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Revision 1.137 by root, Mon May 26 03:27:52 2008 UTC vs.
Revision 1.250 by root, Mon Jul 20 07:12:38 2009 UTC

1	=head1 => NAME	1	=head1 NAME
2		2
3	AnyEvent - provide framework for multiple event loops	3	AnyEvent - events independent of event loop implementation
4		4
5	EV, Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event loops	5	EV, Event, Glib, Tk, Perl, Event::Lib, Qt and POE are various supported
		6	event loops.
6		7
7	=head1 SYNOPSIS	8	=head1 SYNOPSIS
8		9
9	use AnyEvent;	10	use AnyEvent;
10		11
		12	# file descriptor readable
11	my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub {	13	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
		14
		15	# one-shot or repeating timers
		16	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
		17	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...
		18
		19	print AnyEvent->now; # prints current event loop time
		20	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
		21
		22	# POSIX signal
		23	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
		24
		25	# child process exit
		26	my $w = AnyEvent->child (pid => $pid, cb => sub {
		27	my ($pid, $status) = @_;
12	...	28	...
13	});	29	});
14		30
15	my $w = AnyEvent->timer (after => $seconds, cb => sub {	31	# called when event loop idle (if applicable)
16	...	32	my $w = AnyEvent->idle (cb => sub { ... });
17	});
18		33
19	my $w = AnyEvent->condvar; # stores whether a condition was flagged	34	my $w = AnyEvent->condvar; # stores whether a condition was flagged
20	$w->send; # wake up current and all future recv's	35	$w->send; # wake up current and all future recv's
21	$w->recv; # enters "main loop" till $condvar gets ->send	36	$w->recv; # enters "main loop" till $condvar gets ->send
		37	# use a condvar in callback mode:
		38	$w->cb (sub { $_[0]->recv });
		39
		40	=head1 INTRODUCTION/TUTORIAL
		41
		42	This manpage is mainly a reference manual. If you are interested
		43	in a tutorial or some gentle introduction, have a look at the
		44	L<AnyEvent::Intro> manpage.
		45
		46	=head1 SUPPORT
		47
		48	There is a mailinglist for discussing all things AnyEvent, and an IRC
		49	channel, too.
		50
		51	See the AnyEvent project page at the B<Schmorpforge Ta-Sa Software
		52	Respository>, at L<http://anyevent.schmorp.de>, for more info.
22		53
23	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)	54	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
24		55
25	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	56	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
26	nowadays. So what is different about AnyEvent?	57	nowadays. So what is different about AnyEvent?
27		58
28	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of	59	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
29	policy> and AnyEvent is I<small and efficient>.	60	policy> and AnyEvent is I<small and efficient>.
30		61
31	First and foremost, I<AnyEvent is not an event model> itself, it only	62	First and foremost, I<AnyEvent is not an event model> itself, it only
32	interfaces to whatever event model the main program happens to use in a	63	interfaces to whatever event model the main program happens to use, in a
33	pragmatic way. For event models and certain classes of immortals alike,	64	pragmatic way. For event models and certain classes of immortals alike,
34	the statement "there can only be one" is a bitter reality: In general,	65	the statement "there can only be one" is a bitter reality: In general,
35	only one event loop can be active at the same time in a process. AnyEvent	66	only one event loop can be active at the same time in a process. AnyEvent
36	helps hiding the differences between those event loops.	67	cannot change this, but it can hide the differences between those event
		68	loops.
37		69
38	The goal of AnyEvent is to offer module authors the ability to do event	70	The goal of AnyEvent is to offer module authors the ability to do event
39	programming (waiting for I/O or timer events) without subscribing to a	71	programming (waiting for I/O or timer events) without subscribing to a
40	religion, a way of living, and most importantly: without forcing your	72	religion, a way of living, and most importantly: without forcing your
41	module users into the same thing by forcing them to use the same event	73	module users into the same thing by forcing them to use the same event
42	model you use.	74	model you use.
43		75
44	For modules like POE or IO::Async (which is a total misnomer as it is	76	For modules like POE or IO::Async (which is a total misnomer as it is
45	actually doing all I/O I<synchronously>...), using them in your module is	77	actually doing all I/O I<synchronously>...), using them in your module is
46	like joining a cult: After you joined, you are dependent on them and you	78	like joining a cult: After you joined, you are dependent on them and you
47	cannot use anything else, as it is simply incompatible to everything that	79	cannot use anything else, as they are simply incompatible to everything
48	isn't itself. What's worse, all the potential users of your module are	80	that isn't them. What's worse, all the potential users of your
49	I<also> forced to use the same event loop you use.	81	module are I<also> forced to use the same event loop you use.
50		82
51	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	83	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
52	fine. AnyEvent + Tk works fine etc. etc. but none of these work together	84	fine. AnyEvent + Tk works fine etc. etc. but none of these work together
53	with the rest: POE + IO::Async? no go. Tk + Event? no go. Again: if	85	with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if
54	your module uses one of those, every user of your module has to use it,	86	your module uses one of those, every user of your module has to use it,
55	too. But if your module uses AnyEvent, it works transparently with all	87	too. But if your module uses AnyEvent, it works transparently with all
56	event models it supports (including stuff like POE and IO::Async, as long	88	event models it supports (including stuff like IO::Async, as long as those
57	as those use one of the supported event loops. It is trivial to add new	89	use one of the supported event loops. It is trivial to add new event loops
58	event loops to AnyEvent, too, so it is future-proof).	90	to AnyEvent, too, so it is future-proof).
59		91
60	In addition to being free of having to use I<the one and only true event	92	In addition to being free of having to use I<the one and only true event
61	model>, AnyEvent also is free of bloat and policy: with POE or similar	93	model>, AnyEvent also is free of bloat and policy: with POE or similar
62	modules, you get an enormous amount of code and strict rules you have to	94	modules, you get an enormous amount of code and strict rules you have to
63	follow. AnyEvent, on the other hand, is lean and up to the point, by only	95	follow. AnyEvent, on the other hand, is lean and up to the point, by only
64	offering the functionality that is necessary, in as thin as a wrapper as	96	offering the functionality that is necessary, in as thin as a wrapper as
65	technically possible.	97	technically possible.
66		98
		99	Of course, AnyEvent comes with a big (and fully optional!) toolbox
		100	of useful functionality, such as an asynchronous DNS resolver, 100%
		101	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
		102	such as Windows) and lots of real-world knowledge and workarounds for
		103	platform bugs and differences.
		104
67	Of course, if you want lots of policy (this can arguably be somewhat	105	Now, if you I<do want> lots of policy (this can arguably be somewhat
68	useful) and you want to force your users to use the one and only event	106	useful) and you want to force your users to use the one and only event
69	model, you should I<not> use this module.	107	model, you should I<not> use this module.
70		108
71	=head1 DESCRIPTION	109	=head1 DESCRIPTION
72		110
…		…
102	starts using it, all bets are off. Maybe you should tell their authors to	140	starts using it, all bets are off. Maybe you should tell their authors to
103	use AnyEvent so their modules work together with others seamlessly...	141	use AnyEvent so their modules work together with others seamlessly...
104		142
105	The pure-perl implementation of AnyEvent is called	143	The pure-perl implementation of AnyEvent is called
106	C<AnyEvent::Impl::Perl>. Like other event modules you can load it	144	C<AnyEvent::Impl::Perl>. Like other event modules you can load it
107	explicitly.	145	explicitly and enjoy the high availability of that event loop :)
108		146
109	=head1 WATCHERS	147	=head1 WATCHERS
110		148
111	AnyEvent has the central concept of a I<watcher>, which is an object that	149	AnyEvent has the central concept of a I<watcher>, which is an object that
112	stores relevant data for each kind of event you are waiting for, such as	150	stores relevant data for each kind of event you are waiting for, such as
…		…
115	These watchers are normal Perl objects with normal Perl lifetime. After	153	These watchers are normal Perl objects with normal Perl lifetime. After
116	creating a watcher it will immediately "watch" for events and invoke the	154	creating a watcher it will immediately "watch" for events and invoke the
117	callback when the event occurs (of course, only when the event model	155	callback when the event occurs (of course, only when the event model
118	is in control).	156	is in control).
119		157
		158	Note that B<callbacks must not permanently change global variables>
		159	potentially in use by the event loop (such as C<$_> or C<$[>) and that B<<
		160	callbacks must not C<die> >>. The former is good programming practise in
		161	Perl and the latter stems from the fact that exception handling differs
		162	widely between event loops.
		163
120	To disable the watcher you have to destroy it (e.g. by setting the	164	To disable the watcher you have to destroy it (e.g. by setting the
121	variable you store it in to C<undef> or otherwise deleting all references	165	variable you store it in to C<undef> or otherwise deleting all references
122	to it).	166	to it).
123		167
124	All watchers are created by calling a method on the C<AnyEvent> class.	168	All watchers are created by calling a method on the C<AnyEvent> class.
…		…
126	Many watchers either are used with "recursion" (repeating timers for	170	Many watchers either are used with "recursion" (repeating timers for
127	example), or need to refer to their watcher object in other ways.	171	example), or need to refer to their watcher object in other ways.
128		172
129	An any way to achieve that is this pattern:	173	An any way to achieve that is this pattern:
130		174
131	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	175	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
132	# you can use $w here, for example to undef it	176	# you can use $w here, for example to undef it
133	undef $w;	177	undef $w;
134	});	178	});
135		179
136	Note that C<my $w; $w => combination. This is necessary because in Perl,	180	Note that C<my $w; $w => combination. This is necessary because in Perl,
137	my variables are only visible after the statement in which they are	181	my variables are only visible after the statement in which they are
138	declared.	182	declared.
139		183
140	=head2 I/O WATCHERS	184	=head2 I/O WATCHERS
141		185
142	You can create an I/O watcher by calling the C<< AnyEvent->io >> method	186	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
143	with the following mandatory key-value pairs as arguments:	187	with the following mandatory key-value pairs as arguments:
144		188
145	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch	189	C<fh> is the Perl I<file handle> (or a naked file descriptor) to watch
		190	for events (AnyEvent might or might not keep a reference to this file
		191	handle). Note that only file handles pointing to things for which
		192	non-blocking operation makes sense are allowed. This includes sockets,
		193	most character devices, pipes, fifos and so on, but not for example files
		194	or block devices.
		195
146	for events. C<poll> must be a string that is either C<r> or C<w>,	196	C<poll> must be a string that is either C<r> or C<w>, which creates a
147	which creates a watcher waiting for "r"eadable or "w"ritable events,	197	watcher waiting for "r"eadable or "w"ritable events, respectively.
		198
148	respectively. C<cb> is the callback to invoke each time the file handle	199	C<cb> is the callback to invoke each time the file handle becomes ready.
149	becomes ready.
150		200
151	Although the callback might get passed parameters, their value and	201	Although the callback might get passed parameters, their value and
152	presence is undefined and you cannot rely on them. Portable AnyEvent	202	presence is undefined and you cannot rely on them. Portable AnyEvent
153	callbacks cannot use arguments passed to I/O watcher callbacks.	203	callbacks cannot use arguments passed to I/O watcher callbacks.
154		204
…		…
158		208
159	Some event loops issue spurious readyness notifications, so you should	209	Some event loops issue spurious readyness notifications, so you should
160	always use non-blocking calls when reading/writing from/to your file	210	always use non-blocking calls when reading/writing from/to your file
161	handles.	211	handles.
162		212
163	Example:
164
165	# wait for readability of STDIN, then read a line and disable the watcher	213	Example: wait for readability of STDIN, then read a line and disable the
		214	watcher.
		215
166	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	216	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
167	chomp (my $input = <STDIN>);	217	chomp (my $input = <STDIN>);
168	warn "read: $input\n";	218	warn "read: $input\n";
169	undef $w;	219	undef $w;
170	});	220	});
…		…
180		230
181	Although the callback might get passed parameters, their value and	231	Although the callback might get passed parameters, their value and
182	presence is undefined and you cannot rely on them. Portable AnyEvent	232	presence is undefined and you cannot rely on them. Portable AnyEvent
183	callbacks cannot use arguments passed to time watcher callbacks.	233	callbacks cannot use arguments passed to time watcher callbacks.
184		234
185	The timer callback will be invoked at most once: if you want a repeating	235	The callback will normally be invoked once only. If you specify another
186	timer you have to create a new watcher (this is a limitation by both Tk	236	parameter, C<interval>, as a strictly positive number (> 0), then the
187	and Glib).	237	callback will be invoked regularly at that interval (in fractional
		238	seconds) after the first invocation. If C<interval> is specified with a
		239	false value, then it is treated as if it were missing.
188		240
189	Example:	241	The callback will be rescheduled before invoking the callback, but no
		242	attempt is done to avoid timer drift in most backends, so the interval is
		243	only approximate.
190		244
191	# fire an event after 7.7 seconds	245	Example: fire an event after 7.7 seconds.
		246
192	my $w = AnyEvent->timer (after => 7.7, cb => sub {	247	my $w = AnyEvent->timer (after => 7.7, cb => sub {
193	warn "timeout\n";	248	warn "timeout\n";
194	});	249	});
195		250
196	# to cancel the timer:	251	# to cancel the timer:
197	undef $w;	252	undef $w;
198		253
199	Example 2:
200
201	# fire an event after 0.5 seconds, then roughly every second	254	Example 2: fire an event after 0.5 seconds, then roughly every second.
202	my $w;
203		255
204	my $cb = sub {
205	# cancel the old timer while creating a new one
206	$w = AnyEvent->timer (after => 1, cb => $cb);	256	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		257	warn "timeout\n";
207	};	258	};
208
209	# start the "loop" by creating the first watcher
210	$w = AnyEvent->timer (after => 0.5, cb => $cb);
211		259
212	=head3 TIMING ISSUES	260	=head3 TIMING ISSUES
213		261
214	There are two ways to handle timers: based on real time (relative, "fire	262	There are two ways to handle timers: based on real time (relative, "fire
215	in 10 seconds") and based on wallclock time (absolute, "fire at 12	263	in 10 seconds") and based on wallclock time (absolute, "fire at 12
…		…
227	timers.	275	timers.
228		276
229	AnyEvent always prefers relative timers, if available, matching the	277	AnyEvent always prefers relative timers, if available, matching the
230	AnyEvent API.	278	AnyEvent API.
231		279
		280	AnyEvent has two additional methods that return the "current time":
		281
		282	=over 4
		283
		284	=item AnyEvent->time
		285
		286	This returns the "current wallclock time" as a fractional number of
		287	seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
		288	return, and the result is guaranteed to be compatible with those).
		289
		290	It progresses independently of any event loop processing, i.e. each call
		291	will check the system clock, which usually gets updated frequently.
		292
		293	=item AnyEvent->now
		294
		295	This also returns the "current wallclock time", but unlike C<time>, above,
		296	this value might change only once per event loop iteration, depending on
		297	the event loop (most return the same time as C<time>, above). This is the
		298	time that AnyEvent's timers get scheduled against.
		299
		300	I<In almost all cases (in all cases if you don't care), this is the
		301	function to call when you want to know the current time.>
		302
		303	This function is also often faster then C<< AnyEvent->time >>, and
		304	thus the preferred method if you want some timestamp (for example,
		305	L<AnyEvent::Handle> uses this to update it's activity timeouts).
		306
		307	The rest of this section is only of relevance if you try to be very exact
		308	with your timing, you can skip it without bad conscience.
		309
		310	For a practical example of when these times differ, consider L<Event::Lib>
		311	and L<EV> and the following set-up:
		312
		313	The event loop is running and has just invoked one of your callback at
		314	time=500 (assume no other callbacks delay processing). In your callback,
		315	you wait a second by executing C<sleep 1> (blocking the process for a
		316	second) and then (at time=501) you create a relative timer that fires
		317	after three seconds.
		318
		319	With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
		320	both return C<501>, because that is the current time, and the timer will
		321	be scheduled to fire at time=504 (C<501> + C<3>).
		322
		323	With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
		324	time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
		325	last event processing phase started. With L<EV>, your timer gets scheduled
		326	to run at time=503 (C<500> + C<3>).
		327
		328	In one sense, L<Event::Lib> is more exact, as it uses the current time
		329	regardless of any delays introduced by event processing. However, most
		330	callbacks do not expect large delays in processing, so this causes a
		331	higher drift (and a lot more system calls to get the current time).
		332
		333	In another sense, L<EV> is more exact, as your timer will be scheduled at
		334	the same time, regardless of how long event processing actually took.
		335
		336	In either case, if you care (and in most cases, you don't), then you
		337	can get whatever behaviour you want with any event loop, by taking the
		338	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
		339	account.
		340
		341	=item AnyEvent->now_update
		342
		343	Some event loops (such as L<EV> or L<AnyEvent::Impl::Perl>) cache
		344	the current time for each loop iteration (see the discussion of L<<
		345	AnyEvent->now >>, above).
		346
		347	When a callback runs for a long time (or when the process sleeps), then
		348	this "current" time will differ substantially from the real time, which
		349	might affect timers and time-outs.
		350
		351	When this is the case, you can call this method, which will update the
		352	event loop's idea of "current time".
		353
		354	Note that updating the time I<might> cause some events to be handled.
		355
		356	=back
		357
232	=head2 SIGNAL WATCHERS	358	=head2 SIGNAL WATCHERS
233		359
234	You can watch for signals using a signal watcher, C<signal> is the signal	360	You can watch for signals using a signal watcher, C<signal> is the signal
235	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to	361	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
236	be invoked whenever a signal occurs.	362	callback to be invoked whenever a signal occurs.
237		363
238	Although the callback might get passed parameters, their value and	364	Although the callback might get passed parameters, their value and
239	presence is undefined and you cannot rely on them. Portable AnyEvent	365	presence is undefined and you cannot rely on them. Portable AnyEvent
240	callbacks cannot use arguments passed to signal watcher callbacks.	366	callbacks cannot use arguments passed to signal watcher callbacks.
241		367
…		…
243	invocation, and callback invocation will be synchronous. Synchronous means	369	invocation, and callback invocation will be synchronous. Synchronous means
244	that it might take a while until the signal gets handled by the process,	370	that it might take a while until the signal gets handled by the process,
245	but it is guaranteed not to interrupt any other callbacks.	371	but it is guaranteed not to interrupt any other callbacks.
246		372
247	The main advantage of using these watchers is that you can share a signal	373	The main advantage of using these watchers is that you can share a signal
248	between multiple watchers.	374	between multiple watchers, and AnyEvent will ensure that signals will not
		375	interrupt your program at bad times.
249		376
250	This watcher might use C<%SIG>, so programs overwriting those signals	377	This watcher might use C<%SIG> (depending on the event loop used),
251	directly will likely not work correctly.	378	so programs overwriting those signals directly will likely not work
		379	correctly.
252		380
253	Example: exit on SIGINT	381	Example: exit on SIGINT
254		382
255	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	383	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
256		384
		385	=head3 Signal Races, Delays and Workarounds
		386
		387	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		388	callbacks to signals in a generic way, which is a pity, as you cannot do
		389	race-free signal handling in perl. AnyEvent will try to do it's best, but
		390	in some cases, signals will be delayed. The maximum time a signal might
		391	be delayed is specified in C<$AnyEvent::MAX_SIGNAL_LATENCY> (default: 10
		392	seconds). This variable can be changed only before the first signal
		393	watcher is created, and should be left alone otherwise. Higher values
		394	will cause fewer spurious wake-ups, which is better for power and CPU
		395	saving. All these problems can be avoided by installing the optional
		396	L<Async::Interrupt> module. This will not work with inherently broken
		397	event loops such as L<Event> or L<Event::Lib> (and not with L<POE>
		398	currently, as POE does it's own workaround with one-second latency). With
		399	those, you just have to suffer the delays.
		400
257	=head2 CHILD PROCESS WATCHERS	401	=head2 CHILD PROCESS WATCHERS
258		402
259	You can also watch on a child process exit and catch its exit status.	403	You can also watch on a child process exit and catch its exit status.
260		404
261	The child process is specified by the C<pid> argument (if set to C<0>, it	405	The child process is specified by the C<pid> argument (if set to C<0>, it
262	watches for any child process exit). The watcher will trigger as often	406	watches for any child process exit). The watcher will triggered only when
263	as status change for the child are received. This works by installing a	407	the child process has finished and an exit status is available, not on
264	signal handler for C<SIGCHLD>. The callback will be called with the pid	408	any trace events (stopped/continued).
265	and exit status (as returned by waitpid), so unlike other watcher types,	409
266	you I<can> rely on child watcher callback arguments.	410	The callback will be called with the pid and exit status (as returned by
		411	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		412	callback arguments.
		413
		414	This watcher type works by installing a signal handler for C<SIGCHLD>,
		415	and since it cannot be shared, nothing else should use SIGCHLD or reap
		416	random child processes (waiting for specific child processes, e.g. inside
		417	C<system>, is just fine).
267		418
268	There is a slight catch to child watchers, however: you usually start them	419	There is a slight catch to child watchers, however: you usually start them
269	I<after> the child process was created, and this means the process could	420	I<after> the child process was created, and this means the process could
270	have exited already (and no SIGCHLD will be sent anymore).	421	have exited already (and no SIGCHLD will be sent anymore).
271		422
272	Not all event models handle this correctly (POE doesn't), but even for	423	Not all event models handle this correctly (neither POE nor IO::Async do,
		424	see their AnyEvent::Impl manpages for details), but even for event models
273	event models that I<do> handle this correctly, they usually need to be	425	that I<do> handle this correctly, they usually need to be loaded before
274	loaded before the process exits (i.e. before you fork in the first place).	426	the process exits (i.e. before you fork in the first place). AnyEvent's
		427	pure perl event loop handles all cases correctly regardless of when you
		428	start the watcher.
275		429
276	This means you cannot create a child watcher as the very first thing in an	430	This means you cannot create a child watcher as the very first
277	AnyEvent program, you I<have> to create at least one watcher before you	431	thing in an AnyEvent program, you I<have> to create at least one
278	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).	432	watcher before you C<fork> the child (alternatively, you can call
		433	C<AnyEvent::detect>).
		434
		435	As most event loops do not support waiting for child events, they will be
		436	emulated by AnyEvent in most cases, in which the latency and race problems
		437	mentioned in the description of signal watchers apply.
279		438
280	Example: fork a process and wait for it	439	Example: fork a process and wait for it
281		440
282	my $done = AnyEvent->condvar;	441	my $done = AnyEvent->condvar;
283		442
284	my $pid = fork or exit 5;	443	my $pid = fork or exit 5;
285		444
286	my $w = AnyEvent->child (	445	my $w = AnyEvent->child (
287	pid => $pid,	446	pid => $pid,
288	cb => sub {	447	cb => sub {
289	my ($pid, $status) = @_;	448	my ($pid, $status) = @_;
290	warn "pid $pid exited with status $status";	449	warn "pid $pid exited with status $status";
291	$done->send;	450	$done->send;
292	},	451	},
293	);	452	);
294		453
295	# do something else, then wait for process exit	454	# do something else, then wait for process exit
296	$done->recv;	455	$done->recv;
		456
		457	=head2 IDLE WATCHERS
		458
		459	Sometimes there is a need to do something, but it is not so important
		460	to do it instantly, but only when there is nothing better to do. This
		461	"nothing better to do" is usually defined to be "no other events need
		462	attention by the event loop".
		463
		464	Idle watchers ideally get invoked when the event loop has nothing
		465	better to do, just before it would block the process to wait for new
		466	events. Instead of blocking, the idle watcher is invoked.
		467
		468	Most event loops unfortunately do not really support idle watchers (only
		469	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		470	will simply call the callback "from time to time".
		471
		472	Example: read lines from STDIN, but only process them when the
		473	program is otherwise idle:
		474
		475	my @lines; # read data
		476	my $idle_w;
		477	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		478	push @lines, scalar <STDIN>;
		479
		480	# start an idle watcher, if not already done
		481	$idle_w ||= AnyEvent->idle (cb => sub {
		482	# handle only one line, when there are lines left
		483	if (my $line = shift @lines) {
		484	print "handled when idle: $line";
		485	} else {
		486	# otherwise disable the idle watcher again
		487	undef $idle_w;
		488	}
		489	});
		490	});
297		491
298	=head2 CONDITION VARIABLES	492	=head2 CONDITION VARIABLES
299		493
300	If you are familiar with some event loops you will know that all of them	494	If you are familiar with some event loops you will know that all of them
301	require you to run some blocking "loop", "run" or similar function that	495	require you to run some blocking "loop", "run" or similar function that
302	will actively watch for new events and call your callbacks.	496	will actively watch for new events and call your callbacks.
303		497
304	AnyEvent is different, it expects somebody else to run the event loop and	498	AnyEvent is slightly different: it expects somebody else to run the event
305	will only block when necessary (usually when told by the user).	499	loop and will only block when necessary (usually when told by the user).
306		500
307	The instrument to do that is called a "condition variable", so called	501	The instrument to do that is called a "condition variable", so called
308	because they represent a condition that must become true.	502	because they represent a condition that must become true.
		503
		504	Now is probably a good time to look at the examples further below.
309		505
310	Condition variables can be created by calling the C<< AnyEvent->condvar	506	Condition variables can be created by calling the C<< AnyEvent->condvar
311	>> method, usually without arguments. The only argument pair allowed is	507	>> method, usually without arguments. The only argument pair allowed is
312	C<cb>, which specifies a callback to be called when the condition variable	508	C<cb>, which specifies a callback to be called when the condition variable
313	becomes true.	509	becomes true, with the condition variable as the first argument (but not
		510	the results).
314		511
315	After creation, the condition variable is "false" until it becomes "true"	512	After creation, the condition variable is "false" until it becomes "true"
316	by calling the C<send> method (or calling the condition variable as if it	513	by calling the C<send> method (or calling the condition variable as if it
317	were a callback, read about the caveats in the description for the C<<	514	were a callback, read about the caveats in the description for the C<<
318	->send >> method).	515	->send >> method).
…		…
320	Condition variables are similar to callbacks, except that you can	517	Condition variables are similar to callbacks, except that you can
321	optionally wait for them. They can also be called merge points - points	518	optionally wait for them. They can also be called merge points - points
322	in time where multiple outstanding events have been processed. And yet	519	in time where multiple outstanding events have been processed. And yet
323	another way to call them is transactions - each condition variable can be	520	another way to call them is transactions - each condition variable can be
324	used to represent a transaction, which finishes at some point and delivers	521	used to represent a transaction, which finishes at some point and delivers
325	a result.	522	a result. And yet some people know them as "futures" - a promise to
		523	compute/deliver something that you can wait for.
326		524
327	Condition variables are very useful to signal that something has finished,	525	Condition variables are very useful to signal that something has finished,
328	for example, if you write a module that does asynchronous http requests,	526	for example, if you write a module that does asynchronous http requests,
329	then a condition variable would be the ideal candidate to signal the	527	then a condition variable would be the ideal candidate to signal the
330	availability of results. The user can either act when the callback is	528	availability of results. The user can either act when the callback is
…		…
364	after => 1,	562	after => 1,
365	cb => sub { $result_ready->send },	563	cb => sub { $result_ready->send },
366	);	564	);
367		565
368	# this "blocks" (while handling events) till the callback	566	# this "blocks" (while handling events) till the callback
369	# calls send	567	# calls -<send
370	$result_ready->recv;	568	$result_ready->recv;
371		569
372	Example: wait for a timer, but take advantage of the fact that	570	Example: wait for a timer, but take advantage of the fact that condition
373	condition variables are also code references.	571	variables are also callable directly.
374		572
375	my $done = AnyEvent->condvar;	573	my $done = AnyEvent->condvar;
376	my $delay = AnyEvent->timer (after => 5, cb => $done);	574	my $delay = AnyEvent->timer (after => 5, cb => $done);
377	$done->recv;	575	$done->recv;
		576
		577	Example: Imagine an API that returns a condvar and doesn't support
		578	callbacks. This is how you make a synchronous call, for example from
		579	the main program:
		580
		581	use AnyEvent::CouchDB;
		582
		583	...
		584
		585	my @info = $couchdb->info->recv;
		586
		587	And this is how you would just set a callback to be called whenever the
		588	results are available:
		589
		590	$couchdb->info->cb (sub {
		591	my @info = $_[0]->recv;
		592	});
378		593
379	=head3 METHODS FOR PRODUCERS	594	=head3 METHODS FOR PRODUCERS
380		595
381	These methods should only be used by the producing side, i.e. the	596	These methods should only be used by the producing side, i.e. the
382	code/module that eventually sends the signal. Note that it is also	597	code/module that eventually sends the signal. Note that it is also
…		…
395	immediately from within send.	610	immediately from within send.
396		611
397	Any arguments passed to the C<send> call will be returned by all	612	Any arguments passed to the C<send> call will be returned by all
398	future C<< ->recv >> calls.	613	future C<< ->recv >> calls.
399		614
400	Condition variables are overloaded so one can call them directly	615	Condition variables are overloaded so one can call them directly (as if
401	(as a code reference). Calling them directly is the same as calling	616	they were a code reference). Calling them directly is the same as calling
402	C<send>. Note, however, that many C-based event loops do not handle	617	C<send>.
403	overloading, so as tempting as it may be, passing a condition variable
404	instead of a callback does not work. Both the pure perl and EV loops
405	support overloading, however, as well as all functions that use perl to
406	invoke a callback (as in L<AnyEvent::Socket> and L<AnyEvent::DNS> for
407	example).
408		618
409	=item $cv->croak ($error)	619	=item $cv->croak ($error)
410		620
411	Similar to send, but causes all call's to C<< ->recv >> to invoke	621	Similar to send, but causes all call's to C<< ->recv >> to invoke
412	C<Carp::croak> with the given error message/object/scalar.	622	C<Carp::croak> with the given error message/object/scalar.
413		623
414	This can be used to signal any errors to the condition variable	624	This can be used to signal any errors to the condition variable
415	user/consumer.	625	user/consumer. Doing it this way instead of calling C<croak> directly
		626	delays the error detetcion, but has the overwhelmign advantage that it
		627	diagnoses the error at the place where the result is expected, and not
		628	deep in some event clalback without connection to the actual code causing
		629	the problem.
416		630
417	=item $cv->begin ([group callback])	631	=item $cv->begin ([group callback])
418		632
419	=item $cv->end	633	=item $cv->end
420
421	These two methods are EXPERIMENTAL and MIGHT CHANGE.
422		634
423	These two methods can be used to combine many transactions/events into	635	These two methods can be used to combine many transactions/events into
424	one. For example, a function that pings many hosts in parallel might want	636	one. For example, a function that pings many hosts in parallel might want
425	to use a condition variable for the whole process.	637	to use a condition variable for the whole process.
426		638
…		…
428	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end	640	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
429	>>, the (last) callback passed to C<begin> will be executed. That callback	641	>>, the (last) callback passed to C<begin> will be executed. That callback
430	is I<supposed> to call C<< ->send >>, but that is not required. If no	642	is I<supposed> to call C<< ->send >>, but that is not required. If no
431	callback was set, C<send> will be called without any arguments.	643	callback was set, C<send> will be called without any arguments.
432		644
433	Let's clarify this with the ping example:	645	You can think of C<< $cv->send >> giving you an OR condition (one call
		646	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		647	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		648
		649	Let's start with a simple example: you have two I/O watchers (for example,
		650	STDOUT and STDERR for a program), and you want to wait for both streams to
		651	close before activating a condvar:
		652
		653	my $cv = AnyEvent->condvar;
		654
		655	$cv->begin; # first watcher
		656	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		657	defined sysread $fh1, my $buf, 4096
		658	or $cv->end;
		659	});
		660
		661	$cv->begin; # second watcher
		662	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		663	defined sysread $fh2, my $buf, 4096
		664	or $cv->end;
		665	});
		666
		667	$cv->recv;
		668
		669	This works because for every event source (EOF on file handle), there is
		670	one call to C<begin>, so the condvar waits for all calls to C<end> before
		671	sending.
		672
		673	The ping example mentioned above is slightly more complicated, as the
		674	there are results to be passwd back, and the number of tasks that are
		675	begung can potentially be zero:
434		676
435	my $cv = AnyEvent->condvar;	677	my $cv = AnyEvent->condvar;
436		678
437	my %result;	679	my %result;
438	$cv->begin (sub { $cv->send (\%result) });	680	$cv->begin (sub { $cv->send (\%result) });
…		…
458	loop, which serves two important purposes: first, it sets the callback	700	loop, which serves two important purposes: first, it sets the callback
459	to be called once the counter reaches C<0>, and second, it ensures that	701	to be called once the counter reaches C<0>, and second, it ensures that
460	C<send> is called even when C<no> hosts are being pinged (the loop	702	C<send> is called even when C<no> hosts are being pinged (the loop
461	doesn't execute once).	703	doesn't execute once).
462		704
463	This is the general pattern when you "fan out" into multiple subrequests:	705	This is the general pattern when you "fan out" into multiple (but
464	use an outer C<begin>/C<end> pair to set the callback and ensure C<end>	706	potentially none) subrequests: use an outer C<begin>/C<end> pair to set
465	is called at least once, and then, for each subrequest you start, call	707	the callback and ensure C<end> is called at least once, and then, for each
466	C<begin> and for each subrequest you finish, call C<end>.	708	subrequest you start, call C<begin> and for each subrequest you finish,
		709	call C<end>.
467		710
468	=back	711	=back
469		712
470	=head3 METHODS FOR CONSUMERS	713	=head3 METHODS FOR CONSUMERS
471		714
…		…
487	function will call C<croak>.	730	function will call C<croak>.
488		731
489	In list context, all parameters passed to C<send> will be returned,	732	In list context, all parameters passed to C<send> will be returned,
490	in scalar context only the first one will be returned.	733	in scalar context only the first one will be returned.
491		734
		735	Note that doing a blocking wait in a callback is not supported by any
		736	event loop, that is, recursive invocation of a blocking C<< ->recv
		737	>> is not allowed, and the C<recv> call will C<croak> if such a
		738	condition is detected. This condition can be slightly loosened by using
		739	L<Coro::AnyEvent>, which allows you to do a blocking C<< ->recv >> from
		740	any thread that doesn't run the event loop itself.
		741
492	Not all event models support a blocking wait - some die in that case	742	Not all event models support a blocking wait - some die in that case
493	(programs might want to do that to stay interactive), so I<if you are	743	(programs might want to do that to stay interactive), so I<if you are
494	using this from a module, never require a blocking wait>, but let the	744	using this from a module, never require a blocking wait>. Instead, let the
495	caller decide whether the call will block or not (for example, by coupling	745	caller decide whether the call will block or not (for example, by coupling
496	condition variables with some kind of request results and supporting	746	condition variables with some kind of request results and supporting
497	callbacks so the caller knows that getting the result will not block,	747	callbacks so the caller knows that getting the result will not block,
498	while still supporting blocking waits if the caller so desires).	748	while still supporting blocking waits if the caller so desires).
499		749
500	Another reason I<never> to C<< ->recv >> in a module is that you cannot
501	sensibly have two C<< ->recv >>'s in parallel, as that would require
502	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
503	can supply.
504
505	The L<Coro> module, however, I<can> and I<does> supply coroutines and, in
506	fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe
507	versions and also integrates coroutines into AnyEvent, making blocking
508	C<< ->recv >> calls perfectly safe as long as they are done from another
509	coroutine (one that doesn't run the event loop).
510
511	You can ensure that C<< -recv >> never blocks by setting a callback and	750	You can ensure that C<< -recv >> never blocks by setting a callback and
512	only calling C<< ->recv >> from within that callback (or at a later	751	only calling C<< ->recv >> from within that callback (or at a later
513	time). This will work even when the event loop does not support blocking	752	time). This will work even when the event loop does not support blocking
514	waits otherwise.	753	waits otherwise.
515		754
516	=item $bool = $cv->ready	755	=item $bool = $cv->ready
517		756
518	Returns true when the condition is "true", i.e. whether C<send> or	757	Returns true when the condition is "true", i.e. whether C<send> or
519	C<croak> have been called.	758	C<croak> have been called.
520		759
521	=item $cb = $cv->cb ([new callback])	760	=item $cb = $cv->cb ($cb->($cv))
522		761
523	This is a mutator function that returns the callback set and optionally	762	This is a mutator function that returns the callback set and optionally
524	replaces it before doing so.	763	replaces it before doing so.
525		764
526	The callback will be called when the condition becomes "true", i.e. when	765	The callback will be called when the condition becomes "true", i.e. when
527	C<send> or C<croak> are called. Calling C<recv> inside the callback	766	C<send> or C<croak> are called, with the only argument being the condition
528	or at any later time is guaranteed not to block.	767	variable itself. Calling C<recv> inside the callback or at any later time
		768	is guaranteed not to block.
529		769
530	=back	770	=back
531		771
		772	=head1 SUPPORTED EVENT LOOPS/BACKENDS
		773
		774	The available backend classes are (every class has its own manpage):
		775
		776	=over 4
		777
		778	=item Backends that are autoprobed when no other event loop can be found.
		779
		780	EV is the preferred backend when no other event loop seems to be in
		781	use. If EV is not installed, then AnyEvent will try Event, and, failing
		782	that, will fall back to its own pure-perl implementation, which is
		783	available everywhere as it comes with AnyEvent itself.
		784
		785	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		786	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		787	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
		788
		789	=item Backends that are transparently being picked up when they are used.
		790
		791	These will be used when they are currently loaded when the first watcher
		792	is created, in which case it is assumed that the application is using
		793	them. This means that AnyEvent will automatically pick the right backend
		794	when the main program loads an event module before anything starts to
		795	create watchers. Nothing special needs to be done by the main program.
		796
		797	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		798	AnyEvent::Impl::Tk based on Tk, very broken.
		799	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		800	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		801
		802	=item Backends with special needs.
		803
		804	Qt requires the Qt::Application to be instantiated first, but will
		805	otherwise be picked up automatically. As long as the main program
		806	instantiates the application before any AnyEvent watchers are created,
		807	everything should just work.
		808
		809	AnyEvent::Impl::Qt based on Qt.
		810
		811	Support for IO::Async can only be partial, as it is too broken and
		812	architecturally limited to even support the AnyEvent API. It also
		813	is the only event loop that needs the loop to be set explicitly, so
		814	it can only be used by a main program knowing about AnyEvent. See
		815	L<AnyEvent::Impl::Async> for the gory details.
		816
		817	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
		818
		819	=item Event loops that are indirectly supported via other backends.
		820
		821	Some event loops can be supported via other modules:
		822
		823	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		824
		825	B<WxWidgets> has no support for watching file handles. However, you can
		826	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		827	polls 20 times per second, which was considered to be too horrible to even
		828	consider for AnyEvent.
		829
		830	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		831	backend, so it can be supported through POE.
		832
		833	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		834	load L<POE> when detecting them, in the hope that POE will pick them up,
		835	in which case everything will be automatic.
		836
		837	=back
		838
532	=head1 GLOBAL VARIABLES AND FUNCTIONS	839	=head1 GLOBAL VARIABLES AND FUNCTIONS
533		840
		841	These are not normally required to use AnyEvent, but can be useful to
		842	write AnyEvent extension modules.
		843
534	=over 4	844	=over 4
535		845
536	=item $AnyEvent::MODEL	846	=item $AnyEvent::MODEL
537		847
538	Contains C<undef> until the first watcher is being created. Then it	848	Contains C<undef> until the first watcher is being created, before the
		849	backend has been autodetected.
		850
539	contains the event model that is being used, which is the name of the	851	Afterwards it contains the event model that is being used, which is the
540	Perl class implementing the model. This class is usually one of the	852	name of the Perl class implementing the model. This class is usually one
541	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	853	of the C<AnyEvent::Impl:xxx> modules, but can be any other class in the
542	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	854	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
543		855	will be C<urxvt::anyevent>).
544	The known classes so far are:
545
546	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
547	AnyEvent::Impl::Event based on Event, second best choice.
548	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
549	AnyEvent::Impl::Glib based on Glib, third-best choice.
550	AnyEvent::Impl::Tk based on Tk, very bad choice.
551	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
552	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
553	AnyEvent::Impl::POE based on POE, not generic enough for full support.
554
555	There is no support for WxWidgets, as WxWidgets has no support for
556	watching file handles. However, you can use WxWidgets through the
557	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
558	second, which was considered to be too horrible to even consider for
559	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
560	it's adaptor.
561
562	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
563	autodetecting them.
564		856
565	=item AnyEvent::detect	857	=item AnyEvent::detect
566		858
567	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	859	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
568	if necessary. You should only call this function right before you would	860	if necessary. You should only call this function right before you would
569	have created an AnyEvent watcher anyway, that is, as late as possible at	861	have created an AnyEvent watcher anyway, that is, as late as possible at
570	runtime.	862	runtime, and not e.g. while initialising of your module.
		863
		864	If you need to do some initialisation before AnyEvent watchers are
		865	created, use C<post_detect>.
571		866
572	=item $guard = AnyEvent::post_detect { BLOCK }	867	=item $guard = AnyEvent::post_detect { BLOCK }
573		868
574	Arranges for the code block to be executed as soon as the event model is	869	Arranges for the code block to be executed as soon as the event model is
575	autodetected (or immediately if this has already happened).	870	autodetected (or immediately if this has already happened).
		871
		872	The block will be executed I<after> the actual backend has been detected
		873	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		874	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		875	other initialisations - see the sources of L<AnyEvent::Strict> or
		876	L<AnyEvent::AIO> to see how this is used.
		877
		878	The most common usage is to create some global watchers, without forcing
		879	event module detection too early, for example, L<AnyEvent::AIO> creates
		880	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		881	avoid autodetecting the event module at load time.
576		882
577	If called in scalar or list context, then it creates and returns an object	883	If called in scalar or list context, then it creates and returns an object
578	that automatically removes the callback again when it is destroyed. See	884	that automatically removes the callback again when it is destroyed. See
579	L<Coro::BDB> for a case where this is useful.	885	L<Coro::BDB> for a case where this is useful.
580		886
…		…
583	If there are any code references in this array (you can C<push> to it	889	If there are any code references in this array (you can C<push> to it
584	before or after loading AnyEvent), then they will called directly after	890	before or after loading AnyEvent), then they will called directly after
585	the event loop has been chosen.	891	the event loop has been chosen.
586		892
587	You should check C<$AnyEvent::MODEL> before adding to this array, though:	893	You should check C<$AnyEvent::MODEL> before adding to this array, though:
588	if it contains a true value then the event loop has already been detected,	894	if it is defined then the event loop has already been detected, and the
589	and the array will be ignored.	895	array will be ignored.
590		896
591	Best use C<AnyEvent::post_detect { BLOCK }> instead.	897	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		898	it,as it takes care of these details.
		899
		900	This variable is mainly useful for modules that can do something useful
		901	when AnyEvent is used and thus want to know when it is initialised, but do
		902	not need to even load it by default. This array provides the means to hook
		903	into AnyEvent passively, without loading it.
592		904
593	=back	905	=back
594		906
595	=head1 WHAT TO DO IN A MODULE	907	=head1 WHAT TO DO IN A MODULE
596		908
…		…
651		963
652		964
653	=head1 OTHER MODULES	965	=head1 OTHER MODULES
654		966
655	The following is a non-exhaustive list of additional modules that use	967	The following is a non-exhaustive list of additional modules that use
656	AnyEvent and can therefore be mixed easily with other AnyEvent modules	968	AnyEvent as a client and can therefore be mixed easily with other AnyEvent
657	in the same program. Some of the modules come with AnyEvent, some are	969	modules and other event loops in the same program. Some of the modules
658	available via CPAN.	970	come with AnyEvent, most are available via CPAN.
659		971
660	=over 4	972	=over 4
661		973
662	=item L<AnyEvent::Util>	974	=item L<AnyEvent::Util>
663		975
664	Contains various utility functions that replace often-used but blocking	976	Contains various utility functions that replace often-used but blocking
665	functions such as C<inet_aton> by event-/callback-based versions.	977	functions such as C<inet_aton> by event-/callback-based versions.
666
667	=item L<AnyEvent::Handle>
668
669	Provide read and write buffers and manages watchers for reads and writes.
670		978
671	=item L<AnyEvent::Socket>	979	=item L<AnyEvent::Socket>
672		980
673	Provides various utility functions for (internet protocol) sockets,	981	Provides various utility functions for (internet protocol) sockets,
674	addresses and name resolution. Also functions to create non-blocking tcp	982	addresses and name resolution. Also functions to create non-blocking tcp
675	connections or tcp servers, with IPv6 and SRV record support and more.	983	connections or tcp servers, with IPv6 and SRV record support and more.
676		984
		985	=item L<AnyEvent::Handle>
		986
		987	Provide read and write buffers, manages watchers for reads and writes,
		988	supports raw and formatted I/O, I/O queued and fully transparent and
		989	non-blocking SSL/TLS (via L<AnyEvent::TLS>.
		990
677	=item L<AnyEvent::DNS>	991	=item L<AnyEvent::DNS>
678		992
679	Provides rich asynchronous DNS resolver capabilities.	993	Provides rich asynchronous DNS resolver capabilities.
680		994
		995	=item L<AnyEvent::HTTP>
		996
		997	A simple-to-use HTTP library that is capable of making a lot of concurrent
		998	HTTP requests.
		999
681	=item L<AnyEvent::HTTPD>	1000	=item L<AnyEvent::HTTPD>
682		1001
683	Provides a simple web application server framework.	1002	Provides a simple web application server framework.
684		1003
685	=item L<AnyEvent::FastPing>	1004	=item L<AnyEvent::FastPing>
686		1005
687	The fastest ping in the west.	1006	The fastest ping in the west.
688		1007
		1008	=item L<AnyEvent::DBI>
		1009
		1010	Executes L<DBI> requests asynchronously in a proxy process.
		1011
		1012	=item L<AnyEvent::AIO>
		1013
		1014	Truly asynchronous I/O, should be in the toolbox of every event
		1015	programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
		1016	together.
		1017
		1018	=item L<AnyEvent::BDB>
		1019
		1020	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
		1021	L<BDB> and AnyEvent together.
		1022
		1023	=item L<AnyEvent::GPSD>
		1024
		1025	A non-blocking interface to gpsd, a daemon delivering GPS information.
		1026
689	=item L<Net::IRC3>	1027	=item L<AnyEvent::IRC>
690		1028
691	AnyEvent based IRC client module family.	1029	AnyEvent based IRC client module family (replacing the older Net::IRC3).
692		1030
693	=item L<Net::XMPP2>	1031	=item L<AnyEvent::XMPP>
694		1032
695	AnyEvent based XMPP (Jabber protocol) module family.	1033	AnyEvent based XMPP (Jabber protocol) module family (replacing the older
		1034	Net::XMPP2>.
		1035
		1036	=item L<AnyEvent::IGS>
		1037
		1038	A non-blocking interface to the Internet Go Server protocol (used by
		1039	L<App::IGS>).
696		1040
697	=item L<Net::FCP>	1041	=item L<Net::FCP>
698		1042
699	AnyEvent-based implementation of the Freenet Client Protocol, birthplace	1043	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
700	of AnyEvent.	1044	of AnyEvent.
…		…
705		1049
706	=item L<Coro>	1050	=item L<Coro>
707		1051
708	Has special support for AnyEvent via L<Coro::AnyEvent>.	1052	Has special support for AnyEvent via L<Coro::AnyEvent>.
709		1053
710	=item L<AnyEvent::AIO>, L<IO::AIO>
711
712	Truly asynchronous I/O, should be in the toolbox of every event
713	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
714	together.
715
716	=item L<AnyEvent::BDB>, L<BDB>
717
718	Truly asynchronous Berkeley DB access. AnyEvent::AIO transparently fuses
719	IO::AIO and AnyEvent together.
720
721	=item L<IO::Lambda>
722
723	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
724
725	=back	1054	=back
726		1055
727	=cut	1056	=cut
728		1057
729	package AnyEvent;	1058	package AnyEvent;
730		1059
		1060	# basically a tuned-down version of common::sense
		1061	sub common_sense {
731	no warnings;	1062	# no warnings
732	use strict;	1063	${^WARNING_BITS} ^= ${^WARNING_BITS};
		1064	# use strict vars subs
		1065	$^H |= 0x00000600;
		1066	}
733		1067
		1068	BEGIN { AnyEvent::common_sense }
		1069
734	use Carp;	1070	use Carp ();
735		1071
736	our $VERSION = '4.03';	1072	our $VERSION = 4.85;
737	our $MODEL;	1073	our $MODEL;
738		1074
739	our $AUTOLOAD;	1075	our $AUTOLOAD;
740	our @ISA;	1076	our @ISA;
741		1077
742	our @REGISTRY;	1078	our @REGISTRY;
743		1079
		1080	our $WIN32;
		1081
		1082	our $VERBOSE;
		1083
		1084	BEGIN {
		1085	eval "sub WIN32(){ " . (($^O =~ /mswin32/i)*1) ." }";
		1086	eval "sub TAINT(){ " . (${^TAINT}*1) . " }";
		1087
		1088	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1089	if ${^TAINT};
		1090
744	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;	1091	$VERBOSE = $ENV{PERL_ANYEVENT_VERBOSE}*1;
		1092
		1093	}
		1094
		1095	our $MAX_SIGNAL_LATENCY = 10;
745		1096
746	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred	1097	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
747		1098
748	{	1099	{
749	my $idx;	1100	my $idx;
…		…
757	[Event:: => AnyEvent::Impl::Event::],	1108	[Event:: => AnyEvent::Impl::Event::],
758	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1109	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
759	# everything below here will not be autoprobed	1110	# everything below here will not be autoprobed
760	# as the pureperl backend should work everywhere	1111	# as the pureperl backend should work everywhere
761	# and is usually faster	1112	# and is usually faster
762	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
763	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers	1113	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers
764	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy	1114	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		1115	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
765	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program	1116	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
766	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza	1117	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
767	[Wx:: => AnyEvent::Impl::POE::],	1118	[Wx:: => AnyEvent::Impl::POE::],
768	[Prima:: => AnyEvent::Impl::POE::],	1119	[Prima:: => AnyEvent::Impl::POE::],
		1120	# IO::Async is just too broken - we would need workarounds for its
		1121	# byzantine signal and broken child handling, among others.
		1122	# IO::Async is rather hard to detect, as it doesn't have any
		1123	# obvious default class.
		1124	# [IO::Async:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1125	# [IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1126	# [IO::Async::Notifier:: => AnyEvent::Impl::IOAsync::], # requires special main program
769	);	1127	);
770		1128
771	our %method = map +($_ => 1), qw(io timer signal child condvar one_event DESTROY);	1129	our %method = map +($_ => 1),
		1130	qw(io timer time now now_update signal child idle condvar one_event DESTROY);
772		1131
773	our @post_detect;	1132	our @post_detect;
774		1133
775	sub post_detect(&) {	1134	sub post_detect(&) {
776	my ($cb) = @_;	1135	my ($cb) = @_;
…		…
781	1	1140	1
782	} else {	1141	} else {
783	push @post_detect, $cb;	1142	push @post_detect, $cb;
784		1143
785	defined wantarray	1144	defined wantarray
786	? bless \$cb, "AnyEvent::Util::PostDetect"	1145	? bless \$cb, "AnyEvent::Util::postdetect"
787	: ()	1146	: ()
788	}	1147	}
789	}	1148	}
790		1149
791	sub AnyEvent::Util::PostDetect::DESTROY {	1150	sub AnyEvent::Util::postdetect::DESTROY {
792	@post_detect = grep $_ != ${$_[0]}, @post_detect;	1151	@post_detect = grep $_ != ${$_[0]}, @post_detect;
793	}	1152	}
794		1153
795	sub detect() {	1154	sub detect() {
796	unless ($MODEL) {	1155	unless ($MODEL) {
797	no strict 'refs';
798	local $SIG{__DIE__};	1156	local $SIG{__DIE__};
799		1157
800	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	1158	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
801	my $model = "AnyEvent::Impl::$1";	1159	my $model = "AnyEvent::Impl::$1";
802	if (eval "require $model") {	1160	if (eval "require $model") {
803	$MODEL = $model;	1161	$MODEL = $model;
804	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	1162	warn "AnyEvent: loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.\n" if $VERBOSE >= 2;
805	} else {	1163	} else {
806	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;	1164	warn "AnyEvent: unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@" if $VERBOSE;
807	}	1165	}
808	}	1166	}
809		1167
810	# check for already loaded models	1168	# check for already loaded models
811	unless ($MODEL) {	1169	unless ($MODEL) {
812	for (@REGISTRY, @models) {	1170	for (@REGISTRY, @models) {
813	my ($package, $model) = @$_;	1171	my ($package, $model) = @$_;
814	if (${"$package\::VERSION"} > 0) {	1172	if (${"$package\::VERSION"} > 0) {
815	if (eval "require $model") {	1173	if (eval "require $model") {
816	$MODEL = $model;	1174	$MODEL = $model;
817	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;	1175	warn "AnyEvent: autodetected model '$model', using it.\n" if $VERBOSE >= 2;
818	last;	1176	last;
819	}	1177	}
820	}	1178	}
821	}	1179	}
822		1180
…		…
827	my ($package, $model) = @$_;	1185	my ($package, $model) = @$_;
828	if (eval "require $package"	1186	if (eval "require $package"
829	and ${"$package\::VERSION"} > 0	1187	and ${"$package\::VERSION"} > 0
830	and eval "require $model") {	1188	and eval "require $model") {
831	$MODEL = $model;	1189	$MODEL = $model;
832	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;	1190	warn "AnyEvent: autoprobed model '$model', using it.\n" if $VERBOSE >= 2;
833	last;	1191	last;
834	}	1192	}
835	}	1193	}
836		1194
837	$MODEL	1195	$MODEL
838	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.";	1196	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.\n";
839	}	1197	}
840	}	1198	}
841		1199
		1200	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		1201
842	unshift @ISA, $MODEL;	1202	unshift @ISA, $MODEL;
843	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	1203
		1204	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
844		1205
845	(shift @post_detect)->() while @post_detect;	1206	(shift @post_detect)->() while @post_detect;
846	}	1207	}
847		1208
848	$MODEL	1209	$MODEL
…		…
850		1211
851	sub AUTOLOAD {	1212	sub AUTOLOAD {
852	(my $func = $AUTOLOAD) =~ s/.*://;	1213	(my $func = $AUTOLOAD) =~ s/.*://;
853		1214
854	$method{$func}	1215	$method{$func}
855	or croak "$func: not a valid method for AnyEvent objects";	1216	or Carp::croak "$func: not a valid method for AnyEvent objects";
856		1217
857	detect unless $MODEL;	1218	detect unless $MODEL;
858		1219
859	my $class = shift;	1220	my $class = shift;
860	$class->$func (@_);	1221	$class->$func (@_);
861	}	1222	}
862		1223
		1224	# utility function to dup a filehandle. this is used by many backends
		1225	# to support binding more than one watcher per filehandle (they usually
		1226	# allow only one watcher per fd, so we dup it to get a different one).
		1227	sub _dupfh($$;$$) {
		1228	my ($poll, $fh, $r, $w) = @_;
		1229
		1230	# cygwin requires the fh mode to be matching, unix doesn't
		1231	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1232
		1233	open my $fh2, $mode, $fh
		1234	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1235
		1236	# we assume CLOEXEC is already set by perl in all important cases
		1237
		1238	($fh2, $rw)
		1239	}
		1240
863	package AnyEvent::Base;	1241	package AnyEvent::Base;
864		1242
		1243	# default implementations for many methods
		1244
		1245	sub _time {
		1246	# probe for availability of Time::HiRes
		1247	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1248	warn "AnyEvent: using Time::HiRes for sub-second timing accuracy.\n" if $VERBOSE >= 8;
		1249	*_time = \&Time::HiRes::time;
		1250	# if (eval "use POSIX (); (POSIX::times())...
		1251	} else {
		1252	warn "AnyEvent: using built-in time(), WARNING, no sub-second resolution!\n" if $VERBOSE;
		1253	*_time = sub { time }; # epic fail
		1254	}
		1255
		1256	&_time
		1257	}
		1258
		1259	sub time { _time }
		1260	sub now { _time }
		1261	sub now_update { }
		1262
865	# default implementation for ->condvar	1263	# default implementation for ->condvar
866		1264
867	sub condvar {	1265	sub condvar {
868	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, AnyEvent::CondVar::	1266	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
869	}	1267	}
870		1268
871	# default implementation for ->signal	1269	# default implementation for ->signal
872		1270
873	our %SIG_CB;	1271	our $HAVE_ASYNC_INTERRUPT;
		1272	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1273	our (%SIG_ASY, %SIG_ASY_W);
		1274	our ($SIG_COUNT, $SIG_TW);
874		1275
		1276	sub _signal_exec {
		1277	$HAVE_ASYNC_INTERRUPT
		1278	? $SIGPIPE_R->drain
		1279	: sysread $SIGPIPE_R, my $dummy, 9;
		1280
		1281	while (%SIG_EV) {
		1282	for (keys %SIG_EV) {
		1283	delete $SIG_EV{$_};
		1284	$_->() for values %{ $SIG_CB{$_} || {} };
		1285	}
		1286	}
		1287	}
		1288
		1289	# install a dumym wakeupw atcher to reduce signal catching latency
		1290	sub _sig_add() {
		1291	unless ($SIG_COUNT++) {
		1292	# try to align timer on a full-second boundary, if possible
		1293	my $NOW = AnyEvent->now;
		1294
		1295	$SIG_TW = AnyEvent->timer (
		1296	after => $MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1297	interval => $MAX_SIGNAL_LATENCY,
		1298	cb => sub { }, # just for the PERL_ASYNC_CHECK
		1299	);
		1300	}
		1301	}
		1302
		1303	sub _sig_del {
		1304	undef $SIG_TW
		1305	unless --$SIG_COUNT;
		1306	}
		1307
875	sub signal {	1308	sub _signal {
876	my (undef, %arg) = @_;	1309	my (undef, %arg) = @_;
877		1310
878	my $signal = uc $arg{signal}	1311	my $signal = uc $arg{signal}
879	or Carp::croak "required option 'signal' is missing";	1312	or Carp::croak "required option 'signal' is missing";
880		1313
881	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1314	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1315
		1316	if ($HAVE_ASYNC_INTERRUPT) {
		1317	# async::interrupt
		1318
		1319	$SIG_ASY{$signal} ||= do {
		1320	my $asy = new Async::Interrupt
		1321	cb => sub { undef $SIG_EV{$signal} },
		1322	signal => $signal,
		1323	pipe => [$SIGPIPE_R->filenos],
		1324	;
		1325	$asy->pipe_autodrain (0);
		1326
		1327	$asy
		1328	};
		1329
		1330	} else {
		1331	# pure perl
		1332
882	$SIG{$signal} ||= sub {	1333	$SIG{$signal} ||= sub {
883	$_->() for values %{ $SIG_CB{$signal} || {} };	1334	local $!;
		1335	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1336	undef $SIG_EV{$signal};
		1337	};
		1338
		1339	# can't do signal processing without introducing races in pure perl,
		1340	# so limit the signal latency.
		1341	_sig_add;
884	};	1342	}
885		1343
886	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1344	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
887	}	1345	}
888		1346
		1347	sub signal {
		1348	# probe for availability of Async::Interrupt
		1349	if (!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT} && eval "use Async::Interrupt 0.6 (); 1") {
		1350	warn "AnyEvent: using Async::Interrupt for race-free signal handling.\n" if $VERBOSE >= 8;
		1351
		1352	$HAVE_ASYNC_INTERRUPT = 1;
		1353	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1354	$SIG_IO = AnyEvent->io (fh => $SIGPIPE_R->fileno, poll => "r", cb => \&_signal_exec);
		1355
		1356	} else {
		1357	warn "AnyEvent: using emulated perl signal handling with latency timer.\n" if $VERBOSE >= 8;
		1358
		1359	require Fcntl;
		1360
		1361	if (AnyEvent::WIN32) {
		1362	require AnyEvent::Util;
		1363
		1364	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1365	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R) if $SIGPIPE_R;
		1366	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W) if $SIGPIPE_W; # just in case
		1367	} else {
		1368	pipe $SIGPIPE_R, $SIGPIPE_W;
		1369	fcntl $SIGPIPE_R, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_R;
		1370	fcntl $SIGPIPE_W, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_W; # just in case
		1371
		1372	# not strictly required, as $^F is normally 2, but let's make sure...
		1373	fcntl $SIGPIPE_R, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1374	fcntl $SIGPIPE_W, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1375	}
		1376
		1377	$SIGPIPE_R
		1378	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1379
		1380	$SIG_IO = AnyEvent->io (fh => $SIGPIPE_R, poll => "r", cb => \&_signal_exec);
		1381	}
		1382
		1383	*signal = \&_signal;
		1384	&signal
		1385	}
		1386
889	sub AnyEvent::Base::Signal::DESTROY {	1387	sub AnyEvent::Base::signal::DESTROY {
890	my ($signal, $cb) = @{$_[0]};	1388	my ($signal, $cb) = @{$_[0]};
891		1389
		1390	_sig_del;
		1391
892	delete $SIG_CB{$signal}{$cb};	1392	delete $SIG_CB{$signal}{$cb};
893		1393
894	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };	1394	$HAVE_ASYNC_INTERRUPT
		1395	? delete $SIG_ASY{$signal}
		1396	: # delete doesn't work with older perls - they then
		1397	# print weird messages, or just unconditionally exit
		1398	# instead of getting the default action.
		1399	undef $SIG{$signal}
		1400	unless keys %{ $SIG_CB{$signal} };
895	}	1401	}
896		1402
897	# default implementation for ->child	1403	# default implementation for ->child
898		1404
899	our %PID_CB;	1405	our %PID_CB;
900	our $CHLD_W;	1406	our $CHLD_W;
901	our $CHLD_DELAY_W;	1407	our $CHLD_DELAY_W;
902	our $PID_IDLE;
903	our $WNOHANG;	1408	our $WNOHANG;
904		1409
905	sub _child_wait {	1410	sub _sigchld {
906	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1411	while (0 < (my $pid = waitpid -1, $WNOHANG)) {
		1412	$_->($pid, $?)
907	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1413	for values %{ $PID_CB{$pid} || {} },
908	(values %{ $PID_CB{0} || {} });	1414	values %{ $PID_CB{0} || {} };
909	}	1415	}
910
911	undef $PID_IDLE;
912	}
913
914	sub _sigchld {
915	# make sure we deliver these changes "synchronous" with the event loop.
916	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {
917	undef $CHLD_DELAY_W;
918	&_child_wait;
919	});
920	}	1416	}
921		1417
922	sub child {	1418	sub child {
923	my (undef, %arg) = @_;	1419	my (undef, %arg) = @_;
924		1420
925	defined (my $pid = $arg{pid} + 0)	1421	defined (my $pid = $arg{pid} + 0)
926	or Carp::croak "required option 'pid' is missing";	1422	or Carp::croak "required option 'pid' is missing";
927		1423
928	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1424	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
929		1425
930	unless ($WNOHANG) {	1426	# WNOHANG is almost cetrainly 1 everywhere
		1427	$WNOHANG ||= $^O =~ /^(?:openbsd|netbsd|linux|freebsd|cygwin|MSWin32)$/
		1428	? 1
931	$WNOHANG = eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;	1429	: eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
932	}
933		1430
934	unless ($CHLD_W) {	1431	unless ($CHLD_W) {
935	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1432	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
936	# child could be a zombie already, so make at least one round	1433	# child could be a zombie already, so make at least one round
937	&_sigchld;	1434	&_sigchld;
938	}	1435	}
939		1436
940	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	1437	bless [$pid, $arg{cb}], "AnyEvent::Base::child"
941	}	1438	}
942		1439
943	sub AnyEvent::Base::Child::DESTROY {	1440	sub AnyEvent::Base::child::DESTROY {
944	my ($pid, $cb) = @{$_[0]};	1441	my ($pid, $cb) = @{$_[0]};
945		1442
946	delete $PID_CB{$pid}{$cb};	1443	delete $PID_CB{$pid}{$cb};
947	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1444	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
948		1445
949	undef $CHLD_W unless keys %PID_CB;	1446	undef $CHLD_W unless keys %PID_CB;
950	}	1447	}
951		1448
		1449	# idle emulation is done by simply using a timer, regardless
		1450	# of whether the process is idle or not, and not letting
		1451	# the callback use more than 50% of the time.
		1452	sub idle {
		1453	my (undef, %arg) = @_;
		1454
		1455	my ($cb, $w, $rcb) = $arg{cb};
		1456
		1457	$rcb = sub {
		1458	if ($cb) {
		1459	$w = _time;
		1460	&$cb;
		1461	$w = _time - $w;
		1462
		1463	# never use more then 50% of the time for the idle watcher,
		1464	# within some limits
		1465	$w = 0.0001 if $w < 0.0001;
		1466	$w = 5 if $w > 5;
		1467
		1468	$w = AnyEvent->timer (after => $w, cb => $rcb);
		1469	} else {
		1470	# clean up...
		1471	undef $w;
		1472	undef $rcb;
		1473	}
		1474	};
		1475
		1476	$w = AnyEvent->timer (after => 0.05, cb => $rcb);
		1477
		1478	bless \\$cb, "AnyEvent::Base::idle"
		1479	}
		1480
		1481	sub AnyEvent::Base::idle::DESTROY {
		1482	undef $${$_[0]};
		1483	}
		1484
952	package AnyEvent::CondVar;	1485	package AnyEvent::CondVar;
953		1486
954	our @ISA = AnyEvent::CondVar::Base::;	1487	our @ISA = AnyEvent::CondVar::Base::;
955		1488
956	package AnyEvent::CondVar::Base;	1489	package AnyEvent::CondVar::Base;
957		1490
958	use overload	1491	#use overload
959	'&{}' => sub { my $self = shift; sub { $self->send (@_) } },	1492	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
960	fallback => 1;	1493	# fallback => 1;
		1494
		1495	# save 300+ kilobytes by dirtily hardcoding overloading
		1496	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1497	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1498	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1499	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1500
		1501	our $WAITING;
961		1502
962	sub _send {	1503	sub _send {
963	# nop	1504	# nop
964	}	1505	}
965		1506
…		…
978	sub ready {	1519	sub ready {
979	$_[0]{_ae_sent}	1520	$_[0]{_ae_sent}
980	}	1521	}
981		1522
982	sub _wait {	1523	sub _wait {
		1524	$WAITING
		1525	and !$_[0]{_ae_sent}
		1526	and Carp::croak "AnyEvent::CondVar: recursive blocking wait detected";
		1527
		1528	local $WAITING = 1;
983	AnyEvent->one_event while !$_[0]{_ae_sent};	1529	AnyEvent->one_event while !$_[0]{_ae_sent};
984	}	1530	}
985		1531
986	sub recv {	1532	sub recv {
987	$_[0]->_wait;	1533	$_[0]->_wait;
…		…
1006	}	1552	}
1007		1553
1008	# undocumented/compatibility with pre-3.4	1554	# undocumented/compatibility with pre-3.4
1009	*broadcast = \&send;	1555	*broadcast = \&send;
1010	*wait = \&_wait;	1556	*wait = \&_wait;
		1557
		1558	=head1 ERROR AND EXCEPTION HANDLING
		1559
		1560	In general, AnyEvent does not do any error handling - it relies on the
		1561	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1562	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1563	checking of all AnyEvent methods, however, which is highly useful during
		1564	development.
		1565
		1566	As for exception handling (i.e. runtime errors and exceptions thrown while
		1567	executing a callback), this is not only highly event-loop specific, but
		1568	also not in any way wrapped by this module, as this is the job of the main
		1569	program.
		1570
		1571	The pure perl event loop simply re-throws the exception (usually
		1572	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1573	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1574	so on.
		1575
		1576	=head1 ENVIRONMENT VARIABLES
		1577
		1578	The following environment variables are used by this module or its
		1579	submodules.
		1580
		1581	Note that AnyEvent will remove I<all> environment variables starting with
		1582	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		1583	enabled.
		1584
		1585	=over 4
		1586
		1587	=item C<PERL_ANYEVENT_VERBOSE>
		1588
		1589	By default, AnyEvent will be completely silent except in fatal
		1590	conditions. You can set this environment variable to make AnyEvent more
		1591	talkative.
		1592
		1593	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1594	conditions, such as not being able to load the event model specified by
		1595	C<PERL_ANYEVENT_MODEL>.
		1596
		1597	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1598	model it chooses.
		1599
		1600	When set to C<8> or higher, then AnyEvent will report extra information on
		1601	which optional modules it loads and how it implements certain features.
		1602
		1603	=item C<PERL_ANYEVENT_STRICT>
		1604
		1605	AnyEvent does not do much argument checking by default, as thorough
		1606	argument checking is very costly. Setting this variable to a true value
		1607	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1608	check the arguments passed to most method calls. If it finds any problems,
		1609	it will croak.
		1610
		1611	In other words, enables "strict" mode.
		1612
		1613	Unlike C<use strict> (or it's modern cousin, C<< use L<common::sense>
		1614	>>, it is definitely recommended to keep it off in production. Keeping
		1615	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		1616	can be very useful, however.
		1617
		1618	=item C<PERL_ANYEVENT_MODEL>
		1619
		1620	This can be used to specify the event model to be used by AnyEvent, before
		1621	auto detection and -probing kicks in. It must be a string consisting
		1622	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1623	and the resulting module name is loaded and if the load was successful,
		1624	used as event model. If it fails to load AnyEvent will proceed with
		1625	auto detection and -probing.
		1626
		1627	This functionality might change in future versions.
		1628
		1629	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1630	could start your program like this:
		1631
		1632	PERL_ANYEVENT_MODEL=Perl perl ...
		1633
		1634	=item C<PERL_ANYEVENT_PROTOCOLS>
		1635
		1636	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1637	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1638	of auto probing).
		1639
		1640	Must be set to a comma-separated list of protocols or address families,
		1641	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1642	used, and preference will be given to protocols mentioned earlier in the
		1643	list.
		1644
		1645	This variable can effectively be used for denial-of-service attacks
		1646	against local programs (e.g. when setuid), although the impact is likely
		1647	small, as the program has to handle conenction and other failures anyways.
		1648
		1649	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1650	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1651	- only support IPv4, never try to resolve or contact IPv6
		1652	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1653	IPv6, but prefer IPv6 over IPv4.
		1654
		1655	=item C<PERL_ANYEVENT_EDNS0>
		1656
		1657	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1658	for DNS. This extension is generally useful to reduce DNS traffic, but
		1659	some (broken) firewalls drop such DNS packets, which is why it is off by
		1660	default.
		1661
		1662	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1663	EDNS0 in its DNS requests.
		1664
		1665	=item C<PERL_ANYEVENT_MAX_FORKS>
		1666
		1667	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1668	will create in parallel.
		1669
		1670	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		1671
		1672	The default value for the C<max_outstanding> parameter for the default DNS
		1673	resolver - this is the maximum number of parallel DNS requests that are
		1674	sent to the DNS server.
		1675
		1676	=item C<PERL_ANYEVENT_RESOLV_CONF>
		1677
		1678	The file to use instead of F</etc/resolv.conf> (or OS-specific
		1679	configuration) in the default resolver. When set to the empty string, no
		1680	default config will be used.
		1681
		1682	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		1683
		1684	When neither C<ca_file> nor C<ca_path> was specified during
		1685	L<AnyEvent::TLS> context creation, and either of these environment
		1686	variables exist, they will be used to specify CA certificate locations
		1687	instead of a system-dependent default.
		1688
		1689	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		1690
		1691	When these are set to C<1>, then the respective modules are not
		1692	loaded. Mostly good for testing AnyEvent itself.
		1693
		1694	=back
1011		1695
1012	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1696	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
1013		1697
1014	This is an advanced topic that you do not normally need to use AnyEvent in	1698	This is an advanced topic that you do not normally need to use AnyEvent in
1015	a module. This section is only of use to event loop authors who want to	1699	a module. This section is only of use to event loop authors who want to
…		…
1049		1733
1050	I<rxvt-unicode> also cheats a bit by not providing blocking access to	1734	I<rxvt-unicode> also cheats a bit by not providing blocking access to
1051	condition variables: code blocking while waiting for a condition will	1735	condition variables: code blocking while waiting for a condition will
1052	C<die>. This still works with most modules/usages, and blocking calls must	1736	C<die>. This still works with most modules/usages, and blocking calls must
1053	not be done in an interactive application, so it makes sense.	1737	not be done in an interactive application, so it makes sense.
1054
1055	=head1 ENVIRONMENT VARIABLES
1056
1057	The following environment variables are used by this module:
1058
1059	=over 4
1060
1061	=item C<PERL_ANYEVENT_VERBOSE>
1062
1063	By default, AnyEvent will be completely silent except in fatal
1064	conditions. You can set this environment variable to make AnyEvent more
1065	talkative.
1066
1067	When set to C<1> or higher, causes AnyEvent to warn about unexpected
1068	conditions, such as not being able to load the event model specified by
1069	C<PERL_ANYEVENT_MODEL>.
1070
1071	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
1072	model it chooses.
1073
1074	=item C<PERL_ANYEVENT_MODEL>
1075
1076	This can be used to specify the event model to be used by AnyEvent, before
1077	auto detection and -probing kicks in. It must be a string consisting
1078	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
1079	and the resulting module name is loaded and if the load was successful,
1080	used as event model. If it fails to load AnyEvent will proceed with
1081	auto detection and -probing.
1082
1083	This functionality might change in future versions.
1084
1085	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
1086	could start your program like this:
1087
1088	PERL_ANYEVENT_MODEL=Perl perl ...
1089
1090	=item C<PERL_ANYEVENT_PROTOCOLS>
1091
1092	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
1093	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
1094	of auto probing).
1095
1096	Must be set to a comma-separated list of protocols or address families,
1097	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
1098	used, and preference will be given to protocols mentioned earlier in the
1099	list.
1100
1101	This variable can effectively be used for denial-of-service attacks
1102	against local programs (e.g. when setuid), although the impact is likely
1103	small, as the program has to handle connection errors already-
1104
1105	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
1106	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
1107	- only support IPv4, never try to resolve or contact IPv6
1108	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
1109	IPv6, but prefer IPv6 over IPv4.
1110
1111	=item C<PERL_ANYEVENT_EDNS0>
1112
1113	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
1114	for DNS. This extension is generally useful to reduce DNS traffic, but
1115	some (broken) firewalls drop such DNS packets, which is why it is off by
1116	default.
1117
1118	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
1119	EDNS0 in its DNS requests.
1120
1121	=back
1122		1738
1123	=head1 EXAMPLE PROGRAM	1739	=head1 EXAMPLE PROGRAM
1124		1740
1125	The following program uses an I/O watcher to read data from STDIN, a timer	1741	The following program uses an I/O watcher to read data from STDIN, a timer
1126	to display a message once per second, and a condition variable to quit the	1742	to display a message once per second, and a condition variable to quit the
…		…
1320	watcher.	1936	watcher.
1321		1937
1322	=head3 Results	1938	=head3 Results
1323		1939
1324	name watchers bytes create invoke destroy comment	1940	name watchers bytes create invoke destroy comment
1325	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	1941	EV/EV 400000 224 0.47 0.35 0.27 EV native interface
1326	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	1942	EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers
1327	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	1943	CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal
1328	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	1944	Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation
1329	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	1945	Event/Event 16000 517 32.20 31.80 0.81 Event native interface
1330	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers	1946	Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers
		1947	IOAsync/Any 16000 989 38.10 32.77 11.13 via IO::Async::Loop::IO_Poll
		1948	IOAsync/Any 16000 990 37.59 29.50 10.61 via IO::Async::Loop::Epoll
1331	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	1949	Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour
1332	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	1950	Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers
1333	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	1951	POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event
1334	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	1952	POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select
1335		1953
1336	=head3 Discussion	1954	=head3 Discussion
1337		1955
1338	The benchmark does I<not> measure scalability of the event loop very	1956	The benchmark does I<not> measure scalability of the event loop very
1339	well. For example, a select-based event loop (such as the pure perl one)	1957	well. For example, a select-based event loop (such as the pure perl one)
…		…
1364	performance becomes really bad with lots of file descriptors (and few of	1982	performance becomes really bad with lots of file descriptors (and few of
1365	them active), of course, but this was not subject of this benchmark.	1983	them active), of course, but this was not subject of this benchmark.
1366		1984
1367	The C<Event> module has a relatively high setup and callback invocation	1985	The C<Event> module has a relatively high setup and callback invocation
1368	cost, but overall scores in on the third place.	1986	cost, but overall scores in on the third place.
		1987
		1988	C<IO::Async> performs admirably well, about on par with C<Event>, even
		1989	when using its pure perl backend.
1369		1990
1370	C<Glib>'s memory usage is quite a bit higher, but it features a	1991	C<Glib>'s memory usage is quite a bit higher, but it features a
1371	faster callback invocation and overall ends up in the same class as	1992	faster callback invocation and overall ends up in the same class as
1372	C<Event>. However, Glib scales extremely badly, doubling the number of	1993	C<Event>. However, Glib scales extremely badly, doubling the number of
1373	watchers increases the processing time by more than a factor of four,	1994	watchers increases the processing time by more than a factor of four,
…		…
1451	it to another server. This includes deleting the old timeout and creating	2072	it to another server. This includes deleting the old timeout and creating
1452	a new one that moves the timeout into the future.	2073	a new one that moves the timeout into the future.
1453		2074
1454	=head3 Results	2075	=head3 Results
1455		2076
1456	name sockets create request	2077	name sockets create request
1457	EV 20000 69.01 11.16	2078	EV 20000 69.01 11.16
1458	Perl 20000 73.32 35.87	2079	Perl 20000 73.32 35.87
		2080	IOAsync 20000 157.00 98.14 epoll
		2081	IOAsync 20000 159.31 616.06 poll
1459	Event 20000 212.62 257.32	2082	Event 20000 212.62 257.32
1460	Glib 20000 651.16 1896.30	2083	Glib 20000 651.16 1896.30
1461	POE 20000 349.67 12317.24 uses POE::Loop::Event	2084	POE 20000 349.67 12317.24 uses POE::Loop::Event
1462		2085
1463	=head3 Discussion	2086	=head3 Discussion
1464		2087
1465	This benchmark I<does> measure scalability and overall performance of the	2088	This benchmark I<does> measure scalability and overall performance of the
1466	particular event loop.	2089	particular event loop.
…		…
1468	EV is again fastest. Since it is using epoll on my system, the setup time	2091	EV is again fastest. Since it is using epoll on my system, the setup time
1469	is relatively high, though.	2092	is relatively high, though.
1470		2093
1471	Perl surprisingly comes second. It is much faster than the C-based event	2094	Perl surprisingly comes second. It is much faster than the C-based event
1472	loops Event and Glib.	2095	loops Event and Glib.
		2096
		2097	IO::Async performs very well when using its epoll backend, and still quite
		2098	good compared to Glib when using its pure perl backend.
1473		2099
1474	Event suffers from high setup time as well (look at its code and you will	2100	Event suffers from high setup time as well (look at its code and you will
1475	understand why). Callback invocation also has a high overhead compared to	2101	understand why). Callback invocation also has a high overhead compared to
1476	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event	2102	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
1477	uses select or poll in basically all documented configurations.	2103	uses select or poll in basically all documented configurations.
…		…
1540	=item * C-based event loops perform very well with small number of	2166	=item * C-based event loops perform very well with small number of
1541	watchers, as the management overhead dominates.	2167	watchers, as the management overhead dominates.
1542		2168
1543	=back	2169	=back
1544		2170
		2171	=head2 THE IO::Lambda BENCHMARK
		2172
		2173	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2174	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2175	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2176	shouldn't come as a surprise to anybody). As such, the benchmark is
		2177	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2178	very optimal. But how would AnyEvent compare when used without the extra
		2179	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2180
		2181	The benchmark itself creates an echo-server, and then, for 500 times,
		2182	connects to the echo server, sends a line, waits for the reply, and then
		2183	creates the next connection. This is a rather bad benchmark, as it doesn't
		2184	test the efficiency of the framework or much non-blocking I/O, but it is a
		2185	benchmark nevertheless.
		2186
		2187	name runtime
		2188	Lambda/select 0.330 sec
		2189	+ optimized 0.122 sec
		2190	Lambda/AnyEvent 0.327 sec
		2191	+ optimized 0.138 sec
		2192	Raw sockets/select 0.077 sec
		2193	POE/select, components 0.662 sec
		2194	POE/select, raw sockets 0.226 sec
		2195	POE/select, optimized 0.404 sec
		2196
		2197	AnyEvent/select/nb 0.085 sec
		2198	AnyEvent/EV/nb 0.068 sec
		2199	+state machine 0.134 sec
		2200
		2201	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2202	benchmarks actually make blocking connects and use 100% blocking I/O,
		2203	defeating the purpose of an event-based solution. All of the newly
		2204	written AnyEvent benchmarks use 100% non-blocking connects (using
		2205	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2206	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2207	generally require a lot more bookkeeping and event handling than blocking
		2208	connects (which involve a single syscall only).
		2209
		2210	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2211	offers similar expressive power as POE and IO::Lambda, using conventional
		2212	Perl syntax. This means that both the echo server and the client are 100%
		2213	non-blocking, further placing it at a disadvantage.
		2214
		2215	As you can see, the AnyEvent + EV combination even beats the
		2216	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2217	backend easily beats IO::Lambda and POE.
		2218
		2219	And even the 100% non-blocking version written using the high-level (and
		2220	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda by a
		2221	large margin, even though it does all of DNS, tcp-connect and socket I/O
		2222	in a non-blocking way.
		2223
		2224	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2225	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2226	part of the IO::lambda distribution and were used without any changes.
		2227
		2228
		2229	=head1 SIGNALS
		2230
		2231	AnyEvent currently installs handlers for these signals:
		2232
		2233	=over 4
		2234
		2235	=item SIGCHLD
		2236
		2237	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2238	emulation for event loops that do not support them natively. Also, some
		2239	event loops install a similar handler.
		2240
		2241	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2242	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2243
		2244	=item SIGPIPE
		2245
		2246	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2247	when AnyEvent gets loaded.
		2248
		2249	The rationale for this is that AnyEvent users usually do not really depend
		2250	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2251	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2252	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2253	some random socket.
		2254
		2255	The rationale for installing a no-op handler as opposed to ignoring it is
		2256	that this way, the handler will be restored to defaults on exec.
		2257
		2258	Feel free to install your own handler, or reset it to defaults.
		2259
		2260	=back
		2261
		2262	=cut
		2263
		2264	undef $SIG{CHLD}
		2265	if $SIG{CHLD} eq 'IGNORE';
		2266
		2267	$SIG{PIPE} = sub { }
		2268	unless defined $SIG{PIPE};
		2269
		2270	=head1 RECOMMENDED/OPTIONAL MODULES
		2271
		2272	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2273	it's built-in modules) are required to use it.
		2274
		2275	That does not mean that AnyEvent won't take advantage of some additional
		2276	modules if they are installed.
		2277
		2278	This section epxlains which additional modules will be used, and how they
		2279	affect AnyEvent's operetion.
		2280
		2281	=over 4
		2282
		2283	=item L<Async::Interrupt>
		2284
		2285	This slightly arcane module is used to implement fast signal handling: To
		2286	my knowledge, there is no way to do completely race-free and quick
		2287	signal handling in pure perl. To ensure that signals still get
		2288	delivered, AnyEvent will start an interval timer to wake up perl (and
		2289	catch the signals) with some delay (default is 10 seconds, look for
		2290	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2291
		2292	If this module is available, then it will be used to implement signal
		2293	catching, which means that signals will not be delayed, and the event loop
		2294	will not be interrupted regularly, which is more efficient (And good for
		2295	battery life on laptops).
		2296
		2297	This affects not just the pure-perl event loop, but also other event loops
		2298	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2299
		2300	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2301	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2302	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2303	does nothing for those backends.
		2304
		2305	=item L<EV>
		2306
		2307	This module isn't really "optional", as it is simply one of the backend
		2308	event loops that AnyEvent can use. However, it is simply the best event
		2309	loop available in terms of features, speed and stability: It supports
		2310	the AnyEvent API optimally, implements all the watcher types in XS, does
		2311	automatic timer adjustments even when no monotonic clock is available,
		2312	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2313	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2314	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2315
		2316	=item L<Guard>
		2317
		2318	The guard module, when used, will be used to implement
		2319	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2320	lot less memory), but otherwise doesn't affect guard operation much. It is
		2321	purely used for performance.
		2322
		2323	=item L<JSON> and L<JSON::XS>
		2324
		2325	This module is required when you want to read or write JSON data via
		2326	L<AnyEvent::Handle>. It is also written in pure-perl, but can take
		2327	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2328
		2329	In fact, L<AnyEvent::Handle> will use L<JSON::XS> by default if it is
		2330	installed.
		2331
		2332	=item L<Net::SSLeay>
		2333
		2334	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2335	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2336	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2337
		2338	=item L<Time::HiRes>
		2339
		2340	This module is part of perl since release 5.008. It will be used when the
		2341	chosen event library does not come with a timing source on it's own. The
		2342	pure-perl event loop (L<AnyEvent::Impl::Perl>) will additionally use it to
		2343	try to use a monotonic clock for timing stability.
		2344
		2345	=back
		2346
1545		2347
1546	=head1 FORK	2348	=head1 FORK
1547		2349
1548	Most event libraries are not fork-safe. The ones who are usually are	2350	Most event libraries are not fork-safe. The ones who are usually are
1549	because they rely on inefficient but fork-safe C<select> or C<poll>	2351	because they rely on inefficient but fork-safe C<select> or C<poll>
1550	calls. Only L<EV> is fully fork-aware.	2352	calls. Only L<EV> is fully fork-aware.
1551		2353
1552	If you have to fork, you must either do so I<before> creating your first	2354	If you have to fork, you must either do so I<before> creating your first
1553	watcher OR you must not use AnyEvent at all in the child.	2355	watcher OR you must not use AnyEvent at all in the child OR you must do
		2356	something completely out of the scope of AnyEvent.
1554		2357
1555		2358
1556	=head1 SECURITY CONSIDERATIONS	2359	=head1 SECURITY CONSIDERATIONS
1557		2360
1558	AnyEvent can be forced to load any event model via	2361	AnyEvent can be forced to load any event model via
…		…
1563	specified in the variable.	2366	specified in the variable.
1564		2367
1565	You can make AnyEvent completely ignore this variable by deleting it	2368	You can make AnyEvent completely ignore this variable by deleting it
1566	before the first watcher gets created, e.g. with a C<BEGIN> block:	2369	before the first watcher gets created, e.g. with a C<BEGIN> block:
1567		2370
1568	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	2371	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1569		2372
1570	use AnyEvent;	2373	use AnyEvent;
1571		2374
1572	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can	2375	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1573	be used to probe what backend is used and gain other information (which is	2376	be used to probe what backend is used and gain other information (which is
1574	probably even less useful to an attacker than PERL_ANYEVENT_MODEL).	2377	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2378	$ENV{PERL_ANYEVENT_STRICT}.
		2379
		2380	Note that AnyEvent will remove I<all> environment variables starting with
		2381	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2382	enabled.
		2383
		2384
		2385	=head1 BUGS
		2386
		2387	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2388	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2389	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2390	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2391	pronounced).
1575		2392
1576		2393
1577	=head1 SEE ALSO	2394	=head1 SEE ALSO
1578		2395
1579	Utility functions: L<AnyEvent::Util>.	2396	Utility functions: L<AnyEvent::Util>.
…		…
1582	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.	2399	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
1583		2400
1584	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,	2401	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
1585	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,	2402	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
1586	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,	2403	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1587	L<AnyEvent::Impl::POE>.	2404	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>.
1588		2405
1589	Non-blocking file handles, sockets, TCP clients and	2406	Non-blocking file handles, sockets, TCP clients and
1590	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>.	2407	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
1591		2408
1592	Asynchronous DNS: L<AnyEvent::DNS>.	2409	Asynchronous DNS: L<AnyEvent::DNS>.
1593		2410
1594	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,	2411	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>,
		2412	L<Coro::Event>,
1595		2413
1596	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>, L<AnyEvent::DNS>.	2414	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::XMPP>,
		2415	L<AnyEvent::HTTP>.
1597		2416
1598		2417
1599	=head1 AUTHOR	2418	=head1 AUTHOR
1600		2419
1601	Marc Lehmann <schmorp@schmorp.de>	2420	Marc Lehmann <schmorp@schmorp.de>
1602	http://home.schmorp.de/	2421	http://home.schmorp.de/
1603		2422
1604	=cut	2423	=cut
1605		2424
1606	1	2425	1
1607		2426

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