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Revision 1.295 by root, Wed Oct 28 02:42:06 2009 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 - various supported event loops	5	EV, Event, Glib, Tk, Perl, Event::Lib, Irssi, rxvt-unicode, IO::Async, Qt
		6	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	# file descriptor readable
11	my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub {	13	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
		14
		15	# one-shot or repeating timers
		16	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
		17	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...
		18
		19	print AnyEvent->now; # prints current event loop time
		20	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
		21
		22	# POSIX signal
		23	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
		24
		25	# child process exit
		26	my $w = AnyEvent->child (pid => $pid, cb => sub {
		27	my ($pid, $status) = @_;
12	...	28	...
13	});	29	});
14		30
15	my $w = AnyEvent->timer (after => $seconds, cb => sub {	31	# called when event loop idle (if applicable)
16	...	32	my $w = AnyEvent->idle (cb => sub { ... });
17	});
18		33
19	my $w = AnyEvent->condvar; # stores whether a condition was flagged	34	my $w = AnyEvent->condvar; # stores whether a condition was flagged
		35	$w->send; # wake up current and all future recv's
20	$w->wait; # enters "main loop" till $condvar gets ->broadcast	36	$w->recv; # enters "main loop" till $condvar gets ->send
21	$w->broadcast; # wake up current and all future wait's	37	# use a condvar in callback mode:
		38	$w->cb (sub { $_[0]->recv });
		39
		40	=head1 INTRODUCTION/TUTORIAL
		41
		42	This manpage is mainly a reference manual. If you are interested
		43	in a tutorial or some gentle introduction, have a look at the
		44	L<AnyEvent::Intro> manpage.
		45
		46	=head1 SUPPORT
		47
		48	There is a mailinglist for discussing all things AnyEvent, and an IRC
		49	channel, too.
		50
		51	See the AnyEvent project page at the B<Schmorpforge Ta-Sa Software
		52	Repository>, at L<http://anyevent.schmorp.de>, for more info.
22		53
23	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)	54	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
24		55
25	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	56	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
26	nowadays. So what is different about AnyEvent?	57	nowadays. So what is different about AnyEvent?
27		58
28	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of	59	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
29	policy> and AnyEvent is I<small and efficient>.	60	policy> and AnyEvent is I<small and efficient>.
30		61
31	First and foremost, I<AnyEvent is not an event model> itself, it only	62	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	63	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,	64	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,	65	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	66	only one event loop can be active at the same time in a process. AnyEvent
36	helps hiding the differences between those event loops.	67	cannot change this, but it can hide the differences between those event
		68	loops.
37		69
38	The goal of AnyEvent is to offer module authors the ability to do event	70	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	71	programming (waiting for I/O or timer events) without subscribing to a
40	religion, a way of living, and most importantly: without forcing your	72	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	73	module users into the same thing by forcing them to use the same event
42	model you use.	74	model you use.
43		75
44	For modules like POE or IO::Async (which is a total misnomer as it is	76	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	77	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	78	like joining a cult: After you joined, you are dependent on them and you
47	cannot use anything else, as it is simply incompatible to everything that	79	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	80	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.	81	module are I<also> forced to use the same event loop you use.
50		82
51	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	83	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
52	fine. AnyEvent + Tk works fine etc. etc. but none of these work together	84	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	85	with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if
54	your module uses one of those, every user of your module has to use it,	86	your module uses one of those, every user of your module has to use it,
55	too. But if your module uses AnyEvent, it works transparently with all	87	too. But if your module uses AnyEvent, it works transparently with all
56	event models it supports (including stuff like POE and IO::Async, as long	88	event models it supports (including stuff like IO::Async, as long as those
57	as those use one of the supported event loops. It is trivial to add new	89	use one of the supported event loops. It is trivial to add new event loops
58	event loops to AnyEvent, too, so it is future-proof).	90	to AnyEvent, too, so it is future-proof).
59		91
60	In addition to being free of having to use I<the one and only true event	92	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	93	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	94	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	95	follow. AnyEvent, on the other hand, is lean and up to the point, by only
64	offering the functionality that is necessary, in as thin as a wrapper as	96	offering the functionality that is necessary, in as thin as a wrapper as
65	technically possible.	97	technically possible.
66		98
		99	Of course, AnyEvent comes with a big (and fully optional!) toolbox
		100	of useful functionality, such as an asynchronous DNS resolver, 100%
		101	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
		102	such as Windows) and lots of real-world knowledge and workarounds for
		103	platform bugs and differences.
		104
67	Of course, if you want lots of policy (this can arguably be somewhat	105	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	106	useful) and you want to force your users to use the one and only event
69	model, you should I<not> use this module.	107	model, you should I<not> use this module.
70
71		108
72	=head1 DESCRIPTION	109	=head1 DESCRIPTION
73		110
74	L<AnyEvent> provides an identical interface to multiple event loops. This	111	L<AnyEvent> provides an identical interface to multiple event loops. This
75	allows module authors to utilise an event loop without forcing module	112	allows module authors to utilise an event loop without forcing module
…		…
79	The interface itself is vaguely similar, but not identical to the L<Event>	116	The interface itself is vaguely similar, but not identical to the L<Event>
80	module.	117	module.
81		118
82	During the first call of any watcher-creation method, the module tries	119	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	120	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>,	121	following modules is already loaded: L<EV>,
85	L<Event>, L<Glib>, L<Tk>. The first one found is used. If none are found,	122	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,
86	the module tries to load these modules in the stated order. The first one	123	L<POE>. The first one found is used. If none are found, the module tries
		124	to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl
		125	adaptor should always succeed) in the order given. The first one that can
87	that can be successfully loaded will be used. If, after this, still none	126	be successfully loaded will be used. If, after this, still none could be
88	could be found, AnyEvent will fall back to a pure-perl event loop, which	127	found, AnyEvent will fall back to a pure-perl event loop, which is not
89	is not very efficient, but should work everywhere.	128	very efficient, but should work everywhere.
90		129
91	Because AnyEvent first checks for modules that are already loaded, loading	130	Because AnyEvent first checks for modules that are already loaded, loading
92	an event model explicitly before first using AnyEvent will likely make	131	an event model explicitly before first using AnyEvent will likely make
93	that model the default. For example:	132	that model the default. For example:
94		133
…		…
101	starts using it, all bets are off. Maybe you should tell their authors to	140	starts using it, all bets are off. Maybe you should tell their authors to
102	use AnyEvent so their modules work together with others seamlessly...	141	use AnyEvent so their modules work together with others seamlessly...
103		142
104	The pure-perl implementation of AnyEvent is called	143	The pure-perl implementation of AnyEvent is called
105	C<AnyEvent::Impl::Perl>. Like other event modules you can load it	144	C<AnyEvent::Impl::Perl>. Like other event modules you can load it
106	explicitly.	145	explicitly and enjoy the high availability of that event loop :)
107		146
108	=head1 WATCHERS	147	=head1 WATCHERS
109		148
110	AnyEvent has the central concept of a I<watcher>, which is an object that	149	AnyEvent has the central concept of a I<watcher>, which is an object that
111	stores relevant data for each kind of event you are waiting for, such as	150	stores relevant data for each kind of event you are waiting for, such as
112	the callback to call, the filehandle to watch, etc.	151	the callback to call, the file handle to watch, etc.
113		152
114	These watchers are normal Perl objects with normal Perl lifetime. After	153	These watchers are normal Perl objects with normal Perl lifetime. After
115	creating a watcher it will immediately "watch" for events and invoke the	154	creating a watcher it will immediately "watch" for events and invoke the
116	callback when the event occurs (of course, only when the event model	155	callback when the event occurs (of course, only when the event model
117	is in control).	156	is in control).
118		157
		158	Note that B<callbacks must not permanently change global variables>
		159	potentially in use by the event loop (such as C<$_> or C<$[>) and that B<<
		160	callbacks must not C<die> >>. The former is good programming practise in
		161	Perl and the latter stems from the fact that exception handling differs
		162	widely between event loops.
		163
119	To disable the watcher you have to destroy it (e.g. by setting the	164	To disable the watcher you have to destroy it (e.g. by setting the
120	variable you store it in to C<undef> or otherwise deleting all references	165	variable you store it in to C<undef> or otherwise deleting all references
121	to it).	166	to it).
122		167
123	All watchers are created by calling a method on the C<AnyEvent> class.	168	All watchers are created by calling a method on the C<AnyEvent> class.
…		…
125	Many watchers either are used with "recursion" (repeating timers for	170	Many watchers either are used with "recursion" (repeating timers for
126	example), or need to refer to their watcher object in other ways.	171	example), or need to refer to their watcher object in other ways.
127		172
128	An any way to achieve that is this pattern:	173	An any way to achieve that is this pattern:
129		174
130	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	175	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
131	# you can use $w here, for example to undef it	176	# you can use $w here, for example to undef it
132	undef $w;	177	undef $w;
133	});	178	});
134		179
135	Note that C<my $w; $w => combination. This is necessary because in Perl,	180	Note that C<my $w; $w => combination. This is necessary because in Perl,
136	my variables are only visible after the statement in which they are	181	my variables are only visible after the statement in which they are
137	declared.	182	declared.
138		183
139	=head2 IO WATCHERS	184	=head2 I/O WATCHERS
		185
		186	$w = AnyEvent->io (
		187	fh => <filehandle_or_fileno>,
		188	poll => <"r" or "w">,
		189	cb => <callback>,
		190	);
140		191
141	You can create an I/O watcher by calling the C<< AnyEvent->io >> method	192	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
142	with the following mandatory key-value pairs as arguments:	193	with the following mandatory key-value pairs as arguments:
143		194
144	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch for	195	C<fh> is the Perl I<file handle> (or a naked file descriptor) to watch
		196	for events (AnyEvent might or might not keep a reference to this file
		197	handle). Note that only file handles pointing to things for which
		198	non-blocking operation makes sense are allowed. This includes sockets,
		199	most character devices, pipes, fifos and so on, but not for example files
		200	or block devices.
		201
145	events. C<poll> must be a string that is either C<r> or C<w>, which	202	C<poll> must be a string that is either C<r> or C<w>, which creates a
146	creates a watcher waiting for "r"eadable or "w"ritable events,	203	watcher waiting for "r"eadable or "w"ritable events, respectively.
		204
147	respectively. C<cb> is the callback to invoke each time the file handle	205	C<cb> is the callback to invoke each time the file handle becomes ready.
148	becomes ready.
149		206
150	File handles will be kept alive, so as long as the watcher exists, the	207	Although the callback might get passed parameters, their value and
151	file handle exists, too.	208	presence is undefined and you cannot rely on them. Portable AnyEvent
		209	callbacks cannot use arguments passed to I/O watcher callbacks.
152		210
		211	The I/O watcher might use the underlying file descriptor or a copy of it.
153	It is not allowed to close a file handle as long as any watcher is active	212	You must not close a file handle as long as any watcher is active on the
154	on the underlying file descriptor.	213	underlying file descriptor.
155		214
156	Some event loops issue spurious readyness notifications, so you should	215	Some event loops issue spurious readyness notifications, so you should
157	always use non-blocking calls when reading/writing from/to your file	216	always use non-blocking calls when reading/writing from/to your file
158	handles.	217	handles.
159		218
160	Example:
161
162	# wait for readability of STDIN, then read a line and disable the watcher	219	Example: wait for readability of STDIN, then read a line and disable the
		220	watcher.
		221
163	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	222	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
164	chomp (my $input = <STDIN>);	223	chomp (my $input = <STDIN>);
165	warn "read: $input\n";	224	warn "read: $input\n";
166	undef $w;	225	undef $w;
167	});	226	});
168		227
169	=head2 TIME WATCHERS	228	=head2 TIME WATCHERS
170		229
		230	$w = AnyEvent->timer (after => <seconds>, cb => <callback>);
		231
		232	$w = AnyEvent->timer (
		233	after => <fractional_seconds>,
		234	interval => <fractional_seconds>,
		235	cb => <callback>,
		236	);
		237
171	You can create a time watcher by calling the C<< AnyEvent->timer >>	238	You can create a time watcher by calling the C<< AnyEvent->timer >>
172	method with the following mandatory arguments:	239	method with the following mandatory arguments:
173		240
174	C<after> specifies after how many seconds (fractional values are	241	C<after> specifies after how many seconds (fractional values are
175	supported) should the timer activate. C<cb> the callback to invoke in that	242	supported) the callback should be invoked. C<cb> is the callback to invoke
176	case.	243	in that case.
177		244
178	The timer callback will be invoked at most once: if you want a repeating	245	Although the callback might get passed parameters, their value and
179	timer you have to create a new watcher (this is a limitation by both Tk	246	presence is undefined and you cannot rely on them. Portable AnyEvent
180	and Glib).	247	callbacks cannot use arguments passed to time watcher callbacks.
181		248
182	Example:	249	The callback will normally be invoked once only. If you specify another
		250	parameter, C<interval>, as a strictly positive number (> 0), then the
		251	callback will be invoked regularly at that interval (in fractional
		252	seconds) after the first invocation. If C<interval> is specified with a
		253	false value, then it is treated as if it were missing.
183		254
		255	The callback will be rescheduled before invoking the callback, but no
		256	attempt is done to avoid timer drift in most backends, so the interval is
		257	only approximate.
		258
184	# fire an event after 7.7 seconds	259	Example: fire an event after 7.7 seconds.
		260
185	my $w = AnyEvent->timer (after => 7.7, cb => sub {	261	my $w = AnyEvent->timer (after => 7.7, cb => sub {
186	warn "timeout\n";	262	warn "timeout\n";
187	});	263	});
188		264
189	# to cancel the timer:	265	# to cancel the timer:
190	undef $w;	266	undef $w;
191		267
192	Example 2:
193
194	# fire an event after 0.5 seconds, then roughly every second	268	Example 2: fire an event after 0.5 seconds, then roughly every second.
195	my $w;
196		269
197	my $cb = sub {
198	# cancel the old timer while creating a new one
199	$w = AnyEvent->timer (after => 1, cb => $cb);	270	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		271	warn "timeout\n";
200	};	272	};
201
202	# start the "loop" by creating the first watcher
203	$w = AnyEvent->timer (after => 0.5, cb => $cb);
204		273
205	=head3 TIMING ISSUES	274	=head3 TIMING ISSUES
206		275
207	There are two ways to handle timers: based on real time (relative, "fire	276	There are two ways to handle timers: based on real time (relative, "fire
208	in 10 seconds") and based on wallclock time (absolute, "fire at 12	277	in 10 seconds") and based on wallclock time (absolute, "fire at 12
209	o'clock").	278	o'clock").
210		279
211	While most event loops expect timers to specified in a relative way, they use	280	While most event loops expect timers to specified in a relative way, they
212	absolute time internally. This makes a difference when your clock "jumps",	281	use absolute time internally. This makes a difference when your clock
213	for example, when ntp decides to set your clock backwards from the wrong 2014-01-01 to	282	"jumps", for example, when ntp decides to set your clock backwards from
214	2008-01-01, a watcher that you created to fire "after" a second might actually take	283	the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to
215	six years to finally fire.	284	fire "after" a second might actually take six years to finally fire.
216		285
217	AnyEvent cannot compensate for this. The only event loop that is conscious	286	AnyEvent cannot compensate for this. The only event loop that is conscious
218	about these issues is L<EV>, which offers both relative (ev_timer) and	287	about these issues is L<EV>, which offers both relative (ev_timer, based
219	absolute (ev_periodic) timers.	288	on true relative time) and absolute (ev_periodic, based on wallclock time)
		289	timers.
220		290
221	AnyEvent always prefers relative timers, if available, matching the	291	AnyEvent always prefers relative timers, if available, matching the
222	AnyEvent API.	292	AnyEvent API.
223		293
		294	AnyEvent has two additional methods that return the "current time":
		295
		296	=over 4
		297
		298	=item AnyEvent->time
		299
		300	This returns the "current wallclock time" as a fractional number of
		301	seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
		302	return, and the result is guaranteed to be compatible with those).
		303
		304	It progresses independently of any event loop processing, i.e. each call
		305	will check the system clock, which usually gets updated frequently.
		306
		307	=item AnyEvent->now
		308
		309	This also returns the "current wallclock time", but unlike C<time>, above,
		310	this value might change only once per event loop iteration, depending on
		311	the event loop (most return the same time as C<time>, above). This is the
		312	time that AnyEvent's timers get scheduled against.
		313
		314	I<In almost all cases (in all cases if you don't care), this is the
		315	function to call when you want to know the current time.>
		316
		317	This function is also often faster then C<< AnyEvent->time >>, and
		318	thus the preferred method if you want some timestamp (for example,
		319	L<AnyEvent::Handle> uses this to update it's activity timeouts).
		320
		321	The rest of this section is only of relevance if you try to be very exact
		322	with your timing, you can skip it without bad conscience.
		323
		324	For a practical example of when these times differ, consider L<Event::Lib>
		325	and L<EV> and the following set-up:
		326
		327	The event loop is running and has just invoked one of your callback at
		328	time=500 (assume no other callbacks delay processing). In your callback,
		329	you wait a second by executing C<sleep 1> (blocking the process for a
		330	second) and then (at time=501) you create a relative timer that fires
		331	after three seconds.
		332
		333	With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
		334	both return C<501>, because that is the current time, and the timer will
		335	be scheduled to fire at time=504 (C<501> + C<3>).
		336
		337	With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
		338	time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
		339	last event processing phase started. With L<EV>, your timer gets scheduled
		340	to run at time=503 (C<500> + C<3>).
		341
		342	In one sense, L<Event::Lib> is more exact, as it uses the current time
		343	regardless of any delays introduced by event processing. However, most
		344	callbacks do not expect large delays in processing, so this causes a
		345	higher drift (and a lot more system calls to get the current time).
		346
		347	In another sense, L<EV> is more exact, as your timer will be scheduled at
		348	the same time, regardless of how long event processing actually took.
		349
		350	In either case, if you care (and in most cases, you don't), then you
		351	can get whatever behaviour you want with any event loop, by taking the
		352	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
		353	account.
		354
		355	=item AnyEvent->now_update
		356
		357	Some event loops (such as L<EV> or L<AnyEvent::Impl::Perl>) cache
		358	the current time for each loop iteration (see the discussion of L<<
		359	AnyEvent->now >>, above).
		360
		361	When a callback runs for a long time (or when the process sleeps), then
		362	this "current" time will differ substantially from the real time, which
		363	might affect timers and time-outs.
		364
		365	When this is the case, you can call this method, which will update the
		366	event loop's idea of "current time".
		367
		368	Note that updating the time I<might> cause some events to be handled.
		369
		370	=back
		371
224	=head2 SIGNAL WATCHERS	372	=head2 SIGNAL WATCHERS
225		373
		374	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		375
226	You can watch for signals using a signal watcher, C<signal> is the signal	376	You can watch for signals using a signal watcher, C<signal> is the signal
227	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to	377	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
228	be invoked whenever a signal occurs.	378	callback to be invoked whenever a signal occurs.
229		379
		380	Although the callback might get passed parameters, their value and
		381	presence is undefined and you cannot rely on them. Portable AnyEvent
		382	callbacks cannot use arguments passed to signal watcher callbacks.
		383
230	Multiple signals occurances can be clumped together into one callback	384	Multiple signal occurrences can be clumped together into one callback
231	invocation, and callback invocation will be synchronous. synchronous means	385	invocation, and callback invocation will be synchronous. Synchronous means
232	that it might take a while until the signal gets handled by the process,	386	that it might take a while until the signal gets handled by the process,
233	but it is guarenteed not to interrupt any other callbacks.	387	but it is guaranteed not to interrupt any other callbacks.
234		388
235	The main advantage of using these watchers is that you can share a signal	389	The main advantage of using these watchers is that you can share a signal
236	between multiple watchers.	390	between multiple watchers, and AnyEvent will ensure that signals will not
		391	interrupt your program at bad times.
237		392
238	This watcher might use C<%SIG>, so programs overwriting those signals	393	This watcher might use C<%SIG> (depending on the event loop used),
239	directly will likely not work correctly.	394	so programs overwriting those signals directly will likely not work
		395	correctly.
240		396
241	Example: exit on SIGINT	397	Example: exit on SIGINT
242		398
243	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	399	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
244		400
		401	=head3 Signal Races, Delays and Workarounds
		402
		403	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		404	callbacks to signals in a generic way, which is a pity, as you cannot
		405	do race-free signal handling in perl, requiring C libraries for
		406	this. AnyEvent will try to do it's best, which means in some cases,
		407	signals will be delayed. The maximum time a signal might be delayed is
		408	specified in C<$AnyEvent::MAX_SIGNAL_LATENCY> (default: 10 seconds). This
		409	variable can be changed only before the first signal watcher is created,
		410	and should be left alone otherwise. This variable determines how often
		411	AnyEvent polls for signals (in case a wake-up was missed). Higher values
		412	will cause fewer spurious wake-ups, which is better for power and CPU
		413	saving.
		414
		415	All these problems can be avoided by installing the optional
		416	L<Async::Interrupt> module, which works with most event loops. It will not
		417	work with inherently broken event loops such as L<Event> or L<Event::Lib>
		418	(and not with L<POE> currently, as POE does it's own workaround with
		419	one-second latency). For those, you just have to suffer the delays.
		420
245	=head2 CHILD PROCESS WATCHERS	421	=head2 CHILD PROCESS WATCHERS
246		422
		423	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		424
247	You can also watch on a child process exit and catch its exit status.	425	You can also watch on a child process exit and catch its exit status.
248		426
249	The child process is specified by the C<pid> argument (if set to C<0>, it	427	The child process is specified by the C<pid> argument (one some backends,
250	watches for any child process exit). The watcher will trigger as often	428	using C<0> watches for any child process exit, on others this will
251	as status change for the child are received. This works by installing a	429	croak). The watcher will be triggered only when the child process has
252	signal handler for C<SIGCHLD>. The callback will be called with the pid	430	finished and an exit status is available, not on any trace events
253	and exit status (as returned by waitpid).	431	(stopped/continued).
254		432
255	Example: wait for pid 1333	433	The callback will be called with the pid and exit status (as returned by
		434	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		435	callback arguments.
256		436
		437	This watcher type works by installing a signal handler for C<SIGCHLD>,
		438	and since it cannot be shared, nothing else should use SIGCHLD or reap
		439	random child processes (waiting for specific child processes, e.g. inside
		440	C<system>, is just fine).
		441
		442	There is a slight catch to child watchers, however: you usually start them
		443	I<after> the child process was created, and this means the process could
		444	have exited already (and no SIGCHLD will be sent anymore).
		445
		446	Not all event models handle this correctly (neither POE nor IO::Async do,
		447	see their AnyEvent::Impl manpages for details), but even for event models
		448	that I<do> handle this correctly, they usually need to be loaded before
		449	the process exits (i.e. before you fork in the first place). AnyEvent's
		450	pure perl event loop handles all cases correctly regardless of when you
		451	start the watcher.
		452
		453	This means you cannot create a child watcher as the very first
		454	thing in an AnyEvent program, you I<have> to create at least one
		455	watcher before you C<fork> the child (alternatively, you can call
		456	C<AnyEvent::detect>).
		457
		458	As most event loops do not support waiting for child events, they will be
		459	emulated by AnyEvent in most cases, in which the latency and race problems
		460	mentioned in the description of signal watchers apply.
		461
		462	Example: fork a process and wait for it
		463
		464	my $done = AnyEvent->condvar;
		465
		466	my $pid = fork or exit 5;
		467
257	my $w = AnyEvent->child (	468	my $w = AnyEvent->child (
258	pid => 1333,	469	pid => $pid,
259	cb => sub {	470	cb => sub {
260	my ($pid, $status) = @_;	471	my ($pid, $status) = @_;
261	warn "pid $pid exited with status $status";	472	warn "pid $pid exited with status $status";
		473	$done->send;
262	},	474	},
263	);	475	);
		476
		477	# do something else, then wait for process exit
		478	$done->recv;
		479
		480	=head2 IDLE WATCHERS
		481
		482	$w = AnyEvent->idle (cb => <callback>);
		483
		484	Sometimes there is a need to do something, but it is not so important
		485	to do it instantly, but only when there is nothing better to do. This
		486	"nothing better to do" is usually defined to be "no other events need
		487	attention by the event loop".
		488
		489	Idle watchers ideally get invoked when the event loop has nothing
		490	better to do, just before it would block the process to wait for new
		491	events. Instead of blocking, the idle watcher is invoked.
		492
		493	Most event loops unfortunately do not really support idle watchers (only
		494	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		495	will simply call the callback "from time to time".
		496
		497	Example: read lines from STDIN, but only process them when the
		498	program is otherwise idle:
		499
		500	my @lines; # read data
		501	my $idle_w;
		502	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		503	push @lines, scalar <STDIN>;
		504
		505	# start an idle watcher, if not already done
		506	$idle_w ||= AnyEvent->idle (cb => sub {
		507	# handle only one line, when there are lines left
		508	if (my $line = shift @lines) {
		509	print "handled when idle: $line";
		510	} else {
		511	# otherwise disable the idle watcher again
		512	undef $idle_w;
		513	}
		514	});
		515	});
264		516
265	=head2 CONDITION VARIABLES	517	=head2 CONDITION VARIABLES
266		518
		519	$cv = AnyEvent->condvar;
		520
		521	$cv->send (<list>);
		522	my @res = $cv->recv;
		523
		524	If you are familiar with some event loops you will know that all of them
		525	require you to run some blocking "loop", "run" or similar function that
		526	will actively watch for new events and call your callbacks.
		527
		528	AnyEvent is slightly different: it expects somebody else to run the event
		529	loop and will only block when necessary (usually when told by the user).
		530
		531	The instrument to do that is called a "condition variable", so called
		532	because they represent a condition that must become true.
		533
		534	Now is probably a good time to look at the examples further below.
		535
267	Condition variables can be created by calling the C<< AnyEvent->condvar >>	536	Condition variables can be created by calling the C<< AnyEvent->condvar
268	method without any arguments.	537	>> method, usually without arguments. The only argument pair allowed is
		538	C<cb>, which specifies a callback to be called when the condition variable
		539	becomes true, with the condition variable as the first argument (but not
		540	the results).
269		541
270	A condition variable waits for a condition - precisely that the C<<	542	After creation, the condition variable is "false" until it becomes "true"
271	->broadcast >> method has been called.	543	by calling the C<send> method (or calling the condition variable as if it
		544	were a callback, read about the caveats in the description for the C<<
		545	->send >> method).
272		546
273	They are very useful to signal that a condition has been fulfilled, for	547	Condition variables are similar to callbacks, except that you can
		548	optionally wait for them. They can also be called merge points - points
		549	in time where multiple outstanding events have been processed. And yet
		550	another way to call them is transactions - each condition variable can be
		551	used to represent a transaction, which finishes at some point and delivers
		552	a result. And yet some people know them as "futures" - a promise to
		553	compute/deliver something that you can wait for.
		554
		555	Condition variables are very useful to signal that something has finished,
274	example, if you write a module that does asynchronous http requests,	556	for example, if you write a module that does asynchronous http requests,
275	then a condition variable would be the ideal candidate to signal the	557	then a condition variable would be the ideal candidate to signal the
276	availability of results.	558	availability of results. The user can either act when the callback is
		559	called or can synchronously C<< ->recv >> for the results.
277		560
278	You can also use condition variables to block your main program until	561	You can also use them to simulate traditional event loops - for example,
279	an event occurs - for example, you could C<< ->wait >> in your main	562	you can block your main program until an event occurs - for example, you
280	program until the user clicks the Quit button in your app, which would C<<	563	could C<< ->recv >> in your main program until the user clicks the Quit
281	->broadcast >> the "quit" event.	564	button of your app, which would C<< ->send >> the "quit" event.
282		565
283	Note that condition variables recurse into the event loop - if you have	566	Note that condition variables recurse into the event loop - if you have
284	two pirces of code that call C<< ->wait >> in a round-robbin fashion, you	567	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
285	lose. Therefore, condition variables are good to export to your caller, but	568	lose. Therefore, condition variables are good to export to your caller, but
286	you should avoid making a blocking wait yourself, at least in callbacks,	569	you should avoid making a blocking wait yourself, at least in callbacks,
287	as this asks for trouble.	570	as this asks for trouble.
288		571
289	This object has two methods:	572	Condition variables are represented by hash refs in perl, and the keys
		573	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
		574	easy (it is often useful to build your own transaction class on top of
		575	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
		576	it's C<new> method in your own C<new> method.
290		577
291	=over 4	578	There are two "sides" to a condition variable - the "producer side" which
		579	eventually calls C<< -> send >>, and the "consumer side", which waits
		580	for the send to occur.
292		581
293	=item $cv->wait	582	Example: wait for a timer.
294
295	Wait (blocking if necessary) until the C<< ->broadcast >> method has been
296	called on c<$cv>, while servicing other watchers normally.
297
298	You can only wait once on a condition - additional calls will return
299	immediately.
300
301	Not all event models support a blocking wait - some die in that case
302	(programs might want to do that to stay interactive), so I<if you are
303	using this from a module, never require a blocking wait>, but let the
304	caller decide whether the call will block or not (for example, by coupling
305	condition variables with some kind of request results and supporting
306	callbacks so the caller knows that getting the result will not block,
307	while still suppporting blocking waits if the caller so desires).
308
309	Another reason I<never> to C<< ->wait >> in a module is that you cannot
310	sensibly have two C<< ->wait >>'s in parallel, as that would require
311	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
312	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and
313	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
314	from different coroutines, however).
315
316	=item $cv->broadcast
317
318	Flag the condition as ready - a running C<< ->wait >> and all further
319	calls to C<wait> will (eventually) return after this method has been
320	called. If nobody is waiting the broadcast will be remembered..
321
322	=back
323
324	Example:
325		583
326	# wait till the result is ready	584	# wait till the result is ready
327	my $result_ready = AnyEvent->condvar;	585	my $result_ready = AnyEvent->condvar;
328		586
329	# do something such as adding a timer	587	# do something such as adding a timer
330	# or socket watcher the calls $result_ready->broadcast	588	# or socket watcher the calls $result_ready->send
331	# when the "result" is ready.	589	# when the "result" is ready.
332	# in this case, we simply use a timer:	590	# in this case, we simply use a timer:
333	my $w = AnyEvent->timer (	591	my $w = AnyEvent->timer (
334	after => 1,	592	after => 1,
335	cb => sub { $result_ready->broadcast },	593	cb => sub { $result_ready->send },
336	);	594	);
337		595
338	# this "blocks" (while handling events) till the watcher	596	# this "blocks" (while handling events) till the callback
339	# calls broadcast	597	# calls ->send
340	$result_ready->wait;	598	$result_ready->recv;
		599
		600	Example: wait for a timer, but take advantage of the fact that condition
		601	variables are also callable directly.
		602
		603	my $done = AnyEvent->condvar;
		604	my $delay = AnyEvent->timer (after => 5, cb => $done);
		605	$done->recv;
		606
		607	Example: Imagine an API that returns a condvar and doesn't support
		608	callbacks. This is how you make a synchronous call, for example from
		609	the main program:
		610
		611	use AnyEvent::CouchDB;
		612
		613	...
		614
		615	my @info = $couchdb->info->recv;
		616
		617	And this is how you would just set a callback to be called whenever the
		618	results are available:
		619
		620	$couchdb->info->cb (sub {
		621	my @info = $_[0]->recv;
		622	});
		623
		624	=head3 METHODS FOR PRODUCERS
		625
		626	These methods should only be used by the producing side, i.e. the
		627	code/module that eventually sends the signal. Note that it is also
		628	the producer side which creates the condvar in most cases, but it isn't
		629	uncommon for the consumer to create it as well.
		630
		631	=over 4
		632
		633	=item $cv->send (...)
		634
		635	Flag the condition as ready - a running C<< ->recv >> and all further
		636	calls to C<recv> will (eventually) return after this method has been
		637	called. If nobody is waiting the send will be remembered.
		638
		639	If a callback has been set on the condition variable, it is called
		640	immediately from within send.
		641
		642	Any arguments passed to the C<send> call will be returned by all
		643	future C<< ->recv >> calls.
		644
		645	Condition variables are overloaded so one can call them directly (as if
		646	they were a code reference). Calling them directly is the same as calling
		647	C<send>.
		648
		649	=item $cv->croak ($error)
		650
		651	Similar to send, but causes all call's to C<< ->recv >> to invoke
		652	C<Carp::croak> with the given error message/object/scalar.
		653
		654	This can be used to signal any errors to the condition variable
		655	user/consumer. Doing it this way instead of calling C<croak> directly
		656	delays the error detetcion, but has the overwhelmign advantage that it
		657	diagnoses the error at the place where the result is expected, and not
		658	deep in some event clalback without connection to the actual code causing
		659	the problem.
		660
		661	=item $cv->begin ([group callback])
		662
		663	=item $cv->end
		664
		665	These two methods can be used to combine many transactions/events into
		666	one. For example, a function that pings many hosts in parallel might want
		667	to use a condition variable for the whole process.
		668
		669	Every call to C<< ->begin >> will increment a counter, and every call to
		670	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
		671	>>, the (last) callback passed to C<begin> will be executed, passing the
		672	condvar as first argument. That callback is I<supposed> to call C<< ->send
		673	>>, but that is not required. If no group callback was set, C<send> will
		674	be called without any arguments.
		675
		676	You can think of C<< $cv->send >> giving you an OR condition (one call
		677	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		678	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		679
		680	Let's start with a simple example: you have two I/O watchers (for example,
		681	STDOUT and STDERR for a program), and you want to wait for both streams to
		682	close before activating a condvar:
		683
		684	my $cv = AnyEvent->condvar;
		685
		686	$cv->begin; # first watcher
		687	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		688	defined sysread $fh1, my $buf, 4096
		689	or $cv->end;
		690	});
		691
		692	$cv->begin; # second watcher
		693	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		694	defined sysread $fh2, my $buf, 4096
		695	or $cv->end;
		696	});
		697
		698	$cv->recv;
		699
		700	This works because for every event source (EOF on file handle), there is
		701	one call to C<begin>, so the condvar waits for all calls to C<end> before
		702	sending.
		703
		704	The ping example mentioned above is slightly more complicated, as the
		705	there are results to be passwd back, and the number of tasks that are
		706	begung can potentially be zero:
		707
		708	my $cv = AnyEvent->condvar;
		709
		710	my %result;
		711	$cv->begin (sub { shift->send (\%result) });
		712
		713	for my $host (@list_of_hosts) {
		714	$cv->begin;
		715	ping_host_then_call_callback $host, sub {
		716	$result{$host} = ...;
		717	$cv->end;
		718	};
		719	}
		720
		721	$cv->end;
		722
		723	This code fragment supposedly pings a number of hosts and calls
		724	C<send> after results for all then have have been gathered - in any
		725	order. To achieve this, the code issues a call to C<begin> when it starts
		726	each ping request and calls C<end> when it has received some result for
		727	it. Since C<begin> and C<end> only maintain a counter, the order in which
		728	results arrive is not relevant.
		729
		730	There is an additional bracketing call to C<begin> and C<end> outside the
		731	loop, which serves two important purposes: first, it sets the callback
		732	to be called once the counter reaches C<0>, and second, it ensures that
		733	C<send> is called even when C<no> hosts are being pinged (the loop
		734	doesn't execute once).
		735
		736	This is the general pattern when you "fan out" into multiple (but
		737	potentially none) subrequests: use an outer C<begin>/C<end> pair to set
		738	the callback and ensure C<end> is called at least once, and then, for each
		739	subrequest you start, call C<begin> and for each subrequest you finish,
		740	call C<end>.
		741
		742	=back
		743
		744	=head3 METHODS FOR CONSUMERS
		745
		746	These methods should only be used by the consuming side, i.e. the
		747	code awaits the condition.
		748
		749	=over 4
		750
		751	=item $cv->recv
		752
		753	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
		754	>> methods have been called on c<$cv>, while servicing other watchers
		755	normally.
		756
		757	You can only wait once on a condition - additional calls are valid but
		758	will return immediately.
		759
		760	If an error condition has been set by calling C<< ->croak >>, then this
		761	function will call C<croak>.
		762
		763	In list context, all parameters passed to C<send> will be returned,
		764	in scalar context only the first one will be returned.
		765
		766	Note that doing a blocking wait in a callback is not supported by any
		767	event loop, that is, recursive invocation of a blocking C<< ->recv
		768	>> is not allowed, and the C<recv> call will C<croak> if such a
		769	condition is detected. This condition can be slightly loosened by using
		770	L<Coro::AnyEvent>, which allows you to do a blocking C<< ->recv >> from
		771	any thread that doesn't run the event loop itself.
		772
		773	Not all event models support a blocking wait - some die in that case
		774	(programs might want to do that to stay interactive), so I<if you are
		775	using this from a module, never require a blocking wait>. Instead, let the
		776	caller decide whether the call will block or not (for example, by coupling
		777	condition variables with some kind of request results and supporting
		778	callbacks so the caller knows that getting the result will not block,
		779	while still supporting blocking waits if the caller so desires).
		780
		781	You can ensure that C<< -recv >> never blocks by setting a callback and
		782	only calling C<< ->recv >> from within that callback (or at a later
		783	time). This will work even when the event loop does not support blocking
		784	waits otherwise.
		785
		786	=item $bool = $cv->ready
		787
		788	Returns true when the condition is "true", i.e. whether C<send> or
		789	C<croak> have been called.
		790
		791	=item $cb = $cv->cb ($cb->($cv))
		792
		793	This is a mutator function that returns the callback set and optionally
		794	replaces it before doing so.
		795
		796	The callback will be called when the condition becomes (or already was)
		797	"true", i.e. when C<send> or C<croak> are called (or were called), with
		798	the only argument being the condition variable itself. Calling C<recv>
		799	inside the callback or at any later time is guaranteed not to block.
		800
		801	=back
		802
		803	=head1 SUPPORTED EVENT LOOPS/BACKENDS
		804
		805	The available backend classes are (every class has its own manpage):
		806
		807	=over 4
		808
		809	=item Backends that are autoprobed when no other event loop can be found.
		810
		811	EV is the preferred backend when no other event loop seems to be in
		812	use. If EV is not installed, then AnyEvent will fall back to its own
		813	pure-perl implementation, which is available everywhere as it comes with
		814	AnyEvent itself.
		815
		816	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		817	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
		818
		819	=item Backends that are transparently being picked up when they are used.
		820
		821	These will be used when they are currently loaded when the first watcher
		822	is created, in which case it is assumed that the application is using
		823	them. This means that AnyEvent will automatically pick the right backend
		824	when the main program loads an event module before anything starts to
		825	create watchers. Nothing special needs to be done by the main program.
		826
		827	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		828	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		829	AnyEvent::Impl::Tk based on Tk, very broken.
		830	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		831	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		832	AnyEvent::Impl::Irssi used when running within irssi.
		833
		834	=item Backends with special needs.
		835
		836	Qt requires the Qt::Application to be instantiated first, but will
		837	otherwise be picked up automatically. As long as the main program
		838	instantiates the application before any AnyEvent watchers are created,
		839	everything should just work.
		840
		841	AnyEvent::Impl::Qt based on Qt.
		842
		843	Support for IO::Async can only be partial, as it is too broken and
		844	architecturally limited to even support the AnyEvent API. It also
		845	is the only event loop that needs the loop to be set explicitly, so
		846	it can only be used by a main program knowing about AnyEvent. See
		847	L<AnyEvent::Impl::Async> for the gory details.
		848
		849	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
		850
		851	=item Event loops that are indirectly supported via other backends.
		852
		853	Some event loops can be supported via other modules:
		854
		855	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		856
		857	B<WxWidgets> has no support for watching file handles. However, you can
		858	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		859	polls 20 times per second, which was considered to be too horrible to even
		860	consider for AnyEvent.
		861
		862	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		863	backend, so it can be supported through POE.
		864
		865	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		866	load L<POE> when detecting them, in the hope that POE will pick them up,
		867	in which case everything will be automatic.
		868
		869	=back
341		870
342	=head1 GLOBAL VARIABLES AND FUNCTIONS	871	=head1 GLOBAL VARIABLES AND FUNCTIONS
343		872
		873	These are not normally required to use AnyEvent, but can be useful to
		874	write AnyEvent extension modules.
		875
344	=over 4	876	=over 4
345		877
346	=item $AnyEvent::MODEL	878	=item $AnyEvent::MODEL
347		879
348	Contains C<undef> until the first watcher is being created. Then it	880	Contains C<undef> until the first watcher is being created, before the
		881	backend has been autodetected.
		882
349	contains the event model that is being used, which is the name of the	883	Afterwards it contains the event model that is being used, which is the
350	Perl class implementing the model. This class is usually one of the	884	name of the Perl class implementing the model. This class is usually one
351	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	885	of the C<AnyEvent::Impl:xxx> modules, but can be any other class in the
352	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	886	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
353		887	will be C<urxvt::anyevent>).
354	The known classes so far are:
355
356	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
357	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
358	AnyEvent::Impl::EV based on EV (an interface to libev, also best choice).
359	AnyEvent::Impl::Event based on Event, also second best choice :)
360	AnyEvent::Impl::Glib based on Glib, third-best choice.
361	AnyEvent::Impl::Tk based on Tk, very bad choice.
362	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
363	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
364		888
365	=item AnyEvent::detect	889	=item AnyEvent::detect
366		890
367	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	891	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
368	if necessary. You should only call this function right before you would	892	if necessary. You should only call this function right before you would
369	have created an AnyEvent watcher anyway, that is, as late as possible at	893	have created an AnyEvent watcher anyway, that is, as late as possible at
370	runtime.	894	runtime, and not e.g. while initialising of your module.
		895
		896	If you need to do some initialisation before AnyEvent watchers are
		897	created, use C<post_detect>.
		898
		899	=item $guard = AnyEvent::post_detect { BLOCK }
		900
		901	Arranges for the code block to be executed as soon as the event model is
		902	autodetected (or immediately if this has already happened).
		903
		904	The block will be executed I<after> the actual backend has been detected
		905	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		906	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		907	other initialisations - see the sources of L<AnyEvent::Strict> or
		908	L<AnyEvent::AIO> to see how this is used.
		909
		910	The most common usage is to create some global watchers, without forcing
		911	event module detection too early, for example, L<AnyEvent::AIO> creates
		912	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		913	avoid autodetecting the event module at load time.
		914
		915	If called in scalar or list context, then it creates and returns an object
		916	that automatically removes the callback again when it is destroyed (or
		917	C<undef> when the hook was immediately executed). See L<AnyEvent::AIO> for
		918	a case where this is useful.
		919
		920	Example: Create a watcher for the IO::AIO module and store it in
		921	C<$WATCHER>. Only do so after the event loop is initialised, though.
		922
		923	our WATCHER;
		924
		925	my $guard = AnyEvent::post_detect {
		926	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		927	};
		928
		929	# the ||= is important in case post_detect immediately runs the block,
		930	# as to not clobber the newly-created watcher. assigning both watcher and
		931	# post_detect guard to the same variable has the advantage of users being
		932	# able to just C<undef $WATCHER> if the watcher causes them grief.
		933
		934	$WATCHER ||= $guard;
		935
		936	=item @AnyEvent::post_detect
		937
		938	If there are any code references in this array (you can C<push> to it
		939	before or after loading AnyEvent), then they will called directly after
		940	the event loop has been chosen.
		941
		942	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		943	if it is defined then the event loop has already been detected, and the
		944	array will be ignored.
		945
		946	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		947	it,as it takes care of these details.
		948
		949	This variable is mainly useful for modules that can do something useful
		950	when AnyEvent is used and thus want to know when it is initialised, but do
		951	not need to even load it by default. This array provides the means to hook
		952	into AnyEvent passively, without loading it.
371		953
372	=back	954	=back
373		955
374	=head1 WHAT TO DO IN A MODULE	956	=head1 WHAT TO DO IN A MODULE
375		957
…		…
379	Be careful when you create watchers in the module body - AnyEvent will	961	Be careful when you create watchers in the module body - AnyEvent will
380	decide which event module to use as soon as the first method is called, so	962	decide which event module to use as soon as the first method is called, so
381	by calling AnyEvent in your module body you force the user of your module	963	by calling AnyEvent in your module body you force the user of your module
382	to load the event module first.	964	to load the event module first.
383		965
384	Never call C<< ->wait >> on a condition variable unless you I<know> that	966	Never call C<< ->recv >> on a condition variable unless you I<know> that
385	the C<< ->broadcast >> method has been called on it already. This is	967	the C<< ->send >> method has been called on it already. This is
386	because it will stall the whole program, and the whole point of using	968	because it will stall the whole program, and the whole point of using
387	events is to stay interactive.	969	events is to stay interactive.
388		970
389	It is fine, however, to call C<< ->wait >> when the user of your module	971	It is fine, however, to call C<< ->recv >> when the user of your module
390	requests it (i.e. if you create a http request object ad have a method	972	requests it (i.e. if you create a http request object ad have a method
391	called C<results> that returns the results, it should call C<< ->wait >>	973	called C<results> that returns the results, it should call C<< ->recv >>
392	freely, as the user of your module knows what she is doing. always).	974	freely, as the user of your module knows what she is doing. always).
393		975
394	=head1 WHAT TO DO IN THE MAIN PROGRAM	976	=head1 WHAT TO DO IN THE MAIN PROGRAM
395		977
396	There will always be a single main program - the only place that should	978	There will always be a single main program - the only place that should
…		…
398		980
399	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	981	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
400	do anything special (it does not need to be event-based) and let AnyEvent	982	do anything special (it does not need to be event-based) and let AnyEvent
401	decide which implementation to chose if some module relies on it.	983	decide which implementation to chose if some module relies on it.
402		984
403	If the main program relies on a specific event model. For example, in	985	If the main program relies on a specific event model - for example, in
404	Gtk2 programs you have to rely on the Glib module. You should load the	986	Gtk2 programs you have to rely on the Glib module - you should load the
405	event module before loading AnyEvent or any module that uses it: generally	987	event module before loading AnyEvent or any module that uses it: generally
406	speaking, you should load it as early as possible. The reason is that	988	speaking, you should load it as early as possible. The reason is that
407	modules might create watchers when they are loaded, and AnyEvent will	989	modules might create watchers when they are loaded, and AnyEvent will
408	decide on the event model to use as soon as it creates watchers, and it	990	decide on the event model to use as soon as it creates watchers, and it
409	might chose the wrong one unless you load the correct one yourself.	991	might chose the wrong one unless you load the correct one yourself.
410		992
411	You can chose to use a rather inefficient pure-perl implementation by	993	You can chose to use a pure-perl implementation by loading the
412	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	994	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
413	behaviour everywhere, but letting AnyEvent chose is generally better.	995	everywhere, but letting AnyEvent chose the model is generally better.
		996
		997	=head2 MAINLOOP EMULATION
		998
		999	Sometimes (often for short test scripts, or even standalone programs who
		1000	only want to use AnyEvent), you do not want to run a specific event loop.
		1001
		1002	In that case, you can use a condition variable like this:
		1003
		1004	AnyEvent->condvar->recv;
		1005
		1006	This has the effect of entering the event loop and looping forever.
		1007
		1008	Note that usually your program has some exit condition, in which case
		1009	it is better to use the "traditional" approach of storing a condition
		1010	variable somewhere, waiting for it, and sending it when the program should
		1011	exit cleanly.
		1012
		1013
		1014	=head1 OTHER MODULES
		1015
		1016	The following is a non-exhaustive list of additional modules that use
		1017	AnyEvent as a client and can therefore be mixed easily with other AnyEvent
		1018	modules and other event loops in the same program. Some of the modules
		1019	come with AnyEvent, most are available via CPAN.
		1020
		1021	=over 4
		1022
		1023	=item L<AnyEvent::Util>
		1024
		1025	Contains various utility functions that replace often-used but blocking
		1026	functions such as C<inet_aton> by event-/callback-based versions.
		1027
		1028	=item L<AnyEvent::Socket>
		1029
		1030	Provides various utility functions for (internet protocol) sockets,
		1031	addresses and name resolution. Also functions to create non-blocking tcp
		1032	connections or tcp servers, with IPv6 and SRV record support and more.
		1033
		1034	=item L<AnyEvent::Handle>
		1035
		1036	Provide read and write buffers, manages watchers for reads and writes,
		1037	supports raw and formatted I/O, I/O queued and fully transparent and
		1038	non-blocking SSL/TLS (via L<AnyEvent::TLS>.
		1039
		1040	=item L<AnyEvent::DNS>
		1041
		1042	Provides rich asynchronous DNS resolver capabilities.
		1043
		1044	=item L<AnyEvent::HTTP>
		1045
		1046	A simple-to-use HTTP library that is capable of making a lot of concurrent
		1047	HTTP requests.
		1048
		1049	=item L<AnyEvent::HTTPD>
		1050
		1051	Provides a simple web application server framework.
		1052
		1053	=item L<AnyEvent::FastPing>
		1054
		1055	The fastest ping in the west.
		1056
		1057	=item L<AnyEvent::DBI>
		1058
		1059	Executes L<DBI> requests asynchronously in a proxy process.
		1060
		1061	=item L<AnyEvent::AIO>
		1062
		1063	Truly asynchronous I/O, should be in the toolbox of every event
		1064	programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
		1065	together.
		1066
		1067	=item L<AnyEvent::BDB>
		1068
		1069	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
		1070	L<BDB> and AnyEvent together.
		1071
		1072	=item L<AnyEvent::GPSD>
		1073
		1074	A non-blocking interface to gpsd, a daemon delivering GPS information.
		1075
		1076	=item L<AnyEvent::IRC>
		1077
		1078	AnyEvent based IRC client module family (replacing the older Net::IRC3).
		1079
		1080	=item L<AnyEvent::XMPP>
		1081
		1082	AnyEvent based XMPP (Jabber protocol) module family (replacing the older
		1083	Net::XMPP2>.
		1084
		1085	=item L<AnyEvent::IGS>
		1086
		1087	A non-blocking interface to the Internet Go Server protocol (used by
		1088	L<App::IGS>).
		1089
		1090	=item L<Net::FCP>
		1091
		1092	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
		1093	of AnyEvent.
		1094
		1095	=item L<Event::ExecFlow>
		1096
		1097	High level API for event-based execution flow control.
		1098
		1099	=item L<Coro>
		1100
		1101	Has special support for AnyEvent via L<Coro::AnyEvent>.
		1102
		1103	=back
414		1104
415	=cut	1105	=cut
416		1106
417	package AnyEvent;	1107	package AnyEvent;
418		1108
419	no warnings;	1109	# basically a tuned-down version of common::sense
420	use strict;	1110	sub common_sense {
		1111	# from common:.sense 1.0
		1112	${^WARNING_BITS} = "\xfc\x3f\xf3\x00\x0f\xf3\xcf\xc0\xf3\xfc\x33\x03";
		1113	# use strict vars subs
		1114	$^H |= 0x00000600;
		1115	}
421		1116
		1117	BEGIN { AnyEvent::common_sense }
		1118
422	use Carp;	1119	use Carp ();
423		1120
424	our $VERSION = '3.12';	1121	our $VERSION = '5.202';
425	our $MODEL;	1122	our $MODEL;
426		1123
427	our $AUTOLOAD;	1124	our $AUTOLOAD;
428	our @ISA;	1125	our @ISA;
429		1126
430	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
431
432	our @REGISTRY;	1127	our @REGISTRY;
433		1128
		1129	our $WIN32;
		1130
		1131	our $VERBOSE;
		1132
		1133	BEGIN {
		1134	eval "sub WIN32(){ " . (($^O =~ /mswin32/i)*1) ." }";
		1135	eval "sub TAINT(){ " . (${^TAINT}*1) . " }";
		1136
		1137	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1138	if ${^TAINT};
		1139
		1140	$VERBOSE = $ENV{PERL_ANYEVENT_VERBOSE}*1;
		1141
		1142	}
		1143
		1144	our $MAX_SIGNAL_LATENCY = 10;
		1145
		1146	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		1147
		1148	{
		1149	my $idx;
		1150	$PROTOCOL{$_} = ++$idx
		1151	for reverse split /\s*,\s*/,
		1152	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		1153	}
		1154
434	my @models = (	1155	my @models = (
435	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
436	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
437	[EV:: => AnyEvent::Impl::EV::],	1156	[EV:: => AnyEvent::Impl::EV:: , 1],
		1157	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl:: , 1],
		1158	# everything below here will not (normally) be autoprobed
		1159	# as the pureperl backend should work everywhere
		1160	# and is usually faster
438	[Event:: => AnyEvent::Impl::Event::],	1161	[Event:: => AnyEvent::Impl::Event::, 1],
439	[Glib:: => AnyEvent::Impl::Glib::],	1162	[Glib:: => AnyEvent::Impl::Glib:: , 1], # becomes extremely slow with many watchers
		1163	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		1164	[Irssi:: => AnyEvent::Impl::Irssi::], # Irssi has a bogus "Event" package
		1165	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		1166	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		1167	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
440	[Tk:: => AnyEvent::Impl::Tk::],	1168	[Wx:: => AnyEvent::Impl::POE::],
441	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1169	[Prima:: => AnyEvent::Impl::POE::],
442	[Event::Lib:: => AnyEvent::Impl::EventLib::],	1170	# IO::Async is just too broken - we would need workarounds for its
		1171	# byzantine signal and broken child handling, among others.
		1172	# IO::Async is rather hard to detect, as it doesn't have any
		1173	# obvious default class.
		1174	[IO::Async:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1175	[IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1176	[IO::Async::Notifier:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1177	[AnyEvent::Impl::IOAsync:: => AnyEvent::Impl::IOAsync::], # requires special main program
443	);	1178	);
444		1179
445	our %method = map +($_ => 1), qw(io timer condvar broadcast wait signal one_event DESTROY);	1180	our %method = map +($_ => 1),
		1181	qw(io timer time now now_update signal child idle condvar one_event DESTROY);
		1182
		1183	our @post_detect;
		1184
		1185	sub post_detect(&) {
		1186	my ($cb) = @_;
		1187
		1188	if ($MODEL) {
		1189	$cb->();
		1190
		1191	undef
		1192	} else {
		1193	push @post_detect, $cb;
		1194
		1195	defined wantarray
		1196	? bless \$cb, "AnyEvent::Util::postdetect"
		1197	: ()
		1198	}
		1199	}
		1200
		1201	sub AnyEvent::Util::postdetect::DESTROY {
		1202	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		1203	}
446		1204
447	sub detect() {	1205	sub detect() {
448	unless ($MODEL) {	1206	unless ($MODEL) {
449	no strict 'refs';	1207	local $SIG{__DIE__};
450		1208
451	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	1209	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
452	my $model = "AnyEvent::Impl::$1";	1210	my $model = "AnyEvent::Impl::$1";
453	if (eval "require $model") {	1211	if (eval "require $model") {
454	$MODEL = $model;	1212	$MODEL = $model;
455	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	1213	warn "AnyEvent: loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.\n" if $VERBOSE >= 2;
		1214	} else {
		1215	warn "AnyEvent: unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@" if $VERBOSE;
456	}	1216	}
457	}	1217	}
458		1218
459	# check for already loaded models	1219	# check for already loaded models
460	unless ($MODEL) {	1220	unless ($MODEL) {
461	for (@REGISTRY, @models) {	1221	for (@REGISTRY, @models) {
462	my ($package, $model) = @$_;	1222	my ($package, $model) = @$_;
463	if (${"$package\::VERSION"} > 0) {	1223	if (${"$package\::VERSION"} > 0) {
464	if (eval "require $model") {	1224	if (eval "require $model") {
465	$MODEL = $model;	1225	$MODEL = $model;
466	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;	1226	warn "AnyEvent: autodetected model '$model', using it.\n" if $VERBOSE >= 2;
467	last;	1227	last;
468	}	1228	}
469	}	1229	}
470	}	1230	}
471		1231
472	unless ($MODEL) {	1232	unless ($MODEL) {
473	# try to load a model	1233	# try to autoload a model
474
475	for (@REGISTRY, @models) {	1234	for (@REGISTRY, @models) {
476	my ($package, $model) = @$_;	1235	my ($package, $model, $autoload) = @$_;
		1236	if (
		1237	$autoload
477	if (eval "require $package"	1238	and eval "require $package"
478	and ${"$package\::VERSION"} > 0	1239	and ${"$package\::VERSION"} > 0
479	and eval "require $model") {	1240	and eval "require $model"
		1241	) {
480	$MODEL = $model;	1242	$MODEL = $model;
481	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;	1243	warn "AnyEvent: autoloaded model '$model', using it.\n" if $VERBOSE >= 2;
482	last;	1244	last;
483	}	1245	}
484	}	1246	}
485		1247
486	$MODEL	1248	$MODEL
487	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV (or Coro+EV), Event (or Coro+Event) or Glib.";	1249	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.\n";
488	}	1250	}
489	}	1251	}
490		1252
		1253	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		1254
491	unshift @ISA, $MODEL;	1255	unshift @ISA, $MODEL;
492	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	1256
		1257	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
		1258
		1259	(shift @post_detect)->() while @post_detect;
493	}	1260	}
494		1261
495	$MODEL	1262	$MODEL
496	}	1263	}
497		1264
498	sub AUTOLOAD {	1265	sub AUTOLOAD {
499	(my $func = $AUTOLOAD) =~ s/.*://;	1266	(my $func = $AUTOLOAD) =~ s/.*://;
500		1267
501	$method{$func}	1268	$method{$func}
502	or croak "$func: not a valid method for AnyEvent objects";	1269	or Carp::croak "$func: not a valid method for AnyEvent objects";
503		1270
504	detect unless $MODEL;	1271	detect unless $MODEL;
505		1272
506	my $class = shift;	1273	my $class = shift;
507	$class->$func (@_);	1274	$class->$func (@_);
508	}	1275	}
509		1276
		1277	# utility function to dup a filehandle. this is used by many backends
		1278	# to support binding more than one watcher per filehandle (they usually
		1279	# allow only one watcher per fd, so we dup it to get a different one).
		1280	sub _dupfh($$;$$) {
		1281	my ($poll, $fh, $r, $w) = @_;
		1282
		1283	# cygwin requires the fh mode to be matching, unix doesn't
		1284	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1285
		1286	open my $fh2, $mode, $fh
		1287	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1288
		1289	# we assume CLOEXEC is already set by perl in all important cases
		1290
		1291	($fh2, $rw)
		1292	}
		1293
		1294	=head1 SIMPLIFIED AE API
		1295
		1296	Starting with version 5.0, AnyEvent officially supports a second, much
		1297	simpler, API that is designed to reduce the calling, typing and memory
		1298	overhead.
		1299
		1300	See the L<AE> manpage for details.
		1301
		1302	=cut
		1303
		1304	package AE;
		1305
		1306	our $VERSION = $AnyEvent::VERSION;
		1307
		1308	sub io($$$) {
		1309	AnyEvent->io (fh => $_[0], poll => $_[1] ? "w" : "r", cb => $_[2])
		1310	}
		1311
		1312	sub timer($$$) {
		1313	AnyEvent->timer (after => $_[0], interval => $_[1], cb => $_[2])
		1314	}
		1315
		1316	sub signal($$) {
		1317	AnyEvent->signal (signal => $_[0], cb => $_[1])
		1318	}
		1319
		1320	sub child($$) {
		1321	AnyEvent->child (pid => $_[0], cb => $_[1])
		1322	}
		1323
		1324	sub idle($) {
		1325	AnyEvent->idle (cb => $_[0])
		1326	}
		1327
		1328	sub cv(;&) {
		1329	AnyEvent->condvar (@_ ? (cb => $_[0]) : ())
		1330	}
		1331
		1332	sub now() {
		1333	AnyEvent->now
		1334	}
		1335
		1336	sub now_update() {
		1337	AnyEvent->now_update
		1338	}
		1339
		1340	sub time() {
		1341	AnyEvent->time
		1342	}
		1343
510	package AnyEvent::Base;	1344	package AnyEvent::Base;
511		1345
		1346	# default implementations for many methods
		1347
		1348	sub _time() {
		1349	# probe for availability of Time::HiRes
		1350	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1351	warn "AnyEvent: using Time::HiRes for sub-second timing accuracy.\n" if $VERBOSE >= 8;
		1352	*_time = \&Time::HiRes::time;
		1353	# if (eval "use POSIX (); (POSIX::times())...
		1354	} else {
		1355	warn "AnyEvent: using built-in time(), WARNING, no sub-second resolution!\n" if $VERBOSE;
		1356	*_time = sub { time }; # epic fail
		1357	}
		1358
		1359	&_time
		1360	}
		1361
		1362	sub time { _time }
		1363	sub now { _time }
		1364	sub now_update { }
		1365
512	# default implementation for ->condvar, ->wait, ->broadcast	1366	# default implementation for ->condvar
513		1367
514	sub condvar {	1368	sub condvar {
515	bless \my $flag, "AnyEvent::Base::CondVar"	1369	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
516	}
517
518	sub AnyEvent::Base::CondVar::broadcast {
519	${$_[0]}++;
520	}
521
522	sub AnyEvent::Base::CondVar::wait {
523	AnyEvent->one_event while !${$_[0]};
524	}	1370	}
525		1371
526	# default implementation for ->signal	1372	# default implementation for ->signal
527		1373
528	our %SIG_CB;	1374	our $HAVE_ASYNC_INTERRUPT;
		1375
		1376	sub _have_async_interrupt() {
		1377	$HAVE_ASYNC_INTERRUPT = 1*(!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT}
		1378	&& eval "use Async::Interrupt 1.02 (); 1")
		1379	unless defined $HAVE_ASYNC_INTERRUPT;
		1380
		1381	$HAVE_ASYNC_INTERRUPT
		1382	}
		1383
		1384	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1385	our (%SIG_ASY, %SIG_ASY_W);
		1386	our ($SIG_COUNT, $SIG_TW);
		1387
		1388	sub _signal_exec {
		1389	$HAVE_ASYNC_INTERRUPT
		1390	? $SIGPIPE_R->drain
		1391	: sysread $SIGPIPE_R, (my $dummy), 9;
		1392
		1393	while (%SIG_EV) {
		1394	for (keys %SIG_EV) {
		1395	delete $SIG_EV{$_};
		1396	$_->() for values %{ $SIG_CB{$_} || {} };
		1397	}
		1398	}
		1399	}
		1400
		1401	# install a dummy wakeup watcher to reduce signal catching latency
		1402	sub _sig_add() {
		1403	unless ($SIG_COUNT++) {
		1404	# try to align timer on a full-second boundary, if possible
		1405	my $NOW = AE::now;
		1406
		1407	$SIG_TW = AE::timer
		1408	$MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1409	$MAX_SIGNAL_LATENCY,
		1410	sub { } # just for the PERL_ASYNC_CHECK
		1411	;
		1412	}
		1413	}
		1414
		1415	sub _sig_del {
		1416	undef $SIG_TW
		1417	unless --$SIG_COUNT;
		1418	}
		1419
		1420	our $_sig_name_init; $_sig_name_init = sub {
		1421	eval q{ # poor man's autoloading
		1422	undef $_sig_name_init;
		1423
		1424	if (_have_async_interrupt) {
		1425	*sig2num = \&Async::Interrupt::sig2num;
		1426	*sig2name = \&Async::Interrupt::sig2name;
		1427	} else {
		1428	require Config;
		1429
		1430	my %signame2num;
		1431	@signame2num{ split ' ', $Config::Config{sig_name} }
		1432	= split ' ', $Config::Config{sig_num};
		1433
		1434	my @signum2name;
		1435	@signum2name[values %signame2num] = keys %signame2num;
		1436
		1437	*sig2num = sub($) {
		1438	$_[0] > 0 ? shift : $signame2num{+shift}
		1439	};
		1440	*sig2name = sub ($) {
		1441	$_[0] > 0 ? $signum2name[+shift] : shift
		1442	};
		1443	}
		1444	};
		1445	die if $@;
		1446	};
		1447
		1448	sub sig2num ($) { &$_sig_name_init; &sig2num }
		1449	sub sig2name($) { &$_sig_name_init; &sig2name }
529		1450
530	sub signal {	1451	sub signal {
		1452	eval q{ # poor man's autoloading {}
		1453	# probe for availability of Async::Interrupt
		1454	if (_have_async_interrupt) {
		1455	warn "AnyEvent: using Async::Interrupt for race-free signal handling.\n" if $VERBOSE >= 8;
		1456
		1457	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1458	$SIG_IO = AE::io $SIGPIPE_R->fileno, 0, \&_signal_exec;
		1459
		1460	} else {
		1461	warn "AnyEvent: using emulated perl signal handling with latency timer.\n" if $VERBOSE >= 8;
		1462
		1463	require Fcntl;
		1464
		1465	if (AnyEvent::WIN32) {
		1466	require AnyEvent::Util;
		1467
		1468	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1469	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R, 1) if $SIGPIPE_R;
		1470	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W, 1) if $SIGPIPE_W; # just in case
		1471	} else {
		1472	pipe $SIGPIPE_R, $SIGPIPE_W;
		1473	fcntl $SIGPIPE_R, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_R;
		1474	fcntl $SIGPIPE_W, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_W; # just in case
		1475
		1476	# not strictly required, as $^F is normally 2, but let's make sure...
		1477	fcntl $SIGPIPE_R, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1478	fcntl $SIGPIPE_W, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1479	}
		1480
		1481	$SIGPIPE_R
		1482	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1483
		1484	$SIG_IO = AE::io $SIGPIPE_R, 0, \&_signal_exec;
		1485	}
		1486
		1487	*signal = sub {
531	my (undef, %arg) = @_;	1488	my (undef, %arg) = @_;
532		1489
533	my $signal = uc $arg{signal}	1490	my $signal = uc $arg{signal}
534	or Carp::croak "required option 'signal' is missing";	1491	or Carp::croak "required option 'signal' is missing";
535		1492
		1493	if ($HAVE_ASYNC_INTERRUPT) {
		1494	# async::interrupt
		1495
		1496	$signal = sig2num $signal;
536	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1497	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1498
		1499	$SIG_ASY{$signal} ||= new Async::Interrupt
		1500	cb => sub { undef $SIG_EV{$signal} },
		1501	signal => $signal,
		1502	pipe => [$SIGPIPE_R->filenos],
		1503	pipe_autodrain => 0,
		1504	;
		1505
		1506	} else {
		1507	# pure perl
		1508
		1509	# AE::Util has been loaded in signal
		1510	$signal = sig2name $signal;
		1511	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1512
537	$SIG{$signal} ||= sub {	1513	$SIG{$signal} ||= sub {
538	$_->() for values %{ $SIG_CB{$signal} || {} };	1514	local $!;
		1515	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1516	undef $SIG_EV{$signal};
		1517	};
		1518
		1519	# can't do signal processing without introducing races in pure perl,
		1520	# so limit the signal latency.
		1521	_sig_add;
		1522	}
		1523
		1524	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1525	};
		1526
		1527	*AnyEvent::Base::signal::DESTROY = sub {
		1528	my ($signal, $cb) = @{$_[0]};
		1529
		1530	_sig_del;
		1531
		1532	delete $SIG_CB{$signal}{$cb};
		1533
		1534	$HAVE_ASYNC_INTERRUPT
		1535	? delete $SIG_ASY{$signal}
		1536	: # delete doesn't work with older perls - they then
		1537	# print weird messages, or just unconditionally exit
		1538	# instead of getting the default action.
		1539	undef $SIG{$signal}
		1540	unless keys %{ $SIG_CB{$signal} };
		1541	};
539	};	1542	};
540		1543	die if $@;
541	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1544	&signal
542	}
543
544	sub AnyEvent::Base::Signal::DESTROY {
545	my ($signal, $cb) = @{$_[0]};
546
547	delete $SIG_CB{$signal}{$cb};
548
549	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };
550	}	1545	}
551		1546
552	# default implementation for ->child	1547	# default implementation for ->child
553		1548
554	our %PID_CB;	1549	our %PID_CB;
555	our $CHLD_W;	1550	our $CHLD_W;
556	our $CHLD_DELAY_W;	1551	our $CHLD_DELAY_W;
557	our $PID_IDLE;
558	our $WNOHANG;	1552	our $WNOHANG;
559		1553
560	sub _child_wait {	1554	sub _emit_childstatus($$) {
561	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1555	my (undef, $rpid, $rstatus) = @_;
		1556
		1557	$_->($rpid, $rstatus)
562	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1558	for values %{ $PID_CB{$rpid} || {} },
563	(values %{ $PID_CB{0} || {} });	1559	values %{ $PID_CB{0} || {} };
564	}
565
566	undef $PID_IDLE;
567	}	1560	}
568		1561
569	sub _sigchld {	1562	sub _sigchld {
570	# make sure we deliver these changes "synchronous" with the event loop.	1563	my $pid;
571	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {	1564
572	undef $CHLD_DELAY_W;	1565	AnyEvent->_emit_childstatus ($pid, $?)
573	&_child_wait;	1566	while ($pid = waitpid -1, $WNOHANG) > 0;
574	});
575	}	1567	}
576		1568
577	sub child {	1569	sub child {
578	my (undef, %arg) = @_;	1570	my (undef, %arg) = @_;
579		1571
580	defined (my $pid = $arg{pid} + 0)	1572	defined (my $pid = $arg{pid} + 0)
581	or Carp::croak "required option 'pid' is missing";	1573	or Carp::croak "required option 'pid' is missing";
582		1574
583	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1575	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
584		1576
585	unless ($WNOHANG) {	1577	# WNOHANG is almost cetrainly 1 everywhere
586	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;	1578	$WNOHANG ||= $^O =~ /^(?:openbsd|netbsd|linux|freebsd|cygwin|MSWin32)$/
587	}	1579	? 1
		1580	: eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
588		1581
589	unless ($CHLD_W) {	1582	unless ($CHLD_W) {
590	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1583	$CHLD_W = AE::signal CHLD => \&_sigchld;
591	# child could be a zombie already, so make at least one round	1584	# child could be a zombie already, so make at least one round
592	&_sigchld;	1585	&_sigchld;
593	}	1586	}
594		1587
595	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	1588	bless [$pid, $arg{cb}], "AnyEvent::Base::child"
596	}	1589	}
597		1590
598	sub AnyEvent::Base::Child::DESTROY {	1591	sub AnyEvent::Base::child::DESTROY {
599	my ($pid, $cb) = @{$_[0]};	1592	my ($pid, $cb) = @{$_[0]};
600		1593
601	delete $PID_CB{$pid}{$cb};	1594	delete $PID_CB{$pid}{$cb};
602	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1595	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
603		1596
604	undef $CHLD_W unless keys %PID_CB;	1597	undef $CHLD_W unless keys %PID_CB;
605	}	1598	}
		1599
		1600	# idle emulation is done by simply using a timer, regardless
		1601	# of whether the process is idle or not, and not letting
		1602	# the callback use more than 50% of the time.
		1603	sub idle {
		1604	my (undef, %arg) = @_;
		1605
		1606	my ($cb, $w, $rcb) = $arg{cb};
		1607
		1608	$rcb = sub {
		1609	if ($cb) {
		1610	$w = _time;
		1611	&$cb;
		1612	$w = _time - $w;
		1613
		1614	# never use more then 50% of the time for the idle watcher,
		1615	# within some limits
		1616	$w = 0.0001 if $w < 0.0001;
		1617	$w = 5 if $w > 5;
		1618
		1619	$w = AE::timer $w, 0, $rcb;
		1620	} else {
		1621	# clean up...
		1622	undef $w;
		1623	undef $rcb;
		1624	}
		1625	};
		1626
		1627	$w = AE::timer 0.05, 0, $rcb;
		1628
		1629	bless \\$cb, "AnyEvent::Base::idle"
		1630	}
		1631
		1632	sub AnyEvent::Base::idle::DESTROY {
		1633	undef $${$_[0]};
		1634	}
		1635
		1636	package AnyEvent::CondVar;
		1637
		1638	our @ISA = AnyEvent::CondVar::Base::;
		1639
		1640	package AnyEvent::CondVar::Base;
		1641
		1642	#use overload
		1643	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1644	# fallback => 1;
		1645
		1646	# save 300+ kilobytes by dirtily hardcoding overloading
		1647	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1648	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1649	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1650	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1651
		1652	our $WAITING;
		1653
		1654	sub _send {
		1655	# nop
		1656	}
		1657
		1658	sub send {
		1659	my $cv = shift;
		1660	$cv->{_ae_sent} = [@_];
		1661	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1662	$cv->_send;
		1663	}
		1664
		1665	sub croak {
		1666	$_[0]{_ae_croak} = $_[1];
		1667	$_[0]->send;
		1668	}
		1669
		1670	sub ready {
		1671	$_[0]{_ae_sent}
		1672	}
		1673
		1674	sub _wait {
		1675	$WAITING
		1676	and !$_[0]{_ae_sent}
		1677	and Carp::croak "AnyEvent::CondVar: recursive blocking wait detected";
		1678
		1679	local $WAITING = 1;
		1680	AnyEvent->one_event while !$_[0]{_ae_sent};
		1681	}
		1682
		1683	sub recv {
		1684	$_[0]->_wait;
		1685
		1686	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
		1687	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
		1688	}
		1689
		1690	sub cb {
		1691	my $cv = shift;
		1692
		1693	@_
		1694	and $cv->{_ae_cb} = shift
		1695	and $cv->{_ae_sent}
		1696	and (delete $cv->{_ae_cb})->($cv);
		1697
		1698	$cv->{_ae_cb}
		1699	}
		1700
		1701	sub begin {
		1702	++$_[0]{_ae_counter};
		1703	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
		1704	}
		1705
		1706	sub end {
		1707	return if --$_[0]{_ae_counter};
		1708	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		1709	}
		1710
		1711	# undocumented/compatibility with pre-3.4
		1712	*broadcast = \&send;
		1713	*wait = \&_wait;
		1714
		1715	=head1 ERROR AND EXCEPTION HANDLING
		1716
		1717	In general, AnyEvent does not do any error handling - it relies on the
		1718	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1719	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1720	checking of all AnyEvent methods, however, which is highly useful during
		1721	development.
		1722
		1723	As for exception handling (i.e. runtime errors and exceptions thrown while
		1724	executing a callback), this is not only highly event-loop specific, but
		1725	also not in any way wrapped by this module, as this is the job of the main
		1726	program.
		1727
		1728	The pure perl event loop simply re-throws the exception (usually
		1729	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1730	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1731	so on.
		1732
		1733	=head1 ENVIRONMENT VARIABLES
		1734
		1735	The following environment variables are used by this module or its
		1736	submodules.
		1737
		1738	Note that AnyEvent will remove I<all> environment variables starting with
		1739	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		1740	enabled.
		1741
		1742	=over 4
		1743
		1744	=item C<PERL_ANYEVENT_VERBOSE>
		1745
		1746	By default, AnyEvent will be completely silent except in fatal
		1747	conditions. You can set this environment variable to make AnyEvent more
		1748	talkative.
		1749
		1750	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1751	conditions, such as not being able to load the event model specified by
		1752	C<PERL_ANYEVENT_MODEL>.
		1753
		1754	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1755	model it chooses.
		1756
		1757	When set to C<8> or higher, then AnyEvent will report extra information on
		1758	which optional modules it loads and how it implements certain features.
		1759
		1760	=item C<PERL_ANYEVENT_STRICT>
		1761
		1762	AnyEvent does not do much argument checking by default, as thorough
		1763	argument checking is very costly. Setting this variable to a true value
		1764	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1765	check the arguments passed to most method calls. If it finds any problems,
		1766	it will croak.
		1767
		1768	In other words, enables "strict" mode.
		1769
		1770	Unlike C<use strict> (or it's modern cousin, C<< use L<common::sense>
		1771	>>, it is definitely recommended to keep it off in production. Keeping
		1772	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		1773	can be very useful, however.
		1774
		1775	=item C<PERL_ANYEVENT_MODEL>
		1776
		1777	This can be used to specify the event model to be used by AnyEvent, before
		1778	auto detection and -probing kicks in. It must be a string consisting
		1779	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1780	and the resulting module name is loaded and if the load was successful,
		1781	used as event model. If it fails to load AnyEvent will proceed with
		1782	auto detection and -probing.
		1783
		1784	This functionality might change in future versions.
		1785
		1786	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1787	could start your program like this:
		1788
		1789	PERL_ANYEVENT_MODEL=Perl perl ...
		1790
		1791	=item C<PERL_ANYEVENT_PROTOCOLS>
		1792
		1793	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1794	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1795	of auto probing).
		1796
		1797	Must be set to a comma-separated list of protocols or address families,
		1798	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1799	used, and preference will be given to protocols mentioned earlier in the
		1800	list.
		1801
		1802	This variable can effectively be used for denial-of-service attacks
		1803	against local programs (e.g. when setuid), although the impact is likely
		1804	small, as the program has to handle conenction and other failures anyways.
		1805
		1806	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1807	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1808	- only support IPv4, never try to resolve or contact IPv6
		1809	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1810	IPv6, but prefer IPv6 over IPv4.
		1811
		1812	=item C<PERL_ANYEVENT_EDNS0>
		1813
		1814	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1815	for DNS. This extension is generally useful to reduce DNS traffic, but
		1816	some (broken) firewalls drop such DNS packets, which is why it is off by
		1817	default.
		1818
		1819	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1820	EDNS0 in its DNS requests.
		1821
		1822	=item C<PERL_ANYEVENT_MAX_FORKS>
		1823
		1824	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1825	will create in parallel.
		1826
		1827	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		1828
		1829	The default value for the C<max_outstanding> parameter for the default DNS
		1830	resolver - this is the maximum number of parallel DNS requests that are
		1831	sent to the DNS server.
		1832
		1833	=item C<PERL_ANYEVENT_RESOLV_CONF>
		1834
		1835	The file to use instead of F</etc/resolv.conf> (or OS-specific
		1836	configuration) in the default resolver. When set to the empty string, no
		1837	default config will be used.
		1838
		1839	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		1840
		1841	When neither C<ca_file> nor C<ca_path> was specified during
		1842	L<AnyEvent::TLS> context creation, and either of these environment
		1843	variables exist, they will be used to specify CA certificate locations
		1844	instead of a system-dependent default.
		1845
		1846	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		1847
		1848	When these are set to C<1>, then the respective modules are not
		1849	loaded. Mostly good for testing AnyEvent itself.
		1850
		1851	=back
606		1852
607	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1853	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
608		1854
609	This is an advanced topic that you do not normally need to use AnyEvent in	1855	This is an advanced topic that you do not normally need to use AnyEvent in
610	a module. This section is only of use to event loop authors who want to	1856	a module. This section is only of use to event loop authors who want to
…		…
645	I<rxvt-unicode> also cheats a bit by not providing blocking access to	1891	I<rxvt-unicode> also cheats a bit by not providing blocking access to
646	condition variables: code blocking while waiting for a condition will	1892	condition variables: code blocking while waiting for a condition will
647	C<die>. This still works with most modules/usages, and blocking calls must	1893	C<die>. This still works with most modules/usages, and blocking calls must
648	not be done in an interactive application, so it makes sense.	1894	not be done in an interactive application, so it makes sense.
649		1895
650	=head1 ENVIRONMENT VARIABLES
651
652	The following environment variables are used by this module:
653
654	=over 4
655
656	=item C<PERL_ANYEVENT_VERBOSE>
657
658	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
659	model it chooses.
660
661	=item C<PERL_ANYEVENT_MODEL>
662
663	This can be used to specify the event model to be used by AnyEvent, before
664	autodetection and -probing kicks in. It must be a string consisting
665	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
666	and the resulting module name is loaded and if the load was successful,
667	used as event model. If it fails to load AnyEvent will proceed with
668	autodetection and -probing.
669
670	This functionality might change in future versions.
671
672	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
673	could start your program like this:
674
675	PERL_ANYEVENT_MODEL=Perl perl ...
676
677	=back
678
679	=head1 EXAMPLE PROGRAM	1896	=head1 EXAMPLE PROGRAM
680		1897
681	The following program uses an IO watcher to read data from STDIN, a timer	1898	The following program uses an I/O watcher to read data from STDIN, a timer
682	to display a message once per second, and a condition variable to quit the	1899	to display a message once per second, and a condition variable to quit the
683	program when the user enters quit:	1900	program when the user enters quit:
684		1901
685	use AnyEvent;	1902	use AnyEvent;
686		1903
…		…
691	poll => 'r',	1908	poll => 'r',
692	cb => sub {	1909	cb => sub {
693	warn "io event <$_[0]>\n"; # will always output <r>	1910	warn "io event <$_[0]>\n"; # will always output <r>
694	chomp (my $input = <STDIN>); # read a line	1911	chomp (my $input = <STDIN>); # read a line
695	warn "read: $input\n"; # output what has been read	1912	warn "read: $input\n"; # output what has been read
696	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	1913	$cv->send if $input =~ /^q/i; # quit program if /^q/i
697	},	1914	},
698	);	1915	);
699		1916
700	my $time_watcher; # can only be used once
701
702	sub new_timer {
703	$timer = AnyEvent->timer (after => 1, cb => sub {	1917	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
704	warn "timeout\n"; # print 'timeout' about every second	1918	warn "timeout\n"; # print 'timeout' at most every second
705	&new_timer; # and restart the time
706	});	1919	});
707	}
708		1920
709	new_timer; # create first timer
710
711	$cv->wait; # wait until user enters /^q/i	1921	$cv->recv; # wait until user enters /^q/i
712		1922
713	=head1 REAL-WORLD EXAMPLE	1923	=head1 REAL-WORLD EXAMPLE
714		1924
715	Consider the L<Net::FCP> module. It features (among others) the following	1925	Consider the L<Net::FCP> module. It features (among others) the following
716	API calls, which are to freenet what HTTP GET requests are to http:	1926	API calls, which are to freenet what HTTP GET requests are to http:
…		…
766	syswrite $txn->{fh}, $txn->{request}	1976	syswrite $txn->{fh}, $txn->{request}
767	or die "connection or write error";	1977	or die "connection or write error";
768	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	1978	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
769		1979
770	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	1980	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
771	result and signals any possible waiters that the request ahs finished:	1981	result and signals any possible waiters that the request has finished:
772		1982
773	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	1983	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
774		1984
775	if (end-of-file or data complete) {	1985	if (end-of-file or data complete) {
776	$txn->{result} = $txn->{buf};	1986	$txn->{result} = $txn->{buf};
777	$txn->{finished}->broadcast;	1987	$txn->{finished}->send;
778	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	1988	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
779	}	1989	}
780		1990
781	The C<result> method, finally, just waits for the finished signal (if the	1991	The C<result> method, finally, just waits for the finished signal (if the
782	request was already finished, it doesn't wait, of course, and returns the	1992	request was already finished, it doesn't wait, of course, and returns the
783	data:	1993	data:
784		1994
785	$txn->{finished}->wait;	1995	$txn->{finished}->recv;
786	return $txn->{result};	1996	return $txn->{result};
787		1997
788	The actual code goes further and collects all errors (C<die>s, exceptions)	1998	The actual code goes further and collects all errors (C<die>s, exceptions)
789	that occured during request processing. The C<result> method detects	1999	that occurred during request processing. The C<result> method detects
790	whether an exception as thrown (it is stored inside the $txn object)	2000	whether an exception as thrown (it is stored inside the $txn object)
791	and just throws the exception, which means connection errors and other	2001	and just throws the exception, which means connection errors and other
792	problems get reported tot he code that tries to use the result, not in a	2002	problems get reported tot he code that tries to use the result, not in a
793	random callback.	2003	random callback.
794		2004
…		…
825		2035
826	my $quit = AnyEvent->condvar;	2036	my $quit = AnyEvent->condvar;
827		2037
828	$fcp->txn_client_get ($url)->cb (sub {	2038	$fcp->txn_client_get ($url)->cb (sub {
829	...	2039	...
830	$quit->broadcast;	2040	$quit->send;
831	});	2041	});
832		2042
833	$quit->wait;	2043	$quit->recv;
		2044
		2045
		2046	=head1 BENCHMARKS
		2047
		2048	To give you an idea of the performance and overheads that AnyEvent adds
		2049	over the event loops themselves and to give you an impression of the speed
		2050	of various event loops I prepared some benchmarks.
		2051
		2052	=head2 BENCHMARKING ANYEVENT OVERHEAD
		2053
		2054	Here is a benchmark of various supported event models used natively and
		2055	through AnyEvent. The benchmark creates a lot of timers (with a zero
		2056	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
		2057	which it is), lets them fire exactly once and destroys them again.
		2058
		2059	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
		2060	distribution. It uses the L<AE> interface, which makes a real difference
		2061	for the EV and Perl backends only.
		2062
		2063	=head3 Explanation of the columns
		2064
		2065	I<watcher> is the number of event watchers created/destroyed. Since
		2066	different event models feature vastly different performances, each event
		2067	loop was given a number of watchers so that overall runtime is acceptable
		2068	and similar between tested event loop (and keep them from crashing): Glib
		2069	would probably take thousands of years if asked to process the same number
		2070	of watchers as EV in this benchmark.
		2071
		2072	I<bytes> is the number of bytes (as measured by the resident set size,
		2073	RSS) consumed by each watcher. This method of measuring captures both C
		2074	and Perl-based overheads.
		2075
		2076	I<create> is the time, in microseconds (millionths of seconds), that it
		2077	takes to create a single watcher. The callback is a closure shared between
		2078	all watchers, to avoid adding memory overhead. That means closure creation
		2079	and memory usage is not included in the figures.
		2080
		2081	I<invoke> is the time, in microseconds, used to invoke a simple
		2082	callback. The callback simply counts down a Perl variable and after it was
		2083	invoked "watcher" times, it would C<< ->send >> a condvar once to
		2084	signal the end of this phase.
		2085
		2086	I<destroy> is the time, in microseconds, that it takes to destroy a single
		2087	watcher.
		2088
		2089	=head3 Results
		2090
		2091	name watchers bytes create invoke destroy comment
		2092	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
		2093	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
		2094	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
		2095	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
		2096	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
		2097	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
		2098	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
		2099	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
		2100	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
		2101	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
		2102	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
		2103	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
		2104
		2105	=head3 Discussion
		2106
		2107	The benchmark does I<not> measure scalability of the event loop very
		2108	well. For example, a select-based event loop (such as the pure perl one)
		2109	can never compete with an event loop that uses epoll when the number of
		2110	file descriptors grows high. In this benchmark, all events become ready at
		2111	the same time, so select/poll-based implementations get an unnatural speed
		2112	boost.
		2113
		2114	Also, note that the number of watchers usually has a nonlinear effect on
		2115	overall speed, that is, creating twice as many watchers doesn't take twice
		2116	the time - usually it takes longer. This puts event loops tested with a
		2117	higher number of watchers at a disadvantage.
		2118
		2119	To put the range of results into perspective, consider that on the
		2120	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		2121	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		2122	cycles with POE.
		2123
		2124	C<EV> is the sole leader regarding speed and memory use, which are both
		2125	maximal/minimal, respectively. When using the L<AE> API there is zero
		2126	overhead (when going through the AnyEvent API create is about 5-6 times
		2127	slower, with other times being equal, so still uses far less memory than
		2128	any other event loop and is still faster than Event natively).
		2129
		2130	The pure perl implementation is hit in a few sweet spots (both the
		2131	constant timeout and the use of a single fd hit optimisations in the perl
		2132	interpreter and the backend itself). Nevertheless this shows that it
		2133	adds very little overhead in itself. Like any select-based backend its
		2134	performance becomes really bad with lots of file descriptors (and few of
		2135	them active), of course, but this was not subject of this benchmark.
		2136
		2137	The C<Event> module has a relatively high setup and callback invocation
		2138	cost, but overall scores in on the third place.
		2139
		2140	C<IO::Async> performs admirably well, about on par with C<Event>, even
		2141	when using its pure perl backend.
		2142
		2143	C<Glib>'s memory usage is quite a bit higher, but it features a
		2144	faster callback invocation and overall ends up in the same class as
		2145	C<Event>. However, Glib scales extremely badly, doubling the number of
		2146	watchers increases the processing time by more than a factor of four,
		2147	making it completely unusable when using larger numbers of watchers
		2148	(note that only a single file descriptor was used in the benchmark, so
		2149	inefficiencies of C<poll> do not account for this).
		2150
		2151	The C<Tk> adaptor works relatively well. The fact that it crashes with
		2152	more than 2000 watchers is a big setback, however, as correctness takes
		2153	precedence over speed. Nevertheless, its performance is surprising, as the
		2154	file descriptor is dup()ed for each watcher. This shows that the dup()
		2155	employed by some adaptors is not a big performance issue (it does incur a
		2156	hidden memory cost inside the kernel which is not reflected in the figures
		2157	above).
		2158
		2159	C<POE>, regardless of underlying event loop (whether using its pure perl
		2160	select-based backend or the Event module, the POE-EV backend couldn't
		2161	be tested because it wasn't working) shows abysmal performance and
		2162	memory usage with AnyEvent: Watchers use almost 30 times as much memory
		2163	as EV watchers, and 10 times as much memory as Event (the high memory
		2164	requirements are caused by requiring a session for each watcher). Watcher
		2165	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		2166	implementation.
		2167
		2168	The design of the POE adaptor class in AnyEvent can not really account
		2169	for the performance issues, though, as session creation overhead is
		2170	small compared to execution of the state machine, which is coded pretty
		2171	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		2172	using multiple sessions is not a good approach, especially regarding
		2173	memory usage, even the author of POE could not come up with a faster
		2174	design).
		2175
		2176	=head3 Summary
		2177
		2178	=over 4
		2179
		2180	=item * Using EV through AnyEvent is faster than any other event loop
		2181	(even when used without AnyEvent), but most event loops have acceptable
		2182	performance with or without AnyEvent.
		2183
		2184	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
		2185	the actual event loop, only with extremely fast event loops such as EV
		2186	adds AnyEvent significant overhead.
		2187
		2188	=item * You should avoid POE like the plague if you want performance or
		2189	reasonable memory usage.
		2190
		2191	=back
		2192
		2193	=head2 BENCHMARKING THE LARGE SERVER CASE
		2194
		2195	This benchmark actually benchmarks the event loop itself. It works by
		2196	creating a number of "servers": each server consists of a socket pair, a
		2197	timeout watcher that gets reset on activity (but never fires), and an I/O
		2198	watcher waiting for input on one side of the socket. Each time the socket
		2199	watcher reads a byte it will write that byte to a random other "server".
		2200
		2201	The effect is that there will be a lot of I/O watchers, only part of which
		2202	are active at any one point (so there is a constant number of active
		2203	fds for each loop iteration, but which fds these are is random). The
		2204	timeout is reset each time something is read because that reflects how
		2205	most timeouts work (and puts extra pressure on the event loops).
		2206
		2207	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
		2208	(1%) are active. This mirrors the activity of large servers with many
		2209	connections, most of which are idle at any one point in time.
		2210
		2211	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		2212	distribution. It uses the L<AE> interface, which makes a real difference
		2213	for the EV and Perl backends only.
		2214
		2215	=head3 Explanation of the columns
		2216
		2217	I<sockets> is the number of sockets, and twice the number of "servers" (as
		2218	each server has a read and write socket end).
		2219
		2220	I<create> is the time it takes to create a socket pair (which is
		2221	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		2222
		2223	I<request>, the most important value, is the time it takes to handle a
		2224	single "request", that is, reading the token from the pipe and forwarding
		2225	it to another server. This includes deleting the old timeout and creating
		2226	a new one that moves the timeout into the future.
		2227
		2228	=head3 Results
		2229
		2230	name sockets create request
		2231	EV 20000 62.66 7.99
		2232	Perl 20000 68.32 32.64
		2233	IOAsync 20000 174.06 101.15 epoll
		2234	IOAsync 20000 174.67 610.84 poll
		2235	Event 20000 202.69 242.91
		2236	Glib 20000 557.01 1689.52
		2237	POE 20000 341.54 12086.32 uses POE::Loop::Event
		2238
		2239	=head3 Discussion
		2240
		2241	This benchmark I<does> measure scalability and overall performance of the
		2242	particular event loop.
		2243
		2244	EV is again fastest. Since it is using epoll on my system, the setup time
		2245	is relatively high, though.
		2246
		2247	Perl surprisingly comes second. It is much faster than the C-based event
		2248	loops Event and Glib.
		2249
		2250	IO::Async performs very well when using its epoll backend, and still quite
		2251	good compared to Glib when using its pure perl backend.
		2252
		2253	Event suffers from high setup time as well (look at its code and you will
		2254	understand why). Callback invocation also has a high overhead compared to
		2255	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		2256	uses select or poll in basically all documented configurations.
		2257
		2258	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		2259	clearly fails to perform with many filehandles or in busy servers.
		2260
		2261	POE is still completely out of the picture, taking over 1000 times as long
		2262	as EV, and over 100 times as long as the Perl implementation, even though
		2263	it uses a C-based event loop in this case.
		2264
		2265	=head3 Summary
		2266
		2267	=over 4
		2268
		2269	=item * The pure perl implementation performs extremely well.
		2270
		2271	=item * Avoid Glib or POE in large projects where performance matters.
		2272
		2273	=back
		2274
		2275	=head2 BENCHMARKING SMALL SERVERS
		2276
		2277	While event loops should scale (and select-based ones do not...) even to
		2278	large servers, most programs we (or I :) actually write have only a few
		2279	I/O watchers.
		2280
		2281	In this benchmark, I use the same benchmark program as in the large server
		2282	case, but it uses only eight "servers", of which three are active at any
		2283	one time. This should reflect performance for a small server relatively
		2284	well.
		2285
		2286	The columns are identical to the previous table.
		2287
		2288	=head3 Results
		2289
		2290	name sockets create request
		2291	EV 16 20.00 6.54
		2292	Perl 16 25.75 12.62
		2293	Event 16 81.27 35.86
		2294	Glib 16 32.63 15.48
		2295	POE 16 261.87 276.28 uses POE::Loop::Event
		2296
		2297	=head3 Discussion
		2298
		2299	The benchmark tries to test the performance of a typical small
		2300	server. While knowing how various event loops perform is interesting, keep
		2301	in mind that their overhead in this case is usually not as important, due
		2302	to the small absolute number of watchers (that is, you need efficiency and
		2303	speed most when you have lots of watchers, not when you only have a few of
		2304	them).
		2305
		2306	EV is again fastest.
		2307
		2308	Perl again comes second. It is noticeably faster than the C-based event
		2309	loops Event and Glib, although the difference is too small to really
		2310	matter.
		2311
		2312	POE also performs much better in this case, but is is still far behind the
		2313	others.
		2314
		2315	=head3 Summary
		2316
		2317	=over 4
		2318
		2319	=item * C-based event loops perform very well with small number of
		2320	watchers, as the management overhead dominates.
		2321
		2322	=back
		2323
		2324	=head2 THE IO::Lambda BENCHMARK
		2325
		2326	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2327	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2328	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2329	shouldn't come as a surprise to anybody). As such, the benchmark is
		2330	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2331	very optimal. But how would AnyEvent compare when used without the extra
		2332	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2333
		2334	The benchmark itself creates an echo-server, and then, for 500 times,
		2335	connects to the echo server, sends a line, waits for the reply, and then
		2336	creates the next connection. This is a rather bad benchmark, as it doesn't
		2337	test the efficiency of the framework or much non-blocking I/O, but it is a
		2338	benchmark nevertheless.
		2339
		2340	name runtime
		2341	Lambda/select 0.330 sec
		2342	+ optimized 0.122 sec
		2343	Lambda/AnyEvent 0.327 sec
		2344	+ optimized 0.138 sec
		2345	Raw sockets/select 0.077 sec
		2346	POE/select, components 0.662 sec
		2347	POE/select, raw sockets 0.226 sec
		2348	POE/select, optimized 0.404 sec
		2349
		2350	AnyEvent/select/nb 0.085 sec
		2351	AnyEvent/EV/nb 0.068 sec
		2352	+state machine 0.134 sec
		2353
		2354	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2355	benchmarks actually make blocking connects and use 100% blocking I/O,
		2356	defeating the purpose of an event-based solution. All of the newly
		2357	written AnyEvent benchmarks use 100% non-blocking connects (using
		2358	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2359	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2360	generally require a lot more bookkeeping and event handling than blocking
		2361	connects (which involve a single syscall only).
		2362
		2363	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2364	offers similar expressive power as POE and IO::Lambda, using conventional
		2365	Perl syntax. This means that both the echo server and the client are 100%
		2366	non-blocking, further placing it at a disadvantage.
		2367
		2368	As you can see, the AnyEvent + EV combination even beats the
		2369	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2370	backend easily beats IO::Lambda and POE.
		2371
		2372	And even the 100% non-blocking version written using the high-level (and
		2373	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda
		2374	higher level ("unoptimised") abstractions by a large margin, even though
		2375	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
		2376
		2377	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2378	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2379	part of the IO::Lambda distribution and were used without any changes.
		2380
		2381
		2382	=head1 SIGNALS
		2383
		2384	AnyEvent currently installs handlers for these signals:
		2385
		2386	=over 4
		2387
		2388	=item SIGCHLD
		2389
		2390	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2391	emulation for event loops that do not support them natively. Also, some
		2392	event loops install a similar handler.
		2393
		2394	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2395	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2396
		2397	=item SIGPIPE
		2398
		2399	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2400	when AnyEvent gets loaded.
		2401
		2402	The rationale for this is that AnyEvent users usually do not really depend
		2403	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2404	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2405	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2406	some random socket.
		2407
		2408	The rationale for installing a no-op handler as opposed to ignoring it is
		2409	that this way, the handler will be restored to defaults on exec.
		2410
		2411	Feel free to install your own handler, or reset it to defaults.
		2412
		2413	=back
		2414
		2415	=cut
		2416
		2417	undef $SIG{CHLD}
		2418	if $SIG{CHLD} eq 'IGNORE';
		2419
		2420	$SIG{PIPE} = sub { }
		2421	unless defined $SIG{PIPE};
		2422
		2423	=head1 RECOMMENDED/OPTIONAL MODULES
		2424
		2425	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2426	it's built-in modules) are required to use it.
		2427
		2428	That does not mean that AnyEvent won't take advantage of some additional
		2429	modules if they are installed.
		2430
		2431	This section epxlains which additional modules will be used, and how they
		2432	affect AnyEvent's operetion.
		2433
		2434	=over 4
		2435
		2436	=item L<Async::Interrupt>
		2437
		2438	This slightly arcane module is used to implement fast signal handling: To
		2439	my knowledge, there is no way to do completely race-free and quick
		2440	signal handling in pure perl. To ensure that signals still get
		2441	delivered, AnyEvent will start an interval timer to wake up perl (and
		2442	catch the signals) with some delay (default is 10 seconds, look for
		2443	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2444
		2445	If this module is available, then it will be used to implement signal
		2446	catching, which means that signals will not be delayed, and the event loop
		2447	will not be interrupted regularly, which is more efficient (And good for
		2448	battery life on laptops).
		2449
		2450	This affects not just the pure-perl event loop, but also other event loops
		2451	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2452
		2453	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2454	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2455	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2456	does nothing for those backends.
		2457
		2458	=item L<EV>
		2459
		2460	This module isn't really "optional", as it is simply one of the backend
		2461	event loops that AnyEvent can use. However, it is simply the best event
		2462	loop available in terms of features, speed and stability: It supports
		2463	the AnyEvent API optimally, implements all the watcher types in XS, does
		2464	automatic timer adjustments even when no monotonic clock is available,
		2465	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2466	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2467	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2468
		2469	=item L<Guard>
		2470
		2471	The guard module, when used, will be used to implement
		2472	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2473	lot less memory), but otherwise doesn't affect guard operation much. It is
		2474	purely used for performance.
		2475
		2476	=item L<JSON> and L<JSON::XS>
		2477
		2478	One of these modules is required when you want to read or write JSON data
		2479	via L<AnyEvent::Handle>. It is also written in pure-perl, but can take
		2480	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2481
		2482	In fact, L<AnyEvent::Handle> will use L<JSON::XS> by default if it is
		2483	installed.
		2484
		2485	=item L<Net::SSLeay>
		2486
		2487	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2488	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2489	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2490
		2491	=item L<Time::HiRes>
		2492
		2493	This module is part of perl since release 5.008. It will be used when the
		2494	chosen event library does not come with a timing source on it's own. The
		2495	pure-perl event loop (L<AnyEvent::Impl::Perl>) will additionally use it to
		2496	try to use a monotonic clock for timing stability.
		2497
		2498	=back
		2499
834		2500
835	=head1 FORK	2501	=head1 FORK
836		2502
837	Most event libraries are not fork-safe. The ones who are usually are	2503	Most event libraries are not fork-safe. The ones who are usually are
838	because they are so inefficient. Only L<EV> is fully fork-aware.	2504	because they rely on inefficient but fork-safe C<select> or C<poll>
		2505	calls. Only L<EV> is fully fork-aware.
839		2506
840	If you have to fork, you must either do so I<before> creating your first	2507	If you have to fork, you must either do so I<before> creating your first
841	watcher OR you must not use AnyEvent at all in the child.	2508	watcher OR you must not use AnyEvent at all in the child OR you must do
		2509	something completely out of the scope of AnyEvent.
		2510
842		2511
843	=head1 SECURITY CONSIDERATIONS	2512	=head1 SECURITY CONSIDERATIONS
844		2513
845	AnyEvent can be forced to load any event model via	2514	AnyEvent can be forced to load any event model via
846	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to	2515	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
…		…
850	specified in the variable.	2519	specified in the variable.
851		2520
852	You can make AnyEvent completely ignore this variable by deleting it	2521	You can make AnyEvent completely ignore this variable by deleting it
853	before the first watcher gets created, e.g. with a C<BEGIN> block:	2522	before the first watcher gets created, e.g. with a C<BEGIN> block:
854		2523
855	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	2524	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
856		2525
857	use AnyEvent;	2526	use AnyEvent;
		2527
		2528	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		2529	be used to probe what backend is used and gain other information (which is
		2530	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2531	$ENV{PERL_ANYEVENT_STRICT}.
		2532
		2533	Note that AnyEvent will remove I<all> environment variables starting with
		2534	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2535	enabled.
		2536
		2537
		2538	=head1 BUGS
		2539
		2540	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2541	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2542	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2543	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2544	pronounced).
		2545
858		2546
859	=head1 SEE ALSO	2547	=head1 SEE ALSO
860		2548
861	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	2549	Utility functions: L<AnyEvent::Util>.
862	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,
863	L<Event::Lib>.
864		2550
865	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	2551	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
		2552	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
		2553
		2554	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
		2555	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
		2556	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
866	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,	2557	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>, L<Anyevent::Impl::Irssi>.
867	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>.
868		2558
		2559	Non-blocking file handles, sockets, TCP clients and
		2560	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
		2561
		2562	Asynchronous DNS: L<AnyEvent::DNS>.
		2563
		2564	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>,
		2565	L<Coro::Event>,
		2566
869	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	2567	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::XMPP>,
		2568	L<AnyEvent::HTTP>.
		2569
870		2570
871	=head1 AUTHOR	2571	=head1 AUTHOR
872		2572
873	Marc Lehmann <schmorp@schmorp.de>	2573	Marc Lehmann <schmorp@schmorp.de>
874	http://home.schmorp.de/	2574	http://home.schmorp.de/
875		2575
876	=cut	2576	=cut
877		2577
878	1	2578	1
879		2579

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