374	idea about the "current time" (being potentially far in the past, when the
		375	script ran the last time). In that case you should arrange a call to C<<
		376	AnyEvent->now_update >> each time the web server process wakes up again
		377	(e.g. at the start of your script, or in a handler).
		378
		379	Note that updating the time I<might> cause some events to be handled.
		380
		381	=back
		382
233	=head2 SIGNAL WATCHERS	383	=head2 SIGNAL WATCHERS
234		384
		385	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		386
235	You can watch for signals using a signal watcher, C<signal> is the signal	387	You can watch for signals using a signal watcher, C<signal> is the signal
236	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to	388	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
237	be invoked whenever a signal occurs.	389	callback to be invoked whenever a signal occurs.
238		390
239	Although the callback might get passed parameters, their value and	391	Although the callback might get passed parameters, their value and
240	presence is undefined and you cannot rely on them. Portable AnyEvent	392	presence is undefined and you cannot rely on them. Portable AnyEvent
241	callbacks cannot use arguments passed to signal watcher callbacks.	393	callbacks cannot use arguments passed to signal watcher callbacks.
242		394
243	Multiple signal occurances can be clumped together into one callback	395	Multiple signal occurrences can be clumped together into one callback
244	invocation, and callback invocation will be synchronous. synchronous means	396	invocation, and callback invocation will be synchronous. Synchronous means
245	that it might take a while until the signal gets handled by the process,	397	that it might take a while until the signal gets handled by the process,
246	but it is guarenteed not to interrupt any other callbacks.	398	but it is guaranteed not to interrupt any other callbacks.
247		399
248	The main advantage of using these watchers is that you can share a signal	400	The main advantage of using these watchers is that you can share a signal
249	between multiple watchers.	401	between multiple watchers, and AnyEvent will ensure that signals will not
		402	interrupt your program at bad times.
250		403
251	This watcher might use C<%SIG>, so programs overwriting those signals	404	This watcher might use C<%SIG> (depending on the event loop used),
252	directly will likely not work correctly.	405	so programs overwriting those signals directly will likely not work
		406	correctly.
253		407
254	Example: exit on SIGINT	408	Example: exit on SIGINT
255		409
256	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	410	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
257		411
		412	=head3 Restart Behaviour
		413
		414	While restart behaviour is up to the event loop implementation, most will
		415	not restart syscalls (that includes L<Async::Interrupt> and AnyEvent's
		416	pure perl implementation).
		417
		418	=head3 Safe/Unsafe Signals
		419
		420	Perl signals can be either "safe" (synchronous to opcode handling) or
		421	"unsafe" (asynchronous) - the former might get delayed indefinitely, the
		422	latter might corrupt your memory.
		423
		424	AnyEvent signal handlers are, in addition, synchronous to the event loop,
		425	i.e. they will not interrupt your running perl program but will only be
		426	called as part of the normal event handling (just like timer, I/O etc.
		427	callbacks, too).
		428
		429	=head3 Signal Races, Delays and Workarounds
		430
		431	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		432	callbacks to signals in a generic way, which is a pity, as you cannot
		433	do race-free signal handling in perl, requiring C libraries for
		434	this. AnyEvent will try to do its best, which means in some cases,
		435	signals will be delayed. The maximum time a signal might be delayed is
		436	specified in C<$AnyEvent::MAX_SIGNAL_LATENCY> (default: 10 seconds). This
		437	variable can be changed only before the first signal watcher is created,
		438	and should be left alone otherwise. This variable determines how often
		439	AnyEvent polls for signals (in case a wake-up was missed). Higher values
		440	will cause fewer spurious wake-ups, which is better for power and CPU
		441	saving.
		442
		443	All these problems can be avoided by installing the optional
		444	L<Async::Interrupt> module, which works with most event loops. It will not
		445	work with inherently broken event loops such as L<Event> or L<Event::Lib>
		446	(and not with L<POE> currently, as POE does its own workaround with
		447	one-second latency). For those, you just have to suffer the delays.
		448
258	=head2 CHILD PROCESS WATCHERS	449	=head2 CHILD PROCESS WATCHERS
259		450
		451	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		452
260	You can also watch on a child process exit and catch its exit status.	453	You can also watch for a child process exit and catch its exit status.
261		454
262	The child process is specified by the C<pid> argument (if set to C<0>, it	455	The child process is specified by the C<pid> argument (on some backends,
263	watches for any child process exit). The watcher will trigger as often	456	using C<0> watches for any child process exit, on others this will
264	as status change for the child are received. This works by installing a	457	croak). The watcher will be triggered only when the child process has
265	signal handler for C<SIGCHLD>. The callback will be called with the pid	458	finished and an exit status is available, not on any trace events
266	and exit status (as returned by waitpid), so unlike other watcher types,	459	(stopped/continued).
267	you I<can> rely on child watcher callback arguments.	460
		461	The callback will be called with the pid and exit status (as returned by
		462	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		463	callback arguments.
		464
		465	This watcher type works by installing a signal handler for C<SIGCHLD>,
		466	and since it cannot be shared, nothing else should use SIGCHLD or reap
		467	random child processes (waiting for specific child processes, e.g. inside
		468	C<system>, is just fine).
268		469
269	There is a slight catch to child watchers, however: you usually start them	470	There is a slight catch to child watchers, however: you usually start them
270	I<after> the child process was created, and this means the process could	471	I<after> the child process was created, and this means the process could
271	have exited already (and no SIGCHLD will be sent anymore).	472	have exited already (and no SIGCHLD will be sent anymore).
272		473
273	Not all event models handle this correctly (POE doesn't), but even for	474	Not all event models handle this correctly (neither POE nor IO::Async do,
		475	see their AnyEvent::Impl manpages for details), but even for event models
274	event models that I<do> handle this correctly, they usually need to be	476	that I<do> handle this correctly, they usually need to be loaded before
275	loaded before the process exits (i.e. before you fork in the first place).	477	the process exits (i.e. before you fork in the first place). AnyEvent's
		478	pure perl event loop handles all cases correctly regardless of when you
		479	start the watcher.
276		480
277	This means you cannot create a child watcher as the very first thing in an	481	This means you cannot create a child watcher as the very first
278	AnyEvent program, you I<have> to create at least one watcher before you	482	thing in an AnyEvent program, you I<have> to create at least one
279	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).	483	watcher before you C<fork> the child (alternatively, you can call
		484	C<AnyEvent::detect>).
		485
		486	As most event loops do not support waiting for child events, they will be
		487	emulated by AnyEvent in most cases, in which case the latency and race
		488	problems mentioned in the description of signal watchers apply.
280		489
281	Example: fork a process and wait for it	490	Example: fork a process and wait for it
282		491
283	my $done = AnyEvent->condvar;	492	my $done = AnyEvent->condvar;
284		493
285	AnyEvent::detect; # force event module to be initialised
286
287	my $pid = fork or exit 5;	494	my $pid = fork or exit 5;
288		495
289	my $w = AnyEvent->child (	496	my $w = AnyEvent->child (
290	pid => $pid,	497	pid => $pid,
291	cb => sub {	498	cb => sub {
292	my ($pid, $status) = @_;	499	my ($pid, $status) = @_;
293	warn "pid $pid exited with status $status";	500	warn "pid $pid exited with status $status";
294	$done->broadcast;	501	$done->send;
295	},	502	},
296	);	503	);
297		504
298	# do something else, then wait for process exit	505	# do something else, then wait for process exit
299	$done->wait;	506	$done->recv;
		507
		508	=head2 IDLE WATCHERS
		509
		510	$w = AnyEvent->idle (cb => <callback>);
		511
		512	This will repeatedly invoke the callback after the process becomes idle,
		513	until either the watcher is destroyed or new events have been detected.
		514
		515	Idle watchers are useful when there is a need to do something, but it
		516	is not so important (or wise) to do it instantly. The callback will be
		517	invoked only when there is "nothing better to do", which is usually
		518	defined as "all outstanding events have been handled and no new events
		519	have been detected". That means that idle watchers ideally get invoked
		520	when the event loop has just polled for new events but none have been
		521	detected. Instead of blocking to wait for more events, the idle watchers
		522	will be invoked.
		523
		524	Unfortunately, most event loops do not really support idle watchers (only
		525	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		526	will simply call the callback "from time to time".
		527
		528	Example: read lines from STDIN, but only process them when the
		529	program is otherwise idle:
		530
		531	my @lines; # read data
		532	my $idle_w;
		533	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		534	push @lines, scalar <STDIN>;
		535
		536	# start an idle watcher, if not already done
		537	$idle_w ||= AnyEvent->idle (cb => sub {
		538	# handle only one line, when there are lines left
		539	if (my $line = shift @lines) {
		540	print "handled when idle: $line";
		541	} else {
		542	# otherwise disable the idle watcher again
		543	undef $idle_w;
		544	}
		545	});
		546	});
300		547
301	=head2 CONDITION VARIABLES	548	=head2 CONDITION VARIABLES
302		549
		550	$cv = AnyEvent->condvar;
		551
		552	$cv->send (<list>);
		553	my @res = $cv->recv;
		554
		555	If you are familiar with some event loops you will know that all of them
		556	require you to run some blocking "loop", "run" or similar function that
		557	will actively watch for new events and call your callbacks.
		558
		559	AnyEvent is slightly different: it expects somebody else to run the event
		560	loop and will only block when necessary (usually when told by the user).
		561
		562	The tool to do that is called a "condition variable", so called because
		563	they represent a condition that must become true.
		564
		565	Now is probably a good time to look at the examples further below.
		566
303	Condition variables can be created by calling the C<< AnyEvent->condvar >>	567	Condition variables can be created by calling the C<< AnyEvent->condvar
304	method without any arguments.	568	>> method, usually without arguments. The only argument pair allowed is
		569	C<cb>, which specifies a callback to be called when the condition variable
		570	becomes true, with the condition variable as the first argument (but not
		571	the results).
305		572
306	A condition variable waits for a condition - precisely that the C<<	573	After creation, the condition variable is "false" until it becomes "true"
307	->broadcast >> method has been called.	574	by calling the C<send> method (or calling the condition variable as if it
		575	were a callback, read about the caveats in the description for the C<<
		576	->send >> method).
308		577
309	They are very useful to signal that a condition has been fulfilled, for	578	Since condition variables are the most complex part of the AnyEvent API, here are
		579	some different mental models of what they are - pick the ones you can connect to:
		580
		581	=over 4
		582
		583	=item * Condition variables are like callbacks - you can call them (and pass them instead
		584	of callbacks). Unlike callbacks however, you can also wait for them to be called.
		585
		586	=item * Condition variables are signals - one side can emit or send them,
		587	the other side can wait for them, or install a handler that is called when
		588	the signal fires.
		589
		590	=item * Condition variables are like "Merge Points" - points in your program
		591	where you merge multiple independent results/control flows into one.
		592
		593	=item * Condition variables represent a transaction - functions that start
		594	some kind of transaction can return them, leaving the caller the choice
		595	between waiting in a blocking fashion, or setting a callback.
		596
		597	=item * Condition variables represent future values, or promises to deliver
		598	some result, long before the result is available.
		599
		600	=back
		601
		602	Condition variables are very useful to signal that something has finished,
310	example, if you write a module that does asynchronous http requests,	603	for example, if you write a module that does asynchronous http requests,
311	then a condition variable would be the ideal candidate to signal the	604	then a condition variable would be the ideal candidate to signal the
312	availability of results.	605	availability of results. The user can either act when the callback is
		606	called or can synchronously C<< ->recv >> for the results.
313		607
314	You can also use condition variables to block your main program until	608	You can also use them to simulate traditional event loops - for example,
315	an event occurs - for example, you could C<< ->wait >> in your main	609	you can block your main program until an event occurs - for example, you
316	program until the user clicks the Quit button in your app, which would C<<	610	could C<< ->recv >> in your main program until the user clicks the Quit
317	->broadcast >> the "quit" event.	611	button of your app, which would C<< ->send >> the "quit" event.
318		612
319	Note that condition variables recurse into the event loop - if you have	613	Note that condition variables recurse into the event loop - if you have
320	two pirces of code that call C<< ->wait >> in a round-robbin fashion, you	614	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
321	lose. Therefore, condition variables are good to export to your caller, but	615	lose. Therefore, condition variables are good to export to your caller, but
322	you should avoid making a blocking wait yourself, at least in callbacks,	616	you should avoid making a blocking wait yourself, at least in callbacks,
323	as this asks for trouble.	617	as this asks for trouble.
324		618
325	This object has two methods:	619	Condition variables are represented by hash refs in perl, and the keys
		620	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
		621	easy (it is often useful to build your own transaction class on top of
		622	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
		623	its C<new> method in your own C<new> method.
		624
		625	There are two "sides" to a condition variable - the "producer side" which
		626	eventually calls C<< -> send >>, and the "consumer side", which waits
		627	for the send to occur.
		628
		629	Example: wait for a timer.
		630
		631	# condition: "wait till the timer is fired"
		632	my $timer_fired = AnyEvent->condvar;
		633
		634	# create the timer - we could wait for, say
		635	# a handle becomign ready, or even an
		636	# AnyEvent::HTTP request to finish, but
		637	# in this case, we simply use a timer:
		638	my $w = AnyEvent->timer (
		639	after => 1,
		640	cb => sub { $timer_fired->send },
		641	);
		642
		643	# this "blocks" (while handling events) till the callback
		644	# calls ->send
		645	$timer_fired->recv;
		646
		647	Example: wait for a timer, but take advantage of the fact that condition
		648	variables are also callable directly.
		649
		650	my $done = AnyEvent->condvar;
		651	my $delay = AnyEvent->timer (after => 5, cb => $done);
		652	$done->recv;
		653
		654	Example: Imagine an API that returns a condvar and doesn't support
		655	callbacks. This is how you make a synchronous call, for example from
		656	the main program:
		657
		658	use AnyEvent::CouchDB;
		659
		660	...
		661
		662	my @info = $couchdb->info->recv;
		663
		664	And this is how you would just set a callback to be called whenever the
		665	results are available:
		666
		667	$couchdb->info->cb (sub {
		668	my @info = $_[0]->recv;
		669	});
		670
		671	=head3 METHODS FOR PRODUCERS
		672
		673	These methods should only be used by the producing side, i.e. the
		674	code/module that eventually sends the signal. Note that it is also
		675	the producer side which creates the condvar in most cases, but it isn't
		676	uncommon for the consumer to create it as well.
326		677
327	=over 4	678	=over 4
328		679
		680	=item $cv->send (...)
		681
		682	Flag the condition as ready - a running C<< ->recv >> and all further
		683	calls to C<recv> will (eventually) return after this method has been
		684	called. If nobody is waiting the send will be remembered.
		685
		686	If a callback has been set on the condition variable, it is called
		687	immediately from within send.
		688
		689	Any arguments passed to the C<send> call will be returned by all
		690	future C<< ->recv >> calls.
		691
		692	Condition variables are overloaded so one can call them directly (as if
		693	they were a code reference). Calling them directly is the same as calling
		694	C<send>.
		695
		696	=item $cv->croak ($error)
		697
		698	Similar to send, but causes all calls to C<< ->recv >> to invoke
		699	C<Carp::croak> with the given error message/object/scalar.
		700
		701	This can be used to signal any errors to the condition variable
		702	user/consumer. Doing it this way instead of calling C<croak> directly
		703	delays the error detection, but has the overwhelming advantage that it
		704	diagnoses the error at the place where the result is expected, and not
		705	deep in some event callback with no connection to the actual code causing
		706	the problem.
		707
		708	=item $cv->begin ([group callback])
		709
329	=item $cv->wait	710	=item $cv->end
330		711
331	Wait (blocking if necessary) until the C<< ->broadcast >> method has been	712	These two methods can be used to combine many transactions/events into
332	called on c<$cv>, while servicing other watchers normally.	713	one. For example, a function that pings many hosts in parallel might want
		714	to use a condition variable for the whole process.
333		715
		716	Every call to C<< ->begin >> will increment a counter, and every call to
		717	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
		718	>>, the (last) callback passed to C<begin> will be executed, passing the
		719	condvar as first argument. That callback is I<supposed> to call C<< ->send
		720	>>, but that is not required. If no group callback was set, C<send> will
		721	be called without any arguments.
		722
		723	You can think of C<< $cv->send >> giving you an OR condition (one call
		724	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		725	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		726
		727	Let's start with a simple example: you have two I/O watchers (for example,
		728	STDOUT and STDERR for a program), and you want to wait for both streams to
		729	close before activating a condvar:
		730
		731	my $cv = AnyEvent->condvar;
		732
		733	$cv->begin; # first watcher
		734	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		735	defined sysread $fh1, my $buf, 4096
		736	or $cv->end;
		737	});
		738
		739	$cv->begin; # second watcher
		740	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		741	defined sysread $fh2, my $buf, 4096
		742	or $cv->end;
		743	});
		744
		745	$cv->recv;
		746
		747	This works because for every event source (EOF on file handle), there is
		748	one call to C<begin>, so the condvar waits for all calls to C<end> before
		749	sending.
		750
		751	The ping example mentioned above is slightly more complicated, as the
		752	there are results to be passwd back, and the number of tasks that are
		753	begun can potentially be zero:
		754
		755	my $cv = AnyEvent->condvar;
		756
		757	my %result;
		758	$cv->begin (sub { shift->send (\%result) });
		759
		760	for my $host (@list_of_hosts) {
		761	$cv->begin;
		762	ping_host_then_call_callback $host, sub {
		763	$result{$host} = ...;
		764	$cv->end;
		765	};
		766	}
		767
		768	$cv->end;
		769
		770	This code fragment supposedly pings a number of hosts and calls
		771	C<send> after results for all then have have been gathered - in any
		772	order. To achieve this, the code issues a call to C<begin> when it starts
		773	each ping request and calls C<end> when it has received some result for
		774	it. Since C<begin> and C<end> only maintain a counter, the order in which
		775	results arrive is not relevant.
		776
		777	There is an additional bracketing call to C<begin> and C<end> outside the
		778	loop, which serves two important purposes: first, it sets the callback
		779	to be called once the counter reaches C<0>, and second, it ensures that
		780	C<send> is called even when C<no> hosts are being pinged (the loop
		781	doesn't execute once).
		782
		783	This is the general pattern when you "fan out" into multiple (but
		784	potentially zero) subrequests: use an outer C<begin>/C<end> pair to set
		785	the callback and ensure C<end> is called at least once, and then, for each
		786	subrequest you start, call C<begin> and for each subrequest you finish,
		787	call C<end>.
		788
		789	=back
		790
		791	=head3 METHODS FOR CONSUMERS
		792
		793	These methods should only be used by the consuming side, i.e. the
		794	code awaits the condition.
		795
		796	=over 4
		797
		798	=item $cv->recv
		799
		800	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
		801	>> methods have been called on C<$cv>, while servicing other watchers
		802	normally.
		803
334	You can only wait once on a condition - additional calls will return	804	You can only wait once on a condition - additional calls are valid but
335	immediately.	805	will return immediately.
		806
		807	If an error condition has been set by calling C<< ->croak >>, then this
		808	function will call C<croak>.
		809
		810	In list context, all parameters passed to C<send> will be returned,
		811	in scalar context only the first one will be returned.
		812
		813	Note that doing a blocking wait in a callback is not supported by any
		814	event loop, that is, recursive invocation of a blocking C<< ->recv
		815	>> is not allowed, and the C<recv> call will C<croak> if such a
		816	condition is detected. This condition can be slightly loosened by using
		817	L<Coro::AnyEvent>, which allows you to do a blocking C<< ->recv >> from
		818	any thread that doesn't run the event loop itself.
336		819
337	Not all event models support a blocking wait - some die in that case	820	Not all event models support a blocking wait - some die in that case
338	(programs might want to do that to stay interactive), so I<if you are	821	(programs might want to do that to stay interactive), so I<if you are
339	using this from a module, never require a blocking wait>, but let the	822	using this from a module, never require a blocking wait>. Instead, let the
340	caller decide whether the call will block or not (for example, by coupling	823	caller decide whether the call will block or not (for example, by coupling
341	condition variables with some kind of request results and supporting	824	condition variables with some kind of request results and supporting
342	callbacks so the caller knows that getting the result will not block,	825	callbacks so the caller knows that getting the result will not block,
343	while still suppporting blocking waits if the caller so desires).	826	while still supporting blocking waits if the caller so desires).
344		827
345	Another reason I<never> to C<< ->wait >> in a module is that you cannot	828	You can ensure that C<< ->recv >> never blocks by setting a callback and
346	sensibly have two C<< ->wait >>'s in parallel, as that would require	829	only calling C<< ->recv >> from within that callback (or at a later
347	multiple interpreters or coroutines/threads, none of which C<AnyEvent>	830	time). This will work even when the event loop does not support blocking
348	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and	831	waits otherwise.
349	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
350	from different coroutines, however).
351		832
352	=item $cv->broadcast	833	=item $bool = $cv->ready
353		834
354	Flag the condition as ready - a running C<< ->wait >> and all further	835	Returns true when the condition is "true", i.e. whether C<send> or
355	calls to C<wait> will (eventually) return after this method has been	836	C<croak> have been called.
356	called. If nobody is waiting the broadcast will be remembered..	837
		838	=item $cb = $cv->cb ($cb->($cv))
		839
		840	This is a mutator function that returns the callback set and optionally
		841	replaces it before doing so.
		842
		843	The callback will be called when the condition becomes "true", i.e. when
		844	C<send> or C<croak> are called, with the only argument being the
		845	condition variable itself. If the condition is already true, the
		846	callback is called immediately when it is set. Calling C<recv> inside
		847	the callback or at any later time is guaranteed not to block.
357		848
358	=back	849	=back
359		850
360	Example:	851	=head1 SUPPORTED EVENT LOOPS/BACKENDS
361		852
362	# wait till the result is ready	853	The available backend classes are (every class has its own manpage):
363	my $result_ready = AnyEvent->condvar;
364		854
365	# do something such as adding a timer	855	=over 4
366	# or socket watcher the calls $result_ready->broadcast
367	# when the "result" is ready.
368	# in this case, we simply use a timer:
369	my $w = AnyEvent->timer (
370	after => 1,
371	cb => sub { $result_ready->broadcast },
372	);
373		856
374	# this "blocks" (while handling events) till the watcher	857	=item Backends that are autoprobed when no other event loop can be found.
375	# calls broadcast	858
376	$result_ready->wait;	859	EV is the preferred backend when no other event loop seems to be in
		860	use. If EV is not installed, then AnyEvent will fall back to its own
		861	pure-perl implementation, which is available everywhere as it comes with
		862	AnyEvent itself.
		863
		864	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		865	AnyEvent::Impl::Perl pure-perl AnyEvent::Loop, fast and portable.
		866
		867	=item Backends that are transparently being picked up when they are used.
		868
		869	These will be used if they are already loaded when the first watcher
		870	is created, in which case it is assumed that the application is using
		871	them. This means that AnyEvent will automatically pick the right backend
		872	when the main program loads an event module before anything starts to
		873	create watchers. Nothing special needs to be done by the main program.
		874
		875	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		876	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		877	AnyEvent::Impl::Tk based on Tk, very broken.
		878	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		879	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		880	AnyEvent::Impl::Irssi used when running within irssi.
		881	AnyEvent::Impl::IOAsync based on IO::Async.
		882	AnyEvent::Impl::Cocoa based on Cocoa::EventLoop.
		883	AnyEvent::Impl::FLTK2 based on FLTK (fltk 2 binding).
		884
		885	=item Backends with special needs.
		886
		887	Qt requires the Qt::Application to be instantiated first, but will
		888	otherwise be picked up automatically. As long as the main program
		889	instantiates the application before any AnyEvent watchers are created,
		890	everything should just work.
		891
		892	AnyEvent::Impl::Qt based on Qt.
		893
		894	=item Event loops that are indirectly supported via other backends.
		895
		896	Some event loops can be supported via other modules:
		897
		898	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		899
		900	B<WxWidgets> has no support for watching file handles. However, you can
		901	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		902	polls 20 times per second, which was considered to be too horrible to even
		903	consider for AnyEvent.
		904
		905	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		906	backend, so it can be supported through POE.
		907
		908	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		909	load L<POE> when detecting them, in the hope that POE will pick them up,
		910	in which case everything will be automatic.
		911
		912	=back
377		913
378	=head1 GLOBAL VARIABLES AND FUNCTIONS	914	=head1 GLOBAL VARIABLES AND FUNCTIONS
379		915
		916	These are not normally required to use AnyEvent, but can be useful to
		917	write AnyEvent extension modules.
		918
380	=over 4	919	=over 4
381		920
382	=item $AnyEvent::MODEL	921	=item $AnyEvent::MODEL
383		922
384	Contains C<undef> until the first watcher is being created. Then it	923	Contains C<undef> until the first watcher is being created, before the
		924	backend has been autodetected.
		925
385	contains the event model that is being used, which is the name of the	926	Afterwards it contains the event model that is being used, which is the
386	Perl class implementing the model. This class is usually one of the	927	name of the Perl class implementing the model. This class is usually one
387	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	928	of the C<AnyEvent::Impl::xxx> modules, but can be any other class in the
388	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	929	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
389		930	will be C<urxvt::anyevent>).
390	The known classes so far are:
391
392	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
393	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
394	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
395	AnyEvent::Impl::Event based on Event, second best choice.
396	AnyEvent::Impl::Glib based on Glib, third-best choice.
397	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
398	AnyEvent::Impl::Tk based on Tk, very bad choice.
399	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
400	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
401	AnyEvent::Impl::POE based on POE, not generic enough for full support.
402
403	There is no support for WxWidgets, as WxWidgets has no support for
404	watching file handles. However, you can use WxWidgets through the
405	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
406	second, which was considered to be too horrible to even consider for
407	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
408	it's adaptor.
409
410	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
411	autodetecting them.
412		931
413	=item AnyEvent::detect	932	=item AnyEvent::detect
414		933
415	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	934	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
416	if necessary. You should only call this function right before you would	935	if necessary. You should only call this function right before you would
417	have created an AnyEvent watcher anyway, that is, as late as possible at	936	have created an AnyEvent watcher anyway, that is, as late as possible at
418	runtime.	937	runtime, and not e.g. during initialisation of your module.
		938
		939	The effect of calling this function is as if a watcher had been created
		940	(specifically, actions that happen "when the first watcher is created"
		941	happen when calling detetc as well).
		942
		943	If you need to do some initialisation before AnyEvent watchers are
		944	created, use C<post_detect>.
		945
		946	=item $guard = AnyEvent::post_detect { BLOCK }
		947
		948	Arranges for the code block to be executed as soon as the event model is
		949	autodetected (or immediately if that has already happened).
		950
		951	The block will be executed I<after> the actual backend has been detected
		952	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		953	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		954	other initialisations - see the sources of L<AnyEvent::Strict> or
		955	L<AnyEvent::AIO> to see how this is used.
		956
		957	The most common usage is to create some global watchers, without forcing
		958	event module detection too early, for example, L<AnyEvent::AIO> creates
		959	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		960	avoid autodetecting the event module at load time.
		961
		962	If called in scalar or list context, then it creates and returns an object
		963	that automatically removes the callback again when it is destroyed (or
		964	C<undef> when the hook was immediately executed). See L<AnyEvent::AIO> for
		965	a case where this is useful.
		966
		967	Example: Create a watcher for the IO::AIO module and store it in
		968	C<$WATCHER>, but do so only do so after the event loop is initialised.
		969
		970	our WATCHER;
		971
		972	my $guard = AnyEvent::post_detect {
		973	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		974	};
		975
		976	# the ||= is important in case post_detect immediately runs the block,
		977	# as to not clobber the newly-created watcher. assigning both watcher and
		978	# post_detect guard to the same variable has the advantage of users being
		979	# able to just C<undef $WATCHER> if the watcher causes them grief.
		980
		981	$WATCHER ||= $guard;
		982
		983	=item @AnyEvent::post_detect
		984
		985	If there are any code references in this array (you can C<push> to it
		986	before or after loading AnyEvent), then they will be called directly
		987	after the event loop has been chosen.
		988
		989	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		990	if it is defined then the event loop has already been detected, and the
		991	array will be ignored.
		992
		993	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		994	it, as it takes care of these details.
		995
		996	This variable is mainly useful for modules that can do something useful
		997	when AnyEvent is used and thus want to know when it is initialised, but do
		998	not need to even load it by default. This array provides the means to hook
		999	into AnyEvent passively, without loading it.
		1000
		1001	Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used
		1002	together, you could put this into Coro (this is the actual code used by
		1003	Coro to accomplish this):
		1004
		1005	if (defined $AnyEvent::MODEL) {
		1006	# AnyEvent already initialised, so load Coro::AnyEvent
		1007	require Coro::AnyEvent;
		1008	} else {
		1009	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent
		1010	# as soon as it is
		1011	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };
		1012	}
		1013
		1014	=item AnyEvent::postpone { BLOCK }
		1015
		1016	Arranges for the block to be executed as soon as possible, but not before
		1017	the call itself returns. In practise, the block will be executed just
		1018	before the event loop polls for new events, or shortly afterwards.
		1019
		1020	This function never returns anything (to make the C<return postpone { ...
		1021	}> idiom more useful.
		1022
		1023	To understand the usefulness of this function, consider a function that
		1024	asynchronously does something for you and returns some transaction
		1025	object or guard to let you cancel the operation. For example,
		1026	C<AnyEvent::Socket::tcp_connect>:
		1027
		1028	# start a conenction attempt unless one is active
		1029	$self->{connect_guard} ||= AnyEvent::Socket::tcp_connect "www.example.net", 80, sub {
		1030	delete $self->{connect_guard};
		1031	...
		1032	};
		1033
		1034	Imagine that this function could instantly call the callback, for
		1035	example, because it detects an obvious error such as a negative port
		1036	number. Invoking the callback before the function returns causes problems
		1037	however: the callback will be called and will try to delete the guard
		1038	object. But since the function hasn't returned yet, there is nothing to
		1039	delete. When the function eventually returns it will assign the guard
		1040	object to C<< $self->{connect_guard} >>, where it will likely never be
		1041	deleted, so the program thinks it is still trying to connect.
		1042
		1043	This is where C<AnyEvent::postpone> should be used. Instead of calling the
		1044	callback directly on error:
		1045
		1046	$cb->(undef), return # signal error to callback, BAD!
		1047	if $some_error_condition;
		1048
		1049	It should use C<postpone>:
		1050
		1051	AnyEvent::postpone { $cb->(undef) }, return # signal error to callback, later
		1052	if $some_error_condition;
		1053
		1054	=item AnyEvent::log $level, $msg[, @args]
		1055
		1056	Log the given C<$msg> at the given C<$level>.
		1057
		1058	If L<AnyEvent::Log> is not loaded then this function makes a simple test
		1059	to see whether the message will be logged. If the test succeeds it will
		1060	load AnyEvent::Log and call C<AnyEvent::Log::log> - consequently, look at
		1061	the L<AnyEvent::Log> documentation for details.
		1062
		1063	If the test fails it will simply return.
		1064
		1065	If you want to sprinkle loads of logging calls around your code, consider
		1066	creating a logger callback with the C<AnyEvent::Log::logger> function,
		1067	which can reduce typing, codesize and can reduce the logging overhead
		1068	enourmously.
419		1069
420	=back	1070	=back
421		1071
422	=head1 WHAT TO DO IN A MODULE	1072	=head1 WHAT TO DO IN A MODULE
423		1073
…		…
427	Be careful when you create watchers in the module body - AnyEvent will	1077	Be careful when you create watchers in the module body - AnyEvent will
428	decide which event module to use as soon as the first method is called, so	1078	decide which event module to use as soon as the first method is called, so
429	by calling AnyEvent in your module body you force the user of your module	1079	by calling AnyEvent in your module body you force the user of your module
430	to load the event module first.	1080	to load the event module first.
431		1081
432	Never call C<< ->wait >> on a condition variable unless you I<know> that	1082	Never call C<< ->recv >> on a condition variable unless you I<know> that
433	the C<< ->broadcast >> method has been called on it already. This is	1083	the C<< ->send >> method has been called on it already. This is
434	because it will stall the whole program, and the whole point of using	1084	because it will stall the whole program, and the whole point of using
435	events is to stay interactive.	1085	events is to stay interactive.
436		1086
437	It is fine, however, to call C<< ->wait >> when the user of your module	1087	It is fine, however, to call C<< ->recv >> when the user of your module
438	requests it (i.e. if you create a http request object ad have a method	1088	requests it (i.e. if you create a http request object ad have a method
439	called C<results> that returns the results, it should call C<< ->wait >>	1089	called C<results> that returns the results, it may call C<< ->recv >>
440	freely, as the user of your module knows what she is doing. always).	1090	freely, as the user of your module knows what she is doing. Always).
441		1091
442	=head1 WHAT TO DO IN THE MAIN PROGRAM	1092	=head1 WHAT TO DO IN THE MAIN PROGRAM
443		1093
444	There will always be a single main program - the only place that should	1094	There will always be a single main program - the only place that should
445	dictate which event model to use.	1095	dictate which event model to use.
446		1096
447	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	1097	If the program is not event-based, it need not do anything special, even
448	do anything special (it does not need to be event-based) and let AnyEvent	1098	when it depends on a module that uses an AnyEvent. If the program itself
449	decide which implementation to chose if some module relies on it.	1099	uses AnyEvent, but does not care which event loop is used, all it needs
		1100	to do is C<use AnyEvent>. In either case, AnyEvent will choose the best
		1101	available loop implementation.
450		1102
451	If the main program relies on a specific event model. For example, in	1103	If the main program relies on a specific event model - for example, in
452	Gtk2 programs you have to rely on the Glib module. You should load the	1104	Gtk2 programs you have to rely on the Glib module - you should load the
453	event module before loading AnyEvent or any module that uses it: generally	1105	event module before loading AnyEvent or any module that uses it: generally
454	speaking, you should load it as early as possible. The reason is that	1106	speaking, you should load it as early as possible. The reason is that
455	modules might create watchers when they are loaded, and AnyEvent will	1107	modules might create watchers when they are loaded, and AnyEvent will
456	decide on the event model to use as soon as it creates watchers, and it	1108	decide on the event model to use as soon as it creates watchers, and it
457	might chose the wrong one unless you load the correct one yourself.	1109	might choose the wrong one unless you load the correct one yourself.
458		1110
459	You can chose to use a rather inefficient pure-perl implementation by	1111	You can chose to use a pure-perl implementation by loading the
460	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	1112	C<AnyEvent::Loop> module, which gives you similar behaviour
461	behaviour everywhere, but letting AnyEvent chose is generally better.	1113	everywhere, but letting AnyEvent chose the model is generally better.
		1114
		1115	=head2 MAINLOOP EMULATION
		1116
		1117	Sometimes (often for short test scripts, or even standalone programs who
		1118	only want to use AnyEvent), you do not want to run a specific event loop.
		1119
		1120	In that case, you can use a condition variable like this:
		1121
		1122	AnyEvent->condvar->recv;
		1123
		1124	This has the effect of entering the event loop and looping forever.
		1125
		1126	Note that usually your program has some exit condition, in which case
		1127	it is better to use the "traditional" approach of storing a condition
		1128	variable somewhere, waiting for it, and sending it when the program should
		1129	exit cleanly.
		1130
		1131
		1132	=head1 OTHER MODULES
		1133
		1134	The following is a non-exhaustive list of additional modules that use
		1135	AnyEvent as a client and can therefore be mixed easily with other
		1136	AnyEvent modules and other event loops in the same program. Some of the
		1137	modules come as part of AnyEvent, the others are available via CPAN (see
		1138	L<http://search.cpan.org/search?m=module&q=anyevent%3A%3A*> for
		1139	a longer non-exhaustive list), and the list is heavily biased towards
		1140	modules of the AnyEvent author himself :)
		1141
		1142	=over 4
		1143
		1144	=item L<AnyEvent::Util>
		1145
		1146	Contains various utility functions that replace often-used blocking
		1147	functions such as C<inet_aton> with event/callback-based versions.
		1148
		1149	=item L<AnyEvent::Socket>
		1150
		1151	Provides various utility functions for (internet protocol) sockets,
		1152	addresses and name resolution. Also functions to create non-blocking tcp
		1153	connections or tcp servers, with IPv6 and SRV record support and more.
		1154
		1155	=item L<AnyEvent::Handle>
		1156
		1157	Provide read and write buffers, manages watchers for reads and writes,
		1158	supports raw and formatted I/O, I/O queued and fully transparent and
		1159	non-blocking SSL/TLS (via L<AnyEvent::TLS>).
		1160
		1161	=item L<AnyEvent::DNS>
		1162
		1163	Provides rich asynchronous DNS resolver capabilities.
		1164
		1165	=item L<AnyEvent::HTTP>, L<AnyEvent::IRC>, L<AnyEvent::XMPP>, L<AnyEvent::GPSD>, L<AnyEvent::IGS>, L<AnyEvent::FCP>
		1166
		1167	Implement event-based interfaces to the protocols of the same name (for
		1168	the curious, IGS is the International Go Server and FCP is the Freenet
		1169	Client Protocol).
		1170
		1171	=item L<AnyEvent::Handle::UDP>
		1172
		1173	Here be danger!
		1174
		1175	As Pauli would put it, "Not only is it not right, it's not even wrong!" -
		1176	there are so many things wrong with AnyEvent::Handle::UDP, most notably
		1177	its use of a stream-based API with a protocol that isn't streamable, that
		1178	the only way to improve it is to delete it.
		1179
		1180	It features data corruption (but typically only under load) and general
		1181	confusion. On top, the author is not only clueless about UDP but also
		1182	fact-resistant - some gems of his understanding: "connect doesn't work
		1183	with UDP", "UDP packets are not IP packets", "UDP only has datagrams, not
		1184	packets", "I don't need to implement proper error checking as UDP doesn't
		1185	support error checking" and so on - he doesn't even understand what's
		1186	wrong with his module when it is explained to him.
		1187
		1188	=item L<AnyEvent::DBI>
		1189
		1190	Executes L<DBI> requests asynchronously in a proxy process for you,
		1191	notifying you in an event-based way when the operation is finished.
		1192
		1193	=item L<AnyEvent::AIO>
		1194
		1195	Truly asynchronous (as opposed to non-blocking) I/O, should be in the
		1196	toolbox of every event programmer. AnyEvent::AIO transparently fuses
		1197	L<IO::AIO> and AnyEvent together, giving AnyEvent access to event-based
		1198	file I/O, and much more.
		1199
		1200	=item L<AnyEvent::HTTPD>
		1201
		1202	A simple embedded webserver.
		1203
		1204	=item L<AnyEvent::FastPing>
		1205
		1206	The fastest ping in the west.
		1207
		1208	=item L<Coro>
		1209
		1210	Has special support for AnyEvent via L<Coro::AnyEvent>.
		1211
		1212	=back
462		1213
463	=cut	1214	=cut
464		1215
465	package AnyEvent;	1216	package AnyEvent;
466		1217
467	no warnings;	1218	# basically a tuned-down version of common::sense
468	use strict;	1219	sub common_sense {
		1220	# from common:.sense 3.4
		1221	${^WARNING_BITS} ^= ${^WARNING_BITS} ^ "\x3c\x3f\x33\x00\x0f\xf0\x0f\xc0\xf0\xfc\x33\x00";
		1222	# use strict vars subs - NO UTF-8, as Util.pm doesn't like this atm. (uts46data.pl)
		1223	$^H |= 0x00000600;
		1224	}
469		1225
		1226	BEGIN { AnyEvent::common_sense }
		1227
470	use Carp;	1228	use Carp ();
471		1229
472	our $VERSION = '3.3';	1230	our $VERSION = '6.01';
473	our $MODEL;	1231	our $MODEL;
474		1232
475	our $AUTOLOAD;
476	our @ISA;	1233	our @ISA;
477		1234
478	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
479
480	our @REGISTRY;	1235	our @REGISTRY;
481		1236
		1237	our $VERBOSE;
		1238
		1239	BEGIN {
		1240	require "AnyEvent/constants.pl";
		1241
		1242	eval "sub TAINT (){" . (${^TAINT}*1) . "}";
		1243
		1244	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1245	if ${^TAINT};
		1246
		1247	$ENV{"PERL_ANYEVENT_$_"} = $ENV{"AE_$_"}
		1248	for grep s/^AE_// && !exists $ENV{"PERL_ANYEVENT_$_"}, keys %ENV;
		1249
		1250	@ENV{grep /^PERL_ANYEVENT_/, keys %ENV} = ()
		1251	if ${^TAINT};
		1252
		1253	$VERBOSE = $ENV{PERL_ANYEVENT_VERBOSE}*1;
		1254	}
		1255
		1256	our $MAX_SIGNAL_LATENCY = 10;
		1257
		1258	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		1259
		1260	{
		1261	my $idx;
		1262	$PROTOCOL{$_} = ++$idx
		1263	for reverse split /\s*,\s*/,
		1264	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		1265	}
		1266
		1267	our @post_detect;
		1268
		1269	sub post_detect(&) {
		1270	my ($cb) = @_;
		1271
		1272	push @post_detect, $cb;
		1273
		1274	defined wantarray
		1275	? bless \$cb, "AnyEvent::Util::postdetect"
		1276	: ()
		1277	}
		1278
		1279	sub AnyEvent::Util::postdetect::DESTROY {
		1280	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		1281	}
		1282
		1283	our $POSTPONE_W;
		1284	our @POSTPONE;
		1285
		1286	sub _postpone_exec {
		1287	undef $POSTPONE_W;
		1288
		1289	&{ shift @POSTPONE }
		1290	while @POSTPONE;
		1291	}
		1292
		1293	sub postpone(&) {
		1294	push @POSTPONE, shift;
		1295
		1296	$POSTPONE_W ||= AE::timer (0, 0, \&_postpone_exec);
		1297
		1298	()
		1299	}
		1300
		1301	sub log($$;@) {
		1302	# only load the big bloated module when we actually are about to log something
		1303	if ($_[0] <= $VERBOSE) { # also catches non-numeric levels(!)
		1304	require AnyEvent::Log;
		1305	# AnyEvent::Log overwrites this function
		1306	goto &log;
		1307	}
		1308
		1309	0 # not logged
		1310	}
		1311
		1312	if (length $ENV{PERL_ANYEVENT_LOG}) {
		1313	require AnyEvent::Log; # AnyEvent::Log does the thing for us
		1314	}
		1315
482	my @models = (	1316	our @models = (
483	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
484	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
485	[EV:: => AnyEvent::Impl::EV::],	1317	[EV:: => AnyEvent::Impl::EV:: , 1],
		1318	[AnyEvent::Loop:: => AnyEvent::Impl::Perl:: , 1],
		1319	# everything below here will not (normally) be autoprobed
		1320	# as the pure perl backend should work everywhere
		1321	# and is usually faster
486	[Event:: => AnyEvent::Impl::Event::],	1322	[Event:: => AnyEvent::Impl::Event::, 1],
487	[Glib:: => AnyEvent::Impl::Glib::],	1323	[Glib:: => AnyEvent::Impl::Glib:: , 1], # becomes extremely slow with many watchers
		1324	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		1325	[Irssi:: => AnyEvent::Impl::Irssi::], # Irssi has a bogus "Event" package
488	[Tk:: => AnyEvent::Impl::Tk::],	1326	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		1327	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		1328	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
489	[Wx:: => AnyEvent::Impl::POE::],	1329	[Wx:: => AnyEvent::Impl::POE::],
490	[Prima:: => AnyEvent::Impl::POE::],	1330	[Prima:: => AnyEvent::Impl::POE::],
491	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1331	[IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # a bitch to autodetect
492	# everything below here will not be autoprobed as the pureperl backend should work everywhere	1332	[Cocoa::EventLoop:: => AnyEvent::Impl::Cocoa::],
493	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy	1333	[FLTK:: => AnyEvent::Impl::FLTK2::],
494	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
495	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
496	);	1334	);
497		1335
498	our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);	1336	our @isa_hook;
		1337
		1338	sub _isa_set {
		1339	my @pkg = ("AnyEvent", (map $_->[0], grep defined, @isa_hook), $MODEL);
		1340
		1341	@{"$pkg[$_-1]::ISA"} = $pkg[$_]
		1342	for 1 .. $#pkg;
		1343
		1344	grep $_ && $_->[1], @isa_hook
		1345	and AE::_reset ();
		1346	}
		1347
		1348	# used for hooking AnyEvent::Strict and AnyEvent::Debug::Wrap into the class hierarchy
		1349	sub _isa_hook($$;$) {
		1350	my ($i, $pkg, $reset_ae) = @_;
		1351
		1352	$isa_hook[$i] = $pkg ? [$pkg, $reset_ae] : undef;
		1353
		1354	_isa_set;
		1355	}
		1356
		1357	# all autoloaded methods reserve the complete glob, not just the method slot.
		1358	# due to bugs in perls method cache implementation.
		1359	our @methods = qw(io timer time now now_update signal child idle condvar);
499		1360
500	sub detect() {	1361	sub detect() {
		1362	return $MODEL if $MODEL; # some programs keep references to detect
		1363
		1364	local $!; # for good measure
		1365	local $SIG{__DIE__}; # we use eval
		1366
		1367	# free some memory
		1368	*detect = sub () { $MODEL };
		1369	# undef &func doesn't correctly update the method cache. grmbl.
		1370	# so we delete the whole glob. grmbl.
		1371	# otoh, perl doesn't let me undef an active usb, but it lets me free
		1372	# a glob with an active sub. hrm. i hope it works, but perl is
		1373	# usually buggy in this department. sigh.
		1374	delete @{"AnyEvent::"}{@methods};
		1375	undef @methods;
		1376
		1377	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z0-9:]+)$/) {
		1378	my $model = $1;
		1379	$model = "AnyEvent::Impl::$model" unless $model =~ s/::$//;
		1380	if (eval "require $model") {
		1381	AnyEvent::log 7 => "loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.";
		1382	$MODEL = $model;
		1383	} else {
		1384	AnyEvent::log 5 => "unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@";
		1385	}
		1386	}
		1387
		1388	# check for already loaded models
501	unless ($MODEL) {	1389	unless ($MODEL) {
502	no strict 'refs';	1390	for (@REGISTRY, @models) {
503		1391	my ($package, $model) = @$_;
504	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	1392	if (${"$package\::VERSION"} > 0) {
505	my $model = "AnyEvent::Impl::$1";
506	if (eval "require $model") {	1393	if (eval "require $model") {
		1394	AnyEvent::log 7 => "autodetected model '$model', using it.";
507	$MODEL = $model;	1395	$MODEL = $model;
508	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	1396	last;
509	} else {	1397	}
510	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;
511	}	1398	}
512	}	1399	}
513		1400
514	# check for already loaded models
515	unless ($MODEL) {	1401	unless ($MODEL) {
		1402	# try to autoload a model
516	for (@REGISTRY, @models) {	1403	for (@REGISTRY, @models) {
517	my ($package, $model) = @$_;	1404	my ($package, $model, $autoload) = @$_;
		1405	if (
		1406	$autoload
		1407	and eval "require $package"
518	if (${"$package\::VERSION"} > 0) {	1408	and ${"$package\::VERSION"} > 0
519	if (eval "require $model") {	1409	and eval "require $model"
		1410	) {
		1411	AnyEvent::log 7 => "autoloaded model '$model', using it.";
520	$MODEL = $model;	1412	$MODEL = $model;
521	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;
522	last;	1413	last;
523	}
524	}	1414	}
525	}	1415	}
526		1416
527	unless ($MODEL) {	1417	$MODEL
528	# try to load a model	1418	or die "AnyEvent: backend autodetection failed - did you properly install AnyEvent?";
		1419	}
		1420	}
529		1421
530	for (@REGISTRY, @models) {	1422	# free memory only needed for probing
531	my ($package, $model) = @$_;	1423	undef @models;
532	if (eval "require $package"	1424	undef @REGISTRY;
533	and ${"$package\::VERSION"} > 0	1425
534	and eval "require $model") {	1426	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
535	$MODEL = $model;	1427
536	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;	1428	# now nuke some methods that are overridden by the backend.
		1429	# SUPER usage is not allowed in these.
		1430	for (qw(time signal child idle)) {
		1431	undef &{"AnyEvent::Base::$_"}
		1432	if defined &{"$MODEL\::$_"};
		1433	}
		1434
		1435	_isa_set;
		1436
		1437	# we're officially open!
		1438
		1439	if ($ENV{PERL_ANYEVENT_STRICT}) {
		1440	require AnyEvent::Strict;
		1441	}
		1442
		1443	if ($ENV{PERL_ANYEVENT_DEBUG_WRAP}) {
		1444	require AnyEvent::Debug;
		1445	AnyEvent::Debug::wrap ($ENV{PERL_ANYEVENT_DEBUG_WRAP});
		1446	}
		1447
		1448	if (length $ENV{PERL_ANYEVENT_DEBUG_SHELL}) {
		1449	require AnyEvent::Socket;
		1450	require AnyEvent::Debug;
		1451
		1452	my $shell = $ENV{PERL_ANYEVENT_DEBUG_SHELL};
		1453	$shell =~ s/\$\$/$$/g;
		1454
		1455	my ($host, $service) = AnyEvent::Socket::parse_hostport ($shell);
		1456	$AnyEvent::Debug::SHELL = AnyEvent::Debug::shell ($host, $service);
		1457	}
		1458
		1459	# now the anyevent environment is set up as the user told us to, so
		1460	# call the actual user code - post detects
		1461
		1462	(shift @post_detect)->() while @post_detect;
		1463	undef @post_detect;
		1464
		1465	*post_detect = sub(&) {
		1466	shift->();
		1467
		1468	undef
		1469	};
		1470
		1471	$MODEL
		1472	}
		1473
		1474	for my $name (@methods) {
		1475	*$name = sub {
		1476	detect;
		1477	# we use goto because
		1478	# a) it makes the thunk more transparent
		1479	# b) it allows us to delete the thunk later
		1480	goto &{ UNIVERSAL::can AnyEvent => "SUPER::$name" }
		1481	};
		1482	}
		1483
		1484	# utility function to dup a filehandle. this is used by many backends
		1485	# to support binding more than one watcher per filehandle (they usually
		1486	# allow only one watcher per fd, so we dup it to get a different one).
		1487	sub _dupfh($$;$$) {
		1488	my ($poll, $fh, $r, $w) = @_;
		1489
		1490	# cygwin requires the fh mode to be matching, unix doesn't
		1491	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1492
		1493	open my $fh2, $mode, $fh
		1494	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1495
		1496	# we assume CLOEXEC is already set by perl in all important cases
		1497
		1498	($fh2, $rw)
		1499	}
		1500
		1501	=head1 SIMPLIFIED AE API
		1502
		1503	Starting with version 5.0, AnyEvent officially supports a second, much
		1504	simpler, API that is designed to reduce the calling, typing and memory
		1505	overhead by using function call syntax and a fixed number of parameters.
		1506
		1507	See the L<AE> manpage for details.
		1508
		1509	=cut
		1510
		1511	package AE;
		1512
		1513	our $VERSION = $AnyEvent::VERSION;
		1514
		1515	sub _reset() {
		1516	eval q{
		1517	# fall back to the main API by default - backends and AnyEvent::Base
		1518	# implementations can overwrite these.
		1519
		1520	sub io($$$) {
		1521	AnyEvent->io (fh => $_[0], poll => $_[1] ? "w" : "r", cb => $_[2])
		1522	}
		1523
		1524	sub timer($$$) {
		1525	AnyEvent->timer (after => $_[0], interval => $_[1], cb => $_[2])
		1526	}
		1527
		1528	sub signal($$) {
		1529	AnyEvent->signal (signal => $_[0], cb => $_[1])
		1530	}
		1531
		1532	sub child($$) {
		1533	AnyEvent->child (pid => $_[0], cb => $_[1])
		1534	}
		1535
		1536	sub idle($) {
		1537	AnyEvent->idle (cb => $_[0]);
		1538	}
		1539
		1540	sub cv(;&) {
		1541	AnyEvent->condvar (@_ ? (cb => $_[0]) : ())
		1542	}
		1543
		1544	sub now() {
		1545	AnyEvent->now
		1546	}
		1547
		1548	sub now_update() {
		1549	AnyEvent->now_update
		1550	}
		1551
		1552	sub time() {
		1553	AnyEvent->time
		1554	}
		1555
		1556	*postpone = \&AnyEvent::postpone;
		1557	*log = \&AnyEvent::log;
		1558	};
		1559	die if $@;
		1560	}
		1561
		1562	BEGIN { _reset }
		1563
		1564	package AnyEvent::Base;
		1565
		1566	# default implementations for many methods
		1567
		1568	sub time {
		1569	eval q{ # poor man's autoloading {}
		1570	# probe for availability of Time::HiRes
		1571	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1572	*time = sub { Time::HiRes::time () };
		1573	*AE::time = \& Time::HiRes::time ;
		1574	*now = \&time;
		1575	AnyEvent::log 8 => "AnyEvent: using Time::HiRes for sub-second timing accuracy.";
		1576	# if (eval "use POSIX (); (POSIX::times())...
		1577	} else {
		1578	*time = sub { CORE::time };
		1579	*AE::time = sub (){ CORE::time };
		1580	*now = \&time;
		1581	AnyEvent::log 3 => "using built-in time(), WARNING, no sub-second resolution!";
		1582	}
		1583	};
		1584	die if $@;
		1585
		1586	&time
		1587	}
		1588
		1589	*now = \&time;
		1590	sub now_update { }
		1591
		1592	sub _poll {
		1593	Carp::croak "$AnyEvent::MODEL does not support blocking waits. Caught";
		1594	}
		1595
		1596	# default implementation for ->condvar
		1597	# in fact, the default should not be overwritten
		1598
		1599	sub condvar {
		1600	eval q{ # poor man's autoloading {}
		1601	*condvar = sub {
		1602	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
		1603	};
		1604
		1605	*AE::cv = sub (;&) {
		1606	bless { @_ ? (_ae_cb => shift) : () }, "AnyEvent::CondVar"
		1607	};
		1608	};
		1609	die if $@;
		1610
		1611	&condvar
		1612	}
		1613
		1614	# default implementation for ->signal
		1615
		1616	our $HAVE_ASYNC_INTERRUPT;
		1617
		1618	sub _have_async_interrupt() {
		1619	$HAVE_ASYNC_INTERRUPT = 1*(!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT}
		1620	&& eval "use Async::Interrupt 1.02 (); 1")
		1621	unless defined $HAVE_ASYNC_INTERRUPT;
		1622
		1623	$HAVE_ASYNC_INTERRUPT
		1624	}
		1625
		1626	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1627	our (%SIG_ASY, %SIG_ASY_W);
		1628	our ($SIG_COUNT, $SIG_TW);
		1629
		1630	# install a dummy wakeup watcher to reduce signal catching latency
		1631	# used by Impls
		1632	sub _sig_add() {
		1633	unless ($SIG_COUNT++) {
		1634	# try to align timer on a full-second boundary, if possible
		1635	my $NOW = AE::now;
		1636
		1637	$SIG_TW = AE::timer
		1638	$MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1639	$MAX_SIGNAL_LATENCY,
		1640	sub { } # just for the PERL_ASYNC_CHECK
		1641	;
		1642	}
		1643	}
		1644
		1645	sub _sig_del {
		1646	undef $SIG_TW
		1647	unless --$SIG_COUNT;
		1648	}
		1649
		1650	our $_sig_name_init; $_sig_name_init = sub {
		1651	eval q{ # poor man's autoloading {}
		1652	undef $_sig_name_init;
		1653
		1654	if (_have_async_interrupt) {
		1655	*sig2num = \&Async::Interrupt::sig2num;
		1656	*sig2name = \&Async::Interrupt::sig2name;
		1657	} else {
		1658	require Config;
		1659
		1660	my %signame2num;
		1661	@signame2num{ split ' ', $Config::Config{sig_name} }
		1662	= split ' ', $Config::Config{sig_num};
		1663
		1664	my @signum2name;
		1665	@signum2name[values %signame2num] = keys %signame2num;
		1666
		1667	*sig2num = sub($) {
		1668	$_[0] > 0 ? shift : $signame2num{+shift}
		1669	};
		1670	*sig2name = sub ($) {
		1671	$_[0] > 0 ? $signum2name[+shift] : shift
		1672	};
		1673	}
		1674	};
		1675	die if $@;
		1676	};
		1677
		1678	sub sig2num ($) { &$_sig_name_init; &sig2num }
		1679	sub sig2name($) { &$_sig_name_init; &sig2name }
		1680
		1681	sub signal {
		1682	eval q{ # poor man's autoloading {}
		1683	# probe for availability of Async::Interrupt
		1684	if (_have_async_interrupt) {
		1685	AnyEvent::log 8 => "using Async::Interrupt for race-free signal handling.";
		1686
		1687	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1688	$SIG_IO = AE::io $SIGPIPE_R->fileno, 0, \&_signal_exec;
		1689
		1690	} else {
		1691	AnyEvent::log 8 => "using emulated perl signal handling with latency timer.";
		1692
		1693	if (AnyEvent::WIN32) {
		1694	require AnyEvent::Util;
		1695
		1696	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1697	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R, 1) if $SIGPIPE_R;
		1698	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W, 1) if $SIGPIPE_W; # just in case
		1699	} else {
		1700	pipe $SIGPIPE_R, $SIGPIPE_W;
		1701	fcntl $SIGPIPE_R, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_R;
		1702	fcntl $SIGPIPE_W, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_W; # just in case
		1703
		1704	# not strictly required, as $^F is normally 2, but let's make sure...
		1705	fcntl $SIGPIPE_R, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1706	fcntl $SIGPIPE_W, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1707	}
		1708
		1709	$SIGPIPE_R
		1710	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1711
		1712	$SIG_IO = AE::io $SIGPIPE_R, 0, \&_signal_exec;
		1713	}
		1714
		1715	*signal = $HAVE_ASYNC_INTERRUPT
		1716	? sub {
		1717	my (undef, %arg) = @_;
		1718
		1719	# async::interrupt
		1720	my $signal = sig2num $arg{signal};
		1721	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1722
		1723	$SIG_ASY{$signal} ||= new Async::Interrupt
		1724	cb => sub { undef $SIG_EV{$signal} },
		1725	signal => $signal,
		1726	pipe => [$SIGPIPE_R->filenos],
		1727	pipe_autodrain => 0,
		1728	;
		1729
		1730	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1731	}
		1732	: sub {
		1733	my (undef, %arg) = @_;
		1734
		1735	# pure perl
		1736	my $signal = sig2name $arg{signal};
		1737	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1738
		1739	$SIG{$signal} ||= sub {
537	last;	1740	local $!;
		1741	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1742	undef $SIG_EV{$signal};
538	}	1743	};
		1744
		1745	# can't do signal processing without introducing races in pure perl,
		1746	# so limit the signal latency.
		1747	_sig_add;
		1748
		1749	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1750	}
		1751	;
		1752
		1753	*AnyEvent::Base::signal::DESTROY = sub {
		1754	my ($signal, $cb) = @{$_[0]};
		1755
		1756	_sig_del;
		1757
		1758	delete $SIG_CB{$signal}{$cb};
		1759
		1760	$HAVE_ASYNC_INTERRUPT
		1761	? delete $SIG_ASY{$signal}
		1762	: # delete doesn't work with older perls - they then
		1763	# print weird messages, or just unconditionally exit
		1764	# instead of getting the default action.
		1765	undef $SIG{$signal}
		1766	unless keys %{ $SIG_CB{$signal} };
		1767	};
		1768
		1769	*_signal_exec = sub {
		1770	$HAVE_ASYNC_INTERRUPT
		1771	? $SIGPIPE_R->drain
		1772	: sysread $SIGPIPE_R, (my $dummy), 9;
		1773
		1774	while (%SIG_EV) {
		1775	for (keys %SIG_EV) {
		1776	delete $SIG_EV{$_};
		1777	&$_ for values %{ $SIG_CB{$_} || {} };
539	}	1778	}
540
541	$MODEL
542	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV (or Coro+EV), Event (or Coro+Event) or Glib.";
543	}	1779	}
544	}	1780	};
545
546	unshift @ISA, $MODEL;
547	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
548	}
549
550	$MODEL
551	}
552
553	sub AUTOLOAD {
554	(my $func = $AUTOLOAD) =~ s/.*://;
555
556	$method{$func}
557	or croak "$func: not a valid method for AnyEvent objects";
558
559	detect unless $MODEL;
560
561	my $class = shift;
562	$class->$func (@_);
563	}
564
565	package AnyEvent::Base;
566
567	# default implementation for ->condvar, ->wait, ->broadcast
568
569	sub condvar {
570	bless \my $flag, "AnyEvent::Base::CondVar"
571	}
572
573	sub AnyEvent::Base::CondVar::broadcast {
574	${$_[0]}++;
575	}
576
577	sub AnyEvent::Base::CondVar::wait {
578	AnyEvent->one_event while !${$_[0]};
579	}
580
581	# default implementation for ->signal
582
583	our %SIG_CB;
584
585	sub signal {
586	my (undef, %arg) = @_;
587
588	my $signal = uc $arg{signal}
589	or Carp::croak "required option 'signal' is missing";
590
591	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
592	$SIG{$signal} ||= sub {
593	$_->() for values %{ $SIG_CB{$signal} || {} };
594	};	1781	};
		1782	die if $@;
595		1783
596	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1784	&signal
597	}
598
599	sub AnyEvent::Base::Signal::DESTROY {
600	my ($signal, $cb) = @{$_[0]};
601
602	delete $SIG_CB{$signal}{$cb};
603
604	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };
605	}	1785	}
606		1786
607	# default implementation for ->child	1787	# default implementation for ->child
608		1788
609	our %PID_CB;	1789	our %PID_CB;
610	our $CHLD_W;	1790	our $CHLD_W;
611	our $CHLD_DELAY_W;	1791	our $CHLD_DELAY_W;
612	our $PID_IDLE;
613	our $WNOHANG;
614		1792
615	sub _child_wait {	1793	# used by many Impl's
616	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1794	sub _emit_childstatus($$) {
		1795	my (undef, $rpid, $rstatus) = @_;
		1796
		1797	$_->($rpid, $rstatus)
617	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1798	for values %{ $PID_CB{$rpid} || {} },
618	(values %{ $PID_CB{0} || {} });	1799	values %{ $PID_CB{0} || {} };
		1800	}
		1801
		1802	sub child {
		1803	eval q{ # poor man's autoloading {}
		1804	*_sigchld = sub {
		1805	my $pid;
		1806
		1807	AnyEvent->_emit_childstatus ($pid, $?)
		1808	while ($pid = waitpid -1, WNOHANG) > 0;
		1809	};
		1810
		1811	*child = sub {
		1812	my (undef, %arg) = @_;
		1813
		1814	my $pid = $arg{pid};
		1815	my $cb = $arg{cb};
		1816
		1817	$PID_CB{$pid}{$cb+0} = $cb;
		1818
		1819	unless ($CHLD_W) {
		1820	$CHLD_W = AE::signal CHLD => \&_sigchld;
		1821	# child could be a zombie already, so make at least one round
		1822	&_sigchld;
		1823	}
		1824
		1825	bless [$pid, $cb+0], "AnyEvent::Base::child"
		1826	};
		1827
		1828	*AnyEvent::Base::child::DESTROY = sub {
		1829	my ($pid, $icb) = @{$_[0]};
		1830
		1831	delete $PID_CB{$pid}{$icb};
		1832	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
		1833
		1834	undef $CHLD_W unless keys %PID_CB;
		1835	};
		1836	};
		1837	die if $@;
		1838
		1839	&child
		1840	}
		1841
		1842	# idle emulation is done by simply using a timer, regardless
		1843	# of whether the process is idle or not, and not letting
		1844	# the callback use more than 50% of the time.
		1845	sub idle {
		1846	eval q{ # poor man's autoloading {}
		1847	*idle = sub {
		1848	my (undef, %arg) = @_;
		1849
		1850	my ($cb, $w, $rcb) = $arg{cb};
		1851
		1852	$rcb = sub {
		1853	if ($cb) {
		1854	$w = AE::time;
		1855	&$cb;
		1856	$w = AE::time - $w;
		1857
		1858	# never use more then 50% of the time for the idle watcher,
		1859	# within some limits
		1860	$w = 0.0001 if $w < 0.0001;
		1861	$w = 5 if $w > 5;
		1862
		1863	$w = AE::timer $w, 0, $rcb;
		1864	} else {
		1865	# clean up...
		1866	undef $w;
		1867	undef $rcb;
		1868	}
		1869	};
		1870
		1871	$w = AE::timer 0.05, 0, $rcb;
		1872
		1873	bless \\$cb, "AnyEvent::Base::idle"
		1874	};
		1875
		1876	*AnyEvent::Base::idle::DESTROY = sub {
		1877	undef $${$_[0]};
		1878	};
		1879	};
		1880	die if $@;
		1881
		1882	&idle
		1883	}
		1884
		1885	package AnyEvent::CondVar;
		1886
		1887	our @ISA = AnyEvent::CondVar::Base::;
		1888
		1889	# only to be used for subclassing
		1890	sub new {
		1891	my $class = shift;
		1892	bless AnyEvent->condvar (@_), $class
		1893	}
		1894
		1895	package AnyEvent::CondVar::Base;
		1896
		1897	#use overload
		1898	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1899	# fallback => 1;
		1900
		1901	# save 300+ kilobytes by dirtily hardcoding overloading
		1902	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1903	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1904	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1905	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1906
		1907	our $WAITING;
		1908
		1909	sub _send {
		1910	# nop
		1911	}
		1912
		1913	sub _wait {
		1914	AnyEvent->_poll until $_[0]{_ae_sent};
		1915	}
		1916
		1917	sub send {
		1918	my $cv = shift;
		1919	$cv->{_ae_sent} = [@_];
		1920	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1921	$cv->_send;
		1922	}
		1923
		1924	sub croak {
		1925	$_[0]{_ae_croak} = $_[1];
		1926	$_[0]->send;
		1927	}
		1928
		1929	sub ready {
		1930	$_[0]{_ae_sent}
		1931	}
		1932
		1933	sub recv {
		1934	unless ($_[0]{_ae_sent}) {
		1935	$WAITING
		1936	and Carp::croak "AnyEvent::CondVar: recursive blocking wait attempted";
		1937
		1938	local $WAITING = 1;
		1939	$_[0]->_wait;
619	}	1940	}
620		1941
621	undef $PID_IDLE;	1942	$_[0]{_ae_croak}
622	}	1943	and Carp::croak $_[0]{_ae_croak};
623		1944
624	sub _sigchld {	1945	wantarray
625	# make sure we deliver these changes "synchronous" with the event loop.	1946	? @{ $_[0]{_ae_sent} }
626	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {	1947	: $_[0]{_ae_sent}[0]
627	undef $CHLD_DELAY_W;
628	&_child_wait;
629	});
630	}	1948	}
631		1949
632	sub child {	1950	sub cb {
633	my (undef, %arg) = @_;	1951	my $cv = shift;
634		1952
635	defined (my $pid = $arg{pid} + 0)	1953	@_
636	or Carp::croak "required option 'pid' is missing";	1954	and $cv->{_ae_cb} = shift
		1955	and $cv->{_ae_sent}
		1956	and (delete $cv->{_ae_cb})->($cv);
637		1957
638	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1958	$cv->{_ae_cb}
639
640	unless ($WNOHANG) {
641	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;
642	}
643
644	unless ($CHLD_W) {
645	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
646	# child could be a zombie already, so make at least one round
647	&_sigchld;
648	}
649
650	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"
651	}	1959	}
652		1960
653	sub AnyEvent::Base::Child::DESTROY {	1961	sub begin {
654	my ($pid, $cb) = @{$_[0]};	1962	++$_[0]{_ae_counter};
655		1963	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
656	delete $PID_CB{$pid}{$cb};
657	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
658
659	undef $CHLD_W unless keys %PID_CB;
660	}	1964	}
		1965
		1966	sub end {
		1967	return if --$_[0]{_ae_counter};
		1968	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		1969	}
		1970
		1971	# undocumented/compatibility with pre-3.4
		1972	*broadcast = \&send;
		1973	*wait = \&recv;
		1974
		1975	=head1 ERROR AND EXCEPTION HANDLING
		1976
		1977	In general, AnyEvent does not do any error handling - it relies on the
		1978	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1979	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1980	checking of all AnyEvent methods, however, which is highly useful during
		1981	development.
		1982
		1983	As for exception handling (i.e. runtime errors and exceptions thrown while
		1984	executing a callback), this is not only highly event-loop specific, but
		1985	also not in any way wrapped by this module, as this is the job of the main
		1986	program.
		1987
		1988	The pure perl event loop simply re-throws the exception (usually
		1989	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1990	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1991	so on.
		1992
		1993	=head1 ENVIRONMENT VARIABLES
		1994
		1995	AnyEvent supports a number of environment variables that tune the
		1996	runtime behaviour. They are usually evaluated when AnyEvent is
		1997	loaded, initialised, or a submodule that uses them is loaded. Many of
		1998	them also cause AnyEvent to load additional modules - for example,
		1999	C<PERL_ANYEVENT_DEBUG_WRAP> causes the L<AnyEvent::Debug> module to be
		2000	loaded.
		2001
		2002	All the environment variables documented here start with
		2003	C<PERL_ANYEVENT_>, which is what AnyEvent considers its own
		2004	namespace. Other modules are encouraged (but by no means required) to use
		2005	C<PERL_ANYEVENT_SUBMODULE> if they have registered the AnyEvent::Submodule
		2006	namespace on CPAN, for any submodule. For example, L<AnyEvent::HTTP> could
		2007	be expected to use C<PERL_ANYEVENT_HTTP_PROXY> (it should not access env
		2008	variables starting with C<AE_>, see below).
		2009
		2010	All variables can also be set via the C<AE_> prefix, that is, instead
		2011	of setting C<PERL_ANYEVENT_VERBOSE> you can also set C<AE_VERBOSE>. In
		2012	case there is a clash btween anyevent and another program that uses
		2013	C<AE_something> you can set the corresponding C<PERL_ANYEVENT_something>
		2014	variable to the empty string, as those variables take precedence.
		2015
		2016	When AnyEvent is first loaded, it copies all C<AE_xxx> env variables
		2017	to their C<PERL_ANYEVENT_xxx> counterpart unless that variable already
		2018	exists. If taint mode is on, then AnyEvent will remove I<all> environment
		2019	variables starting with C<PERL_ANYEVENT_> from C<%ENV> (or replace them
		2020	with C<undef> or the empty string, if the corresaponding C<AE_> variable
		2021	is set).
		2022
		2023	The exact algorithm is currently:
		2024
		2025	1. if taint mode enabled, delete all PERL_ANYEVENT_xyz variables from %ENV
		2026	2. copy over AE_xyz to PERL_ANYEVENT_xyz unless the latter alraedy exists
		2027	3. if taint mode enabled, set all PERL_ANYEVENT_xyz variables to undef.
		2028
		2029	This ensures that child processes will not see the C<AE_> variables.
		2030
		2031	The following environment variables are currently known to AnyEvent:
		2032
		2033	=over 4
		2034
		2035	=item C<PERL_ANYEVENT_VERBOSE>
		2036
		2037	By default, AnyEvent will be completely silent except in fatal
		2038	conditions. You can set this environment variable to make AnyEvent more
		2039	talkative. If you want to do more than just set the global logging level
		2040	you should have a look at C<PERL_ANYEVENT_LOG>, which allows much more
		2041	complex specifications.
		2042
		2043	When set to C<5> or higher (warn), causes AnyEvent to warn about unexpected
		2044	conditions, such as not being able to load the event model specified by
		2045	C<PERL_ANYEVENT_MODEL>, or a guard callback throwing an exception - this
		2046	is the minimum recommended level.
		2047
		2048	When set to C<7> or higher (info), cause AnyEvent to report which event model it
		2049	chooses.
		2050
		2051	When set to C<8> or higher (debug), then AnyEvent will report extra information on
		2052	which optional modules it loads and how it implements certain features.
		2053
		2054	=item C<PERL_ANYEVENT_LOG>
		2055
		2056	Accepts rather complex logging specifications. For example, you could log
		2057	all C<debug> messages of some module to stderr, warnings and above to
		2058	stderr, and errors and above to syslog, with:
		2059
		2060	PERL_ANYEVENT_LOG=Some::Module=debug,+log:filter=warn,+%syslog:%syslog=error,syslog
		2061
		2062	For the rather extensive details, see L<AnyEvent::Log>.
		2063
		2064	This variable is evaluated when AnyEvent (or L<AnyEvent::Log>) is loaded,
		2065	so will take effect even before AnyEvent has initialised itself.
		2066
		2067	Note that specifying this environment variable causes the L<AnyEvent::Log>
		2068	module to be loaded, while C<PERL_ANYEVENT_VERBOSE> does not, so only
		2069	using the latter saves a few hundred kB of memory until the first message
		2070	is being logged.
		2071
		2072	=item C<PERL_ANYEVENT_STRICT>
		2073
		2074	AnyEvent does not do much argument checking by default, as thorough
		2075	argument checking is very costly. Setting this variable to a true value
		2076	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		2077	check the arguments passed to most method calls. If it finds any problems,
		2078	it will croak.
		2079
		2080	In other words, enables "strict" mode.
		2081
		2082	Unlike C<use strict> (or its modern cousin, C<< use L<common::sense>
		2083	>>, it is definitely recommended to keep it off in production. Keeping
		2084	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		2085	can be very useful, however.
		2086
		2087	=item C<PERL_ANYEVENT_DEBUG_SHELL>
		2088
		2089	If this env variable is set, then its contents will be interpreted by
		2090	C<AnyEvent::Socket::parse_hostport> (after replacing every occurance of
		2091	C<$$> by the process pid) and an C<AnyEvent::Debug::shell> is bound on
		2092	that port. The shell object is saved in C<$AnyEvent::Debug::SHELL>.
		2093
		2094	This happens when the first watcher is created.
		2095
		2096	For example, to bind a debug shell on a unix domain socket in
		2097	F<< /tmp/debug<pid>.sock >>, you could use this:
		2098
		2099	PERL_ANYEVENT_DEBUG_SHELL=/tmp/debug\$\$.sock perlprog
		2100
		2101	Note that creating sockets in F</tmp> is very unsafe on multiuser
		2102	systems.
		2103
		2104	=item C<PERL_ANYEVENT_DEBUG_WRAP>
		2105
		2106	Can be set to C<0>, C<1> or C<2> and enables wrapping of all watchers for
		2107	debugging purposes. See C<AnyEvent::Debug::wrap> for details.
		2108
		2109	=item C<PERL_ANYEVENT_MODEL>
		2110
		2111	This can be used to specify the event model to be used by AnyEvent, before
		2112	auto detection and -probing kicks in.
		2113
		2114	It normally is a string consisting entirely of ASCII letters (e.g. C<EV>
		2115	or C<IOAsync>). The string C<AnyEvent::Impl::> gets prepended and the
		2116	resulting module name is loaded and - if the load was successful - used as
		2117	event model backend. If it fails to load then AnyEvent will proceed with
		2118	auto detection and -probing.
		2119
		2120	If the string ends with C<::> instead (e.g. C<AnyEvent::Impl::EV::>) then
		2121	nothing gets prepended and the module name is used as-is (hint: C<::> at
		2122	the end of a string designates a module name and quotes it appropriately).
		2123
		2124	For example, to force the pure perl model (L<AnyEvent::Loop::Perl>) you
		2125	could start your program like this:
		2126
		2127	PERL_ANYEVENT_MODEL=Perl perl ...
		2128
		2129	=item C<PERL_ANYEVENT_PROTOCOLS>
		2130
		2131	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		2132	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		2133	of auto probing).
		2134
		2135	Must be set to a comma-separated list of protocols or address families,
		2136	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		2137	used, and preference will be given to protocols mentioned earlier in the
		2138	list.
		2139
		2140	This variable can effectively be used for denial-of-service attacks
		2141	against local programs (e.g. when setuid), although the impact is likely
		2142	small, as the program has to handle conenction and other failures anyways.
		2143
		2144	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		2145	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		2146	- only support IPv4, never try to resolve or contact IPv6
		2147	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		2148	IPv6, but prefer IPv6 over IPv4.
		2149
		2150	=item C<PERL_ANYEVENT_HOSTS>
		2151
		2152	This variable, if specified, overrides the F</etc/hosts> file used by
		2153	L<AnyEvent::Socket>C<::resolve_sockaddr>, i.e. hosts aliases will be read
		2154	from that file instead.
		2155
		2156	=item C<PERL_ANYEVENT_EDNS0>
		2157
		2158	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension for
		2159	DNS. This extension is generally useful to reduce DNS traffic, especially
		2160	when DNSSEC is involved, but some (broken) firewalls drop such DNS
		2161	packets, which is why it is off by default.
		2162
		2163	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		2164	EDNS0 in its DNS requests.
		2165
		2166	=item C<PERL_ANYEVENT_MAX_FORKS>
		2167
		2168	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		2169	will create in parallel.
		2170
		2171	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		2172
		2173	The default value for the C<max_outstanding> parameter for the default DNS
		2174	resolver - this is the maximum number of parallel DNS requests that are
		2175	sent to the DNS server.
		2176
		2177	=item C<PERL_ANYEVENT_RESOLV_CONF>
		2178
		2179	The absolute path to a F<resolv.conf>-style file to use instead of
		2180	F</etc/resolv.conf> (or the OS-specific configuration) in the default
		2181	resolver, or the empty string to select the default configuration.
		2182
		2183	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		2184
		2185	When neither C<ca_file> nor C<ca_path> was specified during
		2186	L<AnyEvent::TLS> context creation, and either of these environment
		2187	variables are nonempty, they will be used to specify CA certificate
		2188	locations instead of a system-dependent default.
		2189
		2190	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		2191
		2192	When these are set to C<1>, then the respective modules are not
		2193	loaded. Mostly good for testing AnyEvent itself.
		2194
		2195	=back
661		2196
662	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	2197	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
663		2198
664	This is an advanced topic that you do not normally need to use AnyEvent in	2199	This is an advanced topic that you do not normally need to use AnyEvent in
665	a module. This section is only of use to event loop authors who want to	2200	a module. This section is only of use to event loop authors who want to
…		…
699		2234
700	I<rxvt-unicode> also cheats a bit by not providing blocking access to	2235	I<rxvt-unicode> also cheats a bit by not providing blocking access to
701	condition variables: code blocking while waiting for a condition will	2236	condition variables: code blocking while waiting for a condition will
702	C<die>. This still works with most modules/usages, and blocking calls must	2237	C<die>. This still works with most modules/usages, and blocking calls must
703	not be done in an interactive application, so it makes sense.	2238	not be done in an interactive application, so it makes sense.
704
705	=head1 ENVIRONMENT VARIABLES
706
707	The following environment variables are used by this module:
708
709	=over 4
710
711	=item C<PERL_ANYEVENT_VERBOSE>
712
713	By default, AnyEvent will be completely silent except in fatal
714	conditions. You can set this environment variable to make AnyEvent more
715	talkative.
716
717	When set to C<1> or higher, causes AnyEvent to warn about unexpected
718	conditions, such as not being able to load the event model specified by
719	C<PERL_ANYEVENT_MODEL>.
720
721	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
722	model it chooses.
723
724	=item C<PERL_ANYEVENT_MODEL>
725
726	This can be used to specify the event model to be used by AnyEvent, before
727	autodetection and -probing kicks in. It must be a string consisting
728	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
729	and the resulting module name is loaded and if the load was successful,
730	used as event model. If it fails to load AnyEvent will proceed with
731	autodetection and -probing.
732
733	This functionality might change in future versions.
734
735	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
736	could start your program like this:
737
738	PERL_ANYEVENT_MODEL=Perl perl ...
739
740	=back
741		2239
742	=head1 EXAMPLE PROGRAM	2240	=head1 EXAMPLE PROGRAM
743		2241
744	The following program uses an I/O watcher to read data from STDIN, a timer	2242	The following program uses an I/O watcher to read data from STDIN, a timer
745	to display a message once per second, and a condition variable to quit the	2243	to display a message once per second, and a condition variable to quit the
…		…
754	poll => 'r',	2252	poll => 'r',
755	cb => sub {	2253	cb => sub {
756	warn "io event <$_[0]>\n"; # will always output <r>	2254	warn "io event <$_[0]>\n"; # will always output <r>
757	chomp (my $input = <STDIN>); # read a line	2255	chomp (my $input = <STDIN>); # read a line
758	warn "read: $input\n"; # output what has been read	2256	warn "read: $input\n"; # output what has been read
759	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	2257	$cv->send if $input =~ /^q/i; # quit program if /^q/i
760	},	2258	},
761	);	2259	);
762		2260
763	my $time_watcher; # can only be used once
764
765	sub new_timer {
766	$timer = AnyEvent->timer (after => 1, cb => sub {	2261	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
767	warn "timeout\n"; # print 'timeout' about every second	2262	warn "timeout\n"; # print 'timeout' at most every second
768	&new_timer; # and restart the time
769	});	2263	});
770	}
771		2264
772	new_timer; # create first timer
773
774	$cv->wait; # wait until user enters /^q/i	2265	$cv->recv; # wait until user enters /^q/i
775		2266
776	=head1 REAL-WORLD EXAMPLE	2267	=head1 REAL-WORLD EXAMPLE
777		2268
778	Consider the L<Net::FCP> module. It features (among others) the following	2269	Consider the L<Net::FCP> module. It features (among others) the following
779	API calls, which are to freenet what HTTP GET requests are to http:	2270	API calls, which are to freenet what HTTP GET requests are to http:
…		…
829	syswrite $txn->{fh}, $txn->{request}	2320	syswrite $txn->{fh}, $txn->{request}
830	or die "connection or write error";	2321	or die "connection or write error";
831	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	2322	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
832		2323
833	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	2324	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
834	result and signals any possible waiters that the request ahs finished:	2325	result and signals any possible waiters that the request has finished:
835		2326
836	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	2327	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
837		2328
838	if (end-of-file or data complete) {	2329	if (end-of-file or data complete) {
839	$txn->{result} = $txn->{buf};	2330	$txn->{result} = $txn->{buf};
840	$txn->{finished}->broadcast;	2331	$txn->{finished}->send;
841	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	2332	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
842	}	2333	}
843		2334
844	The C<result> method, finally, just waits for the finished signal (if the	2335	The C<result> method, finally, just waits for the finished signal (if the
845	request was already finished, it doesn't wait, of course, and returns the	2336	request was already finished, it doesn't wait, of course, and returns the
846	data:	2337	data:
847		2338
848	$txn->{finished}->wait;	2339	$txn->{finished}->recv;
849	return $txn->{result};	2340	return $txn->{result};
850		2341
851	The actual code goes further and collects all errors (C<die>s, exceptions)	2342	The actual code goes further and collects all errors (C<die>s, exceptions)
852	that occured during request processing. The C<result> method detects	2343	that occurred during request processing. The C<result> method detects
853	whether an exception as thrown (it is stored inside the $txn object)	2344	whether an exception as thrown (it is stored inside the $txn object)
854	and just throws the exception, which means connection errors and other	2345	and just throws the exception, which means connection errors and other
855	problems get reported tot he code that tries to use the result, not in a	2346	problems get reported to the code that tries to use the result, not in a
856	random callback.	2347	random callback.
857		2348
858	All of this enables the following usage styles:	2349	All of this enables the following usage styles:
859		2350
860	1. Blocking:	2351	1. Blocking:
…		…
888		2379
889	my $quit = AnyEvent->condvar;	2380	my $quit = AnyEvent->condvar;
890		2381
891	$fcp->txn_client_get ($url)->cb (sub {	2382	$fcp->txn_client_get ($url)->cb (sub {
892	...	2383	...
893	$quit->broadcast;	2384	$quit->send;
894	});	2385	});
895		2386
896	$quit->wait;	2387	$quit->recv;
897		2388
898		2389
899	=head1 BENCHMARKS	2390	=head1 BENCHMARKS
900		2391
901	To give you an idea of the performance and overheads that AnyEvent adds	2392	To give you an idea of the performance and overheads that AnyEvent adds
…		…
903	of various event loops I prepared some benchmarks.	2394	of various event loops I prepared some benchmarks.
904		2395
905	=head2 BENCHMARKING ANYEVENT OVERHEAD	2396	=head2 BENCHMARKING ANYEVENT OVERHEAD
906		2397
907	Here is a benchmark of various supported event models used natively and	2398	Here is a benchmark of various supported event models used natively and
908	through anyevent. The benchmark creates a lot of timers (with a zero	2399	through AnyEvent. The benchmark creates a lot of timers (with a zero
909	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,	2400	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
910	which it is), lets them fire exactly once and destroys them again.	2401	which it is), lets them fire exactly once and destroys them again.
911		2402
912	Source code for this benchmark is found as F<eg/bench> in the AnyEvent	2403	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
913	distribution.	2404	distribution. It uses the L<AE> interface, which makes a real difference
		2405	for the EV and Perl backends only.
914		2406
915	=head3 Explanation of the columns	2407	=head3 Explanation of the columns
916		2408
917	I<watcher> is the number of event watchers created/destroyed. Since	2409	I<watcher> is the number of event watchers created/destroyed. Since
918	different event models feature vastly different performances, each event	2410	different event models feature vastly different performances, each event
…		…
930	all watchers, to avoid adding memory overhead. That means closure creation	2422	all watchers, to avoid adding memory overhead. That means closure creation
931	and memory usage is not included in the figures.	2423	and memory usage is not included in the figures.
932		2424
933	I<invoke> is the time, in microseconds, used to invoke a simple	2425	I<invoke> is the time, in microseconds, used to invoke a simple
934	callback. The callback simply counts down a Perl variable and after it was	2426	callback. The callback simply counts down a Perl variable and after it was
935	invoked "watcher" times, it would C<< ->broadcast >> a condvar once to	2427	invoked "watcher" times, it would C<< ->send >> a condvar once to
936	signal the end of this phase.	2428	signal the end of this phase.
937		2429
938	I<destroy> is the time, in microseconds, that it takes to destroy a single	2430	I<destroy> is the time, in microseconds, that it takes to destroy a single
939	watcher.	2431	watcher.
940		2432
941	=head3 Results	2433	=head3 Results
942		2434
943	name watchers bytes create invoke destroy comment	2435	name watchers bytes create invoke destroy comment
944	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	2436	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
945	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	2437	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
946	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	2438	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
947	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	2439	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
948	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	2440	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
949	Event/Any 16000 936 39.17 33.63 1.43 Event + AnyEvent watchers	2441	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
		2442	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
		2443	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
950	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	2444	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
951	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	2445	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
952	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	2446	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
953	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	2447	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
954		2448
955	=head3 Discussion	2449	=head3 Discussion
956		2450
957	The benchmark does I<not> measure scalability of the event loop very	2451	The benchmark does I<not> measure scalability of the event loop very
958	well. For example, a select-based event loop (such as the pure perl one)	2452	well. For example, a select-based event loop (such as the pure perl one)
…		…
964	Also, note that the number of watchers usually has a nonlinear effect on	2458	Also, note that the number of watchers usually has a nonlinear effect on
965	overall speed, that is, creating twice as many watchers doesn't take twice	2459	overall speed, that is, creating twice as many watchers doesn't take twice
966	the time - usually it takes longer. This puts event loops tested with a	2460	the time - usually it takes longer. This puts event loops tested with a
967	higher number of watchers at a disadvantage.	2461	higher number of watchers at a disadvantage.
968		2462
		2463	To put the range of results into perspective, consider that on the
		2464	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		2465	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		2466	cycles with POE.
		2467
969	C<EV> is the sole leader regarding speed and memory use, which are both	2468	C<EV> is the sole leader regarding speed and memory use, which are both
970	maximal/minimal, respectively. Even when going through AnyEvent, it uses	2469	maximal/minimal, respectively. When using the L<AE> API there is zero
		2470	overhead (when going through the AnyEvent API create is about 5-6 times
		2471	slower, with other times being equal, so still uses far less memory than
971	far less memory than any other event loop and is still faster than Event	2472	any other event loop and is still faster than Event natively).
972	natively.
973		2473
974	The pure perl implementation is hit in a few sweet spots (both the	2474	The pure perl implementation is hit in a few sweet spots (both the
975	constant timeout and the use of a single fd hit optimisations in the perl	2475	constant timeout and the use of a single fd hit optimisations in the perl
976	interpreter and the backend itself). Nevertheless this shows that it	2476	interpreter and the backend itself). Nevertheless this shows that it
977	adds very little overhead in itself. Like any select-based backend its	2477	adds very little overhead in itself. Like any select-based backend its
978	performance becomes really bad with lots of file descriptors (and few of	2478	performance becomes really bad with lots of file descriptors (and few of
979	them active), of course, but this was not subject of this benchmark.	2479	them active), of course, but this was not subject of this benchmark.
980		2480
981	The C<Event> module has a relatively high setup and callback invocation	2481	The C<Event> module has a relatively high setup and callback invocation
982	cost, but overall scores in on the third place.	2482	cost, but overall scores in on the third place.
		2483
		2484	C<IO::Async> performs admirably well, about on par with C<Event>, even
		2485	when using its pure perl backend.
983		2486
984	C<Glib>'s memory usage is quite a bit higher, but it features a	2487	C<Glib>'s memory usage is quite a bit higher, but it features a
985	faster callback invocation and overall ends up in the same class as	2488	faster callback invocation and overall ends up in the same class as
986	C<Event>. However, Glib scales extremely badly, doubling the number of	2489	C<Event>. However, Glib scales extremely badly, doubling the number of
987	watchers increases the processing time by more than a factor of four,	2490	watchers increases the processing time by more than a factor of four,
…		…
995	file descriptor is dup()ed for each watcher. This shows that the dup()	2498	file descriptor is dup()ed for each watcher. This shows that the dup()
996	employed by some adaptors is not a big performance issue (it does incur a	2499	employed by some adaptors is not a big performance issue (it does incur a
997	hidden memory cost inside the kernel which is not reflected in the figures	2500	hidden memory cost inside the kernel which is not reflected in the figures
998	above).	2501	above).
999		2502
1000	C<POE>, regardless of underlying event loop (whether using its pure	2503	C<POE>, regardless of underlying event loop (whether using its pure perl
1001	perl select-based backend or the Event module, the POE-EV backend	2504	select-based backend or the Event module, the POE-EV backend couldn't
1002	couldn't be tested because it wasn't working) shows abysmal performance	2505	be tested because it wasn't working) shows abysmal performance and
1003	and memory usage: Watchers use almost 30 times as much memory as	2506	memory usage with AnyEvent: Watchers use almost 30 times as much memory
1004	EV watchers, and 10 times as much memory as Event (the high memory	2507	as EV watchers, and 10 times as much memory as Event (the high memory
1005	requirements are caused by requiring a session for each watcher). Watcher	2508	requirements are caused by requiring a session for each watcher). Watcher
1006	invocation speed is almost 900 times slower than with AnyEvent's pure perl	2509	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		2510	implementation.
		2511
1007	implementation. The design of the POE adaptor class in AnyEvent can not	2512	The design of the POE adaptor class in AnyEvent can not really account
1008	really account for this, as session creation overhead is small compared	2513	for the performance issues, though, as session creation overhead is
1009	to execution of the state machine, which is coded pretty optimally within	2514	small compared to execution of the state machine, which is coded pretty
1010	L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow.	2515	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		2516	using multiple sessions is not a good approach, especially regarding
		2517	memory usage, even the author of POE could not come up with a faster
		2518	design).
1011		2519
1012	=head3 Summary	2520	=head3 Summary
1013		2521
1014	=over 4	2522	=over 4
1015		2523
…		…
1017	(even when used without AnyEvent), but most event loops have acceptable	2525	(even when used without AnyEvent), but most event loops have acceptable
1018	performance with or without AnyEvent.	2526	performance with or without AnyEvent.
1019		2527
1020	=item * The overhead AnyEvent adds is usually much smaller than the overhead of	2528	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
1021	the actual event loop, only with extremely fast event loops such as EV	2529	the actual event loop, only with extremely fast event loops such as EV
1022	adds AnyEvent significant overhead.	2530	does AnyEvent add significant overhead.
1023		2531
1024	=item * You should avoid POE like the plague if you want performance or	2532	=item * You should avoid POE like the plague if you want performance or
1025	reasonable memory usage.	2533	reasonable memory usage.
1026		2534
1027	=back	2535	=back
1028		2536
1029	=head2 BENCHMARKING THE LARGE SERVER CASE	2537	=head2 BENCHMARKING THE LARGE SERVER CASE
1030		2538
1031	This benchmark atcually benchmarks the event loop itself. It works by	2539	This benchmark actually benchmarks the event loop itself. It works by
1032	creating a number of "servers": each server consists of a socketpair, a	2540	creating a number of "servers": each server consists of a socket pair, a
1033	timeout watcher that gets reset on activity (but never fires), and an I/O	2541	timeout watcher that gets reset on activity (but never fires), and an I/O
1034	watcher waiting for input on one side of the socket. Each time the socket	2542	watcher waiting for input on one side of the socket. Each time the socket
1035	watcher reads a byte it will write that byte to a random other "server".	2543	watcher reads a byte it will write that byte to a random other "server".
1036		2544
1037	The effect is that there will be a lot of I/O watchers, only part of which	2545	The effect is that there will be a lot of I/O watchers, only part of which
1038	are active at any one point (so there is a constant number of active	2546	are active at any one point (so there is a constant number of active
1039	fds for each loop iterstaion, but which fds these are is random). The	2547	fds for each loop iteration, but which fds these are is random). The
1040	timeout is reset each time something is read because that reflects how	2548	timeout is reset each time something is read because that reflects how
1041	most timeouts work (and puts extra pressure on the event loops).	2549	most timeouts work (and puts extra pressure on the event loops).
1042		2550
1043	In this benchmark, we use 10000 socketpairs (20000 sockets), of which 100	2551	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
1044	(1%) are active. This mirrors the activity of large servers with many	2552	(1%) are active. This mirrors the activity of large servers with many
1045	connections, most of which are idle at any one point in time.	2553	connections, most of which are idle at any one point in time.
1046		2554
1047	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent	2555	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
1048	distribution.	2556	distribution. It uses the L<AE> interface, which makes a real difference
		2557	for the EV and Perl backends only.
1049		2558
1050	=head3 Explanation of the columns	2559	=head3 Explanation of the columns
1051		2560
1052	I<sockets> is the number of sockets, and twice the number of "servers" (as	2561	I<sockets> is the number of sockets, and twice the number of "servers" (as
1053	each server has a read and write socket end).	2562	each server has a read and write socket end).
1054		2563
1055	I<create> is the time it takes to create a socketpair (which is	2564	I<create> is the time it takes to create a socket pair (which is
1056	nontrivial) and two watchers: an I/O watcher and a timeout watcher.	2565	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
1057		2566
1058	I<request>, the most important value, is the time it takes to handle a	2567	I<request>, the most important value, is the time it takes to handle a
1059	single "request", that is, reading the token from the pipe and forwarding	2568	single "request", that is, reading the token from the pipe and forwarding
1060	it to another server. This includes deleting the old timeout and creating	2569	it to another server. This includes deleting the old timeout and creating
1061	a new one that moves the timeout into the future.	2570	a new one that moves the timeout into the future.
1062		2571
1063	=head3 Results	2572	=head3 Results
1064		2573
1065	name sockets create request	2574	name sockets create request
1066	EV 20000 69.01 11.16	2575	EV 20000 62.66 7.99
1067	Perl 20000 75.28 112.76	2576	Perl 20000 68.32 32.64
1068	Event 20000 212.62 257.32	2577	IOAsync 20000 174.06 101.15 epoll
1069	Glib 20000 651.16 1896.30	2578	IOAsync 20000 174.67 610.84 poll
		2579	Event 20000 202.69 242.91
		2580	Glib 20000 557.01 1689.52
1070	POE 20000 349.67 12317.24 uses POE::Loop::Event	2581	POE 20000 341.54 12086.32 uses POE::Loop::Event
1071		2582
1072	=head3 Discussion	2583	=head3 Discussion
1073		2584
1074	This benchmark I<does> measure scalability and overall performance of the	2585	This benchmark I<does> measure scalability and overall performance of the
1075	particular event loop.	2586	particular event loop.
…		…
1077	EV is again fastest. Since it is using epoll on my system, the setup time	2588	EV is again fastest. Since it is using epoll on my system, the setup time
1078	is relatively high, though.	2589	is relatively high, though.
1079		2590
1080	Perl surprisingly comes second. It is much faster than the C-based event	2591	Perl surprisingly comes second. It is much faster than the C-based event
1081	loops Event and Glib.	2592	loops Event and Glib.
		2593
		2594	IO::Async performs very well when using its epoll backend, and still quite
		2595	good compared to Glib when using its pure perl backend.
1082		2596
1083	Event suffers from high setup time as well (look at its code and you will	2597	Event suffers from high setup time as well (look at its code and you will
1084	understand why). Callback invocation also has a high overhead compared to	2598	understand why). Callback invocation also has a high overhead compared to
1085	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event	2599	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
1086	uses select or poll in basically all documented configurations.	2600	uses select or poll in basically all documented configurations.
…		…
1094		2608
1095	=head3 Summary	2609	=head3 Summary
1096		2610
1097	=over 4	2611	=over 4
1098		2612
1099	=item * The pure perl implementation performs extremely well, considering	2613	=item * The pure perl implementation performs extremely well.
1100	that it uses select.
1101		2614
1102	=item * Avoid Glib or POE in large projects where performance matters.	2615	=item * Avoid Glib or POE in large projects where performance matters.
1103		2616
1104	=back	2617	=back
1105		2618
…		…
1118		2631
1119	=head3 Results	2632	=head3 Results
1120		2633
1121	name sockets create request	2634	name sockets create request
1122	EV 16 20.00 6.54	2635	EV 16 20.00 6.54
		2636	Perl 16 25.75 12.62
1123	Event 16 81.27 35.86	2637	Event 16 81.27 35.86
1124	Glib 16 32.63 15.48	2638	Glib 16 32.63 15.48
1125	Perl 16 24.62 162.37
1126	POE 16 261.87 276.28 uses POE::Loop::Event	2639	POE 16 261.87 276.28 uses POE::Loop::Event
1127		2640
1128	=head3 Discussion	2641	=head3 Discussion
1129		2642
1130	The benchmark tries to test the performance of a typical small	2643	The benchmark tries to test the performance of a typical small
1131	server. While knowing how various event loops perform is interesting, keep	2644	server. While knowing how various event loops perform is interesting, keep
1132	in mind that their overhead in this case is usually not as important, due	2645	in mind that their overhead in this case is usually not as important, due
1133	to the small absolute number of watchers.	2646	to the small absolute number of watchers (that is, you need efficiency and
		2647	speed most when you have lots of watchers, not when you only have a few of
		2648	them).
1134		2649
1135	EV is again fastest.	2650	EV is again fastest.
1136		2651
1137	The C-based event loops Event and Glib come in second this time, as the	2652	Perl again comes second. It is noticeably faster than the C-based event
1138	overhead of running an iteration is much smaller in C than in Perl (little	2653	loops Event and Glib, although the difference is too small to really
1139	code to execute in the inner loop, and perl's function calling overhead is	2654	matter.
1140	high, and updating all the data structures is costly).
1141		2655
1142	The pure perl event loop is much slower, but still competitive.
1143
1144	POE also performs much better in this case, but is is stillf ar behind the	2656	POE also performs much better in this case, but is is still far behind the
1145	others.	2657	others.
1146		2658
1147	=head3 Summary	2659	=head3 Summary
1148		2660
1149	=over 4	2661	=over 4
…		…
1151	=item * C-based event loops perform very well with small number of	2663	=item * C-based event loops perform very well with small number of
1152	watchers, as the management overhead dominates.	2664	watchers, as the management overhead dominates.
1153		2665
1154	=back	2666	=back
1155		2667
		2668	=head2 THE IO::Lambda BENCHMARK
		2669
		2670	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2671	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2672	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2673	shouldn't come as a surprise to anybody). As such, the benchmark is
		2674	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2675	very optimal. But how would AnyEvent compare when used without the extra
		2676	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2677
		2678	The benchmark itself creates an echo-server, and then, for 500 times,
		2679	connects to the echo server, sends a line, waits for the reply, and then
		2680	creates the next connection. This is a rather bad benchmark, as it doesn't
		2681	test the efficiency of the framework or much non-blocking I/O, but it is a
		2682	benchmark nevertheless.
		2683
		2684	name runtime
		2685	Lambda/select 0.330 sec
		2686	+ optimized 0.122 sec
		2687	Lambda/AnyEvent 0.327 sec
		2688	+ optimized 0.138 sec
		2689	Raw sockets/select 0.077 sec
		2690	POE/select, components 0.662 sec
		2691	POE/select, raw sockets 0.226 sec
		2692	POE/select, optimized 0.404 sec
		2693
		2694	AnyEvent/select/nb 0.085 sec
		2695	AnyEvent/EV/nb 0.068 sec
		2696	+state machine 0.134 sec
		2697
		2698	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2699	benchmarks actually make blocking connects and use 100% blocking I/O,
		2700	defeating the purpose of an event-based solution. All of the newly
		2701	written AnyEvent benchmarks use 100% non-blocking connects (using
		2702	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2703	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2704	generally require a lot more bookkeeping and event handling than blocking
		2705	connects (which involve a single syscall only).
		2706
		2707	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2708	offers similar expressive power as POE and IO::Lambda, using conventional
		2709	Perl syntax. This means that both the echo server and the client are 100%
		2710	non-blocking, further placing it at a disadvantage.
		2711
		2712	As you can see, the AnyEvent + EV combination even beats the
		2713	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2714	backend easily beats IO::Lambda and POE.
		2715
		2716	And even the 100% non-blocking version written using the high-level (and
		2717	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda
		2718	higher level ("unoptimised") abstractions by a large margin, even though
		2719	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
		2720
		2721	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2722	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2723	part of the IO::Lambda distribution and were used without any changes.
		2724
		2725
		2726	=head1 SIGNALS
		2727
		2728	AnyEvent currently installs handlers for these signals:
		2729
		2730	=over 4
		2731
		2732	=item SIGCHLD
		2733
		2734	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2735	emulation for event loops that do not support them natively. Also, some
		2736	event loops install a similar handler.
		2737
		2738	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2739	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2740
		2741	=item SIGPIPE
		2742
		2743	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2744	when AnyEvent gets loaded.
		2745
		2746	The rationale for this is that AnyEvent users usually do not really depend
		2747	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2748	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2749	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2750	some random socket.
		2751
		2752	The rationale for installing a no-op handler as opposed to ignoring it is
		2753	that this way, the handler will be restored to defaults on exec.
		2754
		2755	Feel free to install your own handler, or reset it to defaults.
		2756
		2757	=back
		2758
		2759	=cut
		2760
		2761	undef $SIG{CHLD}
		2762	if $SIG{CHLD} eq 'IGNORE';
		2763
		2764	$SIG{PIPE} = sub { }
		2765	unless defined $SIG{PIPE};
		2766
		2767	=head1 RECOMMENDED/OPTIONAL MODULES
		2768
		2769	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2770	its built-in modules) are required to use it.
		2771
		2772	That does not mean that AnyEvent won't take advantage of some additional
		2773	modules if they are installed.
		2774
		2775	This section explains which additional modules will be used, and how they
		2776	affect AnyEvent's operation.
		2777
		2778	=over 4
		2779
		2780	=item L<Async::Interrupt>
		2781
		2782	This slightly arcane module is used to implement fast signal handling: To
		2783	my knowledge, there is no way to do completely race-free and quick
		2784	signal handling in pure perl. To ensure that signals still get
		2785	delivered, AnyEvent will start an interval timer to wake up perl (and
		2786	catch the signals) with some delay (default is 10 seconds, look for
		2787	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2788
		2789	If this module is available, then it will be used to implement signal
		2790	catching, which means that signals will not be delayed, and the event loop
		2791	will not be interrupted regularly, which is more efficient (and good for
		2792	battery life on laptops).
		2793
		2794	This affects not just the pure-perl event loop, but also other event loops
		2795	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2796
		2797	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2798	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2799	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2800	does nothing for those backends.
		2801
		2802	=item L<EV>
		2803
		2804	This module isn't really "optional", as it is simply one of the backend
		2805	event loops that AnyEvent can use. However, it is simply the best event
		2806	loop available in terms of features, speed and stability: It supports
		2807	the AnyEvent API optimally, implements all the watcher types in XS, does
		2808	automatic timer adjustments even when no monotonic clock is available,
		2809	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2810	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2811	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2812
		2813	If you only use backends that rely on another event loop (e.g. C<Tk>),
		2814	then this module will do nothing for you.
		2815
		2816	=item L<Guard>
		2817
		2818	The guard module, when used, will be used to implement
		2819	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2820	lot less memory), but otherwise doesn't affect guard operation much. It is
		2821	purely used for performance.
		2822
		2823	=item L<JSON> and L<JSON::XS>
		2824
		2825	One of these modules is required when you want to read or write JSON data
		2826	via L<AnyEvent::Handle>. L<JSON> is also written in pure-perl, but can take
		2827	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2828
		2829	=item L<Net::SSLeay>
		2830
		2831	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2832	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2833	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2834
		2835	=item L<Time::HiRes>
		2836
		2837	This module is part of perl since release 5.008. It will be used when the
		2838	chosen event library does not come with a timing source of its own. The
		2839	pure-perl event loop (L<AnyEvent::Loop>) will additionally load it to
		2840	try to use a monotonic clock for timing stability.
		2841
		2842	=back
		2843
1156		2844
1157	=head1 FORK	2845	=head1 FORK
1158		2846
1159	Most event libraries are not fork-safe. The ones who are usually are	2847	Most event libraries are not fork-safe. The ones who are usually are
1160	because they are so inefficient. Only L<EV> is fully fork-aware.	2848	because they rely on inefficient but fork-safe C<select> or C<poll> calls
		2849	- higher performance APIs such as BSD's kqueue or the dreaded Linux epoll
		2850	are usually badly thought-out hacks that are incompatible with fork in
		2851	one way or another. Only L<EV> is fully fork-aware and ensures that you
		2852	continue event-processing in both parent and child (or both, if you know
		2853	what you are doing).
		2854
		2855	This means that, in general, you cannot fork and do event processing in
		2856	the child if the event library was initialised before the fork (which
		2857	usually happens when the first AnyEvent watcher is created, or the library
		2858	is loaded).
1161		2859
1162	If you have to fork, you must either do so I<before> creating your first	2860	If you have to fork, you must either do so I<before> creating your first
1163	watcher OR you must not use AnyEvent at all in the child.	2861	watcher OR you must not use AnyEvent at all in the child OR you must do
		2862	something completely out of the scope of AnyEvent.
		2863
		2864	The problem of doing event processing in the parent I<and> the child
		2865	is much more complicated: even for backends that I<are> fork-aware or
		2866	fork-safe, their behaviour is not usually what you want: fork clones all
		2867	watchers, that means all timers, I/O watchers etc. are active in both
		2868	parent and child, which is almost never what you want. USing C<exec>
		2869	to start worker children from some kind of manage rprocess is usually
		2870	preferred, because it is much easier and cleaner, at the expense of having
		2871	to have another binary.
1164		2872
1165		2873
1166	=head1 SECURITY CONSIDERATIONS	2874	=head1 SECURITY CONSIDERATIONS
1167		2875
1168	AnyEvent can be forced to load any event model via	2876	AnyEvent can be forced to load any event model via
…		…
1173	specified in the variable.	2881	specified in the variable.
1174		2882
1175	You can make AnyEvent completely ignore this variable by deleting it	2883	You can make AnyEvent completely ignore this variable by deleting it
1176	before the first watcher gets created, e.g. with a C<BEGIN> block:	2884	before the first watcher gets created, e.g. with a C<BEGIN> block:
1177		2885
1178	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	2886	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1179		2887
1180	use AnyEvent;	2888	use AnyEvent;
		2889
		2890	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		2891	be used to probe what backend is used and gain other information (which is
		2892	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2893	$ENV{PERL_ANYEVENT_STRICT}.
		2894
		2895	Note that AnyEvent will remove I<all> environment variables starting with
		2896	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2897	enabled.
		2898
		2899
		2900	=head1 BUGS
		2901
		2902	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2903	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2904	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2905	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2906	pronounced).
1181		2907
1182		2908
1183	=head1 SEE ALSO	2909	=head1 SEE ALSO
1184		2910
1185	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	2911	Tutorial/Introduction: L<AnyEvent::Intro>.
1186	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,
1187	L<Event::Lib>, L<Qt>, L<POE>.
1188		2912
1189	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	2913	FAQ: L<AnyEvent::FAQ>.
		2914
		2915	Utility functions: L<AnyEvent::Util> (misc. grab-bag), L<AnyEvent::Log>
		2916	(simply logging).
		2917
		2918	Development/Debugging: L<AnyEvent::Strict> (stricter checking),
		2919	L<AnyEvent::Debug> (interactive shell, watcher tracing).
		2920
		2921	Supported event modules: L<AnyEvent::Loop>, L<EV>, L<EV::Glib>,
		2922	L<Glib::EV>, L<Event>, L<Glib::Event>, L<Glib>, L<Tk>, L<Event::Lib>,
		2923	L<Qt>, L<POE>, L<FLTK>.
		2924
		2925	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
		2926	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
		2927	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1190	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,	2928	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>, L<Anyevent::Impl::Irssi>,
1191	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,	2929	L<AnyEvent::Impl::FLTK>.
1192	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.
1193		2930
		2931	Non-blocking handles, pipes, stream sockets, TCP clients and
		2932	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
		2933
		2934	Asynchronous DNS: L<AnyEvent::DNS>.
		2935
		2936	Thread support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
		2937
1194	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	2938	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::IRC>,
		2939	L<AnyEvent::HTTP>.
1195		2940
1196		2941
1197	=head1 AUTHOR	2942	=head1 AUTHOR
1198		2943
1199	Marc Lehmann <schmorp@schmorp.de>	2944	Marc Lehmann <schmorp@schmorp.de>
1200	http://home.schmorp.de/	2945	http://home.schmorp.de/
1201		2946
1202	=cut	2947	=cut
1203		2948
1204	1	2949	1
1205		2950

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