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Revision 1.172 by root, Thu Jul 17 15:21:02 2008 UTC vs.
Revision 1.330 by root, Tue Aug 31 00:59:55 2010 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent - provide framework for multiple event loops	3	AnyEvent - the DBI of event loop programming
4		4
5	EV, Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event loops	5	EV, Event, Glib, Tk, Perl, Event::Lib, Irssi, rxvt-unicode, IO::Async, Qt
		6	and POE are various supported event loops/environments.
6		7
7	=head1 SYNOPSIS	8	=head1 SYNOPSIS
8		9
9	use AnyEvent;	10	use AnyEvent;
10		11
		12	# if you prefer function calls, look at the AE manpage for
		13	# an alternative API.
		14
		15	# file handle or descriptor readable
11	my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub {	16	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
		17
		18	# one-shot or repeating timers
		19	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
		20	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...);
		21
		22	print AnyEvent->now; # prints current event loop time
		23	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
		24
		25	# POSIX signal
		26	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
		27
		28	# child process exit
		29	my $w = AnyEvent->child (pid => $pid, cb => sub {
		30	my ($pid, $status) = @_;
12	...	31	...
13	});	32	});
14		33
15	my $w = AnyEvent->timer (after => $seconds, cb => sub {	34	# called when event loop idle (if applicable)
16	...	35	my $w = AnyEvent->idle (cb => sub { ... });
17	});
18		36
19	my $w = AnyEvent->condvar; # stores whether a condition was flagged	37	my $w = AnyEvent->condvar; # stores whether a condition was flagged
20	$w->send; # wake up current and all future recv's	38	$w->send; # wake up current and all future recv's
21	$w->recv; # enters "main loop" till $condvar gets ->send	39	$w->recv; # enters "main loop" till $condvar gets ->send
		40	# use a condvar in callback mode:
		41	$w->cb (sub { $_[0]->recv });
22		42
23	=head1 INTRODUCTION/TUTORIAL	43	=head1 INTRODUCTION/TUTORIAL
24		44
25	This manpage is mainly a reference manual. If you are interested	45	This manpage is mainly a reference manual. If you are interested
26	in a tutorial or some gentle introduction, have a look at the	46	in a tutorial or some gentle introduction, have a look at the
27	L<AnyEvent::Intro> manpage.	47	L<AnyEvent::Intro> manpage.
		48
		49	=head1 SUPPORT
		50
		51	There is a mailinglist for discussing all things AnyEvent, and an IRC
		52	channel, too.
		53
		54	See the AnyEvent project page at the B<Schmorpforge Ta-Sa Software
		55	Repository>, at L<http://anyevent.schmorp.de>, for more info.
28		56
29	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)	57	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
30		58
31	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	59	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
32	nowadays. So what is different about AnyEvent?	60	nowadays. So what is different about AnyEvent?
…		…
48	module users into the same thing by forcing them to use the same event	76	module users into the same thing by forcing them to use the same event
49	model you use.	77	model you use.
50		78
51	For modules like POE or IO::Async (which is a total misnomer as it is	79	For modules like POE or IO::Async (which is a total misnomer as it is
52	actually doing all I/O I<synchronously>...), using them in your module is	80	actually doing all I/O I<synchronously>...), using them in your module is
53	like joining a cult: After you joined, you are dependent on them and you	81	like joining a cult: After you join, you are dependent on them and you
54	cannot use anything else, as they are simply incompatible to everything	82	cannot use anything else, as they are simply incompatible to everything
55	that isn't them. What's worse, all the potential users of your	83	that isn't them. What's worse, all the potential users of your
56	module are I<also> forced to use the same event loop you use.	84	module are I<also> forced to use the same event loop you use.
57		85
58	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	86	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
59	fine. AnyEvent + Tk works fine etc. etc. but none of these work together	87	fine. AnyEvent + Tk works fine etc. etc. but none of these work together
60	with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if	88	with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if
61	your module uses one of those, every user of your module has to use it,	89	your module uses one of those, every user of your module has to use it,
62	too. But if your module uses AnyEvent, it works transparently with all	90	too. But if your module uses AnyEvent, it works transparently with all
63	event models it supports (including stuff like IO::Async, as long as those	91	event models it supports (including stuff like IO::Async, as long as those
64	use one of the supported event loops. It is trivial to add new event loops	92	use one of the supported event loops. It is easy to add new event loops
65	to AnyEvent, too, so it is future-proof).	93	to AnyEvent, too, so it is future-proof).
66		94
67	In addition to being free of having to use I<the one and only true event	95	In addition to being free of having to use I<the one and only true event
68	model>, AnyEvent also is free of bloat and policy: with POE or similar	96	model>, AnyEvent also is free of bloat and policy: with POE or similar
69	modules, you get an enormous amount of code and strict rules you have to	97	modules, you get an enormous amount of code and strict rules you have to
70	follow. AnyEvent, on the other hand, is lean and up to the point, by only	98	follow. AnyEvent, on the other hand, is lean and to the point, by only
71	offering the functionality that is necessary, in as thin as a wrapper as	99	offering the functionality that is necessary, in as thin as a wrapper as
72	technically possible.	100	technically possible.
73		101
74	Of course, AnyEvent comes with a big (and fully optional!) toolbox	102	Of course, AnyEvent comes with a big (and fully optional!) toolbox
75	of useful functionality, such as an asynchronous DNS resolver, 100%	103	of useful functionality, such as an asynchronous DNS resolver, 100%
…		…
81	useful) and you want to force your users to use the one and only event	109	useful) and you want to force your users to use the one and only event
82	model, you should I<not> use this module.	110	model, you should I<not> use this module.
83		111
84	=head1 DESCRIPTION	112	=head1 DESCRIPTION
85		113
86	L<AnyEvent> provides an identical interface to multiple event loops. This	114	L<AnyEvent> provides a uniform interface to various event loops. This
87	allows module authors to utilise an event loop without forcing module	115	allows module authors to use event loop functionality without forcing
88	users to use the same event loop (as only a single event loop can coexist	116	module users to use a specific event loop implementation (since more
89	peacefully at any one time).	117	than one event loop cannot coexist peacefully).
90		118
91	The interface itself is vaguely similar, but not identical to the L<Event>	119	The interface itself is vaguely similar, but not identical to the L<Event>
92	module.	120	module.
93		121
94	During the first call of any watcher-creation method, the module tries	122	During the first call of any watcher-creation method, the module tries
…		…
110	use AnyEvent;	138	use AnyEvent;
111		139
112	# .. AnyEvent will likely default to Tk	140	# .. AnyEvent will likely default to Tk
113		141
114	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
115	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,
116	use AnyEvent so their modules work together with others seamlessly...	144	as very few modules hardcode event loops without announcing this very
		145	loudly.
117		146
118	The pure-perl implementation of AnyEvent is called	147	The pure-perl implementation of AnyEvent is called
119	C<AnyEvent::Impl::Perl>. Like other event modules you can load it	148	C<AnyEvent::Impl::Perl>. Like other event modules you can load it
120	explicitly and enjoy the high availability of that event loop :)	149	explicitly and enjoy the high availability of that event loop :)
121		150
…		…
128	These watchers are normal Perl objects with normal Perl lifetime. After	157	These watchers are normal Perl objects with normal Perl lifetime. After
129	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
130	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
131	is in control).	160	is in control).
132		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
133	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
134	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
135	to it).	170	to it).
136		171
137	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.
138		173
139	Many watchers either are used with "recursion" (repeating timers for	174	Many watchers either are used with "recursion" (repeating timers for
140	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.
141		176
142	An any way to achieve that is this pattern:	177	One way to achieve that is this pattern:
143		178
144	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	179	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
145	# you can use $w here, for example to undef it	180	# you can use $w here, for example to undef it
146	undef $w;	181	undef $w;
147	});	182	});
…		…
150	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
151	declared.	186	declared.
152		187
153	=head2 I/O WATCHERS	188	=head2 I/O WATCHERS
154		189
		190	$w = AnyEvent->io (
		191	fh => <filehandle_or_fileno>,
		192	poll => <"r" or "w">,
		193	cb => <callback>,
		194	);
		195
155	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
156	with the following mandatory key-value pairs as arguments:	197	with the following mandatory key-value pairs as arguments:
157		198
158	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
159	(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
160	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
161	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
162	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.
163		210
164	Although the callback might get passed parameters, their value and	211	Although the callback might get passed parameters, their value and
165	presence is undefined and you cannot rely on them. Portable AnyEvent	212	presence is undefined and you cannot rely on them. Portable AnyEvent
166	callbacks cannot use arguments passed to I/O watcher callbacks.	213	callbacks cannot use arguments passed to I/O watcher callbacks.
167		214
168	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.
169	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
170	underlying file descriptor.	217	underlying file descriptor.
171		218
172	Some event loops issue spurious readyness notifications, so you should	219	Some event loops issue spurious readiness notifications, so you should
173	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
174	handles.	221	handles.
175		222
176	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
177	watcher.	224	watcher.
…		…
182	undef $w;	229	undef $w;
183	});	230	});
184		231
185	=head2 TIME WATCHERS	232	=head2 TIME WATCHERS
186		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
187	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 >>
188	method with the following mandatory arguments:	243	method with the following mandatory arguments:
189		244
190	C<after> specifies after how many seconds (fractional values are	245	C<after> specifies after how many seconds (fractional values are
191	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
…		…
193		248
194	Although the callback might get passed parameters, their value and	249	Although the callback might get passed parameters, their value and
195	presence is undefined and you cannot rely on them. Portable AnyEvent	250	presence is undefined and you cannot rely on them. Portable AnyEvent
196	callbacks cannot use arguments passed to time watcher callbacks.	251	callbacks cannot use arguments passed to time watcher callbacks.
197		252
198	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
199	parameter, C<interval>, as a strictly positive number (> 0), then the	254	parameter, C<interval>, as a strictly positive number (> 0), then the
200	callback will be invoked regularly at that interval (in fractional	255	callback will be invoked regularly at that interval (in fractional
201	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
202	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.
203		258
204	The callback will be rescheduled before invoking the callback, but no	259	The callback will be rescheduled before invoking the callback, but no
205	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
206	only approximate.	261	only approximate.
207		262
208	Example: fire an event after 7.7 seconds.	263	Example: fire an event after 7.7 seconds.
209		264
210	my $w = AnyEvent->timer (after => 7.7, cb => sub {	265	my $w = AnyEvent->timer (after => 7.7, cb => sub {
…		…
228		283
229	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
230	use absolute time internally. This makes a difference when your clock	285	use absolute time internally. This makes a difference when your clock
231	"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
232	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
233	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.
234		289
235	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
236	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
237	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)
238	timers.	293	timers.
239		294
240	AnyEvent always prefers relative timers, if available, matching the	295	AnyEvent always prefers relative timers, if available, matching the
241	AnyEvent API.	296	AnyEvent API.
…		…
263	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
264	function to call when you want to know the current time.>	319	function to call when you want to know the current time.>
265		320
266	This function is also often faster then C<< AnyEvent->time >>, and	321	This function is also often faster then C<< AnyEvent->time >>, and
267	thus the preferred method if you want some timestamp (for example,	322	thus the preferred method if you want some timestamp (for example,
268	L<AnyEvent::Handle> uses this to update it's activity timeouts).	323	L<AnyEvent::Handle> uses this to update its activity timeouts).
269		324
270	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
271	with your timing, you can skip it without bad conscience.	326	with your timing; you can skip it without a bad conscience.
272		327
273	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>
274	and L<EV> and the following set-up:	329	and L<EV> and the following set-up:
275		330
276	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
277	time=500 (assume no other callbacks delay processing). In your callback,	332	time=500 (assume no other callbacks delay processing). In your callback,
278	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
279	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
280	after three seconds.	335	after three seconds.
281		336
…		…
299	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
300	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
301	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into	356	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
302	account.	357	account.
303		358
		359	=item AnyEvent->now_update
		360
		361	Some event loops (such as L<EV> or L<AnyEvent::Impl::Perl>) cache
		362	the current time for each loop iteration (see the discussion of L<<
		363	AnyEvent->now >>, 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
304	=back	381	=back
305		382
306	=head2 SIGNAL WATCHERS	383	=head2 SIGNAL WATCHERS
		384
		385	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
307		386
308	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
309	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
310	callback to be invoked whenever a signal occurs.	389	callback to be invoked whenever a signal occurs.
311		390
…		…
317	invocation, and callback invocation will be synchronous. Synchronous means	396	invocation, and callback invocation will be synchronous. Synchronous means
318	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,
319	but it is guaranteed not to interrupt any other callbacks.	398	but it is guaranteed not to interrupt any other callbacks.
320		399
321	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
322	between multiple watchers.	401	between multiple watchers, and AnyEvent will ensure that signals will not
		402	interrupt your program at bad times.
323		403
324	This watcher might use C<%SIG>, so programs overwriting those signals	404	This watcher might use C<%SIG> (depending on the event loop used),
325	directly will likely not work correctly.	405	so programs overwriting those signals directly will likely not work
		406	correctly.
326		407
327	Example: exit on SIGINT	408	Example: exit on SIGINT
328		409
329	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	410	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
330		411
		412	=head3 Restart Behaviour
		413
		414	While restart behaviour is up to the event loop implementation, most will
		415	not restart syscalls (that includes L<Async::Interrupt> and AnyEvent's
		416	pure perl implementation).
		417
		418	=head3 Safe/Unsafe Signals
		419
		420	Perl signals can be either "safe" (synchronous to opcode handling) or
		421	"unsafe" (asynchronous) - the former might get delayed indefinitely, the
		422	latter might corrupt your memory.
		423
		424	AnyEvent signal handlers are, in addition, synchronous to the event loop,
		425	i.e. they will not interrupt your running perl program but will only be
		426	called as part of the normal event handling (just like timer, I/O etc.
		427	callbacks, too).
		428
		429	=head3 Signal Races, Delays and Workarounds
		430
		431	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		432	callbacks to signals in a generic way, which is a pity, as you cannot
		433	do race-free signal handling in perl, requiring C libraries for
		434	this. AnyEvent will try to do its best, which means in some cases,
		435	signals will be delayed. The maximum time a signal might be delayed is
		436	specified in C<$AnyEvent::MAX_SIGNAL_LATENCY> (default: 10 seconds). This
		437	variable can be changed only before the first signal watcher is created,
		438	and should be left alone otherwise. This variable determines how often
		439	AnyEvent polls for signals (in case a wake-up was missed). Higher values
		440	will cause fewer spurious wake-ups, which is better for power and CPU
		441	saving.
		442
		443	All these problems can be avoided by installing the optional
		444	L<Async::Interrupt> module, which works with most event loops. It will not
		445	work with inherently broken event loops such as L<Event> or L<Event::Lib>
		446	(and not with L<POE> currently, as POE does its own workaround with
		447	one-second latency). For those, you just have to suffer the delays.
		448
331	=head2 CHILD PROCESS WATCHERS	449	=head2 CHILD PROCESS WATCHERS
332		450
		451	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		452
333	You can also watch on a child process exit and catch its exit status.	453	You can also watch for a child process exit and catch its exit status.
334		454
335	The child process is specified by the C<pid> argument (if set to C<0>, it	455	The child process is specified by the C<pid> argument (on some backends,
336	watches for any child process exit). The watcher will trigger as often	456	using C<0> watches for any child process exit, on others this will
337	as status change for the child are received. This works by installing a	457	croak). The watcher will be triggered only when the child process has
338	signal handler for C<SIGCHLD>. The callback will be called with the pid	458	finished and an exit status is available, not on any trace events
339	and exit status (as returned by waitpid), so unlike other watcher types,	459	(stopped/continued).
340	you I<can> rely on child watcher callback arguments.	460
		461	The callback will be called with the pid and exit status (as returned by
		462	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		463	callback arguments.
		464
		465	This watcher type works by installing a signal handler for C<SIGCHLD>,
		466	and since it cannot be shared, nothing else should use SIGCHLD or reap
		467	random child processes (waiting for specific child processes, e.g. inside
		468	C<system>, is just fine).
341		469
342	There is a slight catch to child watchers, however: you usually start them	470	There is a slight catch to child watchers, however: you usually start them
343	I<after> the child process was created, and this means the process could	471	I<after> the child process was created, and this means the process could
344	have exited already (and no SIGCHLD will be sent anymore).	472	have exited already (and no SIGCHLD will be sent anymore).
345		473
346	Not all event models handle this correctly (POE doesn't), but even for	474	Not all event models handle this correctly (neither POE nor IO::Async do,
		475	see their AnyEvent::Impl manpages for details), but even for event models
347	event models that I<do> handle this correctly, they usually need to be	476	that I<do> handle this correctly, they usually need to be loaded before
348	loaded before the process exits (i.e. before you fork in the first place).	477	the process exits (i.e. before you fork in the first place). AnyEvent's
		478	pure perl event loop handles all cases correctly regardless of when you
		479	start the watcher.
349		480
350	This means you cannot create a child watcher as the very first thing in an	481	This means you cannot create a child watcher as the very first
351	AnyEvent program, you I<have> to create at least one watcher before you	482	thing in an AnyEvent program, you I<have> to create at least one
352	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).	483	watcher before you C<fork> the child (alternatively, you can call
		484	C<AnyEvent::detect>).
		485
		486	As most event loops do not support waiting for child events, they will be
		487	emulated by AnyEvent in most cases, in which the latency and race problems
		488	mentioned in the description of signal watchers apply.
353		489
354	Example: fork a process and wait for it	490	Example: fork a process and wait for it
355		491
356	my $done = AnyEvent->condvar;	492	my $done = AnyEvent->condvar;
357		493
…		…
367	);	503	);
368		504
369	# do something else, then wait for process exit	505	# do something else, then wait for process exit
370	$done->recv;	506	$done->recv;
371		507
		508	=head2 IDLE WATCHERS
		509
		510	$w = AnyEvent->idle (cb => <callback>);
		511
		512	This will repeatedly invoke the callback after the process becomes idle,
		513	until either the watcher is destroyed or new events have been detected.
		514
		515	Idle watchers are useful when there is a need to do something, but it
		516	is not so important (or wise) to do it instantly. The callback will be
		517	invoked only when there is "nothing better to do", which is usually
		518	defined as "all outstanding events have been handled and no new events
		519	have been detected". That means that idle watchers ideally get invoked
		520	when the event loop has just polled for new events but none have been
		521	detected. Instead of blocking to wait for more events, the idle watchers
		522	will be invoked.
		523
		524	Unfortunately, most event loops do not really support idle watchers (only
		525	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		526	will simply call the callback "from time to time".
		527
		528	Example: read lines from STDIN, but only process them when the
		529	program is otherwise idle:
		530
		531	my @lines; # read data
		532	my $idle_w;
		533	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		534	push @lines, scalar <STDIN>;
		535
		536	# start an idle watcher, if not already done
		537	$idle_w ||= AnyEvent->idle (cb => sub {
		538	# handle only one line, when there are lines left
		539	if (my $line = shift @lines) {
		540	print "handled when idle: $line";
		541	} else {
		542	# otherwise disable the idle watcher again
		543	undef $idle_w;
		544	}
		545	});
		546	});
		547
372	=head2 CONDITION VARIABLES	548	=head2 CONDITION VARIABLES
		549
		550	$cv = AnyEvent->condvar;
		551
		552	$cv->send (<list>);
		553	my @res = $cv->recv;
373		554
374	If you are familiar with some event loops you will know that all of them	555	If you are familiar with some event loops you will know that all of them
375	require you to run some blocking "loop", "run" or similar function that	556	require you to run some blocking "loop", "run" or similar function that
376	will actively watch for new events and call your callbacks.	557	will actively watch for new events and call your callbacks.
377		558
378	AnyEvent is different, it expects somebody else to run the event loop and	559	AnyEvent is slightly different: it expects somebody else to run the event
379	will only block when necessary (usually when told by the user).	560	loop and will only block when necessary (usually when told by the user).
380		561
381	The instrument to do that is called a "condition variable", so called	562	The tool to do that is called a "condition variable", so called because
382	because they represent a condition that must become true.	563	they represent a condition that must become true.
		564
		565	Now is probably a good time to look at the examples further below.
383		566
384	Condition variables can be created by calling the C<< AnyEvent->condvar	567	Condition variables can be created by calling the C<< AnyEvent->condvar
385	>> method, usually without arguments. The only argument pair allowed is	568	>> method, usually without arguments. The only argument pair allowed is
386	C<cb>, which specifies a callback to be called when the condition variable	569	C<cb>, which specifies a callback to be called when the condition variable
387	becomes true.	570	becomes true, with the condition variable as the first argument (but not
		571	the results).
388		572
389	After creation, the condition variable is "false" until it becomes "true"	573	After creation, the condition variable is "false" until it becomes "true"
390	by calling the C<send> method (or calling the condition variable as if it	574	by calling the C<send> method (or calling the condition variable as if it
391	were a callback, read about the caveats in the description for the C<<	575	were a callback, read about the caveats in the description for the C<<
392	->send >> method).	576	->send >> method).
393		577
394	Condition variables are similar to callbacks, except that you can	578	Since condition variables are the most complex part of the AnyEvent API, here are
395	optionally wait for them. They can also be called merge points - points	579	some different mental models of what they are - pick the ones you can connect to:
396	in time where multiple outstanding events have been processed. And yet	580
397	another way to call them is transactions - each condition variable can be	581	=over 4
398	used to represent a transaction, which finishes at some point and delivers	582
399	a result.	583	=item * Condition variables are like callbacks - you can call them (and pass them instead
		584	of callbacks). Unlike callbacks however, you can also wait for them to be called.
		585
		586	=item * Condition variables are signals - one side can emit or send them,
		587	the other side can wait for them, or install a handler that is called when
		588	the signal fires.
		589
		590	=item * Condition variables are like "Merge Points" - points in your program
		591	where you merge multiple independent results/control flows into one.
		592
		593	=item * Condition variables represent a transaction - functions that start
		594	some kind of transaction can return them, leaving the caller the choice
		595	between waiting in a blocking fashion, or setting a callback.
		596
		597	=item * Condition variables represent future values, or promises to deliver
		598	some result, long before the result is available.
		599
		600	=back
400		601
401	Condition variables are very useful to signal that something has finished,	602	Condition variables are very useful to signal that something has finished,
402	for example, if you write a module that does asynchronous http requests,	603	for example, if you write a module that does asynchronous http requests,
403	then a condition variable would be the ideal candidate to signal the	604	then a condition variable would be the ideal candidate to signal the
404	availability of results. The user can either act when the callback is	605	availability of results. The user can either act when the callback is
…		…
417		618
418	Condition variables are represented by hash refs in perl, and the keys	619	Condition variables are represented by hash refs in perl, and the keys
419	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing	620	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
420	easy (it is often useful to build your own transaction class on top of	621	easy (it is often useful to build your own transaction class on top of
421	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call	622	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
422	it's C<new> method in your own C<new> method.	623	its C<new> method in your own C<new> method.
423		624
424	There are two "sides" to a condition variable - the "producer side" which	625	There are two "sides" to a condition variable - the "producer side" which
425	eventually calls C<< -> send >>, and the "consumer side", which waits	626	eventually calls C<< -> send >>, and the "consumer side", which waits
426	for the send to occur.	627	for the send to occur.
427		628
428	Example: wait for a timer.	629	Example: wait for a timer.
429		630
430	# wait till the result is ready	631	# condition: "wait till the timer is fired"
431	my $result_ready = AnyEvent->condvar;	632	my $timer_fired = AnyEvent->condvar;
432		633
433	# do something such as adding a timer	634	# create the timer - we could wait for, say
434	# or socket watcher the calls $result_ready->send	635	# a handle becomign ready, or even an
435	# when the "result" is ready.	636	# AnyEvent::HTTP request to finish, but
436	# in this case, we simply use a timer:	637	# in this case, we simply use a timer:
437	my $w = AnyEvent->timer (	638	my $w = AnyEvent->timer (
438	after => 1,	639	after => 1,
439	cb => sub { $result_ready->send },	640	cb => sub { $timer_fired->send },
440	);	641	);
441		642
442	# this "blocks" (while handling events) till the callback	643	# this "blocks" (while handling events) till the callback
443	# calls send	644	# calls ->send
444	$result_ready->recv;	645	$timer_fired->recv;
445		646
446	Example: wait for a timer, but take advantage of the fact that	647	Example: wait for a timer, but take advantage of the fact that condition
447	condition variables are also code references.	648	variables are also callable directly.
448		649
449	my $done = AnyEvent->condvar;	650	my $done = AnyEvent->condvar;
450	my $delay = AnyEvent->timer (after => 5, cb => $done);	651	my $delay = AnyEvent->timer (after => 5, cb => $done);
451	$done->recv;	652	$done->recv;
		653
		654	Example: Imagine an API that returns a condvar and doesn't support
		655	callbacks. This is how you make a synchronous call, for example from
		656	the main program:
		657
		658	use AnyEvent::CouchDB;
		659
		660	...
		661
		662	my @info = $couchdb->info->recv;
		663
		664	And this is how you would just set a callback to be called whenever the
		665	results are available:
		666
		667	$couchdb->info->cb (sub {
		668	my @info = $_[0]->recv;
		669	});
452		670
453	=head3 METHODS FOR PRODUCERS	671	=head3 METHODS FOR PRODUCERS
454		672
455	These methods should only be used by the producing side, i.e. the	673	These methods should only be used by the producing side, i.e. the
456	code/module that eventually sends the signal. Note that it is also	674	code/module that eventually sends the signal. Note that it is also
…		…
469	immediately from within send.	687	immediately from within send.
470		688
471	Any arguments passed to the C<send> call will be returned by all	689	Any arguments passed to the C<send> call will be returned by all
472	future C<< ->recv >> calls.	690	future C<< ->recv >> calls.
473		691
474	Condition variables are overloaded so one can call them directly	692	Condition variables are overloaded so one can call them directly (as if
475	(as a code reference). Calling them directly is the same as calling	693	they were a code reference). Calling them directly is the same as calling
476	C<send>. Note, however, that many C-based event loops do not handle	694	C<send>.
477	overloading, so as tempting as it may be, passing a condition variable
478	instead of a callback does not work. Both the pure perl and EV loops
479	support overloading, however, as well as all functions that use perl to
480	invoke a callback (as in L<AnyEvent::Socket> and L<AnyEvent::DNS> for
481	example).
482		695
483	=item $cv->croak ($error)	696	=item $cv->croak ($error)
484		697
485	Similar to send, but causes all call's to C<< ->recv >> to invoke	698	Similar to send, but causes all calls to C<< ->recv >> to invoke
486	C<Carp::croak> with the given error message/object/scalar.	699	C<Carp::croak> with the given error message/object/scalar.
487		700
488	This can be used to signal any errors to the condition variable	701	This can be used to signal any errors to the condition variable
489	user/consumer.	702	user/consumer. Doing it this way instead of calling C<croak> directly
		703	delays the error detection, but has the overwhelming advantage that it
		704	diagnoses the error at the place where the result is expected, and not
		705	deep in some event callback with no connection to the actual code causing
		706	the problem.
490		707
491	=item $cv->begin ([group callback])	708	=item $cv->begin ([group callback])
492		709
493	=item $cv->end	710	=item $cv->end
494
495	These two methods are EXPERIMENTAL and MIGHT CHANGE.
496		711
497	These two methods can be used to combine many transactions/events into	712	These two methods can be used to combine many transactions/events into
498	one. For example, a function that pings many hosts in parallel might want	713	one. For example, a function that pings many hosts in parallel might want
499	to use a condition variable for the whole process.	714	to use a condition variable for the whole process.
500		715
501	Every call to C<< ->begin >> will increment a counter, and every call to	716	Every call to C<< ->begin >> will increment a counter, and every call to
502	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end	717	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
503	>>, the (last) callback passed to C<begin> will be executed. That callback	718	>>, the (last) callback passed to C<begin> will be executed, passing the
504	is I<supposed> to call C<< ->send >>, but that is not required. If no	719	condvar as first argument. That callback is I<supposed> to call C<< ->send
505	callback was set, C<send> will be called without any arguments.	720	>>, but that is not required. If no group callback was set, C<send> will
		721	be called without any arguments.
506		722
507	Let's clarify this with the ping example:	723	You can think of C<< $cv->send >> giving you an OR condition (one call
		724	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		725	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		726
		727	Let's start with a simple example: you have two I/O watchers (for example,
		728	STDOUT and STDERR for a program), and you want to wait for both streams to
		729	close before activating a condvar:
508		730
509	my $cv = AnyEvent->condvar;	731	my $cv = AnyEvent->condvar;
510		732
		733	$cv->begin; # first watcher
		734	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		735	defined sysread $fh1, my $buf, 4096
		736	or $cv->end;
		737	});
		738
		739	$cv->begin; # second watcher
		740	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		741	defined sysread $fh2, my $buf, 4096
		742	or $cv->end;
		743	});
		744
		745	$cv->recv;
		746
		747	This works because for every event source (EOF on file handle), there is
		748	one call to C<begin>, so the condvar waits for all calls to C<end> before
		749	sending.
		750
		751	The ping example mentioned above is slightly more complicated, as the
		752	there are results to be passwd back, and the number of tasks that are
		753	begun can potentially be zero:
		754
		755	my $cv = AnyEvent->condvar;
		756
511	my %result;	757	my %result;
512	$cv->begin (sub { $cv->send (\%result) });	758	$cv->begin (sub { shift->send (\%result) });
513		759
514	for my $host (@list_of_hosts) {	760	for my $host (@list_of_hosts) {
515	$cv->begin;	761	$cv->begin;
516	ping_host_then_call_callback $host, sub {	762	ping_host_then_call_callback $host, sub {
517	$result{$host} = ...;	763	$result{$host} = ...;
…		…
532	loop, which serves two important purposes: first, it sets the callback	778	loop, which serves two important purposes: first, it sets the callback
533	to be called once the counter reaches C<0>, and second, it ensures that	779	to be called once the counter reaches C<0>, and second, it ensures that
534	C<send> is called even when C<no> hosts are being pinged (the loop	780	C<send> is called even when C<no> hosts are being pinged (the loop
535	doesn't execute once).	781	doesn't execute once).
536		782
537	This is the general pattern when you "fan out" into multiple subrequests:	783	This is the general pattern when you "fan out" into multiple (but
538	use an outer C<begin>/C<end> pair to set the callback and ensure C<end>	784	potentially zero) subrequests: use an outer C<begin>/C<end> pair to set
539	is called at least once, and then, for each subrequest you start, call	785	the callback and ensure C<end> is called at least once, and then, for each
540	C<begin> and for each subrequest you finish, call C<end>.	786	subrequest you start, call C<begin> and for each subrequest you finish,
		787	call C<end>.
541		788
542	=back	789	=back
543		790
544	=head3 METHODS FOR CONSUMERS	791	=head3 METHODS FOR CONSUMERS
545		792
…		…
549	=over 4	796	=over 4
550		797
551	=item $cv->recv	798	=item $cv->recv
552		799
553	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak	800	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
554	>> methods have been called on c<$cv>, while servicing other watchers	801	>> methods have been called on C<$cv>, while servicing other watchers
555	normally.	802	normally.
556		803
557	You can only wait once on a condition - additional calls are valid but	804	You can only wait once on a condition - additional calls are valid but
558	will return immediately.	805	will return immediately.
559		806
…		…
561	function will call C<croak>.	808	function will call C<croak>.
562		809
563	In list context, all parameters passed to C<send> will be returned,	810	In list context, all parameters passed to C<send> will be returned,
564	in scalar context only the first one will be returned.	811	in scalar context only the first one will be returned.
565		812
		813	Note that doing a blocking wait in a callback is not supported by any
		814	event loop, that is, recursive invocation of a blocking C<< ->recv
		815	>> is not allowed, and the C<recv> call will C<croak> if such a
		816	condition is detected. This condition can be slightly loosened by using
		817	L<Coro::AnyEvent>, which allows you to do a blocking C<< ->recv >> from
		818	any thread that doesn't run the event loop itself.
		819
566	Not all event models support a blocking wait - some die in that case	820	Not all event models support a blocking wait - some die in that case
567	(programs might want to do that to stay interactive), so I<if you are	821	(programs might want to do that to stay interactive), so I<if you are
568	using this from a module, never require a blocking wait>, but let the	822	using this from a module, never require a blocking wait>. Instead, let the
569	caller decide whether the call will block or not (for example, by coupling	823	caller decide whether the call will block or not (for example, by coupling
570	condition variables with some kind of request results and supporting	824	condition variables with some kind of request results and supporting
571	callbacks so the caller knows that getting the result will not block,	825	callbacks so the caller knows that getting the result will not block,
572	while still supporting blocking waits if the caller so desires).	826	while still supporting blocking waits if the caller so desires).
573		827
574	Another reason I<never> to C<< ->recv >> in a module is that you cannot
575	sensibly have two C<< ->recv >>'s in parallel, as that would require
576	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
577	can supply.
578
579	The L<Coro> module, however, I<can> and I<does> supply coroutines and, in
580	fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe
581	versions and also integrates coroutines into AnyEvent, making blocking
582	C<< ->recv >> calls perfectly safe as long as they are done from another
583	coroutine (one that doesn't run the event loop).
584
585	You can ensure that C<< -recv >> never blocks by setting a callback and	828	You can ensure that C<< ->recv >> never blocks by setting a callback and
586	only calling C<< ->recv >> from within that callback (or at a later	829	only calling C<< ->recv >> from within that callback (or at a later
587	time). This will work even when the event loop does not support blocking	830	time). This will work even when the event loop does not support blocking
588	waits otherwise.	831	waits otherwise.
589		832
590	=item $bool = $cv->ready	833	=item $bool = $cv->ready
591		834
592	Returns true when the condition is "true", i.e. whether C<send> or	835	Returns true when the condition is "true", i.e. whether C<send> or
593	C<croak> have been called.	836	C<croak> have been called.
594		837
595	=item $cb = $cv->cb ([new callback])	838	=item $cb = $cv->cb ($cb->($cv))
596		839
597	This is a mutator function that returns the callback set and optionally	840	This is a mutator function that returns the callback set and optionally
598	replaces it before doing so.	841	replaces it before doing so.
599		842
600	The callback will be called when the condition becomes "true", i.e. when	843	The callback will be called when the condition becomes "true", i.e. when
601	C<send> or C<croak> are called, with the only argument being the condition	844	C<send> or C<croak> are called, with the only argument being the
602	variable itself. Calling C<recv> inside the callback or at any later time	845	condition variable itself. If the condition is already true, the
603	is guaranteed not to block.	846	callback is called immediately when it is set. Calling C<recv> inside
		847	the callback or at any later time is guaranteed not to block.
604		848
605	=back	849	=back
606		850
		851	=head1 SUPPORTED EVENT LOOPS/BACKENDS
		852
		853	The available backend classes are (every class has its own manpage):
		854
		855	=over 4
		856
		857	=item Backends that are autoprobed when no other event loop can be found.
		858
		859	EV is the preferred backend when no other event loop seems to be in
		860	use. If EV is not installed, then AnyEvent will fall back to its own
		861	pure-perl implementation, which is available everywhere as it comes with
		862	AnyEvent itself.
		863
		864	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		865	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
		866
		867	=item Backends that are transparently being picked up when they are used.
		868
		869	These will be used if they are already loaded when the first watcher
		870	is created, in which case it is assumed that the application is using
		871	them. This means that AnyEvent will automatically pick the right backend
		872	when the main program loads an event module before anything starts to
		873	create watchers. Nothing special needs to be done by the main program.
		874
		875	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		876	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		877	AnyEvent::Impl::Tk based on Tk, very broken.
		878	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		879	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		880	AnyEvent::Impl::Irssi used when running within irssi.
		881
		882	=item Backends with special needs.
		883
		884	Qt requires the Qt::Application to be instantiated first, but will
		885	otherwise be picked up automatically. As long as the main program
		886	instantiates the application before any AnyEvent watchers are created,
		887	everything should just work.
		888
		889	AnyEvent::Impl::Qt based on Qt.
		890
		891	Support for IO::Async can only be partial, as it is too broken and
		892	architecturally limited to even support the AnyEvent API. It also
		893	is the only event loop that needs the loop to be set explicitly, so
		894	it can only be used by a main program knowing about AnyEvent. See
		895	L<AnyEvent::Impl::IOAsync> for the gory details.
		896
		897	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
		898
		899	=item Event loops that are indirectly supported via other backends.
		900
		901	Some event loops can be supported via other modules:
		902
		903	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		904
		905	B<WxWidgets> has no support for watching file handles. However, you can
		906	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		907	polls 20 times per second, which was considered to be too horrible to even
		908	consider for AnyEvent.
		909
		910	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		911	backend, so it can be supported through POE.
		912
		913	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		914	load L<POE> when detecting them, in the hope that POE will pick them up,
		915	in which case everything will be automatic.
		916
		917	=back
		918
607	=head1 GLOBAL VARIABLES AND FUNCTIONS	919	=head1 GLOBAL VARIABLES AND FUNCTIONS
608		920
		921	These are not normally required to use AnyEvent, but can be useful to
		922	write AnyEvent extension modules.
		923
609	=over 4	924	=over 4
610		925
611	=item $AnyEvent::MODEL	926	=item $AnyEvent::MODEL
612		927
613	Contains C<undef> until the first watcher is being created. Then it	928	Contains C<undef> until the first watcher is being created, before the
		929	backend has been autodetected.
		930
614	contains the event model that is being used, which is the name of the	931	Afterwards it contains the event model that is being used, which is the
615	Perl class implementing the model. This class is usually one of the	932	name of the Perl class implementing the model. This class is usually one
616	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	933	of the C<AnyEvent::Impl::xxx> modules, but can be any other class in the
617	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	934	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
618		935	will be C<urxvt::anyevent>).
619	The known classes so far are:
620
621	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
622	AnyEvent::Impl::Event based on Event, second best choice.
623	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
624	AnyEvent::Impl::Glib based on Glib, third-best choice.
625	AnyEvent::Impl::Tk based on Tk, very bad choice.
626	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
627	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
628	AnyEvent::Impl::POE based on POE, not generic enough for full support.
629
630	There is no support for WxWidgets, as WxWidgets has no support for
631	watching file handles. However, you can use WxWidgets through the
632	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
633	second, which was considered to be too horrible to even consider for
634	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
635	it's adaptor.
636
637	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
638	autodetecting them.
639		936
640	=item AnyEvent::detect	937	=item AnyEvent::detect
641		938
642	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	939	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
643	if necessary. You should only call this function right before you would	940	if necessary. You should only call this function right before you would
644	have created an AnyEvent watcher anyway, that is, as late as possible at	941	have created an AnyEvent watcher anyway, that is, as late as possible at
645	runtime.	942	runtime, and not e.g. during initialisation of your module.
		943
		944	If you need to do some initialisation before AnyEvent watchers are
		945	created, use C<post_detect>.
646		946
647	=item $guard = AnyEvent::post_detect { BLOCK }	947	=item $guard = AnyEvent::post_detect { BLOCK }
648		948
649	Arranges for the code block to be executed as soon as the event model is	949	Arranges for the code block to be executed as soon as the event model is
650	autodetected (or immediately if this has already happened).	950	autodetected (or immediately if that has already happened).
		951
		952	The block will be executed I<after> the actual backend has been detected
		953	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		954	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		955	other initialisations - see the sources of L<AnyEvent::Strict> or
		956	L<AnyEvent::AIO> to see how this is used.
		957
		958	The most common usage is to create some global watchers, without forcing
		959	event module detection too early, for example, L<AnyEvent::AIO> creates
		960	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		961	avoid autodetecting the event module at load time.
651		962
652	If called in scalar or list context, then it creates and returns an object	963	If called in scalar or list context, then it creates and returns an object
653	that automatically removes the callback again when it is destroyed. See	964	that automatically removes the callback again when it is destroyed (or
		965	C<undef> when the hook was immediately executed). See L<AnyEvent::AIO> for
654	L<Coro::BDB> for a case where this is useful.	966	a case where this is useful.
		967
		968	Example: Create a watcher for the IO::AIO module and store it in
		969	C<$WATCHER>, but do so only do so after the event loop is initialised.
		970
		971	our WATCHER;
		972
		973	my $guard = AnyEvent::post_detect {
		974	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		975	};
		976
		977	# the ||= is important in case post_detect immediately runs the block,
		978	# as to not clobber the newly-created watcher. assigning both watcher and
		979	# post_detect guard to the same variable has the advantage of users being
		980	# able to just C<undef $WATCHER> if the watcher causes them grief.
		981
		982	$WATCHER ||= $guard;
655		983
656	=item @AnyEvent::post_detect	984	=item @AnyEvent::post_detect
657		985
658	If there are any code references in this array (you can C<push> to it	986	If there are any code references in this array (you can C<push> to it
659	before or after loading AnyEvent), then they will called directly after	987	before or after loading AnyEvent), then they will be called directly
660	the event loop has been chosen.	988	after the event loop has been chosen.
661		989
662	You should check C<$AnyEvent::MODEL> before adding to this array, though:	990	You should check C<$AnyEvent::MODEL> before adding to this array, though:
663	if it contains a true value then the event loop has already been detected,	991	if it is defined then the event loop has already been detected, and the
664	and the array will be ignored.	992	array will be ignored.
665		993
666	Best use C<AnyEvent::post_detect { BLOCK }> instead.	994	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		995	it, as it takes care of these details.
		996
		997	This variable is mainly useful for modules that can do something useful
		998	when AnyEvent is used and thus want to know when it is initialised, but do
		999	not need to even load it by default. This array provides the means to hook
		1000	into AnyEvent passively, without loading it.
		1001
		1002	Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used
		1003	together, you could put this into Coro (this is the actual code used by
		1004	Coro to accomplish this):
		1005
		1006	if (defined $AnyEvent::MODEL) {
		1007	# AnyEvent already initialised, so load Coro::AnyEvent
		1008	require Coro::AnyEvent;
		1009	} else {
		1010	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent
		1011	# as soon as it is
		1012	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };
		1013	}
667		1014
668	=back	1015	=back
669		1016
670	=head1 WHAT TO DO IN A MODULE	1017	=head1 WHAT TO DO IN A MODULE
671		1018
…		…
682	because it will stall the whole program, and the whole point of using	1029	because it will stall the whole program, and the whole point of using
683	events is to stay interactive.	1030	events is to stay interactive.
684		1031
685	It is fine, however, to call C<< ->recv >> when the user of your module	1032	It is fine, however, to call C<< ->recv >> when the user of your module
686	requests it (i.e. if you create a http request object ad have a method	1033	requests it (i.e. if you create a http request object ad have a method
687	called C<results> that returns the results, it should call C<< ->recv >>	1034	called C<results> that returns the results, it may call C<< ->recv >>
688	freely, as the user of your module knows what she is doing. always).	1035	freely, as the user of your module knows what she is doing. Always).
689		1036
690	=head1 WHAT TO DO IN THE MAIN PROGRAM	1037	=head1 WHAT TO DO IN THE MAIN PROGRAM
691		1038
692	There will always be a single main program - the only place that should	1039	There will always be a single main program - the only place that should
693	dictate which event model to use.	1040	dictate which event model to use.
694		1041
695	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	1042	If the program is not event-based, it need not do anything special, even
696	do anything special (it does not need to be event-based) and let AnyEvent	1043	when it depends on a module that uses an AnyEvent. If the program itself
697	decide which implementation to chose if some module relies on it.	1044	uses AnyEvent, but does not care which event loop is used, all it needs
		1045	to do is C<use AnyEvent>. In either case, AnyEvent will choose the best
		1046	available loop implementation.
698		1047
699	If the main program relies on a specific event model - for example, in	1048	If the main program relies on a specific event model - for example, in
700	Gtk2 programs you have to rely on the Glib module - you should load the	1049	Gtk2 programs you have to rely on the Glib module - you should load the
701	event module before loading AnyEvent or any module that uses it: generally	1050	event module before loading AnyEvent or any module that uses it: generally
702	speaking, you should load it as early as possible. The reason is that	1051	speaking, you should load it as early as possible. The reason is that
703	modules might create watchers when they are loaded, and AnyEvent will	1052	modules might create watchers when they are loaded, and AnyEvent will
704	decide on the event model to use as soon as it creates watchers, and it	1053	decide on the event model to use as soon as it creates watchers, and it
705	might chose the wrong one unless you load the correct one yourself.	1054	might choose the wrong one unless you load the correct one yourself.
706		1055
707	You can chose to use a pure-perl implementation by loading the	1056	You can chose to use a pure-perl implementation by loading the
708	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour	1057	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
709	everywhere, but letting AnyEvent chose the model is generally better.	1058	everywhere, but letting AnyEvent chose the model is generally better.
710		1059
…		…
726		1075
727		1076
728	=head1 OTHER MODULES	1077	=head1 OTHER MODULES
729		1078
730	The following is a non-exhaustive list of additional modules that use	1079	The following is a non-exhaustive list of additional modules that use
731	AnyEvent and can therefore be mixed easily with other AnyEvent modules	1080	AnyEvent as a client and can therefore be mixed easily with other AnyEvent
732	in the same program. Some of the modules come with AnyEvent, some are	1081	modules and other event loops in the same program. Some of the modules
733	available via CPAN.	1082	come as part of AnyEvent, the others are available via CPAN.
734		1083
735	=over 4	1084	=over 4
736		1085
737	=item L<AnyEvent::Util>	1086	=item L<AnyEvent::Util>
738		1087
739	Contains various utility functions that replace often-used but blocking	1088	Contains various utility functions that replace often-used blocking
740	functions such as C<inet_aton> by event-/callback-based versions.	1089	functions such as C<inet_aton> with event/callback-based versions.
741		1090
742	=item L<AnyEvent::Socket>	1091	=item L<AnyEvent::Socket>
743		1092
744	Provides various utility functions for (internet protocol) sockets,	1093	Provides various utility functions for (internet protocol) sockets,
745	addresses and name resolution. Also functions to create non-blocking tcp	1094	addresses and name resolution. Also functions to create non-blocking tcp
…		…
747		1096
748	=item L<AnyEvent::Handle>	1097	=item L<AnyEvent::Handle>
749		1098
750	Provide read and write buffers, manages watchers for reads and writes,	1099	Provide read and write buffers, manages watchers for reads and writes,
751	supports raw and formatted I/O, I/O queued and fully transparent and	1100	supports raw and formatted I/O, I/O queued and fully transparent and
752	non-blocking SSL/TLS.	1101	non-blocking SSL/TLS (via L<AnyEvent::TLS>).
753		1102
754	=item L<AnyEvent::DNS>	1103	=item L<AnyEvent::DNS>
755		1104
756	Provides rich asynchronous DNS resolver capabilities.	1105	Provides rich asynchronous DNS resolver capabilities.
757		1106
		1107	=item L<AnyEvent::HTTP>, L<AnyEvent::IRC>, L<AnyEvent::XMPP>, L<AnyEvent::GPSD>, L<AnyEvent::IGS>, L<AnyEvent::FCP>
		1108
		1109	Implement event-based interfaces to the protocols of the same name (for
		1110	the curious, IGS is the International Go Server and FCP is the Freenet
		1111	Client Protocol).
		1112
		1113	=item L<AnyEvent::Handle::UDP>
		1114
		1115	Here be danger!
		1116
		1117	As Pauli would put it, "Not only is it not right, it's not even wrong!" -
		1118	there are so many things wrong with AnyEvent::Handle::UDP, most notably
		1119	its use of a stream-based API with a protocol that isn't streamable, that
		1120	the only way to improve it is to delete it.
		1121
		1122	It features data corruption (but typically only under load) and general
		1123	confusion. On top, the author is not only clueless about UDP but also
		1124	fact-resistant - some gems of his understanding: "connect doesn't work
		1125	with UDP", "UDP packets are not IP packets", "UDP only has datagrams, not
		1126	packets", "I don't need to implement proper error checking as UDP doesn't
		1127	support error checking" and so on - he doesn't even understand what's
		1128	wrong with his module when it is explained to him.
		1129
758	=item L<AnyEvent::HTTP>	1130	=item L<AnyEvent::DBI>
759		1131
760	A simple-to-use HTTP library that is capable of making a lot of concurrent	1132	Executes L<DBI> requests asynchronously in a proxy process for you,
761	HTTP requests.	1133	notifying you in an event-based way when the operation is finished.
		1134
		1135	=item L<AnyEvent::AIO>
		1136
		1137	Truly asynchronous (as opposed to non-blocking) I/O, should be in the
		1138	toolbox of every event programmer. AnyEvent::AIO transparently fuses
		1139	L<IO::AIO> and AnyEvent together, giving AnyEvent access to event-based
		1140	file I/O, and much more.
762		1141
763	=item L<AnyEvent::HTTPD>	1142	=item L<AnyEvent::HTTPD>
764		1143
765	Provides a simple web application server framework.	1144	A simple embedded webserver.
766		1145
767	=item L<AnyEvent::FastPing>	1146	=item L<AnyEvent::FastPing>
768		1147
769	The fastest ping in the west.	1148	The fastest ping in the west.
770		1149
771	=item L<AnyEvent::DBI>
772
773	Executes L<DBI> requests asynchronously in a proxy process.
774
775	=item L<AnyEvent::AIO>
776
777	Truly asynchronous I/O, should be in the toolbox of every event
778	programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
779	together.
780
781	=item L<AnyEvent::BDB>
782
783	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
784	L<BDB> and AnyEvent together.
785
786	=item L<AnyEvent::GPSD>
787
788	A non-blocking interface to gpsd, a daemon delivering GPS information.
789
790	=item L<AnyEvent::IGS>
791
792	A non-blocking interface to the Internet Go Server protocol (used by
793	L<App::IGS>).
794
795	=item L<Net::IRC3>
796
797	AnyEvent based IRC client module family.
798
799	=item L<Net::XMPP2>
800
801	AnyEvent based XMPP (Jabber protocol) module family.
802
803	=item L<Net::FCP>
804
805	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
806	of AnyEvent.
807
808	=item L<Event::ExecFlow>
809
810	High level API for event-based execution flow control.
811
812	=item L<Coro>	1150	=item L<Coro>
813		1151
814	Has special support for AnyEvent via L<Coro::AnyEvent>.	1152	Has special support for AnyEvent via L<Coro::AnyEvent>.
815		1153
816	=item L<IO::Lambda>
817
818	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
819
820	=back	1154	=back
821		1155
822	=cut	1156	=cut
823		1157
824	package AnyEvent;	1158	package AnyEvent;
825		1159
826	no warnings;	1160	# basically a tuned-down version of common::sense
827	use strict;	1161	sub common_sense {
		1162	# from common:.sense 1.0
		1163	${^WARNING_BITS} = "\xfc\x3f\x33\x00\x0f\xf3\xcf\xc0\xf3\xfc\x33\x00";
		1164	# use strict vars subs - NO UTF-8, as Util.pm doesn't like this atm. (uts46data.pl)
		1165	$^H |= 0x00000600;
		1166	}
828		1167
		1168	BEGIN { AnyEvent::common_sense }
		1169
829	use Carp;	1170	use Carp ();
830		1171
831	our $VERSION = 4.22;	1172	our $VERSION = '5.271';
832	our $MODEL;	1173	our $MODEL;
833		1174
834	our $AUTOLOAD;	1175	our $AUTOLOAD;
835	our @ISA;	1176	our @ISA;
836		1177
837	our @REGISTRY;	1178	our @REGISTRY;
838		1179
839	our $WIN32;	1180	our $VERBOSE;
840		1181
841	BEGIN {	1182	BEGIN {
842	my $win32 = ! ! ($^O =~ /mswin32/i);	1183	require "AnyEvent/constants.pl";
843	eval "sub WIN32(){ $win32 }";
844	}
845		1184
		1185	eval "sub TAINT (){" . (${^TAINT}*1) . "}";
		1186
		1187	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1188	if ${^TAINT};
		1189
846	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;	1190	$VERBOSE = $ENV{PERL_ANYEVENT_VERBOSE}*1;
		1191
		1192	}
		1193
		1194	our $MAX_SIGNAL_LATENCY = 10;
847		1195
848	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred	1196	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
849		1197
850	{	1198	{
851	my $idx;	1199	my $idx;
…		…
853	for reverse split /\s*,\s*/,	1201	for reverse split /\s*,\s*/,
854	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";	1202	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
855	}	1203	}
856		1204
857	my @models = (	1205	my @models = (
858	[EV:: => AnyEvent::Impl::EV::],	1206	[EV:: => AnyEvent::Impl::EV:: , 1],
859	[Event:: => AnyEvent::Impl::Event::],
860	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1207	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl:: , 1],
861	# everything below here will not be autoprobed	1208	# everything below here will not (normally) be autoprobed
862	# as the pureperl backend should work everywhere	1209	# as the pureperl backend should work everywhere
863	# and is usually faster	1210	# and is usually faster
		1211	[Event:: => AnyEvent::Impl::Event::, 1],
		1212	[Glib:: => AnyEvent::Impl::Glib:: , 1], # becomes extremely slow with many watchers
		1213	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		1214	[Irssi:: => AnyEvent::Impl::Irssi::], # Irssi has a bogus "Event" package
864	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles	1215	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
865	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers
866	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
867	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program	1216	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
868	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza	1217	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
869	[Wx:: => AnyEvent::Impl::POE::],	1218	[Wx:: => AnyEvent::Impl::POE::],
870	[Prima:: => AnyEvent::Impl::POE::],	1219	[Prima:: => AnyEvent::Impl::POE::],
		1220	# IO::Async is just too broken - we would need workarounds for its
		1221	# byzantine signal and broken child handling, among others.
		1222	# IO::Async is rather hard to detect, as it doesn't have any
		1223	# obvious default class.
		1224	[IO::Async:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1225	[IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1226	[IO::Async::Notifier:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1227	[AnyEvent::Impl::IOAsync:: => AnyEvent::Impl::IOAsync::], # requires special main program
871	);	1228	);
872		1229
873	our %method = map +($_ => 1), qw(io timer time now signal child condvar one_event DESTROY);	1230	our %method = map +($_ => 1),
		1231	qw(io timer time now now_update signal child idle condvar one_event DESTROY);
874		1232
875	our @post_detect;	1233	our @post_detect;
876		1234
877	sub post_detect(&) {	1235	sub post_detect(&) {
878	my ($cb) = @_;	1236	my ($cb) = @_;
879		1237
880	if ($MODEL) {
881	$cb->();
882
883	1
884	} else {
885	push @post_detect, $cb;	1238	push @post_detect, $cb;
886		1239
887	defined wantarray	1240	defined wantarray
888	? bless \$cb, "AnyEvent::Util::PostDetect"	1241	? bless \$cb, "AnyEvent::Util::postdetect"
889	: ()	1242	: ()
		1243	}
		1244
		1245	sub AnyEvent::Util::postdetect::DESTROY {
		1246	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		1247	}
		1248
		1249	sub detect() {
		1250	# free some memory
		1251	*detect = sub () { $MODEL };
		1252
		1253	local $!; # for good measure
		1254	local $SIG{__DIE__};
		1255
		1256	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
		1257	my $model = "AnyEvent::Impl::$1";
		1258	if (eval "require $model") {
		1259	$MODEL = $model;
		1260	warn "AnyEvent: loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.\n" if $VERBOSE >= 2;
		1261	} else {
		1262	warn "AnyEvent: unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@" if $VERBOSE;
		1263	}
890	}	1264	}
891	}
892		1265
893	sub AnyEvent::Util::PostDetect::DESTROY {	1266	# check for already loaded models
894	@post_detect = grep $_ != ${$_[0]}, @post_detect;
895	}
896
897	sub detect() {
898	unless ($MODEL) {	1267	unless ($MODEL) {
899	no strict 'refs';	1268	for (@REGISTRY, @models) {
900	local $SIG{__DIE__};	1269	my ($package, $model) = @$_;
901		1270	if (${"$package\::VERSION"} > 0) {
902	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
903	my $model = "AnyEvent::Impl::$1";
904	if (eval "require $model") {	1271	if (eval "require $model") {
905	$MODEL = $model;	1272	$MODEL = $model;
906	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	1273	warn "AnyEvent: autodetected model '$model', using it.\n" if $VERBOSE >= 2;
907	} else {	1274	last;
908	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;	1275	}
909	}	1276	}
910	}	1277	}
911		1278
912	# check for already loaded models
913	unless ($MODEL) {	1279	unless ($MODEL) {
		1280	# try to autoload a model
914	for (@REGISTRY, @models) {	1281	for (@REGISTRY, @models) {
915	my ($package, $model) = @$_;	1282	my ($package, $model, $autoload) = @$_;
		1283	if (
		1284	$autoload
		1285	and eval "require $package"
916	if (${"$package\::VERSION"} > 0) {	1286	and ${"$package\::VERSION"} > 0
917	if (eval "require $model") {	1287	and eval "require $model"
		1288	) {
918	$MODEL = $model;	1289	$MODEL = $model;
919	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;	1290	warn "AnyEvent: autoloaded model '$model', using it.\n" if $VERBOSE >= 2;
920	last;	1291	last;
921	}
922	}	1292	}
923	}	1293	}
924		1294
925	unless ($MODEL) {
926	# try to load a model
927
928	for (@REGISTRY, @models) {
929	my ($package, $model) = @$_;
930	if (eval "require $package"
931	and ${"$package\::VERSION"} > 0
932	and eval "require $model") {
933	$MODEL = $model;
934	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;
935	last;
936	}
937	}
938
939	$MODEL	1295	$MODEL
940	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.";	1296	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.\n";
941	}
942	}	1297	}
943
944	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
945
946	unshift @ISA, $MODEL;
947
948	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
949
950	(shift @post_detect)->() while @post_detect;
951	}	1298	}
		1299
		1300	@models = (); # free probe data
		1301
		1302	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		1303	unshift @ISA, $MODEL;
		1304
		1305	# now nuke some methods that are overriden by the backend.
		1306	# SUPER is not allowed.
		1307	for (qw(time signal child idle)) {
		1308	undef &{"AnyEvent::Base::$_"}
		1309	if defined &{"$MODEL\::$_"};
		1310	}
		1311
		1312	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
		1313
		1314	(shift @post_detect)->() while @post_detect;
		1315
		1316	*post_detect = sub(&) {
		1317	shift->();
		1318
		1319	undef
		1320	};
952		1321
953	$MODEL	1322	$MODEL
954	}	1323	}
955		1324
956	sub AUTOLOAD {	1325	sub AUTOLOAD {
957	(my $func = $AUTOLOAD) =~ s/.*://;	1326	(my $func = $AUTOLOAD) =~ s/.*://;
958		1327
959	$method{$func}	1328	$method{$func}
960	or croak "$func: not a valid method for AnyEvent objects";	1329	or Carp::croak "$func: not a valid AnyEvent class method";
961		1330
962	detect unless $MODEL;	1331	detect;
963		1332
964	my $class = shift;	1333	my $class = shift;
965	$class->$func (@_);	1334	$class->$func (@_);
966	}	1335	}
967		1336
968	# utility function to dup a filehandle. this is used by many backends	1337	# utility function to dup a filehandle. this is used by many backends
969	# to support binding more than one watcher per filehandle (they usually	1338	# to support binding more than one watcher per filehandle (they usually
970	# allow only one watcher per fd, so we dup it to get a different one).	1339	# allow only one watcher per fd, so we dup it to get a different one).
971	sub _dupfh($$$$) {	1340	sub _dupfh($$;$$) {
972	my ($poll, $fh, $r, $w) = @_;	1341	my ($poll, $fh, $r, $w) = @_;
973		1342
974	require Fcntl;
975
976	# cygwin requires the fh mode to be matching, unix doesn't	1343	# cygwin requires the fh mode to be matching, unix doesn't
977	my ($rw, $mode) = $poll eq "r" ? ($r, "<")	1344	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
978	: $poll eq "w" ? ($w, ">")
979	: Carp::croak "AnyEvent->io requires poll set to either 'r' or 'w'";
980		1345
981	open my $fh2, "$mode&" . fileno $fh	1346	open my $fh2, $mode, $fh
982	or die "cannot dup() filehandle: $!";	1347	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
983		1348
984	# we assume CLOEXEC is already set by perl in all important cases	1349	# we assume CLOEXEC is already set by perl in all important cases
985		1350
986	($fh2, $rw)	1351	($fh2, $rw)
987	}	1352	}
988		1353
		1354	=head1 SIMPLIFIED AE API
		1355
		1356	Starting with version 5.0, AnyEvent officially supports a second, much
		1357	simpler, API that is designed to reduce the calling, typing and memory
		1358	overhead by using function call syntax and a fixed number of parameters.
		1359
		1360	See the L<AE> manpage for details.
		1361
		1362	=cut
		1363
		1364	package AE;
		1365
		1366	our $VERSION = $AnyEvent::VERSION;
		1367
		1368	# fall back to the main API by default - backends and AnyEvent::Base
		1369	# implementations can overwrite these.
		1370
		1371	sub io($$$) {
		1372	AnyEvent->io (fh => $_[0], poll => $_[1] ? "w" : "r", cb => $_[2])
		1373	}
		1374
		1375	sub timer($$$) {
		1376	AnyEvent->timer (after => $_[0], interval => $_[1], cb => $_[2])
		1377	}
		1378
		1379	sub signal($$) {
		1380	AnyEvent->signal (signal => $_[0], cb => $_[1])
		1381	}
		1382
		1383	sub child($$) {
		1384	AnyEvent->child (pid => $_[0], cb => $_[1])
		1385	}
		1386
		1387	sub idle($) {
		1388	AnyEvent->idle (cb => $_[0])
		1389	}
		1390
		1391	sub cv(;&) {
		1392	AnyEvent->condvar (@_ ? (cb => $_[0]) : ())
		1393	}
		1394
		1395	sub now() {
		1396	AnyEvent->now
		1397	}
		1398
		1399	sub now_update() {
		1400	AnyEvent->now_update
		1401	}
		1402
		1403	sub time() {
		1404	AnyEvent->time
		1405	}
		1406
989	package AnyEvent::Base;	1407	package AnyEvent::Base;
990		1408
991	# default implementation for now and time	1409	# default implementations for many methods
992		1410
993	use Time::HiRes ();	1411	sub time {
		1412	eval q{ # poor man's autoloading {}
		1413	# probe for availability of Time::HiRes
		1414	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1415	warn "AnyEvent: using Time::HiRes for sub-second timing accuracy.\n" if $VERBOSE >= 8;
		1416	*AE::time = \&Time::HiRes::time;
		1417	# if (eval "use POSIX (); (POSIX::times())...
		1418	} else {
		1419	warn "AnyEvent: using built-in time(), WARNING, no sub-second resolution!\n" if $VERBOSE;
		1420	*AE::time = sub (){ time }; # epic fail
		1421	}
994		1422
995	sub time { Time::HiRes::time }	1423	*time = sub { AE::time }; # different prototypes
996	sub now { Time::HiRes::time }	1424	};
		1425	die if $@;
		1426
		1427	&time
		1428	}
		1429
		1430	*now = \&time;
		1431
		1432	sub now_update { }
997		1433
998	# default implementation for ->condvar	1434	# default implementation for ->condvar
999		1435
1000	sub condvar {	1436	sub condvar {
		1437	eval q{ # poor man's autoloading {}
		1438	*condvar = sub {
1001	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, AnyEvent::CondVar::	1439	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
		1440	};
		1441
		1442	*AE::cv = sub (;&) {
		1443	bless { @_ ? (_ae_cb => shift) : () }, "AnyEvent::CondVar"
		1444	};
		1445	};
		1446	die if $@;
		1447
		1448	&condvar
1002	}	1449	}
1003		1450
1004	# default implementation for ->signal	1451	# default implementation for ->signal
1005		1452
1006	our %SIG_CB;	1453	our $HAVE_ASYNC_INTERRUPT;
		1454
		1455	sub _have_async_interrupt() {
		1456	$HAVE_ASYNC_INTERRUPT = 1*(!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT}
		1457	&& eval "use Async::Interrupt 1.02 (); 1")
		1458	unless defined $HAVE_ASYNC_INTERRUPT;
		1459
		1460	$HAVE_ASYNC_INTERRUPT
		1461	}
		1462
		1463	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1464	our (%SIG_ASY, %SIG_ASY_W);
		1465	our ($SIG_COUNT, $SIG_TW);
		1466
		1467	# install a dummy wakeup watcher to reduce signal catching latency
		1468	# used by Impls
		1469	sub _sig_add() {
		1470	unless ($SIG_COUNT++) {
		1471	# try to align timer on a full-second boundary, if possible
		1472	my $NOW = AE::now;
		1473
		1474	$SIG_TW = AE::timer
		1475	$MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1476	$MAX_SIGNAL_LATENCY,
		1477	sub { } # just for the PERL_ASYNC_CHECK
		1478	;
		1479	}
		1480	}
		1481
		1482	sub _sig_del {
		1483	undef $SIG_TW
		1484	unless --$SIG_COUNT;
		1485	}
		1486
		1487	our $_sig_name_init; $_sig_name_init = sub {
		1488	eval q{ # poor man's autoloading {}
		1489	undef $_sig_name_init;
		1490
		1491	if (_have_async_interrupt) {
		1492	*sig2num = \&Async::Interrupt::sig2num;
		1493	*sig2name = \&Async::Interrupt::sig2name;
		1494	} else {
		1495	require Config;
		1496
		1497	my %signame2num;
		1498	@signame2num{ split ' ', $Config::Config{sig_name} }
		1499	= split ' ', $Config::Config{sig_num};
		1500
		1501	my @signum2name;
		1502	@signum2name[values %signame2num] = keys %signame2num;
		1503
		1504	*sig2num = sub($) {
		1505	$_[0] > 0 ? shift : $signame2num{+shift}
		1506	};
		1507	*sig2name = sub ($) {
		1508	$_[0] > 0 ? $signum2name[+shift] : shift
		1509	};
		1510	}
		1511	};
		1512	die if $@;
		1513	};
		1514
		1515	sub sig2num ($) { &$_sig_name_init; &sig2num }
		1516	sub sig2name($) { &$_sig_name_init; &sig2name }
1007		1517
1008	sub signal {	1518	sub signal {
		1519	eval q{ # poor man's autoloading {}
		1520	# probe for availability of Async::Interrupt
		1521	if (_have_async_interrupt) {
		1522	warn "AnyEvent: using Async::Interrupt for race-free signal handling.\n" if $VERBOSE >= 8;
		1523
		1524	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1525	$SIG_IO = AE::io $SIGPIPE_R->fileno, 0, \&_signal_exec;
		1526
		1527	} else {
		1528	warn "AnyEvent: using emulated perl signal handling with latency timer.\n" if $VERBOSE >= 8;
		1529
		1530	if (AnyEvent::WIN32) {
		1531	require AnyEvent::Util;
		1532
		1533	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1534	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R, 1) if $SIGPIPE_R;
		1535	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W, 1) if $SIGPIPE_W; # just in case
		1536	} else {
		1537	pipe $SIGPIPE_R, $SIGPIPE_W;
		1538	fcntl $SIGPIPE_R, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_R;
		1539	fcntl $SIGPIPE_W, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_W; # just in case
		1540
		1541	# not strictly required, as $^F is normally 2, but let's make sure...
		1542	fcntl $SIGPIPE_R, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1543	fcntl $SIGPIPE_W, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1544	}
		1545
		1546	$SIGPIPE_R
		1547	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1548
		1549	$SIG_IO = AE::io $SIGPIPE_R, 0, \&_signal_exec;
		1550	}
		1551
		1552	*signal = $HAVE_ASYNC_INTERRUPT
		1553	? sub {
1009	my (undef, %arg) = @_;	1554	my (undef, %arg) = @_;
1010		1555
		1556	# async::interrupt
1011	my $signal = uc $arg{signal}	1557	my $signal = sig2num $arg{signal};
1012	or Carp::croak "required option 'signal' is missing";
1013
1014	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1558	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1559
		1560	$SIG_ASY{$signal} ||= new Async::Interrupt
		1561	cb => sub { undef $SIG_EV{$signal} },
		1562	signal => $signal,
		1563	pipe => [$SIGPIPE_R->filenos],
		1564	pipe_autodrain => 0,
		1565	;
		1566
		1567	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1568	}
		1569	: sub {
		1570	my (undef, %arg) = @_;
		1571
		1572	# pure perl
		1573	my $signal = sig2name $arg{signal};
		1574	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1575
1015	$SIG{$signal} ||= sub {	1576	$SIG{$signal} ||= sub {
		1577	local $!;
		1578	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1579	undef $SIG_EV{$signal};
		1580	};
		1581
		1582	# can't do signal processing without introducing races in pure perl,
		1583	# so limit the signal latency.
		1584	_sig_add;
		1585
		1586	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1587	}
		1588	;
		1589
		1590	*AnyEvent::Base::signal::DESTROY = sub {
		1591	my ($signal, $cb) = @{$_[0]};
		1592
		1593	_sig_del;
		1594
		1595	delete $SIG_CB{$signal}{$cb};
		1596
		1597	$HAVE_ASYNC_INTERRUPT
		1598	? delete $SIG_ASY{$signal}
		1599	: # delete doesn't work with older perls - they then
		1600	# print weird messages, or just unconditionally exit
		1601	# instead of getting the default action.
		1602	undef $SIG{$signal}
		1603	unless keys %{ $SIG_CB{$signal} };
		1604	};
		1605
		1606	*_signal_exec = sub {
		1607	$HAVE_ASYNC_INTERRUPT
		1608	? $SIGPIPE_R->drain
		1609	: sysread $SIGPIPE_R, (my $dummy), 9;
		1610
		1611	while (%SIG_EV) {
		1612	for (keys %SIG_EV) {
		1613	delete $SIG_EV{$_};
1016	$_->() for values %{ $SIG_CB{$signal} || {} };	1614	$_->() for values %{ $SIG_CB{$_} || {} };
		1615	}
		1616	}
		1617	};
1017	};	1618	};
		1619	die if $@;
1018		1620
1019	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1621	&signal
1020	}
1021
1022	sub AnyEvent::Base::Signal::DESTROY {
1023	my ($signal, $cb) = @{$_[0]};
1024
1025	delete $SIG_CB{$signal}{$cb};
1026
1027	delete $SIG{$signal} unless keys %{ $SIG_CB{$signal} };
1028	}	1622	}
1029		1623
1030	# default implementation for ->child	1624	# default implementation for ->child
1031		1625
1032	our %PID_CB;	1626	our %PID_CB;
1033	our $CHLD_W;	1627	our $CHLD_W;
1034	our $CHLD_DELAY_W;	1628	our $CHLD_DELAY_W;
1035	our $PID_IDLE;
1036	our $WNOHANG;	1629	our $WNOHANG;
1037		1630
1038	sub _child_wait {	1631	# used by many Impl's
1039	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1632	sub _emit_childstatus($$) {
		1633	my (undef, $rpid, $rstatus) = @_;
		1634
		1635	$_->($rpid, $rstatus)
1040	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1636	for values %{ $PID_CB{$rpid} || {} },
1041	(values %{ $PID_CB{0} || {} });	1637	values %{ $PID_CB{0} || {} };
1042	}
1043
1044	undef $PID_IDLE;
1045	}
1046
1047	sub _sigchld {
1048	# make sure we deliver these changes "synchronous" with the event loop.
1049	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {
1050	undef $CHLD_DELAY_W;
1051	&_child_wait;
1052	});
1053	}	1638	}
1054		1639
1055	sub child {	1640	sub child {
		1641	eval q{ # poor man's autoloading {}
		1642	*_sigchld = sub {
		1643	my $pid;
		1644
		1645	AnyEvent->_emit_childstatus ($pid, $?)
		1646	while ($pid = waitpid -1, $WNOHANG) > 0;
		1647	};
		1648
		1649	*child = sub {
1056	my (undef, %arg) = @_;	1650	my (undef, %arg) = @_;
1057		1651
1058	defined (my $pid = $arg{pid} + 0)	1652	defined (my $pid = $arg{pid} + 0)
1059	or Carp::croak "required option 'pid' is missing";	1653	or Carp::croak "required option 'pid' is missing";
1060		1654
1061	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1655	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
1062		1656
1063	unless ($WNOHANG) {	1657	# WNOHANG is almost cetrainly 1 everywhere
		1658	$WNOHANG ||= $^O =~ /^(?:openbsd|netbsd|linux|freebsd|cygwin|MSWin32)$/
		1659	? 1
1064	$WNOHANG = eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;	1660	: eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
1065	}
1066		1661
1067	unless ($CHLD_W) {	1662	unless ($CHLD_W) {
1068	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1663	$CHLD_W = AE::signal CHLD => \&_sigchld;
1069	# child could be a zombie already, so make at least one round	1664	# child could be a zombie already, so make at least one round
1070	&_sigchld;	1665	&_sigchld;
1071	}	1666	}
1072		1667
1073	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	1668	bless [$pid, $arg{cb}], "AnyEvent::Base::child"
1074	}	1669	};
1075		1670
1076	sub AnyEvent::Base::Child::DESTROY {	1671	*AnyEvent::Base::child::DESTROY = sub {
1077	my ($pid, $cb) = @{$_[0]};	1672	my ($pid, $cb) = @{$_[0]};
1078		1673
1079	delete $PID_CB{$pid}{$cb};	1674	delete $PID_CB{$pid}{$cb};
1080	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1675	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
1081		1676
1082	undef $CHLD_W unless keys %PID_CB;	1677	undef $CHLD_W unless keys %PID_CB;
		1678	};
		1679	};
		1680	die if $@;
		1681
		1682	&child
		1683	}
		1684
		1685	# idle emulation is done by simply using a timer, regardless
		1686	# of whether the process is idle or not, and not letting
		1687	# the callback use more than 50% of the time.
		1688	sub idle {
		1689	eval q{ # poor man's autoloading {}
		1690	*idle = sub {
		1691	my (undef, %arg) = @_;
		1692
		1693	my ($cb, $w, $rcb) = $arg{cb};
		1694
		1695	$rcb = sub {
		1696	if ($cb) {
		1697	$w = _time;
		1698	&$cb;
		1699	$w = _time - $w;
		1700
		1701	# never use more then 50% of the time for the idle watcher,
		1702	# within some limits
		1703	$w = 0.0001 if $w < 0.0001;
		1704	$w = 5 if $w > 5;
		1705
		1706	$w = AE::timer $w, 0, $rcb;
		1707	} else {
		1708	# clean up...
		1709	undef $w;
		1710	undef $rcb;
		1711	}
		1712	};
		1713
		1714	$w = AE::timer 0.05, 0, $rcb;
		1715
		1716	bless \\$cb, "AnyEvent::Base::idle"
		1717	};
		1718
		1719	*AnyEvent::Base::idle::DESTROY = sub {
		1720	undef $${$_[0]};
		1721	};
		1722	};
		1723	die if $@;
		1724
		1725	&idle
1083	}	1726	}
1084		1727
1085	package AnyEvent::CondVar;	1728	package AnyEvent::CondVar;
1086		1729
1087	our @ISA = AnyEvent::CondVar::Base::;	1730	our @ISA = AnyEvent::CondVar::Base::;
1088		1731
1089	package AnyEvent::CondVar::Base;	1732	package AnyEvent::CondVar::Base;
1090		1733
1091	use overload	1734	#use overload
1092	'&{}' => sub { my $self = shift; sub { $self->send (@_) } },	1735	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
1093	fallback => 1;	1736	# fallback => 1;
		1737
		1738	# save 300+ kilobytes by dirtily hardcoding overloading
		1739	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1740	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1741	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1742	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1743
		1744	our $WAITING;
1094		1745
1095	sub _send {	1746	sub _send {
1096	# nop	1747	# nop
1097	}	1748	}
1098		1749
…		…
1111	sub ready {	1762	sub ready {
1112	$_[0]{_ae_sent}	1763	$_[0]{_ae_sent}
1113	}	1764	}
1114		1765
1115	sub _wait {	1766	sub _wait {
		1767	$WAITING
		1768	and !$_[0]{_ae_sent}
		1769	and Carp::croak "AnyEvent::CondVar: recursive blocking wait detected";
		1770
		1771	local $WAITING = 1;
1116	AnyEvent->one_event while !$_[0]{_ae_sent};	1772	AnyEvent->one_event while !$_[0]{_ae_sent};
1117	}	1773	}
1118		1774
1119	sub recv {	1775	sub recv {
1120	$_[0]->_wait;	1776	$_[0]->_wait;
…		…
1122	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};	1778	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
1123	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]	1779	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
1124	}	1780	}
1125		1781
1126	sub cb {	1782	sub cb {
1127	$_[0]{_ae_cb} = $_[1] if @_ > 1;	1783	my $cv = shift;
		1784
		1785	@_
		1786	and $cv->{_ae_cb} = shift
		1787	and $cv->{_ae_sent}
		1788	and (delete $cv->{_ae_cb})->($cv);
		1789
1128	$_[0]{_ae_cb}	1790	$cv->{_ae_cb}
1129	}	1791	}
1130		1792
1131	sub begin {	1793	sub begin {
1132	++$_[0]{_ae_counter};	1794	++$_[0]{_ae_counter};
1133	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;	1795	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
…		…
1139	}	1801	}
1140		1802
1141	# undocumented/compatibility with pre-3.4	1803	# undocumented/compatibility with pre-3.4
1142	*broadcast = \&send;	1804	*broadcast = \&send;
1143	*wait = \&_wait;	1805	*wait = \&_wait;
		1806
		1807	=head1 ERROR AND EXCEPTION HANDLING
		1808
		1809	In general, AnyEvent does not do any error handling - it relies on the
		1810	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1811	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1812	checking of all AnyEvent methods, however, which is highly useful during
		1813	development.
		1814
		1815	As for exception handling (i.e. runtime errors and exceptions thrown while
		1816	executing a callback), this is not only highly event-loop specific, but
		1817	also not in any way wrapped by this module, as this is the job of the main
		1818	program.
		1819
		1820	The pure perl event loop simply re-throws the exception (usually
		1821	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1822	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1823	so on.
		1824
		1825	=head1 ENVIRONMENT VARIABLES
		1826
		1827	The following environment variables are used by this module or its
		1828	submodules.
		1829
		1830	Note that AnyEvent will remove I<all> environment variables starting with
		1831	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		1832	enabled.
		1833
		1834	=over 4
		1835
		1836	=item C<PERL_ANYEVENT_VERBOSE>
		1837
		1838	By default, AnyEvent will be completely silent except in fatal
		1839	conditions. You can set this environment variable to make AnyEvent more
		1840	talkative.
		1841
		1842	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1843	conditions, such as not being able to load the event model specified by
		1844	C<PERL_ANYEVENT_MODEL>.
		1845
		1846	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1847	model it chooses.
		1848
		1849	When set to C<8> or higher, then AnyEvent will report extra information on
		1850	which optional modules it loads and how it implements certain features.
		1851
		1852	=item C<PERL_ANYEVENT_STRICT>
		1853
		1854	AnyEvent does not do much argument checking by default, as thorough
		1855	argument checking is very costly. Setting this variable to a true value
		1856	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1857	check the arguments passed to most method calls. If it finds any problems,
		1858	it will croak.
		1859
		1860	In other words, enables "strict" mode.
		1861
		1862	Unlike C<use strict> (or its modern cousin, C<< use L<common::sense>
		1863	>>, it is definitely recommended to keep it off in production. Keeping
		1864	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		1865	can be very useful, however.
		1866
		1867	=item C<PERL_ANYEVENT_MODEL>
		1868
		1869	This can be used to specify the event model to be used by AnyEvent, before
		1870	auto detection and -probing kicks in. It must be a string consisting
		1871	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1872	and the resulting module name is loaded and if the load was successful,
		1873	used as event model. If it fails to load AnyEvent will proceed with
		1874	auto detection and -probing.
		1875
		1876	This functionality might change in future versions.
		1877
		1878	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1879	could start your program like this:
		1880
		1881	PERL_ANYEVENT_MODEL=Perl perl ...
		1882
		1883	=item C<PERL_ANYEVENT_PROTOCOLS>
		1884
		1885	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1886	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1887	of auto probing).
		1888
		1889	Must be set to a comma-separated list of protocols or address families,
		1890	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1891	used, and preference will be given to protocols mentioned earlier in the
		1892	list.
		1893
		1894	This variable can effectively be used for denial-of-service attacks
		1895	against local programs (e.g. when setuid), although the impact is likely
		1896	small, as the program has to handle conenction and other failures anyways.
		1897
		1898	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1899	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1900	- only support IPv4, never try to resolve or contact IPv6
		1901	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1902	IPv6, but prefer IPv6 over IPv4.
		1903
		1904	=item C<PERL_ANYEVENT_EDNS0>
		1905
		1906	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1907	for DNS. This extension is generally useful to reduce DNS traffic, but
		1908	some (broken) firewalls drop such DNS packets, which is why it is off by
		1909	default.
		1910
		1911	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1912	EDNS0 in its DNS requests.
		1913
		1914	=item C<PERL_ANYEVENT_MAX_FORKS>
		1915
		1916	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1917	will create in parallel.
		1918
		1919	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		1920
		1921	The default value for the C<max_outstanding> parameter for the default DNS
		1922	resolver - this is the maximum number of parallel DNS requests that are
		1923	sent to the DNS server.
		1924
		1925	=item C<PERL_ANYEVENT_RESOLV_CONF>
		1926
		1927	The file to use instead of F</etc/resolv.conf> (or OS-specific
		1928	configuration) in the default resolver. When set to the empty string, no
		1929	default config will be used.
		1930
		1931	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		1932
		1933	When neither C<ca_file> nor C<ca_path> was specified during
		1934	L<AnyEvent::TLS> context creation, and either of these environment
		1935	variables exist, they will be used to specify CA certificate locations
		1936	instead of a system-dependent default.
		1937
		1938	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		1939
		1940	When these are set to C<1>, then the respective modules are not
		1941	loaded. Mostly good for testing AnyEvent itself.
		1942
		1943	=back
1144		1944
1145	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1945	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
1146		1946
1147	This is an advanced topic that you do not normally need to use AnyEvent in	1947	This is an advanced topic that you do not normally need to use AnyEvent in
1148	a module. This section is only of use to event loop authors who want to	1948	a module. This section is only of use to event loop authors who want to
…		…
1182		1982
1183	I<rxvt-unicode> also cheats a bit by not providing blocking access to	1983	I<rxvt-unicode> also cheats a bit by not providing blocking access to
1184	condition variables: code blocking while waiting for a condition will	1984	condition variables: code blocking while waiting for a condition will
1185	C<die>. This still works with most modules/usages, and blocking calls must	1985	C<die>. This still works with most modules/usages, and blocking calls must
1186	not be done in an interactive application, so it makes sense.	1986	not be done in an interactive application, so it makes sense.
1187
1188	=head1 ENVIRONMENT VARIABLES
1189
1190	The following environment variables are used by this module:
1191
1192	=over 4
1193
1194	=item C<PERL_ANYEVENT_VERBOSE>
1195
1196	By default, AnyEvent will be completely silent except in fatal
1197	conditions. You can set this environment variable to make AnyEvent more
1198	talkative.
1199
1200	When set to C<1> or higher, causes AnyEvent to warn about unexpected
1201	conditions, such as not being able to load the event model specified by
1202	C<PERL_ANYEVENT_MODEL>.
1203
1204	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
1205	model it chooses.
1206
1207	=item C<PERL_ANYEVENT_STRICT>
1208
1209	AnyEvent does not do much argument checking by default, as thorough
1210	argument checking is very costly. Setting this variable to a true value
1211	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
1212	check the arguments passed to most method calls. If it finds any problems
1213	it will croak.
1214
1215	In other words, enables "strict" mode.
1216
1217	Unlike C<use strict> it is definitely recommended ot keep it off in
1218	production.
1219
1220	=item C<PERL_ANYEVENT_MODEL>
1221
1222	This can be used to specify the event model to be used by AnyEvent, before
1223	auto detection and -probing kicks in. It must be a string consisting
1224	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
1225	and the resulting module name is loaded and if the load was successful,
1226	used as event model. If it fails to load AnyEvent will proceed with
1227	auto detection and -probing.
1228
1229	This functionality might change in future versions.
1230
1231	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
1232	could start your program like this:
1233
1234	PERL_ANYEVENT_MODEL=Perl perl ...
1235
1236	=item C<PERL_ANYEVENT_PROTOCOLS>
1237
1238	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
1239	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
1240	of auto probing).
1241
1242	Must be set to a comma-separated list of protocols or address families,
1243	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
1244	used, and preference will be given to protocols mentioned earlier in the
1245	list.
1246
1247	This variable can effectively be used for denial-of-service attacks
1248	against local programs (e.g. when setuid), although the impact is likely
1249	small, as the program has to handle connection errors already-
1250
1251	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
1252	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
1253	- only support IPv4, never try to resolve or contact IPv6
1254	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
1255	IPv6, but prefer IPv6 over IPv4.
1256
1257	=item C<PERL_ANYEVENT_EDNS0>
1258
1259	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
1260	for DNS. This extension is generally useful to reduce DNS traffic, but
1261	some (broken) firewalls drop such DNS packets, which is why it is off by
1262	default.
1263
1264	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
1265	EDNS0 in its DNS requests.
1266
1267	=item C<PERL_ANYEVENT_MAX_FORKS>
1268
1269	The maximum number of child processes that C<AnyEvent::Util::fork_call>
1270	will create in parallel.
1271
1272	=back
1273		1987
1274	=head1 EXAMPLE PROGRAM	1988	=head1 EXAMPLE PROGRAM
1275		1989
1276	The following program uses an I/O watcher to read data from STDIN, a timer	1990	The following program uses an I/O watcher to read data from STDIN, a timer
1277	to display a message once per second, and a condition variable to quit the	1991	to display a message once per second, and a condition variable to quit the
…		…
1290	warn "read: $input\n"; # output what has been read	2004	warn "read: $input\n"; # output what has been read
1291	$cv->send if $input =~ /^q/i; # quit program if /^q/i	2005	$cv->send if $input =~ /^q/i; # quit program if /^q/i
1292	},	2006	},
1293	);	2007	);
1294		2008
1295	my $time_watcher; # can only be used once
1296
1297	sub new_timer {
1298	$timer = AnyEvent->timer (after => 1, cb => sub {	2009	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
1299	warn "timeout\n"; # print 'timeout' about every second	2010	warn "timeout\n"; # print 'timeout' at most every second
1300	&new_timer; # and restart the time
1301	});	2011	});
1302	}
1303
1304	new_timer; # create first timer
1305		2012
1306	$cv->recv; # wait until user enters /^q/i	2013	$cv->recv; # wait until user enters /^q/i
1307		2014
1308	=head1 REAL-WORLD EXAMPLE	2015	=head1 REAL-WORLD EXAMPLE
1309		2016
…		…
1382		2089
1383	The actual code goes further and collects all errors (C<die>s, exceptions)	2090	The actual code goes further and collects all errors (C<die>s, exceptions)
1384	that occurred during request processing. The C<result> method detects	2091	that occurred during request processing. The C<result> method detects
1385	whether an exception as thrown (it is stored inside the $txn object)	2092	whether an exception as thrown (it is stored inside the $txn object)
1386	and just throws the exception, which means connection errors and other	2093	and just throws the exception, which means connection errors and other
1387	problems get reported tot he code that tries to use the result, not in a	2094	problems get reported to the code that tries to use the result, not in a
1388	random callback.	2095	random callback.
1389		2096
1390	All of this enables the following usage styles:	2097	All of this enables the following usage styles:
1391		2098
1392	1. Blocking:	2099	1. Blocking:
…		…
1440	through AnyEvent. The benchmark creates a lot of timers (with a zero	2147	through AnyEvent. The benchmark creates a lot of timers (with a zero
1441	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,	2148	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
1442	which it is), lets them fire exactly once and destroys them again.	2149	which it is), lets them fire exactly once and destroys them again.
1443		2150
1444	Source code for this benchmark is found as F<eg/bench> in the AnyEvent	2151	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
1445	distribution.	2152	distribution. It uses the L<AE> interface, which makes a real difference
		2153	for the EV and Perl backends only.
1446		2154
1447	=head3 Explanation of the columns	2155	=head3 Explanation of the columns
1448		2156
1449	I<watcher> is the number of event watchers created/destroyed. Since	2157	I<watcher> is the number of event watchers created/destroyed. Since
1450	different event models feature vastly different performances, each event	2158	different event models feature vastly different performances, each event
…		…
1471	watcher.	2179	watcher.
1472		2180
1473	=head3 Results	2181	=head3 Results
1474		2182
1475	name watchers bytes create invoke destroy comment	2183	name watchers bytes create invoke destroy comment
1476	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	2184	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
1477	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	2185	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
1478	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	2186	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
1479	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	2187	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
1480	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	2188	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
1481	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers	2189	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
		2190	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
		2191	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
1482	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	2192	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
1483	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	2193	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
1484	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	2194	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
1485	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	2195	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
1486		2196
1487	=head3 Discussion	2197	=head3 Discussion
1488		2198
1489	The benchmark does I<not> measure scalability of the event loop very	2199	The benchmark does I<not> measure scalability of the event loop very
1490	well. For example, a select-based event loop (such as the pure perl one)	2200	well. For example, a select-based event loop (such as the pure perl one)
…		…
1502	benchmark machine, handling an event takes roughly 1600 CPU cycles with	2212	benchmark machine, handling an event takes roughly 1600 CPU cycles with
1503	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU	2213	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
1504	cycles with POE.	2214	cycles with POE.
1505		2215
1506	C<EV> is the sole leader regarding speed and memory use, which are both	2216	C<EV> is the sole leader regarding speed and memory use, which are both
1507	maximal/minimal, respectively. Even when going through AnyEvent, it uses	2217	maximal/minimal, respectively. When using the L<AE> API there is zero
		2218	overhead (when going through the AnyEvent API create is about 5-6 times
		2219	slower, with other times being equal, so still uses far less memory than
1508	far less memory than any other event loop and is still faster than Event	2220	any other event loop and is still faster than Event natively).
1509	natively.
1510		2221
1511	The pure perl implementation is hit in a few sweet spots (both the	2222	The pure perl implementation is hit in a few sweet spots (both the
1512	constant timeout and the use of a single fd hit optimisations in the perl	2223	constant timeout and the use of a single fd hit optimisations in the perl
1513	interpreter and the backend itself). Nevertheless this shows that it	2224	interpreter and the backend itself). Nevertheless this shows that it
1514	adds very little overhead in itself. Like any select-based backend its	2225	adds very little overhead in itself. Like any select-based backend its
1515	performance becomes really bad with lots of file descriptors (and few of	2226	performance becomes really bad with lots of file descriptors (and few of
1516	them active), of course, but this was not subject of this benchmark.	2227	them active), of course, but this was not subject of this benchmark.
1517		2228
1518	The C<Event> module has a relatively high setup and callback invocation	2229	The C<Event> module has a relatively high setup and callback invocation
1519	cost, but overall scores in on the third place.	2230	cost, but overall scores in on the third place.
		2231
		2232	C<IO::Async> performs admirably well, about on par with C<Event>, even
		2233	when using its pure perl backend.
1520		2234
1521	C<Glib>'s memory usage is quite a bit higher, but it features a	2235	C<Glib>'s memory usage is quite a bit higher, but it features a
1522	faster callback invocation and overall ends up in the same class as	2236	faster callback invocation and overall ends up in the same class as
1523	C<Event>. However, Glib scales extremely badly, doubling the number of	2237	C<Event>. However, Glib scales extremely badly, doubling the number of
1524	watchers increases the processing time by more than a factor of four,	2238	watchers increases the processing time by more than a factor of four,
…		…
1585	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100	2299	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
1586	(1%) are active. This mirrors the activity of large servers with many	2300	(1%) are active. This mirrors the activity of large servers with many
1587	connections, most of which are idle at any one point in time.	2301	connections, most of which are idle at any one point in time.
1588		2302
1589	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent	2303	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
1590	distribution.	2304	distribution. It uses the L<AE> interface, which makes a real difference
		2305	for the EV and Perl backends only.
1591		2306
1592	=head3 Explanation of the columns	2307	=head3 Explanation of the columns
1593		2308
1594	I<sockets> is the number of sockets, and twice the number of "servers" (as	2309	I<sockets> is the number of sockets, and twice the number of "servers" (as
1595	each server has a read and write socket end).	2310	each server has a read and write socket end).
…		…
1602	it to another server. This includes deleting the old timeout and creating	2317	it to another server. This includes deleting the old timeout and creating
1603	a new one that moves the timeout into the future.	2318	a new one that moves the timeout into the future.
1604		2319
1605	=head3 Results	2320	=head3 Results
1606		2321
1607	name sockets create request	2322	name sockets create request
1608	EV 20000 69.01 11.16	2323	EV 20000 62.66 7.99
1609	Perl 20000 73.32 35.87	2324	Perl 20000 68.32 32.64
1610	Event 20000 212.62 257.32	2325	IOAsync 20000 174.06 101.15 epoll
1611	Glib 20000 651.16 1896.30	2326	IOAsync 20000 174.67 610.84 poll
		2327	Event 20000 202.69 242.91
		2328	Glib 20000 557.01 1689.52
1612	POE 20000 349.67 12317.24 uses POE::Loop::Event	2329	POE 20000 341.54 12086.32 uses POE::Loop::Event
1613		2330
1614	=head3 Discussion	2331	=head3 Discussion
1615		2332
1616	This benchmark I<does> measure scalability and overall performance of the	2333	This benchmark I<does> measure scalability and overall performance of the
1617	particular event loop.	2334	particular event loop.
…		…
1619	EV is again fastest. Since it is using epoll on my system, the setup time	2336	EV is again fastest. Since it is using epoll on my system, the setup time
1620	is relatively high, though.	2337	is relatively high, though.
1621		2338
1622	Perl surprisingly comes second. It is much faster than the C-based event	2339	Perl surprisingly comes second. It is much faster than the C-based event
1623	loops Event and Glib.	2340	loops Event and Glib.
		2341
		2342	IO::Async performs very well when using its epoll backend, and still quite
		2343	good compared to Glib when using its pure perl backend.
1624		2344
1625	Event suffers from high setup time as well (look at its code and you will	2345	Event suffers from high setup time as well (look at its code and you will
1626	understand why). Callback invocation also has a high overhead compared to	2346	understand why). Callback invocation also has a high overhead compared to
1627	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event	2347	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
1628	uses select or poll in basically all documented configurations.	2348	uses select or poll in basically all documented configurations.
…		…
1691	=item * C-based event loops perform very well with small number of	2411	=item * C-based event loops perform very well with small number of
1692	watchers, as the management overhead dominates.	2412	watchers, as the management overhead dominates.
1693		2413
1694	=back	2414	=back
1695		2415
		2416	=head2 THE IO::Lambda BENCHMARK
		2417
		2418	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2419	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2420	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2421	shouldn't come as a surprise to anybody). As such, the benchmark is
		2422	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2423	very optimal. But how would AnyEvent compare when used without the extra
		2424	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2425
		2426	The benchmark itself creates an echo-server, and then, for 500 times,
		2427	connects to the echo server, sends a line, waits for the reply, and then
		2428	creates the next connection. This is a rather bad benchmark, as it doesn't
		2429	test the efficiency of the framework or much non-blocking I/O, but it is a
		2430	benchmark nevertheless.
		2431
		2432	name runtime
		2433	Lambda/select 0.330 sec
		2434	+ optimized 0.122 sec
		2435	Lambda/AnyEvent 0.327 sec
		2436	+ optimized 0.138 sec
		2437	Raw sockets/select 0.077 sec
		2438	POE/select, components 0.662 sec
		2439	POE/select, raw sockets 0.226 sec
		2440	POE/select, optimized 0.404 sec
		2441
		2442	AnyEvent/select/nb 0.085 sec
		2443	AnyEvent/EV/nb 0.068 sec
		2444	+state machine 0.134 sec
		2445
		2446	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2447	benchmarks actually make blocking connects and use 100% blocking I/O,
		2448	defeating the purpose of an event-based solution. All of the newly
		2449	written AnyEvent benchmarks use 100% non-blocking connects (using
		2450	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2451	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2452	generally require a lot more bookkeeping and event handling than blocking
		2453	connects (which involve a single syscall only).
		2454
		2455	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2456	offers similar expressive power as POE and IO::Lambda, using conventional
		2457	Perl syntax. This means that both the echo server and the client are 100%
		2458	non-blocking, further placing it at a disadvantage.
		2459
		2460	As you can see, the AnyEvent + EV combination even beats the
		2461	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2462	backend easily beats IO::Lambda and POE.
		2463
		2464	And even the 100% non-blocking version written using the high-level (and
		2465	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda
		2466	higher level ("unoptimised") abstractions by a large margin, even though
		2467	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
		2468
		2469	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2470	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2471	part of the IO::Lambda distribution and were used without any changes.
		2472
		2473
		2474	=head1 SIGNALS
		2475
		2476	AnyEvent currently installs handlers for these signals:
		2477
		2478	=over 4
		2479
		2480	=item SIGCHLD
		2481
		2482	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2483	emulation for event loops that do not support them natively. Also, some
		2484	event loops install a similar handler.
		2485
		2486	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2487	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2488
		2489	=item SIGPIPE
		2490
		2491	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2492	when AnyEvent gets loaded.
		2493
		2494	The rationale for this is that AnyEvent users usually do not really depend
		2495	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2496	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2497	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2498	some random socket.
		2499
		2500	The rationale for installing a no-op handler as opposed to ignoring it is
		2501	that this way, the handler will be restored to defaults on exec.
		2502
		2503	Feel free to install your own handler, or reset it to defaults.
		2504
		2505	=back
		2506
		2507	=cut
		2508
		2509	undef $SIG{CHLD}
		2510	if $SIG{CHLD} eq 'IGNORE';
		2511
		2512	$SIG{PIPE} = sub { }
		2513	unless defined $SIG{PIPE};
		2514
		2515	=head1 RECOMMENDED/OPTIONAL MODULES
		2516
		2517	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2518	its built-in modules) are required to use it.
		2519
		2520	That does not mean that AnyEvent won't take advantage of some additional
		2521	modules if they are installed.
		2522
		2523	This section explains which additional modules will be used, and how they
		2524	affect AnyEvent's operation.
		2525
		2526	=over 4
		2527
		2528	=item L<Async::Interrupt>
		2529
		2530	This slightly arcane module is used to implement fast signal handling: To
		2531	my knowledge, there is no way to do completely race-free and quick
		2532	signal handling in pure perl. To ensure that signals still get
		2533	delivered, AnyEvent will start an interval timer to wake up perl (and
		2534	catch the signals) with some delay (default is 10 seconds, look for
		2535	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2536
		2537	If this module is available, then it will be used to implement signal
		2538	catching, which means that signals will not be delayed, and the event loop
		2539	will not be interrupted regularly, which is more efficient (and good for
		2540	battery life on laptops).
		2541
		2542	This affects not just the pure-perl event loop, but also other event loops
		2543	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2544
		2545	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2546	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2547	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2548	does nothing for those backends.
		2549
		2550	=item L<EV>
		2551
		2552	This module isn't really "optional", as it is simply one of the backend
		2553	event loops that AnyEvent can use. However, it is simply the best event
		2554	loop available in terms of features, speed and stability: It supports
		2555	the AnyEvent API optimally, implements all the watcher types in XS, does
		2556	automatic timer adjustments even when no monotonic clock is available,
		2557	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2558	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2559	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2560
		2561	If you only use backends that rely on another event loop (e.g. C<Tk>),
		2562	then this module will do nothing for you.
		2563
		2564	=item L<Guard>
		2565
		2566	The guard module, when used, will be used to implement
		2567	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2568	lot less memory), but otherwise doesn't affect guard operation much. It is
		2569	purely used for performance.
		2570
		2571	=item L<JSON> and L<JSON::XS>
		2572
		2573	One of these modules is required when you want to read or write JSON data
		2574	via L<AnyEvent::Handle>. L<JSON> is also written in pure-perl, but can take
		2575	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2576
		2577	=item L<Net::SSLeay>
		2578
		2579	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2580	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2581	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2582
		2583	=item L<Time::HiRes>
		2584
		2585	This module is part of perl since release 5.008. It will be used when the
		2586	chosen event library does not come with a timing source of its own. The
		2587	pure-perl event loop (L<AnyEvent::Impl::Perl>) will additionally use it to
		2588	try to use a monotonic clock for timing stability.
		2589
		2590	=back
		2591
1696		2592
1697	=head1 FORK	2593	=head1 FORK
1698		2594
1699	Most event libraries are not fork-safe. The ones who are usually are	2595	Most event libraries are not fork-safe. The ones who are usually are
1700	because they rely on inefficient but fork-safe C<select> or C<poll>	2596	because they rely on inefficient but fork-safe C<select> or C<poll> calls
1701	calls. Only L<EV> is fully fork-aware.	2597	- higher performance APIs such as BSD's kqueue or the dreaded Linux epoll
		2598	are usually badly thought-out hacks that are incompatible with fork in
		2599	one way or another. Only L<EV> is fully fork-aware and ensures that you
		2600	continue event-processing in both parent and child (or both, if you know
		2601	what you are doing).
		2602
		2603	This means that, in general, you cannot fork and do event processing in
		2604	the child if the event library was initialised before the fork (which
		2605	usually happens when the first AnyEvent watcher is created, or the library
		2606	is loaded).
1702		2607
1703	If you have to fork, you must either do so I<before> creating your first	2608	If you have to fork, you must either do so I<before> creating your first
1704	watcher OR you must not use AnyEvent at all in the child.	2609	watcher OR you must not use AnyEvent at all in the child OR you must do
		2610	something completely out of the scope of AnyEvent.
		2611
		2612	The problem of doing event processing in the parent I<and> the child
		2613	is much more complicated: even for backends that I<are> fork-aware or
		2614	fork-safe, their behaviour is not usually what you want: fork clones all
		2615	watchers, that means all timers, I/O watchers etc. are active in both
		2616	parent and child, which is almost never what you want. USing C<exec>
		2617	to start worker children from some kind of manage rprocess is usually
		2618	preferred, because it is much easier and cleaner, at the expense of having
		2619	to have another binary.
1705		2620
1706		2621
1707	=head1 SECURITY CONSIDERATIONS	2622	=head1 SECURITY CONSIDERATIONS
1708		2623
1709	AnyEvent can be forced to load any event model via	2624	AnyEvent can be forced to load any event model via
…		…
1721	use AnyEvent;	2636	use AnyEvent;
1722		2637
1723	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can	2638	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1724	be used to probe what backend is used and gain other information (which is	2639	be used to probe what backend is used and gain other information (which is
1725	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and	2640	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
1726	$ENV{PERL_ANYEGENT_STRICT}.	2641	$ENV{PERL_ANYEVENT_STRICT}.
		2642
		2643	Note that AnyEvent will remove I<all> environment variables starting with
		2644	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2645	enabled.
1727		2646
1728		2647
1729	=head1 BUGS	2648	=head1 BUGS
1730		2649
1731	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard	2650	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
1732	to work around. If you suffer from memleaks, first upgrade to Perl 5.10	2651	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
1733	and check wether the leaks still show up. (Perl 5.10.0 has other annoying	2652	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
1734	mamleaks, such as leaking on C<map> and C<grep> but it is usually not as	2653	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
1735	pronounced).	2654	pronounced).
1736		2655
1737		2656
1738	=head1 SEE ALSO	2657	=head1 SEE ALSO
1739		2658
…		…
1743	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.	2662	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
1744		2663
1745	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,	2664	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
1746	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,	2665	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
1747	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,	2666	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1748	L<AnyEvent::Impl::POE>.	2667	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>, L<Anyevent::Impl::Irssi>.
1749		2668
1750	Non-blocking file handles, sockets, TCP clients and	2669	Non-blocking file handles, sockets, TCP clients and
1751	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>.	2670	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
1752		2671
1753	Asynchronous DNS: L<AnyEvent::DNS>.	2672	Asynchronous DNS: L<AnyEvent::DNS>.
1754		2673
1755	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,	2674	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>,
		2675	L<Coro::Event>,
1756		2676
1757	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>, L<AnyEvent::DNS>.	2677	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::XMPP>,
		2678	L<AnyEvent::HTTP>.
1758		2679
1759		2680
1760	=head1 AUTHOR	2681	=head1 AUTHOR
1761		2682
1762	Marc Lehmann <schmorp@schmorp.de>	2683	Marc Lehmann <schmorp@schmorp.de>

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