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Revision 1.332 by root, Tue Aug 31 23:32:40 2010 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, 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	# if you prefer function calls, look at the AE manpage for
		13	# an alternative API.
		14
		15	# file handle or descriptor readable
11	my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub {	16	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
		17
		18	# one-shot or repeating timers
		19	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
		20	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...);
		21
		22	print AnyEvent->now; # prints current event loop time
		23	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
		24
		25	# POSIX signal
		26	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
		27
		28	# child process exit
		29	my $w = AnyEvent->child (pid => $pid, cb => sub {
		30	my ($pid, $status) = @_;
12	...	31	...
13	});	32	});
14		33
15	my $w = AnyEvent->timer (after => $seconds, cb => sub {	34	# called when event loop idle (if applicable)
16	...	35	my $w = AnyEvent->idle (cb => sub { ... });
17	});
18		36
19	my $w = AnyEvent->condvar; # stores whether a condition was flagged	37	my $w = AnyEvent->condvar; # stores whether a condition was flagged
20	$w->send; # wake up current and all future recv's	38	$w->send; # wake up current and all future recv's
21	$w->recv; # enters "main loop" till $condvar gets ->send	39	$w->recv; # enters "main loop" till $condvar gets ->send
		40	# use a condvar in callback mode:
		41	$w->cb (sub { $_[0]->recv });
22		42
23	=head1 INTRODUCTION/TUTORIAL	43	=head1 INTRODUCTION/TUTORIAL
24		44
25	This manpage is mainly a reference manual. If you are interested	45	This manpage is mainly a reference manual. If you are interested
26	in a tutorial or some gentle introduction, have a look at the	46	in a tutorial or some gentle introduction, have a look at the
27	L<AnyEvent::Intro> manpage.	47	L<AnyEvent::Intro> manpage.
28		48
		49	=head1 SUPPORT
		50
		51	There is a mailinglist for discussing all things AnyEvent, and an IRC
		52	channel, too.
		53
		54	See the AnyEvent project page at the B<Schmorpforge Ta-Sa Software
		55	Repository>, at L<http://anyevent.schmorp.de>, for more info.
		56
29	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)	57	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
30		58
31	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	59	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
32	nowadays. So what is different about AnyEvent?	60	nowadays. So what is different about AnyEvent?
33		61
34	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of	62	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
35	policy> and AnyEvent is I<small and efficient>.	63	policy> and AnyEvent is I<small and efficient>.
36		64
37	First and foremost, I<AnyEvent is not an event model> itself, it only	65	First and foremost, I<AnyEvent is not an event model> itself, it only
38	interfaces to whatever event model the main program happens to use in a	66	interfaces to whatever event model the main program happens to use, in a
39	pragmatic way. For event models and certain classes of immortals alike,	67	pragmatic way. For event models and certain classes of immortals alike,
40	the statement "there can only be one" is a bitter reality: In general,	68	the statement "there can only be one" is a bitter reality: In general,
41	only one event loop can be active at the same time in a process. AnyEvent	69	only one event loop can be active at the same time in a process. AnyEvent
42	helps hiding the differences between those event loops.	70	cannot change this, but it can hide the differences between those event
		71	loops.
43		72
44	The goal of AnyEvent is to offer module authors the ability to do event	73	The goal of AnyEvent is to offer module authors the ability to do event
45	programming (waiting for I/O or timer events) without subscribing to a	74	programming (waiting for I/O or timer events) without subscribing to a
46	religion, a way of living, and most importantly: without forcing your	75	religion, a way of living, and most importantly: without forcing your
47	module users into the same thing by forcing them to use the same event	76	module users into the same thing by forcing them to use the same event
48	model you use.	77	model you use.
49		78
50	For modules like POE or IO::Async (which is a total misnomer as it is	79	For modules like POE or IO::Async (which is a total misnomer as it is
51	actually doing all I/O I<synchronously>...), using them in your module is	80	actually doing all I/O I<synchronously>...), using them in your module is
52	like joining a cult: After you joined, you are dependent on them and you	81	like joining a cult: After you join, you are dependent on them and you
53	cannot use anything else, as it is simply incompatible to everything that	82	cannot use anything else, as they are simply incompatible to everything
54	isn't itself. What's worse, all the potential users of your module are	83	that isn't them. What's worse, all the potential users of your
55	I<also> forced to use the same event loop you use.	84	module are I<also> forced to use the same event loop you use.
56		85
57	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	86	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
58	fine. AnyEvent + Tk works fine etc. etc. but none of these work together	87	fine. AnyEvent + Tk works fine etc. etc. but none of these work together
59	with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if	88	with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if
60	your module uses one of those, every user of your module has to use it,	89	your module uses one of those, every user of your module has to use it,
61	too. But if your module uses AnyEvent, it works transparently with all	90	too. But if your module uses AnyEvent, it works transparently with all
62	event models it supports (including stuff like POE and IO::Async, as long	91	event models it supports (including stuff like IO::Async, as long as those
63	as those use one of the supported event loops. It is trivial to add new	92	use one of the supported event loops. It is easy to add new event loops
64	event loops to AnyEvent, too, so it is future-proof).	93	to AnyEvent, too, so it is future-proof).
65		94
66	In addition to being free of having to use I<the one and only true event	95	In addition to being free of having to use I<the one and only true event
67	model>, AnyEvent also is free of bloat and policy: with POE or similar	96	model>, AnyEvent also is free of bloat and policy: with POE or similar
68	modules, you get an enormous amount of code and strict rules you have to	97	modules, you get an enormous amount of code and strict rules you have to
69	follow. AnyEvent, on the other hand, is lean and up to the point, by only	98	follow. AnyEvent, on the other hand, is lean and to the point, by only
70	offering the functionality that is necessary, in as thin as a wrapper as	99	offering the functionality that is necessary, in as thin as a wrapper as
71	technically possible.	100	technically possible.
72		101
73	Of course, AnyEvent comes with a big (and fully optional!) toolbox	102	Of course, AnyEvent comes with a big (and fully optional!) toolbox
74	of useful functionality, such as an asynchronous DNS resolver, 100%	103	of useful functionality, such as an asynchronous DNS resolver, 100%
…		…
80	useful) and you want to force your users to use the one and only event	109	useful) and you want to force your users to use the one and only event
81	model, you should I<not> use this module.	110	model, you should I<not> use this module.
82		111
83	=head1 DESCRIPTION	112	=head1 DESCRIPTION
84		113
85	L<AnyEvent> provides an identical interface to multiple event loops. This	114	L<AnyEvent> provides a uniform interface to various event loops. This
86	allows module authors to utilise an event loop without forcing module	115	allows module authors to use event loop functionality without forcing
87	users to use the same event loop (as only a single event loop can coexist	116	module users to use a specific event loop implementation (since more
88	peacefully at any one time).	117	than one event loop cannot coexist peacefully).
89		118
90	The interface itself is vaguely similar, but not identical to the L<Event>	119	The interface itself is vaguely similar, but not identical to the L<Event>
91	module.	120	module.
92		121
93	During the first call of any watcher-creation method, the module tries	122	During the first call of any watcher-creation method, the module tries
94	to detect the currently loaded event loop by probing whether one of the	123	to detect the currently loaded event loop by probing whether one of the
95	following modules is already loaded: L<EV>,	124	following modules is already loaded: L<EV>, L<AnyEvent::Impl::Perl>,
96	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,	125	L<Event>, L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>. The first one
97	L<POE>. The first one found is used. If none are found, the module tries	126	found is used. If none are detected, the module tries to load the first
98	to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl	127	four modules in the order given; but note that if L<EV> is not
99	adaptor should always succeed) in the order given. The first one that can	128	available, the pure-perl L<AnyEvent::Impl::Perl> should always work, so
100	be successfully loaded will be used. If, after this, still none could be	129	the other two are not normally tried.
101	found, AnyEvent will fall back to a pure-perl event loop, which is not
102	very efficient, but should work everywhere.
103		130
104	Because AnyEvent first checks for modules that are already loaded, loading	131	Because AnyEvent first checks for modules that are already loaded, loading
105	an event model explicitly before first using AnyEvent will likely make	132	an event model explicitly before first using AnyEvent will likely make
106	that model the default. For example:	133	that model the default. For example:
107		134
…		…
109	use AnyEvent;	136	use AnyEvent;
110		137
111	# .. AnyEvent will likely default to Tk	138	# .. AnyEvent will likely default to Tk
112		139
113	The I<likely> means that, if any module loads another event model and	140	The I<likely> means that, if any module loads another event model and
114	starts using it, all bets are off. Maybe you should tell their authors to	141	starts using it, all bets are off - this case should be very rare though,
115	use AnyEvent so their modules work together with others seamlessly...	142	as very few modules hardcode event loops without announcing this very
		143	loudly.
116		144
117	The pure-perl implementation of AnyEvent is called	145	The pure-perl implementation of AnyEvent is called
118	C<AnyEvent::Impl::Perl>. Like other event modules you can load it	146	C<AnyEvent::Impl::Perl>. Like other event modules you can load it
119	explicitly and enjoy the high availability of that event loop :)	147	explicitly and enjoy the high availability of that event loop :)
120		148
…		…
127	These watchers are normal Perl objects with normal Perl lifetime. After	155	These watchers are normal Perl objects with normal Perl lifetime. After
128	creating a watcher it will immediately "watch" for events and invoke the	156	creating a watcher it will immediately "watch" for events and invoke the
129	callback when the event occurs (of course, only when the event model	157	callback when the event occurs (of course, only when the event model
130	is in control).	158	is in control).
131		159
		160	Note that B<callbacks must not permanently change global variables>
		161	potentially in use by the event loop (such as C<$_> or C<$[>) and that B<<
		162	callbacks must not C<die> >>. The former is good programming practice in
		163	Perl and the latter stems from the fact that exception handling differs
		164	widely between event loops.
		165
132	To disable the watcher you have to destroy it (e.g. by setting the	166	To disable a watcher you have to destroy it (e.g. by setting the
133	variable you store it in to C<undef> or otherwise deleting all references	167	variable you store it in to C<undef> or otherwise deleting all references
134	to it).	168	to it).
135		169
136	All watchers are created by calling a method on the C<AnyEvent> class.	170	All watchers are created by calling a method on the C<AnyEvent> class.
137		171
138	Many watchers either are used with "recursion" (repeating timers for	172	Many watchers either are used with "recursion" (repeating timers for
139	example), or need to refer to their watcher object in other ways.	173	example), or need to refer to their watcher object in other ways.
140		174
141	An any way to achieve that is this pattern:	175	One way to achieve that is this pattern:
142		176
143	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	177	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
144	# you can use $w here, for example to undef it	178	# you can use $w here, for example to undef it
145	undef $w;	179	undef $w;
146	});	180	});
…		…
149	my variables are only visible after the statement in which they are	183	my variables are only visible after the statement in which they are
150	declared.	184	declared.
151		185
152	=head2 I/O WATCHERS	186	=head2 I/O WATCHERS
153		187
		188	$w = AnyEvent->io (
		189	fh => <filehandle_or_fileno>,
		190	poll => <"r" or "w">,
		191	cb => <callback>,
		192	);
		193
154	You can create an I/O watcher by calling the C<< AnyEvent->io >> method	194	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
155	with the following mandatory key-value pairs as arguments:	195	with the following mandatory key-value pairs as arguments:
156		196
157	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch	197	C<fh> is the Perl I<file handle> (or a naked file descriptor) to watch
		198	for events (AnyEvent might or might not keep a reference to this file
		199	handle). Note that only file handles pointing to things for which
		200	non-blocking operation makes sense are allowed. This includes sockets,
		201	most character devices, pipes, fifos and so on, but not for example files
		202	or block devices.
		203
158	for events. C<poll> must be a string that is either C<r> or C<w>,	204	C<poll> must be a string that is either C<r> or C<w>, which creates a
159	which creates a watcher waiting for "r"eadable or "w"ritable events,	205	watcher waiting for "r"eadable or "w"ritable events, respectively.
		206
160	respectively. C<cb> is the callback to invoke each time the file handle	207	C<cb> is the callback to invoke each time the file handle becomes ready.
161	becomes ready.
162		208
163	Although the callback might get passed parameters, their value and	209	Although the callback might get passed parameters, their value and
164	presence is undefined and you cannot rely on them. Portable AnyEvent	210	presence is undefined and you cannot rely on them. Portable AnyEvent
165	callbacks cannot use arguments passed to I/O watcher callbacks.	211	callbacks cannot use arguments passed to I/O watcher callbacks.
166		212
167	The I/O watcher might use the underlying file descriptor or a copy of it.	213	The I/O watcher might use the underlying file descriptor or a copy of it.
168	You must not close a file handle as long as any watcher is active on the	214	You must not close a file handle as long as any watcher is active on the
169	underlying file descriptor.	215	underlying file descriptor.
170		216
171	Some event loops issue spurious readyness notifications, so you should	217	Some event loops issue spurious readiness notifications, so you should
172	always use non-blocking calls when reading/writing from/to your file	218	always use non-blocking calls when reading/writing from/to your file
173	handles.	219	handles.
174		220
175	Example:
176
177	# wait for readability of STDIN, then read a line and disable the watcher	221	Example: wait for readability of STDIN, then read a line and disable the
		222	watcher.
		223
178	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	224	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
179	chomp (my $input = <STDIN>);	225	chomp (my $input = <STDIN>);
180	warn "read: $input\n";	226	warn "read: $input\n";
181	undef $w;	227	undef $w;
182	});	228	});
183		229
184	=head2 TIME WATCHERS	230	=head2 TIME WATCHERS
185		231
		232	$w = AnyEvent->timer (after => <seconds>, cb => <callback>);
		233
		234	$w = AnyEvent->timer (
		235	after => <fractional_seconds>,
		236	interval => <fractional_seconds>,
		237	cb => <callback>,
		238	);
		239
186	You can create a time watcher by calling the C<< AnyEvent->timer >>	240	You can create a time watcher by calling the C<< AnyEvent->timer >>
187	method with the following mandatory arguments:	241	method with the following mandatory arguments:
188		242
189	C<after> specifies after how many seconds (fractional values are	243	C<after> specifies after how many seconds (fractional values are
190	supported) the callback should be invoked. C<cb> is the callback to invoke	244	supported) the callback should be invoked. C<cb> is the callback to invoke
…		…
192		246
193	Although the callback might get passed parameters, their value and	247	Although the callback might get passed parameters, their value and
194	presence is undefined and you cannot rely on them. Portable AnyEvent	248	presence is undefined and you cannot rely on them. Portable AnyEvent
195	callbacks cannot use arguments passed to time watcher callbacks.	249	callbacks cannot use arguments passed to time watcher callbacks.
196		250
197	The timer callback will be invoked at most once: if you want a repeating	251	The callback will normally be invoked only once. If you specify another
198	timer you have to create a new watcher (this is a limitation by both Tk	252	parameter, C<interval>, as a strictly positive number (> 0), then the
199	and Glib).	253	callback will be invoked regularly at that interval (in fractional
		254	seconds) after the first invocation. If C<interval> is specified with a
		255	false value, then it is treated as if it were not specified at all.
200		256
201	Example:	257	The callback will be rescheduled before invoking the callback, but no
		258	attempt is made to avoid timer drift in most backends, so the interval is
		259	only approximate.
202		260
203	# fire an event after 7.7 seconds	261	Example: fire an event after 7.7 seconds.
		262
204	my $w = AnyEvent->timer (after => 7.7, cb => sub {	263	my $w = AnyEvent->timer (after => 7.7, cb => sub {
205	warn "timeout\n";	264	warn "timeout\n";
206	});	265	});
207		266
208	# to cancel the timer:	267	# to cancel the timer:
209	undef $w;	268	undef $w;
210		269
211	Example 2:
212
213	# fire an event after 0.5 seconds, then roughly every second	270	Example 2: fire an event after 0.5 seconds, then roughly every second.
214	my $w;
215		271
216	my $cb = sub {
217	# cancel the old timer while creating a new one
218	$w = AnyEvent->timer (after => 1, cb => $cb);	272	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		273	warn "timeout\n";
219	};	274	};
220
221	# start the "loop" by creating the first watcher
222	$w = AnyEvent->timer (after => 0.5, cb => $cb);
223		275
224	=head3 TIMING ISSUES	276	=head3 TIMING ISSUES
225		277
226	There are two ways to handle timers: based on real time (relative, "fire	278	There are two ways to handle timers: based on real time (relative, "fire
227	in 10 seconds") and based on wallclock time (absolute, "fire at 12	279	in 10 seconds") and based on wallclock time (absolute, "fire at 12
…		…
229		281
230	While most event loops expect timers to specified in a relative way, they	282	While most event loops expect timers to specified in a relative way, they
231	use absolute time internally. This makes a difference when your clock	283	use absolute time internally. This makes a difference when your clock
232	"jumps", for example, when ntp decides to set your clock backwards from	284	"jumps", for example, when ntp decides to set your clock backwards from
233	the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to	285	the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to
234	fire "after" a second might actually take six years to finally fire.	286	fire "after a second" might actually take six years to finally fire.
235		287
236	AnyEvent cannot compensate for this. The only event loop that is conscious	288	AnyEvent cannot compensate for this. The only event loop that is conscious
237	about these issues is L<EV>, which offers both relative (ev_timer, based	289	of these issues is L<EV>, which offers both relative (ev_timer, based
238	on true relative time) and absolute (ev_periodic, based on wallclock time)	290	on true relative time) and absolute (ev_periodic, based on wallclock time)
239	timers.	291	timers.
240		292
241	AnyEvent always prefers relative timers, if available, matching the	293	AnyEvent always prefers relative timers, if available, matching the
242	AnyEvent API.	294	AnyEvent API.
…		…
264	I<In almost all cases (in all cases if you don't care), this is the	316	I<In almost all cases (in all cases if you don't care), this is the
265	function to call when you want to know the current time.>	317	function to call when you want to know the current time.>
266		318
267	This function is also often faster then C<< AnyEvent->time >>, and	319	This function is also often faster then C<< AnyEvent->time >>, and
268	thus the preferred method if you want some timestamp (for example,	320	thus the preferred method if you want some timestamp (for example,
269	L<AnyEvent::Handle> uses this to update it's activity timeouts).	321	L<AnyEvent::Handle> uses this to update its activity timeouts).
270		322
271	The rest of this section is only of relevance if you try to be very exact	323	The rest of this section is only of relevance if you try to be very exact
272	with your timing, you can skip it without bad conscience.	324	with your timing; you can skip it without a bad conscience.
273		325
274	For a practical example of when these times differ, consider L<Event::Lib>	326	For a practical example of when these times differ, consider L<Event::Lib>
275	and L<EV> and the following set-up:	327	and L<EV> and the following set-up:
276		328
277	The event loop is running and has just invoked one of your callback at	329	The event loop is running and has just invoked one of your callbacks at
278	time=500 (assume no other callbacks delay processing). In your callback,	330	time=500 (assume no other callbacks delay processing). In your callback,
279	you wait a second by executing C<sleep 1> (blocking the process for a	331	you wait a second by executing C<sleep 1> (blocking the process for a
280	second) and then (at time=501) you create a relative timer that fires	332	second) and then (at time=501) you create a relative timer that fires
281	after three seconds.	333	after three seconds.
282		334
…		…
300	In either case, if you care (and in most cases, you don't), then you	352	In either case, if you care (and in most cases, you don't), then you
301	can get whatever behaviour you want with any event loop, by taking the	353	can get whatever behaviour you want with any event loop, by taking the
302	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into	354	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
303	account.	355	account.
304		356
		357	=item AnyEvent->now_update
		358
		359	Some event loops (such as L<EV> or L<AnyEvent::Impl::Perl>) cache
		360	the current time for each loop iteration (see the discussion of L<<
		361	AnyEvent->now >>, above).
		362
		363	When a callback runs for a long time (or when the process sleeps), then
		364	this "current" time will differ substantially from the real time, which
		365	might affect timers and time-outs.
		366
		367	When this is the case, you can call this method, which will update the
		368	event loop's idea of "current time".
		369
		370	A typical example would be a script in a web server (e.g. C<mod_perl>) -
		371	when mod_perl executes the script, then the event loop will have the wrong
		372	idea about the "current time" (being potentially far in the past, when the
		373	script ran the last time). In that case you should arrange a call to C<<
		374	AnyEvent->now_update >> each time the web server process wakes up again
		375	(e.g. at the start of your script, or in a handler).
		376
		377	Note that updating the time I<might> cause some events to be handled.
		378
305	=back	379	=back
306		380
307	=head2 SIGNAL WATCHERS	381	=head2 SIGNAL WATCHERS
308		382
		383	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		384
309	You can watch for signals using a signal watcher, C<signal> is the signal	385	You can watch for signals using a signal watcher, C<signal> is the signal
310	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to	386	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
311	be invoked whenever a signal occurs.	387	callback to be invoked whenever a signal occurs.
312		388
313	Although the callback might get passed parameters, their value and	389	Although the callback might get passed parameters, their value and
314	presence is undefined and you cannot rely on them. Portable AnyEvent	390	presence is undefined and you cannot rely on them. Portable AnyEvent
315	callbacks cannot use arguments passed to signal watcher callbacks.	391	callbacks cannot use arguments passed to signal watcher callbacks.
316		392
…		…
318	invocation, and callback invocation will be synchronous. Synchronous means	394	invocation, and callback invocation will be synchronous. Synchronous means
319	that it might take a while until the signal gets handled by the process,	395	that it might take a while until the signal gets handled by the process,
320	but it is guaranteed not to interrupt any other callbacks.	396	but it is guaranteed not to interrupt any other callbacks.
321		397
322	The main advantage of using these watchers is that you can share a signal	398	The main advantage of using these watchers is that you can share a signal
323	between multiple watchers.	399	between multiple watchers, and AnyEvent will ensure that signals will not
		400	interrupt your program at bad times.
324		401
325	This watcher might use C<%SIG>, so programs overwriting those signals	402	This watcher might use C<%SIG> (depending on the event loop used),
326	directly will likely not work correctly.	403	so programs overwriting those signals directly will likely not work
		404	correctly.
327		405
328	Example: exit on SIGINT	406	Example: exit on SIGINT
329		407
330	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	408	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
331		409
		410	=head3 Restart Behaviour
		411
		412	While restart behaviour is up to the event loop implementation, most will
		413	not restart syscalls (that includes L<Async::Interrupt> and AnyEvent's
		414	pure perl implementation).
		415
		416	=head3 Safe/Unsafe Signals
		417
		418	Perl signals can be either "safe" (synchronous to opcode handling) or
		419	"unsafe" (asynchronous) - the former might get delayed indefinitely, the
		420	latter might corrupt your memory.
		421
		422	AnyEvent signal handlers are, in addition, synchronous to the event loop,
		423	i.e. they will not interrupt your running perl program but will only be
		424	called as part of the normal event handling (just like timer, I/O etc.
		425	callbacks, too).
		426
		427	=head3 Signal Races, Delays and Workarounds
		428
		429	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		430	callbacks to signals in a generic way, which is a pity, as you cannot
		431	do race-free signal handling in perl, requiring C libraries for
		432	this. AnyEvent will try to do its best, which means in some cases,
		433	signals will be delayed. The maximum time a signal might be delayed is
		434	specified in C<$AnyEvent::MAX_SIGNAL_LATENCY> (default: 10 seconds). This
		435	variable can be changed only before the first signal watcher is created,
		436	and should be left alone otherwise. This variable determines how often
		437	AnyEvent polls for signals (in case a wake-up was missed). Higher values
		438	will cause fewer spurious wake-ups, which is better for power and CPU
		439	saving.
		440
		441	All these problems can be avoided by installing the optional
		442	L<Async::Interrupt> module, which works with most event loops. It will not
		443	work with inherently broken event loops such as L<Event> or L<Event::Lib>
		444	(and not with L<POE> currently, as POE does its own workaround with
		445	one-second latency). For those, you just have to suffer the delays.
		446
332	=head2 CHILD PROCESS WATCHERS	447	=head2 CHILD PROCESS WATCHERS
333		448
		449	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		450
334	You can also watch on a child process exit and catch its exit status.	451	You can also watch for a child process exit and catch its exit status.
335		452
336	The child process is specified by the C<pid> argument (if set to C<0>, it	453	The child process is specified by the C<pid> argument (on some backends,
337	watches for any child process exit). The watcher will trigger as often	454	using C<0> watches for any child process exit, on others this will
338	as status change for the child are received. This works by installing a	455	croak). The watcher will be triggered only when the child process has
339	signal handler for C<SIGCHLD>. The callback will be called with the pid	456	finished and an exit status is available, not on any trace events
340	and exit status (as returned by waitpid), so unlike other watcher types,	457	(stopped/continued).
341	you I<can> rely on child watcher callback arguments.	458
		459	The callback will be called with the pid and exit status (as returned by
		460	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		461	callback arguments.
		462
		463	This watcher type works by installing a signal handler for C<SIGCHLD>,
		464	and since it cannot be shared, nothing else should use SIGCHLD or reap
		465	random child processes (waiting for specific child processes, e.g. inside
		466	C<system>, is just fine).
342		467
343	There is a slight catch to child watchers, however: you usually start them	468	There is a slight catch to child watchers, however: you usually start them
344	I<after> the child process was created, and this means the process could	469	I<after> the child process was created, and this means the process could
345	have exited already (and no SIGCHLD will be sent anymore).	470	have exited already (and no SIGCHLD will be sent anymore).
346		471
347	Not all event models handle this correctly (POE doesn't), but even for	472	Not all event models handle this correctly (neither POE nor IO::Async do,
		473	see their AnyEvent::Impl manpages for details), but even for event models
348	event models that I<do> handle this correctly, they usually need to be	474	that I<do> handle this correctly, they usually need to be loaded before
349	loaded before the process exits (i.e. before you fork in the first place).	475	the process exits (i.e. before you fork in the first place). AnyEvent's
		476	pure perl event loop handles all cases correctly regardless of when you
		477	start the watcher.
350		478
351	This means you cannot create a child watcher as the very first thing in an	479	This means you cannot create a child watcher as the very first
352	AnyEvent program, you I<have> to create at least one watcher before you	480	thing in an AnyEvent program, you I<have> to create at least one
353	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).	481	watcher before you C<fork> the child (alternatively, you can call
		482	C<AnyEvent::detect>).
		483
		484	As most event loops do not support waiting for child events, they will be
		485	emulated by AnyEvent in most cases, in which the latency and race problems
		486	mentioned in the description of signal watchers apply.
354		487
355	Example: fork a process and wait for it	488	Example: fork a process and wait for it
356		489
357	my $done = AnyEvent->condvar;	490	my $done = AnyEvent->condvar;
358		491
…		…
368	);	501	);
369		502
370	# do something else, then wait for process exit	503	# do something else, then wait for process exit
371	$done->recv;	504	$done->recv;
372		505
		506	=head2 IDLE WATCHERS
		507
		508	$w = AnyEvent->idle (cb => <callback>);
		509
		510	This will repeatedly invoke the callback after the process becomes idle,
		511	until either the watcher is destroyed or new events have been detected.
		512
		513	Idle watchers are useful when there is a need to do something, but it
		514	is not so important (or wise) to do it instantly. The callback will be
		515	invoked only when there is "nothing better to do", which is usually
		516	defined as "all outstanding events have been handled and no new events
		517	have been detected". That means that idle watchers ideally get invoked
		518	when the event loop has just polled for new events but none have been
		519	detected. Instead of blocking to wait for more events, the idle watchers
		520	will be invoked.
		521
		522	Unfortunately, most event loops do not really support idle watchers (only
		523	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		524	will simply call the callback "from time to time".
		525
		526	Example: read lines from STDIN, but only process them when the
		527	program is otherwise idle:
		528
		529	my @lines; # read data
		530	my $idle_w;
		531	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		532	push @lines, scalar <STDIN>;
		533
		534	# start an idle watcher, if not already done
		535	$idle_w ||= AnyEvent->idle (cb => sub {
		536	# handle only one line, when there are lines left
		537	if (my $line = shift @lines) {
		538	print "handled when idle: $line";
		539	} else {
		540	# otherwise disable the idle watcher again
		541	undef $idle_w;
		542	}
		543	});
		544	});
		545
373	=head2 CONDITION VARIABLES	546	=head2 CONDITION VARIABLES
		547
		548	$cv = AnyEvent->condvar;
		549
		550	$cv->send (<list>);
		551	my @res = $cv->recv;
374		552
375	If you are familiar with some event loops you will know that all of them	553	If you are familiar with some event loops you will know that all of them
376	require you to run some blocking "loop", "run" or similar function that	554	require you to run some blocking "loop", "run" or similar function that
377	will actively watch for new events and call your callbacks.	555	will actively watch for new events and call your callbacks.
378		556
379	AnyEvent is different, it expects somebody else to run the event loop and	557	AnyEvent is slightly different: it expects somebody else to run the event
380	will only block when necessary (usually when told by the user).	558	loop and will only block when necessary (usually when told by the user).
381		559
382	The instrument to do that is called a "condition variable", so called	560	The tool to do that is called a "condition variable", so called because
383	because they represent a condition that must become true.	561	they represent a condition that must become true.
		562
		563	Now is probably a good time to look at the examples further below.
384		564
385	Condition variables can be created by calling the C<< AnyEvent->condvar	565	Condition variables can be created by calling the C<< AnyEvent->condvar
386	>> method, usually without arguments. The only argument pair allowed is	566	>> method, usually without arguments. The only argument pair allowed is
387	C<cb>, which specifies a callback to be called when the condition variable	567	C<cb>, which specifies a callback to be called when the condition variable
388	becomes true.	568	becomes true, with the condition variable as the first argument (but not
		569	the results).
389		570
390	After creation, the condition variable is "false" until it becomes "true"	571	After creation, the condition variable is "false" until it becomes "true"
391	by calling the C<send> method (or calling the condition variable as if it	572	by calling the C<send> method (or calling the condition variable as if it
392	were a callback, read about the caveats in the description for the C<<	573	were a callback, read about the caveats in the description for the C<<
393	->send >> method).	574	->send >> method).
394		575
395	Condition variables are similar to callbacks, except that you can	576	Since condition variables are the most complex part of the AnyEvent API, here are
396	optionally wait for them. They can also be called merge points - points	577	some different mental models of what they are - pick the ones you can connect to:
397	in time where multiple outstanding events have been processed. And yet	578
398	another way to call them is transactions - each condition variable can be	579	=over 4
399	used to represent a transaction, which finishes at some point and delivers	580
400	a result.	581	=item * Condition variables are like callbacks - you can call them (and pass them instead
		582	of callbacks). Unlike callbacks however, you can also wait for them to be called.
		583
		584	=item * Condition variables are signals - one side can emit or send them,
		585	the other side can wait for them, or install a handler that is called when
		586	the signal fires.
		587
		588	=item * Condition variables are like "Merge Points" - points in your program
		589	where you merge multiple independent results/control flows into one.
		590
		591	=item * Condition variables represent a transaction - functions that start
		592	some kind of transaction can return them, leaving the caller the choice
		593	between waiting in a blocking fashion, or setting a callback.
		594
		595	=item * Condition variables represent future values, or promises to deliver
		596	some result, long before the result is available.
		597
		598	=back
401		599
402	Condition variables are very useful to signal that something has finished,	600	Condition variables are very useful to signal that something has finished,
403	for example, if you write a module that does asynchronous http requests,	601	for example, if you write a module that does asynchronous http requests,
404	then a condition variable would be the ideal candidate to signal the	602	then a condition variable would be the ideal candidate to signal the
405	availability of results. The user can either act when the callback is	603	availability of results. The user can either act when the callback is
…		…
418		616
419	Condition variables are represented by hash refs in perl, and the keys	617	Condition variables are represented by hash refs in perl, and the keys
420	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing	618	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
421	easy (it is often useful to build your own transaction class on top of	619	easy (it is often useful to build your own transaction class on top of
422	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call	620	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
423	it's C<new> method in your own C<new> method.	621	its C<new> method in your own C<new> method.
424		622
425	There are two "sides" to a condition variable - the "producer side" which	623	There are two "sides" to a condition variable - the "producer side" which
426	eventually calls C<< -> send >>, and the "consumer side", which waits	624	eventually calls C<< -> send >>, and the "consumer side", which waits
427	for the send to occur.	625	for the send to occur.
428		626
429	Example: wait for a timer.	627	Example: wait for a timer.
430		628
431	# wait till the result is ready	629	# condition: "wait till the timer is fired"
432	my $result_ready = AnyEvent->condvar;	630	my $timer_fired = AnyEvent->condvar;
433		631
434	# do something such as adding a timer	632	# create the timer - we could wait for, say
435	# or socket watcher the calls $result_ready->send	633	# a handle becomign ready, or even an
436	# when the "result" is ready.	634	# AnyEvent::HTTP request to finish, but
437	# in this case, we simply use a timer:	635	# in this case, we simply use a timer:
438	my $w = AnyEvent->timer (	636	my $w = AnyEvent->timer (
439	after => 1,	637	after => 1,
440	cb => sub { $result_ready->send },	638	cb => sub { $timer_fired->send },
441	);	639	);
442		640
443	# this "blocks" (while handling events) till the callback	641	# this "blocks" (while handling events) till the callback
444	# calls send	642	# calls ->send
445	$result_ready->recv;	643	$timer_fired->recv;
446		644
447	Example: wait for a timer, but take advantage of the fact that	645	Example: wait for a timer, but take advantage of the fact that condition
448	condition variables are also code references.	646	variables are also callable directly.
449		647
450	my $done = AnyEvent->condvar;	648	my $done = AnyEvent->condvar;
451	my $delay = AnyEvent->timer (after => 5, cb => $done);	649	my $delay = AnyEvent->timer (after => 5, cb => $done);
452	$done->recv;	650	$done->recv;
		651
		652	Example: Imagine an API that returns a condvar and doesn't support
		653	callbacks. This is how you make a synchronous call, for example from
		654	the main program:
		655
		656	use AnyEvent::CouchDB;
		657
		658	...
		659
		660	my @info = $couchdb->info->recv;
		661
		662	And this is how you would just set a callback to be called whenever the
		663	results are available:
		664
		665	$couchdb->info->cb (sub {
		666	my @info = $_[0]->recv;
		667	});
453		668
454	=head3 METHODS FOR PRODUCERS	669	=head3 METHODS FOR PRODUCERS
455		670
456	These methods should only be used by the producing side, i.e. the	671	These methods should only be used by the producing side, i.e. the
457	code/module that eventually sends the signal. Note that it is also	672	code/module that eventually sends the signal. Note that it is also
…		…
470	immediately from within send.	685	immediately from within send.
471		686
472	Any arguments passed to the C<send> call will be returned by all	687	Any arguments passed to the C<send> call will be returned by all
473	future C<< ->recv >> calls.	688	future C<< ->recv >> calls.
474		689
475	Condition variables are overloaded so one can call them directly	690	Condition variables are overloaded so one can call them directly (as if
476	(as a code reference). Calling them directly is the same as calling	691	they were a code reference). Calling them directly is the same as calling
477	C<send>. Note, however, that many C-based event loops do not handle	692	C<send>.
478	overloading, so as tempting as it may be, passing a condition variable
479	instead of a callback does not work. Both the pure perl and EV loops
480	support overloading, however, as well as all functions that use perl to
481	invoke a callback (as in L<AnyEvent::Socket> and L<AnyEvent::DNS> for
482	example).
483		693
484	=item $cv->croak ($error)	694	=item $cv->croak ($error)
485		695
486	Similar to send, but causes all call's to C<< ->recv >> to invoke	696	Similar to send, but causes all calls to C<< ->recv >> to invoke
487	C<Carp::croak> with the given error message/object/scalar.	697	C<Carp::croak> with the given error message/object/scalar.
488		698
489	This can be used to signal any errors to the condition variable	699	This can be used to signal any errors to the condition variable
490	user/consumer.	700	user/consumer. Doing it this way instead of calling C<croak> directly
		701	delays the error detection, but has the overwhelming advantage that it
		702	diagnoses the error at the place where the result is expected, and not
		703	deep in some event callback with no connection to the actual code causing
		704	the problem.
491		705
492	=item $cv->begin ([group callback])	706	=item $cv->begin ([group callback])
493		707
494	=item $cv->end	708	=item $cv->end
495
496	These two methods are EXPERIMENTAL and MIGHT CHANGE.
497		709
498	These two methods can be used to combine many transactions/events into	710	These two methods can be used to combine many transactions/events into
499	one. For example, a function that pings many hosts in parallel might want	711	one. For example, a function that pings many hosts in parallel might want
500	to use a condition variable for the whole process.	712	to use a condition variable for the whole process.
501		713
502	Every call to C<< ->begin >> will increment a counter, and every call to	714	Every call to C<< ->begin >> will increment a counter, and every call to
503	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end	715	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
504	>>, the (last) callback passed to C<begin> will be executed. That callback	716	>>, the (last) callback passed to C<begin> will be executed, passing the
505	is I<supposed> to call C<< ->send >>, but that is not required. If no	717	condvar as first argument. That callback is I<supposed> to call C<< ->send
506	callback was set, C<send> will be called without any arguments.	718	>>, but that is not required. If no group callback was set, C<send> will
		719	be called without any arguments.
507		720
508	Let's clarify this with the ping example:	721	You can think of C<< $cv->send >> giving you an OR condition (one call
		722	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		723	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		724
		725	Let's start with a simple example: you have two I/O watchers (for example,
		726	STDOUT and STDERR for a program), and you want to wait for both streams to
		727	close before activating a condvar:
509		728
510	my $cv = AnyEvent->condvar;	729	my $cv = AnyEvent->condvar;
511		730
		731	$cv->begin; # first watcher
		732	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		733	defined sysread $fh1, my $buf, 4096
		734	or $cv->end;
		735	});
		736
		737	$cv->begin; # second watcher
		738	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		739	defined sysread $fh2, my $buf, 4096
		740	or $cv->end;
		741	});
		742
		743	$cv->recv;
		744
		745	This works because for every event source (EOF on file handle), there is
		746	one call to C<begin>, so the condvar waits for all calls to C<end> before
		747	sending.
		748
		749	The ping example mentioned above is slightly more complicated, as the
		750	there are results to be passwd back, and the number of tasks that are
		751	begun can potentially be zero:
		752
		753	my $cv = AnyEvent->condvar;
		754
512	my %result;	755	my %result;
513	$cv->begin (sub { $cv->send (\%result) });	756	$cv->begin (sub { shift->send (\%result) });
514		757
515	for my $host (@list_of_hosts) {	758	for my $host (@list_of_hosts) {
516	$cv->begin;	759	$cv->begin;
517	ping_host_then_call_callback $host, sub {	760	ping_host_then_call_callback $host, sub {
518	$result{$host} = ...;	761	$result{$host} = ...;
…		…
533	loop, which serves two important purposes: first, it sets the callback	776	loop, which serves two important purposes: first, it sets the callback
534	to be called once the counter reaches C<0>, and second, it ensures that	777	to be called once the counter reaches C<0>, and second, it ensures that
535	C<send> is called even when C<no> hosts are being pinged (the loop	778	C<send> is called even when C<no> hosts are being pinged (the loop
536	doesn't execute once).	779	doesn't execute once).
537		780
538	This is the general pattern when you "fan out" into multiple subrequests:	781	This is the general pattern when you "fan out" into multiple (but
539	use an outer C<begin>/C<end> pair to set the callback and ensure C<end>	782	potentially zero) subrequests: use an outer C<begin>/C<end> pair to set
540	is called at least once, and then, for each subrequest you start, call	783	the callback and ensure C<end> is called at least once, and then, for each
541	C<begin> and for each subrequest you finish, call C<end>.	784	subrequest you start, call C<begin> and for each subrequest you finish,
		785	call C<end>.
542		786
543	=back	787	=back
544		788
545	=head3 METHODS FOR CONSUMERS	789	=head3 METHODS FOR CONSUMERS
546		790
…		…
550	=over 4	794	=over 4
551		795
552	=item $cv->recv	796	=item $cv->recv
553		797
554	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak	798	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
555	>> methods have been called on c<$cv>, while servicing other watchers	799	>> methods have been called on C<$cv>, while servicing other watchers
556	normally.	800	normally.
557		801
558	You can only wait once on a condition - additional calls are valid but	802	You can only wait once on a condition - additional calls are valid but
559	will return immediately.	803	will return immediately.
560		804
…		…
562	function will call C<croak>.	806	function will call C<croak>.
563		807
564	In list context, all parameters passed to C<send> will be returned,	808	In list context, all parameters passed to C<send> will be returned,
565	in scalar context only the first one will be returned.	809	in scalar context only the first one will be returned.
566		810
		811	Note that doing a blocking wait in a callback is not supported by any
		812	event loop, that is, recursive invocation of a blocking C<< ->recv
		813	>> is not allowed, and the C<recv> call will C<croak> if such a
		814	condition is detected. This condition can be slightly loosened by using
		815	L<Coro::AnyEvent>, which allows you to do a blocking C<< ->recv >> from
		816	any thread that doesn't run the event loop itself.
		817
567	Not all event models support a blocking wait - some die in that case	818	Not all event models support a blocking wait - some die in that case
568	(programs might want to do that to stay interactive), so I<if you are	819	(programs might want to do that to stay interactive), so I<if you are
569	using this from a module, never require a blocking wait>, but let the	820	using this from a module, never require a blocking wait>. Instead, let the
570	caller decide whether the call will block or not (for example, by coupling	821	caller decide whether the call will block or not (for example, by coupling
571	condition variables with some kind of request results and supporting	822	condition variables with some kind of request results and supporting
572	callbacks so the caller knows that getting the result will not block,	823	callbacks so the caller knows that getting the result will not block,
573	while still supporting blocking waits if the caller so desires).	824	while still supporting blocking waits if the caller so desires).
574		825
575	Another reason I<never> to C<< ->recv >> in a module is that you cannot
576	sensibly have two C<< ->recv >>'s in parallel, as that would require
577	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
578	can supply.
579
580	The L<Coro> module, however, I<can> and I<does> supply coroutines and, in
581	fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe
582	versions and also integrates coroutines into AnyEvent, making blocking
583	C<< ->recv >> calls perfectly safe as long as they are done from another
584	coroutine (one that doesn't run the event loop).
585
586	You can ensure that C<< -recv >> never blocks by setting a callback and	826	You can ensure that C<< ->recv >> never blocks by setting a callback and
587	only calling C<< ->recv >> from within that callback (or at a later	827	only calling C<< ->recv >> from within that callback (or at a later
588	time). This will work even when the event loop does not support blocking	828	time). This will work even when the event loop does not support blocking
589	waits otherwise.	829	waits otherwise.
590		830
591	=item $bool = $cv->ready	831	=item $bool = $cv->ready
592		832
593	Returns true when the condition is "true", i.e. whether C<send> or	833	Returns true when the condition is "true", i.e. whether C<send> or
594	C<croak> have been called.	834	C<croak> have been called.
595		835
596	=item $cb = $cv->cb ([new callback])	836	=item $cb = $cv->cb ($cb->($cv))
597		837
598	This is a mutator function that returns the callback set and optionally	838	This is a mutator function that returns the callback set and optionally
599	replaces it before doing so.	839	replaces it before doing so.
600		840
601	The callback will be called when the condition becomes "true", i.e. when	841	The callback will be called when the condition becomes "true", i.e. when
602	C<send> or C<croak> are called, with the only argument being the condition	842	C<send> or C<croak> are called, with the only argument being the
603	variable itself. Calling C<recv> inside the callback or at any later time	843	condition variable itself. If the condition is already true, the
604	is guaranteed not to block.	844	callback is called immediately when it is set. Calling C<recv> inside
		845	the callback or at any later time is guaranteed not to block.
605		846
606	=back	847	=back
607		848
		849	=head1 SUPPORTED EVENT LOOPS/BACKENDS
		850
		851	The available backend classes are (every class has its own manpage):
		852
		853	=over 4
		854
		855	=item Backends that are autoprobed when no other event loop can be found.
		856
		857	EV is the preferred backend when no other event loop seems to be in
		858	use. If EV is not installed, then AnyEvent will fall back to its own
		859	pure-perl implementation, which is available everywhere as it comes with
		860	AnyEvent itself.
		861
		862	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		863	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
		864
		865	=item Backends that are transparently being picked up when they are used.
		866
		867	These will be used if they are already loaded when the first watcher
		868	is created, in which case it is assumed that the application is using
		869	them. This means that AnyEvent will automatically pick the right backend
		870	when the main program loads an event module before anything starts to
		871	create watchers. Nothing special needs to be done by the main program.
		872
		873	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		874	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		875	AnyEvent::Impl::Tk based on Tk, very broken.
		876	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		877	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		878	AnyEvent::Impl::Irssi used when running within irssi.
		879
		880	=item Backends with special needs.
		881
		882	Qt requires the Qt::Application to be instantiated first, but will
		883	otherwise be picked up automatically. As long as the main program
		884	instantiates the application before any AnyEvent watchers are created,
		885	everything should just work.
		886
		887	AnyEvent::Impl::Qt based on Qt.
		888
		889	Support for IO::Async can only be partial, as it is too broken and
		890	architecturally limited to even support the AnyEvent API. It also
		891	is the only event loop that needs the loop to be set explicitly, so
		892	it can only be used by a main program knowing about AnyEvent. See
		893	L<AnyEvent::Impl::IOAsync> for the gory details.
		894
		895	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
		896
		897	=item Event loops that are indirectly supported via other backends.
		898
		899	Some event loops can be supported via other modules:
		900
		901	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		902
		903	B<WxWidgets> has no support for watching file handles. However, you can
		904	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		905	polls 20 times per second, which was considered to be too horrible to even
		906	consider for AnyEvent.
		907
		908	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		909	backend, so it can be supported through POE.
		910
		911	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		912	load L<POE> when detecting them, in the hope that POE will pick them up,
		913	in which case everything will be automatic.
		914
		915	=back
		916
608	=head1 GLOBAL VARIABLES AND FUNCTIONS	917	=head1 GLOBAL VARIABLES AND FUNCTIONS
609		918
		919	These are not normally required to use AnyEvent, but can be useful to
		920	write AnyEvent extension modules.
		921
610	=over 4	922	=over 4
611		923
612	=item $AnyEvent::MODEL	924	=item $AnyEvent::MODEL
613		925
614	Contains C<undef> until the first watcher is being created. Then it	926	Contains C<undef> until the first watcher is being created, before the
		927	backend has been autodetected.
		928
615	contains the event model that is being used, which is the name of the	929	Afterwards it contains the event model that is being used, which is the
616	Perl class implementing the model. This class is usually one of the	930	name of the Perl class implementing the model. This class is usually one
617	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	931	of the C<AnyEvent::Impl::xxx> modules, but can be any other class in the
618	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	932	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
619		933	will be C<urxvt::anyevent>).
620	The known classes so far are:
621
622	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
623	AnyEvent::Impl::Event based on Event, second best choice.
624	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
625	AnyEvent::Impl::Glib based on Glib, third-best choice.
626	AnyEvent::Impl::Tk based on Tk, very bad choice.
627	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
628	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
629	AnyEvent::Impl::POE based on POE, not generic enough for full support.
630
631	There is no support for WxWidgets, as WxWidgets has no support for
632	watching file handles. However, you can use WxWidgets through the
633	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
634	second, which was considered to be too horrible to even consider for
635	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
636	it's adaptor.
637
638	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
639	autodetecting them.
640		934
641	=item AnyEvent::detect	935	=item AnyEvent::detect
642		936
643	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	937	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
644	if necessary. You should only call this function right before you would	938	if necessary. You should only call this function right before you would
645	have created an AnyEvent watcher anyway, that is, as late as possible at	939	have created an AnyEvent watcher anyway, that is, as late as possible at
646	runtime.	940	runtime, and not e.g. during initialisation of your module.
		941
		942	If you need to do some initialisation before AnyEvent watchers are
		943	created, use C<post_detect>.
647		944
648	=item $guard = AnyEvent::post_detect { BLOCK }	945	=item $guard = AnyEvent::post_detect { BLOCK }
649		946
650	Arranges for the code block to be executed as soon as the event model is	947	Arranges for the code block to be executed as soon as the event model is
651	autodetected (or immediately if this has already happened).	948	autodetected (or immediately if that has already happened).
		949
		950	The block will be executed I<after> the actual backend has been detected
		951	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		952	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		953	other initialisations - see the sources of L<AnyEvent::Strict> or
		954	L<AnyEvent::AIO> to see how this is used.
		955
		956	The most common usage is to create some global watchers, without forcing
		957	event module detection too early, for example, L<AnyEvent::AIO> creates
		958	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		959	avoid autodetecting the event module at load time.
652		960
653	If called in scalar or list context, then it creates and returns an object	961	If called in scalar or list context, then it creates and returns an object
654	that automatically removes the callback again when it is destroyed. See	962	that automatically removes the callback again when it is destroyed (or
		963	C<undef> when the hook was immediately executed). See L<AnyEvent::AIO> for
655	L<Coro::BDB> for a case where this is useful.	964	a case where this is useful.
		965
		966	Example: Create a watcher for the IO::AIO module and store it in
		967	C<$WATCHER>, but do so only do so after the event loop is initialised.
		968
		969	our WATCHER;
		970
		971	my $guard = AnyEvent::post_detect {
		972	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		973	};
		974
		975	# the ||= is important in case post_detect immediately runs the block,
		976	# as to not clobber the newly-created watcher. assigning both watcher and
		977	# post_detect guard to the same variable has the advantage of users being
		978	# able to just C<undef $WATCHER> if the watcher causes them grief.
		979
		980	$WATCHER ||= $guard;
656		981
657	=item @AnyEvent::post_detect	982	=item @AnyEvent::post_detect
658		983
659	If there are any code references in this array (you can C<push> to it	984	If there are any code references in this array (you can C<push> to it
660	before or after loading AnyEvent), then they will called directly after	985	before or after loading AnyEvent), then they will be called directly
661	the event loop has been chosen.	986	after the event loop has been chosen.
662		987
663	You should check C<$AnyEvent::MODEL> before adding to this array, though:	988	You should check C<$AnyEvent::MODEL> before adding to this array, though:
664	if it contains a true value then the event loop has already been detected,	989	if it is defined then the event loop has already been detected, and the
665	and the array will be ignored.	990	array will be ignored.
666		991
667	Best use C<AnyEvent::post_detect { BLOCK }> instead.	992	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		993	it, as it takes care of these details.
		994
		995	This variable is mainly useful for modules that can do something useful
		996	when AnyEvent is used and thus want to know when it is initialised, but do
		997	not need to even load it by default. This array provides the means to hook
		998	into AnyEvent passively, without loading it.
		999
		1000	Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used
		1001	together, you could put this into Coro (this is the actual code used by
		1002	Coro to accomplish this):
		1003
		1004	if (defined $AnyEvent::MODEL) {
		1005	# AnyEvent already initialised, so load Coro::AnyEvent
		1006	require Coro::AnyEvent;
		1007	} else {
		1008	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent
		1009	# as soon as it is
		1010	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };
		1011	}
668		1012
669	=back	1013	=back
670		1014
671	=head1 WHAT TO DO IN A MODULE	1015	=head1 WHAT TO DO IN A MODULE
672		1016
…		…
683	because it will stall the whole program, and the whole point of using	1027	because it will stall the whole program, and the whole point of using
684	events is to stay interactive.	1028	events is to stay interactive.
685		1029
686	It is fine, however, to call C<< ->recv >> when the user of your module	1030	It is fine, however, to call C<< ->recv >> when the user of your module
687	requests it (i.e. if you create a http request object ad have a method	1031	requests it (i.e. if you create a http request object ad have a method
688	called C<results> that returns the results, it should call C<< ->recv >>	1032	called C<results> that returns the results, it may call C<< ->recv >>
689	freely, as the user of your module knows what she is doing. always).	1033	freely, as the user of your module knows what she is doing. Always).
690		1034
691	=head1 WHAT TO DO IN THE MAIN PROGRAM	1035	=head1 WHAT TO DO IN THE MAIN PROGRAM
692		1036
693	There will always be a single main program - the only place that should	1037	There will always be a single main program - the only place that should
694	dictate which event model to use.	1038	dictate which event model to use.
695		1039
696	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	1040	If the program is not event-based, it need not do anything special, even
697	do anything special (it does not need to be event-based) and let AnyEvent	1041	when it depends on a module that uses an AnyEvent. If the program itself
698	decide which implementation to chose if some module relies on it.	1042	uses AnyEvent, but does not care which event loop is used, all it needs
		1043	to do is C<use AnyEvent>. In either case, AnyEvent will choose the best
		1044	available loop implementation.
699		1045
700	If the main program relies on a specific event model - for example, in	1046	If the main program relies on a specific event model - for example, in
701	Gtk2 programs you have to rely on the Glib module - you should load the	1047	Gtk2 programs you have to rely on the Glib module - you should load the
702	event module before loading AnyEvent or any module that uses it: generally	1048	event module before loading AnyEvent or any module that uses it: generally
703	speaking, you should load it as early as possible. The reason is that	1049	speaking, you should load it as early as possible. The reason is that
704	modules might create watchers when they are loaded, and AnyEvent will	1050	modules might create watchers when they are loaded, and AnyEvent will
705	decide on the event model to use as soon as it creates watchers, and it	1051	decide on the event model to use as soon as it creates watchers, and it
706	might chose the wrong one unless you load the correct one yourself.	1052	might choose the wrong one unless you load the correct one yourself.
707		1053
708	You can chose to use a pure-perl implementation by loading the	1054	You can chose to use a pure-perl implementation by loading the
709	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour	1055	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
710	everywhere, but letting AnyEvent chose the model is generally better.	1056	everywhere, but letting AnyEvent chose the model is generally better.
711		1057
…		…
727		1073
728		1074
729	=head1 OTHER MODULES	1075	=head1 OTHER MODULES
730		1076
731	The following is a non-exhaustive list of additional modules that use	1077	The following is a non-exhaustive list of additional modules that use
732	AnyEvent and can therefore be mixed easily with other AnyEvent modules	1078	AnyEvent as a client and can therefore be mixed easily with other AnyEvent
733	in the same program. Some of the modules come with AnyEvent, some are	1079	modules and other event loops in the same program. Some of the modules
734	available via CPAN.	1080	come as part of AnyEvent, the others are available via CPAN.
735		1081
736	=over 4	1082	=over 4
737		1083
738	=item L<AnyEvent::Util>	1084	=item L<AnyEvent::Util>
739		1085
740	Contains various utility functions that replace often-used but blocking	1086	Contains various utility functions that replace often-used blocking
741	functions such as C<inet_aton> by event-/callback-based versions.	1087	functions such as C<inet_aton> with event/callback-based versions.
742
743	=item L<AnyEvent::Handle>
744
745	Provide read and write buffers and manages watchers for reads and writes.
746		1088
747	=item L<AnyEvent::Socket>	1089	=item L<AnyEvent::Socket>
748		1090
749	Provides various utility functions for (internet protocol) sockets,	1091	Provides various utility functions for (internet protocol) sockets,
750	addresses and name resolution. Also functions to create non-blocking tcp	1092	addresses and name resolution. Also functions to create non-blocking tcp
751	connections or tcp servers, with IPv6 and SRV record support and more.	1093	connections or tcp servers, with IPv6 and SRV record support and more.
752		1094
		1095	=item L<AnyEvent::Handle>
		1096
		1097	Provide read and write buffers, manages watchers for reads and writes,
		1098	supports raw and formatted I/O, I/O queued and fully transparent and
		1099	non-blocking SSL/TLS (via L<AnyEvent::TLS>).
		1100
753	=item L<AnyEvent::DNS>	1101	=item L<AnyEvent::DNS>
754		1102
755	Provides rich asynchronous DNS resolver capabilities.	1103	Provides rich asynchronous DNS resolver capabilities.
756		1104
		1105	=item L<AnyEvent::HTTP>, L<AnyEvent::IRC>, L<AnyEvent::XMPP>, L<AnyEvent::GPSD>, L<AnyEvent::IGS>, L<AnyEvent::FCP>
		1106
		1107	Implement event-based interfaces to the protocols of the same name (for
		1108	the curious, IGS is the International Go Server and FCP is the Freenet
		1109	Client Protocol).
		1110
		1111	=item L<AnyEvent::Handle::UDP>
		1112
		1113	Here be danger!
		1114
		1115	As Pauli would put it, "Not only is it not right, it's not even wrong!" -
		1116	there are so many things wrong with AnyEvent::Handle::UDP, most notably
		1117	its use of a stream-based API with a protocol that isn't streamable, that
		1118	the only way to improve it is to delete it.
		1119
		1120	It features data corruption (but typically only under load) and general
		1121	confusion. On top, the author is not only clueless about UDP but also
		1122	fact-resistant - some gems of his understanding: "connect doesn't work
		1123	with UDP", "UDP packets are not IP packets", "UDP only has datagrams, not
		1124	packets", "I don't need to implement proper error checking as UDP doesn't
		1125	support error checking" and so on - he doesn't even understand what's
		1126	wrong with his module when it is explained to him.
		1127
		1128	=item L<AnyEvent::DBI>
		1129
		1130	Executes L<DBI> requests asynchronously in a proxy process for you,
		1131	notifying you in an event-based way when the operation is finished.
		1132
		1133	=item L<AnyEvent::AIO>
		1134
		1135	Truly asynchronous (as opposed to non-blocking) I/O, should be in the
		1136	toolbox of every event programmer. AnyEvent::AIO transparently fuses
		1137	L<IO::AIO> and AnyEvent together, giving AnyEvent access to event-based
		1138	file I/O, and much more.
		1139
757	=item L<AnyEvent::HTTPD>	1140	=item L<AnyEvent::HTTPD>
758		1141
759	Provides a simple web application server framework.	1142	A simple embedded webserver.
760		1143
761	=item L<AnyEvent::FastPing>	1144	=item L<AnyEvent::FastPing>
762		1145
763	The fastest ping in the west.	1146	The fastest ping in the west.
764		1147
765	=item L<Net::IRC3>
766
767	AnyEvent based IRC client module family.
768
769	=item L<Net::XMPP2>
770
771	AnyEvent based XMPP (Jabber protocol) module family.
772
773	=item L<Net::FCP>
774
775	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
776	of AnyEvent.
777
778	=item L<Event::ExecFlow>
779
780	High level API for event-based execution flow control.
781
782	=item L<Coro>	1148	=item L<Coro>
783		1149
784	Has special support for AnyEvent via L<Coro::AnyEvent>.	1150	Has special support for AnyEvent via L<Coro::AnyEvent>.
785		1151
786	=item L<AnyEvent::AIO>, L<IO::AIO>
787
788	Truly asynchronous I/O, should be in the toolbox of every event
789	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
790	together.
791
792	=item L<AnyEvent::BDB>, L<BDB>
793
794	Truly asynchronous Berkeley DB access. AnyEvent::AIO transparently fuses
795	IO::AIO and AnyEvent together.
796
797	=item L<IO::Lambda>
798
799	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
800
801	=back	1152	=back
802		1153
803	=cut	1154	=cut
804		1155
805	package AnyEvent;	1156	package AnyEvent;
806		1157
807	no warnings;	1158	# basically a tuned-down version of common::sense
808	use strict;	1159	sub common_sense {
		1160	# from common:.sense 3.3
		1161	${^WARNING_BITS} ^= ${^WARNING_BITS} ^ "\x3c\x3f\x33\x00\x0f\xf3\x0f\xc0\xf0\xfc\x33\x00";
		1162	# use strict vars subs - NO UTF-8, as Util.pm doesn't like this atm. (uts46data.pl)
		1163	$^H |= 0x00000600;
		1164	}
809		1165
		1166	BEGIN { AnyEvent::common_sense }
		1167
810	use Carp;	1168	use Carp ();
811		1169
812	our $VERSION = 4.11;	1170	our $VERSION = '5.271';
813	our $MODEL;	1171	our $MODEL;
814		1172
815	our $AUTOLOAD;	1173	our $AUTOLOAD;
816	our @ISA;	1174	our @ISA;
817		1175
818	our @REGISTRY;	1176	our @REGISTRY;
819		1177
820	our $WIN32;	1178	our $VERBOSE;
821		1179
822	BEGIN {	1180	BEGIN {
823	my $win32 = ! ! ($^O =~ /mswin32/i);	1181	require "AnyEvent/constants.pl";
824	eval "sub WIN32(){ $win32 }";
825	}
826		1182
		1183	eval "sub TAINT (){" . (${^TAINT}*1) . "}";
		1184
		1185	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1186	if ${^TAINT};
		1187
827	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;	1188	$VERBOSE = $ENV{PERL_ANYEVENT_VERBOSE}*1;
		1189
		1190	}
		1191
		1192	our $MAX_SIGNAL_LATENCY = 10;
828		1193
829	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred	1194	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
830		1195
831	{	1196	{
832	my $idx;	1197	my $idx;
…		…
834	for reverse split /\s*,\s*/,	1199	for reverse split /\s*,\s*/,
835	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";	1200	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
836	}	1201	}
837		1202
838	my @models = (	1203	my @models = (
839	[EV:: => AnyEvent::Impl::EV::],	1204	[EV:: => AnyEvent::Impl::EV:: , 1],
840	[Event:: => AnyEvent::Impl::Event::],
841	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1205	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl:: , 1],
842	# everything below here will not be autoprobed	1206	# everything below here will not (normally) be autoprobed
843	# as the pureperl backend should work everywhere	1207	# as the pureperl backend should work everywhere
844	# and is usually faster	1208	# and is usually faster
		1209	[Event:: => AnyEvent::Impl::Event::, 1],
		1210	[Glib:: => AnyEvent::Impl::Glib:: , 1], # becomes extremely slow with many watchers
		1211	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		1212	[Irssi:: => AnyEvent::Impl::Irssi::], # Irssi has a bogus "Event" package
845	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles	1213	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
846	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers
847	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
848	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program	1214	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
849	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza	1215	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
850	[Wx:: => AnyEvent::Impl::POE::],	1216	[Wx:: => AnyEvent::Impl::POE::],
851	[Prima:: => AnyEvent::Impl::POE::],	1217	[Prima:: => AnyEvent::Impl::POE::],
		1218	# IO::Async is just too broken - we would need workarounds for its
		1219	# byzantine signal and broken child handling, among others.
		1220	# IO::Async is rather hard to detect, as it doesn't have any
		1221	# obvious default class.
		1222	[IO::Async:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1223	[IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1224	[IO::Async::Notifier:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1225	[AnyEvent::Impl::IOAsync:: => AnyEvent::Impl::IOAsync::], # requires special main program
852	);	1226	);
853		1227
854	our %method = map +($_ => 1), qw(io timer time now signal child condvar one_event DESTROY);	1228	our %method = map +($_ => 1),
		1229	qw(io timer time now now_update signal child idle condvar one_event DESTROY);
855		1230
856	our @post_detect;	1231	our @post_detect;
857		1232
858	sub post_detect(&) {	1233	sub post_detect(&) {
859	my ($cb) = @_;	1234	my ($cb) = @_;
860		1235
861	if ($MODEL) {
862	$cb->();
863
864	1
865	} else {
866	push @post_detect, $cb;	1236	push @post_detect, $cb;
867		1237
868	defined wantarray	1238	defined wantarray
869	? bless \$cb, "AnyEvent::Util::PostDetect"	1239	? bless \$cb, "AnyEvent::Util::postdetect"
870	: ()	1240	: ()
		1241	}
		1242
		1243	sub AnyEvent::Util::postdetect::DESTROY {
		1244	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		1245	}
		1246
		1247	sub detect() {
		1248	# free some memory
		1249	*detect = sub () { $MODEL };
		1250
		1251	local $!; # for good measure
		1252	local $SIG{__DIE__};
		1253
		1254	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
		1255	my $model = "AnyEvent::Impl::$1";
		1256	if (eval "require $model") {
		1257	$MODEL = $model;
		1258	warn "AnyEvent: loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.\n" if $VERBOSE >= 2;
		1259	} else {
		1260	warn "AnyEvent: unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@" if $VERBOSE;
		1261	}
871	}	1262	}
872	}
873		1263
874	sub AnyEvent::Util::PostDetect::DESTROY {	1264	# check for already loaded models
875	@post_detect = grep $_ != ${$_[0]}, @post_detect;
876	}
877
878	sub detect() {
879	unless ($MODEL) {	1265	unless ($MODEL) {
880	no strict 'refs';	1266	for (@REGISTRY, @models) {
881	local $SIG{__DIE__};	1267	my ($package, $model) = @$_;
882		1268	if (${"$package\::VERSION"} > 0) {
883	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
884	my $model = "AnyEvent::Impl::$1";
885	if (eval "require $model") {	1269	if (eval "require $model") {
886	$MODEL = $model;	1270	$MODEL = $model;
887	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	1271	warn "AnyEvent: autodetected model '$model', using it.\n" if $VERBOSE >= 2;
888	} else {	1272	last;
889	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;	1273	}
890	}	1274	}
891	}	1275	}
892		1276
893	# check for already loaded models
894	unless ($MODEL) {	1277	unless ($MODEL) {
		1278	# try to autoload a model
895	for (@REGISTRY, @models) {	1279	for (@REGISTRY, @models) {
896	my ($package, $model) = @$_;	1280	my ($package, $model, $autoload) = @$_;
		1281	if (
		1282	$autoload
		1283	and eval "require $package"
897	if (${"$package\::VERSION"} > 0) {	1284	and ${"$package\::VERSION"} > 0
898	if (eval "require $model") {	1285	and eval "require $model"
		1286	) {
899	$MODEL = $model;	1287	$MODEL = $model;
900	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;	1288	warn "AnyEvent: autoloaded model '$model', using it.\n" if $VERBOSE >= 2;
901	last;	1289	last;
902	}
903	}	1290	}
904	}	1291	}
905		1292
906	unless ($MODEL) {
907	# try to load a model
908
909	for (@REGISTRY, @models) {
910	my ($package, $model) = @$_;
911	if (eval "require $package"
912	and ${"$package\::VERSION"} > 0
913	and eval "require $model") {
914	$MODEL = $model;
915	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;
916	last;
917	}
918	}
919
920	$MODEL	1293	$MODEL
921	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.";	1294	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.\n";
922	}
923	}	1295	}
924
925	unshift @ISA, $MODEL;
926	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
927
928	(shift @post_detect)->() while @post_detect;
929	}	1296	}
		1297
		1298	@models = (); # free probe data
		1299
		1300	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		1301	unshift @ISA, $MODEL;
		1302
		1303	# now nuke some methods that are overriden by the backend.
		1304	# SUPER is not allowed.
		1305	for (qw(time signal child idle)) {
		1306	undef &{"AnyEvent::Base::$_"}
		1307	if defined &{"$MODEL\::$_"};
		1308	}
		1309
		1310	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
		1311
		1312	(shift @post_detect)->() while @post_detect;
		1313
		1314	*post_detect = sub(&) {
		1315	shift->();
		1316
		1317	undef
		1318	};
930		1319
931	$MODEL	1320	$MODEL
932	}	1321	}
933		1322
934	sub AUTOLOAD {	1323	sub AUTOLOAD {
935	(my $func = $AUTOLOAD) =~ s/.*://;	1324	(my $func = $AUTOLOAD) =~ s/.*://;
936		1325
937	$method{$func}	1326	$method{$func}
938	or croak "$func: not a valid method for AnyEvent objects";	1327	or Carp::croak "$func: not a valid AnyEvent class method";
939		1328
940	detect unless $MODEL;	1329	detect;
941		1330
942	my $class = shift;	1331	my $class = shift;
943	$class->$func (@_);	1332	$class->$func (@_);
944	}	1333	}
945		1334
		1335	# utility function to dup a filehandle. this is used by many backends
		1336	# to support binding more than one watcher per filehandle (they usually
		1337	# allow only one watcher per fd, so we dup it to get a different one).
		1338	sub _dupfh($$;$$) {
		1339	my ($poll, $fh, $r, $w) = @_;
		1340
		1341	# cygwin requires the fh mode to be matching, unix doesn't
		1342	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1343
		1344	open my $fh2, $mode, $fh
		1345	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1346
		1347	# we assume CLOEXEC is already set by perl in all important cases
		1348
		1349	($fh2, $rw)
		1350	}
		1351
		1352	=head1 SIMPLIFIED AE API
		1353
		1354	Starting with version 5.0, AnyEvent officially supports a second, much
		1355	simpler, API that is designed to reduce the calling, typing and memory
		1356	overhead by using function call syntax and a fixed number of parameters.
		1357
		1358	See the L<AE> manpage for details.
		1359
		1360	=cut
		1361
		1362	package AE;
		1363
		1364	our $VERSION = $AnyEvent::VERSION;
		1365
		1366	# fall back to the main API by default - backends and AnyEvent::Base
		1367	# implementations can overwrite these.
		1368
		1369	sub io($$$) {
		1370	AnyEvent->io (fh => $_[0], poll => $_[1] ? "w" : "r", cb => $_[2])
		1371	}
		1372
		1373	sub timer($$$) {
		1374	AnyEvent->timer (after => $_[0], interval => $_[1], cb => $_[2])
		1375	}
		1376
		1377	sub signal($$) {
		1378	AnyEvent->signal (signal => $_[0], cb => $_[1])
		1379	}
		1380
		1381	sub child($$) {
		1382	AnyEvent->child (pid => $_[0], cb => $_[1])
		1383	}
		1384
		1385	sub idle($) {
		1386	AnyEvent->idle (cb => $_[0])
		1387	}
		1388
		1389	sub cv(;&) {
		1390	AnyEvent->condvar (@_ ? (cb => $_[0]) : ())
		1391	}
		1392
		1393	sub now() {
		1394	AnyEvent->now
		1395	}
		1396
		1397	sub now_update() {
		1398	AnyEvent->now_update
		1399	}
		1400
		1401	sub time() {
		1402	AnyEvent->time
		1403	}
		1404
946	package AnyEvent::Base;	1405	package AnyEvent::Base;
947		1406
948	# default implementation for now and time	1407	# default implementations for many methods
949		1408
950	use Time::HiRes ();	1409	sub time {
		1410	eval q{ # poor man's autoloading {}
		1411	# probe for availability of Time::HiRes
		1412	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1413	warn "AnyEvent: using Time::HiRes for sub-second timing accuracy.\n" if $VERBOSE >= 8;
		1414	*AE::time = \&Time::HiRes::time;
		1415	# if (eval "use POSIX (); (POSIX::times())...
		1416	} else {
		1417	warn "AnyEvent: using built-in time(), WARNING, no sub-second resolution!\n" if $VERBOSE;
		1418	*AE::time = sub (){ time }; # epic fail
		1419	}
951		1420
952	sub time { Time::HiRes::time }	1421	*time = sub { AE::time }; # different prototypes
953	sub now { Time::HiRes::time }	1422	};
		1423	die if $@;
		1424
		1425	&time
		1426	}
		1427
		1428	*now = \&time;
		1429
		1430	sub now_update { }
954		1431
955	# default implementation for ->condvar	1432	# default implementation for ->condvar
956		1433
957	sub condvar {	1434	sub condvar {
		1435	eval q{ # poor man's autoloading {}
		1436	*condvar = sub {
958	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, AnyEvent::CondVar::	1437	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
		1438	};
		1439
		1440	*AE::cv = sub (;&) {
		1441	bless { @_ ? (_ae_cb => shift) : () }, "AnyEvent::CondVar"
		1442	};
		1443	};
		1444	die if $@;
		1445
		1446	&condvar
959	}	1447	}
960		1448
961	# default implementation for ->signal	1449	# default implementation for ->signal
962		1450
963	our %SIG_CB;	1451	our $HAVE_ASYNC_INTERRUPT;
		1452
		1453	sub _have_async_interrupt() {
		1454	$HAVE_ASYNC_INTERRUPT = 1*(!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT}
		1455	&& eval "use Async::Interrupt 1.02 (); 1")
		1456	unless defined $HAVE_ASYNC_INTERRUPT;
		1457
		1458	$HAVE_ASYNC_INTERRUPT
		1459	}
		1460
		1461	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1462	our (%SIG_ASY, %SIG_ASY_W);
		1463	our ($SIG_COUNT, $SIG_TW);
		1464
		1465	# install a dummy wakeup watcher to reduce signal catching latency
		1466	# used by Impls
		1467	sub _sig_add() {
		1468	unless ($SIG_COUNT++) {
		1469	# try to align timer on a full-second boundary, if possible
		1470	my $NOW = AE::now;
		1471
		1472	$SIG_TW = AE::timer
		1473	$MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1474	$MAX_SIGNAL_LATENCY,
		1475	sub { } # just for the PERL_ASYNC_CHECK
		1476	;
		1477	}
		1478	}
		1479
		1480	sub _sig_del {
		1481	undef $SIG_TW
		1482	unless --$SIG_COUNT;
		1483	}
		1484
		1485	our $_sig_name_init; $_sig_name_init = sub {
		1486	eval q{ # poor man's autoloading {}
		1487	undef $_sig_name_init;
		1488
		1489	if (_have_async_interrupt) {
		1490	*sig2num = \&Async::Interrupt::sig2num;
		1491	*sig2name = \&Async::Interrupt::sig2name;
		1492	} else {
		1493	require Config;
		1494
		1495	my %signame2num;
		1496	@signame2num{ split ' ', $Config::Config{sig_name} }
		1497	= split ' ', $Config::Config{sig_num};
		1498
		1499	my @signum2name;
		1500	@signum2name[values %signame2num] = keys %signame2num;
		1501
		1502	*sig2num = sub($) {
		1503	$_[0] > 0 ? shift : $signame2num{+shift}
		1504	};
		1505	*sig2name = sub ($) {
		1506	$_[0] > 0 ? $signum2name[+shift] : shift
		1507	};
		1508	}
		1509	};
		1510	die if $@;
		1511	};
		1512
		1513	sub sig2num ($) { &$_sig_name_init; &sig2num }
		1514	sub sig2name($) { &$_sig_name_init; &sig2name }
964		1515
965	sub signal {	1516	sub signal {
		1517	eval q{ # poor man's autoloading {}
		1518	# probe for availability of Async::Interrupt
		1519	if (_have_async_interrupt) {
		1520	warn "AnyEvent: using Async::Interrupt for race-free signal handling.\n" if $VERBOSE >= 8;
		1521
		1522	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1523	$SIG_IO = AE::io $SIGPIPE_R->fileno, 0, \&_signal_exec;
		1524
		1525	} else {
		1526	warn "AnyEvent: using emulated perl signal handling with latency timer.\n" if $VERBOSE >= 8;
		1527
		1528	if (AnyEvent::WIN32) {
		1529	require AnyEvent::Util;
		1530
		1531	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1532	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R, 1) if $SIGPIPE_R;
		1533	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W, 1) if $SIGPIPE_W; # just in case
		1534	} else {
		1535	pipe $SIGPIPE_R, $SIGPIPE_W;
		1536	fcntl $SIGPIPE_R, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_R;
		1537	fcntl $SIGPIPE_W, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_W; # just in case
		1538
		1539	# not strictly required, as $^F is normally 2, but let's make sure...
		1540	fcntl $SIGPIPE_R, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1541	fcntl $SIGPIPE_W, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1542	}
		1543
		1544	$SIGPIPE_R
		1545	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1546
		1547	$SIG_IO = AE::io $SIGPIPE_R, 0, \&_signal_exec;
		1548	}
		1549
		1550	*signal = $HAVE_ASYNC_INTERRUPT
		1551	? sub {
966	my (undef, %arg) = @_;	1552	my (undef, %arg) = @_;
967		1553
		1554	# async::interrupt
968	my $signal = uc $arg{signal}	1555	my $signal = sig2num $arg{signal};
969	or Carp::croak "required option 'signal' is missing";
970
971	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1556	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1557
		1558	$SIG_ASY{$signal} ||= new Async::Interrupt
		1559	cb => sub { undef $SIG_EV{$signal} },
		1560	signal => $signal,
		1561	pipe => [$SIGPIPE_R->filenos],
		1562	pipe_autodrain => 0,
		1563	;
		1564
		1565	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1566	}
		1567	: sub {
		1568	my (undef, %arg) = @_;
		1569
		1570	# pure perl
		1571	my $signal = sig2name $arg{signal};
		1572	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1573
972	$SIG{$signal} ||= sub {	1574	$SIG{$signal} ||= sub {
		1575	local $!;
		1576	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1577	undef $SIG_EV{$signal};
		1578	};
		1579
		1580	# can't do signal processing without introducing races in pure perl,
		1581	# so limit the signal latency.
		1582	_sig_add;
		1583
		1584	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1585	}
		1586	;
		1587
		1588	*AnyEvent::Base::signal::DESTROY = sub {
		1589	my ($signal, $cb) = @{$_[0]};
		1590
		1591	_sig_del;
		1592
		1593	delete $SIG_CB{$signal}{$cb};
		1594
		1595	$HAVE_ASYNC_INTERRUPT
		1596	? delete $SIG_ASY{$signal}
		1597	: # delete doesn't work with older perls - they then
		1598	# print weird messages, or just unconditionally exit
		1599	# instead of getting the default action.
		1600	undef $SIG{$signal}
		1601	unless keys %{ $SIG_CB{$signal} };
		1602	};
		1603
		1604	*_signal_exec = sub {
		1605	$HAVE_ASYNC_INTERRUPT
		1606	? $SIGPIPE_R->drain
		1607	: sysread $SIGPIPE_R, (my $dummy), 9;
		1608
		1609	while (%SIG_EV) {
		1610	for (keys %SIG_EV) {
		1611	delete $SIG_EV{$_};
973	$_->() for values %{ $SIG_CB{$signal} || {} };	1612	$_->() for values %{ $SIG_CB{$_} || {} };
		1613	}
		1614	}
		1615	};
974	};	1616	};
		1617	die if $@;
975		1618
976	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1619	&signal
977	}
978
979	sub AnyEvent::Base::Signal::DESTROY {
980	my ($signal, $cb) = @{$_[0]};
981
982	delete $SIG_CB{$signal}{$cb};
983
984	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };
985	}	1620	}
986		1621
987	# default implementation for ->child	1622	# default implementation for ->child
988		1623
989	our %PID_CB;	1624	our %PID_CB;
990	our $CHLD_W;	1625	our $CHLD_W;
991	our $CHLD_DELAY_W;	1626	our $CHLD_DELAY_W;
992	our $PID_IDLE;
993	our $WNOHANG;	1627	our $WNOHANG;
994		1628
995	sub _child_wait {	1629	# used by many Impl's
996	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1630	sub _emit_childstatus($$) {
		1631	my (undef, $rpid, $rstatus) = @_;
		1632
		1633	$_->($rpid, $rstatus)
997	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1634	for values %{ $PID_CB{$rpid} || {} },
998	(values %{ $PID_CB{0} || {} });	1635	values %{ $PID_CB{0} || {} };
999	}
1000
1001	undef $PID_IDLE;
1002	}
1003
1004	sub _sigchld {
1005	# make sure we deliver these changes "synchronous" with the event loop.
1006	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {
1007	undef $CHLD_DELAY_W;
1008	&_child_wait;
1009	});
1010	}	1636	}
1011		1637
1012	sub child {	1638	sub child {
		1639	eval q{ # poor man's autoloading {}
		1640	*_sigchld = sub {
		1641	my $pid;
		1642
		1643	AnyEvent->_emit_childstatus ($pid, $?)
		1644	while ($pid = waitpid -1, $WNOHANG) > 0;
		1645	};
		1646
		1647	*child = sub {
1013	my (undef, %arg) = @_;	1648	my (undef, %arg) = @_;
1014		1649
1015	defined (my $pid = $arg{pid} + 0)	1650	defined (my $pid = $arg{pid} + 0)
1016	or Carp::croak "required option 'pid' is missing";	1651	or Carp::croak "required option 'pid' is missing";
1017		1652
1018	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1653	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
1019		1654
1020	unless ($WNOHANG) {	1655	# WNOHANG is almost cetrainly 1 everywhere
		1656	$WNOHANG ||= $^O =~ /^(?:openbsd|netbsd|linux|freebsd|cygwin|MSWin32)$/
		1657	? 1
1021	$WNOHANG = eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;	1658	: eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
1022	}
1023		1659
1024	unless ($CHLD_W) {	1660	unless ($CHLD_W) {
1025	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1661	$CHLD_W = AE::signal CHLD => \&_sigchld;
1026	# child could be a zombie already, so make at least one round	1662	# child could be a zombie already, so make at least one round
1027	&_sigchld;	1663	&_sigchld;
1028	}	1664	}
1029		1665
1030	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	1666	bless [$pid, $arg{cb}], "AnyEvent::Base::child"
1031	}	1667	};
1032		1668
1033	sub AnyEvent::Base::Child::DESTROY {	1669	*AnyEvent::Base::child::DESTROY = sub {
1034	my ($pid, $cb) = @{$_[0]};	1670	my ($pid, $cb) = @{$_[0]};
1035		1671
1036	delete $PID_CB{$pid}{$cb};	1672	delete $PID_CB{$pid}{$cb};
1037	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1673	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
1038		1674
1039	undef $CHLD_W unless keys %PID_CB;	1675	undef $CHLD_W unless keys %PID_CB;
		1676	};
		1677	};
		1678	die if $@;
		1679
		1680	&child
		1681	}
		1682
		1683	# idle emulation is done by simply using a timer, regardless
		1684	# of whether the process is idle or not, and not letting
		1685	# the callback use more than 50% of the time.
		1686	sub idle {
		1687	eval q{ # poor man's autoloading {}
		1688	*idle = sub {
		1689	my (undef, %arg) = @_;
		1690
		1691	my ($cb, $w, $rcb) = $arg{cb};
		1692
		1693	$rcb = sub {
		1694	if ($cb) {
		1695	$w = _time;
		1696	&$cb;
		1697	$w = _time - $w;
		1698
		1699	# never use more then 50% of the time for the idle watcher,
		1700	# within some limits
		1701	$w = 0.0001 if $w < 0.0001;
		1702	$w = 5 if $w > 5;
		1703
		1704	$w = AE::timer $w, 0, $rcb;
		1705	} else {
		1706	# clean up...
		1707	undef $w;
		1708	undef $rcb;
		1709	}
		1710	};
		1711
		1712	$w = AE::timer 0.05, 0, $rcb;
		1713
		1714	bless \\$cb, "AnyEvent::Base::idle"
		1715	};
		1716
		1717	*AnyEvent::Base::idle::DESTROY = sub {
		1718	undef $${$_[0]};
		1719	};
		1720	};
		1721	die if $@;
		1722
		1723	&idle
1040	}	1724	}
1041		1725
1042	package AnyEvent::CondVar;	1726	package AnyEvent::CondVar;
1043		1727
1044	our @ISA = AnyEvent::CondVar::Base::;	1728	our @ISA = AnyEvent::CondVar::Base::;
1045		1729
1046	package AnyEvent::CondVar::Base;	1730	package AnyEvent::CondVar::Base;
1047		1731
1048	use overload	1732	#use overload
1049	'&{}' => sub { my $self = shift; sub { $self->send (@_) } },	1733	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
1050	fallback => 1;	1734	# fallback => 1;
		1735
		1736	# save 300+ kilobytes by dirtily hardcoding overloading
		1737	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1738	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1739	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1740	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1741
		1742	our $WAITING;
1051		1743
1052	sub _send {	1744	sub _send {
1053	# nop	1745	# nop
1054	}	1746	}
1055		1747
…		…
1068	sub ready {	1760	sub ready {
1069	$_[0]{_ae_sent}	1761	$_[0]{_ae_sent}
1070	}	1762	}
1071		1763
1072	sub _wait {	1764	sub _wait {
		1765	$WAITING
		1766	and !$_[0]{_ae_sent}
		1767	and Carp::croak "AnyEvent::CondVar: recursive blocking wait detected";
		1768
		1769	local $WAITING = 1;
1073	AnyEvent->one_event while !$_[0]{_ae_sent};	1770	AnyEvent->one_event while !$_[0]{_ae_sent};
1074	}	1771	}
1075		1772
1076	sub recv {	1773	sub recv {
1077	$_[0]->_wait;	1774	$_[0]->_wait;
…		…
1079	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};	1776	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
1080	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]	1777	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
1081	}	1778	}
1082		1779
1083	sub cb {	1780	sub cb {
1084	$_[0]{_ae_cb} = $_[1] if @_ > 1;	1781	my $cv = shift;
		1782
		1783	@_
		1784	and $cv->{_ae_cb} = shift
		1785	and $cv->{_ae_sent}
		1786	and (delete $cv->{_ae_cb})->($cv);
		1787
1085	$_[0]{_ae_cb}	1788	$cv->{_ae_cb}
1086	}	1789	}
1087		1790
1088	sub begin {	1791	sub begin {
1089	++$_[0]{_ae_counter};	1792	++$_[0]{_ae_counter};
1090	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;	1793	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
…		…
1096	}	1799	}
1097		1800
1098	# undocumented/compatibility with pre-3.4	1801	# undocumented/compatibility with pre-3.4
1099	*broadcast = \&send;	1802	*broadcast = \&send;
1100	*wait = \&_wait;	1803	*wait = \&_wait;
		1804
		1805	=head1 ERROR AND EXCEPTION HANDLING
		1806
		1807	In general, AnyEvent does not do any error handling - it relies on the
		1808	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1809	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1810	checking of all AnyEvent methods, however, which is highly useful during
		1811	development.
		1812
		1813	As for exception handling (i.e. runtime errors and exceptions thrown while
		1814	executing a callback), this is not only highly event-loop specific, but
		1815	also not in any way wrapped by this module, as this is the job of the main
		1816	program.
		1817
		1818	The pure perl event loop simply re-throws the exception (usually
		1819	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1820	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1821	so on.
		1822
		1823	=head1 ENVIRONMENT VARIABLES
		1824
		1825	The following environment variables are used by this module or its
		1826	submodules.
		1827
		1828	Note that AnyEvent will remove I<all> environment variables starting with
		1829	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		1830	enabled.
		1831
		1832	=over 4
		1833
		1834	=item C<PERL_ANYEVENT_VERBOSE>
		1835
		1836	By default, AnyEvent will be completely silent except in fatal
		1837	conditions. You can set this environment variable to make AnyEvent more
		1838	talkative.
		1839
		1840	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1841	conditions, such as not being able to load the event model specified by
		1842	C<PERL_ANYEVENT_MODEL>.
		1843
		1844	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1845	model it chooses.
		1846
		1847	When set to C<8> or higher, then AnyEvent will report extra information on
		1848	which optional modules it loads and how it implements certain features.
		1849
		1850	=item C<PERL_ANYEVENT_STRICT>
		1851
		1852	AnyEvent does not do much argument checking by default, as thorough
		1853	argument checking is very costly. Setting this variable to a true value
		1854	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1855	check the arguments passed to most method calls. If it finds any problems,
		1856	it will croak.
		1857
		1858	In other words, enables "strict" mode.
		1859
		1860	Unlike C<use strict> (or its modern cousin, C<< use L<common::sense>
		1861	>>, it is definitely recommended to keep it off in production. Keeping
		1862	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		1863	can be very useful, however.
		1864
		1865	=item C<PERL_ANYEVENT_MODEL>
		1866
		1867	This can be used to specify the event model to be used by AnyEvent, before
		1868	auto detection and -probing kicks in. It must be a string consisting
		1869	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1870	and the resulting module name is loaded and if the load was successful,
		1871	used as event model. If it fails to load AnyEvent will proceed with
		1872	auto detection and -probing.
		1873
		1874	This functionality might change in future versions.
		1875
		1876	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1877	could start your program like this:
		1878
		1879	PERL_ANYEVENT_MODEL=Perl perl ...
		1880
		1881	=item C<PERL_ANYEVENT_PROTOCOLS>
		1882
		1883	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1884	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1885	of auto probing).
		1886
		1887	Must be set to a comma-separated list of protocols or address families,
		1888	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1889	used, and preference will be given to protocols mentioned earlier in the
		1890	list.
		1891
		1892	This variable can effectively be used for denial-of-service attacks
		1893	against local programs (e.g. when setuid), although the impact is likely
		1894	small, as the program has to handle conenction and other failures anyways.
		1895
		1896	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1897	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1898	- only support IPv4, never try to resolve or contact IPv6
		1899	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1900	IPv6, but prefer IPv6 over IPv4.
		1901
		1902	=item C<PERL_ANYEVENT_EDNS0>
		1903
		1904	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1905	for DNS. This extension is generally useful to reduce DNS traffic, but
		1906	some (broken) firewalls drop such DNS packets, which is why it is off by
		1907	default.
		1908
		1909	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1910	EDNS0 in its DNS requests.
		1911
		1912	=item C<PERL_ANYEVENT_MAX_FORKS>
		1913
		1914	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1915	will create in parallel.
		1916
		1917	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		1918
		1919	The default value for the C<max_outstanding> parameter for the default DNS
		1920	resolver - this is the maximum number of parallel DNS requests that are
		1921	sent to the DNS server.
		1922
		1923	=item C<PERL_ANYEVENT_RESOLV_CONF>
		1924
		1925	The file to use instead of F</etc/resolv.conf> (or OS-specific
		1926	configuration) in the default resolver. When set to the empty string, no
		1927	default config will be used.
		1928
		1929	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		1930
		1931	When neither C<ca_file> nor C<ca_path> was specified during
		1932	L<AnyEvent::TLS> context creation, and either of these environment
		1933	variables exist, they will be used to specify CA certificate locations
		1934	instead of a system-dependent default.
		1935
		1936	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		1937
		1938	When these are set to C<1>, then the respective modules are not
		1939	loaded. Mostly good for testing AnyEvent itself.
		1940
		1941	=back
1101		1942
1102	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1943	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
1103		1944
1104	This is an advanced topic that you do not normally need to use AnyEvent in	1945	This is an advanced topic that you do not normally need to use AnyEvent in
1105	a module. This section is only of use to event loop authors who want to	1946	a module. This section is only of use to event loop authors who want to
…		…
1139		1980
1140	I<rxvt-unicode> also cheats a bit by not providing blocking access to	1981	I<rxvt-unicode> also cheats a bit by not providing blocking access to
1141	condition variables: code blocking while waiting for a condition will	1982	condition variables: code blocking while waiting for a condition will
1142	C<die>. This still works with most modules/usages, and blocking calls must	1983	C<die>. This still works with most modules/usages, and blocking calls must
1143	not be done in an interactive application, so it makes sense.	1984	not be done in an interactive application, so it makes sense.
1144
1145	=head1 ENVIRONMENT VARIABLES
1146
1147	The following environment variables are used by this module:
1148
1149	=over 4
1150
1151	=item C<PERL_ANYEVENT_VERBOSE>
1152
1153	By default, AnyEvent will be completely silent except in fatal
1154	conditions. You can set this environment variable to make AnyEvent more
1155	talkative.
1156
1157	When set to C<1> or higher, causes AnyEvent to warn about unexpected
1158	conditions, such as not being able to load the event model specified by
1159	C<PERL_ANYEVENT_MODEL>.
1160
1161	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
1162	model it chooses.
1163
1164	=item C<PERL_ANYEVENT_MODEL>
1165
1166	This can be used to specify the event model to be used by AnyEvent, before
1167	auto detection and -probing kicks in. It must be a string consisting
1168	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
1169	and the resulting module name is loaded and if the load was successful,
1170	used as event model. If it fails to load AnyEvent will proceed with
1171	auto detection and -probing.
1172
1173	This functionality might change in future versions.
1174
1175	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
1176	could start your program like this:
1177
1178	PERL_ANYEVENT_MODEL=Perl perl ...
1179
1180	=item C<PERL_ANYEVENT_PROTOCOLS>
1181
1182	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
1183	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
1184	of auto probing).
1185
1186	Must be set to a comma-separated list of protocols or address families,
1187	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
1188	used, and preference will be given to protocols mentioned earlier in the
1189	list.
1190
1191	This variable can effectively be used for denial-of-service attacks
1192	against local programs (e.g. when setuid), although the impact is likely
1193	small, as the program has to handle connection errors already-
1194
1195	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
1196	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
1197	- only support IPv4, never try to resolve or contact IPv6
1198	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
1199	IPv6, but prefer IPv6 over IPv4.
1200
1201	=item C<PERL_ANYEVENT_EDNS0>
1202
1203	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
1204	for DNS. This extension is generally useful to reduce DNS traffic, but
1205	some (broken) firewalls drop such DNS packets, which is why it is off by
1206	default.
1207
1208	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
1209	EDNS0 in its DNS requests.
1210
1211	=item C<PERL_ANYEVENT_MAX_FORKS>
1212
1213	The maximum number of child processes that C<AnyEvent::Util::fork_call>
1214	will create in parallel.
1215
1216	=back
1217		1985
1218	=head1 EXAMPLE PROGRAM	1986	=head1 EXAMPLE PROGRAM
1219		1987
1220	The following program uses an I/O watcher to read data from STDIN, a timer	1988	The following program uses an I/O watcher to read data from STDIN, a timer
1221	to display a message once per second, and a condition variable to quit the	1989	to display a message once per second, and a condition variable to quit the
…		…
1234	warn "read: $input\n"; # output what has been read	2002	warn "read: $input\n"; # output what has been read
1235	$cv->send if $input =~ /^q/i; # quit program if /^q/i	2003	$cv->send if $input =~ /^q/i; # quit program if /^q/i
1236	},	2004	},
1237	);	2005	);
1238		2006
1239	my $time_watcher; # can only be used once
1240
1241	sub new_timer {
1242	$timer = AnyEvent->timer (after => 1, cb => sub {	2007	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
1243	warn "timeout\n"; # print 'timeout' about every second	2008	warn "timeout\n"; # print 'timeout' at most every second
1244	&new_timer; # and restart the time
1245	});	2009	});
1246	}
1247
1248	new_timer; # create first timer
1249		2010
1250	$cv->recv; # wait until user enters /^q/i	2011	$cv->recv; # wait until user enters /^q/i
1251		2012
1252	=head1 REAL-WORLD EXAMPLE	2013	=head1 REAL-WORLD EXAMPLE
1253		2014
…		…
1326		2087
1327	The actual code goes further and collects all errors (C<die>s, exceptions)	2088	The actual code goes further and collects all errors (C<die>s, exceptions)
1328	that occurred during request processing. The C<result> method detects	2089	that occurred during request processing. The C<result> method detects
1329	whether an exception as thrown (it is stored inside the $txn object)	2090	whether an exception as thrown (it is stored inside the $txn object)
1330	and just throws the exception, which means connection errors and other	2091	and just throws the exception, which means connection errors and other
1331	problems get reported tot he code that tries to use the result, not in a	2092	problems get reported to the code that tries to use the result, not in a
1332	random callback.	2093	random callback.
1333		2094
1334	All of this enables the following usage styles:	2095	All of this enables the following usage styles:
1335		2096
1336	1. Blocking:	2097	1. Blocking:
…		…
1384	through AnyEvent. The benchmark creates a lot of timers (with a zero	2145	through AnyEvent. The benchmark creates a lot of timers (with a zero
1385	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,	2146	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
1386	which it is), lets them fire exactly once and destroys them again.	2147	which it is), lets them fire exactly once and destroys them again.
1387		2148
1388	Source code for this benchmark is found as F<eg/bench> in the AnyEvent	2149	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
1389	distribution.	2150	distribution. It uses the L<AE> interface, which makes a real difference
		2151	for the EV and Perl backends only.
1390		2152
1391	=head3 Explanation of the columns	2153	=head3 Explanation of the columns
1392		2154
1393	I<watcher> is the number of event watchers created/destroyed. Since	2155	I<watcher> is the number of event watchers created/destroyed. Since
1394	different event models feature vastly different performances, each event	2156	different event models feature vastly different performances, each event
…		…
1415	watcher.	2177	watcher.
1416		2178
1417	=head3 Results	2179	=head3 Results
1418		2180
1419	name watchers bytes create invoke destroy comment	2181	name watchers bytes create invoke destroy comment
1420	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	2182	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
1421	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	2183	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
1422	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	2184	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
1423	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	2185	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
1424	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	2186	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
1425	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers	2187	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
		2188	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
		2189	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
1426	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	2190	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
1427	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	2191	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
1428	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	2192	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
1429	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	2193	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
1430		2194
1431	=head3 Discussion	2195	=head3 Discussion
1432		2196
1433	The benchmark does I<not> measure scalability of the event loop very	2197	The benchmark does I<not> measure scalability of the event loop very
1434	well. For example, a select-based event loop (such as the pure perl one)	2198	well. For example, a select-based event loop (such as the pure perl one)
…		…
1446	benchmark machine, handling an event takes roughly 1600 CPU cycles with	2210	benchmark machine, handling an event takes roughly 1600 CPU cycles with
1447	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU	2211	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
1448	cycles with POE.	2212	cycles with POE.
1449		2213
1450	C<EV> is the sole leader regarding speed and memory use, which are both	2214	C<EV> is the sole leader regarding speed and memory use, which are both
1451	maximal/minimal, respectively. Even when going through AnyEvent, it uses	2215	maximal/minimal, respectively. When using the L<AE> API there is zero
		2216	overhead (when going through the AnyEvent API create is about 5-6 times
		2217	slower, with other times being equal, so still uses far less memory than
1452	far less memory than any other event loop and is still faster than Event	2218	any other event loop and is still faster than Event natively).
1453	natively.
1454		2219
1455	The pure perl implementation is hit in a few sweet spots (both the	2220	The pure perl implementation is hit in a few sweet spots (both the
1456	constant timeout and the use of a single fd hit optimisations in the perl	2221	constant timeout and the use of a single fd hit optimisations in the perl
1457	interpreter and the backend itself). Nevertheless this shows that it	2222	interpreter and the backend itself). Nevertheless this shows that it
1458	adds very little overhead in itself. Like any select-based backend its	2223	adds very little overhead in itself. Like any select-based backend its
1459	performance becomes really bad with lots of file descriptors (and few of	2224	performance becomes really bad with lots of file descriptors (and few of
1460	them active), of course, but this was not subject of this benchmark.	2225	them active), of course, but this was not subject of this benchmark.
1461		2226
1462	The C<Event> module has a relatively high setup and callback invocation	2227	The C<Event> module has a relatively high setup and callback invocation
1463	cost, but overall scores in on the third place.	2228	cost, but overall scores in on the third place.
		2229
		2230	C<IO::Async> performs admirably well, about on par with C<Event>, even
		2231	when using its pure perl backend.
1464		2232
1465	C<Glib>'s memory usage is quite a bit higher, but it features a	2233	C<Glib>'s memory usage is quite a bit higher, but it features a
1466	faster callback invocation and overall ends up in the same class as	2234	faster callback invocation and overall ends up in the same class as
1467	C<Event>. However, Glib scales extremely badly, doubling the number of	2235	C<Event>. However, Glib scales extremely badly, doubling the number of
1468	watchers increases the processing time by more than a factor of four,	2236	watchers increases the processing time by more than a factor of four,
…		…
1529	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100	2297	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
1530	(1%) are active. This mirrors the activity of large servers with many	2298	(1%) are active. This mirrors the activity of large servers with many
1531	connections, most of which are idle at any one point in time.	2299	connections, most of which are idle at any one point in time.
1532		2300
1533	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent	2301	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
1534	distribution.	2302	distribution. It uses the L<AE> interface, which makes a real difference
		2303	for the EV and Perl backends only.
1535		2304
1536	=head3 Explanation of the columns	2305	=head3 Explanation of the columns
1537		2306
1538	I<sockets> is the number of sockets, and twice the number of "servers" (as	2307	I<sockets> is the number of sockets, and twice the number of "servers" (as
1539	each server has a read and write socket end).	2308	each server has a read and write socket end).
…		…
1546	it to another server. This includes deleting the old timeout and creating	2315	it to another server. This includes deleting the old timeout and creating
1547	a new one that moves the timeout into the future.	2316	a new one that moves the timeout into the future.
1548		2317
1549	=head3 Results	2318	=head3 Results
1550		2319
1551	name sockets create request	2320	name sockets create request
1552	EV 20000 69.01 11.16	2321	EV 20000 62.66 7.99
1553	Perl 20000 73.32 35.87	2322	Perl 20000 68.32 32.64
1554	Event 20000 212.62 257.32	2323	IOAsync 20000 174.06 101.15 epoll
1555	Glib 20000 651.16 1896.30	2324	IOAsync 20000 174.67 610.84 poll
		2325	Event 20000 202.69 242.91
		2326	Glib 20000 557.01 1689.52
1556	POE 20000 349.67 12317.24 uses POE::Loop::Event	2327	POE 20000 341.54 12086.32 uses POE::Loop::Event
1557		2328
1558	=head3 Discussion	2329	=head3 Discussion
1559		2330
1560	This benchmark I<does> measure scalability and overall performance of the	2331	This benchmark I<does> measure scalability and overall performance of the
1561	particular event loop.	2332	particular event loop.
…		…
1563	EV is again fastest. Since it is using epoll on my system, the setup time	2334	EV is again fastest. Since it is using epoll on my system, the setup time
1564	is relatively high, though.	2335	is relatively high, though.
1565		2336
1566	Perl surprisingly comes second. It is much faster than the C-based event	2337	Perl surprisingly comes second. It is much faster than the C-based event
1567	loops Event and Glib.	2338	loops Event and Glib.
		2339
		2340	IO::Async performs very well when using its epoll backend, and still quite
		2341	good compared to Glib when using its pure perl backend.
1568		2342
1569	Event suffers from high setup time as well (look at its code and you will	2343	Event suffers from high setup time as well (look at its code and you will
1570	understand why). Callback invocation also has a high overhead compared to	2344	understand why). Callback invocation also has a high overhead compared to
1571	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event	2345	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
1572	uses select or poll in basically all documented configurations.	2346	uses select or poll in basically all documented configurations.
…		…
1635	=item * C-based event loops perform very well with small number of	2409	=item * C-based event loops perform very well with small number of
1636	watchers, as the management overhead dominates.	2410	watchers, as the management overhead dominates.
1637		2411
1638	=back	2412	=back
1639		2413
		2414	=head2 THE IO::Lambda BENCHMARK
		2415
		2416	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2417	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2418	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2419	shouldn't come as a surprise to anybody). As such, the benchmark is
		2420	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2421	very optimal. But how would AnyEvent compare when used without the extra
		2422	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2423
		2424	The benchmark itself creates an echo-server, and then, for 500 times,
		2425	connects to the echo server, sends a line, waits for the reply, and then
		2426	creates the next connection. This is a rather bad benchmark, as it doesn't
		2427	test the efficiency of the framework or much non-blocking I/O, but it is a
		2428	benchmark nevertheless.
		2429
		2430	name runtime
		2431	Lambda/select 0.330 sec
		2432	+ optimized 0.122 sec
		2433	Lambda/AnyEvent 0.327 sec
		2434	+ optimized 0.138 sec
		2435	Raw sockets/select 0.077 sec
		2436	POE/select, components 0.662 sec
		2437	POE/select, raw sockets 0.226 sec
		2438	POE/select, optimized 0.404 sec
		2439
		2440	AnyEvent/select/nb 0.085 sec
		2441	AnyEvent/EV/nb 0.068 sec
		2442	+state machine 0.134 sec
		2443
		2444	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2445	benchmarks actually make blocking connects and use 100% blocking I/O,
		2446	defeating the purpose of an event-based solution. All of the newly
		2447	written AnyEvent benchmarks use 100% non-blocking connects (using
		2448	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2449	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2450	generally require a lot more bookkeeping and event handling than blocking
		2451	connects (which involve a single syscall only).
		2452
		2453	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2454	offers similar expressive power as POE and IO::Lambda, using conventional
		2455	Perl syntax. This means that both the echo server and the client are 100%
		2456	non-blocking, further placing it at a disadvantage.
		2457
		2458	As you can see, the AnyEvent + EV combination even beats the
		2459	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2460	backend easily beats IO::Lambda and POE.
		2461
		2462	And even the 100% non-blocking version written using the high-level (and
		2463	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda
		2464	higher level ("unoptimised") abstractions by a large margin, even though
		2465	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
		2466
		2467	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2468	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2469	part of the IO::Lambda distribution and were used without any changes.
		2470
		2471
		2472	=head1 SIGNALS
		2473
		2474	AnyEvent currently installs handlers for these signals:
		2475
		2476	=over 4
		2477
		2478	=item SIGCHLD
		2479
		2480	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2481	emulation for event loops that do not support them natively. Also, some
		2482	event loops install a similar handler.
		2483
		2484	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2485	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2486
		2487	=item SIGPIPE
		2488
		2489	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2490	when AnyEvent gets loaded.
		2491
		2492	The rationale for this is that AnyEvent users usually do not really depend
		2493	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2494	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2495	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2496	some random socket.
		2497
		2498	The rationale for installing a no-op handler as opposed to ignoring it is
		2499	that this way, the handler will be restored to defaults on exec.
		2500
		2501	Feel free to install your own handler, or reset it to defaults.
		2502
		2503	=back
		2504
		2505	=cut
		2506
		2507	undef $SIG{CHLD}
		2508	if $SIG{CHLD} eq 'IGNORE';
		2509
		2510	$SIG{PIPE} = sub { }
		2511	unless defined $SIG{PIPE};
		2512
		2513	=head1 RECOMMENDED/OPTIONAL MODULES
		2514
		2515	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2516	its built-in modules) are required to use it.
		2517
		2518	That does not mean that AnyEvent won't take advantage of some additional
		2519	modules if they are installed.
		2520
		2521	This section explains which additional modules will be used, and how they
		2522	affect AnyEvent's operation.
		2523
		2524	=over 4
		2525
		2526	=item L<Async::Interrupt>
		2527
		2528	This slightly arcane module is used to implement fast signal handling: To
		2529	my knowledge, there is no way to do completely race-free and quick
		2530	signal handling in pure perl. To ensure that signals still get
		2531	delivered, AnyEvent will start an interval timer to wake up perl (and
		2532	catch the signals) with some delay (default is 10 seconds, look for
		2533	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2534
		2535	If this module is available, then it will be used to implement signal
		2536	catching, which means that signals will not be delayed, and the event loop
		2537	will not be interrupted regularly, which is more efficient (and good for
		2538	battery life on laptops).
		2539
		2540	This affects not just the pure-perl event loop, but also other event loops
		2541	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2542
		2543	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2544	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2545	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2546	does nothing for those backends.
		2547
		2548	=item L<EV>
		2549
		2550	This module isn't really "optional", as it is simply one of the backend
		2551	event loops that AnyEvent can use. However, it is simply the best event
		2552	loop available in terms of features, speed and stability: It supports
		2553	the AnyEvent API optimally, implements all the watcher types in XS, does
		2554	automatic timer adjustments even when no monotonic clock is available,
		2555	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2556	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2557	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2558
		2559	If you only use backends that rely on another event loop (e.g. C<Tk>),
		2560	then this module will do nothing for you.
		2561
		2562	=item L<Guard>
		2563
		2564	The guard module, when used, will be used to implement
		2565	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2566	lot less memory), but otherwise doesn't affect guard operation much. It is
		2567	purely used for performance.
		2568
		2569	=item L<JSON> and L<JSON::XS>
		2570
		2571	One of these modules is required when you want to read or write JSON data
		2572	via L<AnyEvent::Handle>. L<JSON> is also written in pure-perl, but can take
		2573	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2574
		2575	=item L<Net::SSLeay>
		2576
		2577	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2578	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2579	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2580
		2581	=item L<Time::HiRes>
		2582
		2583	This module is part of perl since release 5.008. It will be used when the
		2584	chosen event library does not come with a timing source of its own. The
		2585	pure-perl event loop (L<AnyEvent::Impl::Perl>) will additionally use it to
		2586	try to use a monotonic clock for timing stability.
		2587
		2588	=back
		2589
1640		2590
1641	=head1 FORK	2591	=head1 FORK
1642		2592
1643	Most event libraries are not fork-safe. The ones who are usually are	2593	Most event libraries are not fork-safe. The ones who are usually are
1644	because they rely on inefficient but fork-safe C<select> or C<poll>	2594	because they rely on inefficient but fork-safe C<select> or C<poll> calls
1645	calls. Only L<EV> is fully fork-aware.	2595	- higher performance APIs such as BSD's kqueue or the dreaded Linux epoll
		2596	are usually badly thought-out hacks that are incompatible with fork in
		2597	one way or another. Only L<EV> is fully fork-aware and ensures that you
		2598	continue event-processing in both parent and child (or both, if you know
		2599	what you are doing).
		2600
		2601	This means that, in general, you cannot fork and do event processing in
		2602	the child if the event library was initialised before the fork (which
		2603	usually happens when the first AnyEvent watcher is created, or the library
		2604	is loaded).
1646		2605
1647	If you have to fork, you must either do so I<before> creating your first	2606	If you have to fork, you must either do so I<before> creating your first
1648	watcher OR you must not use AnyEvent at all in the child.	2607	watcher OR you must not use AnyEvent at all in the child OR you must do
		2608	something completely out of the scope of AnyEvent.
		2609
		2610	The problem of doing event processing in the parent I<and> the child
		2611	is much more complicated: even for backends that I<are> fork-aware or
		2612	fork-safe, their behaviour is not usually what you want: fork clones all
		2613	watchers, that means all timers, I/O watchers etc. are active in both
		2614	parent and child, which is almost never what you want. USing C<exec>
		2615	to start worker children from some kind of manage rprocess is usually
		2616	preferred, because it is much easier and cleaner, at the expense of having
		2617	to have another binary.
1649		2618
1650		2619
1651	=head1 SECURITY CONSIDERATIONS	2620	=head1 SECURITY CONSIDERATIONS
1652		2621
1653	AnyEvent can be forced to load any event model via	2622	AnyEvent can be forced to load any event model via
…		…
1664		2633
1665	use AnyEvent;	2634	use AnyEvent;
1666		2635
1667	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can	2636	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1668	be used to probe what backend is used and gain other information (which is	2637	be used to probe what backend is used and gain other information (which is
1669	probably even less useful to an attacker than PERL_ANYEVENT_MODEL).	2638	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2639	$ENV{PERL_ANYEVENT_STRICT}.
		2640
		2641	Note that AnyEvent will remove I<all> environment variables starting with
		2642	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2643	enabled.
		2644
		2645
		2646	=head1 BUGS
		2647
		2648	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2649	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2650	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2651	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2652	pronounced).
1670		2653
1671		2654
1672	=head1 SEE ALSO	2655	=head1 SEE ALSO
1673		2656
1674	Utility functions: L<AnyEvent::Util>.	2657	Utility functions: L<AnyEvent::Util>.
…		…
1677	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.	2660	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
1678		2661
1679	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,	2662	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
1680	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,	2663	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
1681	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,	2664	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1682	L<AnyEvent::Impl::POE>.	2665	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>, L<Anyevent::Impl::Irssi>.
1683		2666
1684	Non-blocking file handles, sockets, TCP clients and	2667	Non-blocking file handles, sockets, TCP clients and
1685	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>.	2668	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
1686		2669
1687	Asynchronous DNS: L<AnyEvent::DNS>.	2670	Asynchronous DNS: L<AnyEvent::DNS>.
1688		2671
1689	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,	2672	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>,
		2673	L<Coro::Event>,
1690		2674
1691	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>, L<AnyEvent::DNS>.	2675	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::XMPP>,
		2676	L<AnyEvent::HTTP>.
1692		2677
1693		2678
1694	=head1 AUTHOR	2679	=head1 AUTHOR
1695		2680
1696	Marc Lehmann <schmorp@schmorp.de>	2681	Marc Lehmann <schmorp@schmorp.de>

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