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Revision 1.106 by root, Thu May 1 13:45:22 2008 UTC vs.
Revision 1.267 by root, Thu Jul 30 03:46:12 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 ->send	36	$w->recv; # enters "main loop" till $condvar gets ->send
21	$w->send; # 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		108
71	=head1 DESCRIPTION	109	=head1 DESCRIPTION
72		110
…		…
78	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>
79	module.	117	module.
80		118
81	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
82	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
83	following modules is already loaded: L<Coro::EV>, L<Coro::Event>, L<EV>,	121	following modules is already loaded: L<EV>,
84	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,	122	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,
85	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
86	to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl	124	to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl
87	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
88	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
…		…
102	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
103	use AnyEvent so their modules work together with others seamlessly...	141	use AnyEvent so their modules work together with others seamlessly...
104		142
105	The pure-perl implementation of AnyEvent is called	143	The pure-perl implementation of AnyEvent is called
106	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
107	explicitly.	145	explicitly and enjoy the high availability of that event loop :)
108		146
109	=head1 WATCHERS	147	=head1 WATCHERS
110		148
111	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
112	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
113	the callback to call, the filehandle to watch, etc.	151	the callback to call, the file handle to watch, etc.
114		152
115	These watchers are normal Perl objects with normal Perl lifetime. After	153	These watchers are normal Perl objects with normal Perl lifetime. After
116	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
117	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
118	is in control).	156	is in control).
119		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
120	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
121	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
122	to it).	166	to it).
123		167
124	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.
…		…
126	Many watchers either are used with "recursion" (repeating timers for	170	Many watchers either are used with "recursion" (repeating timers for
127	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.
128		172
129	An any way to achieve that is this pattern:	173	An any way to achieve that is this pattern:
130		174
131	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	175	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
132	# you can use $w here, for example to undef it	176	# you can use $w here, for example to undef it
133	undef $w;	177	undef $w;
134	});	178	});
135		179
136	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,
137	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
138	declared.	182	declared.
139		183
140	=head2 I/O WATCHERS	184	=head2 I/O WATCHERS
141		185
		186	$w = AnyEvent->io (
		187	fh => <filehandle_or_fileno>,
		188	poll => <"r" or "w">,
		189	cb => <callback>,
		190	);
		191
142	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
143	with the following mandatory key-value pairs as arguments:	193	with the following mandatory key-value pairs as arguments:
144		194
145	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch	195	C<fh> is the Perl I<file handle> (or a naked file descriptor) to watch
		196	for events (AnyEvent might or might not keep a reference to this file
		197	handle). Note that only file handles pointing to things for which
		198	non-blocking operation makes sense are allowed. This includes sockets,
		199	most character devices, pipes, fifos and so on, but not for example files
		200	or block devices.
		201
146	for events. C<poll> must be a string that is either C<r> or C<w>,	202	C<poll> must be a string that is either C<r> or C<w>, which creates a
147	which creates a watcher waiting for "r"eadable or "w"ritable events,	203	watcher waiting for "r"eadable or "w"ritable events, respectively.
		204
148	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.
149	becomes ready.
150		206
151	Although the callback might get passed parameters, their value and	207	Although the callback might get passed parameters, their value and
152	presence is undefined and you cannot rely on them. Portable AnyEvent	208	presence is undefined and you cannot rely on them. Portable AnyEvent
153	callbacks cannot use arguments passed to I/O watcher callbacks.	209	callbacks cannot use arguments passed to I/O watcher callbacks.
154		210
…		…
158		214
159	Some event loops issue spurious readyness notifications, so you should	215	Some event loops issue spurious readyness notifications, so you should
160	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
161	handles.	217	handles.
162		218
163	Example:
164
165	# 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
166	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	222	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
167	chomp (my $input = <STDIN>);	223	chomp (my $input = <STDIN>);
168	warn "read: $input\n";	224	warn "read: $input\n";
169	undef $w;	225	undef $w;
170	});	226	});
171		227
172	=head2 TIME WATCHERS	228	=head2 TIME WATCHERS
173		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
174	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 >>
175	method with the following mandatory arguments:	239	method with the following mandatory arguments:
176		240
177	C<after> specifies after how many seconds (fractional values are	241	C<after> specifies after how many seconds (fractional values are
178	supported) the callback should be invoked. C<cb> is the callback to invoke	242	supported) the callback should be invoked. C<cb> is the callback to invoke
…		…
180		244
181	Although the callback might get passed parameters, their value and	245	Although the callback might get passed parameters, their value and
182	presence is undefined and you cannot rely on them. Portable AnyEvent	246	presence is undefined and you cannot rely on them. Portable AnyEvent
183	callbacks cannot use arguments passed to time watcher callbacks.	247	callbacks cannot use arguments passed to time watcher callbacks.
184		248
185	The timer callback will be invoked at most once: if you want a repeating	249	The callback will normally be invoked once only. If you specify another
186	timer you have to create a new watcher (this is a limitation by both Tk	250	parameter, C<interval>, as a strictly positive number (> 0), then the
187	and Glib).	251	callback will be invoked regularly at that interval (in fractional
		252	seconds) after the first invocation. If C<interval> is specified with a
		253	false value, then it is treated as if it were missing.
188		254
189	Example:	255	The callback will be rescheduled before invoking the callback, but no
		256	attempt is done to avoid timer drift in most backends, so the interval is
		257	only approximate.
190		258
191	# fire an event after 7.7 seconds	259	Example: fire an event after 7.7 seconds.
		260
192	my $w = AnyEvent->timer (after => 7.7, cb => sub {	261	my $w = AnyEvent->timer (after => 7.7, cb => sub {
193	warn "timeout\n";	262	warn "timeout\n";
194	});	263	});
195		264
196	# to cancel the timer:	265	# to cancel the timer:
197	undef $w;	266	undef $w;
198		267
199	Example 2:
200
201	# 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.
202	my $w;
203		269
204	my $cb = sub {
205	# cancel the old timer while creating a new one
206	$w = AnyEvent->timer (after => 1, cb => $cb);	270	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		271	warn "timeout\n";
207	};	272	};
208
209	# start the "loop" by creating the first watcher
210	$w = AnyEvent->timer (after => 0.5, cb => $cb);
211		273
212	=head3 TIMING ISSUES	274	=head3 TIMING ISSUES
213		275
214	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
215	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
…		…
227	timers.	289	timers.
228		290
229	AnyEvent always prefers relative timers, if available, matching the	291	AnyEvent always prefers relative timers, if available, matching the
230	AnyEvent API.	292	AnyEvent API.
231		293
		294	AnyEvent has two additional methods that return the "current time":
		295
		296	=over 4
		297
		298	=item AnyEvent->time
		299
		300	This returns the "current wallclock time" as a fractional number of
		301	seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
		302	return, and the result is guaranteed to be compatible with those).
		303
		304	It progresses independently of any event loop processing, i.e. each call
		305	will check the system clock, which usually gets updated frequently.
		306
		307	=item AnyEvent->now
		308
		309	This also returns the "current wallclock time", but unlike C<time>, above,
		310	this value might change only once per event loop iteration, depending on
		311	the event loop (most return the same time as C<time>, above). This is the
		312	time that AnyEvent's timers get scheduled against.
		313
		314	I<In almost all cases (in all cases if you don't care), this is the
		315	function to call when you want to know the current time.>
		316
		317	This function is also often faster then C<< AnyEvent->time >>, and
		318	thus the preferred method if you want some timestamp (for example,
		319	L<AnyEvent::Handle> uses this to update it's activity timeouts).
		320
		321	The rest of this section is only of relevance if you try to be very exact
		322	with your timing, you can skip it without bad conscience.
		323
		324	For a practical example of when these times differ, consider L<Event::Lib>
		325	and L<EV> and the following set-up:
		326
		327	The event loop is running and has just invoked one of your callback at
		328	time=500 (assume no other callbacks delay processing). In your callback,
		329	you wait a second by executing C<sleep 1> (blocking the process for a
		330	second) and then (at time=501) you create a relative timer that fires
		331	after three seconds.
		332
		333	With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
		334	both return C<501>, because that is the current time, and the timer will
		335	be scheduled to fire at time=504 (C<501> + C<3>).
		336
		337	With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
		338	time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
		339	last event processing phase started. With L<EV>, your timer gets scheduled
		340	to run at time=503 (C<500> + C<3>).
		341
		342	In one sense, L<Event::Lib> is more exact, as it uses the current time
		343	regardless of any delays introduced by event processing. However, most
		344	callbacks do not expect large delays in processing, so this causes a
		345	higher drift (and a lot more system calls to get the current time).
		346
		347	In another sense, L<EV> is more exact, as your timer will be scheduled at
		348	the same time, regardless of how long event processing actually took.
		349
		350	In either case, if you care (and in most cases, you don't), then you
		351	can get whatever behaviour you want with any event loop, by taking the
		352	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
		353	account.
		354
		355	=item AnyEvent->now_update
		356
		357	Some event loops (such as L<EV> or L<AnyEvent::Impl::Perl>) cache
		358	the current time for each loop iteration (see the discussion of L<<
		359	AnyEvent->now >>, above).
		360
		361	When a callback runs for a long time (or when the process sleeps), then
		362	this "current" time will differ substantially from the real time, which
		363	might affect timers and time-outs.
		364
		365	When this is the case, you can call this method, which will update the
		366	event loop's idea of "current time".
		367
		368	Note that updating the time I<might> cause some events to be handled.
		369
		370	=back
		371
232	=head2 SIGNAL WATCHERS	372	=head2 SIGNAL WATCHERS
233		373
		374	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		375
234	You can watch for signals using a signal watcher, C<signal> is the signal	376	You can watch for signals using a signal watcher, C<signal> is the signal
235	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to	377	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
236	be invoked whenever a signal occurs.	378	callback to be invoked whenever a signal occurs.
237		379
238	Although the callback might get passed parameters, their value and	380	Although the callback might get passed parameters, their value and
239	presence is undefined and you cannot rely on them. Portable AnyEvent	381	presence is undefined and you cannot rely on them. Portable AnyEvent
240	callbacks cannot use arguments passed to signal watcher callbacks.	382	callbacks cannot use arguments passed to signal watcher callbacks.
241		383
242	Multiple signal occurances can be clumped together into one callback	384	Multiple signal occurrences can be clumped together into one callback
243	invocation, and callback invocation will be synchronous. synchronous means	385	invocation, and callback invocation will be synchronous. Synchronous means
244	that it might take a while until the signal gets handled by the process,	386	that it might take a while until the signal gets handled by the process,
245	but it is guarenteed not to interrupt any other callbacks.	387	but it is guaranteed not to interrupt any other callbacks.
246		388
247	The main advantage of using these watchers is that you can share a signal	389	The main advantage of using these watchers is that you can share a signal
248	between multiple watchers.	390	between multiple watchers, and AnyEvent will ensure that signals will not
		391	interrupt your program at bad times.
249		392
250	This watcher might use C<%SIG>, so programs overwriting those signals	393	This watcher might use C<%SIG> (depending on the event loop used),
251	directly will likely not work correctly.	394	so programs overwriting those signals directly will likely not work
		395	correctly.
252		396
253	Example: exit on SIGINT	397	Example: exit on SIGINT
254		398
255	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	399	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
256		400
		401	=head3 Signal Races, Delays and Workarounds
		402
		403	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		404	callbacks to signals in a generic way, which is a pity, as you cannot
		405	do race-free signal handling in perl, requiring C libraries for
		406	this. AnyEvent will try to do it's best, which means in some cases,
		407	signals will be delayed. The maximum time a signal might be delayed is
		408	specified in C<$AnyEvent::MAX_SIGNAL_LATENCY> (default: 10 seconds). This
		409	variable can be changed only before the first signal watcher is created,
		410	and should be left alone otherwise. This variable determines how often
		411	AnyEvent polls for signals (in case a wake-up was missed). Higher values
		412	will cause fewer spurious wake-ups, which is better for power and CPU
		413	saving.
		414
		415	All these problems can be avoided by installing the optional
		416	L<Async::Interrupt> module, which works with most event loops. It will not
		417	work with inherently broken event loops such as L<Event> or L<Event::Lib>
		418	(and not with L<POE> currently, as POE does it's own workaround with
		419	one-second latency). For those, you just have to suffer the delays.
		420
257	=head2 CHILD PROCESS WATCHERS	421	=head2 CHILD PROCESS WATCHERS
258		422
		423	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		424
259	You can also watch on a child process exit and catch its exit status.	425	You can also watch on a child process exit and catch its exit status.
260		426
261	The child process is specified by the C<pid> argument (if set to C<0>, it	427	The child process is specified by the C<pid> argument (one some backends,
262	watches for any child process exit). The watcher will trigger as often	428	using C<0> watches for any child process exit, on others this will
263	as status change for the child are received. This works by installing a	429	croak). The watcher will be triggered only when the child process has
264	signal handler for C<SIGCHLD>. The callback will be called with the pid	430	finished and an exit status is available, not on any trace events
265	and exit status (as returned by waitpid), so unlike other watcher types,	431	(stopped/continued).
266	you I<can> rely on child watcher callback arguments.	432
		433	The callback will be called with the pid and exit status (as returned by
		434	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		435	callback arguments.
		436
		437	This watcher type works by installing a signal handler for C<SIGCHLD>,
		438	and since it cannot be shared, nothing else should use SIGCHLD or reap
		439	random child processes (waiting for specific child processes, e.g. inside
		440	C<system>, is just fine).
267		441
268	There is a slight catch to child watchers, however: you usually start them	442	There is a slight catch to child watchers, however: you usually start them
269	I<after> the child process was created, and this means the process could	443	I<after> the child process was created, and this means the process could
270	have exited already (and no SIGCHLD will be sent anymore).	444	have exited already (and no SIGCHLD will be sent anymore).
271		445
272	Not all event models handle this correctly (POE doesn't), but even for	446	Not all event models handle this correctly (neither POE nor IO::Async do,
		447	see their AnyEvent::Impl manpages for details), but even for event models
273	event models that I<do> handle this correctly, they usually need to be	448	that I<do> handle this correctly, they usually need to be loaded before
274	loaded before the process exits (i.e. before you fork in the first place).	449	the process exits (i.e. before you fork in the first place). AnyEvent's
		450	pure perl event loop handles all cases correctly regardless of when you
		451	start the watcher.
275		452
276	This means you cannot create a child watcher as the very first thing in an	453	This means you cannot create a child watcher as the very first
277	AnyEvent program, you I<have> to create at least one watcher before you	454	thing in an AnyEvent program, you I<have> to create at least one
278	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).	455	watcher before you C<fork> the child (alternatively, you can call
		456	C<AnyEvent::detect>).
		457
		458	As most event loops do not support waiting for child events, they will be
		459	emulated by AnyEvent in most cases, in which the latency and race problems
		460	mentioned in the description of signal watchers apply.
279		461
280	Example: fork a process and wait for it	462	Example: fork a process and wait for it
281		463
282	my $done = AnyEvent->condvar;	464	my $done = AnyEvent->condvar;
283		465
284	AnyEvent::detect; # force event module to be initialised
285
286	my $pid = fork or exit 5;	466	my $pid = fork or exit 5;
287		467
288	my $w = AnyEvent->child (	468	my $w = AnyEvent->child (
289	pid => $pid,	469	pid => $pid,
290	cb => sub {	470	cb => sub {
291	my ($pid, $status) = @_;	471	my ($pid, $status) = @_;
292	warn "pid $pid exited with status $status";	472	warn "pid $pid exited with status $status";
293	$done->send;	473	$done->send;
294	},	474	},
295	);	475	);
296		476
297	# do something else, then wait for process exit	477	# do something else, then wait for process exit
298	$done->wait;	478	$done->recv;
		479
		480	=head2 IDLE WATCHERS
		481
		482	$w = AnyEvent->idle (cb => <callback>);
		483
		484	Sometimes there is a need to do something, but it is not so important
		485	to do it instantly, but only when there is nothing better to do. This
		486	"nothing better to do" is usually defined to be "no other events need
		487	attention by the event loop".
		488
		489	Idle watchers ideally get invoked when the event loop has nothing
		490	better to do, just before it would block the process to wait for new
		491	events. Instead of blocking, the idle watcher is invoked.
		492
		493	Most event loops unfortunately do not really support idle watchers (only
		494	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		495	will simply call the callback "from time to time".
		496
		497	Example: read lines from STDIN, but only process them when the
		498	program is otherwise idle:
		499
		500	my @lines; # read data
		501	my $idle_w;
		502	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		503	push @lines, scalar <STDIN>;
		504
		505	# start an idle watcher, if not already done
		506	$idle_w ||= AnyEvent->idle (cb => sub {
		507	# handle only one line, when there are lines left
		508	if (my $line = shift @lines) {
		509	print "handled when idle: $line";
		510	} else {
		511	# otherwise disable the idle watcher again
		512	undef $idle_w;
		513	}
		514	});
		515	});
299		516
300	=head2 CONDITION VARIABLES	517	=head2 CONDITION VARIABLES
		518
		519	$cv = AnyEvent->condvar;
		520
		521	$cv->send (<list>);
		522	my @res = $cv->recv;
301		523
302	If you are familiar with some event loops you will know that all of them	524	If you are familiar with some event loops you will know that all of them
303	require you to run some blocking "loop", "run" or similar function that	525	require you to run some blocking "loop", "run" or similar function that
304	will actively watch for new events and call your callbacks.	526	will actively watch for new events and call your callbacks.
305		527
306	AnyEvent is different, it expects somebody else to run the event loop and	528	AnyEvent is slightly different: it expects somebody else to run the event
307	will only block when necessary (usually when told by the user).	529	loop and will only block when necessary (usually when told by the user).
308		530
309	The instrument to do that is called a "condition variable", so called	531	The instrument to do that is called a "condition variable", so called
310	because they represent a condition that must become true.	532	because they represent a condition that must become true.
		533
		534	Now is probably a good time to look at the examples further below.
311		535
312	Condition variables can be created by calling the C<< AnyEvent->condvar	536	Condition variables can be created by calling the C<< AnyEvent->condvar
313	>> method, usually without arguments. The only argument pair allowed is	537	>> method, usually without arguments. The only argument pair allowed is
314	C<cb>, which specifies a callback to be called when the condition variable	538	C<cb>, which specifies a callback to be called when the condition variable
315	becomes true.	539	becomes true, with the condition variable as the first argument (but not
		540	the results).
316		541
317	After creation, the conditon variable is "false" until it becomes "true"	542	After creation, the condition variable is "false" until it becomes "true"
318	by calling the C<send> method.	543	by calling the C<send> method (or calling the condition variable as if it
		544	were a callback, read about the caveats in the description for the C<<
		545	->send >> method).
319		546
320	Condition variables are similar to callbacks, except that you can	547	Condition variables are similar to callbacks, except that you can
321	optionally wait for them. They can also be called merge points - points	548	optionally wait for them. They can also be called merge points - points
322	in time where multiple outstandign events have been processed. And yet	549	in time where multiple outstanding events have been processed. And yet
323	another way to call them is transations - each condition variable can be	550	another way to call them is transactions - each condition variable can be
324	used to represent a transaction, which finishes at some point and delivers	551	used to represent a transaction, which finishes at some point and delivers
325	a result.	552	a result. And yet some people know them as "futures" - a promise to
		553	compute/deliver something that you can wait for.
326		554
327	Condition variables are very useful to signal that something has finished,	555	Condition variables are very useful to signal that something has finished,
328	for example, if you write a module that does asynchronous http requests,	556	for example, if you write a module that does asynchronous http requests,
329	then a condition variable would be the ideal candidate to signal the	557	then a condition variable would be the ideal candidate to signal the
330	availability of results. The user can either act when the callback is	558	availability of results. The user can either act when the callback is
331	called or can synchronously C<< ->wait >> for the results.	559	called or can synchronously C<< ->recv >> for the results.
332		560
333	You can also use them to simulate traditional event loops - for example,	561	You can also use them to simulate traditional event loops - for example,
334	you can block your main program until an event occurs - for example, you	562	you can block your main program until an event occurs - for example, you
335	could C<< ->wait >> in your main program until the user clicks the Quit	563	could C<< ->recv >> in your main program until the user clicks the Quit
336	button of your app, which would C<< ->send >> the "quit" event.	564	button of your app, which would C<< ->send >> the "quit" event.
337		565
338	Note that condition variables recurse into the event loop - if you have	566	Note that condition variables recurse into the event loop - if you have
339	two pieces of code that call C<< ->wait >> in a round-robbin fashion, you	567	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
340	lose. Therefore, condition variables are good to export to your caller, but	568	lose. Therefore, condition variables are good to export to your caller, but
341	you should avoid making a blocking wait yourself, at least in callbacks,	569	you should avoid making a blocking wait yourself, at least in callbacks,
342	as this asks for trouble.	570	as this asks for trouble.
343		571
344	Condition variables are represented by hash refs in perl, and the keys	572	Condition variables are represented by hash refs in perl, and the keys
…		…
349		577
350	There are two "sides" to a condition variable - the "producer side" which	578	There are two "sides" to a condition variable - the "producer side" which
351	eventually calls C<< -> send >>, and the "consumer side", which waits	579	eventually calls C<< -> send >>, and the "consumer side", which waits
352	for the send to occur.	580	for the send to occur.
353		581
354	Example:	582	Example: wait for a timer.
355		583
356	# wait till the result is ready	584	# wait till the result is ready
357	my $result_ready = AnyEvent->condvar;	585	my $result_ready = AnyEvent->condvar;
358		586
359	# do something such as adding a timer	587	# do something such as adding a timer
…		…
364	after => 1,	592	after => 1,
365	cb => sub { $result_ready->send },	593	cb => sub { $result_ready->send },
366	);	594	);
367		595
368	# this "blocks" (while handling events) till the callback	596	# this "blocks" (while handling events) till the callback
369	# calls send	597	# calls -<send
370	$result_ready->wait;	598	$result_ready->recv;
		599
		600	Example: wait for a timer, but take advantage of the fact that condition
		601	variables are also callable directly.
		602
		603	my $done = AnyEvent->condvar;
		604	my $delay = AnyEvent->timer (after => 5, cb => $done);
		605	$done->recv;
		606
		607	Example: Imagine an API that returns a condvar and doesn't support
		608	callbacks. This is how you make a synchronous call, for example from
		609	the main program:
		610
		611	use AnyEvent::CouchDB;
		612
		613	...
		614
		615	my @info = $couchdb->info->recv;
		616
		617	And this is how you would just set a callback to be called whenever the
		618	results are available:
		619
		620	$couchdb->info->cb (sub {
		621	my @info = $_[0]->recv;
		622	});
371		623
372	=head3 METHODS FOR PRODUCERS	624	=head3 METHODS FOR PRODUCERS
373		625
374	These methods should only be used by the producing side, i.e. the	626	These methods should only be used by the producing side, i.e. the
375	code/module that eventually sends the signal. Note that it is also	627	code/module that eventually sends the signal. Note that it is also
…		…
378		630
379	=over 4	631	=over 4
380		632
381	=item $cv->send (...)	633	=item $cv->send (...)
382		634
383	Flag the condition as ready - a running C<< ->wait >> and all further	635	Flag the condition as ready - a running C<< ->recv >> and all further
384	calls to C<wait> will (eventually) return after this method has been	636	calls to C<recv> will (eventually) return after this method has been
385	called. If nobody is waiting the send will be remembered.	637	called. If nobody is waiting the send will be remembered.
386		638
387	If a callback has been set on the condition variable, it is called	639	If a callback has been set on the condition variable, it is called
388	immediately from within send.	640	immediately from within send.
389		641
390	Any arguments passed to the C<send> call will be returned by all	642	Any arguments passed to the C<send> call will be returned by all
391	future C<< ->wait >> calls.	643	future C<< ->recv >> calls.
		644
		645	Condition variables are overloaded so one can call them directly (as if
		646	they were a code reference). Calling them directly is the same as calling
		647	C<send>.
392		648
393	=item $cv->croak ($error)	649	=item $cv->croak ($error)
394		650
395	Similar to send, but causes all call's wait C<< ->wait >> to invoke	651	Similar to send, but causes all call's to C<< ->recv >> to invoke
396	C<Carp::croak> with the given error message/object/scalar.	652	C<Carp::croak> with the given error message/object/scalar.
397		653
398	This can be used to signal any errors to the condition variable	654	This can be used to signal any errors to the condition variable
399	user/consumer.	655	user/consumer. Doing it this way instead of calling C<croak> directly
		656	delays the error detetcion, but has the overwhelmign advantage that it
		657	diagnoses the error at the place where the result is expected, and not
		658	deep in some event clalback without connection to the actual code causing
		659	the problem.
400		660
401	=item $cv->begin ([group callback])	661	=item $cv->begin ([group callback])
402		662
403	=item $cv->end	663	=item $cv->end
404		664
…		…
410	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end	670	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
411	>>, the (last) callback passed to C<begin> will be executed. That callback	671	>>, the (last) callback passed to C<begin> will be executed. That callback
412	is I<supposed> to call C<< ->send >>, but that is not required. If no	672	is I<supposed> to call C<< ->send >>, but that is not required. If no
413	callback was set, C<send> will be called without any arguments.	673	callback was set, C<send> will be called without any arguments.
414		674
415	Let's clarify this with the ping example:	675	You can think of C<< $cv->send >> giving you an OR condition (one call
		676	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		677	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		678
		679	Let's start with a simple example: you have two I/O watchers (for example,
		680	STDOUT and STDERR for a program), and you want to wait for both streams to
		681	close before activating a condvar:
		682
		683	my $cv = AnyEvent->condvar;
		684
		685	$cv->begin; # first watcher
		686	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		687	defined sysread $fh1, my $buf, 4096
		688	or $cv->end;
		689	});
		690
		691	$cv->begin; # second watcher
		692	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		693	defined sysread $fh2, my $buf, 4096
		694	or $cv->end;
		695	});
		696
		697	$cv->recv;
		698
		699	This works because for every event source (EOF on file handle), there is
		700	one call to C<begin>, so the condvar waits for all calls to C<end> before
		701	sending.
		702
		703	The ping example mentioned above is slightly more complicated, as the
		704	there are results to be passwd back, and the number of tasks that are
		705	begung can potentially be zero:
416		706
417	my $cv = AnyEvent->condvar;	707	my $cv = AnyEvent->condvar;
418		708
419	my %result;	709	my %result;
420	$cv->begin (sub { $cv->send (\%result) });	710	$cv->begin (sub { $cv->send (\%result) });
…		…
440	loop, which serves two important purposes: first, it sets the callback	730	loop, which serves two important purposes: first, it sets the callback
441	to be called once the counter reaches C<0>, and second, it ensures that	731	to be called once the counter reaches C<0>, and second, it ensures that
442	C<send> is called even when C<no> hosts are being pinged (the loop	732	C<send> is called even when C<no> hosts are being pinged (the loop
443	doesn't execute once).	733	doesn't execute once).
444		734
445	This is the general pattern when you "fan out" into multiple subrequests:	735	This is the general pattern when you "fan out" into multiple (but
446	use an outer C<begin>/C<end> pair to set the callback and ensure C<end>	736	potentially none) subrequests: use an outer C<begin>/C<end> pair to set
447	is called at least once, and then, for each subrequest you start, call	737	the callback and ensure C<end> is called at least once, and then, for each
448	C<begin> and for eahc subrequest you finish, call C<end>.	738	subrequest you start, call C<begin> and for each subrequest you finish,
		739	call C<end>.
449		740
450	=back	741	=back
451		742
452	=head3 METHODS FOR CONSUMERS	743	=head3 METHODS FOR CONSUMERS
453		744
454	These methods should only be used by the consuming side, i.e. the	745	These methods should only be used by the consuming side, i.e. the
455	code awaits the condition.	746	code awaits the condition.
456		747
457	=over 4	748	=over 4
458		749
459	=item $cv->wait	750	=item $cv->recv
460		751
461	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak	752	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
462	>> methods have been called on c<$cv>, while servicing other watchers	753	>> methods have been called on c<$cv>, while servicing other watchers
463	normally.	754	normally.
464		755
…		…
469	function will call C<croak>.	760	function will call C<croak>.
470		761
471	In list context, all parameters passed to C<send> will be returned,	762	In list context, all parameters passed to C<send> will be returned,
472	in scalar context only the first one will be returned.	763	in scalar context only the first one will be returned.
473		764
		765	Note that doing a blocking wait in a callback is not supported by any
		766	event loop, that is, recursive invocation of a blocking C<< ->recv
		767	>> is not allowed, and the C<recv> call will C<croak> if such a
		768	condition is detected. This condition can be slightly loosened by using
		769	L<Coro::AnyEvent>, which allows you to do a blocking C<< ->recv >> from
		770	any thread that doesn't run the event loop itself.
		771
474	Not all event models support a blocking wait - some die in that case	772	Not all event models support a blocking wait - some die in that case
475	(programs might want to do that to stay interactive), so I<if you are	773	(programs might want to do that to stay interactive), so I<if you are
476	using this from a module, never require a blocking wait>, but let the	774	using this from a module, never require a blocking wait>. Instead, let the
477	caller decide whether the call will block or not (for example, by coupling	775	caller decide whether the call will block or not (for example, by coupling
478	condition variables with some kind of request results and supporting	776	condition variables with some kind of request results and supporting
479	callbacks so the caller knows that getting the result will not block,	777	callbacks so the caller knows that getting the result will not block,
480	while still suppporting blocking waits if the caller so desires).	778	while still supporting blocking waits if the caller so desires).
481		779
482	Another reason I<never> to C<< ->wait >> in a module is that you cannot
483	sensibly have two C<< ->wait >>'s in parallel, as that would require
484	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
485	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and
486	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
487	from different coroutines, however).
488
489	You can ensure that C<< -wait >> never blocks by setting a callback and	780	You can ensure that C<< -recv >> never blocks by setting a callback and
490	only calling C<< ->wait >> from within that callback (or at a later	781	only calling C<< ->recv >> from within that callback (or at a later
491	time). This will work even when the event loop does not support blocking	782	time). This will work even when the event loop does not support blocking
492	waits otherwise.	783	waits otherwise.
493		784
494	=item $bool = $cv->ready	785	=item $bool = $cv->ready
495		786
496	Returns true when the condition is "true", i.e. whether C<send> or	787	Returns true when the condition is "true", i.e. whether C<send> or
497	C<croak> have been called.	788	C<croak> have been called.
498		789
499	=item $cb = $cv->cb ([new callback])	790	=item $cb = $cv->cb ($cb->($cv))
500		791
501	This is a mutator function that returns the callback set and optionally	792	This is a mutator function that returns the callback set and optionally
502	replaces it before doing so.	793	replaces it before doing so.
503		794
504	The callback will be called when the condition becomes "true", i.e. when	795	The callback will be called when the condition becomes "true", i.e. when
505	C<send> or C<croak> are called. Calling C<wait> inside the callback	796	C<send> or C<croak> are called, with the only argument being the condition
506	or at any later time is guaranteed not to block.	797	variable itself. Calling C<recv> inside the callback or at any later time
		798	is guaranteed not to block.
507		799
508	=back	800	=back
509		801
		802	=head1 SUPPORTED EVENT LOOPS/BACKENDS
		803
		804	The available backend classes are (every class has its own manpage):
		805
		806	=over 4
		807
		808	=item Backends that are autoprobed when no other event loop can be found.
		809
		810	EV is the preferred backend when no other event loop seems to be in
		811	use. If EV is not installed, then AnyEvent will try Event, and, failing
		812	that, will fall back to its own pure-perl implementation, which is
		813	available everywhere as it comes with AnyEvent itself.
		814
		815	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		816	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		817	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
		818
		819	=item Backends that are transparently being picked up when they are used.
		820
		821	These will be used when they are currently loaded when the first watcher
		822	is created, in which case it is assumed that the application is using
		823	them. This means that AnyEvent will automatically pick the right backend
		824	when the main program loads an event module before anything starts to
		825	create watchers. Nothing special needs to be done by the main program.
		826
		827	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		828	AnyEvent::Impl::Tk based on Tk, very broken.
		829	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		830	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		831	AnyEvent::Impl::Irssi used when running within irssi.
		832
		833	=item Backends with special needs.
		834
		835	Qt requires the Qt::Application to be instantiated first, but will
		836	otherwise be picked up automatically. As long as the main program
		837	instantiates the application before any AnyEvent watchers are created,
		838	everything should just work.
		839
		840	AnyEvent::Impl::Qt based on Qt.
		841
		842	Support for IO::Async can only be partial, as it is too broken and
		843	architecturally limited to even support the AnyEvent API. It also
		844	is the only event loop that needs the loop to be set explicitly, so
		845	it can only be used by a main program knowing about AnyEvent. See
		846	L<AnyEvent::Impl::Async> for the gory details.
		847
		848	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
		849
		850	=item Event loops that are indirectly supported via other backends.
		851
		852	Some event loops can be supported via other modules:
		853
		854	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		855
		856	B<WxWidgets> has no support for watching file handles. However, you can
		857	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		858	polls 20 times per second, which was considered to be too horrible to even
		859	consider for AnyEvent.
		860
		861	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		862	backend, so it can be supported through POE.
		863
		864	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		865	load L<POE> when detecting them, in the hope that POE will pick them up,
		866	in which case everything will be automatic.
		867
		868	=back
		869
510	=head1 GLOBAL VARIABLES AND FUNCTIONS	870	=head1 GLOBAL VARIABLES AND FUNCTIONS
511		871
		872	These are not normally required to use AnyEvent, but can be useful to
		873	write AnyEvent extension modules.
		874
512	=over 4	875	=over 4
513		876
514	=item $AnyEvent::MODEL	877	=item $AnyEvent::MODEL
515		878
516	Contains C<undef> until the first watcher is being created. Then it	879	Contains C<undef> until the first watcher is being created, before the
		880	backend has been autodetected.
		881
517	contains the event model that is being used, which is the name of the	882	Afterwards it contains the event model that is being used, which is the
518	Perl class implementing the model. This class is usually one of the	883	name of the Perl class implementing the model. This class is usually one
519	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	884	of the C<AnyEvent::Impl:xxx> modules, but can be any other class in the
520	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	885	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
521		886	will be C<urxvt::anyevent>).
522	The known classes so far are:
523
524	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
525	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
526	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
527	AnyEvent::Impl::Event based on Event, second best choice.
528	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
529	AnyEvent::Impl::Glib based on Glib, third-best choice.
530	AnyEvent::Impl::Tk based on Tk, very bad choice.
531	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
532	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
533	AnyEvent::Impl::POE based on POE, not generic enough for full support.
534
535	There is no support for WxWidgets, as WxWidgets has no support for
536	watching file handles. However, you can use WxWidgets through the
537	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
538	second, which was considered to be too horrible to even consider for
539	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
540	it's adaptor.
541
542	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
543	autodetecting them.
544		887
545	=item AnyEvent::detect	888	=item AnyEvent::detect
546		889
547	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	890	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
548	if necessary. You should only call this function right before you would	891	if necessary. You should only call this function right before you would
549	have created an AnyEvent watcher anyway, that is, as late as possible at	892	have created an AnyEvent watcher anyway, that is, as late as possible at
550	runtime.	893	runtime, and not e.g. while initialising of your module.
		894
		895	If you need to do some initialisation before AnyEvent watchers are
		896	created, use C<post_detect>.
		897
		898	=item $guard = AnyEvent::post_detect { BLOCK }
		899
		900	Arranges for the code block to be executed as soon as the event model is
		901	autodetected (or immediately if this has already happened).
		902
		903	The block will be executed I<after> the actual backend has been detected
		904	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		905	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		906	other initialisations - see the sources of L<AnyEvent::Strict> or
		907	L<AnyEvent::AIO> to see how this is used.
		908
		909	The most common usage is to create some global watchers, without forcing
		910	event module detection too early, for example, L<AnyEvent::AIO> creates
		911	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		912	avoid autodetecting the event module at load time.
		913
		914	If called in scalar or list context, then it creates and returns an object
		915	that automatically removes the callback again when it is destroyed (or
		916	C<undef> when the hook was immediately executed). See L<AnyEvent::AIO> for
		917	a case where this is useful.
		918
		919	Example: Create a watcher for the IO::AIO module and store it in
		920	C<$WATCHER>. Only do so after the event loop is initialised, though.
		921
		922	our WATCHER;
		923
		924	my $guard = AnyEvent::post_detect {
		925	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		926	};
		927
		928	# the ||= is important in case post_detect immediately runs the block,
		929	# as to not clobber the newly-created watcher. assigning both watcher and
		930	# post_detect guard to the same variable has the advantage of users being
		931	# able to just C<undef $WATCHER> if the watcher causes them grief.
		932
		933	$WATCHER ||= $guard;
		934
		935	=item @AnyEvent::post_detect
		936
		937	If there are any code references in this array (you can C<push> to it
		938	before or after loading AnyEvent), then they will called directly after
		939	the event loop has been chosen.
		940
		941	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		942	if it is defined then the event loop has already been detected, and the
		943	array will be ignored.
		944
		945	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		946	it,as it takes care of these details.
		947
		948	This variable is mainly useful for modules that can do something useful
		949	when AnyEvent is used and thus want to know when it is initialised, but do
		950	not need to even load it by default. This array provides the means to hook
		951	into AnyEvent passively, without loading it.
551		952
552	=back	953	=back
553		954
554	=head1 WHAT TO DO IN A MODULE	955	=head1 WHAT TO DO IN A MODULE
555		956
…		…
559	Be careful when you create watchers in the module body - AnyEvent will	960	Be careful when you create watchers in the module body - AnyEvent will
560	decide which event module to use as soon as the first method is called, so	961	decide which event module to use as soon as the first method is called, so
561	by calling AnyEvent in your module body you force the user of your module	962	by calling AnyEvent in your module body you force the user of your module
562	to load the event module first.	963	to load the event module first.
563		964
564	Never call C<< ->wait >> on a condition variable unless you I<know> that	965	Never call C<< ->recv >> on a condition variable unless you I<know> that
565	the C<< ->send >> method has been called on it already. This is	966	the C<< ->send >> method has been called on it already. This is
566	because it will stall the whole program, and the whole point of using	967	because it will stall the whole program, and the whole point of using
567	events is to stay interactive.	968	events is to stay interactive.
568		969
569	It is fine, however, to call C<< ->wait >> when the user of your module	970	It is fine, however, to call C<< ->recv >> when the user of your module
570	requests it (i.e. if you create a http request object ad have a method	971	requests it (i.e. if you create a http request object ad have a method
571	called C<results> that returns the results, it should call C<< ->wait >>	972	called C<results> that returns the results, it should call C<< ->recv >>
572	freely, as the user of your module knows what she is doing. always).	973	freely, as the user of your module knows what she is doing. always).
573		974
574	=head1 WHAT TO DO IN THE MAIN PROGRAM	975	=head1 WHAT TO DO IN THE MAIN PROGRAM
575		976
576	There will always be a single main program - the only place that should	977	There will always be a single main program - the only place that should
…		…
578		979
579	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	980	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
580	do anything special (it does not need to be event-based) and let AnyEvent	981	do anything special (it does not need to be event-based) and let AnyEvent
581	decide which implementation to chose if some module relies on it.	982	decide which implementation to chose if some module relies on it.
582		983
583	If the main program relies on a specific event model. For example, in	984	If the main program relies on a specific event model - for example, in
584	Gtk2 programs you have to rely on the Glib module. You should load the	985	Gtk2 programs you have to rely on the Glib module - you should load the
585	event module before loading AnyEvent or any module that uses it: generally	986	event module before loading AnyEvent or any module that uses it: generally
586	speaking, you should load it as early as possible. The reason is that	987	speaking, you should load it as early as possible. The reason is that
587	modules might create watchers when they are loaded, and AnyEvent will	988	modules might create watchers when they are loaded, and AnyEvent will
588	decide on the event model to use as soon as it creates watchers, and it	989	decide on the event model to use as soon as it creates watchers, and it
589	might chose the wrong one unless you load the correct one yourself.	990	might chose the wrong one unless you load the correct one yourself.
590		991
591	You can chose to use a rather inefficient pure-perl implementation by	992	You can chose to use a pure-perl implementation by loading the
592	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	993	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
593	behaviour everywhere, but letting AnyEvent chose is generally better.	994	everywhere, but letting AnyEvent chose the model is generally better.
		995
		996	=head2 MAINLOOP EMULATION
		997
		998	Sometimes (often for short test scripts, or even standalone programs who
		999	only want to use AnyEvent), you do not want to run a specific event loop.
		1000
		1001	In that case, you can use a condition variable like this:
		1002
		1003	AnyEvent->condvar->recv;
		1004
		1005	This has the effect of entering the event loop and looping forever.
		1006
		1007	Note that usually your program has some exit condition, in which case
		1008	it is better to use the "traditional" approach of storing a condition
		1009	variable somewhere, waiting for it, and sending it when the program should
		1010	exit cleanly.
		1011
594		1012
595	=head1 OTHER MODULES	1013	=head1 OTHER MODULES
596		1014
597	The following is a non-exhaustive list of additional modules that use	1015	The following is a non-exhaustive list of additional modules that use
598	AnyEvent and can therefore be mixed easily with other AnyEvent modules	1016	AnyEvent as a client and can therefore be mixed easily with other AnyEvent
599	in the same program. Some of the modules come with AnyEvent, some are	1017	modules and other event loops in the same program. Some of the modules
600	available via CPAN.	1018	come with AnyEvent, most are available via CPAN.
601		1019
602	=over 4	1020	=over 4
603		1021
604	=item L<AnyEvent::Util>	1022	=item L<AnyEvent::Util>
605		1023
606	Contains various utility functions that replace often-used but blocking	1024	Contains various utility functions that replace often-used but blocking
607	functions such as C<inet_aton> by event-/callback-based versions.	1025	functions such as C<inet_aton> by event-/callback-based versions.
608		1026
		1027	=item L<AnyEvent::Socket>
		1028
		1029	Provides various utility functions for (internet protocol) sockets,
		1030	addresses and name resolution. Also functions to create non-blocking tcp
		1031	connections or tcp servers, with IPv6 and SRV record support and more.
		1032
609	=item L<AnyEvent::Handle>	1033	=item L<AnyEvent::Handle>
610		1034
611	Provide read and write buffers and manages watchers for reads and writes.	1035	Provide read and write buffers, manages watchers for reads and writes,
		1036	supports raw and formatted I/O, I/O queued and fully transparent and
		1037	non-blocking SSL/TLS (via L<AnyEvent::TLS>.
612		1038
613	=item L<AnyEvent::Socket>	1039	=item L<AnyEvent::DNS>
614		1040
615	Provides a means to do non-blocking connects, accepts etc.	1041	Provides rich asynchronous DNS resolver capabilities.
		1042
		1043	=item L<AnyEvent::HTTP>
		1044
		1045	A simple-to-use HTTP library that is capable of making a lot of concurrent
		1046	HTTP requests.
616		1047
617	=item L<AnyEvent::HTTPD>	1048	=item L<AnyEvent::HTTPD>
618		1049
619	Provides a simple web application server framework.	1050	Provides a simple web application server framework.
620		1051
621	=item L<AnyEvent::DNS>
622
623	Provides asynchronous DNS resolver capabilities, beyond what
624	L<AnyEvent::Util> offers.
625
626	=item L<AnyEvent::FastPing>	1052	=item L<AnyEvent::FastPing>
627		1053
628	The fastest ping in the west.	1054	The fastest ping in the west.
629		1055
		1056	=item L<AnyEvent::DBI>
		1057
		1058	Executes L<DBI> requests asynchronously in a proxy process.
		1059
		1060	=item L<AnyEvent::AIO>
		1061
		1062	Truly asynchronous I/O, should be in the toolbox of every event
		1063	programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
		1064	together.
		1065
		1066	=item L<AnyEvent::BDB>
		1067
		1068	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
		1069	L<BDB> and AnyEvent together.
		1070
		1071	=item L<AnyEvent::GPSD>
		1072
		1073	A non-blocking interface to gpsd, a daemon delivering GPS information.
		1074
630	=item L<Net::IRC3>	1075	=item L<AnyEvent::IRC>
631		1076
632	AnyEvent based IRC client module family.	1077	AnyEvent based IRC client module family (replacing the older Net::IRC3).
633		1078
634	=item L<Net::XMPP2>	1079	=item L<AnyEvent::XMPP>
635		1080
636	AnyEvent based XMPP (Jabber protocol) module family.	1081	AnyEvent based XMPP (Jabber protocol) module family (replacing the older
		1082	Net::XMPP2>.
		1083
		1084	=item L<AnyEvent::IGS>
		1085
		1086	A non-blocking interface to the Internet Go Server protocol (used by
		1087	L<App::IGS>).
637		1088
638	=item L<Net::FCP>	1089	=item L<Net::FCP>
639		1090
640	AnyEvent-based implementation of the Freenet Client Protocol, birthplace	1091	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
641	of AnyEvent.	1092	of AnyEvent.
…		…
644		1095
645	High level API for event-based execution flow control.	1096	High level API for event-based execution flow control.
646		1097
647	=item L<Coro>	1098	=item L<Coro>
648		1099
649	Has special support for AnyEvent.	1100	Has special support for AnyEvent via L<Coro::AnyEvent>.
650
651	=item L<IO::Lambda>
652
653	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
654
655	=item L<IO::AIO>
656
657	Truly asynchronous I/O, should be in the toolbox of every event
658	programmer. Can be trivially made to use AnyEvent.
659
660	=item L<BDB>
661
662	Truly asynchronous Berkeley DB access. Can be trivially made to use
663	AnyEvent.
664		1101
665	=back	1102	=back
666		1103
667	=cut	1104	=cut
668		1105
669	package AnyEvent;	1106	package AnyEvent;
670		1107
		1108	# basically a tuned-down version of common::sense
		1109	sub common_sense {
671	no warnings;	1110	# no warnings
672	use strict;	1111	${^WARNING_BITS} ^= ${^WARNING_BITS};
		1112	# use strict vars subs
		1113	$^H |= 0x00000600;
		1114	}
673		1115
		1116	BEGIN { AnyEvent::common_sense }
		1117
674	use Carp;	1118	use Carp ();
675		1119
676	our $VERSION = '3.3';	1120	our $VERSION = 4.881;
677	our $MODEL;	1121	our $MODEL;
678		1122
679	our $AUTOLOAD;	1123	our $AUTOLOAD;
680	our @ISA;	1124	our @ISA;
681		1125
682	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
683
684	our @REGISTRY;	1126	our @REGISTRY;
685		1127
		1128	our $WIN32;
		1129
		1130	our $VERBOSE;
		1131
		1132	BEGIN {
		1133	eval "sub WIN32(){ " . (($^O =~ /mswin32/i)*1) ." }";
		1134	eval "sub TAINT(){ " . (${^TAINT}*1) . " }";
		1135
		1136	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1137	if ${^TAINT};
		1138
		1139	$VERBOSE = $ENV{PERL_ANYEVENT_VERBOSE}*1;
		1140
		1141	}
		1142
		1143	our $MAX_SIGNAL_LATENCY = 10;
		1144
		1145	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		1146
		1147	{
		1148	my $idx;
		1149	$PROTOCOL{$_} = ++$idx
		1150	for reverse split /\s*,\s*/,
		1151	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		1152	}
		1153
686	my @models = (	1154	my @models = (
687	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
688	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
689	[EV:: => AnyEvent::Impl::EV::],	1155	[EV:: => AnyEvent::Impl::EV:: , 1],
690	[Event:: => AnyEvent::Impl::Event::],	1156	[Event:: => AnyEvent::Impl::Event::, 1],
		1157	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl:: , 1],
		1158	# everything below here will not (normally) be autoprobed
		1159	# as the pureperl backend should work everywhere
		1160	# and is usually faster
		1161	[Glib:: => AnyEvent::Impl::Glib:: , 1], # becomes extremely slow with many watchers
		1162	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		1163	[Irssi:: => AnyEvent::Impl::Irssi::], # Irssi has a bogus "Event" package
691	[Tk:: => AnyEvent::Impl::Tk::],	1164	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		1165	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		1166	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
692	[Wx:: => AnyEvent::Impl::POE::],	1167	[Wx:: => AnyEvent::Impl::POE::],
693	[Prima:: => AnyEvent::Impl::POE::],	1168	[Prima:: => AnyEvent::Impl::POE::],
694	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1169	# IO::Async is just too broken - we would need workarounds for its
695	# everything below here will not be autoprobed as the pureperl backend should work everywhere	1170	# byzantine signal and broken child handling, among others.
696	[Glib:: => AnyEvent::Impl::Glib::],	1171	# IO::Async is rather hard to detect, as it doesn't have any
697	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy	1172	# obvious default class.
698	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program	1173	# [0, IO::Async:: => AnyEvent::Impl::IOAsync::], # requires special main program
699	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza	1174	# [0, IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1175	# [0, IO::Async::Notifier:: => AnyEvent::Impl::IOAsync::], # requires special main program
700	);	1176	);
701		1177
702	our %method = map +($_ => 1), qw(io timer signal child condvar one_event DESTROY);	1178	our %method = map +($_ => 1),
		1179	qw(io timer time now now_update signal child idle condvar one_event DESTROY);
		1180
		1181	our @post_detect;
		1182
		1183	sub post_detect(&) {
		1184	my ($cb) = @_;
		1185
		1186	if ($MODEL) {
		1187	$cb->();
		1188
		1189	undef
		1190	} else {
		1191	push @post_detect, $cb;
		1192
		1193	defined wantarray
		1194	? bless \$cb, "AnyEvent::Util::postdetect"
		1195	: ()
		1196	}
		1197	}
		1198
		1199	sub AnyEvent::Util::postdetect::DESTROY {
		1200	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		1201	}
703		1202
704	sub detect() {	1203	sub detect() {
705	unless ($MODEL) {	1204	unless ($MODEL) {
706	no strict 'refs';	1205	local $SIG{__DIE__};
707		1206
708	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	1207	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
709	my $model = "AnyEvent::Impl::$1";	1208	my $model = "AnyEvent::Impl::$1";
710	if (eval "require $model") {	1209	if (eval "require $model") {
711	$MODEL = $model;	1210	$MODEL = $model;
712	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	1211	warn "AnyEvent: loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.\n" if $VERBOSE >= 2;
713	} else {	1212	} else {
714	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;	1213	warn "AnyEvent: unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@" if $VERBOSE;
715	}	1214	}
716	}	1215	}
717		1216
718	# check for already loaded models	1217	# check for already loaded models
719	unless ($MODEL) {	1218	unless ($MODEL) {
720	for (@REGISTRY, @models) {	1219	for (@REGISTRY, @models) {
721	my ($package, $model) = @$_;	1220	my ($package, $model) = @$_;
722	if (${"$package\::VERSION"} > 0) {	1221	if (${"$package\::VERSION"} > 0) {
723	if (eval "require $model") {	1222	if (eval "require $model") {
724	$MODEL = $model;	1223	$MODEL = $model;
725	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;	1224	warn "AnyEvent: autodetected model '$model', using it.\n" if $VERBOSE >= 2;
726	last;	1225	last;
727	}	1226	}
728	}	1227	}
729	}	1228	}
730		1229
731	unless ($MODEL) {	1230	unless ($MODEL) {
732	# try to load a model	1231	# try to autoload a model
733
734	for (@REGISTRY, @models) {	1232	for (@REGISTRY, @models) {
735	my ($package, $model) = @$_;	1233	my ($package, $model, $autoload) = @$_;
		1234	if (
		1235	$autoload
736	if (eval "require $package"	1236	and eval "require $package"
737	and ${"$package\::VERSION"} > 0	1237	and ${"$package\::VERSION"} > 0
738	and eval "require $model") {	1238	and eval "require $model"
		1239	) {
739	$MODEL = $model;	1240	$MODEL = $model;
740	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;	1241	warn "AnyEvent: autoloaded model '$model', using it.\n" if $VERBOSE >= 2;
741	last;	1242	last;
742	}	1243	}
743	}	1244	}
744		1245
745	$MODEL	1246	$MODEL
746	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV (or Coro+EV), Event (or Coro+Event) or Glib.";	1247	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.\n";
747	}	1248	}
748	}	1249	}
749		1250
		1251	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		1252
750	unshift @ISA, $MODEL;	1253	unshift @ISA, $MODEL;
751	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	1254
		1255	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
		1256
		1257	(shift @post_detect)->() while @post_detect;
752	}	1258	}
753		1259
754	$MODEL	1260	$MODEL
755	}	1261	}
756		1262
757	sub AUTOLOAD {	1263	sub AUTOLOAD {
758	(my $func = $AUTOLOAD) =~ s/.*://;	1264	(my $func = $AUTOLOAD) =~ s/.*://;
759		1265
760	$method{$func}	1266	$method{$func}
761	or croak "$func: not a valid method for AnyEvent objects";	1267	or Carp::croak "$func: not a valid method for AnyEvent objects";
762		1268
763	detect unless $MODEL;	1269	detect unless $MODEL;
764		1270
765	my $class = shift;	1271	my $class = shift;
766	$class->$func (@_);	1272	$class->$func (@_);
767	}	1273	}
768		1274
		1275	# utility function to dup a filehandle. this is used by many backends
		1276	# to support binding more than one watcher per filehandle (they usually
		1277	# allow only one watcher per fd, so we dup it to get a different one).
		1278	sub _dupfh($$;$$) {
		1279	my ($poll, $fh, $r, $w) = @_;
		1280
		1281	# cygwin requires the fh mode to be matching, unix doesn't
		1282	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1283
		1284	open my $fh2, $mode, $fh
		1285	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1286
		1287	# we assume CLOEXEC is already set by perl in all important cases
		1288
		1289	($fh2, $rw)
		1290	}
		1291
769	package AnyEvent::Base;	1292	package AnyEvent::Base;
770		1293
		1294	# default implementations for many methods
		1295
		1296	sub _time {
		1297	# probe for availability of Time::HiRes
		1298	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1299	warn "AnyEvent: using Time::HiRes for sub-second timing accuracy.\n" if $VERBOSE >= 8;
		1300	*_time = \&Time::HiRes::time;
		1301	# if (eval "use POSIX (); (POSIX::times())...
		1302	} else {
		1303	warn "AnyEvent: using built-in time(), WARNING, no sub-second resolution!\n" if $VERBOSE;
		1304	*_time = sub { time }; # epic fail
		1305	}
		1306
		1307	&_time
		1308	}
		1309
		1310	sub time { _time }
		1311	sub now { _time }
		1312	sub now_update { }
		1313
771	# default implementation for ->condvar, ->wait, ->broadcast	1314	# default implementation for ->condvar
772		1315
773	sub condvar {	1316	sub condvar {
774	bless \my $flag, "AnyEvent::Base::CondVar"	1317	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
775	}
776
777	sub AnyEvent::Base::CondVar::broadcast {
778	${$_[0]}++;
779	}
780
781	sub AnyEvent::Base::CondVar::wait {
782	AnyEvent->one_event while !${$_[0]};
783	}	1318	}
784		1319
785	# default implementation for ->signal	1320	# default implementation for ->signal
786		1321
787	our %SIG_CB;	1322	our $HAVE_ASYNC_INTERRUPT;
		1323
		1324	sub _have_async_interrupt() {
		1325	$HAVE_ASYNC_INTERRUPT = 1*(!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT}
		1326	&& eval "use Async::Interrupt 1.0 (); 1")
		1327	unless defined $HAVE_ASYNC_INTERRUPT;
		1328
		1329	$HAVE_ASYNC_INTERRUPT
		1330	}
		1331
		1332	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1333	our (%SIG_ASY, %SIG_ASY_W);
		1334	our ($SIG_COUNT, $SIG_TW);
		1335
		1336	sub _signal_exec {
		1337	$HAVE_ASYNC_INTERRUPT
		1338	? $SIGPIPE_R->drain
		1339	: sysread $SIGPIPE_R, my $dummy, 9;
		1340
		1341	while (%SIG_EV) {
		1342	for (keys %SIG_EV) {
		1343	delete $SIG_EV{$_};
		1344	$_->() for values %{ $SIG_CB{$_} || {} };
		1345	}
		1346	}
		1347	}
		1348
		1349	# install a dummy wakeup watcher to reduce signal catching latency
		1350	sub _sig_add() {
		1351	unless ($SIG_COUNT++) {
		1352	# try to align timer on a full-second boundary, if possible
		1353	my $NOW = AnyEvent->now;
		1354
		1355	$SIG_TW = AnyEvent->timer (
		1356	after => $MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1357	interval => $MAX_SIGNAL_LATENCY,
		1358	cb => sub { }, # just for the PERL_ASYNC_CHECK
		1359	);
		1360	}
		1361	}
		1362
		1363	sub _sig_del {
		1364	undef $SIG_TW
		1365	unless --$SIG_COUNT;
		1366	}
		1367
		1368	our $_sig_name_init; $_sig_name_init = sub {
		1369	eval q{ # poor man's autoloading
		1370	undef $_sig_name_init;
		1371
		1372	if (_have_async_interrupt) {
		1373	*sig2num = \&Async::Interrupt::sig2num;
		1374	*sig2name = \&Async::Interrupt::sig2name;
		1375	} else {
		1376	require Config;
		1377
		1378	my %signame2num;
		1379	@signame2num{ split ' ', $Config::Config{sig_name} }
		1380	= split ' ', $Config::Config{sig_num};
		1381
		1382	my @signum2name;
		1383	@signum2name[values %signame2num] = keys %signame2num;
		1384
		1385	*sig2num = sub($) {
		1386	$_[0] > 0 ? shift : $signame2num{+shift}
		1387	};
		1388	*sig2name = sub ($) {
		1389	$_[0] > 0 ? $signum2name[+shift] : shift
		1390	};
		1391	}
		1392	};
		1393	die if $@;
		1394	};
		1395
		1396	sub sig2num ($) { &$_sig_name_init; &sig2num }
		1397	sub sig2name($) { &$_sig_name_init; &sig2name }
788		1398
789	sub signal {	1399	sub signal {
		1400	eval q{ # poor man's autoloading {}
		1401	# probe for availability of Async::Interrupt
		1402	if (_have_async_interrupt) {
		1403	warn "AnyEvent: using Async::Interrupt for race-free signal handling.\n" if $VERBOSE >= 8;
		1404
		1405	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1406	$SIG_IO = AnyEvent->io (fh => $SIGPIPE_R->fileno, poll => "r", cb => \&_signal_exec);
		1407
		1408	} else {
		1409	warn "AnyEvent: using emulated perl signal handling with latency timer.\n" if $VERBOSE >= 8;
		1410
		1411	require Fcntl;
		1412
		1413	if (AnyEvent::WIN32) {
		1414	require AnyEvent::Util;
		1415
		1416	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1417	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R, 1) if $SIGPIPE_R;
		1418	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W, 1) if $SIGPIPE_W; # just in case
		1419	} else {
		1420	pipe $SIGPIPE_R, $SIGPIPE_W;
		1421	fcntl $SIGPIPE_R, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_R;
		1422	fcntl $SIGPIPE_W, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_W; # just in case
		1423
		1424	# not strictly required, as $^F is normally 2, but let's make sure...
		1425	fcntl $SIGPIPE_R, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1426	fcntl $SIGPIPE_W, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1427	}
		1428
		1429	$SIGPIPE_R
		1430	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1431
		1432	$SIG_IO = AnyEvent->io (fh => $SIGPIPE_R, poll => "r", cb => \&_signal_exec);
		1433	}
		1434
		1435	*signal = sub {
790	my (undef, %arg) = @_;	1436	my (undef, %arg) = @_;
791		1437
792	my $signal = uc $arg{signal}	1438	my $signal = uc $arg{signal}
793	or Carp::croak "required option 'signal' is missing";	1439	or Carp::croak "required option 'signal' is missing";
794		1440
		1441	if ($HAVE_ASYNC_INTERRUPT) {
		1442	# async::interrupt
		1443
		1444	$signal = sig2num $signal;
795	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1445	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1446
		1447	$SIG_ASY{$signal} ||= new Async::Interrupt
		1448	cb => sub { undef $SIG_EV{$signal} },
		1449	signal => $signal,
		1450	pipe => [$SIGPIPE_R->filenos],
		1451	pipe_autodrain => 0,
		1452	;
		1453
		1454	} else {
		1455	# pure perl
		1456
		1457	# AE::Util has been loaded in signal
		1458	$signal = sig2name $signal;
		1459	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1460
796	$SIG{$signal} ||= sub {	1461	$SIG{$signal} ||= sub {
797	$_->() for values %{ $SIG_CB{$signal} || {} };	1462	local $!;
		1463	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1464	undef $SIG_EV{$signal};
		1465	};
		1466
		1467	# can't do signal processing without introducing races in pure perl,
		1468	# so limit the signal latency.
		1469	_sig_add;
		1470	}
		1471
		1472	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1473	};
		1474
		1475	*AnyEvent::Base::signal::DESTROY = sub {
		1476	my ($signal, $cb) = @{$_[0]};
		1477
		1478	_sig_del;
		1479
		1480	delete $SIG_CB{$signal}{$cb};
		1481
		1482	$HAVE_ASYNC_INTERRUPT
		1483	? delete $SIG_ASY{$signal}
		1484	: # delete doesn't work with older perls - they then
		1485	# print weird messages, or just unconditionally exit
		1486	# instead of getting the default action.
		1487	undef $SIG{$signal}
		1488	unless keys %{ $SIG_CB{$signal} };
		1489	};
798	};	1490	};
799		1491	die if $@;
800	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1492	&signal
801	}
802
803	sub AnyEvent::Base::Signal::DESTROY {
804	my ($signal, $cb) = @{$_[0]};
805
806	delete $SIG_CB{$signal}{$cb};
807
808	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };
809	}	1493	}
810		1494
811	# default implementation for ->child	1495	# default implementation for ->child
812		1496
813	our %PID_CB;	1497	our %PID_CB;
814	our $CHLD_W;	1498	our $CHLD_W;
815	our $CHLD_DELAY_W;	1499	our $CHLD_DELAY_W;
816	our $PID_IDLE;
817	our $WNOHANG;	1500	our $WNOHANG;
818		1501
819	sub _child_wait {	1502	sub _emit_childstatus($$) {
820	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1503	my (undef, $rpid, $rstatus) = @_;
		1504
		1505	$_->($rpid, $rstatus)
821	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1506	for values %{ $PID_CB{$rpid} || {} },
822	(values %{ $PID_CB{0} || {} });	1507	values %{ $PID_CB{0} || {} };
823	}
824
825	undef $PID_IDLE;
826	}	1508	}
827		1509
828	sub _sigchld {	1510	sub _sigchld {
829	# make sure we deliver these changes "synchronous" with the event loop.	1511	my $pid;
830	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {	1512
831	undef $CHLD_DELAY_W;	1513	AnyEvent->_emit_childstatus ($pid, $?)
832	&_child_wait;	1514	while ($pid = waitpid -1, $WNOHANG) > 0;
833	});
834	}	1515	}
835		1516
836	sub child {	1517	sub child {
837	my (undef, %arg) = @_;	1518	my (undef, %arg) = @_;
838		1519
839	defined (my $pid = $arg{pid} + 0)	1520	defined (my $pid = $arg{pid} + 0)
840	or Carp::croak "required option 'pid' is missing";	1521	or Carp::croak "required option 'pid' is missing";
841		1522
842	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1523	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
843		1524
844	unless ($WNOHANG) {	1525	# WNOHANG is almost cetrainly 1 everywhere
845	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;	1526	$WNOHANG ||= $^O =~ /^(?:openbsd|netbsd|linux|freebsd|cygwin|MSWin32)$/
846	}	1527	? 1
		1528	: eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
847		1529
848	unless ($CHLD_W) {	1530	unless ($CHLD_W) {
849	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1531	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
850	# child could be a zombie already, so make at least one round	1532	# child could be a zombie already, so make at least one round
851	&_sigchld;	1533	&_sigchld;
852	}	1534	}
853		1535
854	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	1536	bless [$pid, $arg{cb}], "AnyEvent::Base::child"
855	}	1537	}
856		1538
857	sub AnyEvent::Base::Child::DESTROY {	1539	sub AnyEvent::Base::child::DESTROY {
858	my ($pid, $cb) = @{$_[0]};	1540	my ($pid, $cb) = @{$_[0]};
859		1541
860	delete $PID_CB{$pid}{$cb};	1542	delete $PID_CB{$pid}{$cb};
861	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1543	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
862		1544
863	undef $CHLD_W unless keys %PID_CB;	1545	undef $CHLD_W unless keys %PID_CB;
864	}	1546	}
		1547
		1548	# idle emulation is done by simply using a timer, regardless
		1549	# of whether the process is idle or not, and not letting
		1550	# the callback use more than 50% of the time.
		1551	sub idle {
		1552	my (undef, %arg) = @_;
		1553
		1554	my ($cb, $w, $rcb) = $arg{cb};
		1555
		1556	$rcb = sub {
		1557	if ($cb) {
		1558	$w = _time;
		1559	&$cb;
		1560	$w = _time - $w;
		1561
		1562	# never use more then 50% of the time for the idle watcher,
		1563	# within some limits
		1564	$w = 0.0001 if $w < 0.0001;
		1565	$w = 5 if $w > 5;
		1566
		1567	$w = AnyEvent->timer (after => $w, cb => $rcb);
		1568	} else {
		1569	# clean up...
		1570	undef $w;
		1571	undef $rcb;
		1572	}
		1573	};
		1574
		1575	$w = AnyEvent->timer (after => 0.05, cb => $rcb);
		1576
		1577	bless \\$cb, "AnyEvent::Base::idle"
		1578	}
		1579
		1580	sub AnyEvent::Base::idle::DESTROY {
		1581	undef $${$_[0]};
		1582	}
		1583
		1584	package AnyEvent::CondVar;
		1585
		1586	our @ISA = AnyEvent::CondVar::Base::;
		1587
		1588	package AnyEvent::CondVar::Base;
		1589
		1590	#use overload
		1591	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1592	# fallback => 1;
		1593
		1594	# save 300+ kilobytes by dirtily hardcoding overloading
		1595	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1596	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1597	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1598	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1599
		1600	our $WAITING;
		1601
		1602	sub _send {
		1603	# nop
		1604	}
		1605
		1606	sub send {
		1607	my $cv = shift;
		1608	$cv->{_ae_sent} = [@_];
		1609	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1610	$cv->_send;
		1611	}
		1612
		1613	sub croak {
		1614	$_[0]{_ae_croak} = $_[1];
		1615	$_[0]->send;
		1616	}
		1617
		1618	sub ready {
		1619	$_[0]{_ae_sent}
		1620	}
		1621
		1622	sub _wait {
		1623	$WAITING
		1624	and !$_[0]{_ae_sent}
		1625	and Carp::croak "AnyEvent::CondVar: recursive blocking wait detected";
		1626
		1627	local $WAITING = 1;
		1628	AnyEvent->one_event while !$_[0]{_ae_sent};
		1629	}
		1630
		1631	sub recv {
		1632	$_[0]->_wait;
		1633
		1634	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
		1635	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
		1636	}
		1637
		1638	sub cb {
		1639	$_[0]{_ae_cb} = $_[1] if @_ > 1;
		1640	$_[0]{_ae_cb}
		1641	}
		1642
		1643	sub begin {
		1644	++$_[0]{_ae_counter};
		1645	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
		1646	}
		1647
		1648	sub end {
		1649	return if --$_[0]{_ae_counter};
		1650	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		1651	}
		1652
		1653	# undocumented/compatibility with pre-3.4
		1654	*broadcast = \&send;
		1655	*wait = \&_wait;
		1656
		1657	#############################################################################
		1658	# "new" API, currently only emulation of it
		1659	#############################################################################
		1660
		1661	package AE;
		1662
		1663	sub io($$$) {
		1664	AnyEvent->io (fh => $_[0], poll => $_[1] ? "w" : "r", cb => $_[2])
		1665	}
		1666
		1667	sub timer($$$) {
		1668	AnyEvent->timer (after => $_[0], interval => $_[1], cb => $_[2]);
		1669	}
		1670
		1671	sub signal($$) {
		1672	AnyEvent->signal (signal => $_[0], cb => $_[1]);
		1673	}
		1674
		1675	sub child($$) {
		1676	AnyEvent->child (pid => $_[0], cb => $_[1]);
		1677	}
		1678
		1679	sub idle($) {
		1680	AnyEvent->idle (cb => $_[0]);
		1681	}
		1682
		1683	sub cv() {
		1684	AnyEvent->condvar
		1685	}
		1686
		1687	sub now() {
		1688	AnyEvent->now
		1689	}
		1690
		1691	sub now_update() {
		1692	AnyEvent->now_update
		1693	}
		1694
		1695	sub time() {
		1696	AnyEvent->time
		1697	}
		1698
		1699	=head1 ERROR AND EXCEPTION HANDLING
		1700
		1701	In general, AnyEvent does not do any error handling - it relies on the
		1702	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1703	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1704	checking of all AnyEvent methods, however, which is highly useful during
		1705	development.
		1706
		1707	As for exception handling (i.e. runtime errors and exceptions thrown while
		1708	executing a callback), this is not only highly event-loop specific, but
		1709	also not in any way wrapped by this module, as this is the job of the main
		1710	program.
		1711
		1712	The pure perl event loop simply re-throws the exception (usually
		1713	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1714	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1715	so on.
		1716
		1717	=head1 ENVIRONMENT VARIABLES
		1718
		1719	The following environment variables are used by this module or its
		1720	submodules.
		1721
		1722	Note that AnyEvent will remove I<all> environment variables starting with
		1723	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		1724	enabled.
		1725
		1726	=over 4
		1727
		1728	=item C<PERL_ANYEVENT_VERBOSE>
		1729
		1730	By default, AnyEvent will be completely silent except in fatal
		1731	conditions. You can set this environment variable to make AnyEvent more
		1732	talkative.
		1733
		1734	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1735	conditions, such as not being able to load the event model specified by
		1736	C<PERL_ANYEVENT_MODEL>.
		1737
		1738	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1739	model it chooses.
		1740
		1741	When set to C<8> or higher, then AnyEvent will report extra information on
		1742	which optional modules it loads and how it implements certain features.
		1743
		1744	=item C<PERL_ANYEVENT_STRICT>
		1745
		1746	AnyEvent does not do much argument checking by default, as thorough
		1747	argument checking is very costly. Setting this variable to a true value
		1748	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1749	check the arguments passed to most method calls. If it finds any problems,
		1750	it will croak.
		1751
		1752	In other words, enables "strict" mode.
		1753
		1754	Unlike C<use strict> (or it's modern cousin, C<< use L<common::sense>
		1755	>>, it is definitely recommended to keep it off in production. Keeping
		1756	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		1757	can be very useful, however.
		1758
		1759	=item C<PERL_ANYEVENT_MODEL>
		1760
		1761	This can be used to specify the event model to be used by AnyEvent, before
		1762	auto detection and -probing kicks in. It must be a string consisting
		1763	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1764	and the resulting module name is loaded and if the load was successful,
		1765	used as event model. If it fails to load AnyEvent will proceed with
		1766	auto detection and -probing.
		1767
		1768	This functionality might change in future versions.
		1769
		1770	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1771	could start your program like this:
		1772
		1773	PERL_ANYEVENT_MODEL=Perl perl ...
		1774
		1775	=item C<PERL_ANYEVENT_PROTOCOLS>
		1776
		1777	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1778	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1779	of auto probing).
		1780
		1781	Must be set to a comma-separated list of protocols or address families,
		1782	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1783	used, and preference will be given to protocols mentioned earlier in the
		1784	list.
		1785
		1786	This variable can effectively be used for denial-of-service attacks
		1787	against local programs (e.g. when setuid), although the impact is likely
		1788	small, as the program has to handle conenction and other failures anyways.
		1789
		1790	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1791	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1792	- only support IPv4, never try to resolve or contact IPv6
		1793	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1794	IPv6, but prefer IPv6 over IPv4.
		1795
		1796	=item C<PERL_ANYEVENT_EDNS0>
		1797
		1798	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1799	for DNS. This extension is generally useful to reduce DNS traffic, but
		1800	some (broken) firewalls drop such DNS packets, which is why it is off by
		1801	default.
		1802
		1803	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1804	EDNS0 in its DNS requests.
		1805
		1806	=item C<PERL_ANYEVENT_MAX_FORKS>
		1807
		1808	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1809	will create in parallel.
		1810
		1811	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		1812
		1813	The default value for the C<max_outstanding> parameter for the default DNS
		1814	resolver - this is the maximum number of parallel DNS requests that are
		1815	sent to the DNS server.
		1816
		1817	=item C<PERL_ANYEVENT_RESOLV_CONF>
		1818
		1819	The file to use instead of F</etc/resolv.conf> (or OS-specific
		1820	configuration) in the default resolver. When set to the empty string, no
		1821	default config will be used.
		1822
		1823	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		1824
		1825	When neither C<ca_file> nor C<ca_path> was specified during
		1826	L<AnyEvent::TLS> context creation, and either of these environment
		1827	variables exist, they will be used to specify CA certificate locations
		1828	instead of a system-dependent default.
		1829
		1830	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		1831
		1832	When these are set to C<1>, then the respective modules are not
		1833	loaded. Mostly good for testing AnyEvent itself.
		1834
		1835	=back
865		1836
866	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1837	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
867		1838
868	This is an advanced topic that you do not normally need to use AnyEvent in	1839	This is an advanced topic that you do not normally need to use AnyEvent in
869	a module. This section is only of use to event loop authors who want to	1840	a module. This section is only of use to event loop authors who want to
…		…
903		1874
904	I<rxvt-unicode> also cheats a bit by not providing blocking access to	1875	I<rxvt-unicode> also cheats a bit by not providing blocking access to
905	condition variables: code blocking while waiting for a condition will	1876	condition variables: code blocking while waiting for a condition will
906	C<die>. This still works with most modules/usages, and blocking calls must	1877	C<die>. This still works with most modules/usages, and blocking calls must
907	not be done in an interactive application, so it makes sense.	1878	not be done in an interactive application, so it makes sense.
908
909	=head1 ENVIRONMENT VARIABLES
910
911	The following environment variables are used by this module:
912
913	=over 4
914
915	=item C<PERL_ANYEVENT_VERBOSE>
916
917	By default, AnyEvent will be completely silent except in fatal
918	conditions. You can set this environment variable to make AnyEvent more
919	talkative.
920
921	When set to C<1> or higher, causes AnyEvent to warn about unexpected
922	conditions, such as not being able to load the event model specified by
923	C<PERL_ANYEVENT_MODEL>.
924
925	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
926	model it chooses.
927
928	=item C<PERL_ANYEVENT_MODEL>
929
930	This can be used to specify the event model to be used by AnyEvent, before
931	autodetection and -probing kicks in. It must be a string consisting
932	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
933	and the resulting module name is loaded and if the load was successful,
934	used as event model. If it fails to load AnyEvent will proceed with
935	autodetection and -probing.
936
937	This functionality might change in future versions.
938
939	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
940	could start your program like this:
941
942	PERL_ANYEVENT_MODEL=Perl perl ...
943
944	=back
945		1879
946	=head1 EXAMPLE PROGRAM	1880	=head1 EXAMPLE PROGRAM
947		1881
948	The following program uses an I/O watcher to read data from STDIN, a timer	1882	The following program uses an I/O watcher to read data from STDIN, a timer
949	to display a message once per second, and a condition variable to quit the	1883	to display a message once per second, and a condition variable to quit the
…		…
958	poll => 'r',	1892	poll => 'r',
959	cb => sub {	1893	cb => sub {
960	warn "io event <$_[0]>\n"; # will always output <r>	1894	warn "io event <$_[0]>\n"; # will always output <r>
961	chomp (my $input = <STDIN>); # read a line	1895	chomp (my $input = <STDIN>); # read a line
962	warn "read: $input\n"; # output what has been read	1896	warn "read: $input\n"; # output what has been read
963	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	1897	$cv->send if $input =~ /^q/i; # quit program if /^q/i
964	},	1898	},
965	);	1899	);
966		1900
967	my $time_watcher; # can only be used once	1901	my $time_watcher; # can only be used once
968		1902
…		…
973	});	1907	});
974	}	1908	}
975		1909
976	new_timer; # create first timer	1910	new_timer; # create first timer
977		1911
978	$cv->wait; # wait until user enters /^q/i	1912	$cv->recv; # wait until user enters /^q/i
979		1913
980	=head1 REAL-WORLD EXAMPLE	1914	=head1 REAL-WORLD EXAMPLE
981		1915
982	Consider the L<Net::FCP> module. It features (among others) the following	1916	Consider the L<Net::FCP> module. It features (among others) the following
983	API calls, which are to freenet what HTTP GET requests are to http:	1917	API calls, which are to freenet what HTTP GET requests are to http:
…		…
1033	syswrite $txn->{fh}, $txn->{request}	1967	syswrite $txn->{fh}, $txn->{request}
1034	or die "connection or write error";	1968	or die "connection or write error";
1035	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	1969	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
1036		1970
1037	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	1971	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
1038	result and signals any possible waiters that the request ahs finished:	1972	result and signals any possible waiters that the request has finished:
1039		1973
1040	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	1974	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
1041		1975
1042	if (end-of-file or data complete) {	1976	if (end-of-file or data complete) {
1043	$txn->{result} = $txn->{buf};	1977	$txn->{result} = $txn->{buf};
1044	$txn->{finished}->broadcast;	1978	$txn->{finished}->send;
1045	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	1979	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
1046	}	1980	}
1047		1981
1048	The C<result> method, finally, just waits for the finished signal (if the	1982	The C<result> method, finally, just waits for the finished signal (if the
1049	request was already finished, it doesn't wait, of course, and returns the	1983	request was already finished, it doesn't wait, of course, and returns the
1050	data:	1984	data:
1051		1985
1052	$txn->{finished}->wait;	1986	$txn->{finished}->recv;
1053	return $txn->{result};	1987	return $txn->{result};
1054		1988
1055	The actual code goes further and collects all errors (C<die>s, exceptions)	1989	The actual code goes further and collects all errors (C<die>s, exceptions)
1056	that occured during request processing. The C<result> method detects	1990	that occurred during request processing. The C<result> method detects
1057	whether an exception as thrown (it is stored inside the $txn object)	1991	whether an exception as thrown (it is stored inside the $txn object)
1058	and just throws the exception, which means connection errors and other	1992	and just throws the exception, which means connection errors and other
1059	problems get reported tot he code that tries to use the result, not in a	1993	problems get reported tot he code that tries to use the result, not in a
1060	random callback.	1994	random callback.
1061		1995
…		…
1092		2026
1093	my $quit = AnyEvent->condvar;	2027	my $quit = AnyEvent->condvar;
1094		2028
1095	$fcp->txn_client_get ($url)->cb (sub {	2029	$fcp->txn_client_get ($url)->cb (sub {
1096	...	2030	...
1097	$quit->broadcast;	2031	$quit->send;
1098	});	2032	});
1099		2033
1100	$quit->wait;	2034	$quit->recv;
1101		2035
1102		2036
1103	=head1 BENCHMARKS	2037	=head1 BENCHMARKS
1104		2038
1105	To give you an idea of the performance and overheads that AnyEvent adds	2039	To give you an idea of the performance and overheads that AnyEvent adds
…		…
1107	of various event loops I prepared some benchmarks.	2041	of various event loops I prepared some benchmarks.
1108		2042
1109	=head2 BENCHMARKING ANYEVENT OVERHEAD	2043	=head2 BENCHMARKING ANYEVENT OVERHEAD
1110		2044
1111	Here is a benchmark of various supported event models used natively and	2045	Here is a benchmark of various supported event models used natively and
1112	through anyevent. The benchmark creates a lot of timers (with a zero	2046	through AnyEvent. The benchmark creates a lot of timers (with a zero
1113	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,	2047	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
1114	which it is), lets them fire exactly once and destroys them again.	2048	which it is), lets them fire exactly once and destroys them again.
1115		2049
1116	Source code for this benchmark is found as F<eg/bench> in the AnyEvent	2050	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
1117	distribution.	2051	distribution.
…		…
1134	all watchers, to avoid adding memory overhead. That means closure creation	2068	all watchers, to avoid adding memory overhead. That means closure creation
1135	and memory usage is not included in the figures.	2069	and memory usage is not included in the figures.
1136		2070
1137	I<invoke> is the time, in microseconds, used to invoke a simple	2071	I<invoke> is the time, in microseconds, used to invoke a simple
1138	callback. The callback simply counts down a Perl variable and after it was	2072	callback. The callback simply counts down a Perl variable and after it was
1139	invoked "watcher" times, it would C<< ->broadcast >> a condvar once to	2073	invoked "watcher" times, it would C<< ->send >> a condvar once to
1140	signal the end of this phase.	2074	signal the end of this phase.
1141		2075
1142	I<destroy> is the time, in microseconds, that it takes to destroy a single	2076	I<destroy> is the time, in microseconds, that it takes to destroy a single
1143	watcher.	2077	watcher.
1144		2078
1145	=head3 Results	2079	=head3 Results
1146		2080
1147	name watchers bytes create invoke destroy comment	2081	name watchers bytes create invoke destroy comment
1148	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	2082	EV/EV 400000 224 0.47 0.35 0.27 EV native interface
1149	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	2083	EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers
1150	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	2084	CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal
1151	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	2085	Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation
1152	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	2086	Event/Event 16000 517 32.20 31.80 0.81 Event native interface
1153	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers	2087	Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers
		2088	IOAsync/Any 16000 989 38.10 32.77 11.13 via IO::Async::Loop::IO_Poll
		2089	IOAsync/Any 16000 990 37.59 29.50 10.61 via IO::Async::Loop::Epoll
1154	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	2090	Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour
1155	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	2091	Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers
1156	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	2092	POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event
1157	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	2093	POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select
1158		2094
1159	=head3 Discussion	2095	=head3 Discussion
1160		2096
1161	The benchmark does I<not> measure scalability of the event loop very	2097	The benchmark does I<not> measure scalability of the event loop very
1162	well. For example, a select-based event loop (such as the pure perl one)	2098	well. For example, a select-based event loop (such as the pure perl one)
…		…
1187	performance becomes really bad with lots of file descriptors (and few of	2123	performance becomes really bad with lots of file descriptors (and few of
1188	them active), of course, but this was not subject of this benchmark.	2124	them active), of course, but this was not subject of this benchmark.
1189		2125
1190	The C<Event> module has a relatively high setup and callback invocation	2126	The C<Event> module has a relatively high setup and callback invocation
1191	cost, but overall scores in on the third place.	2127	cost, but overall scores in on the third place.
		2128
		2129	C<IO::Async> performs admirably well, about on par with C<Event>, even
		2130	when using its pure perl backend.
1192		2131
1193	C<Glib>'s memory usage is quite a bit higher, but it features a	2132	C<Glib>'s memory usage is quite a bit higher, but it features a
1194	faster callback invocation and overall ends up in the same class as	2133	faster callback invocation and overall ends up in the same class as
1195	C<Event>. However, Glib scales extremely badly, doubling the number of	2134	C<Event>. However, Glib scales extremely badly, doubling the number of
1196	watchers increases the processing time by more than a factor of four,	2135	watchers increases the processing time by more than a factor of four,
…		…
1240		2179
1241	=back	2180	=back
1242		2181
1243	=head2 BENCHMARKING THE LARGE SERVER CASE	2182	=head2 BENCHMARKING THE LARGE SERVER CASE
1244		2183
1245	This benchmark atcually benchmarks the event loop itself. It works by	2184	This benchmark actually benchmarks the event loop itself. It works by
1246	creating a number of "servers": each server consists of a socketpair, a	2185	creating a number of "servers": each server consists of a socket pair, a
1247	timeout watcher that gets reset on activity (but never fires), and an I/O	2186	timeout watcher that gets reset on activity (but never fires), and an I/O
1248	watcher waiting for input on one side of the socket. Each time the socket	2187	watcher waiting for input on one side of the socket. Each time the socket
1249	watcher reads a byte it will write that byte to a random other "server".	2188	watcher reads a byte it will write that byte to a random other "server".
1250		2189
1251	The effect is that there will be a lot of I/O watchers, only part of which	2190	The effect is that there will be a lot of I/O watchers, only part of which
1252	are active at any one point (so there is a constant number of active	2191	are active at any one point (so there is a constant number of active
1253	fds for each loop iterstaion, but which fds these are is random). The	2192	fds for each loop iteration, but which fds these are is random). The
1254	timeout is reset each time something is read because that reflects how	2193	timeout is reset each time something is read because that reflects how
1255	most timeouts work (and puts extra pressure on the event loops).	2194	most timeouts work (and puts extra pressure on the event loops).
1256		2195
1257	In this benchmark, we use 10000 socketpairs (20000 sockets), of which 100	2196	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
1258	(1%) are active. This mirrors the activity of large servers with many	2197	(1%) are active. This mirrors the activity of large servers with many
1259	connections, most of which are idle at any one point in time.	2198	connections, most of which are idle at any one point in time.
1260		2199
1261	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent	2200	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
1262	distribution.	2201	distribution.
…		…
1264	=head3 Explanation of the columns	2203	=head3 Explanation of the columns
1265		2204
1266	I<sockets> is the number of sockets, and twice the number of "servers" (as	2205	I<sockets> is the number of sockets, and twice the number of "servers" (as
1267	each server has a read and write socket end).	2206	each server has a read and write socket end).
1268		2207
1269	I<create> is the time it takes to create a socketpair (which is	2208	I<create> is the time it takes to create a socket pair (which is
1270	nontrivial) and two watchers: an I/O watcher and a timeout watcher.	2209	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
1271		2210
1272	I<request>, the most important value, is the time it takes to handle a	2211	I<request>, the most important value, is the time it takes to handle a
1273	single "request", that is, reading the token from the pipe and forwarding	2212	single "request", that is, reading the token from the pipe and forwarding
1274	it to another server. This includes deleting the old timeout and creating	2213	it to another server. This includes deleting the old timeout and creating
1275	a new one that moves the timeout into the future.	2214	a new one that moves the timeout into the future.
1276		2215
1277	=head3 Results	2216	=head3 Results
1278		2217
1279	name sockets create request	2218	name sockets create request
1280	EV 20000 69.01 11.16	2219	EV 20000 69.01 11.16
1281	Perl 20000 73.32 35.87	2220	Perl 20000 73.32 35.87
		2221	IOAsync 20000 157.00 98.14 epoll
		2222	IOAsync 20000 159.31 616.06 poll
1282	Event 20000 212.62 257.32	2223	Event 20000 212.62 257.32
1283	Glib 20000 651.16 1896.30	2224	Glib 20000 651.16 1896.30
1284	POE 20000 349.67 12317.24 uses POE::Loop::Event	2225	POE 20000 349.67 12317.24 uses POE::Loop::Event
1285		2226
1286	=head3 Discussion	2227	=head3 Discussion
1287		2228
1288	This benchmark I<does> measure scalability and overall performance of the	2229	This benchmark I<does> measure scalability and overall performance of the
1289	particular event loop.	2230	particular event loop.
…		…
1291	EV is again fastest. Since it is using epoll on my system, the setup time	2232	EV is again fastest. Since it is using epoll on my system, the setup time
1292	is relatively high, though.	2233	is relatively high, though.
1293		2234
1294	Perl surprisingly comes second. It is much faster than the C-based event	2235	Perl surprisingly comes second. It is much faster than the C-based event
1295	loops Event and Glib.	2236	loops Event and Glib.
		2237
		2238	IO::Async performs very well when using its epoll backend, and still quite
		2239	good compared to Glib when using its pure perl backend.
1296		2240
1297	Event suffers from high setup time as well (look at its code and you will	2241	Event suffers from high setup time as well (look at its code and you will
1298	understand why). Callback invocation also has a high overhead compared to	2242	understand why). Callback invocation also has a high overhead compared to
1299	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event	2243	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
1300	uses select or poll in basically all documented configurations.	2244	uses select or poll in basically all documented configurations.
…		…
1347	speed most when you have lots of watchers, not when you only have a few of	2291	speed most when you have lots of watchers, not when you only have a few of
1348	them).	2292	them).
1349		2293
1350	EV is again fastest.	2294	EV is again fastest.
1351		2295
1352	Perl again comes second. It is noticably faster than the C-based event	2296	Perl again comes second. It is noticeably faster than the C-based event
1353	loops Event and Glib, although the difference is too small to really	2297	loops Event and Glib, although the difference is too small to really
1354	matter.	2298	matter.
1355		2299
1356	POE also performs much better in this case, but is is still far behind the	2300	POE also performs much better in this case, but is is still far behind the
1357	others.	2301	others.
…		…
1360		2304
1361	=over 4	2305	=over 4
1362		2306
1363	=item * C-based event loops perform very well with small number of	2307	=item * C-based event loops perform very well with small number of
1364	watchers, as the management overhead dominates.	2308	watchers, as the management overhead dominates.
		2309
		2310	=back
		2311
		2312	=head2 THE IO::Lambda BENCHMARK
		2313
		2314	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2315	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2316	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2317	shouldn't come as a surprise to anybody). As such, the benchmark is
		2318	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2319	very optimal. But how would AnyEvent compare when used without the extra
		2320	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2321
		2322	The benchmark itself creates an echo-server, and then, for 500 times,
		2323	connects to the echo server, sends a line, waits for the reply, and then
		2324	creates the next connection. This is a rather bad benchmark, as it doesn't
		2325	test the efficiency of the framework or much non-blocking I/O, but it is a
		2326	benchmark nevertheless.
		2327
		2328	name runtime
		2329	Lambda/select 0.330 sec
		2330	+ optimized 0.122 sec
		2331	Lambda/AnyEvent 0.327 sec
		2332	+ optimized 0.138 sec
		2333	Raw sockets/select 0.077 sec
		2334	POE/select, components 0.662 sec
		2335	POE/select, raw sockets 0.226 sec
		2336	POE/select, optimized 0.404 sec
		2337
		2338	AnyEvent/select/nb 0.085 sec
		2339	AnyEvent/EV/nb 0.068 sec
		2340	+state machine 0.134 sec
		2341
		2342	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2343	benchmarks actually make blocking connects and use 100% blocking I/O,
		2344	defeating the purpose of an event-based solution. All of the newly
		2345	written AnyEvent benchmarks use 100% non-blocking connects (using
		2346	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2347	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2348	generally require a lot more bookkeeping and event handling than blocking
		2349	connects (which involve a single syscall only).
		2350
		2351	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2352	offers similar expressive power as POE and IO::Lambda, using conventional
		2353	Perl syntax. This means that both the echo server and the client are 100%
		2354	non-blocking, further placing it at a disadvantage.
		2355
		2356	As you can see, the AnyEvent + EV combination even beats the
		2357	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2358	backend easily beats IO::Lambda and POE.
		2359
		2360	And even the 100% non-blocking version written using the high-level (and
		2361	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda by a
		2362	large margin, even though it does all of DNS, tcp-connect and socket I/O
		2363	in a non-blocking way.
		2364
		2365	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2366	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2367	part of the IO::lambda distribution and were used without any changes.
		2368
		2369
		2370	=head1 SIGNALS
		2371
		2372	AnyEvent currently installs handlers for these signals:
		2373
		2374	=over 4
		2375
		2376	=item SIGCHLD
		2377
		2378	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2379	emulation for event loops that do not support them natively. Also, some
		2380	event loops install a similar handler.
		2381
		2382	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2383	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2384
		2385	=item SIGPIPE
		2386
		2387	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2388	when AnyEvent gets loaded.
		2389
		2390	The rationale for this is that AnyEvent users usually do not really depend
		2391	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2392	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2393	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2394	some random socket.
		2395
		2396	The rationale for installing a no-op handler as opposed to ignoring it is
		2397	that this way, the handler will be restored to defaults on exec.
		2398
		2399	Feel free to install your own handler, or reset it to defaults.
		2400
		2401	=back
		2402
		2403	=cut
		2404
		2405	undef $SIG{CHLD}
		2406	if $SIG{CHLD} eq 'IGNORE';
		2407
		2408	$SIG{PIPE} = sub { }
		2409	unless defined $SIG{PIPE};
		2410
		2411	=head1 RECOMMENDED/OPTIONAL MODULES
		2412
		2413	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2414	it's built-in modules) are required to use it.
		2415
		2416	That does not mean that AnyEvent won't take advantage of some additional
		2417	modules if they are installed.
		2418
		2419	This section epxlains which additional modules will be used, and how they
		2420	affect AnyEvent's operetion.
		2421
		2422	=over 4
		2423
		2424	=item L<Async::Interrupt>
		2425
		2426	This slightly arcane module is used to implement fast signal handling: To
		2427	my knowledge, there is no way to do completely race-free and quick
		2428	signal handling in pure perl. To ensure that signals still get
		2429	delivered, AnyEvent will start an interval timer to wake up perl (and
		2430	catch the signals) with some delay (default is 10 seconds, look for
		2431	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2432
		2433	If this module is available, then it will be used to implement signal
		2434	catching, which means that signals will not be delayed, and the event loop
		2435	will not be interrupted regularly, which is more efficient (And good for
		2436	battery life on laptops).
		2437
		2438	This affects not just the pure-perl event loop, but also other event loops
		2439	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2440
		2441	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2442	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2443	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2444	does nothing for those backends.
		2445
		2446	=item L<EV>
		2447
		2448	This module isn't really "optional", as it is simply one of the backend
		2449	event loops that AnyEvent can use. However, it is simply the best event
		2450	loop available in terms of features, speed and stability: It supports
		2451	the AnyEvent API optimally, implements all the watcher types in XS, does
		2452	automatic timer adjustments even when no monotonic clock is available,
		2453	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2454	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2455	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2456
		2457	=item L<Guard>
		2458
		2459	The guard module, when used, will be used to implement
		2460	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2461	lot less memory), but otherwise doesn't affect guard operation much. It is
		2462	purely used for performance.
		2463
		2464	=item L<JSON> and L<JSON::XS>
		2465
		2466	This module is required when you want to read or write JSON data via
		2467	L<AnyEvent::Handle>. It is also written in pure-perl, but can take
		2468	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2469
		2470	In fact, L<AnyEvent::Handle> will use L<JSON::XS> by default if it is
		2471	installed.
		2472
		2473	=item L<Net::SSLeay>
		2474
		2475	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2476	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2477	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2478
		2479	=item L<Time::HiRes>
		2480
		2481	This module is part of perl since release 5.008. It will be used when the
		2482	chosen event library does not come with a timing source on it's own. The
		2483	pure-perl event loop (L<AnyEvent::Impl::Perl>) will additionally use it to
		2484	try to use a monotonic clock for timing stability.
1365		2485
1366	=back	2486	=back
1367		2487
1368		2488
1369	=head1 FORK	2489	=head1 FORK
…		…
1371	Most event libraries are not fork-safe. The ones who are usually are	2491	Most event libraries are not fork-safe. The ones who are usually are
1372	because they rely on inefficient but fork-safe C<select> or C<poll>	2492	because they rely on inefficient but fork-safe C<select> or C<poll>
1373	calls. Only L<EV> is fully fork-aware.	2493	calls. Only L<EV> is fully fork-aware.
1374		2494
1375	If you have to fork, you must either do so I<before> creating your first	2495	If you have to fork, you must either do so I<before> creating your first
1376	watcher OR you must not use AnyEvent at all in the child.	2496	watcher OR you must not use AnyEvent at all in the child OR you must do
		2497	something completely out of the scope of AnyEvent.
1377		2498
1378		2499
1379	=head1 SECURITY CONSIDERATIONS	2500	=head1 SECURITY CONSIDERATIONS
1380		2501
1381	AnyEvent can be forced to load any event model via	2502	AnyEvent can be forced to load any event model via
…		…
1386	specified in the variable.	2507	specified in the variable.
1387		2508
1388	You can make AnyEvent completely ignore this variable by deleting it	2509	You can make AnyEvent completely ignore this variable by deleting it
1389	before the first watcher gets created, e.g. with a C<BEGIN> block:	2510	before the first watcher gets created, e.g. with a C<BEGIN> block:
1390		2511
1391	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	2512	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1392		2513
1393	use AnyEvent;	2514	use AnyEvent;
		2515
		2516	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		2517	be used to probe what backend is used and gain other information (which is
		2518	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2519	$ENV{PERL_ANYEVENT_STRICT}.
		2520
		2521	Note that AnyEvent will remove I<all> environment variables starting with
		2522	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2523	enabled.
		2524
		2525
		2526	=head1 BUGS
		2527
		2528	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2529	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2530	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2531	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2532	pronounced).
1394		2533
1395		2534
1396	=head1 SEE ALSO	2535	=head1 SEE ALSO
1397		2536
1398	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	2537	Utility functions: L<AnyEvent::Util>.
1399	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,	2538
		2539	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
1400	L<Event::Lib>, L<Qt>, L<POE>.	2540	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
1401		2541
1402	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	2542	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
		2543	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
		2544	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1403	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,	2545	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>, L<Anyevent::Impl::Irssi>.
1404	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,
1405	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.
1406		2546
		2547	Non-blocking file handles, sockets, TCP clients and
		2548	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
		2549
		2550	Asynchronous DNS: L<AnyEvent::DNS>.
		2551
		2552	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>,
		2553	L<Coro::Event>,
		2554
1407	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	2555	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::XMPP>,
		2556	L<AnyEvent::HTTP>.
1408		2557
1409		2558
1410	=head1 AUTHOR	2559	=head1 AUTHOR
1411		2560
1412	Marc Lehmann <schmorp@schmorp.de>	2561	Marc Lehmann <schmorp@schmorp.de>
1413	http://home.schmorp.de/	2562	http://home.schmorp.de/
1414		2563
1415	=cut	2564	=cut
1416		2565
1417	1	2566	1
1418		2567

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