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Revision 1.300 by root, Tue Dec 1 17:56:28 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<Tk>, L<AnyEvent::Impl::Perl>, 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 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
90	found, AnyEvent will fall back to a pure-perl event loop, which is not	127	found, AnyEvent will fall back to a pure-perl event loop, which is not
91	very efficient, but should work everywhere.	128	very efficient, but should work everywhere.
92		129
…		…
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 IO WATCHERS	184	=head2 I/O WATCHERS
		185
		186	$w = AnyEvent->io (
		187	fh => <filehandle_or_fileno>,
		188	poll => <"r" or "w">,
		189	cb => <callback>,
		190	);
142		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 for	195	C<fh> is the Perl I<file handle> (or a naked file descriptor) to watch
		196	for events (AnyEvent might or might not keep a reference to this file
		197	handle). Note that only file handles pointing to things for which
		198	non-blocking operation makes sense are allowed. This includes sockets,
		199	most character devices, pipes, fifos and so on, but not for example files
		200	or block devices.
		201
147	events. C<poll> must be a string that is either C<r> or C<w>, which	202	C<poll> must be a string that is either C<r> or C<w>, which creates a
148	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	As long as the I/O watcher exists it will keep the file descriptor or a	207	Although the callback might get passed parameters, their value and
153	copy of it alive/open.	208	presence is undefined and you cannot rely on them. Portable AnyEvent
		209	callbacks cannot use arguments passed to I/O watcher callbacks.
154		210
		211	The I/O watcher might use the underlying file descriptor or a copy of it.
155	It is not allowed to close a file handle as long as any watcher is active	212	You must not close a file handle as long as any watcher is active on the
156	on the underlying file descriptor.	213	underlying file descriptor.
157		214
158	Some event loops issue spurious readyness notifications, so you should	215	Some event loops issue spurious readyness notifications, so you should
159	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
160	handles.	217	handles.
161		218
162	Example:
163
164	# 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
165	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	222	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
166	chomp (my $input = <STDIN>);	223	chomp (my $input = <STDIN>);
167	warn "read: $input\n";	224	warn "read: $input\n";
168	undef $w;	225	undef $w;
169	});	226	});
170		227
171	=head2 TIME WATCHERS	228	=head2 TIME WATCHERS
172		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
173	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 >>
174	method with the following mandatory arguments:	239	method with the following mandatory arguments:
175		240
176	C<after> specifies after how many seconds (fractional values are	241	C<after> specifies after how many seconds (fractional values are
177	supported) should the timer activate. C<cb> the callback to invoke in that	242	supported) the callback should be invoked. C<cb> is the callback to invoke
178	case.	243	in that case.
179		244
180	The timer callback will be invoked at most once: if you want a repeating	245	Although the callback might get passed parameters, their value and
181	timer you have to create a new watcher (this is a limitation by both Tk	246	presence is undefined and you cannot rely on them. Portable AnyEvent
182	and Glib).	247	callbacks cannot use arguments passed to time watcher callbacks.
183		248
184	Example:	249	The callback will normally be invoked once only. If you specify another
		250	parameter, C<interval>, as a strictly positive number (> 0), then the
		251	callback will be invoked regularly at that interval (in fractional
		252	seconds) after the first invocation. If C<interval> is specified with a
		253	false value, then it is treated as if it were missing.
185		254
		255	The callback will be rescheduled before invoking the callback, but no
		256	attempt is done to avoid timer drift in most backends, so the interval is
		257	only approximate.
		258
186	# fire an event after 7.7 seconds	259	Example: fire an event after 7.7 seconds.
		260
187	my $w = AnyEvent->timer (after => 7.7, cb => sub {	261	my $w = AnyEvent->timer (after => 7.7, cb => sub {
188	warn "timeout\n";	262	warn "timeout\n";
189	});	263	});
190		264
191	# to cancel the timer:	265	# to cancel the timer:
192	undef $w;	266	undef $w;
193		267
194	Example 2:
195
196	# 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.
197	my $w;
198		269
199	my $cb = sub {
200	# cancel the old timer while creating a new one
201	$w = AnyEvent->timer (after => 1, cb => $cb);	270	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		271	warn "timeout\n";
202	};	272	};
203
204	# start the "loop" by creating the first watcher
205	$w = AnyEvent->timer (after => 0.5, cb => $cb);
206		273
207	=head3 TIMING ISSUES	274	=head3 TIMING ISSUES
208		275
209	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
210	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
…		…
222	timers.	289	timers.
223		290
224	AnyEvent always prefers relative timers, if available, matching the	291	AnyEvent always prefers relative timers, if available, matching the
225	AnyEvent API.	292	AnyEvent API.
226		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	A typical example would be a script in a web server (e.g. C<mod_perl>) -
		369	when mod_perl executes the script, then the event loop will have the wrong
		370	idea about the "current time" (being potentially far in the past, when the
		371	script ran the last time). In that case you should arrange a call to C<<
		372	AnyEvent->now_update >> each time the web server process wakes up again
		373	(e.g. at the start of your script, or in a handler).
		374
		375	Note that updating the time I<might> cause some events to be handled.
		376
		377	=back
		378
227	=head2 SIGNAL WATCHERS	379	=head2 SIGNAL WATCHERS
228		380
		381	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		382
229	You can watch for signals using a signal watcher, C<signal> is the signal	383	You can watch for signals using a signal watcher, C<signal> is the signal
230	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to	384	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
231	be invoked whenever a signal occurs.	385	callback to be invoked whenever a signal occurs.
232		386
		387	Although the callback might get passed parameters, their value and
		388	presence is undefined and you cannot rely on them. Portable AnyEvent
		389	callbacks cannot use arguments passed to signal watcher callbacks.
		390
233	Multiple signal occurances can be clumped together into one callback	391	Multiple signal occurrences can be clumped together into one callback
234	invocation, and callback invocation will be synchronous. synchronous means	392	invocation, and callback invocation will be synchronous. Synchronous means
235	that it might take a while until the signal gets handled by the process,	393	that it might take a while until the signal gets handled by the process,
236	but it is guarenteed not to interrupt any other callbacks.	394	but it is guaranteed not to interrupt any other callbacks.
237		395
238	The main advantage of using these watchers is that you can share a signal	396	The main advantage of using these watchers is that you can share a signal
239	between multiple watchers.	397	between multiple watchers, and AnyEvent will ensure that signals will not
		398	interrupt your program at bad times.
240		399
241	This watcher might use C<%SIG>, so programs overwriting those signals	400	This watcher might use C<%SIG> (depending on the event loop used),
242	directly will likely not work correctly.	401	so programs overwriting those signals directly will likely not work
		402	correctly.
243		403
244	Example: exit on SIGINT	404	Example: exit on SIGINT
245		405
246	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	406	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
247		407
		408	=head3 Restart Behaviour
		409
		410	While restart behaviour is up to the event loop implementation, most will
		411	not restart syscalls (that includes L<Async::Interrupt> and AnyEvent's
		412	pure perl implementation).
		413
		414	=head3 Safe/Unsafe Signals
		415
		416	Perl signals can be either "safe" (synchronous to opcode handling) or
		417	"unsafe" (asynchronous) - the former might get delayed indefinitely, the
		418	latter might corrupt your memory.
		419
		420	AnyEvent signal handlers are, in addition, synchronous to the event loop,
		421	i.e. they will not interrupt your running perl program but will only be
		422	called as part of the normal event handling (just like timer, I/O etc.
		423	callbacks, too).
		424
		425	=head3 Signal Races, Delays and Workarounds
		426
		427	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		428	callbacks to signals in a generic way, which is a pity, as you cannot
		429	do race-free signal handling in perl, requiring C libraries for
		430	this. AnyEvent will try to do it's best, which means in some cases,
		431	signals will be delayed. The maximum time a signal might be delayed is
		432	specified in C<$AnyEvent::MAX_SIGNAL_LATENCY> (default: 10 seconds). This
		433	variable can be changed only before the first signal watcher is created,
		434	and should be left alone otherwise. This variable determines how often
		435	AnyEvent polls for signals (in case a wake-up was missed). Higher values
		436	will cause fewer spurious wake-ups, which is better for power and CPU
		437	saving.
		438
		439	All these problems can be avoided by installing the optional
		440	L<Async::Interrupt> module, which works with most event loops. It will not
		441	work with inherently broken event loops such as L<Event> or L<Event::Lib>
		442	(and not with L<POE> currently, as POE does it's own workaround with
		443	one-second latency). For those, you just have to suffer the delays.
		444
248	=head2 CHILD PROCESS WATCHERS	445	=head2 CHILD PROCESS WATCHERS
249		446
		447	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		448
250	You can also watch on a child process exit and catch its exit status.	449	You can also watch on a child process exit and catch its exit status.
251		450
252	The child process is specified by the C<pid> argument (if set to C<0>, it	451	The child process is specified by the C<pid> argument (one some backends,
253	watches for any child process exit). The watcher will trigger as often	452	using C<0> watches for any child process exit, on others this will
254	as status change for the child are received. This works by installing a	453	croak). The watcher will be triggered only when the child process has
255	signal handler for C<SIGCHLD>. The callback will be called with the pid	454	finished and an exit status is available, not on any trace events
256	and exit status (as returned by waitpid).	455	(stopped/continued).
257		456
258	Example: wait for pid 1333	457	The callback will be called with the pid and exit status (as returned by
		458	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		459	callback arguments.
259		460
		461	This watcher type works by installing a signal handler for C<SIGCHLD>,
		462	and since it cannot be shared, nothing else should use SIGCHLD or reap
		463	random child processes (waiting for specific child processes, e.g. inside
		464	C<system>, is just fine).
		465
		466	There is a slight catch to child watchers, however: you usually start them
		467	I<after> the child process was created, and this means the process could
		468	have exited already (and no SIGCHLD will be sent anymore).
		469
		470	Not all event models handle this correctly (neither POE nor IO::Async do,
		471	see their AnyEvent::Impl manpages for details), but even for event models
		472	that I<do> handle this correctly, they usually need to be loaded before
		473	the process exits (i.e. before you fork in the first place). AnyEvent's
		474	pure perl event loop handles all cases correctly regardless of when you
		475	start the watcher.
		476
		477	This means you cannot create a child watcher as the very first
		478	thing in an AnyEvent program, you I<have> to create at least one
		479	watcher before you C<fork> the child (alternatively, you can call
		480	C<AnyEvent::detect>).
		481
		482	As most event loops do not support waiting for child events, they will be
		483	emulated by AnyEvent in most cases, in which the latency and race problems
		484	mentioned in the description of signal watchers apply.
		485
		486	Example: fork a process and wait for it
		487
		488	my $done = AnyEvent->condvar;
		489
		490	my $pid = fork or exit 5;
		491
260	my $w = AnyEvent->child (	492	my $w = AnyEvent->child (
261	pid => 1333,	493	pid => $pid,
262	cb => sub {	494	cb => sub {
263	my ($pid, $status) = @_;	495	my ($pid, $status) = @_;
264	warn "pid $pid exited with status $status";	496	warn "pid $pid exited with status $status";
		497	$done->send;
265	},	498	},
266	);	499	);
		500
		501	# do something else, then wait for process exit
		502	$done->recv;
		503
		504	=head2 IDLE WATCHERS
		505
		506	$w = AnyEvent->idle (cb => <callback>);
		507
		508	Sometimes there is a need to do something, but it is not so important
		509	to do it instantly, but only when there is nothing better to do. This
		510	"nothing better to do" is usually defined to be "no other events need
		511	attention by the event loop".
		512
		513	Idle watchers ideally get invoked when the event loop has nothing
		514	better to do, just before it would block the process to wait for new
		515	events. Instead of blocking, the idle watcher is invoked.
		516
		517	Most event loops unfortunately do not really support idle watchers (only
		518	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		519	will simply call the callback "from time to time".
		520
		521	Example: read lines from STDIN, but only process them when the
		522	program is otherwise idle:
		523
		524	my @lines; # read data
		525	my $idle_w;
		526	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		527	push @lines, scalar <STDIN>;
		528
		529	# start an idle watcher, if not already done
		530	$idle_w ||= AnyEvent->idle (cb => sub {
		531	# handle only one line, when there are lines left
		532	if (my $line = shift @lines) {
		533	print "handled when idle: $line";
		534	} else {
		535	# otherwise disable the idle watcher again
		536	undef $idle_w;
		537	}
		538	});
		539	});
267		540
268	=head2 CONDITION VARIABLES	541	=head2 CONDITION VARIABLES
269		542
		543	$cv = AnyEvent->condvar;
		544
		545	$cv->send (<list>);
		546	my @res = $cv->recv;
		547
		548	If you are familiar with some event loops you will know that all of them
		549	require you to run some blocking "loop", "run" or similar function that
		550	will actively watch for new events and call your callbacks.
		551
		552	AnyEvent is slightly different: it expects somebody else to run the event
		553	loop and will only block when necessary (usually when told by the user).
		554
		555	The instrument to do that is called a "condition variable", so called
		556	because they represent a condition that must become true.
		557
		558	Now is probably a good time to look at the examples further below.
		559
270	Condition variables can be created by calling the C<< AnyEvent->condvar >>	560	Condition variables can be created by calling the C<< AnyEvent->condvar
271	method without any arguments.	561	>> method, usually without arguments. The only argument pair allowed is
		562	C<cb>, which specifies a callback to be called when the condition variable
		563	becomes true, with the condition variable as the first argument (but not
		564	the results).
272		565
273	A condition variable waits for a condition - precisely that the C<<	566	After creation, the condition variable is "false" until it becomes "true"
274	->broadcast >> method has been called.	567	by calling the C<send> method (or calling the condition variable as if it
		568	were a callback, read about the caveats in the description for the C<<
		569	->send >> method).
275		570
276	They are very useful to signal that a condition has been fulfilled, for	571	Condition variables are similar to callbacks, except that you can
		572	optionally wait for them. They can also be called merge points - points
		573	in time where multiple outstanding events have been processed. And yet
		574	another way to call them is transactions - each condition variable can be
		575	used to represent a transaction, which finishes at some point and delivers
		576	a result. And yet some people know them as "futures" - a promise to
		577	compute/deliver something that you can wait for.
		578
		579	Condition variables are very useful to signal that something has finished,
277	example, if you write a module that does asynchronous http requests,	580	for example, if you write a module that does asynchronous http requests,
278	then a condition variable would be the ideal candidate to signal the	581	then a condition variable would be the ideal candidate to signal the
279	availability of results.	582	availability of results. The user can either act when the callback is
		583	called or can synchronously C<< ->recv >> for the results.
280		584
281	You can also use condition variables to block your main program until	585	You can also use them to simulate traditional event loops - for example,
282	an event occurs - for example, you could C<< ->wait >> in your main	586	you can block your main program until an event occurs - for example, you
283	program until the user clicks the Quit button in your app, which would C<<	587	could C<< ->recv >> in your main program until the user clicks the Quit
284	->broadcast >> the "quit" event.	588	button of your app, which would C<< ->send >> the "quit" event.
285		589
286	Note that condition variables recurse into the event loop - if you have	590	Note that condition variables recurse into the event loop - if you have
287	two pirces of code that call C<< ->wait >> in a round-robbin fashion, you	591	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
288	lose. Therefore, condition variables are good to export to your caller, but	592	lose. Therefore, condition variables are good to export to your caller, but
289	you should avoid making a blocking wait yourself, at least in callbacks,	593	you should avoid making a blocking wait yourself, at least in callbacks,
290	as this asks for trouble.	594	as this asks for trouble.
291		595
292	This object has two methods:	596	Condition variables are represented by hash refs in perl, and the keys
		597	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
		598	easy (it is often useful to build your own transaction class on top of
		599	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
		600	it's C<new> method in your own C<new> method.
293		601
294	=over 4	602	There are two "sides" to a condition variable - the "producer side" which
		603	eventually calls C<< -> send >>, and the "consumer side", which waits
		604	for the send to occur.
295		605
296	=item $cv->wait	606	Example: wait for a timer.
297
298	Wait (blocking if necessary) until the C<< ->broadcast >> method has been
299	called on c<$cv>, while servicing other watchers normally.
300
301	You can only wait once on a condition - additional calls will return
302	immediately.
303
304	Not all event models support a blocking wait - some die in that case
305	(programs might want to do that to stay interactive), so I<if you are
306	using this from a module, never require a blocking wait>, but let the
307	caller decide whether the call will block or not (for example, by coupling
308	condition variables with some kind of request results and supporting
309	callbacks so the caller knows that getting the result will not block,
310	while still suppporting blocking waits if the caller so desires).
311
312	Another reason I<never> to C<< ->wait >> in a module is that you cannot
313	sensibly have two C<< ->wait >>'s in parallel, as that would require
314	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
315	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and
316	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
317	from different coroutines, however).
318
319	=item $cv->broadcast
320
321	Flag the condition as ready - a running C<< ->wait >> and all further
322	calls to C<wait> will (eventually) return after this method has been
323	called. If nobody is waiting the broadcast will be remembered..
324
325	=back
326
327	Example:
328		607
329	# wait till the result is ready	608	# wait till the result is ready
330	my $result_ready = AnyEvent->condvar;	609	my $result_ready = AnyEvent->condvar;
331		610
332	# do something such as adding a timer	611	# do something such as adding a timer
333	# or socket watcher the calls $result_ready->broadcast	612	# or socket watcher the calls $result_ready->send
334	# when the "result" is ready.	613	# when the "result" is ready.
335	# in this case, we simply use a timer:	614	# in this case, we simply use a timer:
336	my $w = AnyEvent->timer (	615	my $w = AnyEvent->timer (
337	after => 1,	616	after => 1,
338	cb => sub { $result_ready->broadcast },	617	cb => sub { $result_ready->send },
339	);	618	);
340		619
341	# this "blocks" (while handling events) till the watcher	620	# this "blocks" (while handling events) till the callback
342	# calls broadcast	621	# calls ->send
343	$result_ready->wait;	622	$result_ready->recv;
		623
		624	Example: wait for a timer, but take advantage of the fact that condition
		625	variables are also callable directly.
		626
		627	my $done = AnyEvent->condvar;
		628	my $delay = AnyEvent->timer (after => 5, cb => $done);
		629	$done->recv;
		630
		631	Example: Imagine an API that returns a condvar and doesn't support
		632	callbacks. This is how you make a synchronous call, for example from
		633	the main program:
		634
		635	use AnyEvent::CouchDB;
		636
		637	...
		638
		639	my @info = $couchdb->info->recv;
		640
		641	And this is how you would just set a callback to be called whenever the
		642	results are available:
		643
		644	$couchdb->info->cb (sub {
		645	my @info = $_[0]->recv;
		646	});
		647
		648	=head3 METHODS FOR PRODUCERS
		649
		650	These methods should only be used by the producing side, i.e. the
		651	code/module that eventually sends the signal. Note that it is also
		652	the producer side which creates the condvar in most cases, but it isn't
		653	uncommon for the consumer to create it as well.
		654
		655	=over 4
		656
		657	=item $cv->send (...)
		658
		659	Flag the condition as ready - a running C<< ->recv >> and all further
		660	calls to C<recv> will (eventually) return after this method has been
		661	called. If nobody is waiting the send will be remembered.
		662
		663	If a callback has been set on the condition variable, it is called
		664	immediately from within send.
		665
		666	Any arguments passed to the C<send> call will be returned by all
		667	future C<< ->recv >> calls.
		668
		669	Condition variables are overloaded so one can call them directly (as if
		670	they were a code reference). Calling them directly is the same as calling
		671	C<send>.
		672
		673	=item $cv->croak ($error)
		674
		675	Similar to send, but causes all call's to C<< ->recv >> to invoke
		676	C<Carp::croak> with the given error message/object/scalar.
		677
		678	This can be used to signal any errors to the condition variable
		679	user/consumer. Doing it this way instead of calling C<croak> directly
		680	delays the error detetcion, but has the overwhelmign advantage that it
		681	diagnoses the error at the place where the result is expected, and not
		682	deep in some event clalback without connection to the actual code causing
		683	the problem.
		684
		685	=item $cv->begin ([group callback])
		686
		687	=item $cv->end
		688
		689	These two methods can be used to combine many transactions/events into
		690	one. For example, a function that pings many hosts in parallel might want
		691	to use a condition variable for the whole process.
		692
		693	Every call to C<< ->begin >> will increment a counter, and every call to
		694	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
		695	>>, the (last) callback passed to C<begin> will be executed, passing the
		696	condvar as first argument. That callback is I<supposed> to call C<< ->send
		697	>>, but that is not required. If no group callback was set, C<send> will
		698	be called without any arguments.
		699
		700	You can think of C<< $cv->send >> giving you an OR condition (one call
		701	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		702	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		703
		704	Let's start with a simple example: you have two I/O watchers (for example,
		705	STDOUT and STDERR for a program), and you want to wait for both streams to
		706	close before activating a condvar:
		707
		708	my $cv = AnyEvent->condvar;
		709
		710	$cv->begin; # first watcher
		711	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		712	defined sysread $fh1, my $buf, 4096
		713	or $cv->end;
		714	});
		715
		716	$cv->begin; # second watcher
		717	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		718	defined sysread $fh2, my $buf, 4096
		719	or $cv->end;
		720	});
		721
		722	$cv->recv;
		723
		724	This works because for every event source (EOF on file handle), there is
		725	one call to C<begin>, so the condvar waits for all calls to C<end> before
		726	sending.
		727
		728	The ping example mentioned above is slightly more complicated, as the
		729	there are results to be passwd back, and the number of tasks that are
		730	begung can potentially be zero:
		731
		732	my $cv = AnyEvent->condvar;
		733
		734	my %result;
		735	$cv->begin (sub { shift->send (\%result) });
		736
		737	for my $host (@list_of_hosts) {
		738	$cv->begin;
		739	ping_host_then_call_callback $host, sub {
		740	$result{$host} = ...;
		741	$cv->end;
		742	};
		743	}
		744
		745	$cv->end;
		746
		747	This code fragment supposedly pings a number of hosts and calls
		748	C<send> after results for all then have have been gathered - in any
		749	order. To achieve this, the code issues a call to C<begin> when it starts
		750	each ping request and calls C<end> when it has received some result for
		751	it. Since C<begin> and C<end> only maintain a counter, the order in which
		752	results arrive is not relevant.
		753
		754	There is an additional bracketing call to C<begin> and C<end> outside the
		755	loop, which serves two important purposes: first, it sets the callback
		756	to be called once the counter reaches C<0>, and second, it ensures that
		757	C<send> is called even when C<no> hosts are being pinged (the loop
		758	doesn't execute once).
		759
		760	This is the general pattern when you "fan out" into multiple (but
		761	potentially none) subrequests: use an outer C<begin>/C<end> pair to set
		762	the callback and ensure C<end> is called at least once, and then, for each
		763	subrequest you start, call C<begin> and for each subrequest you finish,
		764	call C<end>.
		765
		766	=back
		767
		768	=head3 METHODS FOR CONSUMERS
		769
		770	These methods should only be used by the consuming side, i.e. the
		771	code awaits the condition.
		772
		773	=over 4
		774
		775	=item $cv->recv
		776
		777	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
		778	>> methods have been called on c<$cv>, while servicing other watchers
		779	normally.
		780
		781	You can only wait once on a condition - additional calls are valid but
		782	will return immediately.
		783
		784	If an error condition has been set by calling C<< ->croak >>, then this
		785	function will call C<croak>.
		786
		787	In list context, all parameters passed to C<send> will be returned,
		788	in scalar context only the first one will be returned.
		789
		790	Note that doing a blocking wait in a callback is not supported by any
		791	event loop, that is, recursive invocation of a blocking C<< ->recv
		792	>> is not allowed, and the C<recv> call will C<croak> if such a
		793	condition is detected. This condition can be slightly loosened by using
		794	L<Coro::AnyEvent>, which allows you to do a blocking C<< ->recv >> from
		795	any thread that doesn't run the event loop itself.
		796
		797	Not all event models support a blocking wait - some die in that case
		798	(programs might want to do that to stay interactive), so I<if you are
		799	using this from a module, never require a blocking wait>. Instead, let the
		800	caller decide whether the call will block or not (for example, by coupling
		801	condition variables with some kind of request results and supporting
		802	callbacks so the caller knows that getting the result will not block,
		803	while still supporting blocking waits if the caller so desires).
		804
		805	You can ensure that C<< -recv >> never blocks by setting a callback and
		806	only calling C<< ->recv >> from within that callback (or at a later
		807	time). This will work even when the event loop does not support blocking
		808	waits otherwise.
		809
		810	=item $bool = $cv->ready
		811
		812	Returns true when the condition is "true", i.e. whether C<send> or
		813	C<croak> have been called.
		814
		815	=item $cb = $cv->cb ($cb->($cv))
		816
		817	This is a mutator function that returns the callback set and optionally
		818	replaces it before doing so.
		819
		820	The callback will be called when the condition becomes (or already was)
		821	"true", i.e. when C<send> or C<croak> are called (or were called), with
		822	the only argument being the condition variable itself. Calling C<recv>
		823	inside the callback or at any later time is guaranteed not to block.
		824
		825	=back
		826
		827	=head1 SUPPORTED EVENT LOOPS/BACKENDS
		828
		829	The available backend classes are (every class has its own manpage):
		830
		831	=over 4
		832
		833	=item Backends that are autoprobed when no other event loop can be found.
		834
		835	EV is the preferred backend when no other event loop seems to be in
		836	use. If EV is not installed, then AnyEvent will fall back to its own
		837	pure-perl implementation, which is available everywhere as it comes with
		838	AnyEvent itself.
		839
		840	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		841	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
		842
		843	=item Backends that are transparently being picked up when they are used.
		844
		845	These will be used when they are currently loaded when the first watcher
		846	is created, in which case it is assumed that the application is using
		847	them. This means that AnyEvent will automatically pick the right backend
		848	when the main program loads an event module before anything starts to
		849	create watchers. Nothing special needs to be done by the main program.
		850
		851	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		852	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		853	AnyEvent::Impl::Tk based on Tk, very broken.
		854	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		855	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		856	AnyEvent::Impl::Irssi used when running within irssi.
		857
		858	=item Backends with special needs.
		859
		860	Qt requires the Qt::Application to be instantiated first, but will
		861	otherwise be picked up automatically. As long as the main program
		862	instantiates the application before any AnyEvent watchers are created,
		863	everything should just work.
		864
		865	AnyEvent::Impl::Qt based on Qt.
		866
		867	Support for IO::Async can only be partial, as it is too broken and
		868	architecturally limited to even support the AnyEvent API. It also
		869	is the only event loop that needs the loop to be set explicitly, so
		870	it can only be used by a main program knowing about AnyEvent. See
		871	L<AnyEvent::Impl::Async> for the gory details.
		872
		873	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
		874
		875	=item Event loops that are indirectly supported via other backends.
		876
		877	Some event loops can be supported via other modules:
		878
		879	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		880
		881	B<WxWidgets> has no support for watching file handles. However, you can
		882	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		883	polls 20 times per second, which was considered to be too horrible to even
		884	consider for AnyEvent.
		885
		886	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		887	backend, so it can be supported through POE.
		888
		889	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		890	load L<POE> when detecting them, in the hope that POE will pick them up,
		891	in which case everything will be automatic.
		892
		893	=back
344		894
345	=head1 GLOBAL VARIABLES AND FUNCTIONS	895	=head1 GLOBAL VARIABLES AND FUNCTIONS
346		896
		897	These are not normally required to use AnyEvent, but can be useful to
		898	write AnyEvent extension modules.
		899
347	=over 4	900	=over 4
348		901
349	=item $AnyEvent::MODEL	902	=item $AnyEvent::MODEL
350		903
351	Contains C<undef> until the first watcher is being created. Then it	904	Contains C<undef> until the first watcher is being created, before the
		905	backend has been autodetected.
		906
352	contains the event model that is being used, which is the name of the	907	Afterwards it contains the event model that is being used, which is the
353	Perl class implementing the model. This class is usually one of the	908	name of the Perl class implementing the model. This class is usually one
354	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	909	of the C<AnyEvent::Impl:xxx> modules, but can be any other class in the
355	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	910	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
356		911	will be C<urxvt::anyevent>).
357	The known classes so far are:
358
359	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
360	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
361	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
362	AnyEvent::Impl::Event based on Event, second best choice.
363	AnyEvent::Impl::Glib based on Glib, third-best choice.
364	AnyEvent::Impl::Tk based on Tk, very bad choice.
365	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
366	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
367	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
368	AnyEvent::Impl::POE based on POE, not generic enough for full support.
369
370	There is no support for WxWidgets, as WxWidgets has no support for
371	watching file handles. However, you can use WxWidgets through the
372	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
373	second, which was considered to be too horrible to even consider for
374	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
375	it's adaptor.
376
377	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
378	autodetecting them.
379		912
380	=item AnyEvent::detect	913	=item AnyEvent::detect
381		914
382	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	915	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
383	if necessary. You should only call this function right before you would	916	if necessary. You should only call this function right before you would
384	have created an AnyEvent watcher anyway, that is, as late as possible at	917	have created an AnyEvent watcher anyway, that is, as late as possible at
385	runtime.	918	runtime, and not e.g. while initialising of your module.
		919
		920	If you need to do some initialisation before AnyEvent watchers are
		921	created, use C<post_detect>.
		922
		923	=item $guard = AnyEvent::post_detect { BLOCK }
		924
		925	Arranges for the code block to be executed as soon as the event model is
		926	autodetected (or immediately if this has already happened).
		927
		928	The block will be executed I<after> the actual backend has been detected
		929	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		930	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		931	other initialisations - see the sources of L<AnyEvent::Strict> or
		932	L<AnyEvent::AIO> to see how this is used.
		933
		934	The most common usage is to create some global watchers, without forcing
		935	event module detection too early, for example, L<AnyEvent::AIO> creates
		936	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		937	avoid autodetecting the event module at load time.
		938
		939	If called in scalar or list context, then it creates and returns an object
		940	that automatically removes the callback again when it is destroyed (or
		941	C<undef> when the hook was immediately executed). See L<AnyEvent::AIO> for
		942	a case where this is useful.
		943
		944	Example: Create a watcher for the IO::AIO module and store it in
		945	C<$WATCHER>. Only do so after the event loop is initialised, though.
		946
		947	our WATCHER;
		948
		949	my $guard = AnyEvent::post_detect {
		950	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		951	};
		952
		953	# the ||= is important in case post_detect immediately runs the block,
		954	# as to not clobber the newly-created watcher. assigning both watcher and
		955	# post_detect guard to the same variable has the advantage of users being
		956	# able to just C<undef $WATCHER> if the watcher causes them grief.
		957
		958	$WATCHER ||= $guard;
		959
		960	=item @AnyEvent::post_detect
		961
		962	If there are any code references in this array (you can C<push> to it
		963	before or after loading AnyEvent), then they will called directly after
		964	the event loop has been chosen.
		965
		966	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		967	if it is defined then the event loop has already been detected, and the
		968	array will be ignored.
		969
		970	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		971	it,as it takes care of these details.
		972
		973	This variable is mainly useful for modules that can do something useful
		974	when AnyEvent is used and thus want to know when it is initialised, but do
		975	not need to even load it by default. This array provides the means to hook
		976	into AnyEvent passively, without loading it.
386		977
387	=back	978	=back
388		979
389	=head1 WHAT TO DO IN A MODULE	980	=head1 WHAT TO DO IN A MODULE
390		981
…		…
394	Be careful when you create watchers in the module body - AnyEvent will	985	Be careful when you create watchers in the module body - AnyEvent will
395	decide which event module to use as soon as the first method is called, so	986	decide which event module to use as soon as the first method is called, so
396	by calling AnyEvent in your module body you force the user of your module	987	by calling AnyEvent in your module body you force the user of your module
397	to load the event module first.	988	to load the event module first.
398		989
399	Never call C<< ->wait >> on a condition variable unless you I<know> that	990	Never call C<< ->recv >> on a condition variable unless you I<know> that
400	the C<< ->broadcast >> method has been called on it already. This is	991	the C<< ->send >> method has been called on it already. This is
401	because it will stall the whole program, and the whole point of using	992	because it will stall the whole program, and the whole point of using
402	events is to stay interactive.	993	events is to stay interactive.
403		994
404	It is fine, however, to call C<< ->wait >> when the user of your module	995	It is fine, however, to call C<< ->recv >> when the user of your module
405	requests it (i.e. if you create a http request object ad have a method	996	requests it (i.e. if you create a http request object ad have a method
406	called C<results> that returns the results, it should call C<< ->wait >>	997	called C<results> that returns the results, it should call C<< ->recv >>
407	freely, as the user of your module knows what she is doing. always).	998	freely, as the user of your module knows what she is doing. always).
408		999
409	=head1 WHAT TO DO IN THE MAIN PROGRAM	1000	=head1 WHAT TO DO IN THE MAIN PROGRAM
410		1001
411	There will always be a single main program - the only place that should	1002	There will always be a single main program - the only place that should
…		…
413		1004
414	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	1005	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
415	do anything special (it does not need to be event-based) and let AnyEvent	1006	do anything special (it does not need to be event-based) and let AnyEvent
416	decide which implementation to chose if some module relies on it.	1007	decide which implementation to chose if some module relies on it.
417		1008
418	If the main program relies on a specific event model. For example, in	1009	If the main program relies on a specific event model - for example, in
419	Gtk2 programs you have to rely on the Glib module. You should load the	1010	Gtk2 programs you have to rely on the Glib module - you should load the
420	event module before loading AnyEvent or any module that uses it: generally	1011	event module before loading AnyEvent or any module that uses it: generally
421	speaking, you should load it as early as possible. The reason is that	1012	speaking, you should load it as early as possible. The reason is that
422	modules might create watchers when they are loaded, and AnyEvent will	1013	modules might create watchers when they are loaded, and AnyEvent will
423	decide on the event model to use as soon as it creates watchers, and it	1014	decide on the event model to use as soon as it creates watchers, and it
424	might chose the wrong one unless you load the correct one yourself.	1015	might chose the wrong one unless you load the correct one yourself.
425		1016
426	You can chose to use a rather inefficient pure-perl implementation by	1017	You can chose to use a pure-perl implementation by loading the
427	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	1018	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
428	behaviour everywhere, but letting AnyEvent chose is generally better.	1019	everywhere, but letting AnyEvent chose the model is generally better.
		1020
		1021	=head2 MAINLOOP EMULATION
		1022
		1023	Sometimes (often for short test scripts, or even standalone programs who
		1024	only want to use AnyEvent), you do not want to run a specific event loop.
		1025
		1026	In that case, you can use a condition variable like this:
		1027
		1028	AnyEvent->condvar->recv;
		1029
		1030	This has the effect of entering the event loop and looping forever.
		1031
		1032	Note that usually your program has some exit condition, in which case
		1033	it is better to use the "traditional" approach of storing a condition
		1034	variable somewhere, waiting for it, and sending it when the program should
		1035	exit cleanly.
		1036
		1037
		1038	=head1 OTHER MODULES
		1039
		1040	The following is a non-exhaustive list of additional modules that use
		1041	AnyEvent as a client and can therefore be mixed easily with other AnyEvent
		1042	modules and other event loops in the same program. Some of the modules
		1043	come with AnyEvent, most are available via CPAN.
		1044
		1045	=over 4
		1046
		1047	=item L<AnyEvent::Util>
		1048
		1049	Contains various utility functions that replace often-used but blocking
		1050	functions such as C<inet_aton> by event-/callback-based versions.
		1051
		1052	=item L<AnyEvent::Socket>
		1053
		1054	Provides various utility functions for (internet protocol) sockets,
		1055	addresses and name resolution. Also functions to create non-blocking tcp
		1056	connections or tcp servers, with IPv6 and SRV record support and more.
		1057
		1058	=item L<AnyEvent::Handle>
		1059
		1060	Provide read and write buffers, manages watchers for reads and writes,
		1061	supports raw and formatted I/O, I/O queued and fully transparent and
		1062	non-blocking SSL/TLS (via L<AnyEvent::TLS>.
		1063
		1064	=item L<AnyEvent::DNS>
		1065
		1066	Provides rich asynchronous DNS resolver capabilities.
		1067
		1068	=item L<AnyEvent::HTTP>
		1069
		1070	A simple-to-use HTTP library that is capable of making a lot of concurrent
		1071	HTTP requests.
		1072
		1073	=item L<AnyEvent::HTTPD>
		1074
		1075	Provides a simple web application server framework.
		1076
		1077	=item L<AnyEvent::FastPing>
		1078
		1079	The fastest ping in the west.
		1080
		1081	=item L<AnyEvent::DBI>
		1082
		1083	Executes L<DBI> requests asynchronously in a proxy process.
		1084
		1085	=item L<AnyEvent::AIO>
		1086
		1087	Truly asynchronous I/O, should be in the toolbox of every event
		1088	programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
		1089	together.
		1090
		1091	=item L<AnyEvent::BDB>
		1092
		1093	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
		1094	L<BDB> and AnyEvent together.
		1095
		1096	=item L<AnyEvent::GPSD>
		1097
		1098	A non-blocking interface to gpsd, a daemon delivering GPS information.
		1099
		1100	=item L<AnyEvent::IRC>
		1101
		1102	AnyEvent based IRC client module family (replacing the older Net::IRC3).
		1103
		1104	=item L<AnyEvent::XMPP>
		1105
		1106	AnyEvent based XMPP (Jabber protocol) module family (replacing the older
		1107	Net::XMPP2>.
		1108
		1109	=item L<AnyEvent::IGS>
		1110
		1111	A non-blocking interface to the Internet Go Server protocol (used by
		1112	L<App::IGS>).
		1113
		1114	=item L<Net::FCP>
		1115
		1116	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
		1117	of AnyEvent.
		1118
		1119	=item L<Event::ExecFlow>
		1120
		1121	High level API for event-based execution flow control.
		1122
		1123	=item L<Coro>
		1124
		1125	Has special support for AnyEvent via L<Coro::AnyEvent>.
		1126
		1127	=back
429		1128
430	=cut	1129	=cut
431		1130
432	package AnyEvent;	1131	package AnyEvent;
433		1132
434	no warnings;	1133	# basically a tuned-down version of common::sense
435	use strict;	1134	sub common_sense {
		1135	# from common:.sense 1.0
		1136	${^WARNING_BITS} = "\xfc\x3f\xf3\x00\x0f\xf3\xcf\xc0\xf3\xfc\x33\x03";
		1137	# use strict vars subs
		1138	$^H |= 0x00000600;
		1139	}
436		1140
		1141	BEGIN { AnyEvent::common_sense }
		1142
437	use Carp;	1143	use Carp ();
438		1144
439	our $VERSION = '3.3';	1145	our $VERSION = '5.21';
440	our $MODEL;	1146	our $MODEL;
441		1147
442	our $AUTOLOAD;	1148	our $AUTOLOAD;
443	our @ISA;	1149	our @ISA;
444		1150
445	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
446
447	our @REGISTRY;	1151	our @REGISTRY;
448		1152
		1153	our $VERBOSE;
		1154
		1155	BEGIN {
		1156	eval "sub WIN32(){ " . (($^O =~ /mswin32/i)*1) ." }";
		1157	eval "sub TAINT(){ " . (${^TAINT}*1) . " }";
		1158
		1159	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1160	if ${^TAINT};
		1161
		1162	$VERBOSE = $ENV{PERL_ANYEVENT_VERBOSE}*1;
		1163
		1164	}
		1165
		1166	our $MAX_SIGNAL_LATENCY = 10;
		1167
		1168	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		1169
		1170	{
		1171	my $idx;
		1172	$PROTOCOL{$_} = ++$idx
		1173	for reverse split /\s*,\s*/,
		1174	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		1175	}
		1176
449	my @models = (	1177	my @models = (
450	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
451	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
452	[EV:: => AnyEvent::Impl::EV::],	1178	[EV:: => AnyEvent::Impl::EV:: , 1],
		1179	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl:: , 1],
		1180	# everything below here will not (normally) be autoprobed
		1181	# as the pureperl backend should work everywhere
		1182	# and is usually faster
453	[Event:: => AnyEvent::Impl::Event::],	1183	[Event:: => AnyEvent::Impl::Event::, 1],
454	[Glib:: => AnyEvent::Impl::Glib::],	1184	[Glib:: => AnyEvent::Impl::Glib:: , 1], # becomes extremely slow with many watchers
		1185	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		1186	[Irssi:: => AnyEvent::Impl::Irssi::], # Irssi has a bogus "Event" package
455	[Tk:: => AnyEvent::Impl::Tk::],	1187	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		1188	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		1189	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
456	[Wx:: => AnyEvent::Impl::POE::],	1190	[Wx:: => AnyEvent::Impl::POE::],
457	[Prima:: => AnyEvent::Impl::POE::],	1191	[Prima:: => AnyEvent::Impl::POE::],
458	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1192	# IO::Async is just too broken - we would need workarounds for its
459	# everything below here will not be autoprobed as the pureperl backend should work everywhere	1193	# byzantine signal and broken child handling, among others.
460	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy	1194	# IO::Async is rather hard to detect, as it doesn't have any
		1195	# obvious default class.
461	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program	1196	[IO::Async:: => AnyEvent::Impl::IOAsync::], # requires special main program
462	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza	1197	[IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1198	[IO::Async::Notifier:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1199	[AnyEvent::Impl::IOAsync:: => AnyEvent::Impl::IOAsync::], # requires special main program
463	);	1200	);
464		1201
465	our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);	1202	our %method = map +($_ => 1),
		1203	qw(io timer time now now_update signal child idle condvar one_event DESTROY);
		1204
		1205	our @post_detect;
		1206
		1207	sub post_detect(&) {
		1208	my ($cb) = @_;
		1209
		1210	if ($MODEL) {
		1211	$cb->();
		1212
		1213	undef
		1214	} else {
		1215	push @post_detect, $cb;
		1216
		1217	defined wantarray
		1218	? bless \$cb, "AnyEvent::Util::postdetect"
		1219	: ()
		1220	}
		1221	}
		1222
		1223	sub AnyEvent::Util::postdetect::DESTROY {
		1224	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		1225	}
466		1226
467	sub detect() {	1227	sub detect() {
468	unless ($MODEL) {	1228	unless ($MODEL) {
469	no strict 'refs';	1229	local $SIG{__DIE__};
470		1230
471	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	1231	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
472	my $model = "AnyEvent::Impl::$1";	1232	my $model = "AnyEvent::Impl::$1";
473	if (eval "require $model") {	1233	if (eval "require $model") {
474	$MODEL = $model;	1234	$MODEL = $model;
475	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	1235	warn "AnyEvent: loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.\n" if $VERBOSE >= 2;
476	} else {	1236	} else {
477	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;	1237	warn "AnyEvent: unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@" if $VERBOSE;
478	}	1238	}
479	}	1239	}
480		1240
481	# check for already loaded models	1241	# check for already loaded models
482	unless ($MODEL) {	1242	unless ($MODEL) {
483	for (@REGISTRY, @models) {	1243	for (@REGISTRY, @models) {
484	my ($package, $model) = @$_;	1244	my ($package, $model) = @$_;
485	if (${"$package\::VERSION"} > 0) {	1245	if (${"$package\::VERSION"} > 0) {
486	if (eval "require $model") {	1246	if (eval "require $model") {
487	$MODEL = $model;	1247	$MODEL = $model;
488	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;	1248	warn "AnyEvent: autodetected model '$model', using it.\n" if $VERBOSE >= 2;
489	last;	1249	last;
490	}	1250	}
491	}	1251	}
492	}	1252	}
493		1253
494	unless ($MODEL) {	1254	unless ($MODEL) {
495	# try to load a model	1255	# try to autoload a model
496
497	for (@REGISTRY, @models) {	1256	for (@REGISTRY, @models) {
498	my ($package, $model) = @$_;	1257	my ($package, $model, $autoload) = @$_;
		1258	if (
		1259	$autoload
499	if (eval "require $package"	1260	and eval "require $package"
500	and ${"$package\::VERSION"} > 0	1261	and ${"$package\::VERSION"} > 0
501	and eval "require $model") {	1262	and eval "require $model"
		1263	) {
502	$MODEL = $model;	1264	$MODEL = $model;
503	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;	1265	warn "AnyEvent: autoloaded model '$model', using it.\n" if $VERBOSE >= 2;
504	last;	1266	last;
505	}	1267	}
506	}	1268	}
507		1269
508	$MODEL	1270	$MODEL
509	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV (or Coro+EV), Event (or Coro+Event) or Glib.";	1271	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.\n";
510	}	1272	}
511	}	1273	}
512		1274
		1275	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		1276
513	unshift @ISA, $MODEL;	1277	unshift @ISA, $MODEL;
514	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	1278
		1279	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
		1280
		1281	(shift @post_detect)->() while @post_detect;
515	}	1282	}
516		1283
517	$MODEL	1284	$MODEL
518	}	1285	}
519		1286
520	sub AUTOLOAD {	1287	sub AUTOLOAD {
521	(my $func = $AUTOLOAD) =~ s/.*://;	1288	(my $func = $AUTOLOAD) =~ s/.*://;
522		1289
523	$method{$func}	1290	$method{$func}
524	or croak "$func: not a valid method for AnyEvent objects";	1291	or Carp::croak "$func: not a valid method for AnyEvent objects";
525		1292
526	detect unless $MODEL;	1293	detect unless $MODEL;
527		1294
528	my $class = shift;	1295	my $class = shift;
529	$class->$func (@_);	1296	$class->$func (@_);
530	}	1297	}
531		1298
		1299	# utility function to dup a filehandle. this is used by many backends
		1300	# to support binding more than one watcher per filehandle (they usually
		1301	# allow only one watcher per fd, so we dup it to get a different one).
		1302	sub _dupfh($$;$$) {
		1303	my ($poll, $fh, $r, $w) = @_;
		1304
		1305	# cygwin requires the fh mode to be matching, unix doesn't
		1306	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1307
		1308	open my $fh2, $mode, $fh
		1309	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1310
		1311	# we assume CLOEXEC is already set by perl in all important cases
		1312
		1313	($fh2, $rw)
		1314	}
		1315
		1316	=head1 SIMPLIFIED AE API
		1317
		1318	Starting with version 5.0, AnyEvent officially supports a second, much
		1319	simpler, API that is designed to reduce the calling, typing and memory
		1320	overhead.
		1321
		1322	See the L<AE> manpage for details.
		1323
		1324	=cut
		1325
		1326	package AE;
		1327
		1328	our $VERSION = $AnyEvent::VERSION;
		1329
		1330	sub io($$$) {
		1331	AnyEvent->io (fh => $_[0], poll => $_[1] ? "w" : "r", cb => $_[2])
		1332	}
		1333
		1334	sub timer($$$) {
		1335	AnyEvent->timer (after => $_[0], interval => $_[1], cb => $_[2])
		1336	}
		1337
		1338	sub signal($$) {
		1339	AnyEvent->signal (signal => $_[0], cb => $_[1])
		1340	}
		1341
		1342	sub child($$) {
		1343	AnyEvent->child (pid => $_[0], cb => $_[1])
		1344	}
		1345
		1346	sub idle($) {
		1347	AnyEvent->idle (cb => $_[0])
		1348	}
		1349
		1350	sub cv(;&) {
		1351	AnyEvent->condvar (@_ ? (cb => $_[0]) : ())
		1352	}
		1353
		1354	sub now() {
		1355	AnyEvent->now
		1356	}
		1357
		1358	sub now_update() {
		1359	AnyEvent->now_update
		1360	}
		1361
		1362	sub time() {
		1363	AnyEvent->time
		1364	}
		1365
532	package AnyEvent::Base;	1366	package AnyEvent::Base;
533		1367
		1368	# default implementations for many methods
		1369
		1370	sub _time() {
		1371	# probe for availability of Time::HiRes
		1372	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1373	warn "AnyEvent: using Time::HiRes for sub-second timing accuracy.\n" if $VERBOSE >= 8;
		1374	*_time = \&Time::HiRes::time;
		1375	# if (eval "use POSIX (); (POSIX::times())...
		1376	} else {
		1377	warn "AnyEvent: using built-in time(), WARNING, no sub-second resolution!\n" if $VERBOSE;
		1378	*_time = sub { time }; # epic fail
		1379	}
		1380
		1381	&_time
		1382	}
		1383
		1384	sub time { _time }
		1385	sub now { _time }
		1386	sub now_update { }
		1387
534	# default implementation for ->condvar, ->wait, ->broadcast	1388	# default implementation for ->condvar
535		1389
536	sub condvar {	1390	sub condvar {
537	bless \my $flag, "AnyEvent::Base::CondVar"	1391	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
538	}
539
540	sub AnyEvent::Base::CondVar::broadcast {
541	${$_[0]}++;
542	}
543
544	sub AnyEvent::Base::CondVar::wait {
545	AnyEvent->one_event while !${$_[0]};
546	}	1392	}
547		1393
548	# default implementation for ->signal	1394	# default implementation for ->signal
549		1395
550	our %SIG_CB;	1396	our $HAVE_ASYNC_INTERRUPT;
		1397
		1398	sub _have_async_interrupt() {
		1399	$HAVE_ASYNC_INTERRUPT = 1*(!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT}
		1400	&& eval "use Async::Interrupt 1.02 (); 1")
		1401	unless defined $HAVE_ASYNC_INTERRUPT;
		1402
		1403	$HAVE_ASYNC_INTERRUPT
		1404	}
		1405
		1406	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1407	our (%SIG_ASY, %SIG_ASY_W);
		1408	our ($SIG_COUNT, $SIG_TW);
		1409
		1410	sub _signal_exec {
		1411	$HAVE_ASYNC_INTERRUPT
		1412	? $SIGPIPE_R->drain
		1413	: sysread $SIGPIPE_R, (my $dummy), 9;
		1414
		1415	while (%SIG_EV) {
		1416	for (keys %SIG_EV) {
		1417	delete $SIG_EV{$_};
		1418	$_->() for values %{ $SIG_CB{$_} || {} };
		1419	}
		1420	}
		1421	}
		1422
		1423	# install a dummy wakeup watcher to reduce signal catching latency
		1424	sub _sig_add() {
		1425	unless ($SIG_COUNT++) {
		1426	# try to align timer on a full-second boundary, if possible
		1427	my $NOW = AE::now;
		1428
		1429	$SIG_TW = AE::timer
		1430	$MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1431	$MAX_SIGNAL_LATENCY,
		1432	sub { } # just for the PERL_ASYNC_CHECK
		1433	;
		1434	}
		1435	}
		1436
		1437	sub _sig_del {
		1438	undef $SIG_TW
		1439	unless --$SIG_COUNT;
		1440	}
		1441
		1442	our $_sig_name_init; $_sig_name_init = sub {
		1443	eval q{ # poor man's autoloading
		1444	undef $_sig_name_init;
		1445
		1446	if (_have_async_interrupt) {
		1447	*sig2num = \&Async::Interrupt::sig2num;
		1448	*sig2name = \&Async::Interrupt::sig2name;
		1449	} else {
		1450	require Config;
		1451
		1452	my %signame2num;
		1453	@signame2num{ split ' ', $Config::Config{sig_name} }
		1454	= split ' ', $Config::Config{sig_num};
		1455
		1456	my @signum2name;
		1457	@signum2name[values %signame2num] = keys %signame2num;
		1458
		1459	*sig2num = sub($) {
		1460	$_[0] > 0 ? shift : $signame2num{+shift}
		1461	};
		1462	*sig2name = sub ($) {
		1463	$_[0] > 0 ? $signum2name[+shift] : shift
		1464	};
		1465	}
		1466	};
		1467	die if $@;
		1468	};
		1469
		1470	sub sig2num ($) { &$_sig_name_init; &sig2num }
		1471	sub sig2name($) { &$_sig_name_init; &sig2name }
551		1472
552	sub signal {	1473	sub signal {
		1474	eval q{ # poor man's autoloading {}
		1475	# probe for availability of Async::Interrupt
		1476	if (_have_async_interrupt) {
		1477	warn "AnyEvent: using Async::Interrupt for race-free signal handling.\n" if $VERBOSE >= 8;
		1478
		1479	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1480	$SIG_IO = AE::io $SIGPIPE_R->fileno, 0, \&_signal_exec;
		1481
		1482	} else {
		1483	warn "AnyEvent: using emulated perl signal handling with latency timer.\n" if $VERBOSE >= 8;
		1484
		1485	require Fcntl;
		1486
		1487	if (AnyEvent::WIN32) {
		1488	require AnyEvent::Util;
		1489
		1490	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1491	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R, 1) if $SIGPIPE_R;
		1492	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W, 1) if $SIGPIPE_W; # just in case
		1493	} else {
		1494	pipe $SIGPIPE_R, $SIGPIPE_W;
		1495	fcntl $SIGPIPE_R, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_R;
		1496	fcntl $SIGPIPE_W, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_W; # just in case
		1497
		1498	# not strictly required, as $^F is normally 2, but let's make sure...
		1499	fcntl $SIGPIPE_R, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1500	fcntl $SIGPIPE_W, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1501	}
		1502
		1503	$SIGPIPE_R
		1504	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1505
		1506	$SIG_IO = AE::io $SIGPIPE_R, 0, \&_signal_exec;
		1507	}
		1508
		1509	*signal = sub {
553	my (undef, %arg) = @_;	1510	my (undef, %arg) = @_;
554		1511
555	my $signal = uc $arg{signal}	1512	my $signal = uc $arg{signal}
556	or Carp::croak "required option 'signal' is missing";	1513	or Carp::croak "required option 'signal' is missing";
557		1514
		1515	if ($HAVE_ASYNC_INTERRUPT) {
		1516	# async::interrupt
		1517
		1518	$signal = sig2num $signal;
558	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1519	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1520
		1521	$SIG_ASY{$signal} ||= new Async::Interrupt
		1522	cb => sub { undef $SIG_EV{$signal} },
		1523	signal => $signal,
		1524	pipe => [$SIGPIPE_R->filenos],
		1525	pipe_autodrain => 0,
		1526	;
		1527
		1528	} else {
		1529	# pure perl
		1530
		1531	# AE::Util has been loaded in signal
		1532	$signal = sig2name $signal;
		1533	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1534
559	$SIG{$signal} ||= sub {	1535	$SIG{$signal} ||= sub {
560	$_->() for values %{ $SIG_CB{$signal} || {} };	1536	local $!;
		1537	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1538	undef $SIG_EV{$signal};
		1539	};
		1540
		1541	# can't do signal processing without introducing races in pure perl,
		1542	# so limit the signal latency.
		1543	_sig_add;
		1544	}
		1545
		1546	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1547	};
		1548
		1549	*AnyEvent::Base::signal::DESTROY = sub {
		1550	my ($signal, $cb) = @{$_[0]};
		1551
		1552	_sig_del;
		1553
		1554	delete $SIG_CB{$signal}{$cb};
		1555
		1556	$HAVE_ASYNC_INTERRUPT
		1557	? delete $SIG_ASY{$signal}
		1558	: # delete doesn't work with older perls - they then
		1559	# print weird messages, or just unconditionally exit
		1560	# instead of getting the default action.
		1561	undef $SIG{$signal}
		1562	unless keys %{ $SIG_CB{$signal} };
		1563	};
561	};	1564	};
562		1565	die if $@;
563	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1566	&signal
564	}
565
566	sub AnyEvent::Base::Signal::DESTROY {
567	my ($signal, $cb) = @{$_[0]};
568
569	delete $SIG_CB{$signal}{$cb};
570
571	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };
572	}	1567	}
573		1568
574	# default implementation for ->child	1569	# default implementation for ->child
575		1570
576	our %PID_CB;	1571	our %PID_CB;
577	our $CHLD_W;	1572	our $CHLD_W;
578	our $CHLD_DELAY_W;	1573	our $CHLD_DELAY_W;
579	our $PID_IDLE;
580	our $WNOHANG;	1574	our $WNOHANG;
581		1575
582	sub _child_wait {	1576	sub _emit_childstatus($$) {
583	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1577	my (undef, $rpid, $rstatus) = @_;
		1578
		1579	$_->($rpid, $rstatus)
584	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1580	for values %{ $PID_CB{$rpid} || {} },
585	(values %{ $PID_CB{0} || {} });	1581	values %{ $PID_CB{0} || {} };
586	}
587
588	undef $PID_IDLE;
589	}	1582	}
590		1583
591	sub _sigchld {	1584	sub _sigchld {
592	# make sure we deliver these changes "synchronous" with the event loop.	1585	my $pid;
593	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {	1586
594	undef $CHLD_DELAY_W;	1587	AnyEvent->_emit_childstatus ($pid, $?)
595	&_child_wait;	1588	while ($pid = waitpid -1, $WNOHANG) > 0;
596	});
597	}	1589	}
598		1590
599	sub child {	1591	sub child {
600	my (undef, %arg) = @_;	1592	my (undef, %arg) = @_;
601		1593
602	defined (my $pid = $arg{pid} + 0)	1594	defined (my $pid = $arg{pid} + 0)
603	or Carp::croak "required option 'pid' is missing";	1595	or Carp::croak "required option 'pid' is missing";
604		1596
605	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1597	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
606		1598
607	unless ($WNOHANG) {	1599	# WNOHANG is almost cetrainly 1 everywhere
608	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;	1600	$WNOHANG ||= $^O =~ /^(?:openbsd|netbsd|linux|freebsd|cygwin|MSWin32)$/
609	}	1601	? 1
		1602	: eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
610		1603
611	unless ($CHLD_W) {	1604	unless ($CHLD_W) {
612	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1605	$CHLD_W = AE::signal CHLD => \&_sigchld;
613	# child could be a zombie already, so make at least one round	1606	# child could be a zombie already, so make at least one round
614	&_sigchld;	1607	&_sigchld;
615	}	1608	}
616		1609
617	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	1610	bless [$pid, $arg{cb}], "AnyEvent::Base::child"
618	}	1611	}
619		1612
620	sub AnyEvent::Base::Child::DESTROY {	1613	sub AnyEvent::Base::child::DESTROY {
621	my ($pid, $cb) = @{$_[0]};	1614	my ($pid, $cb) = @{$_[0]};
622		1615
623	delete $PID_CB{$pid}{$cb};	1616	delete $PID_CB{$pid}{$cb};
624	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1617	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
625		1618
626	undef $CHLD_W unless keys %PID_CB;	1619	undef $CHLD_W unless keys %PID_CB;
627	}	1620	}
		1621
		1622	# idle emulation is done by simply using a timer, regardless
		1623	# of whether the process is idle or not, and not letting
		1624	# the callback use more than 50% of the time.
		1625	sub idle {
		1626	my (undef, %arg) = @_;
		1627
		1628	my ($cb, $w, $rcb) = $arg{cb};
		1629
		1630	$rcb = sub {
		1631	if ($cb) {
		1632	$w = _time;
		1633	&$cb;
		1634	$w = _time - $w;
		1635
		1636	# never use more then 50% of the time for the idle watcher,
		1637	# within some limits
		1638	$w = 0.0001 if $w < 0.0001;
		1639	$w = 5 if $w > 5;
		1640
		1641	$w = AE::timer $w, 0, $rcb;
		1642	} else {
		1643	# clean up...
		1644	undef $w;
		1645	undef $rcb;
		1646	}
		1647	};
		1648
		1649	$w = AE::timer 0.05, 0, $rcb;
		1650
		1651	bless \\$cb, "AnyEvent::Base::idle"
		1652	}
		1653
		1654	sub AnyEvent::Base::idle::DESTROY {
		1655	undef $${$_[0]};
		1656	}
		1657
		1658	package AnyEvent::CondVar;
		1659
		1660	our @ISA = AnyEvent::CondVar::Base::;
		1661
		1662	package AnyEvent::CondVar::Base;
		1663
		1664	#use overload
		1665	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1666	# fallback => 1;
		1667
		1668	# save 300+ kilobytes by dirtily hardcoding overloading
		1669	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1670	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1671	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1672	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1673
		1674	our $WAITING;
		1675
		1676	sub _send {
		1677	# nop
		1678	}
		1679
		1680	sub send {
		1681	my $cv = shift;
		1682	$cv->{_ae_sent} = [@_];
		1683	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1684	$cv->_send;
		1685	}
		1686
		1687	sub croak {
		1688	$_[0]{_ae_croak} = $_[1];
		1689	$_[0]->send;
		1690	}
		1691
		1692	sub ready {
		1693	$_[0]{_ae_sent}
		1694	}
		1695
		1696	sub _wait {
		1697	$WAITING
		1698	and !$_[0]{_ae_sent}
		1699	and Carp::croak "AnyEvent::CondVar: recursive blocking wait detected";
		1700
		1701	local $WAITING = 1;
		1702	AnyEvent->one_event while !$_[0]{_ae_sent};
		1703	}
		1704
		1705	sub recv {
		1706	$_[0]->_wait;
		1707
		1708	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
		1709	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
		1710	}
		1711
		1712	sub cb {
		1713	my $cv = shift;
		1714
		1715	@_
		1716	and $cv->{_ae_cb} = shift
		1717	and $cv->{_ae_sent}
		1718	and (delete $cv->{_ae_cb})->($cv);
		1719
		1720	$cv->{_ae_cb}
		1721	}
		1722
		1723	sub begin {
		1724	++$_[0]{_ae_counter};
		1725	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
		1726	}
		1727
		1728	sub end {
		1729	return if --$_[0]{_ae_counter};
		1730	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		1731	}
		1732
		1733	# undocumented/compatibility with pre-3.4
		1734	*broadcast = \&send;
		1735	*wait = \&_wait;
		1736
		1737	=head1 ERROR AND EXCEPTION HANDLING
		1738
		1739	In general, AnyEvent does not do any error handling - it relies on the
		1740	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1741	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1742	checking of all AnyEvent methods, however, which is highly useful during
		1743	development.
		1744
		1745	As for exception handling (i.e. runtime errors and exceptions thrown while
		1746	executing a callback), this is not only highly event-loop specific, but
		1747	also not in any way wrapped by this module, as this is the job of the main
		1748	program.
		1749
		1750	The pure perl event loop simply re-throws the exception (usually
		1751	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1752	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1753	so on.
		1754
		1755	=head1 ENVIRONMENT VARIABLES
		1756
		1757	The following environment variables are used by this module or its
		1758	submodules.
		1759
		1760	Note that AnyEvent will remove I<all> environment variables starting with
		1761	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		1762	enabled.
		1763
		1764	=over 4
		1765
		1766	=item C<PERL_ANYEVENT_VERBOSE>
		1767
		1768	By default, AnyEvent will be completely silent except in fatal
		1769	conditions. You can set this environment variable to make AnyEvent more
		1770	talkative.
		1771
		1772	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1773	conditions, such as not being able to load the event model specified by
		1774	C<PERL_ANYEVENT_MODEL>.
		1775
		1776	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1777	model it chooses.
		1778
		1779	When set to C<8> or higher, then AnyEvent will report extra information on
		1780	which optional modules it loads and how it implements certain features.
		1781
		1782	=item C<PERL_ANYEVENT_STRICT>
		1783
		1784	AnyEvent does not do much argument checking by default, as thorough
		1785	argument checking is very costly. Setting this variable to a true value
		1786	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1787	check the arguments passed to most method calls. If it finds any problems,
		1788	it will croak.
		1789
		1790	In other words, enables "strict" mode.
		1791
		1792	Unlike C<use strict> (or it's modern cousin, C<< use L<common::sense>
		1793	>>, it is definitely recommended to keep it off in production. Keeping
		1794	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		1795	can be very useful, however.
		1796
		1797	=item C<PERL_ANYEVENT_MODEL>
		1798
		1799	This can be used to specify the event model to be used by AnyEvent, before
		1800	auto detection and -probing kicks in. It must be a string consisting
		1801	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1802	and the resulting module name is loaded and if the load was successful,
		1803	used as event model. If it fails to load AnyEvent will proceed with
		1804	auto detection and -probing.
		1805
		1806	This functionality might change in future versions.
		1807
		1808	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1809	could start your program like this:
		1810
		1811	PERL_ANYEVENT_MODEL=Perl perl ...
		1812
		1813	=item C<PERL_ANYEVENT_PROTOCOLS>
		1814
		1815	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1816	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1817	of auto probing).
		1818
		1819	Must be set to a comma-separated list of protocols or address families,
		1820	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1821	used, and preference will be given to protocols mentioned earlier in the
		1822	list.
		1823
		1824	This variable can effectively be used for denial-of-service attacks
		1825	against local programs (e.g. when setuid), although the impact is likely
		1826	small, as the program has to handle conenction and other failures anyways.
		1827
		1828	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1829	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1830	- only support IPv4, never try to resolve or contact IPv6
		1831	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1832	IPv6, but prefer IPv6 over IPv4.
		1833
		1834	=item C<PERL_ANYEVENT_EDNS0>
		1835
		1836	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1837	for DNS. This extension is generally useful to reduce DNS traffic, but
		1838	some (broken) firewalls drop such DNS packets, which is why it is off by
		1839	default.
		1840
		1841	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1842	EDNS0 in its DNS requests.
		1843
		1844	=item C<PERL_ANYEVENT_MAX_FORKS>
		1845
		1846	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1847	will create in parallel.
		1848
		1849	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		1850
		1851	The default value for the C<max_outstanding> parameter for the default DNS
		1852	resolver - this is the maximum number of parallel DNS requests that are
		1853	sent to the DNS server.
		1854
		1855	=item C<PERL_ANYEVENT_RESOLV_CONF>
		1856
		1857	The file to use instead of F</etc/resolv.conf> (or OS-specific
		1858	configuration) in the default resolver. When set to the empty string, no
		1859	default config will be used.
		1860
		1861	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		1862
		1863	When neither C<ca_file> nor C<ca_path> was specified during
		1864	L<AnyEvent::TLS> context creation, and either of these environment
		1865	variables exist, they will be used to specify CA certificate locations
		1866	instead of a system-dependent default.
		1867
		1868	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		1869
		1870	When these are set to C<1>, then the respective modules are not
		1871	loaded. Mostly good for testing AnyEvent itself.
		1872
		1873	=back
628		1874
629	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1875	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
630		1876
631	This is an advanced topic that you do not normally need to use AnyEvent in	1877	This is an advanced topic that you do not normally need to use AnyEvent in
632	a module. This section is only of use to event loop authors who want to	1878	a module. This section is only of use to event loop authors who want to
…		…
667	I<rxvt-unicode> also cheats a bit by not providing blocking access to	1913	I<rxvt-unicode> also cheats a bit by not providing blocking access to
668	condition variables: code blocking while waiting for a condition will	1914	condition variables: code blocking while waiting for a condition will
669	C<die>. This still works with most modules/usages, and blocking calls must	1915	C<die>. This still works with most modules/usages, and blocking calls must
670	not be done in an interactive application, so it makes sense.	1916	not be done in an interactive application, so it makes sense.
671		1917
672	=head1 ENVIRONMENT VARIABLES
673
674	The following environment variables are used by this module:
675
676	=over 4
677
678	=item C<PERL_ANYEVENT_VERBOSE>
679
680	By default, AnyEvent will be completely silent except in fatal
681	conditions. You can set this environment variable to make AnyEvent more
682	talkative.
683
684	When set to C<1> or higher, causes AnyEvent to warn about unexpected
685	conditions, such as not being able to load the event model specified by
686	C<PERL_ANYEVENT_MODEL>.
687
688	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
689	model it chooses.
690
691	=item C<PERL_ANYEVENT_MODEL>
692
693	This can be used to specify the event model to be used by AnyEvent, before
694	autodetection and -probing kicks in. It must be a string consisting
695	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
696	and the resulting module name is loaded and if the load was successful,
697	used as event model. If it fails to load AnyEvent will proceed with
698	autodetection and -probing.
699
700	This functionality might change in future versions.
701
702	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
703	could start your program like this:
704
705	PERL_ANYEVENT_MODEL=Perl perl ...
706
707	=back
708
709	=head1 EXAMPLE PROGRAM	1918	=head1 EXAMPLE PROGRAM
710		1919
711	The following program uses an IO watcher to read data from STDIN, a timer	1920	The following program uses an I/O watcher to read data from STDIN, a timer
712	to display a message once per second, and a condition variable to quit the	1921	to display a message once per second, and a condition variable to quit the
713	program when the user enters quit:	1922	program when the user enters quit:
714		1923
715	use AnyEvent;	1924	use AnyEvent;
716		1925
…		…
721	poll => 'r',	1930	poll => 'r',
722	cb => sub {	1931	cb => sub {
723	warn "io event <$_[0]>\n"; # will always output <r>	1932	warn "io event <$_[0]>\n"; # will always output <r>
724	chomp (my $input = <STDIN>); # read a line	1933	chomp (my $input = <STDIN>); # read a line
725	warn "read: $input\n"; # output what has been read	1934	warn "read: $input\n"; # output what has been read
726	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	1935	$cv->send if $input =~ /^q/i; # quit program if /^q/i
727	},	1936	},
728	);	1937	);
729		1938
730	my $time_watcher; # can only be used once
731
732	sub new_timer {
733	$timer = AnyEvent->timer (after => 1, cb => sub {	1939	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
734	warn "timeout\n"; # print 'timeout' about every second	1940	warn "timeout\n"; # print 'timeout' at most every second
735	&new_timer; # and restart the time
736	});	1941	});
737	}
738		1942
739	new_timer; # create first timer
740
741	$cv->wait; # wait until user enters /^q/i	1943	$cv->recv; # wait until user enters /^q/i
742		1944
743	=head1 REAL-WORLD EXAMPLE	1945	=head1 REAL-WORLD EXAMPLE
744		1946
745	Consider the L<Net::FCP> module. It features (among others) the following	1947	Consider the L<Net::FCP> module. It features (among others) the following
746	API calls, which are to freenet what HTTP GET requests are to http:	1948	API calls, which are to freenet what HTTP GET requests are to http:
…		…
796	syswrite $txn->{fh}, $txn->{request}	1998	syswrite $txn->{fh}, $txn->{request}
797	or die "connection or write error";	1999	or die "connection or write error";
798	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	2000	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
799		2001
800	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	2002	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
801	result and signals any possible waiters that the request ahs finished:	2003	result and signals any possible waiters that the request has finished:
802		2004
803	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	2005	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
804		2006
805	if (end-of-file or data complete) {	2007	if (end-of-file or data complete) {
806	$txn->{result} = $txn->{buf};	2008	$txn->{result} = $txn->{buf};
807	$txn->{finished}->broadcast;	2009	$txn->{finished}->send;
808	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	2010	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
809	}	2011	}
810		2012
811	The C<result> method, finally, just waits for the finished signal (if the	2013	The C<result> method, finally, just waits for the finished signal (if the
812	request was already finished, it doesn't wait, of course, and returns the	2014	request was already finished, it doesn't wait, of course, and returns the
813	data:	2015	data:
814		2016
815	$txn->{finished}->wait;	2017	$txn->{finished}->recv;
816	return $txn->{result};	2018	return $txn->{result};
817		2019
818	The actual code goes further and collects all errors (C<die>s, exceptions)	2020	The actual code goes further and collects all errors (C<die>s, exceptions)
819	that occured during request processing. The C<result> method detects	2021	that occurred during request processing. The C<result> method detects
820	whether an exception as thrown (it is stored inside the $txn object)	2022	whether an exception as thrown (it is stored inside the $txn object)
821	and just throws the exception, which means connection errors and other	2023	and just throws the exception, which means connection errors and other
822	problems get reported tot he code that tries to use the result, not in a	2024	problems get reported tot he code that tries to use the result, not in a
823	random callback.	2025	random callback.
824		2026
…		…
855		2057
856	my $quit = AnyEvent->condvar;	2058	my $quit = AnyEvent->condvar;
857		2059
858	$fcp->txn_client_get ($url)->cb (sub {	2060	$fcp->txn_client_get ($url)->cb (sub {
859	...	2061	...
860	$quit->broadcast;	2062	$quit->send;
861	});	2063	});
862		2064
863	$quit->wait;	2065	$quit->recv;
864		2066
865		2067
866	=head1 BENCHMARK	2068	=head1 BENCHMARKS
867		2069
868	To give you an idea of the performance and overheads that AnyEvent adds	2070	To give you an idea of the performance and overheads that AnyEvent adds
869	over the backends directly, here is a benchmark of various supported event	2071	over the event loops themselves and to give you an impression of the speed
870	models natively and with anyevent. The benchmark creates a lot of timers	2072	of various event loops I prepared some benchmarks.
		2073
		2074	=head2 BENCHMARKING ANYEVENT OVERHEAD
		2075
		2076	Here is a benchmark of various supported event models used natively and
		2077	through AnyEvent. The benchmark creates a lot of timers (with a zero
871	(with a zero timeout) and io watchers (watching STDOUT, a pty, to become	2078	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
872	writable, which it is), lets them fire exactly once and destroys them	2079	which it is), lets them fire exactly once and destroys them again.
873	again.
874		2080
875	Explanation of the fields:	2081	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
		2082	distribution. It uses the L<AE> interface, which makes a real difference
		2083	for the EV and Perl backends only.
876		2084
		2085	=head3 Explanation of the columns
		2086
877	I<watcher> is the number of event watchers created/destroyed. Sicne	2087	I<watcher> is the number of event watchers created/destroyed. Since
878	different event models have vastly different performance each backend was	2088	different event models feature vastly different performances, each event
879	handed a number of watchers so that overall runtime is acceptable and	2089	loop was given a number of watchers so that overall runtime is acceptable
880	similar to all backends (and keep them from crashing).	2090	and similar between tested event loop (and keep them from crashing): Glib
		2091	would probably take thousands of years if asked to process the same number
		2092	of watchers as EV in this benchmark.
881		2093
882	I<bytes> is the number of bytes (as measured by resident set size) used by	2094	I<bytes> is the number of bytes (as measured by the resident set size,
883	each watcher.	2095	RSS) consumed by each watcher. This method of measuring captures both C
		2096	and Perl-based overheads.
884		2097
885	I<create> is the time, in microseconds, to create a single watcher.	2098	I<create> is the time, in microseconds (millionths of seconds), that it
		2099	takes to create a single watcher. The callback is a closure shared between
		2100	all watchers, to avoid adding memory overhead. That means closure creation
		2101	and memory usage is not included in the figures.
886		2102
887	I<invoke> is the time, in microseconds, used to invoke a simple callback	2103	I<invoke> is the time, in microseconds, used to invoke a simple
888	that simply counts down.	2104	callback. The callback simply counts down a Perl variable and after it was
		2105	invoked "watcher" times, it would C<< ->send >> a condvar once to
		2106	signal the end of this phase.
889		2107
890	I<destroy> is the time, in microseconds, to destroy a single watcher.	2108	I<destroy> is the time, in microseconds, that it takes to destroy a single
		2109	watcher.
891		2110
		2111	=head3 Results
		2112
892	name watcher bytes create invoke destroy comment	2113	name watchers bytes create invoke destroy comment
893	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	2114	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
894	EV/Any 100000 610 3.52 0.91 0.75	2115	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
895	CoroEV/Any 100000 610 3.49 0.92 0.75 coroutines + Coro::Signal	2116	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
896	Perl/Any 10000 654 4.64 1.22 0.77 pure perl implementation	2117	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
897	Event/Event 10000 523 28.05 21.38 5.22 Event native interface	2118	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
898	Event/Any 10000 943 34.43 20.48 1.39	2119	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
		2120	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
		2121	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
899	Glib/Any 16000 1357 96.99 12.55 55.51 quadratic behaviour	2122	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
900	Tk/Any 2000 1855 27.01 66.61 14.03 SEGV with >> 2000 watchers	2123	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
901	POE/Select 2000 6343 94.69 807.65 562.69 POE::Loop::Select	2124	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
902	POE/Event 2000 6644 108.15 768.19 14.33 POE::Loop::Event	2125	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
903		2126
904	Discussion: The benchmark does I<not> bench scalability of the	2127	=head3 Discussion
		2128
		2129	The benchmark does I<not> measure scalability of the event loop very
905	backend. For example a select-based backend (such as the pureperl one) can	2130	well. For example, a select-based event loop (such as the pure perl one)
906	never compete with a backend using epoll. In this benchmark, only a single	2131	can never compete with an event loop that uses epoll when the number of
907	filehandle is used.	2132	file descriptors grows high. In this benchmark, all events become ready at
		2133	the same time, so select/poll-based implementations get an unnatural speed
		2134	boost.
908		2135
		2136	Also, note that the number of watchers usually has a nonlinear effect on
		2137	overall speed, that is, creating twice as many watchers doesn't take twice
		2138	the time - usually it takes longer. This puts event loops tested with a
		2139	higher number of watchers at a disadvantage.
		2140
		2141	To put the range of results into perspective, consider that on the
		2142	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		2143	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		2144	cycles with POE.
		2145
909	EV is the sole leader regarding speed and memory use, which are both	2146	C<EV> is the sole leader regarding speed and memory use, which are both
910	maximal/minimal. Even when going through AnyEvent, there is only one event	2147	maximal/minimal, respectively. When using the L<AE> API there is zero
911	loop that uses less memory (the Event module natively), and no faster	2148	overhead (when going through the AnyEvent API create is about 5-6 times
912	event model.	2149	slower, with other times being equal, so still uses far less memory than
		2150	any other event loop and is still faster than Event natively).
913		2151
914	The pure perl implementation is hit in a few sweet spots (both the	2152	The pure perl implementation is hit in a few sweet spots (both the
915	zero timeout and the use of a single fd hit optimisations in the perl	2153	constant timeout and the use of a single fd hit optimisations in the perl
916	interpreter and the backend itself), but it shows that it adds very little	2154	interpreter and the backend itself). Nevertheless this shows that it
917	overhead in itself. Like any select-based backend it's performance becomes	2155	adds very little overhead in itself. Like any select-based backend its
918	really bad with lots of file descriptors.	2156	performance becomes really bad with lots of file descriptors (and few of
		2157	them active), of course, but this was not subject of this benchmark.
919		2158
920	The Event module has a relatively high setup and callback invocation cost,	2159	The C<Event> module has a relatively high setup and callback invocation
921	but overall scores on the third place.	2160	cost, but overall scores in on the third place.
922		2161
923	Glib has a little higher memory cost, a bit fster callback invocation and	2162	C<IO::Async> performs admirably well, about on par with C<Event>, even
924	has a similar speed as Event.	2163	when using its pure perl backend.
925		2164
		2165	C<Glib>'s memory usage is quite a bit higher, but it features a
		2166	faster callback invocation and overall ends up in the same class as
		2167	C<Event>. However, Glib scales extremely badly, doubling the number of
		2168	watchers increases the processing time by more than a factor of four,
		2169	making it completely unusable when using larger numbers of watchers
		2170	(note that only a single file descriptor was used in the benchmark, so
		2171	inefficiencies of C<poll> do not account for this).
		2172
926	The Tk backend works relatively well, the fact that it crashes with	2173	The C<Tk> adaptor works relatively well. The fact that it crashes with
927	more than 2000 watchers is a big setback, however, as correctness takes	2174	more than 2000 watchers is a big setback, however, as correctness takes
928	precedence over speed.	2175	precedence over speed. Nevertheless, its performance is surprising, as the
		2176	file descriptor is dup()ed for each watcher. This shows that the dup()
		2177	employed by some adaptors is not a big performance issue (it does incur a
		2178	hidden memory cost inside the kernel which is not reflected in the figures
		2179	above).
929		2180
930	POE, regardless of backend (wether it's pure perl select backend or the	2181	C<POE>, regardless of underlying event loop (whether using its pure perl
931	Event backend) shows abysmal performance and memory usage: Watchers use	2182	select-based backend or the Event module, the POE-EV backend couldn't
932	almost 30 times as much memory as EV watchers, and 10 times as much memory	2183	be tested because it wasn't working) shows abysmal performance and
933	as both Event or EV via AnyEvent.	2184	memory usage with AnyEvent: Watchers use almost 30 times as much memory
		2185	as EV watchers, and 10 times as much memory as Event (the high memory
		2186	requirements are caused by requiring a session for each watcher). Watcher
		2187	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		2188	implementation.
934		2189
		2190	The design of the POE adaptor class in AnyEvent can not really account
		2191	for the performance issues, though, as session creation overhead is
		2192	small compared to execution of the state machine, which is coded pretty
		2193	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		2194	using multiple sessions is not a good approach, especially regarding
		2195	memory usage, even the author of POE could not come up with a faster
		2196	design).
		2197
		2198	=head3 Summary
		2199
		2200	=over 4
		2201
935	Summary: using EV through AnyEvent is faster than any other event	2202	=item * Using EV through AnyEvent is faster than any other event loop
936	loop. The overhead AnyEvent adds can be very small, and you should avoid	2203	(even when used without AnyEvent), but most event loops have acceptable
937	POE like the plague if you want performance or reasonable memory usage.	2204	performance with or without AnyEvent.
		2205
		2206	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
		2207	the actual event loop, only with extremely fast event loops such as EV
		2208	adds AnyEvent significant overhead.
		2209
		2210	=item * You should avoid POE like the plague if you want performance or
		2211	reasonable memory usage.
		2212
		2213	=back
		2214
		2215	=head2 BENCHMARKING THE LARGE SERVER CASE
		2216
		2217	This benchmark actually benchmarks the event loop itself. It works by
		2218	creating a number of "servers": each server consists of a socket pair, a
		2219	timeout watcher that gets reset on activity (but never fires), and an I/O
		2220	watcher waiting for input on one side of the socket. Each time the socket
		2221	watcher reads a byte it will write that byte to a random other "server".
		2222
		2223	The effect is that there will be a lot of I/O watchers, only part of which
		2224	are active at any one point (so there is a constant number of active
		2225	fds for each loop iteration, but which fds these are is random). The
		2226	timeout is reset each time something is read because that reflects how
		2227	most timeouts work (and puts extra pressure on the event loops).
		2228
		2229	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
		2230	(1%) are active. This mirrors the activity of large servers with many
		2231	connections, most of which are idle at any one point in time.
		2232
		2233	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		2234	distribution. It uses the L<AE> interface, which makes a real difference
		2235	for the EV and Perl backends only.
		2236
		2237	=head3 Explanation of the columns
		2238
		2239	I<sockets> is the number of sockets, and twice the number of "servers" (as
		2240	each server has a read and write socket end).
		2241
		2242	I<create> is the time it takes to create a socket pair (which is
		2243	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		2244
		2245	I<request>, the most important value, is the time it takes to handle a
		2246	single "request", that is, reading the token from the pipe and forwarding
		2247	it to another server. This includes deleting the old timeout and creating
		2248	a new one that moves the timeout into the future.
		2249
		2250	=head3 Results
		2251
		2252	name sockets create request
		2253	EV 20000 62.66 7.99
		2254	Perl 20000 68.32 32.64
		2255	IOAsync 20000 174.06 101.15 epoll
		2256	IOAsync 20000 174.67 610.84 poll
		2257	Event 20000 202.69 242.91
		2258	Glib 20000 557.01 1689.52
		2259	POE 20000 341.54 12086.32 uses POE::Loop::Event
		2260
		2261	=head3 Discussion
		2262
		2263	This benchmark I<does> measure scalability and overall performance of the
		2264	particular event loop.
		2265
		2266	EV is again fastest. Since it is using epoll on my system, the setup time
		2267	is relatively high, though.
		2268
		2269	Perl surprisingly comes second. It is much faster than the C-based event
		2270	loops Event and Glib.
		2271
		2272	IO::Async performs very well when using its epoll backend, and still quite
		2273	good compared to Glib when using its pure perl backend.
		2274
		2275	Event suffers from high setup time as well (look at its code and you will
		2276	understand why). Callback invocation also has a high overhead compared to
		2277	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		2278	uses select or poll in basically all documented configurations.
		2279
		2280	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		2281	clearly fails to perform with many filehandles or in busy servers.
		2282
		2283	POE is still completely out of the picture, taking over 1000 times as long
		2284	as EV, and over 100 times as long as the Perl implementation, even though
		2285	it uses a C-based event loop in this case.
		2286
		2287	=head3 Summary
		2288
		2289	=over 4
		2290
		2291	=item * The pure perl implementation performs extremely well.
		2292
		2293	=item * Avoid Glib or POE in large projects where performance matters.
		2294
		2295	=back
		2296
		2297	=head2 BENCHMARKING SMALL SERVERS
		2298
		2299	While event loops should scale (and select-based ones do not...) even to
		2300	large servers, most programs we (or I :) actually write have only a few
		2301	I/O watchers.
		2302
		2303	In this benchmark, I use the same benchmark program as in the large server
		2304	case, but it uses only eight "servers", of which three are active at any
		2305	one time. This should reflect performance for a small server relatively
		2306	well.
		2307
		2308	The columns are identical to the previous table.
		2309
		2310	=head3 Results
		2311
		2312	name sockets create request
		2313	EV 16 20.00 6.54
		2314	Perl 16 25.75 12.62
		2315	Event 16 81.27 35.86
		2316	Glib 16 32.63 15.48
		2317	POE 16 261.87 276.28 uses POE::Loop::Event
		2318
		2319	=head3 Discussion
		2320
		2321	The benchmark tries to test the performance of a typical small
		2322	server. While knowing how various event loops perform is interesting, keep
		2323	in mind that their overhead in this case is usually not as important, due
		2324	to the small absolute number of watchers (that is, you need efficiency and
		2325	speed most when you have lots of watchers, not when you only have a few of
		2326	them).
		2327
		2328	EV is again fastest.
		2329
		2330	Perl again comes second. It is noticeably faster than the C-based event
		2331	loops Event and Glib, although the difference is too small to really
		2332	matter.
		2333
		2334	POE also performs much better in this case, but is is still far behind the
		2335	others.
		2336
		2337	=head3 Summary
		2338
		2339	=over 4
		2340
		2341	=item * C-based event loops perform very well with small number of
		2342	watchers, as the management overhead dominates.
		2343
		2344	=back
		2345
		2346	=head2 THE IO::Lambda BENCHMARK
		2347
		2348	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2349	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2350	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2351	shouldn't come as a surprise to anybody). As such, the benchmark is
		2352	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2353	very optimal. But how would AnyEvent compare when used without the extra
		2354	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2355
		2356	The benchmark itself creates an echo-server, and then, for 500 times,
		2357	connects to the echo server, sends a line, waits for the reply, and then
		2358	creates the next connection. This is a rather bad benchmark, as it doesn't
		2359	test the efficiency of the framework or much non-blocking I/O, but it is a
		2360	benchmark nevertheless.
		2361
		2362	name runtime
		2363	Lambda/select 0.330 sec
		2364	+ optimized 0.122 sec
		2365	Lambda/AnyEvent 0.327 sec
		2366	+ optimized 0.138 sec
		2367	Raw sockets/select 0.077 sec
		2368	POE/select, components 0.662 sec
		2369	POE/select, raw sockets 0.226 sec
		2370	POE/select, optimized 0.404 sec
		2371
		2372	AnyEvent/select/nb 0.085 sec
		2373	AnyEvent/EV/nb 0.068 sec
		2374	+state machine 0.134 sec
		2375
		2376	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2377	benchmarks actually make blocking connects and use 100% blocking I/O,
		2378	defeating the purpose of an event-based solution. All of the newly
		2379	written AnyEvent benchmarks use 100% non-blocking connects (using
		2380	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2381	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2382	generally require a lot more bookkeeping and event handling than blocking
		2383	connects (which involve a single syscall only).
		2384
		2385	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2386	offers similar expressive power as POE and IO::Lambda, using conventional
		2387	Perl syntax. This means that both the echo server and the client are 100%
		2388	non-blocking, further placing it at a disadvantage.
		2389
		2390	As you can see, the AnyEvent + EV combination even beats the
		2391	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2392	backend easily beats IO::Lambda and POE.
		2393
		2394	And even the 100% non-blocking version written using the high-level (and
		2395	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda
		2396	higher level ("unoptimised") abstractions by a large margin, even though
		2397	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
		2398
		2399	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2400	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2401	part of the IO::Lambda distribution and were used without any changes.
		2402
		2403
		2404	=head1 SIGNALS
		2405
		2406	AnyEvent currently installs handlers for these signals:
		2407
		2408	=over 4
		2409
		2410	=item SIGCHLD
		2411
		2412	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2413	emulation for event loops that do not support them natively. Also, some
		2414	event loops install a similar handler.
		2415
		2416	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2417	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2418
		2419	=item SIGPIPE
		2420
		2421	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2422	when AnyEvent gets loaded.
		2423
		2424	The rationale for this is that AnyEvent users usually do not really depend
		2425	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2426	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2427	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2428	some random socket.
		2429
		2430	The rationale for installing a no-op handler as opposed to ignoring it is
		2431	that this way, the handler will be restored to defaults on exec.
		2432
		2433	Feel free to install your own handler, or reset it to defaults.
		2434
		2435	=back
		2436
		2437	=cut
		2438
		2439	undef $SIG{CHLD}
		2440	if $SIG{CHLD} eq 'IGNORE';
		2441
		2442	$SIG{PIPE} = sub { }
		2443	unless defined $SIG{PIPE};
		2444
		2445	=head1 RECOMMENDED/OPTIONAL MODULES
		2446
		2447	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2448	it's built-in modules) are required to use it.
		2449
		2450	That does not mean that AnyEvent won't take advantage of some additional
		2451	modules if they are installed.
		2452
		2453	This section epxlains which additional modules will be used, and how they
		2454	affect AnyEvent's operation.
		2455
		2456	=over 4
		2457
		2458	=item L<Async::Interrupt>
		2459
		2460	This slightly arcane module is used to implement fast signal handling: To
		2461	my knowledge, there is no way to do completely race-free and quick
		2462	signal handling in pure perl. To ensure that signals still get
		2463	delivered, AnyEvent will start an interval timer to wake up perl (and
		2464	catch the signals) with some delay (default is 10 seconds, look for
		2465	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2466
		2467	If this module is available, then it will be used to implement signal
		2468	catching, which means that signals will not be delayed, and the event loop
		2469	will not be interrupted regularly, which is more efficient (and good for
		2470	battery life on laptops).
		2471
		2472	This affects not just the pure-perl event loop, but also other event loops
		2473	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2474
		2475	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2476	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2477	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2478	does nothing for those backends.
		2479
		2480	=item L<EV>
		2481
		2482	This module isn't really "optional", as it is simply one of the backend
		2483	event loops that AnyEvent can use. However, it is simply the best event
		2484	loop available in terms of features, speed and stability: It supports
		2485	the AnyEvent API optimally, implements all the watcher types in XS, does
		2486	automatic timer adjustments even when no monotonic clock is available,
		2487	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2488	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2489	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2490
		2491	=item L<Guard>
		2492
		2493	The guard module, when used, will be used to implement
		2494	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2495	lot less memory), but otherwise doesn't affect guard operation much. It is
		2496	purely used for performance.
		2497
		2498	=item L<JSON> and L<JSON::XS>
		2499
		2500	One of these modules is required when you want to read or write JSON data
		2501	via L<AnyEvent::Handle>. It is also written in pure-perl, but can take
		2502	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2503
		2504	In fact, L<AnyEvent::Handle> will use L<JSON::XS> by default if it is
		2505	installed.
		2506
		2507	=item L<Net::SSLeay>
		2508
		2509	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2510	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2511	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2512
		2513	=item L<Time::HiRes>
		2514
		2515	This module is part of perl since release 5.008. It will be used when the
		2516	chosen event library does not come with a timing source on it's own. The
		2517	pure-perl event loop (L<AnyEvent::Impl::Perl>) will additionally use it to
		2518	try to use a monotonic clock for timing stability.
		2519
		2520	=back
938		2521
939		2522
940	=head1 FORK	2523	=head1 FORK
941		2524
942	Most event libraries are not fork-safe. The ones who are usually are	2525	Most event libraries are not fork-safe. The ones who are usually are
943	because they are so inefficient. Only L<EV> is fully fork-aware.	2526	because they rely on inefficient but fork-safe C<select> or C<poll>
		2527	calls. Only L<EV> is fully fork-aware.
944		2528
945	If you have to fork, you must either do so I<before> creating your first	2529	If you have to fork, you must either do so I<before> creating your first
946	watcher OR you must not use AnyEvent at all in the child.	2530	watcher OR you must not use AnyEvent at all in the child OR you must do
		2531	something completely out of the scope of AnyEvent.
947		2532
948		2533
949	=head1 SECURITY CONSIDERATIONS	2534	=head1 SECURITY CONSIDERATIONS
950		2535
951	AnyEvent can be forced to load any event model via	2536	AnyEvent can be forced to load any event model via
…		…
956	specified in the variable.	2541	specified in the variable.
957		2542
958	You can make AnyEvent completely ignore this variable by deleting it	2543	You can make AnyEvent completely ignore this variable by deleting it
959	before the first watcher gets created, e.g. with a C<BEGIN> block:	2544	before the first watcher gets created, e.g. with a C<BEGIN> block:
960		2545
961	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	2546	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
962		2547
963	use AnyEvent;	2548	use AnyEvent;
		2549
		2550	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		2551	be used to probe what backend is used and gain other information (which is
		2552	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2553	$ENV{PERL_ANYEVENT_STRICT}.
		2554
		2555	Note that AnyEvent will remove I<all> environment variables starting with
		2556	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2557	enabled.
		2558
		2559
		2560	=head1 BUGS
		2561
		2562	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2563	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2564	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2565	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2566	pronounced).
964		2567
965		2568
966	=head1 SEE ALSO	2569	=head1 SEE ALSO
967		2570
968	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	2571	Utility functions: L<AnyEvent::Util>.
969	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,	2572
		2573	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
970	L<Event::Lib>, L<Qt>, L<POE>.	2574	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
971		2575
972	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	2576	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
		2577	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
		2578	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
973	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,	2579	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>, L<Anyevent::Impl::Irssi>.
974	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,
975	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.
976		2580
		2581	Non-blocking file handles, sockets, TCP clients and
		2582	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
		2583
		2584	Asynchronous DNS: L<AnyEvent::DNS>.
		2585
		2586	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>,
		2587	L<Coro::Event>,
		2588
977	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	2589	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::XMPP>,
		2590	L<AnyEvent::HTTP>.
978		2591
979		2592
980	=head1 AUTHOR	2593	=head1 AUTHOR
981		2594
982	Marc Lehmann <schmorp@schmorp.de>	2595	Marc Lehmann <schmorp@schmorp.de>
983	http://home.schmorp.de/	2596	http://home.schmorp.de/
984		2597
985	=cut	2598	=cut
986		2599
987	1	2600	1
988		2601

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