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Revision 1.266 by root, Thu Jul 30 03:41:56 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, Qt, POE - 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<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,	122	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,
86	L<POE>. The first one found is used. If none are found, the module tries	123	L<POE>. The first one found is used. If none are found, the module tries
87	to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl	124	to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl
88	adaptor should always succeed) in the order given. The first one that can	125	adaptor should always succeed) in the order given. The first one that can
89	be successfully loaded will be used. If, after this, still none could be	126	be successfully loaded will be used. If, after this, still none could be
…		…
103	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
104	use AnyEvent so their modules work together with others seamlessly...	141	use AnyEvent so their modules work together with others seamlessly...
105		142
106	The pure-perl implementation of AnyEvent is called	143	The pure-perl implementation of AnyEvent is called
107	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
108	explicitly.	145	explicitly and enjoy the high availability of that event loop :)
109		146
110	=head1 WATCHERS	147	=head1 WATCHERS
111		148
112	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
113	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
114	the callback to call, the filehandle to watch, etc.	151	the callback to call, the file handle to watch, etc.
115		152
116	These watchers are normal Perl objects with normal Perl lifetime. After	153	These watchers are normal Perl objects with normal Perl lifetime. After
117	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
118	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
119	is in control).	156	is in control).
120		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
121	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
122	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
123	to it).	166	to it).
124		167
125	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.
…		…
127	Many watchers either are used with "recursion" (repeating timers for	170	Many watchers either are used with "recursion" (repeating timers for
128	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.
129		172
130	An any way to achieve that is this pattern:	173	An any way to achieve that is this pattern:
131		174
132	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	175	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
133	# you can use $w here, for example to undef it	176	# you can use $w here, for example to undef it
134	undef $w;	177	undef $w;
135	});	178	});
136		179
137	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,
138	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
139	declared.	182	declared.
140		183
141	=head2 I/O WATCHERS	184	=head2 I/O WATCHERS
142		185
		186	$w = AnyEvent->io (
		187	fh => <filehandle_or_fileno>,
		188	poll => <"r" or "w">,
		189	cb => <callback>,
		190	);
		191
143	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
144	with the following mandatory key-value pairs as arguments:	193	with the following mandatory key-value pairs as arguments:
145		194
146	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch	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
147	for events. C<poll> must be a string that is either C<r> or C<w>,	202	C<poll> must be a string that is either C<r> or C<w>, which creates a
148	which creates a watcher waiting for "r"eadable or "w"ritable events,	203	watcher waiting for "r"eadable or "w"ritable events, respectively.
		204
149	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.
150	becomes ready.
151		206
152	Although the callback might get passed parameters, their value and	207	Although the callback might get passed parameters, their value and
153	presence is undefined and you cannot rely on them. Portable AnyEvent	208	presence is undefined and you cannot rely on them. Portable AnyEvent
154	callbacks cannot use arguments passed to I/O watcher callbacks.	209	callbacks cannot use arguments passed to I/O watcher callbacks.
155		210
…		…
159		214
160	Some event loops issue spurious readyness notifications, so you should	215	Some event loops issue spurious readyness notifications, so you should
161	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
162	handles.	217	handles.
163		218
164	Example:
165
166	# 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
167	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	222	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
168	chomp (my $input = <STDIN>);	223	chomp (my $input = <STDIN>);
169	warn "read: $input\n";	224	warn "read: $input\n";
170	undef $w;	225	undef $w;
171	});	226	});
172		227
173	=head2 TIME WATCHERS	228	=head2 TIME WATCHERS
174		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
175	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 >>
176	method with the following mandatory arguments:	239	method with the following mandatory arguments:
177		240
178	C<after> specifies after how many seconds (fractional values are	241	C<after> specifies after how many seconds (fractional values are
179	supported) the callback should be invoked. C<cb> is the callback to invoke	242	supported) the callback should be invoked. C<cb> is the callback to invoke
…		…
181		244
182	Although the callback might get passed parameters, their value and	245	Although the callback might get passed parameters, their value and
183	presence is undefined and you cannot rely on them. Portable AnyEvent	246	presence is undefined and you cannot rely on them. Portable AnyEvent
184	callbacks cannot use arguments passed to time watcher callbacks.	247	callbacks cannot use arguments passed to time watcher callbacks.
185		248
186	The timer callback will be invoked at most once: if you want a repeating	249	The callback will normally be invoked once only. If you specify another
187	timer you have to create a new watcher (this is a limitation by both Tk	250	parameter, C<interval>, as a strictly positive number (> 0), then the
188	and Glib).	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.
189		254
190	Example:	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.
191		258
192	# fire an event after 7.7 seconds	259	Example: fire an event after 7.7 seconds.
		260
193	my $w = AnyEvent->timer (after => 7.7, cb => sub {	261	my $w = AnyEvent->timer (after => 7.7, cb => sub {
194	warn "timeout\n";	262	warn "timeout\n";
195	});	263	});
196		264
197	# to cancel the timer:	265	# to cancel the timer:
198	undef $w;	266	undef $w;
199		267
200	Example 2:
201
202	# 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.
203	my $w;
204		269
205	my $cb = sub {
206	# cancel the old timer while creating a new one
207	$w = AnyEvent->timer (after => 1, cb => $cb);	270	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		271	warn "timeout\n";
208	};	272	};
209
210	# start the "loop" by creating the first watcher
211	$w = AnyEvent->timer (after => 0.5, cb => $cb);
212		273
213	=head3 TIMING ISSUES	274	=head3 TIMING ISSUES
214		275
215	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
216	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
…		…
228	timers.	289	timers.
229		290
230	AnyEvent always prefers relative timers, if available, matching the	291	AnyEvent always prefers relative timers, if available, matching the
231	AnyEvent API.	292	AnyEvent API.
232		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
233	=head2 SIGNAL WATCHERS	372	=head2 SIGNAL WATCHERS
234		373
		374	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		375
235	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
236	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
237	be invoked whenever a signal occurs.	378	callback to be invoked whenever a signal occurs.
238		379
239	Although the callback might get passed parameters, their value and	380	Although the callback might get passed parameters, their value and
240	presence is undefined and you cannot rely on them. Portable AnyEvent	381	presence is undefined and you cannot rely on them. Portable AnyEvent
241	callbacks cannot use arguments passed to signal watcher callbacks.	382	callbacks cannot use arguments passed to signal watcher callbacks.
242		383
243	Multiple signal occurances can be clumped together into one callback	384	Multiple signal occurrences can be clumped together into one callback
244	invocation, and callback invocation will be synchronous. synchronous means	385	invocation, and callback invocation will be synchronous. Synchronous means
245	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,
246	but it is guarenteed not to interrupt any other callbacks.	387	but it is guaranteed not to interrupt any other callbacks.
247		388
248	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
249	between multiple watchers.	390	between multiple watchers, and AnyEvent will ensure that signals will not
		391	interrupt your program at bad times.
250		392
251	This watcher might use C<%SIG>, so programs overwriting those signals	393	This watcher might use C<%SIG> (depending on the event loop used),
252	directly will likely not work correctly.	394	so programs overwriting those signals directly will likely not work
		395	correctly.
253		396
254	Example: exit on SIGINT	397	Example: exit on SIGINT
255		398
256	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	399	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
257		400
		401	=head3 Signal Races, Delays and Workarounds
		402
		403	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		404	callbacks to signals in a generic way, which is a pity, as you cannot do
		405	race-free signal handling in perl. AnyEvent will try to do it's best, but
		406	in some cases, signals will be delayed. The maximum time a signal might
		407	be delayed is specified in C<$AnyEvent::MAX_SIGNAL_LATENCY> (default: 10
		408	seconds). This variable can be changed only before the first signal
		409	watcher is created, and should be left alone otherwise. Higher values
		410	will cause fewer spurious wake-ups, which is better for power and CPU
		411	saving. All these problems can be avoided by installing the optional
		412	L<Async::Interrupt> module. This will not work with inherently broken
		413	event loops such as L<Event> or L<Event::Lib> (and not with L<POE>
		414	currently, as POE does it's own workaround with one-second latency). With
		415	those, you just have to suffer the delays.
		416
258	=head2 CHILD PROCESS WATCHERS	417	=head2 CHILD PROCESS WATCHERS
259		418
		419	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		420
260	You can also watch on a child process exit and catch its exit status.	421	You can also watch on a child process exit and catch its exit status.
261		422
262	The child process is specified by the C<pid> argument (if set to C<0>, it	423	The child process is specified by the C<pid> argument (one some backends,
263	watches for any child process exit). The watcher will trigger as often	424	using C<0> watches for any child process exit, on others this will
264	as status change for the child are received. This works by installing a	425	croak). The watcher will be triggered only when the child process has
265	signal handler for C<SIGCHLD>. The callback will be called with the pid	426	finished and an exit status is available, not on any trace events
266	and exit status (as returned by waitpid), so unlike other watcher types,	427	(stopped/continued).
267	you I<can> rely on child watcher callback arguments.	428
		429	The callback will be called with the pid and exit status (as returned by
		430	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		431	callback arguments.
		432
		433	This watcher type works by installing a signal handler for C<SIGCHLD>,
		434	and since it cannot be shared, nothing else should use SIGCHLD or reap
		435	random child processes (waiting for specific child processes, e.g. inside
		436	C<system>, is just fine).
268		437
269	There is a slight catch to child watchers, however: you usually start them	438	There is a slight catch to child watchers, however: you usually start them
270	I<after> the child process was created, and this means the process could	439	I<after> the child process was created, and this means the process could
271	have exited already (and no SIGCHLD will be sent anymore).	440	have exited already (and no SIGCHLD will be sent anymore).
272		441
273	Not all event models handle this correctly (POE doesn't), but even for	442	Not all event models handle this correctly (neither POE nor IO::Async do,
		443	see their AnyEvent::Impl manpages for details), but even for event models
274	event models that I<do> handle this correctly, they usually need to be	444	that I<do> handle this correctly, they usually need to be loaded before
275	loaded before the process exits (i.e. before you fork in the first place).	445	the process exits (i.e. before you fork in the first place). AnyEvent's
		446	pure perl event loop handles all cases correctly regardless of when you
		447	start the watcher.
276		448
277	This means you cannot create a child watcher as the very first thing in an	449	This means you cannot create a child watcher as the very first
278	AnyEvent program, you I<have> to create at least one watcher before you	450	thing in an AnyEvent program, you I<have> to create at least one
279	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).	451	watcher before you C<fork> the child (alternatively, you can call
		452	C<AnyEvent::detect>).
		453
		454	As most event loops do not support waiting for child events, they will be
		455	emulated by AnyEvent in most cases, in which the latency and race problems
		456	mentioned in the description of signal watchers apply.
280		457
281	Example: fork a process and wait for it	458	Example: fork a process and wait for it
282		459
283	my $done = AnyEvent->condvar;	460	my $done = AnyEvent->condvar;
284		461
285	AnyEvent::detect; # force event module to be initialised
286
287	my $pid = fork or exit 5;	462	my $pid = fork or exit 5;
288		463
289	my $w = AnyEvent->child (	464	my $w = AnyEvent->child (
290	pid => $pid,	465	pid => $pid,
291	cb => sub {	466	cb => sub {
292	my ($pid, $status) = @_;	467	my ($pid, $status) = @_;
293	warn "pid $pid exited with status $status";	468	warn "pid $pid exited with status $status";
294	$done->broadcast;	469	$done->send;
295	},	470	},
296	);	471	);
297		472
298	# do something else, then wait for process exit	473	# do something else, then wait for process exit
299	$done->wait;	474	$done->recv;
		475
		476	=head2 IDLE WATCHERS
		477
		478	$w = AnyEvent->idle (cb => <callback>);
		479
		480	Sometimes there is a need to do something, but it is not so important
		481	to do it instantly, but only when there is nothing better to do. This
		482	"nothing better to do" is usually defined to be "no other events need
		483	attention by the event loop".
		484
		485	Idle watchers ideally get invoked when the event loop has nothing
		486	better to do, just before it would block the process to wait for new
		487	events. Instead of blocking, the idle watcher is invoked.
		488
		489	Most event loops unfortunately do not really support idle watchers (only
		490	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		491	will simply call the callback "from time to time".
		492
		493	Example: read lines from STDIN, but only process them when the
		494	program is otherwise idle:
		495
		496	my @lines; # read data
		497	my $idle_w;
		498	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		499	push @lines, scalar <STDIN>;
		500
		501	# start an idle watcher, if not already done
		502	$idle_w ||= AnyEvent->idle (cb => sub {
		503	# handle only one line, when there are lines left
		504	if (my $line = shift @lines) {
		505	print "handled when idle: $line";
		506	} else {
		507	# otherwise disable the idle watcher again
		508	undef $idle_w;
		509	}
		510	});
		511	});
300		512
301	=head2 CONDITION VARIABLES	513	=head2 CONDITION VARIABLES
302		514
		515	$cv = AnyEvent->condvar;
		516
		517	$cv->send (<list>);
		518	my @res = $cv->recv;
		519
		520	If you are familiar with some event loops you will know that all of them
		521	require you to run some blocking "loop", "run" or similar function that
		522	will actively watch for new events and call your callbacks.
		523
		524	AnyEvent is slightly different: it expects somebody else to run the event
		525	loop and will only block when necessary (usually when told by the user).
		526
		527	The instrument to do that is called a "condition variable", so called
		528	because they represent a condition that must become true.
		529
		530	Now is probably a good time to look at the examples further below.
		531
303	Condition variables can be created by calling the C<< AnyEvent->condvar >>	532	Condition variables can be created by calling the C<< AnyEvent->condvar
304	method without any arguments.	533	>> method, usually without arguments. The only argument pair allowed is
		534	C<cb>, which specifies a callback to be called when the condition variable
		535	becomes true, with the condition variable as the first argument (but not
		536	the results).
305		537
306	A condition variable waits for a condition - precisely that the C<<	538	After creation, the condition variable is "false" until it becomes "true"
307	->broadcast >> method has been called.	539	by calling the C<send> method (or calling the condition variable as if it
		540	were a callback, read about the caveats in the description for the C<<
		541	->send >> method).
308		542
309	They are very useful to signal that a condition has been fulfilled, for	543	Condition variables are similar to callbacks, except that you can
		544	optionally wait for them. They can also be called merge points - points
		545	in time where multiple outstanding events have been processed. And yet
		546	another way to call them is transactions - each condition variable can be
		547	used to represent a transaction, which finishes at some point and delivers
		548	a result. And yet some people know them as "futures" - a promise to
		549	compute/deliver something that you can wait for.
		550
		551	Condition variables are very useful to signal that something has finished,
310	example, if you write a module that does asynchronous http requests,	552	for example, if you write a module that does asynchronous http requests,
311	then a condition variable would be the ideal candidate to signal the	553	then a condition variable would be the ideal candidate to signal the
312	availability of results.	554	availability of results. The user can either act when the callback is
		555	called or can synchronously C<< ->recv >> for the results.
313		556
314	You can also use condition variables to block your main program until	557	You can also use them to simulate traditional event loops - for example,
315	an event occurs - for example, you could C<< ->wait >> in your main	558	you can block your main program until an event occurs - for example, you
316	program until the user clicks the Quit button in your app, which would C<<	559	could C<< ->recv >> in your main program until the user clicks the Quit
317	->broadcast >> the "quit" event.	560	button of your app, which would C<< ->send >> the "quit" event.
318		561
319	Note that condition variables recurse into the event loop - if you have	562	Note that condition variables recurse into the event loop - if you have
320	two pirces of code that call C<< ->wait >> in a round-robbin fashion, you	563	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
321	lose. Therefore, condition variables are good to export to your caller, but	564	lose. Therefore, condition variables are good to export to your caller, but
322	you should avoid making a blocking wait yourself, at least in callbacks,	565	you should avoid making a blocking wait yourself, at least in callbacks,
323	as this asks for trouble.	566	as this asks for trouble.
324		567
325	This object has two methods:	568	Condition variables are represented by hash refs in perl, and the keys
		569	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
		570	easy (it is often useful to build your own transaction class on top of
		571	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
		572	it's C<new> method in your own C<new> method.
326		573
327	=over 4	574	There are two "sides" to a condition variable - the "producer side" which
		575	eventually calls C<< -> send >>, and the "consumer side", which waits
		576	for the send to occur.
328		577
329	=item $cv->wait	578	Example: wait for a timer.
330
331	Wait (blocking if necessary) until the C<< ->broadcast >> method has been
332	called on c<$cv>, while servicing other watchers normally.
333
334	You can only wait once on a condition - additional calls will return
335	immediately.
336
337	Not all event models support a blocking wait - some die in that case
338	(programs might want to do that to stay interactive), so I<if you are
339	using this from a module, never require a blocking wait>, but let the
340	caller decide whether the call will block or not (for example, by coupling
341	condition variables with some kind of request results and supporting
342	callbacks so the caller knows that getting the result will not block,
343	while still suppporting blocking waits if the caller so desires).
344
345	Another reason I<never> to C<< ->wait >> in a module is that you cannot
346	sensibly have two C<< ->wait >>'s in parallel, as that would require
347	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
348	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and
349	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
350	from different coroutines, however).
351
352	=item $cv->broadcast
353
354	Flag the condition as ready - a running C<< ->wait >> and all further
355	calls to C<wait> will (eventually) return after this method has been
356	called. If nobody is waiting the broadcast will be remembered..
357
358	=back
359
360	Example:
361		579
362	# wait till the result is ready	580	# wait till the result is ready
363	my $result_ready = AnyEvent->condvar;	581	my $result_ready = AnyEvent->condvar;
364		582
365	# do something such as adding a timer	583	# do something such as adding a timer
366	# or socket watcher the calls $result_ready->broadcast	584	# or socket watcher the calls $result_ready->send
367	# when the "result" is ready.	585	# when the "result" is ready.
368	# in this case, we simply use a timer:	586	# in this case, we simply use a timer:
369	my $w = AnyEvent->timer (	587	my $w = AnyEvent->timer (
370	after => 1,	588	after => 1,
371	cb => sub { $result_ready->broadcast },	589	cb => sub { $result_ready->send },
372	);	590	);
373		591
374	# this "blocks" (while handling events) till the watcher	592	# this "blocks" (while handling events) till the callback
375	# calls broadcast	593	# calls -<send
376	$result_ready->wait;	594	$result_ready->recv;
		595
		596	Example: wait for a timer, but take advantage of the fact that condition
		597	variables are also callable directly.
		598
		599	my $done = AnyEvent->condvar;
		600	my $delay = AnyEvent->timer (after => 5, cb => $done);
		601	$done->recv;
		602
		603	Example: Imagine an API that returns a condvar and doesn't support
		604	callbacks. This is how you make a synchronous call, for example from
		605	the main program:
		606
		607	use AnyEvent::CouchDB;
		608
		609	...
		610
		611	my @info = $couchdb->info->recv;
		612
		613	And this is how you would just set a callback to be called whenever the
		614	results are available:
		615
		616	$couchdb->info->cb (sub {
		617	my @info = $_[0]->recv;
		618	});
		619
		620	=head3 METHODS FOR PRODUCERS
		621
		622	These methods should only be used by the producing side, i.e. the
		623	code/module that eventually sends the signal. Note that it is also
		624	the producer side which creates the condvar in most cases, but it isn't
		625	uncommon for the consumer to create it as well.
		626
		627	=over 4
		628
		629	=item $cv->send (...)
		630
		631	Flag the condition as ready - a running C<< ->recv >> and all further
		632	calls to C<recv> will (eventually) return after this method has been
		633	called. If nobody is waiting the send will be remembered.
		634
		635	If a callback has been set on the condition variable, it is called
		636	immediately from within send.
		637
		638	Any arguments passed to the C<send> call will be returned by all
		639	future C<< ->recv >> calls.
		640
		641	Condition variables are overloaded so one can call them directly (as if
		642	they were a code reference). Calling them directly is the same as calling
		643	C<send>.
		644
		645	=item $cv->croak ($error)
		646
		647	Similar to send, but causes all call's to C<< ->recv >> to invoke
		648	C<Carp::croak> with the given error message/object/scalar.
		649
		650	This can be used to signal any errors to the condition variable
		651	user/consumer. Doing it this way instead of calling C<croak> directly
		652	delays the error detetcion, but has the overwhelmign advantage that it
		653	diagnoses the error at the place where the result is expected, and not
		654	deep in some event clalback without connection to the actual code causing
		655	the problem.
		656
		657	=item $cv->begin ([group callback])
		658
		659	=item $cv->end
		660
		661	These two methods can be used to combine many transactions/events into
		662	one. For example, a function that pings many hosts in parallel might want
		663	to use a condition variable for the whole process.
		664
		665	Every call to C<< ->begin >> will increment a counter, and every call to
		666	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
		667	>>, the (last) callback passed to C<begin> will be executed. That callback
		668	is I<supposed> to call C<< ->send >>, but that is not required. If no
		669	callback was set, C<send> will be called without any arguments.
		670
		671	You can think of C<< $cv->send >> giving you an OR condition (one call
		672	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		673	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		674
		675	Let's start with a simple example: you have two I/O watchers (for example,
		676	STDOUT and STDERR for a program), and you want to wait for both streams to
		677	close before activating a condvar:
		678
		679	my $cv = AnyEvent->condvar;
		680
		681	$cv->begin; # first watcher
		682	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		683	defined sysread $fh1, my $buf, 4096
		684	or $cv->end;
		685	});
		686
		687	$cv->begin; # second watcher
		688	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		689	defined sysread $fh2, my $buf, 4096
		690	or $cv->end;
		691	});
		692
		693	$cv->recv;
		694
		695	This works because for every event source (EOF on file handle), there is
		696	one call to C<begin>, so the condvar waits for all calls to C<end> before
		697	sending.
		698
		699	The ping example mentioned above is slightly more complicated, as the
		700	there are results to be passwd back, and the number of tasks that are
		701	begung can potentially be zero:
		702
		703	my $cv = AnyEvent->condvar;
		704
		705	my %result;
		706	$cv->begin (sub { $cv->send (\%result) });
		707
		708	for my $host (@list_of_hosts) {
		709	$cv->begin;
		710	ping_host_then_call_callback $host, sub {
		711	$result{$host} = ...;
		712	$cv->end;
		713	};
		714	}
		715
		716	$cv->end;
		717
		718	This code fragment supposedly pings a number of hosts and calls
		719	C<send> after results for all then have have been gathered - in any
		720	order. To achieve this, the code issues a call to C<begin> when it starts
		721	each ping request and calls C<end> when it has received some result for
		722	it. Since C<begin> and C<end> only maintain a counter, the order in which
		723	results arrive is not relevant.
		724
		725	There is an additional bracketing call to C<begin> and C<end> outside the
		726	loop, which serves two important purposes: first, it sets the callback
		727	to be called once the counter reaches C<0>, and second, it ensures that
		728	C<send> is called even when C<no> hosts are being pinged (the loop
		729	doesn't execute once).
		730
		731	This is the general pattern when you "fan out" into multiple (but
		732	potentially none) subrequests: use an outer C<begin>/C<end> pair to set
		733	the callback and ensure C<end> is called at least once, and then, for each
		734	subrequest you start, call C<begin> and for each subrequest you finish,
		735	call C<end>.
		736
		737	=back
		738
		739	=head3 METHODS FOR CONSUMERS
		740
		741	These methods should only be used by the consuming side, i.e. the
		742	code awaits the condition.
		743
		744	=over 4
		745
		746	=item $cv->recv
		747
		748	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
		749	>> methods have been called on c<$cv>, while servicing other watchers
		750	normally.
		751
		752	You can only wait once on a condition - additional calls are valid but
		753	will return immediately.
		754
		755	If an error condition has been set by calling C<< ->croak >>, then this
		756	function will call C<croak>.
		757
		758	In list context, all parameters passed to C<send> will be returned,
		759	in scalar context only the first one will be returned.
		760
		761	Note that doing a blocking wait in a callback is not supported by any
		762	event loop, that is, recursive invocation of a blocking C<< ->recv
		763	>> is not allowed, and the C<recv> call will C<croak> if such a
		764	condition is detected. This condition can be slightly loosened by using
		765	L<Coro::AnyEvent>, which allows you to do a blocking C<< ->recv >> from
		766	any thread that doesn't run the event loop itself.
		767
		768	Not all event models support a blocking wait - some die in that case
		769	(programs might want to do that to stay interactive), so I<if you are
		770	using this from a module, never require a blocking wait>. Instead, let the
		771	caller decide whether the call will block or not (for example, by coupling
		772	condition variables with some kind of request results and supporting
		773	callbacks so the caller knows that getting the result will not block,
		774	while still supporting blocking waits if the caller so desires).
		775
		776	You can ensure that C<< -recv >> never blocks by setting a callback and
		777	only calling C<< ->recv >> from within that callback (or at a later
		778	time). This will work even when the event loop does not support blocking
		779	waits otherwise.
		780
		781	=item $bool = $cv->ready
		782
		783	Returns true when the condition is "true", i.e. whether C<send> or
		784	C<croak> have been called.
		785
		786	=item $cb = $cv->cb ($cb->($cv))
		787
		788	This is a mutator function that returns the callback set and optionally
		789	replaces it before doing so.
		790
		791	The callback will be called when the condition becomes "true", i.e. when
		792	C<send> or C<croak> are called, with the only argument being the condition
		793	variable itself. Calling C<recv> inside the callback or at any later time
		794	is guaranteed not to block.
		795
		796	=back
		797
		798	=head1 SUPPORTED EVENT LOOPS/BACKENDS
		799
		800	The available backend classes are (every class has its own manpage):
		801
		802	=over 4
		803
		804	=item Backends that are autoprobed when no other event loop can be found.
		805
		806	EV is the preferred backend when no other event loop seems to be in
		807	use. If EV is not installed, then AnyEvent will try Event, and, failing
		808	that, will fall back to its own pure-perl implementation, which is
		809	available everywhere as it comes with AnyEvent itself.
		810
		811	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		812	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		813	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
		814
		815	=item Backends that are transparently being picked up when they are used.
		816
		817	These will be used when they are currently loaded when the first watcher
		818	is created, in which case it is assumed that the application is using
		819	them. This means that AnyEvent will automatically pick the right backend
		820	when the main program loads an event module before anything starts to
		821	create watchers. Nothing special needs to be done by the main program.
		822
		823	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		824	AnyEvent::Impl::Tk based on Tk, very broken.
		825	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		826	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		827	AnyEvent::Impl::Irssi used when running within irssi.
		828
		829	=item Backends with special needs.
		830
		831	Qt requires the Qt::Application to be instantiated first, but will
		832	otherwise be picked up automatically. As long as the main program
		833	instantiates the application before any AnyEvent watchers are created,
		834	everything should just work.
		835
		836	AnyEvent::Impl::Qt based on Qt.
		837
		838	Support for IO::Async can only be partial, as it is too broken and
		839	architecturally limited to even support the AnyEvent API. It also
		840	is the only event loop that needs the loop to be set explicitly, so
		841	it can only be used by a main program knowing about AnyEvent. See
		842	L<AnyEvent::Impl::Async> for the gory details.
		843
		844	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
		845
		846	=item Event loops that are indirectly supported via other backends.
		847
		848	Some event loops can be supported via other modules:
		849
		850	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		851
		852	B<WxWidgets> has no support for watching file handles. However, you can
		853	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		854	polls 20 times per second, which was considered to be too horrible to even
		855	consider for AnyEvent.
		856
		857	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		858	backend, so it can be supported through POE.
		859
		860	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		861	load L<POE> when detecting them, in the hope that POE will pick them up,
		862	in which case everything will be automatic.
		863
		864	=back
377		865
378	=head1 GLOBAL VARIABLES AND FUNCTIONS	866	=head1 GLOBAL VARIABLES AND FUNCTIONS
379		867
		868	These are not normally required to use AnyEvent, but can be useful to
		869	write AnyEvent extension modules.
		870
380	=over 4	871	=over 4
381		872
382	=item $AnyEvent::MODEL	873	=item $AnyEvent::MODEL
383		874
384	Contains C<undef> until the first watcher is being created. Then it	875	Contains C<undef> until the first watcher is being created, before the
		876	backend has been autodetected.
		877
385	contains the event model that is being used, which is the name of the	878	Afterwards it contains the event model that is being used, which is the
386	Perl class implementing the model. This class is usually one of the	879	name of the Perl class implementing the model. This class is usually one
387	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	880	of the C<AnyEvent::Impl:xxx> modules, but can be any other class in the
388	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	881	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
389		882	will be C<urxvt::anyevent>).
390	The known classes so far are:
391
392	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
393	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
394	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
395	AnyEvent::Impl::Event based on Event, second best choice.
396	AnyEvent::Impl::Glib based on Glib, third-best choice.
397	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
398	AnyEvent::Impl::Tk based on Tk, very bad choice.
399	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
400	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
401	AnyEvent::Impl::POE based on POE, not generic enough for full support.
402
403	There is no support for WxWidgets, as WxWidgets has no support for
404	watching file handles. However, you can use WxWidgets through the
405	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
406	second, which was considered to be too horrible to even consider for
407	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
408	it's adaptor.
409
410	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
411	autodetecting them.
412		883
413	=item AnyEvent::detect	884	=item AnyEvent::detect
414		885
415	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	886	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
416	if necessary. You should only call this function right before you would	887	if necessary. You should only call this function right before you would
417	have created an AnyEvent watcher anyway, that is, as late as possible at	888	have created an AnyEvent watcher anyway, that is, as late as possible at
418	runtime.	889	runtime, and not e.g. while initialising of your module.
		890
		891	If you need to do some initialisation before AnyEvent watchers are
		892	created, use C<post_detect>.
		893
		894	=item $guard = AnyEvent::post_detect { BLOCK }
		895
		896	Arranges for the code block to be executed as soon as the event model is
		897	autodetected (or immediately if this has already happened).
		898
		899	The block will be executed I<after> the actual backend has been detected
		900	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		901	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		902	other initialisations - see the sources of L<AnyEvent::Strict> or
		903	L<AnyEvent::AIO> to see how this is used.
		904
		905	The most common usage is to create some global watchers, without forcing
		906	event module detection too early, for example, L<AnyEvent::AIO> creates
		907	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		908	avoid autodetecting the event module at load time.
		909
		910	If called in scalar or list context, then it creates and returns an object
		911	that automatically removes the callback again when it is destroyed (or
		912	C<undef> when the hook was immediately executed). See L<AnyEvent::AIO> for
		913	a case where this is useful.
		914
		915	Example: Create a watcher for the IO::AIO module and store it in
		916	C<$WATCHER>. Only do so after the event loop is initialised, though.
		917
		918	our WATCHER;
		919
		920	my $guard = AnyEvent::post_detect {
		921	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		922	};
		923
		924	# the ||= is important in case post_detect immediately runs the block,
		925	# as to not clobber the newly-created watcher. assigning both watcher and
		926	# post_detect guard to the same variable has the advantage of users being
		927	# able to just C<undef $WATCHER> if the watcher causes them grief.
		928
		929	$WATCHER ||= $guard;
		930
		931	=item @AnyEvent::post_detect
		932
		933	If there are any code references in this array (you can C<push> to it
		934	before or after loading AnyEvent), then they will called directly after
		935	the event loop has been chosen.
		936
		937	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		938	if it is defined then the event loop has already been detected, and the
		939	array will be ignored.
		940
		941	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		942	it,as it takes care of these details.
		943
		944	This variable is mainly useful for modules that can do something useful
		945	when AnyEvent is used and thus want to know when it is initialised, but do
		946	not need to even load it by default. This array provides the means to hook
		947	into AnyEvent passively, without loading it.
419		948
420	=back	949	=back
421		950
422	=head1 WHAT TO DO IN A MODULE	951	=head1 WHAT TO DO IN A MODULE
423		952
…		…
427	Be careful when you create watchers in the module body - AnyEvent will	956	Be careful when you create watchers in the module body - AnyEvent will
428	decide which event module to use as soon as the first method is called, so	957	decide which event module to use as soon as the first method is called, so
429	by calling AnyEvent in your module body you force the user of your module	958	by calling AnyEvent in your module body you force the user of your module
430	to load the event module first.	959	to load the event module first.
431		960
432	Never call C<< ->wait >> on a condition variable unless you I<know> that	961	Never call C<< ->recv >> on a condition variable unless you I<know> that
433	the C<< ->broadcast >> method has been called on it already. This is	962	the C<< ->send >> method has been called on it already. This is
434	because it will stall the whole program, and the whole point of using	963	because it will stall the whole program, and the whole point of using
435	events is to stay interactive.	964	events is to stay interactive.
436		965
437	It is fine, however, to call C<< ->wait >> when the user of your module	966	It is fine, however, to call C<< ->recv >> when the user of your module
438	requests it (i.e. if you create a http request object ad have a method	967	requests it (i.e. if you create a http request object ad have a method
439	called C<results> that returns the results, it should call C<< ->wait >>	968	called C<results> that returns the results, it should call C<< ->recv >>
440	freely, as the user of your module knows what she is doing. always).	969	freely, as the user of your module knows what she is doing. always).
441		970
442	=head1 WHAT TO DO IN THE MAIN PROGRAM	971	=head1 WHAT TO DO IN THE MAIN PROGRAM
443		972
444	There will always be a single main program - the only place that should	973	There will always be a single main program - the only place that should
…		…
446		975
447	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	976	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
448	do anything special (it does not need to be event-based) and let AnyEvent	977	do anything special (it does not need to be event-based) and let AnyEvent
449	decide which implementation to chose if some module relies on it.	978	decide which implementation to chose if some module relies on it.
450		979
451	If the main program relies on a specific event model. For example, in	980	If the main program relies on a specific event model - for example, in
452	Gtk2 programs you have to rely on the Glib module. You should load the	981	Gtk2 programs you have to rely on the Glib module - you should load the
453	event module before loading AnyEvent or any module that uses it: generally	982	event module before loading AnyEvent or any module that uses it: generally
454	speaking, you should load it as early as possible. The reason is that	983	speaking, you should load it as early as possible. The reason is that
455	modules might create watchers when they are loaded, and AnyEvent will	984	modules might create watchers when they are loaded, and AnyEvent will
456	decide on the event model to use as soon as it creates watchers, and it	985	decide on the event model to use as soon as it creates watchers, and it
457	might chose the wrong one unless you load the correct one yourself.	986	might chose the wrong one unless you load the correct one yourself.
458		987
459	You can chose to use a rather inefficient pure-perl implementation by	988	You can chose to use a pure-perl implementation by loading the
460	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	989	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
461	behaviour everywhere, but letting AnyEvent chose is generally better.	990	everywhere, but letting AnyEvent chose the model is generally better.
		991
		992	=head2 MAINLOOP EMULATION
		993
		994	Sometimes (often for short test scripts, or even standalone programs who
		995	only want to use AnyEvent), you do not want to run a specific event loop.
		996
		997	In that case, you can use a condition variable like this:
		998
		999	AnyEvent->condvar->recv;
		1000
		1001	This has the effect of entering the event loop and looping forever.
		1002
		1003	Note that usually your program has some exit condition, in which case
		1004	it is better to use the "traditional" approach of storing a condition
		1005	variable somewhere, waiting for it, and sending it when the program should
		1006	exit cleanly.
		1007
		1008
		1009	=head1 OTHER MODULES
		1010
		1011	The following is a non-exhaustive list of additional modules that use
		1012	AnyEvent as a client and can therefore be mixed easily with other AnyEvent
		1013	modules and other event loops in the same program. Some of the modules
		1014	come with AnyEvent, most are available via CPAN.
		1015
		1016	=over 4
		1017
		1018	=item L<AnyEvent::Util>
		1019
		1020	Contains various utility functions that replace often-used but blocking
		1021	functions such as C<inet_aton> by event-/callback-based versions.
		1022
		1023	=item L<AnyEvent::Socket>
		1024
		1025	Provides various utility functions for (internet protocol) sockets,
		1026	addresses and name resolution. Also functions to create non-blocking tcp
		1027	connections or tcp servers, with IPv6 and SRV record support and more.
		1028
		1029	=item L<AnyEvent::Handle>
		1030
		1031	Provide read and write buffers, manages watchers for reads and writes,
		1032	supports raw and formatted I/O, I/O queued and fully transparent and
		1033	non-blocking SSL/TLS (via L<AnyEvent::TLS>.
		1034
		1035	=item L<AnyEvent::DNS>
		1036
		1037	Provides rich asynchronous DNS resolver capabilities.
		1038
		1039	=item L<AnyEvent::HTTP>
		1040
		1041	A simple-to-use HTTP library that is capable of making a lot of concurrent
		1042	HTTP requests.
		1043
		1044	=item L<AnyEvent::HTTPD>
		1045
		1046	Provides a simple web application server framework.
		1047
		1048	=item L<AnyEvent::FastPing>
		1049
		1050	The fastest ping in the west.
		1051
		1052	=item L<AnyEvent::DBI>
		1053
		1054	Executes L<DBI> requests asynchronously in a proxy process.
		1055
		1056	=item L<AnyEvent::AIO>
		1057
		1058	Truly asynchronous I/O, should be in the toolbox of every event
		1059	programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
		1060	together.
		1061
		1062	=item L<AnyEvent::BDB>
		1063
		1064	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
		1065	L<BDB> and AnyEvent together.
		1066
		1067	=item L<AnyEvent::GPSD>
		1068
		1069	A non-blocking interface to gpsd, a daemon delivering GPS information.
		1070
		1071	=item L<AnyEvent::IRC>
		1072
		1073	AnyEvent based IRC client module family (replacing the older Net::IRC3).
		1074
		1075	=item L<AnyEvent::XMPP>
		1076
		1077	AnyEvent based XMPP (Jabber protocol) module family (replacing the older
		1078	Net::XMPP2>.
		1079
		1080	=item L<AnyEvent::IGS>
		1081
		1082	A non-blocking interface to the Internet Go Server protocol (used by
		1083	L<App::IGS>).
		1084
		1085	=item L<Net::FCP>
		1086
		1087	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
		1088	of AnyEvent.
		1089
		1090	=item L<Event::ExecFlow>
		1091
		1092	High level API for event-based execution flow control.
		1093
		1094	=item L<Coro>
		1095
		1096	Has special support for AnyEvent via L<Coro::AnyEvent>.
		1097
		1098	=back
462		1099
463	=cut	1100	=cut
464		1101
465	package AnyEvent;	1102	package AnyEvent;
466		1103
		1104	# basically a tuned-down version of common::sense
		1105	sub common_sense {
467	no warnings;	1106	# no warnings
468	use strict;	1107	${^WARNING_BITS} ^= ${^WARNING_BITS};
		1108	# use strict vars subs
		1109	$^H |= 0x00000600;
		1110	}
469		1111
		1112	BEGIN { AnyEvent::common_sense }
		1113
470	use Carp;	1114	use Carp ();
471		1115
472	our $VERSION = '3.3';	1116	our $VERSION = 4.881;
473	our $MODEL;	1117	our $MODEL;
474		1118
475	our $AUTOLOAD;	1119	our $AUTOLOAD;
476	our @ISA;	1120	our @ISA;
477		1121
478	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
479
480	our @REGISTRY;	1122	our @REGISTRY;
481		1123
		1124	our $WIN32;
		1125
		1126	our $VERBOSE;
		1127
		1128	BEGIN {
		1129	eval "sub WIN32(){ " . (($^O =~ /mswin32/i)*1) ." }";
		1130	eval "sub TAINT(){ " . (${^TAINT}*1) . " }";
		1131
		1132	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1133	if ${^TAINT};
		1134
		1135	$VERBOSE = $ENV{PERL_ANYEVENT_VERBOSE}*1;
		1136
		1137	}
		1138
		1139	our $MAX_SIGNAL_LATENCY = 10;
		1140
		1141	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		1142
		1143	{
		1144	my $idx;
		1145	$PROTOCOL{$_} = ++$idx
		1146	for reverse split /\s*,\s*/,
		1147	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		1148	}
		1149
482	my @models = (	1150	my @models = (
483	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
484	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
485	[EV:: => AnyEvent::Impl::EV::],	1151	[EV:: => AnyEvent::Impl::EV:: , 1],
486	[Event:: => AnyEvent::Impl::Event::],	1152	[Event:: => AnyEvent::Impl::Event::, 1],
487	[Glib:: => AnyEvent::Impl::Glib::],	1153	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl:: , 1],
		1154	# everything below here will not (normally) be autoprobed
		1155	# as the pureperl backend should work everywhere
		1156	# and is usually faster
		1157	[Glib:: => AnyEvent::Impl::Glib:: , 1], # becomes extremely slow with many watchers
		1158	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		1159	[Irssi:: => AnyEvent::Impl::Irssi::], # Irssi has a bogus "Event" package
488	[Tk:: => AnyEvent::Impl::Tk::],	1160	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		1161	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		1162	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
489	[Wx:: => AnyEvent::Impl::POE::],	1163	[Wx:: => AnyEvent::Impl::POE::],
490	[Prima:: => AnyEvent::Impl::POE::],	1164	[Prima:: => AnyEvent::Impl::POE::],
491	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1165	# IO::Async is just too broken - we would need workarounds for its
492	# everything below here will not be autoprobed as the pureperl backend should work everywhere	1166	# byzantine signal and broken child handling, among others.
493	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy	1167	# IO::Async is rather hard to detect, as it doesn't have any
		1168	# obvious default class.
494	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program	1169	# [0, IO::Async:: => AnyEvent::Impl::IOAsync::], # requires special main program
495	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza	1170	# [0, IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1171	# [0, IO::Async::Notifier:: => AnyEvent::Impl::IOAsync::], # requires special main program
496	);	1172	);
497		1173
498	our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);	1174	our %method = map +($_ => 1),
		1175	qw(io timer time now now_update signal child idle condvar one_event DESTROY);
		1176
		1177	our @post_detect;
		1178
		1179	sub post_detect(&) {
		1180	my ($cb) = @_;
		1181
		1182	if ($MODEL) {
		1183	$cb->();
		1184
		1185	undef
		1186	} else {
		1187	push @post_detect, $cb;
		1188
		1189	defined wantarray
		1190	? bless \$cb, "AnyEvent::Util::postdetect"
		1191	: ()
		1192	}
		1193	}
		1194
		1195	sub AnyEvent::Util::postdetect::DESTROY {
		1196	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		1197	}
499		1198
500	sub detect() {	1199	sub detect() {
501	unless ($MODEL) {	1200	unless ($MODEL) {
502	no strict 'refs';	1201	local $SIG{__DIE__};
503		1202
504	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	1203	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
505	my $model = "AnyEvent::Impl::$1";	1204	my $model = "AnyEvent::Impl::$1";
506	if (eval "require $model") {	1205	if (eval "require $model") {
507	$MODEL = $model;	1206	$MODEL = $model;
508	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	1207	warn "AnyEvent: loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.\n" if $VERBOSE >= 2;
509	} else {	1208	} else {
510	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;	1209	warn "AnyEvent: unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@" if $VERBOSE;
511	}	1210	}
512	}	1211	}
513		1212
514	# check for already loaded models	1213	# check for already loaded models
515	unless ($MODEL) {	1214	unless ($MODEL) {
516	for (@REGISTRY, @models) {	1215	for (@REGISTRY, @models) {
517	my ($package, $model) = @$_;	1216	my ($package, $model) = @$_;
518	if (${"$package\::VERSION"} > 0) {	1217	if (${"$package\::VERSION"} > 0) {
519	if (eval "require $model") {	1218	if (eval "require $model") {
520	$MODEL = $model;	1219	$MODEL = $model;
521	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;	1220	warn "AnyEvent: autodetected model '$model', using it.\n" if $VERBOSE >= 2;
522	last;	1221	last;
523	}	1222	}
524	}	1223	}
525	}	1224	}
526		1225
527	unless ($MODEL) {	1226	unless ($MODEL) {
528	# try to load a model	1227	# try to autoload a model
529
530	for (@REGISTRY, @models) {	1228	for (@REGISTRY, @models) {
531	my ($package, $model) = @$_;	1229	my ($package, $model, $autoload) = @$_;
		1230	if (
		1231	$autoload
532	if (eval "require $package"	1232	and eval "require $package"
533	and ${"$package\::VERSION"} > 0	1233	and ${"$package\::VERSION"} > 0
534	and eval "require $model") {	1234	and eval "require $model"
		1235	) {
535	$MODEL = $model;	1236	$MODEL = $model;
536	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;	1237	warn "AnyEvent: autoloaded model '$model', using it.\n" if $VERBOSE >= 2;
537	last;	1238	last;
538	}	1239	}
539	}	1240	}
540		1241
541	$MODEL	1242	$MODEL
542	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV (or Coro+EV), Event (or Coro+Event) or Glib.";	1243	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.\n";
543	}	1244	}
544	}	1245	}
545		1246
		1247	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		1248
546	unshift @ISA, $MODEL;	1249	unshift @ISA, $MODEL;
547	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	1250
		1251	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
		1252
		1253	(shift @post_detect)->() while @post_detect;
548	}	1254	}
549		1255
550	$MODEL	1256	$MODEL
551	}	1257	}
552		1258
553	sub AUTOLOAD {	1259	sub AUTOLOAD {
554	(my $func = $AUTOLOAD) =~ s/.*://;	1260	(my $func = $AUTOLOAD) =~ s/.*://;
555		1261
556	$method{$func}	1262	$method{$func}
557	or croak "$func: not a valid method for AnyEvent objects";	1263	or Carp::croak "$func: not a valid method for AnyEvent objects";
558		1264
559	detect unless $MODEL;	1265	detect unless $MODEL;
560		1266
561	my $class = shift;	1267	my $class = shift;
562	$class->$func (@_);	1268	$class->$func (@_);
563	}	1269	}
564		1270
		1271	# utility function to dup a filehandle. this is used by many backends
		1272	# to support binding more than one watcher per filehandle (they usually
		1273	# allow only one watcher per fd, so we dup it to get a different one).
		1274	sub _dupfh($$;$$) {
		1275	my ($poll, $fh, $r, $w) = @_;
		1276
		1277	# cygwin requires the fh mode to be matching, unix doesn't
		1278	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1279
		1280	open my $fh2, $mode, $fh
		1281	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1282
		1283	# we assume CLOEXEC is already set by perl in all important cases
		1284
		1285	($fh2, $rw)
		1286	}
		1287
565	package AnyEvent::Base;	1288	package AnyEvent::Base;
566		1289
		1290	# default implementations for many methods
		1291
		1292	sub _time {
		1293	# probe for availability of Time::HiRes
		1294	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1295	warn "AnyEvent: using Time::HiRes for sub-second timing accuracy.\n" if $VERBOSE >= 8;
		1296	*_time = \&Time::HiRes::time;
		1297	# if (eval "use POSIX (); (POSIX::times())...
		1298	} else {
		1299	warn "AnyEvent: using built-in time(), WARNING, no sub-second resolution!\n" if $VERBOSE;
		1300	*_time = sub { time }; # epic fail
		1301	}
		1302
		1303	&_time
		1304	}
		1305
		1306	sub time { _time }
		1307	sub now { _time }
		1308	sub now_update { }
		1309
567	# default implementation for ->condvar, ->wait, ->broadcast	1310	# default implementation for ->condvar
568		1311
569	sub condvar {	1312	sub condvar {
570	bless \my $flag, "AnyEvent::Base::CondVar"	1313	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
571	}
572
573	sub AnyEvent::Base::CondVar::broadcast {
574	${$_[0]}++;
575	}
576
577	sub AnyEvent::Base::CondVar::wait {
578	AnyEvent->one_event while !${$_[0]};
579	}	1314	}
580		1315
581	# default implementation for ->signal	1316	# default implementation for ->signal
582		1317
583	our %SIG_CB;	1318	our $HAVE_ASYNC_INTERRUPT;
		1319
		1320	sub _have_async_interrupt() {
		1321	$HAVE_ASYNC_INTERRUPT = 1*(!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT}
		1322	&& eval "use Async::Interrupt 1.0 (); 1")
		1323	unless defined $HAVE_ASYNC_INTERRUPT;
		1324
		1325	$HAVE_ASYNC_INTERRUPT
		1326	}
		1327
		1328	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1329	our (%SIG_ASY, %SIG_ASY_W);
		1330	our ($SIG_COUNT, $SIG_TW);
		1331
		1332	sub _signal_exec {
		1333	$HAVE_ASYNC_INTERRUPT
		1334	? $SIGPIPE_R->drain
		1335	: sysread $SIGPIPE_R, my $dummy, 9;
		1336
		1337	while (%SIG_EV) {
		1338	for (keys %SIG_EV) {
		1339	delete $SIG_EV{$_};
		1340	$_->() for values %{ $SIG_CB{$_} || {} };
		1341	}
		1342	}
		1343	}
		1344
		1345	# install a dummy wakeup watcher to reduce signal catching latency
		1346	sub _sig_add() {
		1347	unless ($SIG_COUNT++) {
		1348	# try to align timer on a full-second boundary, if possible
		1349	my $NOW = AnyEvent->now;
		1350
		1351	$SIG_TW = AnyEvent->timer (
		1352	after => $MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1353	interval => $MAX_SIGNAL_LATENCY,
		1354	cb => sub { }, # just for the PERL_ASYNC_CHECK
		1355	);
		1356	}
		1357	}
		1358
		1359	sub _sig_del {
		1360	undef $SIG_TW
		1361	unless --$SIG_COUNT;
		1362	}
		1363
		1364	our $_sig_name_init; $_sig_name_init = sub {
		1365	eval q{ # poor man's autoloading
		1366	undef $_sig_name_init;
		1367
		1368	if (_have_async_interrupt) {
		1369	*sig2num = \&Async::Interrupt::sig2num;
		1370	*sig2name = \&Async::Interrupt::sig2name;
		1371	} else {
		1372	require Config;
		1373
		1374	my %signame2num;
		1375	@signame2num{ split ' ', $Config::Config{sig_name} }
		1376	= split ' ', $Config::Config{sig_num};
		1377
		1378	my @signum2name;
		1379	@signum2name[values %signame2num] = keys %signame2num;
		1380
		1381	*sig2num = sub($) {
		1382	$_[0] > 0 ? shift : $signame2num{+shift}
		1383	};
		1384	*sig2name = sub ($) {
		1385	$_[0] > 0 ? $signum2name[+shift] : shift
		1386	};
		1387	}
		1388	};
		1389	die if $@;
		1390	};
		1391
		1392	sub sig2num ($) { &$_sig_name_init; &sig2num }
		1393	sub sig2name($) { &$_sig_name_init; &sig2name }
584		1394
585	sub signal {	1395	sub signal {
		1396	eval q{ # poor man's autoloading {}
		1397	# probe for availability of Async::Interrupt
		1398	if (_have_async_interrupt) {
		1399	warn "AnyEvent: using Async::Interrupt for race-free signal handling.\n" if $VERBOSE >= 8;
		1400
		1401	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1402	$SIG_IO = AnyEvent->io (fh => $SIGPIPE_R->fileno, poll => "r", cb => \&_signal_exec);
		1403
		1404	} else {
		1405	warn "AnyEvent: using emulated perl signal handling with latency timer.\n" if $VERBOSE >= 8;
		1406
		1407	require Fcntl;
		1408
		1409	if (AnyEvent::WIN32) {
		1410	require AnyEvent::Util;
		1411
		1412	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1413	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R, 1) if $SIGPIPE_R;
		1414	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W, 1) if $SIGPIPE_W; # just in case
		1415	} else {
		1416	pipe $SIGPIPE_R, $SIGPIPE_W;
		1417	fcntl $SIGPIPE_R, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_R;
		1418	fcntl $SIGPIPE_W, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_W; # just in case
		1419
		1420	# not strictly required, as $^F is normally 2, but let's make sure...
		1421	fcntl $SIGPIPE_R, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1422	fcntl $SIGPIPE_W, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1423	}
		1424
		1425	$SIGPIPE_R
		1426	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1427
		1428	$SIG_IO = AnyEvent->io (fh => $SIGPIPE_R, poll => "r", cb => \&_signal_exec);
		1429	}
		1430
		1431	*signal = sub {
586	my (undef, %arg) = @_;	1432	my (undef, %arg) = @_;
587		1433
588	my $signal = uc $arg{signal}	1434	my $signal = uc $arg{signal}
589	or Carp::croak "required option 'signal' is missing";	1435	or Carp::croak "required option 'signal' is missing";
590		1436
		1437	if ($HAVE_ASYNC_INTERRUPT) {
		1438	# async::interrupt
		1439
		1440	$signal = sig2num $signal;
591	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1441	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1442
		1443	$SIG_ASY{$signal} ||= new Async::Interrupt
		1444	cb => sub { undef $SIG_EV{$signal} },
		1445	signal => $signal,
		1446	pipe => [$SIGPIPE_R->filenos],
		1447	pipe_autodrain => 0,
		1448	;
		1449
		1450	} else {
		1451	# pure perl
		1452
		1453	# AE::Util has been loaded in signal
		1454	$signal = sig2name $signal;
		1455	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1456
592	$SIG{$signal} ||= sub {	1457	$SIG{$signal} ||= sub {
593	$_->() for values %{ $SIG_CB{$signal} || {} };	1458	local $!;
		1459	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1460	undef $SIG_EV{$signal};
		1461	};
		1462
		1463	# can't do signal processing without introducing races in pure perl,
		1464	# so limit the signal latency.
		1465	_sig_add;
		1466	}
		1467
		1468	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1469	};
		1470
		1471	*AnyEvent::Base::signal::DESTROY = sub {
		1472	my ($signal, $cb) = @{$_[0]};
		1473
		1474	_sig_del;
		1475
		1476	delete $SIG_CB{$signal}{$cb};
		1477
		1478	$HAVE_ASYNC_INTERRUPT
		1479	? delete $SIG_ASY{$signal}
		1480	: # delete doesn't work with older perls - they then
		1481	# print weird messages, or just unconditionally exit
		1482	# instead of getting the default action.
		1483	undef $SIG{$signal}
		1484	unless keys %{ $SIG_CB{$signal} };
		1485	};
594	};	1486	};
595		1487	die if $@;
596	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1488	&signal
597	}
598
599	sub AnyEvent::Base::Signal::DESTROY {
600	my ($signal, $cb) = @{$_[0]};
601
602	delete $SIG_CB{$signal}{$cb};
603
604	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };
605	}	1489	}
606		1490
607	# default implementation for ->child	1491	# default implementation for ->child
608		1492
609	our %PID_CB;	1493	our %PID_CB;
610	our $CHLD_W;	1494	our $CHLD_W;
611	our $CHLD_DELAY_W;	1495	our $CHLD_DELAY_W;
612	our $PID_IDLE;
613	our $WNOHANG;	1496	our $WNOHANG;
614		1497
615	sub _child_wait {	1498	sub _emit_childstatus($$) {
616	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1499	my (undef, $rpid, $rstatus) = @_;
		1500
		1501	$_->($rpid, $rstatus)
617	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1502	for values %{ $PID_CB{$rpid} || {} },
618	(values %{ $PID_CB{0} || {} });	1503	values %{ $PID_CB{0} || {} };
619	}
620
621	undef $PID_IDLE;
622	}	1504	}
623		1505
624	sub _sigchld {	1506	sub _sigchld {
625	# make sure we deliver these changes "synchronous" with the event loop.	1507	my $pid;
626	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {	1508
627	undef $CHLD_DELAY_W;	1509	AnyEvent->_emit_childstatus ($pid, $?)
628	&_child_wait;	1510	while ($pid = waitpid -1, $WNOHANG) > 0;
629	});
630	}	1511	}
631		1512
632	sub child {	1513	sub child {
633	my (undef, %arg) = @_;	1514	my (undef, %arg) = @_;
634		1515
635	defined (my $pid = $arg{pid} + 0)	1516	defined (my $pid = $arg{pid} + 0)
636	or Carp::croak "required option 'pid' is missing";	1517	or Carp::croak "required option 'pid' is missing";
637		1518
638	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1519	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
639		1520
640	unless ($WNOHANG) {	1521	# WNOHANG is almost cetrainly 1 everywhere
641	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;	1522	$WNOHANG ||= $^O =~ /^(?:openbsd|netbsd|linux|freebsd|cygwin|MSWin32)$/
642	}	1523	? 1
		1524	: eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
643		1525
644	unless ($CHLD_W) {	1526	unless ($CHLD_W) {
645	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1527	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
646	# child could be a zombie already, so make at least one round	1528	# child could be a zombie already, so make at least one round
647	&_sigchld;	1529	&_sigchld;
648	}	1530	}
649		1531
650	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	1532	bless [$pid, $arg{cb}], "AnyEvent::Base::child"
651	}	1533	}
652		1534
653	sub AnyEvent::Base::Child::DESTROY {	1535	sub AnyEvent::Base::child::DESTROY {
654	my ($pid, $cb) = @{$_[0]};	1536	my ($pid, $cb) = @{$_[0]};
655		1537
656	delete $PID_CB{$pid}{$cb};	1538	delete $PID_CB{$pid}{$cb};
657	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1539	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
658		1540
659	undef $CHLD_W unless keys %PID_CB;	1541	undef $CHLD_W unless keys %PID_CB;
660	}	1542	}
		1543
		1544	# idle emulation is done by simply using a timer, regardless
		1545	# of whether the process is idle or not, and not letting
		1546	# the callback use more than 50% of the time.
		1547	sub idle {
		1548	my (undef, %arg) = @_;
		1549
		1550	my ($cb, $w, $rcb) = $arg{cb};
		1551
		1552	$rcb = sub {
		1553	if ($cb) {
		1554	$w = _time;
		1555	&$cb;
		1556	$w = _time - $w;
		1557
		1558	# never use more then 50% of the time for the idle watcher,
		1559	# within some limits
		1560	$w = 0.0001 if $w < 0.0001;
		1561	$w = 5 if $w > 5;
		1562
		1563	$w = AnyEvent->timer (after => $w, cb => $rcb);
		1564	} else {
		1565	# clean up...
		1566	undef $w;
		1567	undef $rcb;
		1568	}
		1569	};
		1570
		1571	$w = AnyEvent->timer (after => 0.05, cb => $rcb);
		1572
		1573	bless \\$cb, "AnyEvent::Base::idle"
		1574	}
		1575
		1576	sub AnyEvent::Base::idle::DESTROY {
		1577	undef $${$_[0]};
		1578	}
		1579
		1580	package AnyEvent::CondVar;
		1581
		1582	our @ISA = AnyEvent::CondVar::Base::;
		1583
		1584	package AnyEvent::CondVar::Base;
		1585
		1586	#use overload
		1587	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1588	# fallback => 1;
		1589
		1590	# save 300+ kilobytes by dirtily hardcoding overloading
		1591	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1592	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1593	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1594	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1595
		1596	our $WAITING;
		1597
		1598	sub _send {
		1599	# nop
		1600	}
		1601
		1602	sub send {
		1603	my $cv = shift;
		1604	$cv->{_ae_sent} = [@_];
		1605	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1606	$cv->_send;
		1607	}
		1608
		1609	sub croak {
		1610	$_[0]{_ae_croak} = $_[1];
		1611	$_[0]->send;
		1612	}
		1613
		1614	sub ready {
		1615	$_[0]{_ae_sent}
		1616	}
		1617
		1618	sub _wait {
		1619	$WAITING
		1620	and !$_[0]{_ae_sent}
		1621	and Carp::croak "AnyEvent::CondVar: recursive blocking wait detected";
		1622
		1623	local $WAITING = 1;
		1624	AnyEvent->one_event while !$_[0]{_ae_sent};
		1625	}
		1626
		1627	sub recv {
		1628	$_[0]->_wait;
		1629
		1630	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
		1631	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
		1632	}
		1633
		1634	sub cb {
		1635	$_[0]{_ae_cb} = $_[1] if @_ > 1;
		1636	$_[0]{_ae_cb}
		1637	}
		1638
		1639	sub begin {
		1640	++$_[0]{_ae_counter};
		1641	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
		1642	}
		1643
		1644	sub end {
		1645	return if --$_[0]{_ae_counter};
		1646	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		1647	}
		1648
		1649	# undocumented/compatibility with pre-3.4
		1650	*broadcast = \&send;
		1651	*wait = \&_wait;
		1652
		1653	#############################################################################
		1654	# "new" API, currently only emulation of it
		1655	#############################################################################
		1656
		1657	package AE;
		1658
		1659	sub io($$$) {
		1660	AnyEvent->io (fh => $_[0], poll => $_[1] ? "w" : "r", cb => $_[2])
		1661	}
		1662
		1663	sub timer($$$) {
		1664	AnyEvent->timer (after => $_[0], interval => $_[1], cb => $_[2]);
		1665	}
		1666
		1667	sub signal($$) {
		1668	AnyEvent->signal (signal => $_[0], cb => $_[1]);
		1669	}
		1670
		1671	sub child($$) {
		1672	AnyEvent->child (pid => $_[0], cb => $_[1]);
		1673	}
		1674
		1675	sub idle($) {
		1676	AnyEvent->idle (cb => $_[0]);
		1677	}
		1678
		1679	sub cv() {
		1680	AnyEvent->condvar
		1681	}
		1682
		1683	sub now() {
		1684	AnyEvent->now
		1685	}
		1686
		1687	sub now_update() {
		1688	AnyEvent->now_update
		1689	}
		1690
		1691	sub time() {
		1692	AnyEvent->time
		1693	}
		1694
		1695	=head1 ERROR AND EXCEPTION HANDLING
		1696
		1697	In general, AnyEvent does not do any error handling - it relies on the
		1698	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1699	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1700	checking of all AnyEvent methods, however, which is highly useful during
		1701	development.
		1702
		1703	As for exception handling (i.e. runtime errors and exceptions thrown while
		1704	executing a callback), this is not only highly event-loop specific, but
		1705	also not in any way wrapped by this module, as this is the job of the main
		1706	program.
		1707
		1708	The pure perl event loop simply re-throws the exception (usually
		1709	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1710	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1711	so on.
		1712
		1713	=head1 ENVIRONMENT VARIABLES
		1714
		1715	The following environment variables are used by this module or its
		1716	submodules.
		1717
		1718	Note that AnyEvent will remove I<all> environment variables starting with
		1719	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		1720	enabled.
		1721
		1722	=over 4
		1723
		1724	=item C<PERL_ANYEVENT_VERBOSE>
		1725
		1726	By default, AnyEvent will be completely silent except in fatal
		1727	conditions. You can set this environment variable to make AnyEvent more
		1728	talkative.
		1729
		1730	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1731	conditions, such as not being able to load the event model specified by
		1732	C<PERL_ANYEVENT_MODEL>.
		1733
		1734	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1735	model it chooses.
		1736
		1737	When set to C<8> or higher, then AnyEvent will report extra information on
		1738	which optional modules it loads and how it implements certain features.
		1739
		1740	=item C<PERL_ANYEVENT_STRICT>
		1741
		1742	AnyEvent does not do much argument checking by default, as thorough
		1743	argument checking is very costly. Setting this variable to a true value
		1744	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1745	check the arguments passed to most method calls. If it finds any problems,
		1746	it will croak.
		1747
		1748	In other words, enables "strict" mode.
		1749
		1750	Unlike C<use strict> (or it's modern cousin, C<< use L<common::sense>
		1751	>>, it is definitely recommended to keep it off in production. Keeping
		1752	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		1753	can be very useful, however.
		1754
		1755	=item C<PERL_ANYEVENT_MODEL>
		1756
		1757	This can be used to specify the event model to be used by AnyEvent, before
		1758	auto detection and -probing kicks in. It must be a string consisting
		1759	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1760	and the resulting module name is loaded and if the load was successful,
		1761	used as event model. If it fails to load AnyEvent will proceed with
		1762	auto detection and -probing.
		1763
		1764	This functionality might change in future versions.
		1765
		1766	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1767	could start your program like this:
		1768
		1769	PERL_ANYEVENT_MODEL=Perl perl ...
		1770
		1771	=item C<PERL_ANYEVENT_PROTOCOLS>
		1772
		1773	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1774	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1775	of auto probing).
		1776
		1777	Must be set to a comma-separated list of protocols or address families,
		1778	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1779	used, and preference will be given to protocols mentioned earlier in the
		1780	list.
		1781
		1782	This variable can effectively be used for denial-of-service attacks
		1783	against local programs (e.g. when setuid), although the impact is likely
		1784	small, as the program has to handle conenction and other failures anyways.
		1785
		1786	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1787	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1788	- only support IPv4, never try to resolve or contact IPv6
		1789	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1790	IPv6, but prefer IPv6 over IPv4.
		1791
		1792	=item C<PERL_ANYEVENT_EDNS0>
		1793
		1794	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1795	for DNS. This extension is generally useful to reduce DNS traffic, but
		1796	some (broken) firewalls drop such DNS packets, which is why it is off by
		1797	default.
		1798
		1799	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1800	EDNS0 in its DNS requests.
		1801
		1802	=item C<PERL_ANYEVENT_MAX_FORKS>
		1803
		1804	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1805	will create in parallel.
		1806
		1807	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		1808
		1809	The default value for the C<max_outstanding> parameter for the default DNS
		1810	resolver - this is the maximum number of parallel DNS requests that are
		1811	sent to the DNS server.
		1812
		1813	=item C<PERL_ANYEVENT_RESOLV_CONF>
		1814
		1815	The file to use instead of F</etc/resolv.conf> (or OS-specific
		1816	configuration) in the default resolver. When set to the empty string, no
		1817	default config will be used.
		1818
		1819	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		1820
		1821	When neither C<ca_file> nor C<ca_path> was specified during
		1822	L<AnyEvent::TLS> context creation, and either of these environment
		1823	variables exist, they will be used to specify CA certificate locations
		1824	instead of a system-dependent default.
		1825
		1826	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		1827
		1828	When these are set to C<1>, then the respective modules are not
		1829	loaded. Mostly good for testing AnyEvent itself.
		1830
		1831	=back
661		1832
662	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1833	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
663		1834
664	This is an advanced topic that you do not normally need to use AnyEvent in	1835	This is an advanced topic that you do not normally need to use AnyEvent in
665	a module. This section is only of use to event loop authors who want to	1836	a module. This section is only of use to event loop authors who want to
…		…
699		1870
700	I<rxvt-unicode> also cheats a bit by not providing blocking access to	1871	I<rxvt-unicode> also cheats a bit by not providing blocking access to
701	condition variables: code blocking while waiting for a condition will	1872	condition variables: code blocking while waiting for a condition will
702	C<die>. This still works with most modules/usages, and blocking calls must	1873	C<die>. This still works with most modules/usages, and blocking calls must
703	not be done in an interactive application, so it makes sense.	1874	not be done in an interactive application, so it makes sense.
704
705	=head1 ENVIRONMENT VARIABLES
706
707	The following environment variables are used by this module:
708
709	=over 4
710
711	=item C<PERL_ANYEVENT_VERBOSE>
712
713	By default, AnyEvent will be completely silent except in fatal
714	conditions. You can set this environment variable to make AnyEvent more
715	talkative.
716
717	When set to C<1> or higher, causes AnyEvent to warn about unexpected
718	conditions, such as not being able to load the event model specified by
719	C<PERL_ANYEVENT_MODEL>.
720
721	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
722	model it chooses.
723
724	=item C<PERL_ANYEVENT_MODEL>
725
726	This can be used to specify the event model to be used by AnyEvent, before
727	autodetection and -probing kicks in. It must be a string consisting
728	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
729	and the resulting module name is loaded and if the load was successful,
730	used as event model. If it fails to load AnyEvent will proceed with
731	autodetection and -probing.
732
733	This functionality might change in future versions.
734
735	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
736	could start your program like this:
737
738	PERL_ANYEVENT_MODEL=Perl perl ...
739
740	=back
741		1875
742	=head1 EXAMPLE PROGRAM	1876	=head1 EXAMPLE PROGRAM
743		1877
744	The following program uses an I/O watcher to read data from STDIN, a timer	1878	The following program uses an I/O watcher to read data from STDIN, a timer
745	to display a message once per second, and a condition variable to quit the	1879	to display a message once per second, and a condition variable to quit the
…		…
754	poll => 'r',	1888	poll => 'r',
755	cb => sub {	1889	cb => sub {
756	warn "io event <$_[0]>\n"; # will always output <r>	1890	warn "io event <$_[0]>\n"; # will always output <r>
757	chomp (my $input = <STDIN>); # read a line	1891	chomp (my $input = <STDIN>); # read a line
758	warn "read: $input\n"; # output what has been read	1892	warn "read: $input\n"; # output what has been read
759	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	1893	$cv->send if $input =~ /^q/i; # quit program if /^q/i
760	},	1894	},
761	);	1895	);
762		1896
763	my $time_watcher; # can only be used once	1897	my $time_watcher; # can only be used once
764		1898
…		…
769	});	1903	});
770	}	1904	}
771		1905
772	new_timer; # create first timer	1906	new_timer; # create first timer
773		1907
774	$cv->wait; # wait until user enters /^q/i	1908	$cv->recv; # wait until user enters /^q/i
775		1909
776	=head1 REAL-WORLD EXAMPLE	1910	=head1 REAL-WORLD EXAMPLE
777		1911
778	Consider the L<Net::FCP> module. It features (among others) the following	1912	Consider the L<Net::FCP> module. It features (among others) the following
779	API calls, which are to freenet what HTTP GET requests are to http:	1913	API calls, which are to freenet what HTTP GET requests are to http:
…		…
829	syswrite $txn->{fh}, $txn->{request}	1963	syswrite $txn->{fh}, $txn->{request}
830	or die "connection or write error";	1964	or die "connection or write error";
831	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	1965	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
832		1966
833	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	1967	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
834	result and signals any possible waiters that the request ahs finished:	1968	result and signals any possible waiters that the request has finished:
835		1969
836	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	1970	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
837		1971
838	if (end-of-file or data complete) {	1972	if (end-of-file or data complete) {
839	$txn->{result} = $txn->{buf};	1973	$txn->{result} = $txn->{buf};
840	$txn->{finished}->broadcast;	1974	$txn->{finished}->send;
841	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	1975	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
842	}	1976	}
843		1977
844	The C<result> method, finally, just waits for the finished signal (if the	1978	The C<result> method, finally, just waits for the finished signal (if the
845	request was already finished, it doesn't wait, of course, and returns the	1979	request was already finished, it doesn't wait, of course, and returns the
846	data:	1980	data:
847		1981
848	$txn->{finished}->wait;	1982	$txn->{finished}->recv;
849	return $txn->{result};	1983	return $txn->{result};
850		1984
851	The actual code goes further and collects all errors (C<die>s, exceptions)	1985	The actual code goes further and collects all errors (C<die>s, exceptions)
852	that occured during request processing. The C<result> method detects	1986	that occurred during request processing. The C<result> method detects
853	whether an exception as thrown (it is stored inside the $txn object)	1987	whether an exception as thrown (it is stored inside the $txn object)
854	and just throws the exception, which means connection errors and other	1988	and just throws the exception, which means connection errors and other
855	problems get reported tot he code that tries to use the result, not in a	1989	problems get reported tot he code that tries to use the result, not in a
856	random callback.	1990	random callback.
857		1991
…		…
888		2022
889	my $quit = AnyEvent->condvar;	2023	my $quit = AnyEvent->condvar;
890		2024
891	$fcp->txn_client_get ($url)->cb (sub {	2025	$fcp->txn_client_get ($url)->cb (sub {
892	...	2026	...
893	$quit->broadcast;	2027	$quit->send;
894	});	2028	});
895		2029
896	$quit->wait;	2030	$quit->recv;
897		2031
898		2032
899	=head1 BENCHMARKS	2033	=head1 BENCHMARKS
900		2034
901	To give you an idea of the performance and overheads that AnyEvent adds	2035	To give you an idea of the performance and overheads that AnyEvent adds
…		…
903	of various event loops I prepared some benchmarks.	2037	of various event loops I prepared some benchmarks.
904		2038
905	=head2 BENCHMARKING ANYEVENT OVERHEAD	2039	=head2 BENCHMARKING ANYEVENT OVERHEAD
906		2040
907	Here is a benchmark of various supported event models used natively and	2041	Here is a benchmark of various supported event models used natively and
908	through anyevent. The benchmark creates a lot of timers (with a zero	2042	through AnyEvent. The benchmark creates a lot of timers (with a zero
909	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,	2043	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
910	which it is), lets them fire exactly once and destroys them again.	2044	which it is), lets them fire exactly once and destroys them again.
911		2045
912	Source code for this benchmark is found as F<eg/bench> in the AnyEvent	2046	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
913	distribution.	2047	distribution.
…		…
930	all watchers, to avoid adding memory overhead. That means closure creation	2064	all watchers, to avoid adding memory overhead. That means closure creation
931	and memory usage is not included in the figures.	2065	and memory usage is not included in the figures.
932		2066
933	I<invoke> is the time, in microseconds, used to invoke a simple	2067	I<invoke> is the time, in microseconds, used to invoke a simple
934	callback. The callback simply counts down a Perl variable and after it was	2068	callback. The callback simply counts down a Perl variable and after it was
935	invoked "watcher" times, it would C<< ->broadcast >> a condvar once to	2069	invoked "watcher" times, it would C<< ->send >> a condvar once to
936	signal the end of this phase.	2070	signal the end of this phase.
937		2071
938	I<destroy> is the time, in microseconds, that it takes to destroy a single	2072	I<destroy> is the time, in microseconds, that it takes to destroy a single
939	watcher.	2073	watcher.
940		2074
941	=head3 Results	2075	=head3 Results
942		2076
943	name watchers bytes create invoke destroy comment	2077	name watchers bytes create invoke destroy comment
944	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	2078	EV/EV 400000 224 0.47 0.35 0.27 EV native interface
945	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	2079	EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers
946	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	2080	CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal
947	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	2081	Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation
948	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	2082	Event/Event 16000 517 32.20 31.80 0.81 Event native interface
949	Event/Any 16000 936 39.17 33.63 1.43 Event + AnyEvent watchers	2083	Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers
		2084	IOAsync/Any 16000 989 38.10 32.77 11.13 via IO::Async::Loop::IO_Poll
		2085	IOAsync/Any 16000 990 37.59 29.50 10.61 via IO::Async::Loop::Epoll
950	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	2086	Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour
951	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	2087	Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers
952	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	2088	POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event
953	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	2089	POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select
954		2090
955	=head3 Discussion	2091	=head3 Discussion
956		2092
957	The benchmark does I<not> measure scalability of the event loop very	2093	The benchmark does I<not> measure scalability of the event loop very
958	well. For example, a select-based event loop (such as the pure perl one)	2094	well. For example, a select-based event loop (such as the pure perl one)
959	can never compete with an event loop that uses epoll when the number of	2095	can never compete with an event loop that uses epoll when the number of
960	file descriptors grows high. In this benchmark, all events become ready at	2096	file descriptors grows high. In this benchmark, all events become ready at
961	the same time, so select/poll-based implementations get an unnatural speed	2097	the same time, so select/poll-based implementations get an unnatural speed
962	boost.	2098	boost.
963		2099
		2100	Also, note that the number of watchers usually has a nonlinear effect on
		2101	overall speed, that is, creating twice as many watchers doesn't take twice
		2102	the time - usually it takes longer. This puts event loops tested with a
		2103	higher number of watchers at a disadvantage.
		2104
		2105	To put the range of results into perspective, consider that on the
		2106	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		2107	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		2108	cycles with POE.
		2109
964	C<EV> is the sole leader regarding speed and memory use, which are both	2110	C<EV> is the sole leader regarding speed and memory use, which are both
965	maximal/minimal, respectively. Even when going through AnyEvent, it uses	2111	maximal/minimal, respectively. Even when going through AnyEvent, it uses
966	far less memory than any other event loop and is still faster than Event	2112	far less memory than any other event loop and is still faster than Event
967	natively.	2113	natively.
968		2114
…		…
973	performance becomes really bad with lots of file descriptors (and few of	2119	performance becomes really bad with lots of file descriptors (and few of
974	them active), of course, but this was not subject of this benchmark.	2120	them active), of course, but this was not subject of this benchmark.
975		2121
976	The C<Event> module has a relatively high setup and callback invocation	2122	The C<Event> module has a relatively high setup and callback invocation
977	cost, but overall scores in on the third place.	2123	cost, but overall scores in on the third place.
		2124
		2125	C<IO::Async> performs admirably well, about on par with C<Event>, even
		2126	when using its pure perl backend.
978		2127
979	C<Glib>'s memory usage is quite a bit higher, but it features a	2128	C<Glib>'s memory usage is quite a bit higher, but it features a
980	faster callback invocation and overall ends up in the same class as	2129	faster callback invocation and overall ends up in the same class as
981	C<Event>. However, Glib scales extremely badly, doubling the number of	2130	C<Event>. However, Glib scales extremely badly, doubling the number of
982	watchers increases the processing time by more than a factor of four,	2131	watchers increases the processing time by more than a factor of four,
…		…
990	file descriptor is dup()ed for each watcher. This shows that the dup()	2139	file descriptor is dup()ed for each watcher. This shows that the dup()
991	employed by some adaptors is not a big performance issue (it does incur a	2140	employed by some adaptors is not a big performance issue (it does incur a
992	hidden memory cost inside the kernel which is not reflected in the figures	2141	hidden memory cost inside the kernel which is not reflected in the figures
993	above).	2142	above).
994		2143
995	C<POE>, regardless of underlying event loop (whether using its pure	2144	C<POE>, regardless of underlying event loop (whether using its pure perl
996	perl select-based backend or the Event module, the POE-EV backend	2145	select-based backend or the Event module, the POE-EV backend couldn't
997	couldn't be tested because it wasn't working) shows abysmal performance	2146	be tested because it wasn't working) shows abysmal performance and
998	and memory usage: Watchers use almost 30 times as much memory as	2147	memory usage with AnyEvent: Watchers use almost 30 times as much memory
999	EV watchers, and 10 times as much memory as Event (the high memory	2148	as EV watchers, and 10 times as much memory as Event (the high memory
1000	requirements are caused by requiring a session for each watcher). Watcher	2149	requirements are caused by requiring a session for each watcher). Watcher
1001	invocation speed is almost 900 times slower than with AnyEvent's pure perl	2150	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		2151	implementation.
		2152
1002	implementation. The design of the POE adaptor class in AnyEvent can not	2153	The design of the POE adaptor class in AnyEvent can not really account
1003	really account for this, as session creation overhead is small compared	2154	for the performance issues, though, as session creation overhead is
1004	to execution of the state machine, which is coded pretty optimally within	2155	small compared to execution of the state machine, which is coded pretty
1005	L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow.	2156	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		2157	using multiple sessions is not a good approach, especially regarding
		2158	memory usage, even the author of POE could not come up with a faster
		2159	design).
1006		2160
1007	=head3 Summary	2161	=head3 Summary
1008		2162
1009	=over 4	2163	=over 4
1010		2164
…		…
1021		2175
1022	=back	2176	=back
1023		2177
1024	=head2 BENCHMARKING THE LARGE SERVER CASE	2178	=head2 BENCHMARKING THE LARGE SERVER CASE
1025		2179
1026	This benchmark atcually benchmarks the event loop itself. It works by	2180	This benchmark actually benchmarks the event loop itself. It works by
1027	creating a number of "servers": each server consists of a socketpair, a	2181	creating a number of "servers": each server consists of a socket pair, a
1028	timeout watcher that gets reset on activity (but never fires), and an I/O	2182	timeout watcher that gets reset on activity (but never fires), and an I/O
1029	watcher waiting for input on one side of the socket. Each time the socket	2183	watcher waiting for input on one side of the socket. Each time the socket
1030	watcher reads a byte it will write that byte to a random other "server".	2184	watcher reads a byte it will write that byte to a random other "server".
1031		2185
1032	The effect is that there will be a lot of I/O watchers, only part of which	2186	The effect is that there will be a lot of I/O watchers, only part of which
1033	are active at any one point (so there is a constant number of active	2187	are active at any one point (so there is a constant number of active
1034	fds for each loop iterstaion, but which fds these are is random). The	2188	fds for each loop iteration, but which fds these are is random). The
1035	timeout is reset each time something is read because that reflects how	2189	timeout is reset each time something is read because that reflects how
1036	most timeouts work (and puts extra pressure on the event loops).	2190	most timeouts work (and puts extra pressure on the event loops).
1037		2191
1038	In this benchmark, we use 10000 socketpairs (20000 sockets), of which 100	2192	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
1039	(1%) are active. This mirrors the activity of large servers with many	2193	(1%) are active. This mirrors the activity of large servers with many
1040	connections, most of which are idle at any one point in time.	2194	connections, most of which are idle at any one point in time.
1041		2195
1042	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent	2196	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
1043	distribution.	2197	distribution.
1044		2198
1045	=head3 Explanation of the columns	2199	=head3 Explanation of the columns
1046		2200
1047	I<sockets> is the number of sockets, and twice the number of "servers" (as	2201	I<sockets> is the number of sockets, and twice the number of "servers" (as
1048	eahc server has a read and write socket end).	2202	each server has a read and write socket end).
1049		2203
1050	I<create> is the time it takes to create a socketpair (which is	2204	I<create> is the time it takes to create a socket pair (which is
1051	nontrivial) and two watchers: an I/O watcher and a timeout watcher.	2205	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
1052		2206
1053	I<request>, the most important value, is the time it takes to handle a	2207	I<request>, the most important value, is the time it takes to handle a
1054	single "request", that is, reading the token from the pipe and forwarding	2208	single "request", that is, reading the token from the pipe and forwarding
1055	it to another server. This includes deleting the old timeout and creating	2209	it to another server. This includes deleting the old timeout and creating
1056	a new one that moves the timeout into the future.	2210	a new one that moves the timeout into the future.
1057		2211
1058	=head3 Results	2212	=head3 Results
1059		2213
1060	name sockets create request	2214	name sockets create request
1061	EV 20000 69.01 11.16	2215	EV 20000 69.01 11.16
1062	Perl 20000 75.28 112.76	2216	Perl 20000 73.32 35.87
		2217	IOAsync 20000 157.00 98.14 epoll
		2218	IOAsync 20000 159.31 616.06 poll
1063	Event 20000 212.62 257.32	2219	Event 20000 212.62 257.32
1064	Glib 20000 651.16 1896.30	2220	Glib 20000 651.16 1896.30
1065	POE 20000 349.67 12317.24 uses POE::Loop::Event	2221	POE 20000 349.67 12317.24 uses POE::Loop::Event
1066		2222
1067	=head3 Discussion	2223	=head3 Discussion
1068		2224
1069	This benchmark I<does> measure scalability and overall performance of the	2225	This benchmark I<does> measure scalability and overall performance of the
1070	particular event loop.	2226	particular event loop.
…		…
1072	EV is again fastest. Since it is using epoll on my system, the setup time	2228	EV is again fastest. Since it is using epoll on my system, the setup time
1073	is relatively high, though.	2229	is relatively high, though.
1074		2230
1075	Perl surprisingly comes second. It is much faster than the C-based event	2231	Perl surprisingly comes second. It is much faster than the C-based event
1076	loops Event and Glib.	2232	loops Event and Glib.
		2233
		2234	IO::Async performs very well when using its epoll backend, and still quite
		2235	good compared to Glib when using its pure perl backend.
1077		2236
1078	Event suffers from high setup time as well (look at its code and you will	2237	Event suffers from high setup time as well (look at its code and you will
1079	understand why). Callback invocation also has a high overhead compared to	2238	understand why). Callback invocation also has a high overhead compared to
1080	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event	2239	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
1081	uses select or poll in basically all documented configurations.	2240	uses select or poll in basically all documented configurations.
…		…
1089		2248
1090	=head3 Summary	2249	=head3 Summary
1091		2250
1092	=over 4	2251	=over 4
1093		2252
1094	=item * The pure perl implementation performs extremely well, considering	2253	=item * The pure perl implementation performs extremely well.
1095	that it uses select.
1096		2254
1097	=item * Avoid Glib or POE in large projects where performance matters.	2255	=item * Avoid Glib or POE in large projects where performance matters.
1098		2256
1099	=back	2257	=back
1100		2258
…		…
1113		2271
1114	=head3 Results	2272	=head3 Results
1115		2273
1116	name sockets create request	2274	name sockets create request
1117	EV 16 20.00 6.54	2275	EV 16 20.00 6.54
		2276	Perl 16 25.75 12.62
1118	Event 16 81.27 35.86	2277	Event 16 81.27 35.86
1119	Glib 16 32.63 15.48	2278	Glib 16 32.63 15.48
1120	Perl 16 24.62 162.37
1121	POE 16 261.87 276.28 uses POE::Loop::Event	2279	POE 16 261.87 276.28 uses POE::Loop::Event
1122		2280
1123	=head3 Discussion	2281	=head3 Discussion
1124		2282
1125	The benchmark tries to test the performance of a typical small	2283	The benchmark tries to test the performance of a typical small
1126	server. While knowing how various event loops perform is interesting, keep	2284	server. While knowing how various event loops perform is interesting, keep
1127	in mind that their overhead in this case is usually not as important, due	2285	in mind that their overhead in this case is usually not as important, due
1128	to the small absolute number of watchers.	2286	to the small absolute number of watchers (that is, you need efficiency and
		2287	speed most when you have lots of watchers, not when you only have a few of
		2288	them).
1129		2289
1130	EV is again fastest.	2290	EV is again fastest.
1131		2291
1132	The C-based event loops Event and Glib come in second this time, as the	2292	Perl again comes second. It is noticeably faster than the C-based event
1133	overhead of running an iteration is much smaller in C than in Perl (little	2293	loops Event and Glib, although the difference is too small to really
1134	code to execute in the inner loop, and perl's function calling overhead is	2294	matter.
1135	high, and updating all the data structures is costly).
1136		2295
1137	The pure perl event loop is much slower, but still competitive.
1138
1139	POE also performs much better in this case, but is is stillf ar behind the	2296	POE also performs much better in this case, but is is still far behind the
1140	others.	2297	others.
1141		2298
1142	=head3 Summary	2299	=head3 Summary
1143		2300
1144	=over 4	2301	=over 4
…		…
1146	=item * C-based event loops perform very well with small number of	2303	=item * C-based event loops perform very well with small number of
1147	watchers, as the management overhead dominates.	2304	watchers, as the management overhead dominates.
1148		2305
1149	=back	2306	=back
1150		2307
		2308	=head2 THE IO::Lambda BENCHMARK
		2309
		2310	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2311	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2312	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2313	shouldn't come as a surprise to anybody). As such, the benchmark is
		2314	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2315	very optimal. But how would AnyEvent compare when used without the extra
		2316	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2317
		2318	The benchmark itself creates an echo-server, and then, for 500 times,
		2319	connects to the echo server, sends a line, waits for the reply, and then
		2320	creates the next connection. This is a rather bad benchmark, as it doesn't
		2321	test the efficiency of the framework or much non-blocking I/O, but it is a
		2322	benchmark nevertheless.
		2323
		2324	name runtime
		2325	Lambda/select 0.330 sec
		2326	+ optimized 0.122 sec
		2327	Lambda/AnyEvent 0.327 sec
		2328	+ optimized 0.138 sec
		2329	Raw sockets/select 0.077 sec
		2330	POE/select, components 0.662 sec
		2331	POE/select, raw sockets 0.226 sec
		2332	POE/select, optimized 0.404 sec
		2333
		2334	AnyEvent/select/nb 0.085 sec
		2335	AnyEvent/EV/nb 0.068 sec
		2336	+state machine 0.134 sec
		2337
		2338	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2339	benchmarks actually make blocking connects and use 100% blocking I/O,
		2340	defeating the purpose of an event-based solution. All of the newly
		2341	written AnyEvent benchmarks use 100% non-blocking connects (using
		2342	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2343	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2344	generally require a lot more bookkeeping and event handling than blocking
		2345	connects (which involve a single syscall only).
		2346
		2347	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2348	offers similar expressive power as POE and IO::Lambda, using conventional
		2349	Perl syntax. This means that both the echo server and the client are 100%
		2350	non-blocking, further placing it at a disadvantage.
		2351
		2352	As you can see, the AnyEvent + EV combination even beats the
		2353	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2354	backend easily beats IO::Lambda and POE.
		2355
		2356	And even the 100% non-blocking version written using the high-level (and
		2357	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda by a
		2358	large margin, even though it does all of DNS, tcp-connect and socket I/O
		2359	in a non-blocking way.
		2360
		2361	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2362	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2363	part of the IO::lambda distribution and were used without any changes.
		2364
		2365
		2366	=head1 SIGNALS
		2367
		2368	AnyEvent currently installs handlers for these signals:
		2369
		2370	=over 4
		2371
		2372	=item SIGCHLD
		2373
		2374	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2375	emulation for event loops that do not support them natively. Also, some
		2376	event loops install a similar handler.
		2377
		2378	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2379	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2380
		2381	=item SIGPIPE
		2382
		2383	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2384	when AnyEvent gets loaded.
		2385
		2386	The rationale for this is that AnyEvent users usually do not really depend
		2387	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2388	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2389	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2390	some random socket.
		2391
		2392	The rationale for installing a no-op handler as opposed to ignoring it is
		2393	that this way, the handler will be restored to defaults on exec.
		2394
		2395	Feel free to install your own handler, or reset it to defaults.
		2396
		2397	=back
		2398
		2399	=cut
		2400
		2401	undef $SIG{CHLD}
		2402	if $SIG{CHLD} eq 'IGNORE';
		2403
		2404	$SIG{PIPE} = sub { }
		2405	unless defined $SIG{PIPE};
		2406
		2407	=head1 RECOMMENDED/OPTIONAL MODULES
		2408
		2409	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2410	it's built-in modules) are required to use it.
		2411
		2412	That does not mean that AnyEvent won't take advantage of some additional
		2413	modules if they are installed.
		2414
		2415	This section epxlains which additional modules will be used, and how they
		2416	affect AnyEvent's operetion.
		2417
		2418	=over 4
		2419
		2420	=item L<Async::Interrupt>
		2421
		2422	This slightly arcane module is used to implement fast signal handling: To
		2423	my knowledge, there is no way to do completely race-free and quick
		2424	signal handling in pure perl. To ensure that signals still get
		2425	delivered, AnyEvent will start an interval timer to wake up perl (and
		2426	catch the signals) with some delay (default is 10 seconds, look for
		2427	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2428
		2429	If this module is available, then it will be used to implement signal
		2430	catching, which means that signals will not be delayed, and the event loop
		2431	will not be interrupted regularly, which is more efficient (And good for
		2432	battery life on laptops).
		2433
		2434	This affects not just the pure-perl event loop, but also other event loops
		2435	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2436
		2437	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2438	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2439	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2440	does nothing for those backends.
		2441
		2442	=item L<EV>
		2443
		2444	This module isn't really "optional", as it is simply one of the backend
		2445	event loops that AnyEvent can use. However, it is simply the best event
		2446	loop available in terms of features, speed and stability: It supports
		2447	the AnyEvent API optimally, implements all the watcher types in XS, does
		2448	automatic timer adjustments even when no monotonic clock is available,
		2449	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2450	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2451	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2452
		2453	=item L<Guard>
		2454
		2455	The guard module, when used, will be used to implement
		2456	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2457	lot less memory), but otherwise doesn't affect guard operation much. It is
		2458	purely used for performance.
		2459
		2460	=item L<JSON> and L<JSON::XS>
		2461
		2462	This module is required when you want to read or write JSON data via
		2463	L<AnyEvent::Handle>. It is also written in pure-perl, but can take
		2464	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2465
		2466	In fact, L<AnyEvent::Handle> will use L<JSON::XS> by default if it is
		2467	installed.
		2468
		2469	=item L<Net::SSLeay>
		2470
		2471	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2472	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2473	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2474
		2475	=item L<Time::HiRes>
		2476
		2477	This module is part of perl since release 5.008. It will be used when the
		2478	chosen event library does not come with a timing source on it's own. The
		2479	pure-perl event loop (L<AnyEvent::Impl::Perl>) will additionally use it to
		2480	try to use a monotonic clock for timing stability.
		2481
		2482	=back
		2483
1151		2484
1152	=head1 FORK	2485	=head1 FORK
1153		2486
1154	Most event libraries are not fork-safe. The ones who are usually are	2487	Most event libraries are not fork-safe. The ones who are usually are
1155	because they are so inefficient. Only L<EV> is fully fork-aware.	2488	because they rely on inefficient but fork-safe C<select> or C<poll>
		2489	calls. Only L<EV> is fully fork-aware.
1156		2490
1157	If you have to fork, you must either do so I<before> creating your first	2491	If you have to fork, you must either do so I<before> creating your first
1158	watcher OR you must not use AnyEvent at all in the child.	2492	watcher OR you must not use AnyEvent at all in the child OR you must do
		2493	something completely out of the scope of AnyEvent.
1159		2494
1160		2495
1161	=head1 SECURITY CONSIDERATIONS	2496	=head1 SECURITY CONSIDERATIONS
1162		2497
1163	AnyEvent can be forced to load any event model via	2498	AnyEvent can be forced to load any event model via
…		…
1168	specified in the variable.	2503	specified in the variable.
1169		2504
1170	You can make AnyEvent completely ignore this variable by deleting it	2505	You can make AnyEvent completely ignore this variable by deleting it
1171	before the first watcher gets created, e.g. with a C<BEGIN> block:	2506	before the first watcher gets created, e.g. with a C<BEGIN> block:
1172		2507
1173	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	2508	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1174		2509
1175	use AnyEvent;	2510	use AnyEvent;
		2511
		2512	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		2513	be used to probe what backend is used and gain other information (which is
		2514	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2515	$ENV{PERL_ANYEVENT_STRICT}.
		2516
		2517	Note that AnyEvent will remove I<all> environment variables starting with
		2518	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2519	enabled.
		2520
		2521
		2522	=head1 BUGS
		2523
		2524	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2525	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2526	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2527	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2528	pronounced).
1176		2529
1177		2530
1178	=head1 SEE ALSO	2531	=head1 SEE ALSO
1179		2532
1180	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	2533	Utility functions: L<AnyEvent::Util>.
1181	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,	2534
		2535	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
1182	L<Event::Lib>, L<Qt>, L<POE>.	2536	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
1183		2537
1184	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	2538	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
		2539	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
		2540	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1185	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,	2541	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>, L<Anyevent::Impl::Irssi>.
1186	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,
1187	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.
1188		2542
		2543	Non-blocking file handles, sockets, TCP clients and
		2544	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
		2545
		2546	Asynchronous DNS: L<AnyEvent::DNS>.
		2547
		2548	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>,
		2549	L<Coro::Event>,
		2550
1189	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	2551	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::XMPP>,
		2552	L<AnyEvent::HTTP>.
1190		2553
1191		2554
1192	=head1 AUTHOR	2555	=head1 AUTHOR
1193		2556
1194	Marc Lehmann <schmorp@schmorp.de>	2557	Marc Lehmann <schmorp@schmorp.de>
1195	http://home.schmorp.de/	2558	http://home.schmorp.de/
1196		2559
1197	=cut	2560	=cut
1198		2561
1199	1	2562	1
1200		2563

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