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Revision 1.180 by root, Sat Sep 6 07:00:45 2008 UTC vs.
Revision 1.419 by root, Thu Aug 28 15:26:20 2014 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, UV, Perl, Event::Lib, Irssi, rxvt-unicode, IO::Async,
		6	Qt, FLTK 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 { ... });
12		17
		18	# one-shot or repeating timers
13	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });	19	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
14	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...	20	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...);
15		21
16	print AnyEvent->now; # prints current event loop time	22	print AnyEvent->now; # prints current event loop time
17	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.	23	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
18		24
		25	# POSIX signal
19	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });	26	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
20		27
		28	# child process exit
21	my $w = AnyEvent->child (pid => $pid, cb => sub {	29	my $w = AnyEvent->child (pid => $pid, cb => sub {
22	my ($pid, $status) = @_;	30	my ($pid, $status) = @_;
23	...	31	...
24	});	32	});
		33
		34	# called when event loop idle (if applicable)
		35	my $w = AnyEvent->idle (cb => sub { ... });
25		36
26	my $w = AnyEvent->condvar; # stores whether a condition was flagged	37	my $w = AnyEvent->condvar; # stores whether a condition was flagged
27	$w->send; # wake up current and all future recv's	38	$w->send; # wake up current and all future recv's
28	$w->recv; # enters "main loop" till $condvar gets ->send	39	$w->recv; # enters "main loop" till $condvar gets ->send
29	# use a condvar in callback mode:	40	# use a condvar in callback mode:
…		…
32	=head1 INTRODUCTION/TUTORIAL	43	=head1 INTRODUCTION/TUTORIAL
33		44
34	This manpage is mainly a reference manual. If you are interested	45	This manpage is mainly a reference manual. If you are interested
35	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
36	L<AnyEvent::Intro> manpage.	47	L<AnyEvent::Intro> manpage.
		48
		49	=head1 SUPPORT
		50
		51	An FAQ document is available as L<AnyEvent::FAQ>.
		52
		53	There also is a mailinglist for discussing all things AnyEvent, and an IRC
		54	channel, too.
		55
		56	See the AnyEvent project page at the B<Schmorpforge Ta-Sa Software
		57	Repository>, at L<http://anyevent.schmorp.de>, for more info.
37		58
38	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)	59	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
39		60
40	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	61	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
41	nowadays. So what is different about AnyEvent?	62	nowadays. So what is different about AnyEvent?
…		…
57	module users into the same thing by forcing them to use the same event	78	module users into the same thing by forcing them to use the same event
58	model you use.	79	model you use.
59		80
60	For modules like POE or IO::Async (which is a total misnomer as it is	81	For modules like POE or IO::Async (which is a total misnomer as it is
61	actually doing all I/O I<synchronously>...), using them in your module is	82	actually doing all I/O I<synchronously>...), using them in your module is
62	like joining a cult: After you joined, you are dependent on them and you	83	like joining a cult: After you join, you are dependent on them and you
63	cannot use anything else, as they are simply incompatible to everything	84	cannot use anything else, as they are simply incompatible to everything
64	that isn't them. What's worse, all the potential users of your	85	that isn't them. What's worse, all the potential users of your
65	module are I<also> forced to use the same event loop you use.	86	module are I<also> forced to use the same event loop you use.
66		87
67	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	88	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
68	fine. AnyEvent + Tk works fine etc. etc. but none of these work together	89	fine. AnyEvent + Tk works fine etc. etc. but none of these work together
69	with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if	90	with the rest: POE + EV? No go. Tk + Event? No go. Again: if your module
70	your module uses one of those, every user of your module has to use it,	91	uses one of those, every user of your module has to use it, too. But if
71	too. But if your module uses AnyEvent, it works transparently with all	92	your module uses AnyEvent, it works transparently with all event models it
72	event models it supports (including stuff like IO::Async, as long as those	93	supports (including stuff like IO::Async, as long as those use one of the
73	use one of the supported event loops. It is trivial to add new event loops	94	supported event loops. It is easy to add new event loops to AnyEvent, too,
74	to AnyEvent, too, so it is future-proof).	95	so it is future-proof).
75		96
76	In addition to being free of having to use I<the one and only true event	97	In addition to being free of having to use I<the one and only true event
77	model>, AnyEvent also is free of bloat and policy: with POE or similar	98	model>, AnyEvent also is free of bloat and policy: with POE or similar
78	modules, you get an enormous amount of code and strict rules you have to	99	modules, you get an enormous amount of code and strict rules you have to
79	follow. AnyEvent, on the other hand, is lean and up to the point, by only	100	follow. AnyEvent, on the other hand, is lean and to the point, by only
80	offering the functionality that is necessary, in as thin as a wrapper as	101	offering the functionality that is necessary, in as thin as a wrapper as
81	technically possible.	102	technically possible.
82		103
83	Of course, AnyEvent comes with a big (and fully optional!) toolbox	104	Of course, AnyEvent comes with a big (and fully optional!) toolbox
84	of useful functionality, such as an asynchronous DNS resolver, 100%	105	of useful functionality, such as an asynchronous DNS resolver, 100%
…		…
90	useful) and you want to force your users to use the one and only event	111	useful) and you want to force your users to use the one and only event
91	model, you should I<not> use this module.	112	model, you should I<not> use this module.
92		113
93	=head1 DESCRIPTION	114	=head1 DESCRIPTION
94		115
95	L<AnyEvent> provides an identical interface to multiple event loops. This	116	L<AnyEvent> provides a uniform interface to various event loops. This
96	allows module authors to utilise an event loop without forcing module	117	allows module authors to use event loop functionality without forcing
97	users to use the same event loop (as only a single event loop can coexist	118	module users to use a specific event loop implementation (since more
98	peacefully at any one time).	119	than one event loop cannot coexist peacefully).
99		120
100	The interface itself is vaguely similar, but not identical to the L<Event>	121	The interface itself is vaguely similar, but not identical to the L<Event>
101	module.	122	module.
102		123
103	During the first call of any watcher-creation method, the module tries	124	During the first call of any watcher-creation method, the module tries
104	to detect the currently loaded event loop by probing whether one of the	125	to detect the currently loaded event loop by probing whether one of the
105	following modules is already loaded: L<EV>,	126	following modules is already loaded: L<EV>, L<AnyEvent::Loop>,
106	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,	127	L<Event>, L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>. The first one
107	L<POE>. The first one found is used. If none are found, the module tries	128	found is used. If none are detected, the module tries to load the first
108	to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl	129	four modules in the order given; but note that if L<EV> is not
109	adaptor should always succeed) in the order given. The first one that can	130	available, the pure-perl L<AnyEvent::Loop> should always work, so
110	be successfully loaded will be used. If, after this, still none could be	131	the other two are not normally tried.
111	found, AnyEvent will fall back to a pure-perl event loop, which is not
112	very efficient, but should work everywhere.
113		132
114	Because AnyEvent first checks for modules that are already loaded, loading	133	Because AnyEvent first checks for modules that are already loaded, loading
115	an event model explicitly before first using AnyEvent will likely make	134	an event model explicitly before first using AnyEvent will likely make
116	that model the default. For example:	135	that model the default. For example:
117		136
…		…
119	use AnyEvent;	138	use AnyEvent;
120		139
121	# .. AnyEvent will likely default to Tk	140	# .. AnyEvent will likely default to Tk
122		141
123	The I<likely> means that, if any module loads another event model and	142	The I<likely> means that, if any module loads another event model and
124	starts using it, all bets are off. Maybe you should tell their authors to	143	starts using it, all bets are off - this case should be very rare though,
125	use AnyEvent so their modules work together with others seamlessly...	144	as very few modules hardcode event loops without announcing this very
		145	loudly.
126		146
127	The pure-perl implementation of AnyEvent is called	147	The pure-perl implementation of AnyEvent is called C<AnyEvent::Loop>. Like
128	C<AnyEvent::Impl::Perl>. Like other event modules you can load it	148	other event modules you can load it explicitly and enjoy the high
129	explicitly and enjoy the high availability of that event loop :)	149	availability of that event loop :)
130		150
131	=head1 WATCHERS	151	=head1 WATCHERS
132		152
133	AnyEvent has the central concept of a I<watcher>, which is an object that	153	AnyEvent has the central concept of a I<watcher>, which is an object that
134	stores relevant data for each kind of event you are waiting for, such as	154	stores relevant data for each kind of event you are waiting for, such as
…		…
137	These watchers are normal Perl objects with normal Perl lifetime. After	157	These watchers are normal Perl objects with normal Perl lifetime. After
138	creating a watcher it will immediately "watch" for events and invoke the	158	creating a watcher it will immediately "watch" for events and invoke the
139	callback when the event occurs (of course, only when the event model	159	callback when the event occurs (of course, only when the event model
140	is in control).	160	is in control).
141		161
		162	Note that B<callbacks must not permanently change global variables>
		163	potentially in use by the event loop (such as C<$_> or C<$[>) and that B<<
		164	callbacks must not C<die> >>. The former is good programming practice in
		165	Perl and the latter stems from the fact that exception handling differs
		166	widely between event loops.
		167
142	To disable the watcher you have to destroy it (e.g. by setting the	168	To disable a watcher you have to destroy it (e.g. by setting the
143	variable you store it in to C<undef> or otherwise deleting all references	169	variable you store it in to C<undef> or otherwise deleting all references
144	to it).	170	to it).
145		171
146	All watchers are created by calling a method on the C<AnyEvent> class.	172	All watchers are created by calling a method on the C<AnyEvent> class.
147		173
148	Many watchers either are used with "recursion" (repeating timers for	174	Many watchers either are used with "recursion" (repeating timers for
149	example), or need to refer to their watcher object in other ways.	175	example), or need to refer to their watcher object in other ways.
150		176
151	An any way to achieve that is this pattern:	177	One way to achieve that is this pattern:
152		178
153	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	179	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
154	# you can use $w here, for example to undef it	180	# you can use $w here, for example to undef it
155	undef $w;	181	undef $w;
156	});	182	});
…		…
159	my variables are only visible after the statement in which they are	185	my variables are only visible after the statement in which they are
160	declared.	186	declared.
161		187
162	=head2 I/O WATCHERS	188	=head2 I/O WATCHERS
163		189
		190	$w = AnyEvent->io (
		191	fh => <filehandle_or_fileno>,
		192	poll => <"r" or "w">,
		193	cb => <callback>,
		194	);
		195
164	You can create an I/O watcher by calling the C<< AnyEvent->io >> method	196	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
165	with the following mandatory key-value pairs as arguments:	197	with the following mandatory key-value pairs as arguments:
166		198
167	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch for events	199	C<fh> is the Perl I<file handle> (or a naked file descriptor) to watch
168	(AnyEvent might or might not keep a reference to this file handle). C<poll>	200	for events (AnyEvent might or might not keep a reference to this file
		201	handle). Note that only file handles pointing to things for which
		202	non-blocking operation makes sense are allowed. This includes sockets,
		203	most character devices, pipes, fifos and so on, but not for example files
		204	or block devices.
		205
169	must be a string that is either C<r> or C<w>, which creates a watcher	206	C<poll> must be a string that is either C<r> or C<w>, which creates a
170	waiting for "r"eadable or "w"ritable events, respectively. C<cb> is the	207	watcher waiting for "r"eadable or "w"ritable events, respectively.
		208
171	callback to invoke each time the file handle becomes ready.	209	C<cb> is the callback to invoke each time the file handle becomes ready.
172		210
173	Although the callback might get passed parameters, their value and	211	Although the callback might get passed parameters, their value and
174	presence is undefined and you cannot rely on them. Portable AnyEvent	212	presence is undefined and you cannot rely on them. Portable AnyEvent
175	callbacks cannot use arguments passed to I/O watcher callbacks.	213	callbacks cannot use arguments passed to I/O watcher callbacks.
176		214
177	The I/O watcher might use the underlying file descriptor or a copy of it.	215	The I/O watcher might use the underlying file descriptor or a copy of it.
178	You must not close a file handle as long as any watcher is active on the	216	You must not close a file handle as long as any watcher is active on the
179	underlying file descriptor.	217	underlying file descriptor.
180		218
181	Some event loops issue spurious readyness notifications, so you should	219	Some event loops issue spurious readiness notifications, so you should
182	always use non-blocking calls when reading/writing from/to your file	220	always use non-blocking calls when reading/writing from/to your file
183	handles.	221	handles.
184		222
185	Example: wait for readability of STDIN, then read a line and disable the	223	Example: wait for readability of STDIN, then read a line and disable the
186	watcher.	224	watcher.
…		…
191	undef $w;	229	undef $w;
192	});	230	});
193		231
194	=head2 TIME WATCHERS	232	=head2 TIME WATCHERS
195		233
		234	$w = AnyEvent->timer (after => <seconds>, cb => <callback>);
		235
		236	$w = AnyEvent->timer (
		237	after => <fractional_seconds>,
		238	interval => <fractional_seconds>,
		239	cb => <callback>,
		240	);
		241
196	You can create a time watcher by calling the C<< AnyEvent->timer >>	242	You can create a time watcher by calling the C<< AnyEvent->timer >>
197	method with the following mandatory arguments:	243	method with the following mandatory arguments:
198		244
199	C<after> specifies after how many seconds (fractional values are	245	C<after> specifies after how many seconds (fractional values are
200	supported) the callback should be invoked. C<cb> is the callback to invoke	246	supported) the callback should be invoked. C<cb> is the callback to invoke
…		…
202		248
203	Although the callback might get passed parameters, their value and	249	Although the callback might get passed parameters, their value and
204	presence is undefined and you cannot rely on them. Portable AnyEvent	250	presence is undefined and you cannot rely on them. Portable AnyEvent
205	callbacks cannot use arguments passed to time watcher callbacks.	251	callbacks cannot use arguments passed to time watcher callbacks.
206		252
207	The callback will normally be invoked once only. If you specify another	253	The callback will normally be invoked only once. If you specify another
208	parameter, C<interval>, as a strictly positive number (> 0), then the	254	parameter, C<interval>, as a strictly positive number (> 0), then the
209	callback will be invoked regularly at that interval (in fractional	255	callback will be invoked regularly at that interval (in fractional
210	seconds) after the first invocation. If C<interval> is specified with a	256	seconds) after the first invocation. If C<interval> is specified with a
211	false value, then it is treated as if it were missing.	257	false value, then it is treated as if it were not specified at all.
212		258
213	The callback will be rescheduled before invoking the callback, but no	259	The callback will be rescheduled before invoking the callback, but no
214	attempt is done to avoid timer drift in most backends, so the interval is	260	attempt is made to avoid timer drift in most backends, so the interval is
215	only approximate.	261	only approximate.
216		262
217	Example: fire an event after 7.7 seconds.	263	Example: fire an event after 7.7 seconds.
218		264
219	my $w = AnyEvent->timer (after => 7.7, cb => sub {	265	my $w = AnyEvent->timer (after => 7.7, cb => sub {
…		…
225		271
226	Example 2: fire an event after 0.5 seconds, then roughly every second.	272	Example 2: fire an event after 0.5 seconds, then roughly every second.
227		273
228	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {	274	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
229	warn "timeout\n";	275	warn "timeout\n";
230	};	276	});
231		277
232	=head3 TIMING ISSUES	278	=head3 TIMING ISSUES
233		279
234	There are two ways to handle timers: based on real time (relative, "fire	280	There are two ways to handle timers: based on real time (relative, "fire
235	in 10 seconds") and based on wallclock time (absolute, "fire at 12	281	in 10 seconds") and based on wallclock time (absolute, "fire at 12
…		…
237		283
238	While most event loops expect timers to specified in a relative way, they	284	While most event loops expect timers to specified in a relative way, they
239	use absolute time internally. This makes a difference when your clock	285	use absolute time internally. This makes a difference when your clock
240	"jumps", for example, when ntp decides to set your clock backwards from	286	"jumps", for example, when ntp decides to set your clock backwards from
241	the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to	287	the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to
242	fire "after" a second might actually take six years to finally fire.	288	fire "after a second" might actually take six years to finally fire.
243		289
244	AnyEvent cannot compensate for this. The only event loop that is conscious	290	AnyEvent cannot compensate for this. The only event loop that is conscious
245	about these issues is L<EV>, which offers both relative (ev_timer, based	291	of these issues is L<EV>, which offers both relative (ev_timer, based
246	on true relative time) and absolute (ev_periodic, based on wallclock time)	292	on true relative time) and absolute (ev_periodic, based on wallclock time)
247	timers.	293	timers.
248		294
249	AnyEvent always prefers relative timers, if available, matching the	295	AnyEvent always prefers relative timers, if available, matching the
250	AnyEvent API.	296	AnyEvent API.
…		…
272	I<In almost all cases (in all cases if you don't care), this is the	318	I<In almost all cases (in all cases if you don't care), this is the
273	function to call when you want to know the current time.>	319	function to call when you want to know the current time.>
274		320
275	This function is also often faster then C<< AnyEvent->time >>, and	321	This function is also often faster then C<< AnyEvent->time >>, and
276	thus the preferred method if you want some timestamp (for example,	322	thus the preferred method if you want some timestamp (for example,
277	L<AnyEvent::Handle> uses this to update it's activity timeouts).	323	L<AnyEvent::Handle> uses this to update its activity timeouts).
278		324
279	The rest of this section is only of relevance if you try to be very exact	325	The rest of this section is only of relevance if you try to be very exact
280	with your timing, you can skip it without bad conscience.	326	with your timing; you can skip it without a bad conscience.
281		327
282	For a practical example of when these times differ, consider L<Event::Lib>	328	For a practical example of when these times differ, consider L<Event::Lib>
283	and L<EV> and the following set-up:	329	and L<EV> and the following set-up:
284		330
285	The event loop is running and has just invoked one of your callback at	331	The event loop is running and has just invoked one of your callbacks at
286	time=500 (assume no other callbacks delay processing). In your callback,	332	time=500 (assume no other callbacks delay processing). In your callback,
287	you wait a second by executing C<sleep 1> (blocking the process for a	333	you wait a second by executing C<sleep 1> (blocking the process for a
288	second) and then (at time=501) you create a relative timer that fires	334	second) and then (at time=501) you create a relative timer that fires
289	after three seconds.	335	after three seconds.
290		336
…		…
308	In either case, if you care (and in most cases, you don't), then you	354	In either case, if you care (and in most cases, you don't), then you
309	can get whatever behaviour you want with any event loop, by taking the	355	can get whatever behaviour you want with any event loop, by taking the
310	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into	356	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
311	account.	357	account.
312		358
		359	=item AnyEvent->now_update
		360
		361	Some event loops (such as L<EV> or L<AnyEvent::Loop>) cache the current
		362	time for each loop iteration (see the discussion of L<< AnyEvent->now >>,
		363	above).
		364
		365	When a callback runs for a long time (or when the process sleeps), then
		366	this "current" time will differ substantially from the real time, which
		367	might affect timers and time-outs.
		368
		369	When this is the case, you can call this method, which will update the
		370	event loop's idea of "current time".
		371
		372	A typical example would be a script in a web server (e.g. C<mod_perl>) -
		373	when mod_perl executes the script, then the event loop will have the wrong
		374	idea about the "current time" (being potentially far in the past, when the
		375	script ran the last time). In that case you should arrange a call to C<<
		376	AnyEvent->now_update >> each time the web server process wakes up again
		377	(e.g. at the start of your script, or in a handler).
		378
		379	Note that updating the time I<might> cause some events to be handled.
		380
313	=back	381	=back
314		382
315	=head2 SIGNAL WATCHERS	383	=head2 SIGNAL WATCHERS
		384
		385	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
316		386
317	You can watch for signals using a signal watcher, C<signal> is the signal	387	You can watch for signals using a signal watcher, C<signal> is the signal
318	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl	388	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
319	callback to be invoked whenever a signal occurs.	389	callback to be invoked whenever a signal occurs.
320		390
…		…
326	invocation, and callback invocation will be synchronous. Synchronous means	396	invocation, and callback invocation will be synchronous. Synchronous means
327	that it might take a while until the signal gets handled by the process,	397	that it might take a while until the signal gets handled by the process,
328	but it is guaranteed not to interrupt any other callbacks.	398	but it is guaranteed not to interrupt any other callbacks.
329		399
330	The main advantage of using these watchers is that you can share a signal	400	The main advantage of using these watchers is that you can share a signal
331	between multiple watchers.	401	between multiple watchers, and AnyEvent will ensure that signals will not
		402	interrupt your program at bad times.
332		403
333	This watcher might use C<%SIG>, so programs overwriting those signals	404	This watcher might use C<%SIG> (depending on the event loop used),
334	directly will likely not work correctly.	405	so programs overwriting those signals directly will likely not work
		406	correctly.
335		407
336	Example: exit on SIGINT	408	Example: exit on SIGINT
337		409
338	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	410	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
339		411
		412	=head3 Restart Behaviour
		413
		414	While restart behaviour is up to the event loop implementation, most will
		415	not restart syscalls (that includes L<Async::Interrupt> and AnyEvent's
		416	pure perl implementation).
		417
		418	=head3 Safe/Unsafe Signals
		419
		420	Perl signals can be either "safe" (synchronous to opcode handling)
		421	or "unsafe" (asynchronous) - the former might delay signal delivery
		422	indefinitely, the latter might corrupt your memory.
		423
		424	AnyEvent signal handlers are, in addition, synchronous to the event loop,
		425	i.e. they will not interrupt your running perl program but will only be
		426	called as part of the normal event handling (just like timer, I/O etc.
		427	callbacks, too).
		428
		429	=head3 Signal Races, Delays and Workarounds
		430
		431	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support
		432	attaching callbacks to signals in a generic way, which is a pity,
		433	as you cannot do race-free signal handling in perl, requiring
		434	C libraries for this. AnyEvent will try to do its best, which
		435	means in some cases, signals will be delayed. The maximum time
		436	a signal might be delayed is 10 seconds by default, but can
		437	be overriden via C<$ENV{PERL_ANYEVENT_MAX_SIGNAL_LATENCY}> or
		438	C<$AnyEvent::MAX_SIGNAL_LATENCY> - see the L<ENVIRONMENT VARIABLES>
		439	section for details.
		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). For those, you just have to suffer the
		445	delays.
		446
340	=head2 CHILD PROCESS WATCHERS	447	=head2 CHILD PROCESS WATCHERS
341		448
		449	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		450
342	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.
343		452
344	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,
345	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
346	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
347	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
348	and exit status (as returned by waitpid), so unlike other watcher types,	457	(stopped/continued).
349	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).
350		467
351	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
352	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
353	have exited already (and no SIGCHLD will be sent anymore).	470	have exited already (and no SIGCHLD will be sent anymore).
354		471
355	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
356	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
357	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.
358		478
359	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
360	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
361	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 case the latency and race
		486	problems mentioned in the description of signal watchers apply.
362		487
363	Example: fork a process and wait for it	488	Example: fork a process and wait for it
364		489
365	my $done = AnyEvent->condvar;	490	my $done = AnyEvent->condvar;
366		491
		492	# this forks and immediately calls exit in the child. this
		493	# normally has all sorts of bad consequences for your parent,
		494	# so take this as an example only. always fork and exec,
		495	# or call POSIX::_exit, in real code.
367	my $pid = fork or exit 5;	496	my $pid = fork or exit 5;
368		497
369	my $w = AnyEvent->child (	498	my $w = AnyEvent->child (
370	pid => $pid,	499	pid => $pid,
371	cb => sub {	500	cb => sub {
…		…
376	);	505	);
377		506
378	# do something else, then wait for process exit	507	# do something else, then wait for process exit
379	$done->recv;	508	$done->recv;
380		509
		510	=head2 IDLE WATCHERS
		511
		512	$w = AnyEvent->idle (cb => <callback>);
		513
		514	This will repeatedly invoke the callback after the process becomes idle,
		515	until either the watcher is destroyed or new events have been detected.
		516
		517	Idle watchers are useful when there is a need to do something, but it
		518	is not so important (or wise) to do it instantly. The callback will be
		519	invoked only when there is "nothing better to do", which is usually
		520	defined as "all outstanding events have been handled and no new events
		521	have been detected". That means that idle watchers ideally get invoked
		522	when the event loop has just polled for new events but none have been
		523	detected. Instead of blocking to wait for more events, the idle watchers
		524	will be invoked.
		525
		526	Unfortunately, most event loops do not really support idle watchers (only
		527	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		528	will simply call the callback "from time to time".
		529
		530	Example: read lines from STDIN, but only process them when the
		531	program is otherwise idle:
		532
		533	my @lines; # read data
		534	my $idle_w;
		535	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		536	push @lines, scalar <STDIN>;
		537
		538	# start an idle watcher, if not already done
		539	$idle_w ||= AnyEvent->idle (cb => sub {
		540	# handle only one line, when there are lines left
		541	if (my $line = shift @lines) {
		542	print "handled when idle: $line";
		543	} else {
		544	# otherwise disable the idle watcher again
		545	undef $idle_w;
		546	}
		547	});
		548	});
		549
381	=head2 CONDITION VARIABLES	550	=head2 CONDITION VARIABLES
		551
		552	$cv = AnyEvent->condvar;
		553
		554	$cv->send (<list>);
		555	my @res = $cv->recv;
382		556
383	If you are familiar with some event loops you will know that all of them	557	If you are familiar with some event loops you will know that all of them
384	require you to run some blocking "loop", "run" or similar function that	558	require you to run some blocking "loop", "run" or similar function that
385	will actively watch for new events and call your callbacks.	559	will actively watch for new events and call your callbacks.
386		560
387	AnyEvent is different, it expects somebody else to run the event loop and	561	AnyEvent is slightly different: it expects somebody else to run the event
388	will only block when necessary (usually when told by the user).	562	loop and will only block when necessary (usually when told by the user).
389		563
390	The instrument to do that is called a "condition variable", so called	564	The tool to do that is called a "condition variable", so called because
391	because they represent a condition that must become true.	565	they represent a condition that must become true.
		566
		567	Now is probably a good time to look at the examples further below.
392		568
393	Condition variables can be created by calling the C<< AnyEvent->condvar	569	Condition variables can be created by calling the C<< AnyEvent->condvar
394	>> method, usually without arguments. The only argument pair allowed is	570	>> method, usually without arguments. The only argument pair allowed is
395
396	C<cb>, which specifies a callback to be called when the condition variable	571	C<cb>, which specifies a callback to be called when the condition variable
397	becomes true, with the condition variable as the first argument (but not	572	becomes true, with the condition variable as the first argument (but not
398	the results).	573	the results).
399		574
400	After creation, the condition variable is "false" until it becomes "true"	575	After creation, the condition variable is "false" until it becomes "true"
401	by calling the C<send> method (or calling the condition variable as if it	576	by calling the C<send> method (or calling the condition variable as if it
402	were a callback, read about the caveats in the description for the C<<	577	were a callback, read about the caveats in the description for the C<<
403	->send >> method).	578	->send >> method).
404		579
405	Condition variables are similar to callbacks, except that you can	580	Since condition variables are the most complex part of the AnyEvent API, here are
406	optionally wait for them. They can also be called merge points - points	581	some different mental models of what they are - pick the ones you can connect to:
407	in time where multiple outstanding events have been processed. And yet	582
408	another way to call them is transactions - each condition variable can be	583	=over 4
409	used to represent a transaction, which finishes at some point and delivers	584
410	a result.	585	=item * Condition variables are like callbacks - you can call them (and pass them instead
		586	of callbacks). Unlike callbacks however, you can also wait for them to be called.
		587
		588	=item * Condition variables are signals - one side can emit or send them,
		589	the other side can wait for them, or install a handler that is called when
		590	the signal fires.
		591
		592	=item * Condition variables are like "Merge Points" - points in your program
		593	where you merge multiple independent results/control flows into one.
		594
		595	=item * Condition variables represent a transaction - functions that start
		596	some kind of transaction can return them, leaving the caller the choice
		597	between waiting in a blocking fashion, or setting a callback.
		598
		599	=item * Condition variables represent future values, or promises to deliver
		600	some result, long before the result is available.
		601
		602	=back
411		603
412	Condition variables are very useful to signal that something has finished,	604	Condition variables are very useful to signal that something has finished,
413	for example, if you write a module that does asynchronous http requests,	605	for example, if you write a module that does asynchronous http requests,
414	then a condition variable would be the ideal candidate to signal the	606	then a condition variable would be the ideal candidate to signal the
415	availability of results. The user can either act when the callback is	607	availability of results. The user can either act when the callback is
…		…
428		620
429	Condition variables are represented by hash refs in perl, and the keys	621	Condition variables are represented by hash refs in perl, and the keys
430	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing	622	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
431	easy (it is often useful to build your own transaction class on top of	623	easy (it is often useful to build your own transaction class on top of
432	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call	624	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
433	it's C<new> method in your own C<new> method.	625	its C<new> method in your own C<new> method.
434		626
435	There are two "sides" to a condition variable - the "producer side" which	627	There are two "sides" to a condition variable - the "producer side" which
436	eventually calls C<< -> send >>, and the "consumer side", which waits	628	eventually calls C<< -> send >>, and the "consumer side", which waits
437	for the send to occur.	629	for the send to occur.
438		630
439	Example: wait for a timer.	631	Example: wait for a timer.
440		632
441	# wait till the result is ready	633	# condition: "wait till the timer is fired"
442	my $result_ready = AnyEvent->condvar;	634	my $timer_fired = AnyEvent->condvar;
443		635
444	# do something such as adding a timer	636	# create the timer - we could wait for, say
445	# or socket watcher the calls $result_ready->send	637	# a handle becomign ready, or even an
446	# when the "result" is ready.	638	# AnyEvent::HTTP request to finish, but
447	# in this case, we simply use a timer:	639	# in this case, we simply use a timer:
448	my $w = AnyEvent->timer (	640	my $w = AnyEvent->timer (
449	after => 1,	641	after => 1,
450	cb => sub { $result_ready->send },	642	cb => sub { $timer_fired->send },
451	);	643	);
452		644
453	# this "blocks" (while handling events) till the callback	645	# this "blocks" (while handling events) till the callback
454	# calls send	646	# calls ->send
455	$result_ready->recv;	647	$timer_fired->recv;
456		648
457	Example: wait for a timer, but take advantage of the fact that	649	Example: wait for a timer, but take advantage of the fact that condition
458	condition variables are also code references.	650	variables are also callable directly.
459		651
460	my $done = AnyEvent->condvar;	652	my $done = AnyEvent->condvar;
461	my $delay = AnyEvent->timer (after => 5, cb => $done);	653	my $delay = AnyEvent->timer (after => 5, cb => $done);
462	$done->recv;	654	$done->recv;
463		655
…		…
469		661
470	...	662	...
471		663
472	my @info = $couchdb->info->recv;	664	my @info = $couchdb->info->recv;
473		665
474	And this is how you would just ste a callback to be called whenever the	666	And this is how you would just set a callback to be called whenever the
475	results are available:	667	results are available:
476		668
477	$couchdb->info->cb (sub {	669	$couchdb->info->cb (sub {
478	my @info = $_[0]->recv;	670	my @info = $_[0]->recv;
479	});	671	});
…		…
497	immediately from within send.	689	immediately from within send.
498		690
499	Any arguments passed to the C<send> call will be returned by all	691	Any arguments passed to the C<send> call will be returned by all
500	future C<< ->recv >> calls.	692	future C<< ->recv >> calls.
501		693
502	Condition variables are overloaded so one can call them directly	694	Condition variables are overloaded so one can call them directly (as if
503	(as a code reference). Calling them directly is the same as calling	695	they were a code reference). Calling them directly is the same as calling
504	C<send>. Note, however, that many C-based event loops do not handle	696	C<send>.
505	overloading, so as tempting as it may be, passing a condition variable
506	instead of a callback does not work. Both the pure perl and EV loops
507	support overloading, however, as well as all functions that use perl to
508	invoke a callback (as in L<AnyEvent::Socket> and L<AnyEvent::DNS> for
509	example).
510		697
511	=item $cv->croak ($error)	698	=item $cv->croak ($error)
512		699
513	Similar to send, but causes all call's to C<< ->recv >> to invoke	700	Similar to send, but causes all calls to C<< ->recv >> to invoke
514	C<Carp::croak> with the given error message/object/scalar.	701	C<Carp::croak> with the given error message/object/scalar.
515		702
516	This can be used to signal any errors to the condition variable	703	This can be used to signal any errors to the condition variable
517	user/consumer.	704	user/consumer. Doing it this way instead of calling C<croak> directly
		705	delays the error detection, but has the overwhelming advantage that it
		706	diagnoses the error at the place where the result is expected, and not
		707	deep in some event callback with no connection to the actual code causing
		708	the problem.
518		709
519	=item $cv->begin ([group callback])	710	=item $cv->begin ([group callback])
520		711
521	=item $cv->end	712	=item $cv->end
522
523	These two methods are EXPERIMENTAL and MIGHT CHANGE.
524		713
525	These two methods can be used to combine many transactions/events into	714	These two methods can be used to combine many transactions/events into
526	one. For example, a function that pings many hosts in parallel might want	715	one. For example, a function that pings many hosts in parallel might want
527	to use a condition variable for the whole process.	716	to use a condition variable for the whole process.
528		717
529	Every call to C<< ->begin >> will increment a counter, and every call to	718	Every call to C<< ->begin >> will increment a counter, and every call to
530	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end	719	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
531	>>, the (last) callback passed to C<begin> will be executed. That callback	720	>>, the (last) callback passed to C<begin> will be executed, passing the
532	is I<supposed> to call C<< ->send >>, but that is not required. If no	721	condvar as first argument. That callback is I<supposed> to call C<< ->send
533	callback was set, C<send> will be called without any arguments.	722	>>, but that is not required. If no group callback was set, C<send> will
		723	be called without any arguments.
534		724
535	Let's clarify this with the ping example:	725	You can think of C<< $cv->send >> giving you an OR condition (one call
		726	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		727	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		728
		729	Let's start with a simple example: you have two I/O watchers (for example,
		730	STDOUT and STDERR for a program), and you want to wait for both streams to
		731	close before activating a condvar:
536		732
537	my $cv = AnyEvent->condvar;	733	my $cv = AnyEvent->condvar;
538		734
		735	$cv->begin; # first watcher
		736	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		737	defined sysread $fh1, my $buf, 4096
		738	or $cv->end;
		739	});
		740
		741	$cv->begin; # second watcher
		742	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		743	defined sysread $fh2, my $buf, 4096
		744	or $cv->end;
		745	});
		746
		747	$cv->recv;
		748
		749	This works because for every event source (EOF on file handle), there is
		750	one call to C<begin>, so the condvar waits for all calls to C<end> before
		751	sending.
		752
		753	The ping example mentioned above is slightly more complicated, as the
		754	there are results to be passed back, and the number of tasks that are
		755	begun can potentially be zero:
		756
		757	my $cv = AnyEvent->condvar;
		758
539	my %result;	759	my %result;
540	$cv->begin (sub { $cv->send (\%result) });	760	$cv->begin (sub { shift->send (\%result) });
541		761
542	for my $host (@list_of_hosts) {	762	for my $host (@list_of_hosts) {
543	$cv->begin;	763	$cv->begin;
544	ping_host_then_call_callback $host, sub {	764	ping_host_then_call_callback $host, sub {
545	$result{$host} = ...;	765	$result{$host} = ...;
…		…
547	};	767	};
548	}	768	}
549		769
550	$cv->end;	770	$cv->end;
551		771
		772	...
		773
		774	my $results = $cv->recv;
		775
552	This code fragment supposedly pings a number of hosts and calls	776	This code fragment supposedly pings a number of hosts and calls
553	C<send> after results for all then have have been gathered - in any	777	C<send> after results for all then have have been gathered - in any
554	order. To achieve this, the code issues a call to C<begin> when it starts	778	order. To achieve this, the code issues a call to C<begin> when it starts
555	each ping request and calls C<end> when it has received some result for	779	each ping request and calls C<end> when it has received some result for
556	it. Since C<begin> and C<end> only maintain a counter, the order in which	780	it. Since C<begin> and C<end> only maintain a counter, the order in which
…		…
560	loop, which serves two important purposes: first, it sets the callback	784	loop, which serves two important purposes: first, it sets the callback
561	to be called once the counter reaches C<0>, and second, it ensures that	785	to be called once the counter reaches C<0>, and second, it ensures that
562	C<send> is called even when C<no> hosts are being pinged (the loop	786	C<send> is called even when C<no> hosts are being pinged (the loop
563	doesn't execute once).	787	doesn't execute once).
564		788
565	This is the general pattern when you "fan out" into multiple subrequests:	789	This is the general pattern when you "fan out" into multiple (but
566	use an outer C<begin>/C<end> pair to set the callback and ensure C<end>	790	potentially zero) subrequests: use an outer C<begin>/C<end> pair to set
567	is called at least once, and then, for each subrequest you start, call	791	the callback and ensure C<end> is called at least once, and then, for each
568	C<begin> and for each subrequest you finish, call C<end>.	792	subrequest you start, call C<begin> and for each subrequest you finish,
		793	call C<end>.
569		794
570	=back	795	=back
571		796
572	=head3 METHODS FOR CONSUMERS	797	=head3 METHODS FOR CONSUMERS
573		798
…		…
577	=over 4	802	=over 4
578		803
579	=item $cv->recv	804	=item $cv->recv
580		805
581	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak	806	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
582	>> methods have been called on c<$cv>, while servicing other watchers	807	>> methods have been called on C<$cv>, while servicing other watchers
583	normally.	808	normally.
584		809
585	You can only wait once on a condition - additional calls are valid but	810	You can only wait once on a condition - additional calls are valid but
586	will return immediately.	811	will return immediately.
587		812
…		…
589	function will call C<croak>.	814	function will call C<croak>.
590		815
591	In list context, all parameters passed to C<send> will be returned,	816	In list context, all parameters passed to C<send> will be returned,
592	in scalar context only the first one will be returned.	817	in scalar context only the first one will be returned.
593		818
		819	Note that doing a blocking wait in a callback is not supported by any
		820	event loop, that is, recursive invocation of a blocking C<< ->recv >> is
		821	not allowed and the C<recv> call will C<croak> if such a condition is
		822	detected. This requirement can be dropped by relying on L<Coro::AnyEvent>
		823	, which allows you to do a blocking C<< ->recv >> from any thread
		824	that doesn't run the event loop itself. L<Coro::AnyEvent> is loaded
		825	automatically when L<Coro> is used with L<AnyEvent>, so code does not need
		826	to do anything special to take advantage of that: any code that would
		827	normally block your program because it calls C<recv>, be executed in an
		828	C<async> thread instead without blocking other threads.
		829
594	Not all event models support a blocking wait - some die in that case	830	Not all event models support a blocking wait - some die in that case
595	(programs might want to do that to stay interactive), so I<if you are	831	(programs might want to do that to stay interactive), so I<if you are
596	using this from a module, never require a blocking wait>, but let the	832	using this from a module, never require a blocking wait>. Instead, let the
597	caller decide whether the call will block or not (for example, by coupling	833	caller decide whether the call will block or not (for example, by coupling
598	condition variables with some kind of request results and supporting	834	condition variables with some kind of request results and supporting
599	callbacks so the caller knows that getting the result will not block,	835	callbacks so the caller knows that getting the result will not block,
600	while still supporting blocking waits if the caller so desires).	836	while still supporting blocking waits if the caller so desires).
601		837
602	Another reason I<never> to C<< ->recv >> in a module is that you cannot
603	sensibly have two C<< ->recv >>'s in parallel, as that would require
604	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
605	can supply.
606
607	The L<Coro> module, however, I<can> and I<does> supply coroutines and, in
608	fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe
609	versions and also integrates coroutines into AnyEvent, making blocking
610	C<< ->recv >> calls perfectly safe as long as they are done from another
611	coroutine (one that doesn't run the event loop).
612
613	You can ensure that C<< -recv >> never blocks by setting a callback and	838	You can ensure that C<< ->recv >> never blocks by setting a callback and
614	only calling C<< ->recv >> from within that callback (or at a later	839	only calling C<< ->recv >> from within that callback (or at a later
615	time). This will work even when the event loop does not support blocking	840	time). This will work even when the event loop does not support blocking
616	waits otherwise.	841	waits otherwise.
617		842
618	=item $bool = $cv->ready	843	=item $bool = $cv->ready
…		…
624		849
625	This is a mutator function that returns the callback set and optionally	850	This is a mutator function that returns the callback set and optionally
626	replaces it before doing so.	851	replaces it before doing so.
627		852
628	The callback will be called when the condition becomes "true", i.e. when	853	The callback will be called when the condition becomes "true", i.e. when
629	C<send> or C<croak> are called, with the only argument being the condition	854	C<send> or C<croak> are called, with the only argument being the
630	variable itself. Calling C<recv> inside the callback or at any later time	855	condition variable itself. If the condition is already true, the
631	is guaranteed not to block.	856	callback is called immediately when it is set. Calling C<recv> inside
		857	the callback or at any later time is guaranteed not to block.
632		858
633	=back	859	=back
634		860
		861	=head1 SUPPORTED EVENT LOOPS/BACKENDS
		862
		863	The available backend classes are (every class has its own manpage):
		864
		865	=over 4
		866
		867	=item Backends that are autoprobed when no other event loop can be found.
		868
		869	EV is the preferred backend when no other event loop seems to be in
		870	use. If EV is not installed, then AnyEvent will fall back to its own
		871	pure-perl implementation, which is available everywhere as it comes with
		872	AnyEvent itself.
		873
		874	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		875	AnyEvent::Impl::Perl pure-perl AnyEvent::Loop, fast and portable.
		876
		877	=item Backends that are transparently being picked up when they are used.
		878
		879	These will be used if they are already loaded when the first watcher
		880	is created, in which case it is assumed that the application is using
		881	them. This means that AnyEvent will automatically pick the right backend
		882	when the main program loads an event module before anything starts to
		883	create watchers. Nothing special needs to be done by the main program.
		884
		885	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		886	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		887	AnyEvent::Impl::Tk based on Tk, very broken.
		888	AnyEvent::Impl::UV based on UV, innovated square wheels.
		889	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		890	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		891	AnyEvent::Impl::Irssi used when running within irssi.
		892	AnyEvent::Impl::IOAsync based on IO::Async.
		893	AnyEvent::Impl::Cocoa based on Cocoa::EventLoop.
		894	AnyEvent::Impl::FLTK based on FLTK (fltk 2 binding).
		895
		896	=item Backends with special needs.
		897
		898	Qt requires the Qt::Application to be instantiated first, but will
		899	otherwise be picked up automatically. As long as the main program
		900	instantiates the application before any AnyEvent watchers are created,
		901	everything should just work.
		902
		903	AnyEvent::Impl::Qt based on Qt.
		904
		905	=item Event loops that are indirectly supported via other backends.
		906
		907	Some event loops can be supported via other modules:
		908
		909	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		910
		911	B<WxWidgets> has no support for watching file handles. However, you can
		912	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		913	polls 20 times per second, which was considered to be too horrible to even
		914	consider for AnyEvent.
		915
		916	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		917	backend, so it can be supported through POE.
		918
		919	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		920	load L<POE> when detecting them, in the hope that POE will pick them up,
		921	in which case everything will be automatic.
		922
		923	=back
		924
635	=head1 GLOBAL VARIABLES AND FUNCTIONS	925	=head1 GLOBAL VARIABLES AND FUNCTIONS
636		926
		927	These are not normally required to use AnyEvent, but can be useful to
		928	write AnyEvent extension modules.
		929
637	=over 4	930	=over 4
638		931
639	=item $AnyEvent::MODEL	932	=item $AnyEvent::MODEL
640		933
641	Contains C<undef> until the first watcher is being created. Then it	934	Contains C<undef> until the first watcher is being created, before the
		935	backend has been autodetected.
		936
642	contains the event model that is being used, which is the name of the	937	Afterwards it contains the event model that is being used, which is the
643	Perl class implementing the model. This class is usually one of the	938	name of the Perl class implementing the model. This class is usually one
644	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	939	of the C<AnyEvent::Impl::xxx> modules, but can be any other class in the
645	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	940	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
646		941	will be C<urxvt::anyevent>).
647	The known classes so far are:
648
649	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
650	AnyEvent::Impl::Event based on Event, second best choice.
651	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
652	AnyEvent::Impl::Glib based on Glib, third-best choice.
653	AnyEvent::Impl::Tk based on Tk, very bad choice.
654	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
655	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
656	AnyEvent::Impl::POE based on POE, not generic enough for full support.
657
658	There is no support for WxWidgets, as WxWidgets has no support for
659	watching file handles. However, you can use WxWidgets through the
660	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
661	second, which was considered to be too horrible to even consider for
662	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
663	it's adaptor.
664
665	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
666	autodetecting them.
667		942
668	=item AnyEvent::detect	943	=item AnyEvent::detect
669		944
670	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	945	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
671	if necessary. You should only call this function right before you would	946	if necessary. You should only call this function right before you would
672	have created an AnyEvent watcher anyway, that is, as late as possible at	947	have created an AnyEvent watcher anyway, that is, as late as possible at
673	runtime.	948	runtime, and not e.g. during initialisation of your module.
		949
		950	The effect of calling this function is as if a watcher had been created
		951	(specifically, actions that happen "when the first watcher is created"
		952	happen when calling detetc as well).
		953
		954	If you need to do some initialisation before AnyEvent watchers are
		955	created, use C<post_detect>.
674		956
675	=item $guard = AnyEvent::post_detect { BLOCK }	957	=item $guard = AnyEvent::post_detect { BLOCK }
676		958
677	Arranges for the code block to be executed as soon as the event model is	959	Arranges for the code block to be executed as soon as the event model is
678	autodetected (or immediately if this has already happened).	960	autodetected (or immediately if that has already happened).
		961
		962	The block will be executed I<after> the actual backend has been detected
		963	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		964	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		965	other initialisations - see the sources of L<AnyEvent::Strict> or
		966	L<AnyEvent::AIO> to see how this is used.
		967
		968	The most common usage is to create some global watchers, without forcing
		969	event module detection too early, for example, L<AnyEvent::AIO> creates
		970	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		971	avoid autodetecting the event module at load time.
679		972
680	If called in scalar or list context, then it creates and returns an object	973	If called in scalar or list context, then it creates and returns an object
681	that automatically removes the callback again when it is destroyed. See	974	that automatically removes the callback again when it is destroyed (or
		975	C<undef> when the hook was immediately executed). See L<AnyEvent::AIO> for
682	L<Coro::BDB> for a case where this is useful.	976	a case where this is useful.
		977
		978	Example: Create a watcher for the IO::AIO module and store it in
		979	C<$WATCHER>, but do so only do so after the event loop is initialised.
		980
		981	our WATCHER;
		982
		983	my $guard = AnyEvent::post_detect {
		984	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		985	};
		986
		987	# the ||= is important in case post_detect immediately runs the block,
		988	# as to not clobber the newly-created watcher. assigning both watcher and
		989	# post_detect guard to the same variable has the advantage of users being
		990	# able to just C<undef $WATCHER> if the watcher causes them grief.
		991
		992	$WATCHER ||= $guard;
683		993
684	=item @AnyEvent::post_detect	994	=item @AnyEvent::post_detect
685		995
686	If there are any code references in this array (you can C<push> to it	996	If there are any code references in this array (you can C<push> to it
687	before or after loading AnyEvent), then they will called directly after	997	before or after loading AnyEvent), then they will be called directly
688	the event loop has been chosen.	998	after the event loop has been chosen.
689		999
690	You should check C<$AnyEvent::MODEL> before adding to this array, though:	1000	You should check C<$AnyEvent::MODEL> before adding to this array, though:
691	if it contains a true value then the event loop has already been detected,	1001	if it is defined then the event loop has already been detected, and the
692	and the array will be ignored.	1002	array will be ignored.
693		1003
694	Best use C<AnyEvent::post_detect { BLOCK }> instead.	1004	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		1005	it, as it takes care of these details.
		1006
		1007	This variable is mainly useful for modules that can do something useful
		1008	when AnyEvent is used and thus want to know when it is initialised, but do
		1009	not need to even load it by default. This array provides the means to hook
		1010	into AnyEvent passively, without loading it.
		1011
		1012	Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used
		1013	together, you could put this into Coro (this is the actual code used by
		1014	Coro to accomplish this):
		1015
		1016	if (defined $AnyEvent::MODEL) {
		1017	# AnyEvent already initialised, so load Coro::AnyEvent
		1018	require Coro::AnyEvent;
		1019	} else {
		1020	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent
		1021	# as soon as it is
		1022	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };
		1023	}
		1024
		1025	=item AnyEvent::postpone { BLOCK }
		1026
		1027	Arranges for the block to be executed as soon as possible, but not before
		1028	the call itself returns. In practise, the block will be executed just
		1029	before the event loop polls for new events, or shortly afterwards.
		1030
		1031	This function never returns anything (to make the C<return postpone { ...
		1032	}> idiom more useful.
		1033
		1034	To understand the usefulness of this function, consider a function that
		1035	asynchronously does something for you and returns some transaction
		1036	object or guard to let you cancel the operation. For example,
		1037	C<AnyEvent::Socket::tcp_connect>:
		1038
		1039	# start a connection attempt unless one is active
		1040	$self->{connect_guard} ||= AnyEvent::Socket::tcp_connect "www.example.net", 80, sub {
		1041	delete $self->{connect_guard};
		1042	...
		1043	};
		1044
		1045	Imagine that this function could instantly call the callback, for
		1046	example, because it detects an obvious error such as a negative port
		1047	number. Invoking the callback before the function returns causes problems
		1048	however: the callback will be called and will try to delete the guard
		1049	object. But since the function hasn't returned yet, there is nothing to
		1050	delete. When the function eventually returns it will assign the guard
		1051	object to C<< $self->{connect_guard} >>, where it will likely never be
		1052	deleted, so the program thinks it is still trying to connect.
		1053
		1054	This is where C<AnyEvent::postpone> should be used. Instead of calling the
		1055	callback directly on error:
		1056
		1057	$cb->(undef), return # signal error to callback, BAD!
		1058	if $some_error_condition;
		1059
		1060	It should use C<postpone>:
		1061
		1062	AnyEvent::postpone { $cb->(undef) }, return # signal error to callback, later
		1063	if $some_error_condition;
		1064
		1065	=item AnyEvent::log $level, $msg[, @args]
		1066
		1067	Log the given C<$msg> at the given C<$level>.
		1068
		1069	If L<AnyEvent::Log> is not loaded then this function makes a simple test
		1070	to see whether the message will be logged. If the test succeeds it will
		1071	load AnyEvent::Log and call C<AnyEvent::Log::log> - consequently, look at
		1072	the L<AnyEvent::Log> documentation for details.
		1073
		1074	If the test fails it will simply return. Right now this happens when a
		1075	numerical loglevel is used and it is larger than the level specified via
		1076	C<$ENV{PERL_ANYEVENT_VERBOSE}>.
		1077
		1078	If you want to sprinkle loads of logging calls around your code, consider
		1079	creating a logger callback with the C<AnyEvent::Log::logger> function,
		1080	which can reduce typing, codesize and can reduce the logging overhead
		1081	enourmously.
695		1082
696	=back	1083	=back
697		1084
698	=head1 WHAT TO DO IN A MODULE	1085	=head1 WHAT TO DO IN A MODULE
699		1086
…		…
710	because it will stall the whole program, and the whole point of using	1097	because it will stall the whole program, and the whole point of using
711	events is to stay interactive.	1098	events is to stay interactive.
712		1099
713	It is fine, however, to call C<< ->recv >> when the user of your module	1100	It is fine, however, to call C<< ->recv >> when the user of your module
714	requests it (i.e. if you create a http request object ad have a method	1101	requests it (i.e. if you create a http request object ad have a method
715	called C<results> that returns the results, it should call C<< ->recv >>	1102	called C<results> that returns the results, it may call C<< ->recv >>
716	freely, as the user of your module knows what she is doing. always).	1103	freely, as the user of your module knows what she is doing. Always).
717		1104
718	=head1 WHAT TO DO IN THE MAIN PROGRAM	1105	=head1 WHAT TO DO IN THE MAIN PROGRAM
719		1106
720	There will always be a single main program - the only place that should	1107	There will always be a single main program - the only place that should
721	dictate which event model to use.	1108	dictate which event model to use.
722		1109
723	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	1110	If the program is not event-based, it need not do anything special, even
724	do anything special (it does not need to be event-based) and let AnyEvent	1111	when it depends on a module that uses an AnyEvent. If the program itself
725	decide which implementation to chose if some module relies on it.	1112	uses AnyEvent, but does not care which event loop is used, all it needs
		1113	to do is C<use AnyEvent>. In either case, AnyEvent will choose the best
		1114	available loop implementation.
726		1115
727	If the main program relies on a specific event model - for example, in	1116	If the main program relies on a specific event model - for example, in
728	Gtk2 programs you have to rely on the Glib module - you should load the	1117	Gtk2 programs you have to rely on the Glib module - you should load the
729	event module before loading AnyEvent or any module that uses it: generally	1118	event module before loading AnyEvent or any module that uses it: generally
730	speaking, you should load it as early as possible. The reason is that	1119	speaking, you should load it as early as possible. The reason is that
731	modules might create watchers when they are loaded, and AnyEvent will	1120	modules might create watchers when they are loaded, and AnyEvent will
732	decide on the event model to use as soon as it creates watchers, and it	1121	decide on the event model to use as soon as it creates watchers, and it
733	might chose the wrong one unless you load the correct one yourself.	1122	might choose the wrong one unless you load the correct one yourself.
734		1123
735	You can chose to use a pure-perl implementation by loading the	1124	You can chose to use a pure-perl implementation by loading the
736	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour	1125	C<AnyEvent::Loop> module, which gives you similar behaviour
737	everywhere, but letting AnyEvent chose the model is generally better.	1126	everywhere, but letting AnyEvent chose the model is generally better.
738		1127
739	=head2 MAINLOOP EMULATION	1128	=head2 MAINLOOP EMULATION
740		1129
741	Sometimes (often for short test scripts, or even standalone programs who	1130	Sometimes (often for short test scripts, or even standalone programs who
…		…
754		1143
755		1144
756	=head1 OTHER MODULES	1145	=head1 OTHER MODULES
757		1146
758	The following is a non-exhaustive list of additional modules that use	1147	The following is a non-exhaustive list of additional modules that use
759	AnyEvent and can therefore be mixed easily with other AnyEvent modules	1148	AnyEvent as a client and can therefore be mixed easily with other
760	in the same program. Some of the modules come with AnyEvent, some are	1149	AnyEvent modules and other event loops in the same program. Some of the
761	available via CPAN.	1150	modules come as part of AnyEvent, the others are available via CPAN (see
		1151	L<http://search.cpan.org/search?m=module&q=anyevent%3A%3A*> for
		1152	a longer non-exhaustive list), and the list is heavily biased towards
		1153	modules of the AnyEvent author himself :)
762		1154
763	=over 4	1155	=over 4
764		1156
765	=item L<AnyEvent::Util>	1157	=item L<AnyEvent::Util> (part of the AnyEvent distribution)
766		1158
767	Contains various utility functions that replace often-used but blocking	1159	Contains various utility functions that replace often-used blocking
768	functions such as C<inet_aton> by event-/callback-based versions.	1160	functions such as C<inet_aton> with event/callback-based versions.
769		1161
770	=item L<AnyEvent::Socket>	1162	=item L<AnyEvent::Socket> (part of the AnyEvent distribution)
771		1163
772	Provides various utility functions for (internet protocol) sockets,	1164	Provides various utility functions for (internet protocol) sockets,
773	addresses and name resolution. Also functions to create non-blocking tcp	1165	addresses and name resolution. Also functions to create non-blocking tcp
774	connections or tcp servers, with IPv6 and SRV record support and more.	1166	connections or tcp servers, with IPv6 and SRV record support and more.
775		1167
776	=item L<AnyEvent::Handle>	1168	=item L<AnyEvent::Handle> (part of the AnyEvent distribution)
777		1169
778	Provide read and write buffers, manages watchers for reads and writes,	1170	Provide read and write buffers, manages watchers for reads and writes,
779	supports raw and formatted I/O, I/O queued and fully transparent and	1171	supports raw and formatted I/O, I/O queued and fully transparent and
780	non-blocking SSL/TLS.	1172	non-blocking SSL/TLS (via L<AnyEvent::TLS>).
781		1173
782	=item L<AnyEvent::DNS>	1174	=item L<AnyEvent::DNS> (part of the AnyEvent distribution)
783		1175
784	Provides rich asynchronous DNS resolver capabilities.	1176	Provides rich asynchronous DNS resolver capabilities.
785		1177
786	=item L<AnyEvent::HTTP>	1178	=item L<AnyEvent::HTTP>, L<AnyEvent::IRC>, L<AnyEvent::XMPP>, L<AnyEvent::GPSD>, L<AnyEvent::IGS>, L<AnyEvent::FCP>
787		1179
788	A simple-to-use HTTP library that is capable of making a lot of concurrent	1180	Implement event-based interfaces to the protocols of the same name (for
789	HTTP requests.	1181	the curious, IGS is the International Go Server and FCP is the Freenet
		1182	Client Protocol).
790		1183
		1184	=item L<AnyEvent::AIO> (part of the AnyEvent distribution)
		1185
		1186	Truly asynchronous (as opposed to non-blocking) I/O, should be in the
		1187	toolbox of every event programmer. AnyEvent::AIO transparently fuses
		1188	L<IO::AIO> and AnyEvent together, giving AnyEvent access to event-based
		1189	file I/O, and much more.
		1190
		1191	=item L<AnyEvent::Fork>, L<AnyEvent::Fork::RPC>, L<AnyEvent::Fork::Pool>, L<AnyEvent::Fork::Remote>
		1192
		1193	These let you safely fork new subprocesses, either locally or
		1194	remotely (e.g.v ia ssh), using some RPC protocol or not, without
		1195	the limitations normally imposed by fork (AnyEvent works fine for
		1196	example). Dynamically-resized worker pools are obviously included as well.
		1197
		1198	And they are quite tiny and fast as well - "abusing" L<AnyEvent::Fork>
		1199	just to exec external programs can easily beat using C<fork> and C<exec>
		1200	(or even C<system>) in most programs.
		1201
		1202	=item L<AnyEvent::Filesys::Notify>
		1203
		1204	AnyEvent is good for non-blocking stuff, but it can't detect file or
		1205	path changes (e.g. "watch this directory for new files", "watch this
		1206	file for changes"). The L<AnyEvent::Filesys::Notify> module promises to
		1207	do just that in a portbale fashion, supporting inotify on GNU/Linux and
		1208	some weird, without doubt broken, stuff on OS X to monitor files. It can
		1209	fall back to blocking scans at regular intervals transparently on other
		1210	platforms, so it's about as portable as it gets.
		1211
		1212	(I haven't used it myself, but it seems the biggest problem with it is
		1213	it quite bad performance).
		1214
791	=item L<AnyEvent::HTTPD>	1215	=item L<AnyEvent::DBI>
792		1216
793	Provides a simple web application server framework.	1217	Executes L<DBI> requests asynchronously in a proxy process for you,
		1218	notifying you in an event-based way when the operation is finished.
794		1219
795	=item L<AnyEvent::FastPing>	1220	=item L<AnyEvent::FastPing>
796		1221
797	The fastest ping in the west.	1222	The fastest ping in the west.
798		1223
799	=item L<AnyEvent::DBI>
800
801	Executes L<DBI> requests asynchronously in a proxy process.
802
803	=item L<AnyEvent::AIO>
804
805	Truly asynchronous I/O, should be in the toolbox of every event
806	programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
807	together.
808
809	=item L<AnyEvent::BDB>
810
811	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
812	L<BDB> and AnyEvent together.
813
814	=item L<AnyEvent::GPSD>
815
816	A non-blocking interface to gpsd, a daemon delivering GPS information.
817
818	=item L<AnyEvent::IGS>
819
820	A non-blocking interface to the Internet Go Server protocol (used by
821	L<App::IGS>).
822
823	=item L<Net::IRC3>
824
825	AnyEvent based IRC client module family.
826
827	=item L<Net::XMPP2>
828
829	AnyEvent based XMPP (Jabber protocol) module family.
830
831	=item L<Net::FCP>
832
833	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
834	of AnyEvent.
835
836	=item L<Event::ExecFlow>
837
838	High level API for event-based execution flow control.
839
840	=item L<Coro>	1224	=item L<Coro>
841		1225
842	Has special support for AnyEvent via L<Coro::AnyEvent>.	1226	Has special support for AnyEvent via L<Coro::AnyEvent>, which allows you
		1227	to simply invert the flow control - don't call us, we will call you:
843		1228
844	=item L<IO::Lambda>	1229	async {
		1230	Coro::AnyEvent::sleep 5; # creates a 5s timer and waits for it
		1231	print "5 seconds later!\n";
845		1232
846	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.	1233	Coro::AnyEvent::readable *STDIN; # uses an I/O watcher
		1234	my $line = <STDIN>; # works for ttys
		1235
		1236	AnyEvent::HTTP::http_get "url", Coro::rouse_cb;
		1237	my ($body, $hdr) = Coro::rouse_wait;
		1238	};
847		1239
848	=back	1240	=back
849		1241
850	=cut	1242	=cut
851		1243
852	package AnyEvent;	1244	package AnyEvent;
853		1245
854	no warnings;	1246	BEGIN {
855	use strict qw(vars subs);	1247	require "AnyEvent/constants.pl";
		1248	&AnyEvent::common_sense;
		1249	}
856		1250
857	use Carp;	1251	use Carp ();
858		1252
859	our $VERSION = 4.233;	1253	our $VERSION = '7.07';
860	our $MODEL;	1254	our $MODEL;
861
862	our $AUTOLOAD;
863	our @ISA;	1255	our @ISA;
864
865	our @REGISTRY;	1256	our @REGISTRY;
866		1257	our $VERBOSE;
867	our $WIN32;	1258	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		1259	our $MAX_SIGNAL_LATENCY = $ENV{PERL_ANYEVENT_MAX_SIGNAL_LATENCY} || 10; # executes after the BEGIN block below (tainting!)
868		1260
869	BEGIN {	1261	BEGIN {
870	my $win32 = ! ! ($^O =~ /mswin32/i);	1262	eval "sub TAINT (){" . (${^TAINT}*1) . "}";
871	eval "sub WIN32(){ $win32 }";
872	}
873		1263
874	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;	1264	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1265	if ${^TAINT};
875		1266
876	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred	1267	$ENV{"PERL_ANYEVENT_$_"} = $ENV{"AE_$_"}
		1268	for grep s/^AE_// && !exists $ENV{"PERL_ANYEVENT_$_"}, keys %ENV;
877		1269
878	{	1270	@ENV{grep /^PERL_ANYEVENT_/, keys %ENV} = ()
		1271	if ${^TAINT};
		1272
		1273	# $ENV{PERL_ANYEVENT_xxx} now valid
		1274
		1275	$VERBOSE = length $ENV{PERL_ANYEVENT_VERBOSE} ? $ENV{PERL_ANYEVENT_VERBOSE}*1 : 4;
		1276
879	my $idx;	1277	my $idx;
880	$PROTOCOL{$_} = ++$idx	1278	$PROTOCOL{$_} = ++$idx
881	for reverse split /\s*,\s*/,	1279	for reverse split /\s*,\s*/,
882	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";	1280	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
883	}	1281	}
884		1282
		1283	our @post_detect;
		1284
		1285	sub post_detect(&) {
		1286	my ($cb) = @_;
		1287
		1288	push @post_detect, $cb;
		1289
		1290	defined wantarray
		1291	? bless \$cb, "AnyEvent::Util::postdetect"
		1292	: ()
		1293	}
		1294
		1295	sub AnyEvent::Util::postdetect::DESTROY {
		1296	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		1297	}
		1298
		1299	our $POSTPONE_W;
		1300	our @POSTPONE;
		1301
		1302	sub _postpone_exec {
		1303	undef $POSTPONE_W;
		1304
		1305	&{ shift @POSTPONE }
		1306	while @POSTPONE;
		1307	}
		1308
		1309	sub postpone(&) {
		1310	push @POSTPONE, shift;
		1311
		1312	$POSTPONE_W ||= AE::timer (0, 0, \&_postpone_exec);
		1313
		1314	()
		1315	}
		1316
		1317	sub log($$;@) {
		1318	# only load the big bloated module when we actually are about to log something
		1319	if ($_[0] <= ($VERBOSE || 1)) { # also catches non-numeric levels(!) and fatal
		1320	local ($!, $@);
		1321	require AnyEvent::Log; # among other things, sets $VERBOSE to 9
		1322	# AnyEvent::Log overwrites this function
		1323	goto &log;
		1324	}
		1325
		1326	0 # not logged
		1327	}
		1328
		1329	sub _logger($;$) {
		1330	my ($level, $renabled) = @_;
		1331
		1332	$$renabled = $level <= $VERBOSE;
		1333
		1334	my $logger = [(caller)[0], $level, $renabled];
		1335
		1336	$AnyEvent::Log::LOGGER{$logger+0} = $logger;
		1337
		1338	# return unless defined wantarray;
		1339	#
		1340	# require AnyEvent::Util;
		1341	# my $guard = AnyEvent::Util::guard (sub {
		1342	# # "clean up"
		1343	# delete $LOGGER{$logger+0};
		1344	# });
		1345	#
		1346	# sub {
		1347	# return 0 unless $$renabled;
		1348	#
		1349	# $guard if 0; # keep guard alive, but don't cause runtime overhead
		1350	# require AnyEvent::Log unless $AnyEvent::Log::VERSION;
		1351	# package AnyEvent::Log;
		1352	# _log ($logger->[0], $level, @_) # logger->[0] has been converted at load time
		1353	# }
		1354	}
		1355
		1356	if (length $ENV{PERL_ANYEVENT_LOG}) {
		1357	require AnyEvent::Log; # AnyEvent::Log does the thing for us
		1358	}
		1359
885	my @models = (	1360	our @models = (
886	[EV:: => AnyEvent::Impl::EV::],	1361	[EV:: => AnyEvent::Impl::EV::],
887	[Event:: => AnyEvent::Impl::Event::],
888	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1362	[AnyEvent::Loop:: => AnyEvent::Impl::Perl::],
889	# everything below here will not be autoprobed	1363	# everything below here will not (normally) be autoprobed
890	# as the pureperl backend should work everywhere	1364	# as the pure perl backend should work everywhere
891	# and is usually faster	1365	# and is usually faster
		1366	[Irssi:: => AnyEvent::Impl::Irssi::], # Irssi has a bogus "Event" package, so msut be near the top
		1367	[Event:: => AnyEvent::Impl::Event::], # slow, stable
		1368	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers
		1369	# everything below here should not be autoloaded
		1370	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
892	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles	1371	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
893	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers	1372	[UV:: => AnyEvent::Impl::UV::], # switched from libev, added back all bugs imaginable
894	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
895	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program	1373	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
896	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza	1374	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
897	[Wx:: => AnyEvent::Impl::POE::],	1375	[Wx:: => AnyEvent::Impl::POE::],
898	[Prima:: => AnyEvent::Impl::POE::],	1376	[Prima:: => AnyEvent::Impl::POE::],
		1377	[IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # a bitch to autodetect
		1378	[Cocoa::EventLoop:: => AnyEvent::Impl::Cocoa::],
		1379	[FLTK:: => AnyEvent::Impl::FLTK::],
899	);	1380	);
900		1381
901	our %method = map +($_ => 1), qw(io timer time now signal child condvar one_event DESTROY);	1382	our @isa_hook;
902		1383
903	our @post_detect;	1384	sub _isa_set {
		1385	my @pkg = ("AnyEvent", (map $_->[0], grep defined, @isa_hook), $MODEL);
904		1386
		1387	@{"$pkg[$_-1]::ISA"} = $pkg[$_]
		1388	for 1 .. $#pkg;
		1389
		1390	grep $_ && $_->[1], @isa_hook
		1391	and AE::_reset ();
		1392	}
		1393
		1394	# used for hooking AnyEvent::Strict and AnyEvent::Debug::Wrap into the class hierarchy
		1395	sub _isa_hook($$;$) {
		1396	my ($i, $pkg, $reset_ae) = @_;
		1397
		1398	$isa_hook[$i] = $pkg ? [$pkg, $reset_ae] : undef;
		1399
		1400	_isa_set;
		1401	}
		1402
		1403	# all autoloaded methods reserve the complete glob, not just the method slot.
		1404	# due to bugs in perls method cache implementation.
		1405	our @methods = qw(io timer time now now_update signal child idle condvar);
		1406
905	sub post_detect(&) {	1407	sub detect() {
906	my ($cb) = @_;	1408	return $MODEL if $MODEL; # some programs keep references to detect
907		1409
908	if ($MODEL) {	1410	# IO::Async::Loop::AnyEvent is extremely evil, refuse to work with it
909	$cb->();	1411	# the author knows about the problems and what it does to AnyEvent as a whole
		1412	# (and the ability of others to use AnyEvent), but simply wants to abuse AnyEvent
		1413	# anyway.
		1414	AnyEvent::log fatal => "IO::Async::Loop::AnyEvent detected - that module is broken by\n"
		1415	. "design, abuses internals and breaks AnyEvent - will not continue."
		1416	if exists $INC{"IO/Async/Loop/AnyEvent.pm"};
910		1417
911	1	1418	local $!; # for good measure
		1419	local $SIG{__DIE__}; # we use eval
		1420
		1421	# free some memory
		1422	*detect = sub () { $MODEL };
		1423	# undef &func doesn't correctly update the method cache. grmbl.
		1424	# so we delete the whole glob. grmbl.
		1425	# otoh, perl doesn't let me undef an active usb, but it lets me free
		1426	# a glob with an active sub. hrm. i hope it works, but perl is
		1427	# usually buggy in this department. sigh.
		1428	delete @{"AnyEvent::"}{@methods};
		1429	undef @methods;
		1430
		1431	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z0-9:]+)$/) {
		1432	my $model = $1;
		1433	$model = "AnyEvent::Impl::$model" unless $model =~ s/::$//;
		1434	if (eval "require $model") {
		1435	AnyEvent::log 7 => "Loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.";
		1436	$MODEL = $model;
912	} else {	1437	} else {
913	push @post_detect, $cb;	1438	AnyEvent::log 4 => "Unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@";
914		1439	}
915	defined wantarray
916	? bless \$cb, "AnyEvent::Util::PostDetect"
917	: ()
918	}	1440	}
919	}
920		1441
921	sub AnyEvent::Util::PostDetect::DESTROY {	1442	# check for already loaded models
922	@post_detect = grep $_ != ${$_[0]}, @post_detect;
923	}
924
925	sub detect() {
926	unless ($MODEL) {	1443	unless ($MODEL) {
927	no strict 'refs';	1444	for (@REGISTRY, @models) {
928	local $SIG{__DIE__};	1445	my ($package, $model) = @$_;
929		1446	if (${"$package\::VERSION"} > 0) {
930	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
931	my $model = "AnyEvent::Impl::$1";
932	if (eval "require $model") {	1447	if (eval "require $model") {
		1448	AnyEvent::log 7 => "Autodetected model '$model', using it.";
933	$MODEL = $model;	1449	$MODEL = $model;
934	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	1450	last;
935	} else {	1451	} else {
936	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;	1452	AnyEvent::log 8 => "Detected event loop $package, but cannot load '$model', skipping: $@";
		1453	}
937	}	1454	}
938	}	1455	}
939		1456
940	# check for already loaded models
941	unless ($MODEL) {	1457	unless ($MODEL) {
		1458	# try to autoload a model
942	for (@REGISTRY, @models) {	1459	for (@REGISTRY, @models) {
943	my ($package, $model) = @$_;	1460	my ($package, $model) = @$_;
		1461	if (
		1462	eval "require $package"
944	if (${"$package\::VERSION"} > 0) {	1463	and ${"$package\::VERSION"} > 0
945	if (eval "require $model") {	1464	and eval "require $model"
		1465	) {
		1466	AnyEvent::log 7 => "Autoloaded model '$model', using it.";
946	$MODEL = $model;	1467	$MODEL = $model;
947	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;
948	last;	1468	last;
949	}
950	}	1469	}
951	}	1470	}
952		1471
953	unless ($MODEL) {
954	# try to load a model
955
956	for (@REGISTRY, @models) {
957	my ($package, $model) = @$_;
958	if (eval "require $package"
959	and ${"$package\::VERSION"} > 0
960	and eval "require $model") {
961	$MODEL = $model;
962	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;
963	last;
964	}
965	}
966
967	$MODEL	1472	$MODEL
968	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.";	1473	or AnyEvent::log fatal => "Backend autodetection failed - did you properly install AnyEvent?";
969	}
970	}	1474	}
971
972	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
973
974	unshift @ISA, $MODEL;
975
976	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
977
978	(shift @post_detect)->() while @post_detect;
979	}	1475	}
980		1476
		1477	# free memory only needed for probing
		1478	undef @models;
		1479	undef @REGISTRY;
		1480
		1481	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		1482
		1483	# now nuke some methods that are overridden by the backend.
		1484	# SUPER usage is not allowed in these.
		1485	for (qw(time signal child idle)) {
		1486	undef &{"AnyEvent::Base::$_"}
		1487	if defined &{"$MODEL\::$_"};
		1488	}
		1489
		1490	_isa_set;
		1491
		1492	# we're officially open!
		1493
		1494	if ($ENV{PERL_ANYEVENT_STRICT}) {
		1495	require AnyEvent::Strict;
		1496	}
		1497
		1498	if ($ENV{PERL_ANYEVENT_DEBUG_WRAP}) {
		1499	require AnyEvent::Debug;
		1500	AnyEvent::Debug::wrap ($ENV{PERL_ANYEVENT_DEBUG_WRAP});
		1501	}
		1502
		1503	if (length $ENV{PERL_ANYEVENT_DEBUG_SHELL}) {
		1504	require AnyEvent::Socket;
		1505	require AnyEvent::Debug;
		1506
		1507	my $shell = $ENV{PERL_ANYEVENT_DEBUG_SHELL};
		1508	$shell =~ s/\$\$/$$/g;
		1509
		1510	my ($host, $service) = AnyEvent::Socket::parse_hostport ($shell);
		1511	$AnyEvent::Debug::SHELL = AnyEvent::Debug::shell ($host, $service);
		1512	}
		1513
		1514	# now the anyevent environment is set up as the user told us to, so
		1515	# call the actual user code - post detects
		1516
		1517	(shift @post_detect)->() while @post_detect;
		1518	undef @post_detect;
		1519
		1520	*post_detect = sub(&) {
		1521	shift->();
		1522
		1523	undef
		1524	};
		1525
981	$MODEL	1526	$MODEL
982	}	1527	}
983		1528
984	sub AUTOLOAD {	1529	for my $name (@methods) {
985	(my $func = $AUTOLOAD) =~ s/.*://;	1530	*$name = sub {
986		1531	detect;
987	$method{$func}	1532	# we use goto because
988	or croak "$func: not a valid method for AnyEvent objects";	1533	# a) it makes the thunk more transparent
989		1534	# b) it allows us to delete the thunk later
990	detect unless $MODEL;	1535	goto &{ UNIVERSAL::can AnyEvent => "SUPER::$name" }
991		1536	};
992	my $class = shift;
993	$class->$func (@_);
994	}	1537	}
995		1538
996	# utility function to dup a filehandle. this is used by many backends	1539	# utility function to dup a filehandle. this is used by many backends
997	# to support binding more than one watcher per filehandle (they usually	1540	# to support binding more than one watcher per filehandle (they usually
998	# allow only one watcher per fd, so we dup it to get a different one).	1541	# allow only one watcher per fd, so we dup it to get a different one).
999	sub _dupfh($$$$) {	1542	sub _dupfh($$;$$) {
1000	my ($poll, $fh, $r, $w) = @_;	1543	my ($poll, $fh, $r, $w) = @_;
1001		1544
1002	require Fcntl;
1003
1004	# cygwin requires the fh mode to be matching, unix doesn't	1545	# cygwin requires the fh mode to be matching, unix doesn't
1005	my ($rw, $mode) = $poll eq "r" ? ($r, "<")	1546	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
1006	: $poll eq "w" ? ($w, ">")
1007	: Carp::croak "AnyEvent->io requires poll set to either 'r' or 'w'";
1008		1547
1009	open my $fh2, "$mode&" . fileno $fh	1548	open my $fh2, $mode, $fh
1010	or die "cannot dup() filehandle: $!";	1549	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
1011		1550
1012	# we assume CLOEXEC is already set by perl in all important cases	1551	# we assume CLOEXEC is already set by perl in all important cases
1013		1552
1014	($fh2, $rw)	1553	($fh2, $rw)
1015	}	1554	}
1016		1555
		1556	=head1 SIMPLIFIED AE API
		1557
		1558	Starting with version 5.0, AnyEvent officially supports a second, much
		1559	simpler, API that is designed to reduce the calling, typing and memory
		1560	overhead by using function call syntax and a fixed number of parameters.
		1561
		1562	See the L<AE> manpage for details.
		1563
		1564	=cut
		1565
		1566	package AE;
		1567
		1568	our $VERSION = $AnyEvent::VERSION;
		1569
		1570	sub _reset() {
		1571	eval q{
		1572	# fall back to the main API by default - backends and AnyEvent::Base
		1573	# implementations can overwrite these.
		1574
		1575	sub io($$$) {
		1576	AnyEvent->io (fh => $_[0], poll => $_[1] ? "w" : "r", cb => $_[2])
		1577	}
		1578
		1579	sub timer($$$) {
		1580	AnyEvent->timer (after => $_[0], interval => $_[1], cb => $_[2])
		1581	}
		1582
		1583	sub signal($$) {
		1584	AnyEvent->signal (signal => $_[0], cb => $_[1])
		1585	}
		1586
		1587	sub child($$) {
		1588	AnyEvent->child (pid => $_[0], cb => $_[1])
		1589	}
		1590
		1591	sub idle($) {
		1592	AnyEvent->idle (cb => $_[0]);
		1593	}
		1594
		1595	sub cv(;&) {
		1596	AnyEvent->condvar (@_ ? (cb => $_[0]) : ())
		1597	}
		1598
		1599	sub now() {
		1600	AnyEvent->now
		1601	}
		1602
		1603	sub now_update() {
		1604	AnyEvent->now_update
		1605	}
		1606
		1607	sub time() {
		1608	AnyEvent->time
		1609	}
		1610
		1611	*postpone = \&AnyEvent::postpone;
		1612	*log = \&AnyEvent::log;
		1613	};
		1614	die if $@;
		1615	}
		1616
		1617	BEGIN { _reset }
		1618
1017	package AnyEvent::Base;	1619	package AnyEvent::Base;
1018		1620
1019	# default implementation for now and time	1621	# default implementations for many methods
1020		1622
1021	BEGIN {	1623	sub time {
		1624	eval q{ # poor man's autoloading {}
		1625	# probe for availability of Time::HiRes
1022	if (eval "use Time::HiRes (); time (); 1") {	1626	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1627	*time = sub { Time::HiRes::time () };
1023	*_time = \&Time::HiRes::time;	1628	*AE::time = \& Time::HiRes::time ;
		1629	*now = \&time;
		1630	AnyEvent::log 8 => "using Time::HiRes for sub-second timing accuracy.";
1024	# if (eval "use POSIX (); (POSIX::times())...	1631	# if (eval "use POSIX (); (POSIX::times())...
1025	} else {	1632	} else {
1026	*_time = \&CORE::time; # epic fail	1633	*time = sub { CORE::time };
		1634	*AE::time = sub (){ CORE::time };
		1635	*now = \&time;
		1636	AnyEvent::log 3 => "Using built-in time(), no sub-second resolution!";
		1637	}
		1638	};
		1639	die if $@;
		1640
		1641	&time
		1642	}
		1643
		1644	*now = \&time;
		1645	sub now_update { }
		1646
		1647	sub _poll {
		1648	Carp::croak "$AnyEvent::MODEL does not support blocking waits. Caught";
		1649	}
		1650
		1651	# default implementation for ->condvar
		1652	# in fact, the default should not be overwritten
		1653
		1654	sub condvar {
		1655	eval q{ # poor man's autoloading {}
		1656	*condvar = sub {
		1657	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
		1658	};
		1659
		1660	*AE::cv = sub (;&) {
		1661	bless { @_ ? (_ae_cb => shift) : () }, "AnyEvent::CondVar"
		1662	};
		1663	};
		1664	die if $@;
		1665
		1666	&condvar
		1667	}
		1668
		1669	# default implementation for ->signal
		1670
		1671	our $HAVE_ASYNC_INTERRUPT;
		1672
		1673	sub _have_async_interrupt() {
		1674	$HAVE_ASYNC_INTERRUPT = 1*(!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT}
		1675	&& eval "use Async::Interrupt 1.02 (); 1")
		1676	unless defined $HAVE_ASYNC_INTERRUPT;
		1677
		1678	$HAVE_ASYNC_INTERRUPT
		1679	}
		1680
		1681	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1682	our (%SIG_ASY, %SIG_ASY_W);
		1683	our ($SIG_COUNT, $SIG_TW);
		1684
		1685	# install a dummy wakeup watcher to reduce signal catching latency
		1686	# used by Impls
		1687	sub _sig_add() {
		1688	unless ($SIG_COUNT++) {
		1689	# try to align timer on a full-second boundary, if possible
		1690	my $NOW = AE::now;
		1691
		1692	$SIG_TW = AE::timer
		1693	$MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1694	$MAX_SIGNAL_LATENCY,
		1695	sub { } # just for the PERL_ASYNC_CHECK
		1696	;
1027	}	1697	}
1028	}	1698	}
1029		1699
1030	sub time { _time }	1700	sub _sig_del {
1031	sub now { _time }	1701	undef $SIG_TW
1032		1702	unless --$SIG_COUNT;
1033	# default implementation for ->condvar
1034
1035	sub condvar {
1036	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, AnyEvent::CondVar::
1037	}	1703	}
1038		1704
1039	# default implementation for ->signal	1705	our $_sig_name_init; $_sig_name_init = sub {
		1706	eval q{ # poor man's autoloading {}
		1707	undef $_sig_name_init;
1040		1708
1041	our %SIG_CB;	1709	if (_have_async_interrupt) {
		1710	*sig2num = \&Async::Interrupt::sig2num;
		1711	*sig2name = \&Async::Interrupt::sig2name;
		1712	} else {
		1713	require Config;
		1714
		1715	my %signame2num;
		1716	@signame2num{ split ' ', $Config::Config{sig_name} }
		1717	= split ' ', $Config::Config{sig_num};
		1718
		1719	my @signum2name;
		1720	@signum2name[values %signame2num] = keys %signame2num;
		1721
		1722	*sig2num = sub($) {
		1723	$_[0] > 0 ? shift : $signame2num{+shift}
		1724	};
		1725	*sig2name = sub ($) {
		1726	$_[0] > 0 ? $signum2name[+shift] : shift
		1727	};
		1728	}
		1729	};
		1730	die if $@;
		1731	};
		1732
		1733	sub sig2num ($) { &$_sig_name_init; &sig2num }
		1734	sub sig2name($) { &$_sig_name_init; &sig2name }
1042		1735
1043	sub signal {	1736	sub signal {
		1737	eval q{ # poor man's autoloading {}
		1738	# probe for availability of Async::Interrupt
		1739	if (_have_async_interrupt) {
		1740	AnyEvent::log 8 => "Using Async::Interrupt for race-free signal handling.";
		1741
		1742	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1743	$SIG_IO = AE::io $SIGPIPE_R->fileno, 0, \&_signal_exec;
		1744
		1745	} else {
		1746	AnyEvent::log 8 => "Using emulated perl signal handling with latency timer.";
		1747
		1748	if (AnyEvent::WIN32) {
		1749	require AnyEvent::Util;
		1750
		1751	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1752	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R, 1) if $SIGPIPE_R;
		1753	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W, 1) if $SIGPIPE_W; # just in case
		1754	} else {
		1755	pipe $SIGPIPE_R, $SIGPIPE_W;
		1756	fcntl $SIGPIPE_R, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_R;
		1757	fcntl $SIGPIPE_W, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_W; # just in case
		1758
		1759	# not strictly required, as $^F is normally 2, but let's make sure...
		1760	fcntl $SIGPIPE_R, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1761	fcntl $SIGPIPE_W, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1762	}
		1763
		1764	$SIGPIPE_R
		1765	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1766
		1767	$SIG_IO = AE::io $SIGPIPE_R, 0, \&_signal_exec;
		1768	}
		1769
		1770	*signal = $HAVE_ASYNC_INTERRUPT
		1771	? sub {
1044	my (undef, %arg) = @_;	1772	my (undef, %arg) = @_;
1045		1773
		1774	# async::interrupt
1046	my $signal = uc $arg{signal}	1775	my $signal = sig2num $arg{signal};
1047	or Carp::croak "required option 'signal' is missing";
1048
1049	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1776	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1777
		1778	$SIG_ASY{$signal} ||= new Async::Interrupt
		1779	cb => sub { undef $SIG_EV{$signal} },
		1780	signal => $signal,
		1781	pipe => [$SIGPIPE_R->filenos],
		1782	pipe_autodrain => 0,
		1783	;
		1784
		1785	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1786	}
		1787	: sub {
		1788	my (undef, %arg) = @_;
		1789
		1790	# pure perl
		1791	my $signal = sig2name $arg{signal};
		1792	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1793
1050	$SIG{$signal} ||= sub {	1794	$SIG{$signal} ||= sub {
		1795	local $!;
		1796	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1797	undef $SIG_EV{$signal};
		1798	};
		1799
		1800	# can't do signal processing without introducing races in pure perl,
		1801	# so limit the signal latency.
		1802	_sig_add;
		1803
		1804	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1805	}
		1806	;
		1807
		1808	*AnyEvent::Base::signal::DESTROY = sub {
		1809	my ($signal, $cb) = @{$_[0]};
		1810
		1811	_sig_del;
		1812
		1813	delete $SIG_CB{$signal}{$cb};
		1814
		1815	$HAVE_ASYNC_INTERRUPT
		1816	? delete $SIG_ASY{$signal}
		1817	: # delete doesn't work with older perls - they then
		1818	# print weird messages, or just unconditionally exit
		1819	# instead of getting the default action.
		1820	undef $SIG{$signal}
		1821	unless keys %{ $SIG_CB{$signal} };
		1822	};
		1823
		1824	*_signal_exec = sub {
		1825	$HAVE_ASYNC_INTERRUPT
		1826	? $SIGPIPE_R->drain
		1827	: sysread $SIGPIPE_R, (my $dummy), 9;
		1828
		1829	while (%SIG_EV) {
		1830	for (keys %SIG_EV) {
		1831	delete $SIG_EV{$_};
1051	$_->() for values %{ $SIG_CB{$signal} || {} };	1832	&$_ for values %{ $SIG_CB{$_} || {} };
		1833	}
		1834	}
		1835	};
1052	};	1836	};
		1837	die if $@;
1053		1838
1054	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1839	&signal
1055	}
1056
1057	sub AnyEvent::Base::Signal::DESTROY {
1058	my ($signal, $cb) = @{$_[0]};
1059
1060	delete $SIG_CB{$signal}{$cb};
1061
1062	delete $SIG{$signal} unless keys %{ $SIG_CB{$signal} };
1063	}	1840	}
1064		1841
1065	# default implementation for ->child	1842	# default implementation for ->child
1066		1843
1067	our %PID_CB;	1844	our %PID_CB;
1068	our $CHLD_W;	1845	our $CHLD_W;
1069	our $CHLD_DELAY_W;	1846	our $CHLD_DELAY_W;
1070	our $PID_IDLE;
1071	our $WNOHANG;
1072		1847
1073	sub _child_wait {	1848	# used by many Impl's
1074	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1849	sub _emit_childstatus($$) {
		1850	my (undef, $rpid, $rstatus) = @_;
		1851
		1852	$_->($rpid, $rstatus)
1075	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1853	for values %{ $PID_CB{$rpid} || {} },
1076	(values %{ $PID_CB{0} || {} });	1854	values %{ $PID_CB{0} || {} };
1077	}
1078
1079	undef $PID_IDLE;
1080	}
1081
1082	sub _sigchld {
1083	# make sure we deliver these changes "synchronous" with the event loop.
1084	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {
1085	undef $CHLD_DELAY_W;
1086	&_child_wait;
1087	});
1088	}	1855	}
1089		1856
1090	sub child {	1857	sub child {
		1858	eval q{ # poor man's autoloading {}
		1859	*_sigchld = sub {
		1860	my $pid;
		1861
		1862	AnyEvent->_emit_childstatus ($pid, $?)
		1863	while ($pid = waitpid -1, WNOHANG) > 0;
		1864	};
		1865
		1866	*child = sub {
1091	my (undef, %arg) = @_;	1867	my (undef, %arg) = @_;
1092		1868
1093	defined (my $pid = $arg{pid} + 0)	1869	my $pid = $arg{pid};
1094	or Carp::croak "required option 'pid' is missing";	1870	my $cb = $arg{cb};
1095		1871
1096	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1872	$PID_CB{$pid}{$cb+0} = $cb;
1097		1873
1098	unless ($WNOHANG) {
1099	$WNOHANG = eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
1100	}
1101
1102	unless ($CHLD_W) {	1874	unless ($CHLD_W) {
1103	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1875	$CHLD_W = AE::signal CHLD => \&_sigchld;
1104	# child could be a zombie already, so make at least one round	1876	# child could be a zombie already, so make at least one round
1105	&_sigchld;	1877	&_sigchld;
1106	}	1878	}
1107		1879
1108	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	1880	bless [$pid, $cb+0], "AnyEvent::Base::child"
1109	}	1881	};
1110		1882
1111	sub AnyEvent::Base::Child::DESTROY {	1883	*AnyEvent::Base::child::DESTROY = sub {
1112	my ($pid, $cb) = @{$_[0]};	1884	my ($pid, $icb) = @{$_[0]};
1113		1885
1114	delete $PID_CB{$pid}{$cb};	1886	delete $PID_CB{$pid}{$icb};
1115	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1887	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
1116		1888
1117	undef $CHLD_W unless keys %PID_CB;	1889	undef $CHLD_W unless keys %PID_CB;
		1890	};
		1891	};
		1892	die if $@;
		1893
		1894	&child
		1895	}
		1896
		1897	# idle emulation is done by simply using a timer, regardless
		1898	# of whether the process is idle or not, and not letting
		1899	# the callback use more than 50% of the time.
		1900	sub idle {
		1901	eval q{ # poor man's autoloading {}
		1902	*idle = sub {
		1903	my (undef, %arg) = @_;
		1904
		1905	my ($cb, $w, $rcb) = $arg{cb};
		1906
		1907	$rcb = sub {
		1908	if ($cb) {
		1909	$w = AE::time;
		1910	&$cb;
		1911	$w = AE::time - $w;
		1912
		1913	# never use more then 50% of the time for the idle watcher,
		1914	# within some limits
		1915	$w = 0.0001 if $w < 0.0001;
		1916	$w = 5 if $w > 5;
		1917
		1918	$w = AE::timer $w, 0, $rcb;
		1919	} else {
		1920	# clean up...
		1921	undef $w;
		1922	undef $rcb;
		1923	}
		1924	};
		1925
		1926	$w = AE::timer 0.05, 0, $rcb;
		1927
		1928	bless \\$cb, "AnyEvent::Base::idle"
		1929	};
		1930
		1931	*AnyEvent::Base::idle::DESTROY = sub {
		1932	undef $${$_[0]};
		1933	};
		1934	};
		1935	die if $@;
		1936
		1937	&idle
1118	}	1938	}
1119		1939
1120	package AnyEvent::CondVar;	1940	package AnyEvent::CondVar;
1121		1941
1122	our @ISA = AnyEvent::CondVar::Base::;	1942	our @ISA = AnyEvent::CondVar::Base::;
1123		1943
		1944	# only to be used for subclassing
		1945	sub new {
		1946	my $class = shift;
		1947	bless AnyEvent->condvar (@_), $class
		1948	}
		1949
1124	package AnyEvent::CondVar::Base;	1950	package AnyEvent::CondVar::Base;
1125		1951
1126	use overload	1952	#use overload
1127	'&{}' => sub { my $self = shift; sub { $self->send (@_) } },	1953	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
1128	fallback => 1;	1954	# fallback => 1;
		1955
		1956	# save 300+ kilobytes by dirtily hardcoding overloading
		1957	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1958	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1959	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1960	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1961
		1962	our $WAITING;
1129		1963
1130	sub _send {	1964	sub _send {
1131	# nop	1965	# nop
		1966	}
		1967
		1968	sub _wait {
		1969	AnyEvent->_poll until $_[0]{_ae_sent};
1132	}	1970	}
1133		1971
1134	sub send {	1972	sub send {
1135	my $cv = shift;	1973	my $cv = shift;
1136	$cv->{_ae_sent} = [@_];	1974	$cv->{_ae_sent} = [@_];
…		…
1145		1983
1146	sub ready {	1984	sub ready {
1147	$_[0]{_ae_sent}	1985	$_[0]{_ae_sent}
1148	}	1986	}
1149		1987
1150	sub _wait {
1151	AnyEvent->one_event while !$_[0]{_ae_sent};
1152	}
1153
1154	sub recv {	1988	sub recv {
		1989	unless ($_[0]{_ae_sent}) {
		1990	$WAITING
		1991	and Carp::croak "AnyEvent::CondVar: recursive blocking wait attempted";
		1992
		1993	local $WAITING = 1;
1155	$_[0]->_wait;	1994	$_[0]->_wait;
		1995	}
1156		1996
1157	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};	1997	$_[0]{_ae_croak}
1158	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]	1998	and Carp::croak $_[0]{_ae_croak};
		1999
		2000	wantarray
		2001	? @{ $_[0]{_ae_sent} }
		2002	: $_[0]{_ae_sent}[0]
1159	}	2003	}
1160		2004
1161	sub cb {	2005	sub cb {
1162	$_[0]{_ae_cb} = $_[1] if @_ > 1;	2006	my $cv = shift;
		2007
		2008	@_
		2009	and $cv->{_ae_cb} = shift
		2010	and $cv->{_ae_sent}
		2011	and (delete $cv->{_ae_cb})->($cv);
		2012
1163	$_[0]{_ae_cb}	2013	$cv->{_ae_cb}
1164	}	2014	}
1165		2015
1166	sub begin {	2016	sub begin {
1167	++$_[0]{_ae_counter};	2017	++$_[0]{_ae_counter};
1168	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;	2018	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
…		…
1173	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };	2023	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
1174	}	2024	}
1175		2025
1176	# undocumented/compatibility with pre-3.4	2026	# undocumented/compatibility with pre-3.4
1177	*broadcast = \&send;	2027	*broadcast = \&send;
1178	*wait = \&_wait;	2028	*wait = \&recv;
1179		2029
1180	=head1 ERROR AND EXCEPTION HANDLING	2030	=head1 ERROR AND EXCEPTION HANDLING
1181		2031
1182	In general, AnyEvent does not do any error handling - it relies on the	2032	In general, AnyEvent does not do any error handling - it relies on the
1183	caller to do that if required. The L<AnyEvent::Strict> module (see also	2033	caller to do that if required. The L<AnyEvent::Strict> module (see also
…		…
1195	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and	2045	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
1196	so on.	2046	so on.
1197		2047
1198	=head1 ENVIRONMENT VARIABLES	2048	=head1 ENVIRONMENT VARIABLES
1199		2049
1200	The following environment variables are used by this module or its	2050	AnyEvent supports a number of environment variables that tune the
1201	submodules:	2051	runtime behaviour. They are usually evaluated when AnyEvent is
		2052	loaded, initialised, or a submodule that uses them is loaded. Many of
		2053	them also cause AnyEvent to load additional modules - for example,
		2054	C<PERL_ANYEVENT_DEBUG_WRAP> causes the L<AnyEvent::Debug> module to be
		2055	loaded.
		2056
		2057	All the environment variables documented here start with
		2058	C<PERL_ANYEVENT_>, which is what AnyEvent considers its own
		2059	namespace. Other modules are encouraged (but by no means required) to use
		2060	C<PERL_ANYEVENT_SUBMODULE> if they have registered the AnyEvent::Submodule
		2061	namespace on CPAN, for any submodule. For example, L<AnyEvent::HTTP> could
		2062	be expected to use C<PERL_ANYEVENT_HTTP_PROXY> (it should not access env
		2063	variables starting with C<AE_>, see below).
		2064
		2065	All variables can also be set via the C<AE_> prefix, that is, instead
		2066	of setting C<PERL_ANYEVENT_VERBOSE> you can also set C<AE_VERBOSE>. In
		2067	case there is a clash btween anyevent and another program that uses
		2068	C<AE_something> you can set the corresponding C<PERL_ANYEVENT_something>
		2069	variable to the empty string, as those variables take precedence.
		2070
		2071	When AnyEvent is first loaded, it copies all C<AE_xxx> env variables
		2072	to their C<PERL_ANYEVENT_xxx> counterpart unless that variable already
		2073	exists. If taint mode is on, then AnyEvent will remove I<all> environment
		2074	variables starting with C<PERL_ANYEVENT_> from C<%ENV> (or replace them
		2075	with C<undef> or the empty string, if the corresaponding C<AE_> variable
		2076	is set).
		2077
		2078	The exact algorithm is currently:
		2079
		2080	1. if taint mode enabled, delete all PERL_ANYEVENT_xyz variables from %ENV
		2081	2. copy over AE_xyz to PERL_ANYEVENT_xyz unless the latter alraedy exists
		2082	3. if taint mode enabled, set all PERL_ANYEVENT_xyz variables to undef.
		2083
		2084	This ensures that child processes will not see the C<AE_> variables.
		2085
		2086	The following environment variables are currently known to AnyEvent:
1202		2087
1203	=over 4	2088	=over 4
1204		2089
1205	=item C<PERL_ANYEVENT_VERBOSE>	2090	=item C<PERL_ANYEVENT_VERBOSE>
1206		2091
1207	By default, AnyEvent will be completely silent except in fatal	2092	By default, AnyEvent will log messages with loglevel C<4> (C<error>) or
1208	conditions. You can set this environment variable to make AnyEvent more	2093	higher (see L<AnyEvent::Log>). You can set this environment variable to a
1209	talkative.	2094	numerical loglevel to make AnyEvent more (or less) talkative.
1210		2095
		2096	If you want to do more than just set the global logging level
		2097	you should have a look at C<PERL_ANYEVENT_LOG>, which allows much more
		2098	complex specifications.
		2099
		2100	When set to C<0> (C<off>), then no messages whatsoever will be logged with
		2101	everything else at defaults.
		2102
1211	When set to C<1> or higher, causes AnyEvent to warn about unexpected	2103	When set to C<5> or higher (C<warn>), AnyEvent warns about unexpected
1212	conditions, such as not being able to load the event model specified by	2104	conditions, such as not being able to load the event model specified by
1213	C<PERL_ANYEVENT_MODEL>.	2105	C<PERL_ANYEVENT_MODEL>, or a guard callback throwing an exception - this
		2106	is the minimum recommended level for use during development.
1214		2107
1215	When set to C<2> or higher, cause AnyEvent to report to STDERR which event	2108	When set to C<7> or higher (info), AnyEvent reports which event model it
1216	model it chooses.	2109	chooses.
		2110
		2111	When set to C<8> or higher (debug), then AnyEvent will report extra
		2112	information on which optional modules it loads and how it implements
		2113	certain features.
		2114
		2115	=item C<PERL_ANYEVENT_LOG>
		2116
		2117	Accepts rather complex logging specifications. For example, you could log
		2118	all C<debug> messages of some module to stderr, warnings and above to
		2119	stderr, and errors and above to syslog, with:
		2120
		2121	PERL_ANYEVENT_LOG=Some::Module=debug,+log:filter=warn,+%syslog:%syslog=error,syslog
		2122
		2123	For the rather extensive details, see L<AnyEvent::Log>.
		2124
		2125	This variable is evaluated when AnyEvent (or L<AnyEvent::Log>) is loaded,
		2126	so will take effect even before AnyEvent has initialised itself.
		2127
		2128	Note that specifying this environment variable causes the L<AnyEvent::Log>
		2129	module to be loaded, while C<PERL_ANYEVENT_VERBOSE> does not, so only
		2130	using the latter saves a few hundred kB of memory unless a module
		2131	explicitly needs the extra features of AnyEvent::Log.
1217		2132
1218	=item C<PERL_ANYEVENT_STRICT>	2133	=item C<PERL_ANYEVENT_STRICT>
1219		2134
1220	AnyEvent does not do much argument checking by default, as thorough	2135	AnyEvent does not do much argument checking by default, as thorough
1221	argument checking is very costly. Setting this variable to a true value	2136	argument checking is very costly. Setting this variable to a true value
1222	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly	2137	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
1223	check the arguments passed to most method calls. If it finds any problems	2138	check the arguments passed to most method calls. If it finds any problems,
1224	it will croak.	2139	it will croak.
1225		2140
1226	In other words, enables "strict" mode.	2141	In other words, enables "strict" mode.
1227		2142
1228	Unlike C<use strict>, it is definitely recommended ot keep it off in	2143	Unlike C<use strict> (or its modern cousin, C<< use L<common::sense>
1229	production. Keeping C<PERL_ANYEVENT_STRICT=1> in your environment while	2144	>>, it is definitely recommended to keep it off in production. Keeping
1230	developing programs can be very useful, however.	2145	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		2146	can be very useful, however.
		2147
		2148	=item C<PERL_ANYEVENT_DEBUG_SHELL>
		2149
		2150	If this env variable is nonempty, then its contents will be interpreted by
		2151	C<AnyEvent::Socket::parse_hostport> and C<AnyEvent::Debug::shell> (after
		2152	replacing every occurance of C<$$> by the process pid). The shell object
		2153	is saved in C<$AnyEvent::Debug::SHELL>.
		2154
		2155	This happens when the first watcher is created.
		2156
		2157	For example, to bind a debug shell on a unix domain socket in
		2158	F<< /tmp/debug<pid>.sock >>, you could use this:
		2159
		2160	PERL_ANYEVENT_DEBUG_SHELL=/tmp/debug\$\$.sock perlprog
		2161	# connect with e.g.: socat readline /tmp/debug123.sock
		2162
		2163	Or to bind to tcp port 4545 on localhost:
		2164
		2165	PERL_ANYEVENT_DEBUG_SHELL=127.0.0.1:4545 perlprog
		2166	# connect with e.g.: telnet localhost 4545
		2167
		2168	Note that creating sockets in F</tmp> or on localhost is very unsafe on
		2169	multiuser systems.
		2170
		2171	=item C<PERL_ANYEVENT_DEBUG_WRAP>
		2172
		2173	Can be set to C<0>, C<1> or C<2> and enables wrapping of all watchers for
		2174	debugging purposes. See C<AnyEvent::Debug::wrap> for details.
1231		2175
1232	=item C<PERL_ANYEVENT_MODEL>	2176	=item C<PERL_ANYEVENT_MODEL>
1233		2177
1234	This can be used to specify the event model to be used by AnyEvent, before	2178	This can be used to specify the event model to be used by AnyEvent, before
1235	auto detection and -probing kicks in. It must be a string consisting	2179	auto detection and -probing kicks in.
1236	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended	2180
		2181	It normally is a string consisting entirely of ASCII letters (e.g. C<EV>
		2182	or C<IOAsync>). The string C<AnyEvent::Impl::> gets prepended and the
1237	and the resulting module name is loaded and if the load was successful,	2183	resulting module name is loaded and - if the load was successful - used as
1238	used as event model. If it fails to load AnyEvent will proceed with	2184	event model backend. If it fails to load then AnyEvent will proceed with
1239	auto detection and -probing.	2185	auto detection and -probing.
1240		2186
1241	This functionality might change in future versions.	2187	If the string ends with C<::> instead (e.g. C<AnyEvent::Impl::EV::>) then
		2188	nothing gets prepended and the module name is used as-is (hint: C<::> at
		2189	the end of a string designates a module name and quotes it appropriately).
1242		2190
1243	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you	2191	For example, to force the pure perl model (L<AnyEvent::Loop::Perl>) you
1244	could start your program like this:	2192	could start your program like this:
1245		2193
1246	PERL_ANYEVENT_MODEL=Perl perl ...	2194	PERL_ANYEVENT_MODEL=Perl perl ...
		2195
		2196	=item C<PERL_ANYEVENT_IO_MODEL>
		2197
		2198	The current file I/O model - see L<AnyEvent::IO> for more info.
		2199
		2200	At the moment, only C<Perl> (small, pure-perl, synchronous) and
		2201	C<IOAIO> (truly asynchronous) are supported. The default is C<IOAIO> if
		2202	L<AnyEvent::AIO> can be loaded, otherwise it is C<Perl>.
1247		2203
1248	=item C<PERL_ANYEVENT_PROTOCOLS>	2204	=item C<PERL_ANYEVENT_PROTOCOLS>
1249		2205
1250	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences	2206	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
1251	for IPv4 or IPv6. The default is unspecified (and might change, or be the result	2207	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
…		…
1256	used, and preference will be given to protocols mentioned earlier in the	2212	used, and preference will be given to protocols mentioned earlier in the
1257	list.	2213	list.
1258		2214
1259	This variable can effectively be used for denial-of-service attacks	2215	This variable can effectively be used for denial-of-service attacks
1260	against local programs (e.g. when setuid), although the impact is likely	2216	against local programs (e.g. when setuid), although the impact is likely
1261	small, as the program has to handle connection errors already-	2217	small, as the program has to handle connection and other failures anyways.
1262		2218
1263	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,	2219	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
1264	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>	2220	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
1265	- only support IPv4, never try to resolve or contact IPv6	2221	- only support IPv4, never try to resolve or contact IPv6
1266	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or	2222	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
1267	IPv6, but prefer IPv6 over IPv4.	2223	IPv6, but prefer IPv6 over IPv4.
1268		2224
		2225	=item C<PERL_ANYEVENT_HOSTS>
		2226
		2227	This variable, if specified, overrides the F</etc/hosts> file used by
		2228	L<AnyEvent::Socket>C<::resolve_sockaddr>, i.e. hosts aliases will be read
		2229	from that file instead.
		2230
1269	=item C<PERL_ANYEVENT_EDNS0>	2231	=item C<PERL_ANYEVENT_EDNS0>
1270		2232
1271	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension	2233	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension for
1272	for DNS. This extension is generally useful to reduce DNS traffic, but	2234	DNS. This extension is generally useful to reduce DNS traffic, especially
1273	some (broken) firewalls drop such DNS packets, which is why it is off by	2235	when DNSSEC is involved, but some (broken) firewalls drop such DNS
1274	default.	2236	packets, which is why it is off by default.
1275		2237
1276	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce	2238	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
1277	EDNS0 in its DNS requests.	2239	EDNS0 in its DNS requests.
1278		2240
1279	=item C<PERL_ANYEVENT_MAX_FORKS>	2241	=item C<PERL_ANYEVENT_MAX_FORKS>
1280		2242
1281	The maximum number of child processes that C<AnyEvent::Util::fork_call>	2243	The maximum number of child processes that C<AnyEvent::Util::fork_call>
1282	will create in parallel.	2244	will create in parallel.
		2245
		2246	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		2247
		2248	The default value for the C<max_outstanding> parameter for the default DNS
		2249	resolver - this is the maximum number of parallel DNS requests that are
		2250	sent to the DNS server.
		2251
		2252	=item C<PERL_ANYEVENT_MAX_SIGNAL_LATENCY>
		2253
		2254	Perl has inherently racy signal handling (you can basically choose between
		2255	losing signals and memory corruption) - pure perl event loops (including
		2256	C<AnyEvent::Loop>, when C<Async::Interrupt> isn't available) therefore
		2257	have to poll regularly to avoid losing signals.
		2258
		2259	Some event loops are racy, but don't poll regularly, and some event loops
		2260	are written in C but are still racy. For those event loops, AnyEvent
		2261	installs a timer that regularly wakes up the event loop.
		2262
		2263	By default, the interval for this timer is C<10> seconds, but you can
		2264	override this delay with this environment variable (or by setting
		2265	the C<$AnyEvent::MAX_SIGNAL_LATENCY> variable before creating signal
		2266	watchers).
		2267
		2268	Lower values increase CPU (and energy) usage, higher values can introduce
		2269	long delays when reaping children or waiting for signals.
		2270
		2271	The L<AnyEvent::Async> module, if available, will be used to avoid this
		2272	polling (with most event loops).
		2273
		2274	=item C<PERL_ANYEVENT_RESOLV_CONF>
		2275
		2276	The absolute path to a F<resolv.conf>-style file to use instead of
		2277	F</etc/resolv.conf> (or the OS-specific configuration) in the default
		2278	resolver, or the empty string to select the default configuration.
		2279
		2280	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		2281
		2282	When neither C<ca_file> nor C<ca_path> was specified during
		2283	L<AnyEvent::TLS> context creation, and either of these environment
		2284	variables are nonempty, they will be used to specify CA certificate
		2285	locations instead of a system-dependent default.
		2286
		2287	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		2288
		2289	When these are set to C<1>, then the respective modules are not
		2290	loaded. Mostly good for testing AnyEvent itself.
1283		2291
1284	=back	2292	=back
1285		2293
1286	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	2294	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
1287		2295
…		…
1345	warn "read: $input\n"; # output what has been read	2353	warn "read: $input\n"; # output what has been read
1346	$cv->send if $input =~ /^q/i; # quit program if /^q/i	2354	$cv->send if $input =~ /^q/i; # quit program if /^q/i
1347	},	2355	},
1348	);	2356	);
1349		2357
1350	my $time_watcher; # can only be used once
1351
1352	sub new_timer {
1353	$timer = AnyEvent->timer (after => 1, cb => sub {	2358	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
1354	warn "timeout\n"; # print 'timeout' about every second	2359	warn "timeout\n"; # print 'timeout' at most every second
1355	&new_timer; # and restart the time
1356	});	2360	});
1357	}
1358
1359	new_timer; # create first timer
1360		2361
1361	$cv->recv; # wait until user enters /^q/i	2362	$cv->recv; # wait until user enters /^q/i
1362		2363
1363	=head1 REAL-WORLD EXAMPLE	2364	=head1 REAL-WORLD EXAMPLE
1364		2365
…		…
1437		2438
1438	The actual code goes further and collects all errors (C<die>s, exceptions)	2439	The actual code goes further and collects all errors (C<die>s, exceptions)
1439	that occurred during request processing. The C<result> method detects	2440	that occurred during request processing. The C<result> method detects
1440	whether an exception as thrown (it is stored inside the $txn object)	2441	whether an exception as thrown (it is stored inside the $txn object)
1441	and just throws the exception, which means connection errors and other	2442	and just throws the exception, which means connection errors and other
1442	problems get reported tot he code that tries to use the result, not in a	2443	problems get reported to the code that tries to use the result, not in a
1443	random callback.	2444	random callback.
1444		2445
1445	All of this enables the following usage styles:	2446	All of this enables the following usage styles:
1446		2447
1447	1. Blocking:	2448	1. Blocking:
…		…
1495	through AnyEvent. The benchmark creates a lot of timers (with a zero	2496	through AnyEvent. The benchmark creates a lot of timers (with a zero
1496	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,	2497	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
1497	which it is), lets them fire exactly once and destroys them again.	2498	which it is), lets them fire exactly once and destroys them again.
1498		2499
1499	Source code for this benchmark is found as F<eg/bench> in the AnyEvent	2500	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
1500	distribution.	2501	distribution. It uses the L<AE> interface, which makes a real difference
		2502	for the EV and Perl backends only.
1501		2503
1502	=head3 Explanation of the columns	2504	=head3 Explanation of the columns
1503		2505
1504	I<watcher> is the number of event watchers created/destroyed. Since	2506	I<watcher> is the number of event watchers created/destroyed. Since
1505	different event models feature vastly different performances, each event	2507	different event models feature vastly different performances, each event
…		…
1526	watcher.	2528	watcher.
1527		2529
1528	=head3 Results	2530	=head3 Results
1529		2531
1530	name watchers bytes create invoke destroy comment	2532	name watchers bytes create invoke destroy comment
1531	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	2533	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
1532	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	2534	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
1533	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	2535	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
1534	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	2536	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
1535	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	2537	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
1536	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers	2538	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
		2539	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
		2540	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
1537	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	2541	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
1538	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	2542	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
1539	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	2543	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
1540	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	2544	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
1541		2545
1542	=head3 Discussion	2546	=head3 Discussion
1543		2547
1544	The benchmark does I<not> measure scalability of the event loop very	2548	The benchmark does I<not> measure scalability of the event loop very
1545	well. For example, a select-based event loop (such as the pure perl one)	2549	well. For example, a select-based event loop (such as the pure perl one)
…		…
1557	benchmark machine, handling an event takes roughly 1600 CPU cycles with	2561	benchmark machine, handling an event takes roughly 1600 CPU cycles with
1558	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU	2562	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
1559	cycles with POE.	2563	cycles with POE.
1560		2564
1561	C<EV> is the sole leader regarding speed and memory use, which are both	2565	C<EV> is the sole leader regarding speed and memory use, which are both
1562	maximal/minimal, respectively. Even when going through AnyEvent, it uses	2566	maximal/minimal, respectively. When using the L<AE> API there is zero
		2567	overhead (when going through the AnyEvent API create is about 5-6 times
		2568	slower, with other times being equal, so still uses far less memory than
1563	far less memory than any other event loop and is still faster than Event	2569	any other event loop and is still faster than Event natively).
1564	natively.
1565		2570
1566	The pure perl implementation is hit in a few sweet spots (both the	2571	The pure perl implementation is hit in a few sweet spots (both the
1567	constant timeout and the use of a single fd hit optimisations in the perl	2572	constant timeout and the use of a single fd hit optimisations in the perl
1568	interpreter and the backend itself). Nevertheless this shows that it	2573	interpreter and the backend itself). Nevertheless this shows that it
1569	adds very little overhead in itself. Like any select-based backend its	2574	adds very little overhead in itself. Like any select-based backend its
1570	performance becomes really bad with lots of file descriptors (and few of	2575	performance becomes really bad with lots of file descriptors (and few of
1571	them active), of course, but this was not subject of this benchmark.	2576	them active), of course, but this was not subject of this benchmark.
1572		2577
1573	The C<Event> module has a relatively high setup and callback invocation	2578	The C<Event> module has a relatively high setup and callback invocation
1574	cost, but overall scores in on the third place.	2579	cost, but overall scores in on the third place.
		2580
		2581	C<IO::Async> performs admirably well, about on par with C<Event>, even
		2582	when using its pure perl backend.
1575		2583
1576	C<Glib>'s memory usage is quite a bit higher, but it features a	2584	C<Glib>'s memory usage is quite a bit higher, but it features a
1577	faster callback invocation and overall ends up in the same class as	2585	faster callback invocation and overall ends up in the same class as
1578	C<Event>. However, Glib scales extremely badly, doubling the number of	2586	C<Event>. However, Glib scales extremely badly, doubling the number of
1579	watchers increases the processing time by more than a factor of four,	2587	watchers increases the processing time by more than a factor of four,
…		…
1614	(even when used without AnyEvent), but most event loops have acceptable	2622	(even when used without AnyEvent), but most event loops have acceptable
1615	performance with or without AnyEvent.	2623	performance with or without AnyEvent.
1616		2624
1617	=item * The overhead AnyEvent adds is usually much smaller than the overhead of	2625	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
1618	the actual event loop, only with extremely fast event loops such as EV	2626	the actual event loop, only with extremely fast event loops such as EV
1619	adds AnyEvent significant overhead.	2627	does AnyEvent add significant overhead.
1620		2628
1621	=item * You should avoid POE like the plague if you want performance or	2629	=item * You should avoid POE like the plague if you want performance or
1622	reasonable memory usage.	2630	reasonable memory usage.
1623		2631
1624	=back	2632	=back
…		…
1640	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100	2648	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
1641	(1%) are active. This mirrors the activity of large servers with many	2649	(1%) are active. This mirrors the activity of large servers with many
1642	connections, most of which are idle at any one point in time.	2650	connections, most of which are idle at any one point in time.
1643		2651
1644	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent	2652	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
1645	distribution.	2653	distribution. It uses the L<AE> interface, which makes a real difference
		2654	for the EV and Perl backends only.
1646		2655
1647	=head3 Explanation of the columns	2656	=head3 Explanation of the columns
1648		2657
1649	I<sockets> is the number of sockets, and twice the number of "servers" (as	2658	I<sockets> is the number of sockets, and twice the number of "servers" (as
1650	each server has a read and write socket end).	2659	each server has a read and write socket end).
…		…
1657	it to another server. This includes deleting the old timeout and creating	2666	it to another server. This includes deleting the old timeout and creating
1658	a new one that moves the timeout into the future.	2667	a new one that moves the timeout into the future.
1659		2668
1660	=head3 Results	2669	=head3 Results
1661		2670
1662	name sockets create request	2671	name sockets create request
1663	EV 20000 69.01 11.16	2672	EV 20000 62.66 7.99
1664	Perl 20000 73.32 35.87	2673	Perl 20000 68.32 32.64
1665	Event 20000 212.62 257.32	2674	IOAsync 20000 174.06 101.15 epoll
1666	Glib 20000 651.16 1896.30	2675	IOAsync 20000 174.67 610.84 poll
		2676	Event 20000 202.69 242.91
		2677	Glib 20000 557.01 1689.52
1667	POE 20000 349.67 12317.24 uses POE::Loop::Event	2678	POE 20000 341.54 12086.32 uses POE::Loop::Event
1668		2679
1669	=head3 Discussion	2680	=head3 Discussion
1670		2681
1671	This benchmark I<does> measure scalability and overall performance of the	2682	This benchmark I<does> measure scalability and overall performance of the
1672	particular event loop.	2683	particular event loop.
…		…
1674	EV is again fastest. Since it is using epoll on my system, the setup time	2685	EV is again fastest. Since it is using epoll on my system, the setup time
1675	is relatively high, though.	2686	is relatively high, though.
1676		2687
1677	Perl surprisingly comes second. It is much faster than the C-based event	2688	Perl surprisingly comes second. It is much faster than the C-based event
1678	loops Event and Glib.	2689	loops Event and Glib.
		2690
		2691	IO::Async performs very well when using its epoll backend, and still quite
		2692	good compared to Glib when using its pure perl backend.
1679		2693
1680	Event suffers from high setup time as well (look at its code and you will	2694	Event suffers from high setup time as well (look at its code and you will
1681	understand why). Callback invocation also has a high overhead compared to	2695	understand why). Callback invocation also has a high overhead compared to
1682	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event	2696	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
1683	uses select or poll in basically all documented configurations.	2697	uses select or poll in basically all documented configurations.
…		…
1746	=item * C-based event loops perform very well with small number of	2760	=item * C-based event loops perform very well with small number of
1747	watchers, as the management overhead dominates.	2761	watchers, as the management overhead dominates.
1748		2762
1749	=back	2763	=back
1750		2764
		2765	=head2 THE IO::Lambda BENCHMARK
		2766
		2767	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2768	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2769	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2770	shouldn't come as a surprise to anybody). As such, the benchmark is
		2771	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2772	very optimal. But how would AnyEvent compare when used without the extra
		2773	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2774
		2775	The benchmark itself creates an echo-server, and then, for 500 times,
		2776	connects to the echo server, sends a line, waits for the reply, and then
		2777	creates the next connection. This is a rather bad benchmark, as it doesn't
		2778	test the efficiency of the framework or much non-blocking I/O, but it is a
		2779	benchmark nevertheless.
		2780
		2781	name runtime
		2782	Lambda/select 0.330 sec
		2783	+ optimized 0.122 sec
		2784	Lambda/AnyEvent 0.327 sec
		2785	+ optimized 0.138 sec
		2786	Raw sockets/select 0.077 sec
		2787	POE/select, components 0.662 sec
		2788	POE/select, raw sockets 0.226 sec
		2789	POE/select, optimized 0.404 sec
		2790
		2791	AnyEvent/select/nb 0.085 sec
		2792	AnyEvent/EV/nb 0.068 sec
		2793	+state machine 0.134 sec
		2794
		2795	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2796	benchmarks actually make blocking connects and use 100% blocking I/O,
		2797	defeating the purpose of an event-based solution. All of the newly
		2798	written AnyEvent benchmarks use 100% non-blocking connects (using
		2799	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2800	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2801	generally require a lot more bookkeeping and event handling than blocking
		2802	connects (which involve a single syscall only).
		2803
		2804	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2805	offers similar expressive power as POE and IO::Lambda, using conventional
		2806	Perl syntax. This means that both the echo server and the client are 100%
		2807	non-blocking, further placing it at a disadvantage.
		2808
		2809	As you can see, the AnyEvent + EV combination even beats the
		2810	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2811	backend easily beats IO::Lambda and POE.
		2812
		2813	And even the 100% non-blocking version written using the high-level (and
		2814	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda
		2815	higher level ("unoptimised") abstractions by a large margin, even though
		2816	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
		2817
		2818	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2819	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2820	part of the IO::Lambda distribution and were used without any changes.
		2821
		2822
		2823	=head1 SIGNALS
		2824
		2825	AnyEvent currently installs handlers for these signals:
		2826
		2827	=over 4
		2828
		2829	=item SIGCHLD
		2830
		2831	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2832	emulation for event loops that do not support them natively. Also, some
		2833	event loops install a similar handler.
		2834
		2835	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2836	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2837
		2838	=item SIGPIPE
		2839
		2840	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2841	when AnyEvent gets loaded.
		2842
		2843	The rationale for this is that AnyEvent users usually do not really depend
		2844	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2845	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2846	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2847	some random socket.
		2848
		2849	The rationale for installing a no-op handler as opposed to ignoring it is
		2850	that this way, the handler will be restored to defaults on exec.
		2851
		2852	Feel free to install your own handler, or reset it to defaults.
		2853
		2854	=back
		2855
		2856	=cut
		2857
		2858	undef $SIG{CHLD}
		2859	if $SIG{CHLD} eq 'IGNORE';
		2860
		2861	$SIG{PIPE} = sub { }
		2862	unless defined $SIG{PIPE};
		2863
		2864	=head1 RECOMMENDED/OPTIONAL MODULES
		2865
		2866	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2867	its built-in modules) are required to use it.
		2868
		2869	That does not mean that AnyEvent won't take advantage of some additional
		2870	modules if they are installed.
		2871
		2872	This section explains which additional modules will be used, and how they
		2873	affect AnyEvent's operation.
		2874
		2875	=over 4
		2876
		2877	=item L<Async::Interrupt>
		2878
		2879	This slightly arcane module is used to implement fast signal handling: To
		2880	my knowledge, there is no way to do completely race-free and quick
		2881	signal handling in pure perl. To ensure that signals still get
		2882	delivered, AnyEvent will start an interval timer to wake up perl (and
		2883	catch the signals) with some delay (default is 10 seconds, look for
		2884	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2885
		2886	If this module is available, then it will be used to implement signal
		2887	catching, which means that signals will not be delayed, and the event loop
		2888	will not be interrupted regularly, which is more efficient (and good for
		2889	battery life on laptops).
		2890
		2891	This affects not just the pure-perl event loop, but also other event loops
		2892	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2893
		2894	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2895	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2896	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2897	does nothing for those backends.
		2898
		2899	=item L<EV>
		2900
		2901	This module isn't really "optional", as it is simply one of the backend
		2902	event loops that AnyEvent can use. However, it is simply the best event
		2903	loop available in terms of features, speed and stability: It supports
		2904	the AnyEvent API optimally, implements all the watcher types in XS, does
		2905	automatic timer adjustments even when no monotonic clock is available,
		2906	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2907	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2908	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2909
		2910	If you only use backends that rely on another event loop (e.g. C<Tk>),
		2911	then this module will do nothing for you.
		2912
		2913	=item L<Guard>
		2914
		2915	The guard module, when used, will be used to implement
		2916	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2917	lot less memory), but otherwise doesn't affect guard operation much. It is
		2918	purely used for performance.
		2919
		2920	=item L<JSON> and L<JSON::XS>
		2921
		2922	One of these modules is required when you want to read or write JSON data
		2923	via L<AnyEvent::Handle>. L<JSON> is also written in pure-perl, but can take
		2924	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2925
		2926	=item L<Net::SSLeay>
		2927
		2928	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2929	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2930	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2931
		2932	=item L<Time::HiRes>
		2933
		2934	This module is part of perl since release 5.008. It will be used when the
		2935	chosen event library does not come with a timing source of its own. The
		2936	pure-perl event loop (L<AnyEvent::Loop>) will additionally load it to
		2937	try to use a monotonic clock for timing stability.
		2938
		2939	=item L<AnyEvent::AIO> (and L<IO::AIO>)
		2940
		2941	The default implementation of L<AnyEvent::IO> is to do I/O synchronously,
		2942	stopping programs while they access the disk, which is fine for a lot of
		2943	programs.
		2944
		2945	Installing AnyEvent::AIO (and its IO::AIO dependency) makes it switch to
		2946	a true asynchronous implementation, so event processing can continue even
		2947	while waiting for disk I/O.
		2948
		2949	=back
		2950
1751		2951
1752	=head1 FORK	2952	=head1 FORK
1753		2953
1754	Most event libraries are not fork-safe. The ones who are usually are	2954	Most event libraries are not fork-safe. The ones who are usually are
1755	because they rely on inefficient but fork-safe C<select> or C<poll>	2955	because they rely on inefficient but fork-safe C<select> or C<poll> calls
1756	calls. Only L<EV> is fully fork-aware.	2956	- higher performance APIs such as BSD's kqueue or the dreaded Linux epoll
		2957	are usually badly thought-out hacks that are incompatible with fork in
		2958	one way or another. Only L<EV> is fully fork-aware and ensures that you
		2959	continue event-processing in both parent and child (or both, if you know
		2960	what you are doing).
		2961
		2962	This means that, in general, you cannot fork and do event processing in
		2963	the child if the event library was initialised before the fork (which
		2964	usually happens when the first AnyEvent watcher is created, or the library
		2965	is loaded).
1757		2966
1758	If you have to fork, you must either do so I<before> creating your first	2967	If you have to fork, you must either do so I<before> creating your first
1759	watcher OR you must not use AnyEvent at all in the child.	2968	watcher OR you must not use AnyEvent at all in the child OR you must do
		2969	something completely out of the scope of AnyEvent (see below).
		2970
		2971	The problem of doing event processing in the parent I<and> the child
		2972	is much more complicated: even for backends that I<are> fork-aware or
		2973	fork-safe, their behaviour is not usually what you want: fork clones all
		2974	watchers, that means all timers, I/O watchers etc. are active in both
		2975	parent and child, which is almost never what you want. Using C<exec>
		2976	to start worker children from some kind of manage prrocess is usually
		2977	preferred, because it is much easier and cleaner, at the expense of having
		2978	to have another binary.
		2979
		2980	In addition to logical problems with fork, there are also implementation
		2981	problems. For example, on POSIX systems, you cannot fork at all in Perl
		2982	code if a thread (I am talking of pthreads here) was ever created in the
		2983	process, and this is just the tip of the iceberg. In general, using fork
		2984	from Perl is difficult, and attempting to use fork without an exec to
		2985	implement some kind of parallel processing is almost certainly doomed.
		2986
		2987	To safely fork and exec, you should use a module such as
		2988	L<Proc::FastSpawn> that let's you safely fork and exec new processes.
		2989
		2990	If you want to do multiprocessing using processes, you can
		2991	look at the L<AnyEvent::Fork> module (and some related modules
		2992	such as L<AnyEvent::Fork::RPC>, L<AnyEvent::Fork::Pool> and
		2993	L<AnyEvent::Fork::Remote>). This module allows you to safely create
		2994	subprocesses without any limitations - you can use X11 toolkits or
		2995	AnyEvent in the children created by L<AnyEvent::Fork> safely and without
		2996	any special precautions.
1760		2997
1761		2998
1762	=head1 SECURITY CONSIDERATIONS	2999	=head1 SECURITY CONSIDERATIONS
1763		3000
1764	AnyEvent can be forced to load any event model via	3001	AnyEvent can be forced to load any event model via
…		…
1776	use AnyEvent;	3013	use AnyEvent;
1777		3014
1778	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can	3015	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1779	be used to probe what backend is used and gain other information (which is	3016	be used to probe what backend is used and gain other information (which is
1780	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and	3017	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
1781	$ENV{PERL_ANYEGENT_STRICT}.	3018	$ENV{PERL_ANYEVENT_STRICT}.
		3019
		3020	Note that AnyEvent will remove I<all> environment variables starting with
		3021	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		3022	enabled.
1782		3023
1783		3024
1784	=head1 BUGS	3025	=head1 BUGS
1785		3026
1786	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard	3027	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
1787	to work around. If you suffer from memleaks, first upgrade to Perl 5.10	3028	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
1788	and check wether the leaks still show up. (Perl 5.10.0 has other annoying	3029	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
1789	mamleaks, such as leaking on C<map> and C<grep> but it is usually not as	3030	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
1790	pronounced).	3031	pronounced).
1791		3032
1792		3033
1793	=head1 SEE ALSO	3034	=head1 SEE ALSO
1794		3035
1795	Utility functions: L<AnyEvent::Util>.	3036	Tutorial/Introduction: L<AnyEvent::Intro>.
1796		3037
1797	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,	3038	FAQ: L<AnyEvent::FAQ>.
1798	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.	3039
		3040	Utility functions: L<AnyEvent::Util> (misc. grab-bag), L<AnyEvent::Log>
		3041	(simply logging).
		3042
		3043	Development/Debugging: L<AnyEvent::Strict> (stricter checking),
		3044	L<AnyEvent::Debug> (interactive shell, watcher tracing).
		3045
		3046	Supported event modules: L<AnyEvent::Loop>, L<EV>, L<EV::Glib>,
		3047	L<Glib::EV>, L<Event>, L<Glib::Event>, L<Glib>, L<Tk>, L<Event::Lib>,
		3048	L<Qt>, L<POE>, L<FLTK>.
1799		3049
1800	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,	3050	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
1801	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,	3051	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
1802	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,	3052	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
		3053	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>, L<Anyevent::Impl::Irssi>,
1803	L<AnyEvent::Impl::POE>.	3054	L<AnyEvent::Impl::FLTK>.
1804		3055
1805	Non-blocking file handles, sockets, TCP clients and	3056	Non-blocking handles, pipes, stream sockets, TCP clients and
1806	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>.	3057	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
		3058
		3059	Asynchronous File I/O: L<AnyEvent::IO>.
1807		3060
1808	Asynchronous DNS: L<AnyEvent::DNS>.	3061	Asynchronous DNS: L<AnyEvent::DNS>.
1809		3062
1810	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,	3063	Thread support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
1811		3064
1812	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>, L<AnyEvent::DNS>.	3065	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::IRC>,
		3066	L<AnyEvent::HTTP>.
1813		3067
1814		3068
1815	=head1 AUTHOR	3069	=head1 AUTHOR
1816		3070
1817	Marc Lehmann <schmorp@schmorp.de>	3071	Marc Lehmann <schmorp@schmorp.de>
1818	http://home.schmorp.de/	3072	http://anyevent.schmorp.de
1819		3073
1820	=cut	3074	=cut
1821		3075
1822	1	3076	1
1823		3077

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