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Revision 1.112 by root, Sat May 10 01:04:42 2008 UTC vs.
Revision 1.273 by root, Thu Aug 6 13:45:04 2009 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent - provide framework for multiple event loops	3	AnyEvent - the DBI of event loop programming
4		4
5	EV, Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event loops	5	EV, Event, Glib, Tk, Perl, Event::Lib, Irssi, rxvt-unicode, IO::Async, Qt
		6	and POE are various supported event loops/environments.
6		7
7	=head1 SYNOPSIS	8	=head1 SYNOPSIS
8		9
9	use AnyEvent;	10	use AnyEvent;
10		11
		12	# file descriptor readable
11	my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub {	13	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
		14
		15	# one-shot or repeating timers
		16	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
		17	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...
		18
		19	print AnyEvent->now; # prints current event loop time
		20	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
		21
		22	# POSIX signal
		23	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
		24
		25	# child process exit
		26	my $w = AnyEvent->child (pid => $pid, cb => sub {
		27	my ($pid, $status) = @_;
12	...	28	...
13	});	29	});
14		30
15	my $w = AnyEvent->timer (after => $seconds, cb => sub {	31	# called when event loop idle (if applicable)
16	...	32	my $w = AnyEvent->idle (cb => sub { ... });
17	});
18		33
19	my $w = AnyEvent->condvar; # stores whether a condition was flagged	34	my $w = AnyEvent->condvar; # stores whether a condition was flagged
		35	$w->send; # wake up current and all future recv's
20	$w->wait; # enters "main loop" till $condvar gets ->send	36	$w->recv; # enters "main loop" till $condvar gets ->send
21	$w->send; # wake up current and all future wait's	37	# use a condvar in callback mode:
		38	$w->cb (sub { $_[0]->recv });
		39
		40	=head1 INTRODUCTION/TUTORIAL
		41
		42	This manpage is mainly a reference manual. If you are interested
		43	in a tutorial or some gentle introduction, have a look at the
		44	L<AnyEvent::Intro> manpage.
		45
		46	=head1 SUPPORT
		47
		48	There is a mailinglist for discussing all things AnyEvent, and an IRC
		49	channel, too.
		50
		51	See the AnyEvent project page at the B<Schmorpforge Ta-Sa Software
		52	Repository>, at L<http://anyevent.schmorp.de>, for more info.
22		53
23	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)	54	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
24		55
25	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	56	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
26	nowadays. So what is different about AnyEvent?	57	nowadays. So what is different about AnyEvent?
27		58
28	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of	59	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
29	policy> and AnyEvent is I<small and efficient>.	60	policy> and AnyEvent is I<small and efficient>.
30		61
31	First and foremost, I<AnyEvent is not an event model> itself, it only	62	First and foremost, I<AnyEvent is not an event model> itself, it only
32	interfaces to whatever event model the main program happens to use in a	63	interfaces to whatever event model the main program happens to use, in a
33	pragmatic way. For event models and certain classes of immortals alike,	64	pragmatic way. For event models and certain classes of immortals alike,
34	the statement "there can only be one" is a bitter reality: In general,	65	the statement "there can only be one" is a bitter reality: In general,
35	only one event loop can be active at the same time in a process. AnyEvent	66	only one event loop can be active at the same time in a process. AnyEvent
36	helps hiding the differences between those event loops.	67	cannot change this, but it can hide the differences between those event
		68	loops.
37		69
38	The goal of AnyEvent is to offer module authors the ability to do event	70	The goal of AnyEvent is to offer module authors the ability to do event
39	programming (waiting for I/O or timer events) without subscribing to a	71	programming (waiting for I/O or timer events) without subscribing to a
40	religion, a way of living, and most importantly: without forcing your	72	religion, a way of living, and most importantly: without forcing your
41	module users into the same thing by forcing them to use the same event	73	module users into the same thing by forcing them to use the same event
42	model you use.	74	model you use.
43		75
44	For modules like POE or IO::Async (which is a total misnomer as it is	76	For modules like POE or IO::Async (which is a total misnomer as it is
45	actually doing all I/O I<synchronously>...), using them in your module is	77	actually doing all I/O I<synchronously>...), using them in your module is
46	like joining a cult: After you joined, you are dependent on them and you	78	like joining a cult: After you joined, you are dependent on them and you
47	cannot use anything else, as it is simply incompatible to everything that	79	cannot use anything else, as they are simply incompatible to everything
48	isn't itself. What's worse, all the potential users of your module are	80	that isn't them. What's worse, all the potential users of your
49	I<also> forced to use the same event loop you use.	81	module are I<also> forced to use the same event loop you use.
50		82
51	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	83	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
52	fine. AnyEvent + Tk works fine etc. etc. but none of these work together	84	fine. AnyEvent + Tk works fine etc. etc. but none of these work together
53	with the rest: POE + IO::Async? no go. Tk + Event? no go. Again: if	85	with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if
54	your module uses one of those, every user of your module has to use it,	86	your module uses one of those, every user of your module has to use it,
55	too. But if your module uses AnyEvent, it works transparently with all	87	too. But if your module uses AnyEvent, it works transparently with all
56	event models it supports (including stuff like POE and IO::Async, as long	88	event models it supports (including stuff like IO::Async, as long as those
57	as those use one of the supported event loops. It is trivial to add new	89	use one of the supported event loops. It is trivial to add new event loops
58	event loops to AnyEvent, too, so it is future-proof).	90	to AnyEvent, too, so it is future-proof).
59		91
60	In addition to being free of having to use I<the one and only true event	92	In addition to being free of having to use I<the one and only true event
61	model>, AnyEvent also is free of bloat and policy: with POE or similar	93	model>, AnyEvent also is free of bloat and policy: with POE or similar
62	modules, you get an enourmous amount of code and strict rules you have to	94	modules, you get an enormous amount of code and strict rules you have to
63	follow. AnyEvent, on the other hand, is lean and up to the point, by only	95	follow. AnyEvent, on the other hand, is lean and up to the point, by only
64	offering the functionality that is necessary, in as thin as a wrapper as	96	offering the functionality that is necessary, in as thin as a wrapper as
65	technically possible.	97	technically possible.
66		98
		99	Of course, AnyEvent comes with a big (and fully optional!) toolbox
		100	of useful functionality, such as an asynchronous DNS resolver, 100%
		101	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
		102	such as Windows) and lots of real-world knowledge and workarounds for
		103	platform bugs and differences.
		104
67	Of course, if you want lots of policy (this can arguably be somewhat	105	Now, if you I<do want> lots of policy (this can arguably be somewhat
68	useful) and you want to force your users to use the one and only event	106	useful) and you want to force your users to use the one and only event
69	model, you should I<not> use this module.	107	model, you should I<not> use this module.
70		108
71	=head1 DESCRIPTION	109	=head1 DESCRIPTION
72		110
…		…
102	starts using it, all bets are off. Maybe you should tell their authors to	140	starts using it, all bets are off. Maybe you should tell their authors to
103	use AnyEvent so their modules work together with others seamlessly...	141	use AnyEvent so their modules work together with others seamlessly...
104		142
105	The pure-perl implementation of AnyEvent is called	143	The pure-perl implementation of AnyEvent is called
106	C<AnyEvent::Impl::Perl>. Like other event modules you can load it	144	C<AnyEvent::Impl::Perl>. Like other event modules you can load it
107	explicitly.	145	explicitly and enjoy the high availability of that event loop :)
108		146
109	=head1 WATCHERS	147	=head1 WATCHERS
110		148
111	AnyEvent has the central concept of a I<watcher>, which is an object that	149	AnyEvent has the central concept of a I<watcher>, which is an object that
112	stores relevant data for each kind of event you are waiting for, such as	150	stores relevant data for each kind of event you are waiting for, such as
113	the callback to call, the filehandle to watch, etc.	151	the callback to call, the file handle to watch, etc.
114		152
115	These watchers are normal Perl objects with normal Perl lifetime. After	153	These watchers are normal Perl objects with normal Perl lifetime. After
116	creating a watcher it will immediately "watch" for events and invoke the	154	creating a watcher it will immediately "watch" for events and invoke the
117	callback when the event occurs (of course, only when the event model	155	callback when the event occurs (of course, only when the event model
118	is in control).	156	is in control).
119		157
		158	Note that B<callbacks must not permanently change global variables>
		159	potentially in use by the event loop (such as C<$_> or C<$[>) and that B<<
		160	callbacks must not C<die> >>. The former is good programming practise in
		161	Perl and the latter stems from the fact that exception handling differs
		162	widely between event loops.
		163
120	To disable the watcher you have to destroy it (e.g. by setting the	164	To disable the watcher you have to destroy it (e.g. by setting the
121	variable you store it in to C<undef> or otherwise deleting all references	165	variable you store it in to C<undef> or otherwise deleting all references
122	to it).	166	to it).
123		167
124	All watchers are created by calling a method on the C<AnyEvent> class.	168	All watchers are created by calling a method on the C<AnyEvent> class.
…		…
126	Many watchers either are used with "recursion" (repeating timers for	170	Many watchers either are used with "recursion" (repeating timers for
127	example), or need to refer to their watcher object in other ways.	171	example), or need to refer to their watcher object in other ways.
128		172
129	An any way to achieve that is this pattern:	173	An any way to achieve that is this pattern:
130		174
131	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	175	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
132	# you can use $w here, for example to undef it	176	# you can use $w here, for example to undef it
133	undef $w;	177	undef $w;
134	});	178	});
135		179
136	Note that C<my $w; $w => combination. This is necessary because in Perl,	180	Note that C<my $w; $w => combination. This is necessary because in Perl,
137	my variables are only visible after the statement in which they are	181	my variables are only visible after the statement in which they are
138	declared.	182	declared.
139		183
140	=head2 I/O WATCHERS	184	=head2 I/O WATCHERS
141		185
		186	$w = AnyEvent->io (
		187	fh => <filehandle_or_fileno>,
		188	poll => <"r" or "w">,
		189	cb => <callback>,
		190	);
		191
142	You can create an I/O watcher by calling the C<< AnyEvent->io >> method	192	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
143	with the following mandatory key-value pairs as arguments:	193	with the following mandatory key-value pairs as arguments:
144		194
145	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch	195	C<fh> is the Perl I<file handle> (or a naked file descriptor) to watch
		196	for events (AnyEvent might or might not keep a reference to this file
		197	handle). Note that only file handles pointing to things for which
		198	non-blocking operation makes sense are allowed. This includes sockets,
		199	most character devices, pipes, fifos and so on, but not for example files
		200	or block devices.
		201
146	for events. C<poll> must be a string that is either C<r> or C<w>,	202	C<poll> must be a string that is either C<r> or C<w>, which creates a
147	which creates a watcher waiting for "r"eadable or "w"ritable events,	203	watcher waiting for "r"eadable or "w"ritable events, respectively.
		204
148	respectively. C<cb> is the callback to invoke each time the file handle	205	C<cb> is the callback to invoke each time the file handle becomes ready.
149	becomes ready.
150		206
151	Although the callback might get passed parameters, their value and	207	Although the callback might get passed parameters, their value and
152	presence is undefined and you cannot rely on them. Portable AnyEvent	208	presence is undefined and you cannot rely on them. Portable AnyEvent
153	callbacks cannot use arguments passed to I/O watcher callbacks.	209	callbacks cannot use arguments passed to I/O watcher callbacks.
154		210
…		…
158		214
159	Some event loops issue spurious readyness notifications, so you should	215	Some event loops issue spurious readyness notifications, so you should
160	always use non-blocking calls when reading/writing from/to your file	216	always use non-blocking calls when reading/writing from/to your file
161	handles.	217	handles.
162		218
163	Example:
164
165	# wait for readability of STDIN, then read a line and disable the watcher	219	Example: wait for readability of STDIN, then read a line and disable the
		220	watcher.
		221
166	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	222	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
167	chomp (my $input = <STDIN>);	223	chomp (my $input = <STDIN>);
168	warn "read: $input\n";	224	warn "read: $input\n";
169	undef $w;	225	undef $w;
170	});	226	});
171		227
172	=head2 TIME WATCHERS	228	=head2 TIME WATCHERS
173		229
		230	$w = AnyEvent->timer (after => <seconds>, cb => <callback>);
		231
		232	$w = AnyEvent->timer (
		233	after => <fractional_seconds>,
		234	interval => <fractional_seconds>,
		235	cb => <callback>,
		236	);
		237
174	You can create a time watcher by calling the C<< AnyEvent->timer >>	238	You can create a time watcher by calling the C<< AnyEvent->timer >>
175	method with the following mandatory arguments:	239	method with the following mandatory arguments:
176		240
177	C<after> specifies after how many seconds (fractional values are	241	C<after> specifies after how many seconds (fractional values are
178	supported) the callback should be invoked. C<cb> is the callback to invoke	242	supported) the callback should be invoked. C<cb> is the callback to invoke
…		…
180		244
181	Although the callback might get passed parameters, their value and	245	Although the callback might get passed parameters, their value and
182	presence is undefined and you cannot rely on them. Portable AnyEvent	246	presence is undefined and you cannot rely on them. Portable AnyEvent
183	callbacks cannot use arguments passed to time watcher callbacks.	247	callbacks cannot use arguments passed to time watcher callbacks.
184		248
185	The timer callback will be invoked at most once: if you want a repeating	249	The callback will normally be invoked once only. If you specify another
186	timer you have to create a new watcher (this is a limitation by both Tk	250	parameter, C<interval>, as a strictly positive number (> 0), then the
187	and Glib).	251	callback will be invoked regularly at that interval (in fractional
		252	seconds) after the first invocation. If C<interval> is specified with a
		253	false value, then it is treated as if it were missing.
188		254
189	Example:	255	The callback will be rescheduled before invoking the callback, but no
		256	attempt is done to avoid timer drift in most backends, so the interval is
		257	only approximate.
190		258
191	# fire an event after 7.7 seconds	259	Example: fire an event after 7.7 seconds.
		260
192	my $w = AnyEvent->timer (after => 7.7, cb => sub {	261	my $w = AnyEvent->timer (after => 7.7, cb => sub {
193	warn "timeout\n";	262	warn "timeout\n";
194	});	263	});
195		264
196	# to cancel the timer:	265	# to cancel the timer:
197	undef $w;	266	undef $w;
198		267
199	Example 2:
200
201	# fire an event after 0.5 seconds, then roughly every second	268	Example 2: fire an event after 0.5 seconds, then roughly every second.
202	my $w;
203		269
204	my $cb = sub {
205	# cancel the old timer while creating a new one
206	$w = AnyEvent->timer (after => 1, cb => $cb);	270	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		271	warn "timeout\n";
207	};	272	};
208
209	# start the "loop" by creating the first watcher
210	$w = AnyEvent->timer (after => 0.5, cb => $cb);
211		273
212	=head3 TIMING ISSUES	274	=head3 TIMING ISSUES
213		275
214	There are two ways to handle timers: based on real time (relative, "fire	276	There are two ways to handle timers: based on real time (relative, "fire
215	in 10 seconds") and based on wallclock time (absolute, "fire at 12	277	in 10 seconds") and based on wallclock time (absolute, "fire at 12
…		…
227	timers.	289	timers.
228		290
229	AnyEvent always prefers relative timers, if available, matching the	291	AnyEvent always prefers relative timers, if available, matching the
230	AnyEvent API.	292	AnyEvent API.
231		293
		294	AnyEvent has two additional methods that return the "current time":
		295
		296	=over 4
		297
		298	=item AnyEvent->time
		299
		300	This returns the "current wallclock time" as a fractional number of
		301	seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
		302	return, and the result is guaranteed to be compatible with those).
		303
		304	It progresses independently of any event loop processing, i.e. each call
		305	will check the system clock, which usually gets updated frequently.
		306
		307	=item AnyEvent->now
		308
		309	This also returns the "current wallclock time", but unlike C<time>, above,
		310	this value might change only once per event loop iteration, depending on
		311	the event loop (most return the same time as C<time>, above). This is the
		312	time that AnyEvent's timers get scheduled against.
		313
		314	I<In almost all cases (in all cases if you don't care), this is the
		315	function to call when you want to know the current time.>
		316
		317	This function is also often faster then C<< AnyEvent->time >>, and
		318	thus the preferred method if you want some timestamp (for example,
		319	L<AnyEvent::Handle> uses this to update it's activity timeouts).
		320
		321	The rest of this section is only of relevance if you try to be very exact
		322	with your timing, you can skip it without bad conscience.
		323
		324	For a practical example of when these times differ, consider L<Event::Lib>
		325	and L<EV> and the following set-up:
		326
		327	The event loop is running and has just invoked one of your callback at
		328	time=500 (assume no other callbacks delay processing). In your callback,
		329	you wait a second by executing C<sleep 1> (blocking the process for a
		330	second) and then (at time=501) you create a relative timer that fires
		331	after three seconds.
		332
		333	With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
		334	both return C<501>, because that is the current time, and the timer will
		335	be scheduled to fire at time=504 (C<501> + C<3>).
		336
		337	With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
		338	time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
		339	last event processing phase started. With L<EV>, your timer gets scheduled
		340	to run at time=503 (C<500> + C<3>).
		341
		342	In one sense, L<Event::Lib> is more exact, as it uses the current time
		343	regardless of any delays introduced by event processing. However, most
		344	callbacks do not expect large delays in processing, so this causes a
		345	higher drift (and a lot more system calls to get the current time).
		346
		347	In another sense, L<EV> is more exact, as your timer will be scheduled at
		348	the same time, regardless of how long event processing actually took.
		349
		350	In either case, if you care (and in most cases, you don't), then you
		351	can get whatever behaviour you want with any event loop, by taking the
		352	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
		353	account.
		354
		355	=item AnyEvent->now_update
		356
		357	Some event loops (such as L<EV> or L<AnyEvent::Impl::Perl>) cache
		358	the current time for each loop iteration (see the discussion of L<<
		359	AnyEvent->now >>, above).
		360
		361	When a callback runs for a long time (or when the process sleeps), then
		362	this "current" time will differ substantially from the real time, which
		363	might affect timers and time-outs.
		364
		365	When this is the case, you can call this method, which will update the
		366	event loop's idea of "current time".
		367
		368	Note that updating the time I<might> cause some events to be handled.
		369
		370	=back
		371
232	=head2 SIGNAL WATCHERS	372	=head2 SIGNAL WATCHERS
233		373
		374	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		375
234	You can watch for signals using a signal watcher, C<signal> is the signal	376	You can watch for signals using a signal watcher, C<signal> is the signal
235	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to	377	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
236	be invoked whenever a signal occurs.	378	callback to be invoked whenever a signal occurs.
237		379
238	Although the callback might get passed parameters, their value and	380	Although the callback might get passed parameters, their value and
239	presence is undefined and you cannot rely on them. Portable AnyEvent	381	presence is undefined and you cannot rely on them. Portable AnyEvent
240	callbacks cannot use arguments passed to signal watcher callbacks.	382	callbacks cannot use arguments passed to signal watcher callbacks.
241		383
242	Multiple signal occurances can be clumped together into one callback	384	Multiple signal occurrences can be clumped together into one callback
243	invocation, and callback invocation will be synchronous. synchronous means	385	invocation, and callback invocation will be synchronous. Synchronous means
244	that it might take a while until the signal gets handled by the process,	386	that it might take a while until the signal gets handled by the process,
245	but it is guarenteed not to interrupt any other callbacks.	387	but it is guaranteed not to interrupt any other callbacks.
246		388
247	The main advantage of using these watchers is that you can share a signal	389	The main advantage of using these watchers is that you can share a signal
248	between multiple watchers.	390	between multiple watchers, and AnyEvent will ensure that signals will not
		391	interrupt your program at bad times.
249		392
250	This watcher might use C<%SIG>, so programs overwriting those signals	393	This watcher might use C<%SIG> (depending on the event loop used),
251	directly will likely not work correctly.	394	so programs overwriting those signals directly will likely not work
		395	correctly.
252		396
253	Example: exit on SIGINT	397	Example: exit on SIGINT
254		398
255	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	399	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
256		400
		401	=head3 Signal Races, Delays and Workarounds
		402
		403	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		404	callbacks to signals in a generic way, which is a pity, as you cannot
		405	do race-free signal handling in perl, requiring C libraries for
		406	this. AnyEvent will try to do it's best, which means in some cases,
		407	signals will be delayed. The maximum time a signal might be delayed is
		408	specified in C<$AnyEvent::MAX_SIGNAL_LATENCY> (default: 10 seconds). This
		409	variable can be changed only before the first signal watcher is created,
		410	and should be left alone otherwise. This variable determines how often
		411	AnyEvent polls for signals (in case a wake-up was missed). Higher values
		412	will cause fewer spurious wake-ups, which is better for power and CPU
		413	saving.
		414
		415	All these problems can be avoided by installing the optional
		416	L<Async::Interrupt> module, which works with most event loops. It will not
		417	work with inherently broken event loops such as L<Event> or L<Event::Lib>
		418	(and not with L<POE> currently, as POE does it's own workaround with
		419	one-second latency). For those, you just have to suffer the delays.
		420
257	=head2 CHILD PROCESS WATCHERS	421	=head2 CHILD PROCESS WATCHERS
258		422
		423	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		424
259	You can also watch on a child process exit and catch its exit status.	425	You can also watch on a child process exit and catch its exit status.
260		426
261	The child process is specified by the C<pid> argument (if set to C<0>, it	427	The child process is specified by the C<pid> argument (one some backends,
262	watches for any child process exit). The watcher will trigger as often	428	using C<0> watches for any child process exit, on others this will
263	as status change for the child are received. This works by installing a	429	croak). The watcher will be triggered only when the child process has
264	signal handler for C<SIGCHLD>. The callback will be called with the pid	430	finished and an exit status is available, not on any trace events
265	and exit status (as returned by waitpid), so unlike other watcher types,	431	(stopped/continued).
266	you I<can> rely on child watcher callback arguments.	432
		433	The callback will be called with the pid and exit status (as returned by
		434	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		435	callback arguments.
		436
		437	This watcher type works by installing a signal handler for C<SIGCHLD>,
		438	and since it cannot be shared, nothing else should use SIGCHLD or reap
		439	random child processes (waiting for specific child processes, e.g. inside
		440	C<system>, is just fine).
267		441
268	There is a slight catch to child watchers, however: you usually start them	442	There is a slight catch to child watchers, however: you usually start them
269	I<after> the child process was created, and this means the process could	443	I<after> the child process was created, and this means the process could
270	have exited already (and no SIGCHLD will be sent anymore).	444	have exited already (and no SIGCHLD will be sent anymore).
271		445
272	Not all event models handle this correctly (POE doesn't), but even for	446	Not all event models handle this correctly (neither POE nor IO::Async do,
		447	see their AnyEvent::Impl manpages for details), but even for event models
273	event models that I<do> handle this correctly, they usually need to be	448	that I<do> handle this correctly, they usually need to be loaded before
274	loaded before the process exits (i.e. before you fork in the first place).	449	the process exits (i.e. before you fork in the first place). AnyEvent's
		450	pure perl event loop handles all cases correctly regardless of when you
		451	start the watcher.
275		452
276	This means you cannot create a child watcher as the very first thing in an	453	This means you cannot create a child watcher as the very first
277	AnyEvent program, you I<have> to create at least one watcher before you	454	thing in an AnyEvent program, you I<have> to create at least one
278	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).	455	watcher before you C<fork> the child (alternatively, you can call
		456	C<AnyEvent::detect>).
		457
		458	As most event loops do not support waiting for child events, they will be
		459	emulated by AnyEvent in most cases, in which the latency and race problems
		460	mentioned in the description of signal watchers apply.
279		461
280	Example: fork a process and wait for it	462	Example: fork a process and wait for it
281		463
282	my $done = AnyEvent->condvar;	464	my $done = AnyEvent->condvar;
283		465
284	AnyEvent::detect; # force event module to be initialised
285
286	my $pid = fork or exit 5;	466	my $pid = fork or exit 5;
287		467
288	my $w = AnyEvent->child (	468	my $w = AnyEvent->child (
289	pid => $pid,	469	pid => $pid,
290	cb => sub {	470	cb => sub {
291	my ($pid, $status) = @_;	471	my ($pid, $status) = @_;
292	warn "pid $pid exited with status $status";	472	warn "pid $pid exited with status $status";
293	$done->send;	473	$done->send;
294	},	474	},
295	);	475	);
296		476
297	# do something else, then wait for process exit	477	# do something else, then wait for process exit
298	$done->wait;	478	$done->recv;
		479
		480	=head2 IDLE WATCHERS
		481
		482	$w = AnyEvent->idle (cb => <callback>);
		483
		484	Sometimes there is a need to do something, but it is not so important
		485	to do it instantly, but only when there is nothing better to do. This
		486	"nothing better to do" is usually defined to be "no other events need
		487	attention by the event loop".
		488
		489	Idle watchers ideally get invoked when the event loop has nothing
		490	better to do, just before it would block the process to wait for new
		491	events. Instead of blocking, the idle watcher is invoked.
		492
		493	Most event loops unfortunately do not really support idle watchers (only
		494	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		495	will simply call the callback "from time to time".
		496
		497	Example: read lines from STDIN, but only process them when the
		498	program is otherwise idle:
		499
		500	my @lines; # read data
		501	my $idle_w;
		502	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		503	push @lines, scalar <STDIN>;
		504
		505	# start an idle watcher, if not already done
		506	$idle_w ||= AnyEvent->idle (cb => sub {
		507	# handle only one line, when there are lines left
		508	if (my $line = shift @lines) {
		509	print "handled when idle: $line";
		510	} else {
		511	# otherwise disable the idle watcher again
		512	undef $idle_w;
		513	}
		514	});
		515	});
299		516
300	=head2 CONDITION VARIABLES	517	=head2 CONDITION VARIABLES
		518
		519	$cv = AnyEvent->condvar;
		520
		521	$cv->send (<list>);
		522	my @res = $cv->recv;
301		523
302	If you are familiar with some event loops you will know that all of them	524	If you are familiar with some event loops you will know that all of them
303	require you to run some blocking "loop", "run" or similar function that	525	require you to run some blocking "loop", "run" or similar function that
304	will actively watch for new events and call your callbacks.	526	will actively watch for new events and call your callbacks.
305		527
306	AnyEvent is different, it expects somebody else to run the event loop and	528	AnyEvent is slightly different: it expects somebody else to run the event
307	will only block when necessary (usually when told by the user).	529	loop and will only block when necessary (usually when told by the user).
308		530
309	The instrument to do that is called a "condition variable", so called	531	The instrument to do that is called a "condition variable", so called
310	because they represent a condition that must become true.	532	because they represent a condition that must become true.
		533
		534	Now is probably a good time to look at the examples further below.
311		535
312	Condition variables can be created by calling the C<< AnyEvent->condvar	536	Condition variables can be created by calling the C<< AnyEvent->condvar
313	>> method, usually without arguments. The only argument pair allowed is	537	>> method, usually without arguments. The only argument pair allowed is
314	C<cb>, which specifies a callback to be called when the condition variable	538	C<cb>, which specifies a callback to be called when the condition variable
315	becomes true.	539	becomes true, with the condition variable as the first argument (but not
		540	the results).
316		541
317	After creation, the conditon variable is "false" until it becomes "true"	542	After creation, the condition variable is "false" until it becomes "true"
318	by calling the C<send> method.	543	by calling the C<send> method (or calling the condition variable as if it
		544	were a callback, read about the caveats in the description for the C<<
		545	->send >> method).
319		546
320	Condition variables are similar to callbacks, except that you can	547	Condition variables are similar to callbacks, except that you can
321	optionally wait for them. They can also be called merge points - points	548	optionally wait for them. They can also be called merge points - points
322	in time where multiple outstandign events have been processed. And yet	549	in time where multiple outstanding events have been processed. And yet
323	another way to call them is transations - each condition variable can be	550	another way to call them is transactions - each condition variable can be
324	used to represent a transaction, which finishes at some point and delivers	551	used to represent a transaction, which finishes at some point and delivers
325	a result.	552	a result. And yet some people know them as "futures" - a promise to
		553	compute/deliver something that you can wait for.
326		554
327	Condition variables are very useful to signal that something has finished,	555	Condition variables are very useful to signal that something has finished,
328	for example, if you write a module that does asynchronous http requests,	556	for example, if you write a module that does asynchronous http requests,
329	then a condition variable would be the ideal candidate to signal the	557	then a condition variable would be the ideal candidate to signal the
330	availability of results. The user can either act when the callback is	558	availability of results. The user can either act when the callback is
331	called or can synchronously C<< ->wait >> for the results.	559	called or can synchronously C<< ->recv >> for the results.
332		560
333	You can also use them to simulate traditional event loops - for example,	561	You can also use them to simulate traditional event loops - for example,
334	you can block your main program until an event occurs - for example, you	562	you can block your main program until an event occurs - for example, you
335	could C<< ->wait >> in your main program until the user clicks the Quit	563	could C<< ->recv >> in your main program until the user clicks the Quit
336	button of your app, which would C<< ->send >> the "quit" event.	564	button of your app, which would C<< ->send >> the "quit" event.
337		565
338	Note that condition variables recurse into the event loop - if you have	566	Note that condition variables recurse into the event loop - if you have
339	two pieces of code that call C<< ->wait >> in a round-robbin fashion, you	567	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
340	lose. Therefore, condition variables are good to export to your caller, but	568	lose. Therefore, condition variables are good to export to your caller, but
341	you should avoid making a blocking wait yourself, at least in callbacks,	569	you should avoid making a blocking wait yourself, at least in callbacks,
342	as this asks for trouble.	570	as this asks for trouble.
343		571
344	Condition variables are represented by hash refs in perl, and the keys	572	Condition variables are represented by hash refs in perl, and the keys
…		…
349		577
350	There are two "sides" to a condition variable - the "producer side" which	578	There are two "sides" to a condition variable - the "producer side" which
351	eventually calls C<< -> send >>, and the "consumer side", which waits	579	eventually calls C<< -> send >>, and the "consumer side", which waits
352	for the send to occur.	580	for the send to occur.
353		581
354	Example:	582	Example: wait for a timer.
355		583
356	# wait till the result is ready	584	# wait till the result is ready
357	my $result_ready = AnyEvent->condvar;	585	my $result_ready = AnyEvent->condvar;
358		586
359	# do something such as adding a timer	587	# do something such as adding a timer
…		…
364	after => 1,	592	after => 1,
365	cb => sub { $result_ready->send },	593	cb => sub { $result_ready->send },
366	);	594	);
367		595
368	# this "blocks" (while handling events) till the callback	596	# this "blocks" (while handling events) till the callback
369	# calls send	597	# calls -<send
370	$result_ready->wait;	598	$result_ready->recv;
		599
		600	Example: wait for a timer, but take advantage of the fact that condition
		601	variables are also callable directly.
		602
		603	my $done = AnyEvent->condvar;
		604	my $delay = AnyEvent->timer (after => 5, cb => $done);
		605	$done->recv;
		606
		607	Example: Imagine an API that returns a condvar and doesn't support
		608	callbacks. This is how you make a synchronous call, for example from
		609	the main program:
		610
		611	use AnyEvent::CouchDB;
		612
		613	...
		614
		615	my @info = $couchdb->info->recv;
		616
		617	And this is how you would just set a callback to be called whenever the
		618	results are available:
		619
		620	$couchdb->info->cb (sub {
		621	my @info = $_[0]->recv;
		622	});
371		623
372	=head3 METHODS FOR PRODUCERS	624	=head3 METHODS FOR PRODUCERS
373		625
374	These methods should only be used by the producing side, i.e. the	626	These methods should only be used by the producing side, i.e. the
375	code/module that eventually sends the signal. Note that it is also	627	code/module that eventually sends the signal. Note that it is also
…		…
378		630
379	=over 4	631	=over 4
380		632
381	=item $cv->send (...)	633	=item $cv->send (...)
382		634
383	Flag the condition as ready - a running C<< ->wait >> and all further	635	Flag the condition as ready - a running C<< ->recv >> and all further
384	calls to C<wait> will (eventually) return after this method has been	636	calls to C<recv> will (eventually) return after this method has been
385	called. If nobody is waiting the send will be remembered.	637	called. If nobody is waiting the send will be remembered.
386		638
387	If a callback has been set on the condition variable, it is called	639	If a callback has been set on the condition variable, it is called
388	immediately from within send.	640	immediately from within send.
389		641
390	Any arguments passed to the C<send> call will be returned by all	642	Any arguments passed to the C<send> call will be returned by all
391	future C<< ->wait >> calls.	643	future C<< ->recv >> calls.
		644
		645	Condition variables are overloaded so one can call them directly (as if
		646	they were a code reference). Calling them directly is the same as calling
		647	C<send>.
392		648
393	=item $cv->croak ($error)	649	=item $cv->croak ($error)
394		650
395	Similar to send, but causes all call's wait C<< ->wait >> to invoke	651	Similar to send, but causes all call's to C<< ->recv >> to invoke
396	C<Carp::croak> with the given error message/object/scalar.	652	C<Carp::croak> with the given error message/object/scalar.
397		653
398	This can be used to signal any errors to the condition variable	654	This can be used to signal any errors to the condition variable
399	user/consumer.	655	user/consumer. Doing it this way instead of calling C<croak> directly
		656	delays the error detetcion, but has the overwhelmign advantage that it
		657	diagnoses the error at the place where the result is expected, and not
		658	deep in some event clalback without connection to the actual code causing
		659	the problem.
400		660
401	=item $cv->begin ([group callback])	661	=item $cv->begin ([group callback])
402		662
403	=item $cv->end	663	=item $cv->end
404		664
…		…
410	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end	670	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
411	>>, the (last) callback passed to C<begin> will be executed. That callback	671	>>, the (last) callback passed to C<begin> will be executed. That callback
412	is I<supposed> to call C<< ->send >>, but that is not required. If no	672	is I<supposed> to call C<< ->send >>, but that is not required. If no
413	callback was set, C<send> will be called without any arguments.	673	callback was set, C<send> will be called without any arguments.
414		674
415	Let's clarify this with the ping example:	675	You can think of C<< $cv->send >> giving you an OR condition (one call
		676	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		677	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		678
		679	Let's start with a simple example: you have two I/O watchers (for example,
		680	STDOUT and STDERR for a program), and you want to wait for both streams to
		681	close before activating a condvar:
		682
		683	my $cv = AnyEvent->condvar;
		684
		685	$cv->begin; # first watcher
		686	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		687	defined sysread $fh1, my $buf, 4096
		688	or $cv->end;
		689	});
		690
		691	$cv->begin; # second watcher
		692	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		693	defined sysread $fh2, my $buf, 4096
		694	or $cv->end;
		695	});
		696
		697	$cv->recv;
		698
		699	This works because for every event source (EOF on file handle), there is
		700	one call to C<begin>, so the condvar waits for all calls to C<end> before
		701	sending.
		702
		703	The ping example mentioned above is slightly more complicated, as the
		704	there are results to be passwd back, and the number of tasks that are
		705	begung can potentially be zero:
416		706
417	my $cv = AnyEvent->condvar;	707	my $cv = AnyEvent->condvar;
418		708
419	my %result;	709	my %result;
420	$cv->begin (sub { $cv->send (\%result) });	710	$cv->begin (sub { $cv->send (\%result) });
…		…
440	loop, which serves two important purposes: first, it sets the callback	730	loop, which serves two important purposes: first, it sets the callback
441	to be called once the counter reaches C<0>, and second, it ensures that	731	to be called once the counter reaches C<0>, and second, it ensures that
442	C<send> is called even when C<no> hosts are being pinged (the loop	732	C<send> is called even when C<no> hosts are being pinged (the loop
443	doesn't execute once).	733	doesn't execute once).
444		734
445	This is the general pattern when you "fan out" into multiple subrequests:	735	This is the general pattern when you "fan out" into multiple (but
446	use an outer C<begin>/C<end> pair to set the callback and ensure C<end>	736	potentially none) subrequests: use an outer C<begin>/C<end> pair to set
447	is called at least once, and then, for each subrequest you start, call	737	the callback and ensure C<end> is called at least once, and then, for each
448	C<begin> and for eahc subrequest you finish, call C<end>.	738	subrequest you start, call C<begin> and for each subrequest you finish,
		739	call C<end>.
449		740
450	=back	741	=back
451		742
452	=head3 METHODS FOR CONSUMERS	743	=head3 METHODS FOR CONSUMERS
453		744
454	These methods should only be used by the consuming side, i.e. the	745	These methods should only be used by the consuming side, i.e. the
455	code awaits the condition.	746	code awaits the condition.
456		747
457	=over 4	748	=over 4
458		749
459	=item $cv->wait	750	=item $cv->recv
460		751
461	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak	752	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
462	>> methods have been called on c<$cv>, while servicing other watchers	753	>> methods have been called on c<$cv>, while servicing other watchers
463	normally.	754	normally.
464		755
…		…
469	function will call C<croak>.	760	function will call C<croak>.
470		761
471	In list context, all parameters passed to C<send> will be returned,	762	In list context, all parameters passed to C<send> will be returned,
472	in scalar context only the first one will be returned.	763	in scalar context only the first one will be returned.
473		764
		765	Note that doing a blocking wait in a callback is not supported by any
		766	event loop, that is, recursive invocation of a blocking C<< ->recv
		767	>> is not allowed, and the C<recv> call will C<croak> if such a
		768	condition is detected. This condition can be slightly loosened by using
		769	L<Coro::AnyEvent>, which allows you to do a blocking C<< ->recv >> from
		770	any thread that doesn't run the event loop itself.
		771
474	Not all event models support a blocking wait - some die in that case	772	Not all event models support a blocking wait - some die in that case
475	(programs might want to do that to stay interactive), so I<if you are	773	(programs might want to do that to stay interactive), so I<if you are
476	using this from a module, never require a blocking wait>, but let the	774	using this from a module, never require a blocking wait>. Instead, let the
477	caller decide whether the call will block or not (for example, by coupling	775	caller decide whether the call will block or not (for example, by coupling
478	condition variables with some kind of request results and supporting	776	condition variables with some kind of request results and supporting
479	callbacks so the caller knows that getting the result will not block,	777	callbacks so the caller knows that getting the result will not block,
480	while still suppporting blocking waits if the caller so desires).	778	while still supporting blocking waits if the caller so desires).
481		779
482	Another reason I<never> to C<< ->wait >> in a module is that you cannot
483	sensibly have two C<< ->wait >>'s in parallel, as that would require
484	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
485	can supply.
486
487	The L<Coro> module, however, I<can> and I<does> supply coroutines and, in
488	fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe
489	versions and also integrates coroutines into AnyEvent, making blocking
490	C<< ->wait >> calls perfectly safe as long as they are done from another
491	coroutine (one that doesn't run the event loop).
492
493	You can ensure that C<< -wait >> never blocks by setting a callback and	780	You can ensure that C<< -recv >> never blocks by setting a callback and
494	only calling C<< ->wait >> from within that callback (or at a later	781	only calling C<< ->recv >> from within that callback (or at a later
495	time). This will work even when the event loop does not support blocking	782	time). This will work even when the event loop does not support blocking
496	waits otherwise.	783	waits otherwise.
497		784
498	=item $bool = $cv->ready	785	=item $bool = $cv->ready
499		786
500	Returns true when the condition is "true", i.e. whether C<send> or	787	Returns true when the condition is "true", i.e. whether C<send> or
501	C<croak> have been called.	788	C<croak> have been called.
502		789
503	=item $cb = $cv->cb ([new callback])	790	=item $cb = $cv->cb ($cb->($cv))
504		791
505	This is a mutator function that returns the callback set and optionally	792	This is a mutator function that returns the callback set and optionally
506	replaces it before doing so.	793	replaces it before doing so.
507		794
508	The callback will be called when the condition becomes "true", i.e. when	795	The callback will be called when the condition becomes (or already was)
509	C<send> or C<croak> are called. Calling C<wait> inside the callback	796	"true", i.e. when C<send> or C<croak> are called (or were called), with
		797	the only argument being the condition variable itself. Calling C<recv>
510	or at any later time is guaranteed not to block.	798	inside the callback or at any later time is guaranteed not to block.
511		799
512	=back	800	=back
513		801
		802	=head1 SUPPORTED EVENT LOOPS/BACKENDS
		803
		804	The available backend classes are (every class has its own manpage):
		805
		806	=over 4
		807
		808	=item Backends that are autoprobed when no other event loop can be found.
		809
		810	EV is the preferred backend when no other event loop seems to be in
		811	use. If EV is not installed, then AnyEvent will try Event, and, failing
		812	that, will fall back to its own pure-perl implementation, which is
		813	available everywhere as it comes with AnyEvent itself.
		814
		815	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		816	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		817	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
		818
		819	=item Backends that are transparently being picked up when they are used.
		820
		821	These will be used when they are currently loaded when the first watcher
		822	is created, in which case it is assumed that the application is using
		823	them. This means that AnyEvent will automatically pick the right backend
		824	when the main program loads an event module before anything starts to
		825	create watchers. Nothing special needs to be done by the main program.
		826
		827	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		828	AnyEvent::Impl::Tk based on Tk, very broken.
		829	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		830	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		831	AnyEvent::Impl::Irssi used when running within irssi.
		832
		833	=item Backends with special needs.
		834
		835	Qt requires the Qt::Application to be instantiated first, but will
		836	otherwise be picked up automatically. As long as the main program
		837	instantiates the application before any AnyEvent watchers are created,
		838	everything should just work.
		839
		840	AnyEvent::Impl::Qt based on Qt.
		841
		842	Support for IO::Async can only be partial, as it is too broken and
		843	architecturally limited to even support the AnyEvent API. It also
		844	is the only event loop that needs the loop to be set explicitly, so
		845	it can only be used by a main program knowing about AnyEvent. See
		846	L<AnyEvent::Impl::Async> for the gory details.
		847
		848	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
		849
		850	=item Event loops that are indirectly supported via other backends.
		851
		852	Some event loops can be supported via other modules:
		853
		854	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		855
		856	B<WxWidgets> has no support for watching file handles. However, you can
		857	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		858	polls 20 times per second, which was considered to be too horrible to even
		859	consider for AnyEvent.
		860
		861	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		862	backend, so it can be supported through POE.
		863
		864	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		865	load L<POE> when detecting them, in the hope that POE will pick them up,
		866	in which case everything will be automatic.
		867
		868	=back
		869
514	=head1 GLOBAL VARIABLES AND FUNCTIONS	870	=head1 GLOBAL VARIABLES AND FUNCTIONS
515		871
		872	These are not normally required to use AnyEvent, but can be useful to
		873	write AnyEvent extension modules.
		874
516	=over 4	875	=over 4
517		876
518	=item $AnyEvent::MODEL	877	=item $AnyEvent::MODEL
519		878
520	Contains C<undef> until the first watcher is being created. Then it	879	Contains C<undef> until the first watcher is being created, before the
		880	backend has been autodetected.
		881
521	contains the event model that is being used, which is the name of the	882	Afterwards it contains the event model that is being used, which is the
522	Perl class implementing the model. This class is usually one of the	883	name of the Perl class implementing the model. This class is usually one
523	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	884	of the C<AnyEvent::Impl:xxx> modules, but can be any other class in the
524	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	885	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
525		886	will be C<urxvt::anyevent>).
526	The known classes so far are:
527
528	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
529	AnyEvent::Impl::Event based on Event, second best choice.
530	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
531	AnyEvent::Impl::Glib based on Glib, third-best choice.
532	AnyEvent::Impl::Tk based on Tk, very bad choice.
533	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
534	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
535	AnyEvent::Impl::POE based on POE, not generic enough for full support.
536
537	There is no support for WxWidgets, as WxWidgets has no support for
538	watching file handles. However, you can use WxWidgets through the
539	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
540	second, which was considered to be too horrible to even consider for
541	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
542	it's adaptor.
543
544	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
545	autodetecting them.
546		887
547	=item AnyEvent::detect	888	=item AnyEvent::detect
548		889
549	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	890	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
550	if necessary. You should only call this function right before you would	891	if necessary. You should only call this function right before you would
551	have created an AnyEvent watcher anyway, that is, as late as possible at	892	have created an AnyEvent watcher anyway, that is, as late as possible at
552	runtime.	893	runtime, and not e.g. while initialising of your module.
		894
		895	If you need to do some initialisation before AnyEvent watchers are
		896	created, use C<post_detect>.
553		897
554	=item $guard = AnyEvent::post_detect { BLOCK }	898	=item $guard = AnyEvent::post_detect { BLOCK }
555		899
556	Arranges for the code block to be executed as soon as the event model is	900	Arranges for the code block to be executed as soon as the event model is
557	autodetected (or immediately if this has already happened).	901	autodetected (or immediately if this has already happened).
558		902
		903	The block will be executed I<after> the actual backend has been detected
		904	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		905	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		906	other initialisations - see the sources of L<AnyEvent::Strict> or
		907	L<AnyEvent::AIO> to see how this is used.
		908
		909	The most common usage is to create some global watchers, without forcing
		910	event module detection too early, for example, L<AnyEvent::AIO> creates
		911	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		912	avoid autodetecting the event module at load time.
		913
559	If called in scalar or list context, then it creates and returns an object	914	If called in scalar or list context, then it creates and returns an object
560	that automatically removes the callback again when it is destroyed. See	915	that automatically removes the callback again when it is destroyed (or
		916	C<undef> when the hook was immediately executed). See L<AnyEvent::AIO> for
561	L<Coro::BDB> for a case where this is useful.	917	a case where this is useful.
		918
		919	Example: Create a watcher for the IO::AIO module and store it in
		920	C<$WATCHER>. Only do so after the event loop is initialised, though.
		921
		922	our WATCHER;
		923
		924	my $guard = AnyEvent::post_detect {
		925	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		926	};
		927
		928	# the ||= is important in case post_detect immediately runs the block,
		929	# as to not clobber the newly-created watcher. assigning both watcher and
		930	# post_detect guard to the same variable has the advantage of users being
		931	# able to just C<undef $WATCHER> if the watcher causes them grief.
		932
		933	$WATCHER ||= $guard;
562		934
563	=item @AnyEvent::post_detect	935	=item @AnyEvent::post_detect
564		936
565	If there are any code references in this array (you can C<push> to it	937	If there are any code references in this array (you can C<push> to it
566	before or after loading AnyEvent), then they will called directly after	938	before or after loading AnyEvent), then they will called directly after
567	the event loop has been chosen.	939	the event loop has been chosen.
568		940
569	You should check C<$AnyEvent::MODEL> before adding to this array, though:	941	You should check C<$AnyEvent::MODEL> before adding to this array, though:
570	if it contains a true value then the event loop has already been detected,	942	if it is defined then the event loop has already been detected, and the
571	and the array will be ignored.	943	array will be ignored.
572		944
573	Best use C<AnyEvent::post_detect { BLOCK }> instead.	945	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		946	it,as it takes care of these details.
		947
		948	This variable is mainly useful for modules that can do something useful
		949	when AnyEvent is used and thus want to know when it is initialised, but do
		950	not need to even load it by default. This array provides the means to hook
		951	into AnyEvent passively, without loading it.
574		952
575	=back	953	=back
576		954
577	=head1 WHAT TO DO IN A MODULE	955	=head1 WHAT TO DO IN A MODULE
578		956
…		…
582	Be careful when you create watchers in the module body - AnyEvent will	960	Be careful when you create watchers in the module body - AnyEvent will
583	decide which event module to use as soon as the first method is called, so	961	decide which event module to use as soon as the first method is called, so
584	by calling AnyEvent in your module body you force the user of your module	962	by calling AnyEvent in your module body you force the user of your module
585	to load the event module first.	963	to load the event module first.
586		964
587	Never call C<< ->wait >> on a condition variable unless you I<know> that	965	Never call C<< ->recv >> on a condition variable unless you I<know> that
588	the C<< ->send >> method has been called on it already. This is	966	the C<< ->send >> method has been called on it already. This is
589	because it will stall the whole program, and the whole point of using	967	because it will stall the whole program, and the whole point of using
590	events is to stay interactive.	968	events is to stay interactive.
591		969
592	It is fine, however, to call C<< ->wait >> when the user of your module	970	It is fine, however, to call C<< ->recv >> when the user of your module
593	requests it (i.e. if you create a http request object ad have a method	971	requests it (i.e. if you create a http request object ad have a method
594	called C<results> that returns the results, it should call C<< ->wait >>	972	called C<results> that returns the results, it should call C<< ->recv >>
595	freely, as the user of your module knows what she is doing. always).	973	freely, as the user of your module knows what she is doing. always).
596		974
597	=head1 WHAT TO DO IN THE MAIN PROGRAM	975	=head1 WHAT TO DO IN THE MAIN PROGRAM
598		976
599	There will always be a single main program - the only place that should	977	There will always be a single main program - the only place that should
…		…
601		979
602	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	980	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
603	do anything special (it does not need to be event-based) and let AnyEvent	981	do anything special (it does not need to be event-based) and let AnyEvent
604	decide which implementation to chose if some module relies on it.	982	decide which implementation to chose if some module relies on it.
605		983
606	If the main program relies on a specific event model. For example, in	984	If the main program relies on a specific event model - for example, in
607	Gtk2 programs you have to rely on the Glib module. You should load the	985	Gtk2 programs you have to rely on the Glib module - you should load the
608	event module before loading AnyEvent or any module that uses it: generally	986	event module before loading AnyEvent or any module that uses it: generally
609	speaking, you should load it as early as possible. The reason is that	987	speaking, you should load it as early as possible. The reason is that
610	modules might create watchers when they are loaded, and AnyEvent will	988	modules might create watchers when they are loaded, and AnyEvent will
611	decide on the event model to use as soon as it creates watchers, and it	989	decide on the event model to use as soon as it creates watchers, and it
612	might chose the wrong one unless you load the correct one yourself.	990	might chose the wrong one unless you load the correct one yourself.
613		991
614	You can chose to use a rather inefficient pure-perl implementation by	992	You can chose to use a pure-perl implementation by loading the
615	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	993	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
616	behaviour everywhere, but letting AnyEvent chose is generally better.	994	everywhere, but letting AnyEvent chose the model is generally better.
		995
		996	=head2 MAINLOOP EMULATION
		997
		998	Sometimes (often for short test scripts, or even standalone programs who
		999	only want to use AnyEvent), you do not want to run a specific event loop.
		1000
		1001	In that case, you can use a condition variable like this:
		1002
		1003	AnyEvent->condvar->recv;
		1004
		1005	This has the effect of entering the event loop and looping forever.
		1006
		1007	Note that usually your program has some exit condition, in which case
		1008	it is better to use the "traditional" approach of storing a condition
		1009	variable somewhere, waiting for it, and sending it when the program should
		1010	exit cleanly.
		1011
617		1012
618	=head1 OTHER MODULES	1013	=head1 OTHER MODULES
619		1014
620	The following is a non-exhaustive list of additional modules that use	1015	The following is a non-exhaustive list of additional modules that use
621	AnyEvent and can therefore be mixed easily with other AnyEvent modules	1016	AnyEvent as a client and can therefore be mixed easily with other AnyEvent
622	in the same program. Some of the modules come with AnyEvent, some are	1017	modules and other event loops in the same program. Some of the modules
623	available via CPAN.	1018	come with AnyEvent, most are available via CPAN.
624		1019
625	=over 4	1020	=over 4
626		1021
627	=item L<AnyEvent::Util>	1022	=item L<AnyEvent::Util>
628		1023
629	Contains various utility functions that replace often-used but blocking	1024	Contains various utility functions that replace often-used but blocking
630	functions such as C<inet_aton> by event-/callback-based versions.	1025	functions such as C<inet_aton> by event-/callback-based versions.
631		1026
		1027	=item L<AnyEvent::Socket>
		1028
		1029	Provides various utility functions for (internet protocol) sockets,
		1030	addresses and name resolution. Also functions to create non-blocking tcp
		1031	connections or tcp servers, with IPv6 and SRV record support and more.
		1032
632	=item L<AnyEvent::Handle>	1033	=item L<AnyEvent::Handle>
633		1034
634	Provide read and write buffers and manages watchers for reads and writes.	1035	Provide read and write buffers, manages watchers for reads and writes,
		1036	supports raw and formatted I/O, I/O queued and fully transparent and
		1037	non-blocking SSL/TLS (via L<AnyEvent::TLS>.
635		1038
636	=item L<AnyEvent::Socket>	1039	=item L<AnyEvent::DNS>
637		1040
638	Provides a means to do non-blocking connects, accepts etc.	1041	Provides rich asynchronous DNS resolver capabilities.
		1042
		1043	=item L<AnyEvent::HTTP>
		1044
		1045	A simple-to-use HTTP library that is capable of making a lot of concurrent
		1046	HTTP requests.
639		1047
640	=item L<AnyEvent::HTTPD>	1048	=item L<AnyEvent::HTTPD>
641		1049
642	Provides a simple web application server framework.	1050	Provides a simple web application server framework.
643		1051
644	=item L<AnyEvent::DNS>
645
646	Provides asynchronous DNS resolver capabilities, beyond what
647	L<AnyEvent::Util> offers.
648
649	=item L<AnyEvent::FastPing>	1052	=item L<AnyEvent::FastPing>
650		1053
651	The fastest ping in the west.	1054	The fastest ping in the west.
652		1055
		1056	=item L<AnyEvent::DBI>
		1057
		1058	Executes L<DBI> requests asynchronously in a proxy process.
		1059
		1060	=item L<AnyEvent::AIO>
		1061
		1062	Truly asynchronous I/O, should be in the toolbox of every event
		1063	programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
		1064	together.
		1065
		1066	=item L<AnyEvent::BDB>
		1067
		1068	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
		1069	L<BDB> and AnyEvent together.
		1070
		1071	=item L<AnyEvent::GPSD>
		1072
		1073	A non-blocking interface to gpsd, a daemon delivering GPS information.
		1074
653	=item L<Net::IRC3>	1075	=item L<AnyEvent::IRC>
654		1076
655	AnyEvent based IRC client module family.	1077	AnyEvent based IRC client module family (replacing the older Net::IRC3).
656		1078
657	=item L<Net::XMPP2>	1079	=item L<AnyEvent::XMPP>
658		1080
659	AnyEvent based XMPP (Jabber protocol) module family.	1081	AnyEvent based XMPP (Jabber protocol) module family (replacing the older
		1082	Net::XMPP2>.
		1083
		1084	=item L<AnyEvent::IGS>
		1085
		1086	A non-blocking interface to the Internet Go Server protocol (used by
		1087	L<App::IGS>).
660		1088
661	=item L<Net::FCP>	1089	=item L<Net::FCP>
662		1090
663	AnyEvent-based implementation of the Freenet Client Protocol, birthplace	1091	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
664	of AnyEvent.	1092	of AnyEvent.
…		…
669		1097
670	=item L<Coro>	1098	=item L<Coro>
671		1099
672	Has special support for AnyEvent via L<Coro::AnyEvent>.	1100	Has special support for AnyEvent via L<Coro::AnyEvent>.
673		1101
674	=item L<IO::Lambda>
675
676	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
677
678	=item L<IO::AIO>
679
680	Truly asynchronous I/O, should be in the toolbox of every event
681	programmer. Can be trivially made to use AnyEvent.
682
683	=item L<BDB>
684
685	Truly asynchronous Berkeley DB access. Can be trivially made to use
686	AnyEvent.
687
688	=back	1102	=back
689		1103
690	=cut	1104	=cut
691		1105
692	package AnyEvent;	1106	package AnyEvent;
693		1107
		1108	# basically a tuned-down version of common::sense
		1109	sub common_sense {
694	no warnings;	1110	# no warnings
695	use strict;	1111	${^WARNING_BITS} ^= ${^WARNING_BITS};
		1112	# use strict vars subs
		1113	$^H |= 0x00000600;
		1114	}
696		1115
		1116	BEGIN { AnyEvent::common_sense }
		1117
697	use Carp;	1118	use Carp ();
698		1119
699	our $VERSION = '3.4';	1120	our $VERSION = 4.91;
700	our $MODEL;	1121	our $MODEL;
701		1122
702	our $AUTOLOAD;	1123	our $AUTOLOAD;
703	our @ISA;	1124	our @ISA;
704		1125
705	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
706
707	our @REGISTRY;	1126	our @REGISTRY;
708		1127
		1128	our $WIN32;
		1129
		1130	our $VERBOSE;
		1131
		1132	BEGIN {
		1133	eval "sub WIN32(){ " . (($^O =~ /mswin32/i)*1) ." }";
		1134	eval "sub TAINT(){ " . (${^TAINT}*1) . " }";
		1135
		1136	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1137	if ${^TAINT};
		1138
		1139	$VERBOSE = $ENV{PERL_ANYEVENT_VERBOSE}*1;
		1140
		1141	}
		1142
		1143	our $MAX_SIGNAL_LATENCY = 10;
		1144
		1145	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		1146
		1147	{
		1148	my $idx;
		1149	$PROTOCOL{$_} = ++$idx
		1150	for reverse split /\s*,\s*/,
		1151	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		1152	}
		1153
709	my @models = (	1154	my @models = (
710	[EV:: => AnyEvent::Impl::EV::],	1155	[EV:: => AnyEvent::Impl::EV:: , 1],
711	[Event:: => AnyEvent::Impl::Event::],	1156	[Event:: => AnyEvent::Impl::Event::, 1],
		1157	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl:: , 1],
		1158	# everything below here will not (normally) be autoprobed
		1159	# as the pureperl backend should work everywhere
		1160	# and is usually faster
		1161	[Glib:: => AnyEvent::Impl::Glib:: , 1], # becomes extremely slow with many watchers
		1162	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		1163	[Irssi:: => AnyEvent::Impl::Irssi::], # Irssi has a bogus "Event" package
712	[Tk:: => AnyEvent::Impl::Tk::],	1164	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		1165	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		1166	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
713	[Wx:: => AnyEvent::Impl::POE::],	1167	[Wx:: => AnyEvent::Impl::POE::],
714	[Prima:: => AnyEvent::Impl::POE::],	1168	[Prima:: => AnyEvent::Impl::POE::],
715	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1169	# IO::Async is just too broken - we would need workarounds for its
716	# everything below here will not be autoprobed as the pureperl backend should work everywhere	1170	# byzantine signal and broken child handling, among others.
717	[Glib:: => AnyEvent::Impl::Glib::],	1171	# IO::Async is rather hard to detect, as it doesn't have any
718	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy	1172	# obvious default class.
719	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program	1173	# [0, IO::Async:: => AnyEvent::Impl::IOAsync::], # requires special main program
720	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza	1174	# [0, IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1175	# [0, IO::Async::Notifier:: => AnyEvent::Impl::IOAsync::], # requires special main program
721	);	1176	);
722		1177
723	our %method = map +($_ => 1), qw(io timer signal child condvar one_event DESTROY);	1178	our %method = map +($_ => 1),
		1179	qw(io timer time now now_update signal child idle condvar one_event DESTROY);
724		1180
725	our @post_detect;	1181	our @post_detect;
726		1182
727	sub post_detect(&) {	1183	sub post_detect(&) {
728	my ($cb) = @_;	1184	my ($cb) = @_;
729		1185
730	if ($MODEL) {	1186	if ($MODEL) {
731	$cb->();	1187	$cb->();
732		1188
733	1	1189	undef
734	} else {	1190	} else {
735	push @post_detect, $cb;	1191	push @post_detect, $cb;
736		1192
737	defined wantarray	1193	defined wantarray
738	? bless \$cb, "AnyEvent::Util::Guard"	1194	? bless \$cb, "AnyEvent::Util::postdetect"
739	: ()	1195	: ()
740	}	1196	}
741	}	1197	}
742		1198
743	sub AnyEvent::Util::Guard::DESTROY {	1199	sub AnyEvent::Util::postdetect::DESTROY {
744	@post_detect = grep $_ != ${$_[0]}, @post_detect;	1200	@post_detect = grep $_ != ${$_[0]}, @post_detect;
745	}	1201	}
746		1202
747	sub detect() {	1203	sub detect() {
748	unless ($MODEL) {	1204	unless ($MODEL) {
749	no strict 'refs';	1205	local $SIG{__DIE__};
750		1206
751	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	1207	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
752	my $model = "AnyEvent::Impl::$1";	1208	my $model = "AnyEvent::Impl::$1";
753	if (eval "require $model") {	1209	if (eval "require $model") {
754	$MODEL = $model;	1210	$MODEL = $model;
755	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	1211	warn "AnyEvent: loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.\n" if $VERBOSE >= 2;
756	} else {	1212	} else {
757	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;	1213	warn "AnyEvent: unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@" if $VERBOSE;
758	}	1214	}
759	}	1215	}
760		1216
761	# check for already loaded models	1217	# check for already loaded models
762	unless ($MODEL) {	1218	unless ($MODEL) {
763	for (@REGISTRY, @models) {	1219	for (@REGISTRY, @models) {
764	my ($package, $model) = @$_;	1220	my ($package, $model) = @$_;
765	if (${"$package\::VERSION"} > 0) {	1221	if (${"$package\::VERSION"} > 0) {
766	if (eval "require $model") {	1222	if (eval "require $model") {
767	$MODEL = $model;	1223	$MODEL = $model;
768	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;	1224	warn "AnyEvent: autodetected model '$model', using it.\n" if $VERBOSE >= 2;
769	last;	1225	last;
770	}	1226	}
771	}	1227	}
772	}	1228	}
773		1229
774	unless ($MODEL) {	1230	unless ($MODEL) {
775	# try to load a model	1231	# try to autoload a model
776
777	for (@REGISTRY, @models) {	1232	for (@REGISTRY, @models) {
778	my ($package, $model) = @$_;	1233	my ($package, $model, $autoload) = @$_;
		1234	if (
		1235	$autoload
779	if (eval "require $package"	1236	and eval "require $package"
780	and ${"$package\::VERSION"} > 0	1237	and ${"$package\::VERSION"} > 0
781	and eval "require $model") {	1238	and eval "require $model"
		1239	) {
782	$MODEL = $model;	1240	$MODEL = $model;
783	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;	1241	warn "AnyEvent: autoloaded model '$model', using it.\n" if $VERBOSE >= 2;
784	last;	1242	last;
785	}	1243	}
786	}	1244	}
787		1245
788	$MODEL	1246	$MODEL
789	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.";	1247	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.\n";
790	}	1248	}
791	}	1249	}
792		1250
		1251	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		1252
793	unshift @ISA, $MODEL;	1253	unshift @ISA, $MODEL;
794	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	1254
		1255	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
795		1256
796	(shift @post_detect)->() while @post_detect;	1257	(shift @post_detect)->() while @post_detect;
797	}	1258	}
798		1259
799	$MODEL	1260	$MODEL
…		…
801		1262
802	sub AUTOLOAD {	1263	sub AUTOLOAD {
803	(my $func = $AUTOLOAD) =~ s/.*://;	1264	(my $func = $AUTOLOAD) =~ s/.*://;
804		1265
805	$method{$func}	1266	$method{$func}
806	or croak "$func: not a valid method for AnyEvent objects";	1267	or Carp::croak "$func: not a valid method for AnyEvent objects";
807		1268
808	detect unless $MODEL;	1269	detect unless $MODEL;
809		1270
810	my $class = shift;	1271	my $class = shift;
811	$class->$func (@_);	1272	$class->$func (@_);
812	}	1273	}
813		1274
		1275	# utility function to dup a filehandle. this is used by many backends
		1276	# to support binding more than one watcher per filehandle (they usually
		1277	# allow only one watcher per fd, so we dup it to get a different one).
		1278	sub _dupfh($$;$$) {
		1279	my ($poll, $fh, $r, $w) = @_;
		1280
		1281	# cygwin requires the fh mode to be matching, unix doesn't
		1282	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1283
		1284	open my $fh2, $mode, $fh
		1285	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1286
		1287	# we assume CLOEXEC is already set by perl in all important cases
		1288
		1289	($fh2, $rw)
		1290	}
		1291
		1292	#############################################################################
		1293	# "new" API, currently only emulation of it
		1294	#############################################################################
		1295
		1296	package AE;
		1297
		1298	sub io($$$) {
		1299	AnyEvent->io (fh => $_[0], poll => $_[1] ? "w" : "r", cb => $_[2])
		1300	}
		1301
		1302	sub timer($$$) {
		1303	AnyEvent->timer (after => $_[0], interval => $_[1], cb => $_[2]);
		1304	}
		1305
		1306	sub signal($$) {
		1307	AnyEvent->signal (signal => $_[0], cb => $_[1]);
		1308	}
		1309
		1310	sub child($$) {
		1311	AnyEvent->child (pid => $_[0], cb => $_[1]);
		1312	}
		1313
		1314	sub idle($) {
		1315	AnyEvent->idle (cb => $_[0]);
		1316	}
		1317
		1318	sub cv(;&) {
		1319	AnyEvent->condvar (@_ ? (cb => $_[0]) : ())
		1320	}
		1321
		1322	sub now() {
		1323	AnyEvent->now
		1324	}
		1325
		1326	sub now_update() {
		1327	AnyEvent->now_update
		1328	}
		1329
		1330	sub time() {
		1331	AnyEvent->time
		1332	}
		1333
814	package AnyEvent::Base;	1334	package AnyEvent::Base;
815		1335
		1336	# default implementations for many methods
		1337
		1338	sub _time {
		1339	# probe for availability of Time::HiRes
		1340	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1341	warn "AnyEvent: using Time::HiRes for sub-second timing accuracy.\n" if $VERBOSE >= 8;
		1342	*_time = \&Time::HiRes::time;
		1343	# if (eval "use POSIX (); (POSIX::times())...
		1344	} else {
		1345	warn "AnyEvent: using built-in time(), WARNING, no sub-second resolution!\n" if $VERBOSE;
		1346	*_time = sub { time }; # epic fail
		1347	}
		1348
		1349	&_time
		1350	}
		1351
		1352	sub time { _time }
		1353	sub now { _time }
		1354	sub now_update { }
		1355
816	# default implementation for ->condvar, ->wait, ->broadcast	1356	# default implementation for ->condvar
817		1357
818	sub condvar {	1358	sub condvar {
819	bless \my $flag, "AnyEvent::Base::CondVar"	1359	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
820	}
821
822	sub AnyEvent::Base::CondVar::broadcast {
823	${$_[0]}++;
824	}
825
826	sub AnyEvent::Base::CondVar::wait {
827	AnyEvent->one_event while !${$_[0]};
828	}	1360	}
829		1361
830	# default implementation for ->signal	1362	# default implementation for ->signal
831		1363
832	our %SIG_CB;	1364	our $HAVE_ASYNC_INTERRUPT;
		1365
		1366	sub _have_async_interrupt() {
		1367	$HAVE_ASYNC_INTERRUPT = 1*(!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT}
		1368	&& eval "use Async::Interrupt 1.0 (); 1")
		1369	unless defined $HAVE_ASYNC_INTERRUPT;
		1370
		1371	$HAVE_ASYNC_INTERRUPT
		1372	}
		1373
		1374	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1375	our (%SIG_ASY, %SIG_ASY_W);
		1376	our ($SIG_COUNT, $SIG_TW);
		1377
		1378	sub _signal_exec {
		1379	$HAVE_ASYNC_INTERRUPT
		1380	? $SIGPIPE_R->drain
		1381	: sysread $SIGPIPE_R, my $dummy, 9;
		1382
		1383	while (%SIG_EV) {
		1384	for (keys %SIG_EV) {
		1385	delete $SIG_EV{$_};
		1386	$_->() for values %{ $SIG_CB{$_} || {} };
		1387	}
		1388	}
		1389	}
		1390
		1391	# install a dummy wakeup watcher to reduce signal catching latency
		1392	sub _sig_add() {
		1393	unless ($SIG_COUNT++) {
		1394	# try to align timer on a full-second boundary, if possible
		1395	my $NOW = AE::now;
		1396
		1397	$SIG_TW = AE::timer
		1398	$MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1399	$MAX_SIGNAL_LATENCY,
		1400	sub { } # just for the PERL_ASYNC_CHECK
		1401	;
		1402	}
		1403	}
		1404
		1405	sub _sig_del {
		1406	undef $SIG_TW
		1407	unless --$SIG_COUNT;
		1408	}
		1409
		1410	our $_sig_name_init; $_sig_name_init = sub {
		1411	eval q{ # poor man's autoloading
		1412	undef $_sig_name_init;
		1413
		1414	if (_have_async_interrupt) {
		1415	*sig2num = \&Async::Interrupt::sig2num;
		1416	*sig2name = \&Async::Interrupt::sig2name;
		1417	} else {
		1418	require Config;
		1419
		1420	my %signame2num;
		1421	@signame2num{ split ' ', $Config::Config{sig_name} }
		1422	= split ' ', $Config::Config{sig_num};
		1423
		1424	my @signum2name;
		1425	@signum2name[values %signame2num] = keys %signame2num;
		1426
		1427	*sig2num = sub($) {
		1428	$_[0] > 0 ? shift : $signame2num{+shift}
		1429	};
		1430	*sig2name = sub ($) {
		1431	$_[0] > 0 ? $signum2name[+shift] : shift
		1432	};
		1433	}
		1434	};
		1435	die if $@;
		1436	};
		1437
		1438	sub sig2num ($) { &$_sig_name_init; &sig2num }
		1439	sub sig2name($) { &$_sig_name_init; &sig2name }
833		1440
834	sub signal {	1441	sub signal {
		1442	eval q{ # poor man's autoloading {}
		1443	# probe for availability of Async::Interrupt
		1444	if (_have_async_interrupt) {
		1445	warn "AnyEvent: using Async::Interrupt for race-free signal handling.\n" if $VERBOSE >= 8;
		1446
		1447	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1448	$SIG_IO = AE::io $SIGPIPE_R->fileno, 0, \&_signal_exec;
		1449
		1450	} else {
		1451	warn "AnyEvent: using emulated perl signal handling with latency timer.\n" if $VERBOSE >= 8;
		1452
		1453	require Fcntl;
		1454
		1455	if (AnyEvent::WIN32) {
		1456	require AnyEvent::Util;
		1457
		1458	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1459	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R, 1) if $SIGPIPE_R;
		1460	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W, 1) if $SIGPIPE_W; # just in case
		1461	} else {
		1462	pipe $SIGPIPE_R, $SIGPIPE_W;
		1463	fcntl $SIGPIPE_R, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_R;
		1464	fcntl $SIGPIPE_W, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_W; # just in case
		1465
		1466	# not strictly required, as $^F is normally 2, but let's make sure...
		1467	fcntl $SIGPIPE_R, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1468	fcntl $SIGPIPE_W, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1469	}
		1470
		1471	$SIGPIPE_R
		1472	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1473
		1474	$SIG_IO = AE::io $SIGPIPE_R, 0, \&_signal_exec;
		1475	}
		1476
		1477	*signal = sub {
835	my (undef, %arg) = @_;	1478	my (undef, %arg) = @_;
836		1479
837	my $signal = uc $arg{signal}	1480	my $signal = uc $arg{signal}
838	or Carp::croak "required option 'signal' is missing";	1481	or Carp::croak "required option 'signal' is missing";
839		1482
		1483	if ($HAVE_ASYNC_INTERRUPT) {
		1484	# async::interrupt
		1485
		1486	$signal = sig2num $signal;
840	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1487	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1488
		1489	$SIG_ASY{$signal} ||= new Async::Interrupt
		1490	cb => sub { undef $SIG_EV{$signal} },
		1491	signal => $signal,
		1492	pipe => [$SIGPIPE_R->filenos],
		1493	pipe_autodrain => 0,
		1494	;
		1495
		1496	} else {
		1497	# pure perl
		1498
		1499	# AE::Util has been loaded in signal
		1500	$signal = sig2name $signal;
		1501	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1502
841	$SIG{$signal} ||= sub {	1503	$SIG{$signal} ||= sub {
842	$_->() for values %{ $SIG_CB{$signal} || {} };	1504	local $!;
		1505	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1506	undef $SIG_EV{$signal};
		1507	};
		1508
		1509	# can't do signal processing without introducing races in pure perl,
		1510	# so limit the signal latency.
		1511	_sig_add;
		1512	}
		1513
		1514	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1515	};
		1516
		1517	*AnyEvent::Base::signal::DESTROY = sub {
		1518	my ($signal, $cb) = @{$_[0]};
		1519
		1520	_sig_del;
		1521
		1522	delete $SIG_CB{$signal}{$cb};
		1523
		1524	$HAVE_ASYNC_INTERRUPT
		1525	? delete $SIG_ASY{$signal}
		1526	: # delete doesn't work with older perls - they then
		1527	# print weird messages, or just unconditionally exit
		1528	# instead of getting the default action.
		1529	undef $SIG{$signal}
		1530	unless keys %{ $SIG_CB{$signal} };
		1531	};
843	};	1532	};
844		1533	die if $@;
845	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1534	&signal
846	}
847
848	sub AnyEvent::Base::Signal::DESTROY {
849	my ($signal, $cb) = @{$_[0]};
850
851	delete $SIG_CB{$signal}{$cb};
852
853	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };
854	}	1535	}
855		1536
856	# default implementation for ->child	1537	# default implementation for ->child
857		1538
858	our %PID_CB;	1539	our %PID_CB;
859	our $CHLD_W;	1540	our $CHLD_W;
860	our $CHLD_DELAY_W;	1541	our $CHLD_DELAY_W;
861	our $PID_IDLE;
862	our $WNOHANG;	1542	our $WNOHANG;
863		1543
864	sub _child_wait {	1544	sub _emit_childstatus($$) {
865	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1545	my (undef, $rpid, $rstatus) = @_;
		1546
		1547	$_->($rpid, $rstatus)
866	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1548	for values %{ $PID_CB{$rpid} || {} },
867	(values %{ $PID_CB{0} || {} });	1549	values %{ $PID_CB{0} || {} };
868	}
869
870	undef $PID_IDLE;
871	}	1550	}
872		1551
873	sub _sigchld {	1552	sub _sigchld {
874	# make sure we deliver these changes "synchronous" with the event loop.	1553	my $pid;
875	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {	1554
876	undef $CHLD_DELAY_W;	1555	AnyEvent->_emit_childstatus ($pid, $?)
877	&_child_wait;	1556	while ($pid = waitpid -1, $WNOHANG) > 0;
878	});
879	}	1557	}
880		1558
881	sub child {	1559	sub child {
882	my (undef, %arg) = @_;	1560	my (undef, %arg) = @_;
883		1561
884	defined (my $pid = $arg{pid} + 0)	1562	defined (my $pid = $arg{pid} + 0)
885	or Carp::croak "required option 'pid' is missing";	1563	or Carp::croak "required option 'pid' is missing";
886		1564
887	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1565	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
888		1566
889	unless ($WNOHANG) {	1567	# WNOHANG is almost cetrainly 1 everywhere
890	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;	1568	$WNOHANG ||= $^O =~ /^(?:openbsd|netbsd|linux|freebsd|cygwin|MSWin32)$/
891	}	1569	? 1
		1570	: eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
892		1571
893	unless ($CHLD_W) {	1572	unless ($CHLD_W) {
894	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1573	$CHLD_W = AE::signal CHLD => \&_sigchld;
895	# child could be a zombie already, so make at least one round	1574	# child could be a zombie already, so make at least one round
896	&_sigchld;	1575	&_sigchld;
897	}	1576	}
898		1577
899	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	1578	bless [$pid, $arg{cb}], "AnyEvent::Base::child"
900	}	1579	}
901		1580
902	sub AnyEvent::Base::Child::DESTROY {	1581	sub AnyEvent::Base::child::DESTROY {
903	my ($pid, $cb) = @{$_[0]};	1582	my ($pid, $cb) = @{$_[0]};
904		1583
905	delete $PID_CB{$pid}{$cb};	1584	delete $PID_CB{$pid}{$cb};
906	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1585	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
907		1586
908	undef $CHLD_W unless keys %PID_CB;	1587	undef $CHLD_W unless keys %PID_CB;
909	}	1588	}
		1589
		1590	# idle emulation is done by simply using a timer, regardless
		1591	# of whether the process is idle or not, and not letting
		1592	# the callback use more than 50% of the time.
		1593	sub idle {
		1594	my (undef, %arg) = @_;
		1595
		1596	my ($cb, $w, $rcb) = $arg{cb};
		1597
		1598	$rcb = sub {
		1599	if ($cb) {
		1600	$w = _time;
		1601	&$cb;
		1602	$w = _time - $w;
		1603
		1604	# never use more then 50% of the time for the idle watcher,
		1605	# within some limits
		1606	$w = 0.0001 if $w < 0.0001;
		1607	$w = 5 if $w > 5;
		1608
		1609	$w = AE::timer $w, 0, $rcb;
		1610	} else {
		1611	# clean up...
		1612	undef $w;
		1613	undef $rcb;
		1614	}
		1615	};
		1616
		1617	$w = AE::timer 0.05, 0, $rcb;
		1618
		1619	bless \\$cb, "AnyEvent::Base::idle"
		1620	}
		1621
		1622	sub AnyEvent::Base::idle::DESTROY {
		1623	undef $${$_[0]};
		1624	}
		1625
		1626	package AnyEvent::CondVar;
		1627
		1628	our @ISA = AnyEvent::CondVar::Base::;
		1629
		1630	package AnyEvent::CondVar::Base;
		1631
		1632	#use overload
		1633	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1634	# fallback => 1;
		1635
		1636	# save 300+ kilobytes by dirtily hardcoding overloading
		1637	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1638	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1639	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1640	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1641
		1642	our $WAITING;
		1643
		1644	sub _send {
		1645	# nop
		1646	}
		1647
		1648	sub send {
		1649	my $cv = shift;
		1650	$cv->{_ae_sent} = [@_];
		1651	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1652	$cv->_send;
		1653	}
		1654
		1655	sub croak {
		1656	$_[0]{_ae_croak} = $_[1];
		1657	$_[0]->send;
		1658	}
		1659
		1660	sub ready {
		1661	$_[0]{_ae_sent}
		1662	}
		1663
		1664	sub _wait {
		1665	$WAITING
		1666	and !$_[0]{_ae_sent}
		1667	and Carp::croak "AnyEvent::CondVar: recursive blocking wait detected";
		1668
		1669	local $WAITING = 1;
		1670	AnyEvent->one_event while !$_[0]{_ae_sent};
		1671	}
		1672
		1673	sub recv {
		1674	$_[0]->_wait;
		1675
		1676	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
		1677	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
		1678	}
		1679
		1680	sub cb {
		1681	my $cv = shift;
		1682
		1683	@_
		1684	and $cv->{_ae_cb} = shift
		1685	and $cv->{_ae_sent}
		1686	and (delete $cv->{_ae_cb})->($cv);
		1687
		1688	$cv->{_ae_cb}
		1689	}
		1690
		1691	sub begin {
		1692	++$_[0]{_ae_counter};
		1693	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
		1694	}
		1695
		1696	sub end {
		1697	return if --$_[0]{_ae_counter};
		1698	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		1699	}
		1700
		1701	# undocumented/compatibility with pre-3.4
		1702	*broadcast = \&send;
		1703	*wait = \&_wait;
		1704
		1705	=head1 ERROR AND EXCEPTION HANDLING
		1706
		1707	In general, AnyEvent does not do any error handling - it relies on the
		1708	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1709	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1710	checking of all AnyEvent methods, however, which is highly useful during
		1711	development.
		1712
		1713	As for exception handling (i.e. runtime errors and exceptions thrown while
		1714	executing a callback), this is not only highly event-loop specific, but
		1715	also not in any way wrapped by this module, as this is the job of the main
		1716	program.
		1717
		1718	The pure perl event loop simply re-throws the exception (usually
		1719	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1720	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1721	so on.
		1722
		1723	=head1 ENVIRONMENT VARIABLES
		1724
		1725	The following environment variables are used by this module or its
		1726	submodules.
		1727
		1728	Note that AnyEvent will remove I<all> environment variables starting with
		1729	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		1730	enabled.
		1731
		1732	=over 4
		1733
		1734	=item C<PERL_ANYEVENT_VERBOSE>
		1735
		1736	By default, AnyEvent will be completely silent except in fatal
		1737	conditions. You can set this environment variable to make AnyEvent more
		1738	talkative.
		1739
		1740	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1741	conditions, such as not being able to load the event model specified by
		1742	C<PERL_ANYEVENT_MODEL>.
		1743
		1744	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1745	model it chooses.
		1746
		1747	When set to C<8> or higher, then AnyEvent will report extra information on
		1748	which optional modules it loads and how it implements certain features.
		1749
		1750	=item C<PERL_ANYEVENT_STRICT>
		1751
		1752	AnyEvent does not do much argument checking by default, as thorough
		1753	argument checking is very costly. Setting this variable to a true value
		1754	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1755	check the arguments passed to most method calls. If it finds any problems,
		1756	it will croak.
		1757
		1758	In other words, enables "strict" mode.
		1759
		1760	Unlike C<use strict> (or it's modern cousin, C<< use L<common::sense>
		1761	>>, it is definitely recommended to keep it off in production. Keeping
		1762	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		1763	can be very useful, however.
		1764
		1765	=item C<PERL_ANYEVENT_MODEL>
		1766
		1767	This can be used to specify the event model to be used by AnyEvent, before
		1768	auto detection and -probing kicks in. It must be a string consisting
		1769	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1770	and the resulting module name is loaded and if the load was successful,
		1771	used as event model. If it fails to load AnyEvent will proceed with
		1772	auto detection and -probing.
		1773
		1774	This functionality might change in future versions.
		1775
		1776	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1777	could start your program like this:
		1778
		1779	PERL_ANYEVENT_MODEL=Perl perl ...
		1780
		1781	=item C<PERL_ANYEVENT_PROTOCOLS>
		1782
		1783	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1784	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1785	of auto probing).
		1786
		1787	Must be set to a comma-separated list of protocols or address families,
		1788	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1789	used, and preference will be given to protocols mentioned earlier in the
		1790	list.
		1791
		1792	This variable can effectively be used for denial-of-service attacks
		1793	against local programs (e.g. when setuid), although the impact is likely
		1794	small, as the program has to handle conenction and other failures anyways.
		1795
		1796	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1797	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1798	- only support IPv4, never try to resolve or contact IPv6
		1799	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1800	IPv6, but prefer IPv6 over IPv4.
		1801
		1802	=item C<PERL_ANYEVENT_EDNS0>
		1803
		1804	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1805	for DNS. This extension is generally useful to reduce DNS traffic, but
		1806	some (broken) firewalls drop such DNS packets, which is why it is off by
		1807	default.
		1808
		1809	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1810	EDNS0 in its DNS requests.
		1811
		1812	=item C<PERL_ANYEVENT_MAX_FORKS>
		1813
		1814	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1815	will create in parallel.
		1816
		1817	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		1818
		1819	The default value for the C<max_outstanding> parameter for the default DNS
		1820	resolver - this is the maximum number of parallel DNS requests that are
		1821	sent to the DNS server.
		1822
		1823	=item C<PERL_ANYEVENT_RESOLV_CONF>
		1824
		1825	The file to use instead of F</etc/resolv.conf> (or OS-specific
		1826	configuration) in the default resolver. When set to the empty string, no
		1827	default config will be used.
		1828
		1829	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		1830
		1831	When neither C<ca_file> nor C<ca_path> was specified during
		1832	L<AnyEvent::TLS> context creation, and either of these environment
		1833	variables exist, they will be used to specify CA certificate locations
		1834	instead of a system-dependent default.
		1835
		1836	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		1837
		1838	When these are set to C<1>, then the respective modules are not
		1839	loaded. Mostly good for testing AnyEvent itself.
		1840
		1841	=back
910		1842
911	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1843	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
912		1844
913	This is an advanced topic that you do not normally need to use AnyEvent in	1845	This is an advanced topic that you do not normally need to use AnyEvent in
914	a module. This section is only of use to event loop authors who want to	1846	a module. This section is only of use to event loop authors who want to
…		…
948		1880
949	I<rxvt-unicode> also cheats a bit by not providing blocking access to	1881	I<rxvt-unicode> also cheats a bit by not providing blocking access to
950	condition variables: code blocking while waiting for a condition will	1882	condition variables: code blocking while waiting for a condition will
951	C<die>. This still works with most modules/usages, and blocking calls must	1883	C<die>. This still works with most modules/usages, and blocking calls must
952	not be done in an interactive application, so it makes sense.	1884	not be done in an interactive application, so it makes sense.
953
954	=head1 ENVIRONMENT VARIABLES
955
956	The following environment variables are used by this module:
957
958	=over 4
959
960	=item C<PERL_ANYEVENT_VERBOSE>
961
962	By default, AnyEvent will be completely silent except in fatal
963	conditions. You can set this environment variable to make AnyEvent more
964	talkative.
965
966	When set to C<1> or higher, causes AnyEvent to warn about unexpected
967	conditions, such as not being able to load the event model specified by
968	C<PERL_ANYEVENT_MODEL>.
969
970	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
971	model it chooses.
972
973	=item C<PERL_ANYEVENT_MODEL>
974
975	This can be used to specify the event model to be used by AnyEvent, before
976	autodetection and -probing kicks in. It must be a string consisting
977	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
978	and the resulting module name is loaded and if the load was successful,
979	used as event model. If it fails to load AnyEvent will proceed with
980	autodetection and -probing.
981
982	This functionality might change in future versions.
983
984	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
985	could start your program like this:
986
987	PERL_ANYEVENT_MODEL=Perl perl ...
988
989	=back
990		1885
991	=head1 EXAMPLE PROGRAM	1886	=head1 EXAMPLE PROGRAM
992		1887
993	The following program uses an I/O watcher to read data from STDIN, a timer	1888	The following program uses an I/O watcher to read data from STDIN, a timer
994	to display a message once per second, and a condition variable to quit the	1889	to display a message once per second, and a condition variable to quit the
…		…
1003	poll => 'r',	1898	poll => 'r',
1004	cb => sub {	1899	cb => sub {
1005	warn "io event <$_[0]>\n"; # will always output <r>	1900	warn "io event <$_[0]>\n"; # will always output <r>
1006	chomp (my $input = <STDIN>); # read a line	1901	chomp (my $input = <STDIN>); # read a line
1007	warn "read: $input\n"; # output what has been read	1902	warn "read: $input\n"; # output what has been read
1008	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	1903	$cv->send if $input =~ /^q/i; # quit program if /^q/i
1009	},	1904	},
1010	);	1905	);
1011		1906
1012	my $time_watcher; # can only be used once	1907	my $time_watcher; # can only be used once
1013		1908
…		…
1018	});	1913	});
1019	}	1914	}
1020		1915
1021	new_timer; # create first timer	1916	new_timer; # create first timer
1022		1917
1023	$cv->wait; # wait until user enters /^q/i	1918	$cv->recv; # wait until user enters /^q/i
1024		1919
1025	=head1 REAL-WORLD EXAMPLE	1920	=head1 REAL-WORLD EXAMPLE
1026		1921
1027	Consider the L<Net::FCP> module. It features (among others) the following	1922	Consider the L<Net::FCP> module. It features (among others) the following
1028	API calls, which are to freenet what HTTP GET requests are to http:	1923	API calls, which are to freenet what HTTP GET requests are to http:
…		…
1078	syswrite $txn->{fh}, $txn->{request}	1973	syswrite $txn->{fh}, $txn->{request}
1079	or die "connection or write error";	1974	or die "connection or write error";
1080	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	1975	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
1081		1976
1082	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	1977	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
1083	result and signals any possible waiters that the request ahs finished:	1978	result and signals any possible waiters that the request has finished:
1084		1979
1085	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	1980	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
1086		1981
1087	if (end-of-file or data complete) {	1982	if (end-of-file or data complete) {
1088	$txn->{result} = $txn->{buf};	1983	$txn->{result} = $txn->{buf};
1089	$txn->{finished}->broadcast;	1984	$txn->{finished}->send;
1090	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	1985	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
1091	}	1986	}
1092		1987
1093	The C<result> method, finally, just waits for the finished signal (if the	1988	The C<result> method, finally, just waits for the finished signal (if the
1094	request was already finished, it doesn't wait, of course, and returns the	1989	request was already finished, it doesn't wait, of course, and returns the
1095	data:	1990	data:
1096		1991
1097	$txn->{finished}->wait;	1992	$txn->{finished}->recv;
1098	return $txn->{result};	1993	return $txn->{result};
1099		1994
1100	The actual code goes further and collects all errors (C<die>s, exceptions)	1995	The actual code goes further and collects all errors (C<die>s, exceptions)
1101	that occured during request processing. The C<result> method detects	1996	that occurred during request processing. The C<result> method detects
1102	whether an exception as thrown (it is stored inside the $txn object)	1997	whether an exception as thrown (it is stored inside the $txn object)
1103	and just throws the exception, which means connection errors and other	1998	and just throws the exception, which means connection errors and other
1104	problems get reported tot he code that tries to use the result, not in a	1999	problems get reported tot he code that tries to use the result, not in a
1105	random callback.	2000	random callback.
1106		2001
…		…
1137		2032
1138	my $quit = AnyEvent->condvar;	2033	my $quit = AnyEvent->condvar;
1139		2034
1140	$fcp->txn_client_get ($url)->cb (sub {	2035	$fcp->txn_client_get ($url)->cb (sub {
1141	...	2036	...
1142	$quit->broadcast;	2037	$quit->send;
1143	});	2038	});
1144		2039
1145	$quit->wait;	2040	$quit->recv;
1146		2041
1147		2042
1148	=head1 BENCHMARKS	2043	=head1 BENCHMARKS
1149		2044
1150	To give you an idea of the performance and overheads that AnyEvent adds	2045	To give you an idea of the performance and overheads that AnyEvent adds
…		…
1152	of various event loops I prepared some benchmarks.	2047	of various event loops I prepared some benchmarks.
1153		2048
1154	=head2 BENCHMARKING ANYEVENT OVERHEAD	2049	=head2 BENCHMARKING ANYEVENT OVERHEAD
1155		2050
1156	Here is a benchmark of various supported event models used natively and	2051	Here is a benchmark of various supported event models used natively and
1157	through anyevent. The benchmark creates a lot of timers (with a zero	2052	through AnyEvent. The benchmark creates a lot of timers (with a zero
1158	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,	2053	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
1159	which it is), lets them fire exactly once and destroys them again.	2054	which it is), lets them fire exactly once and destroys them again.
1160		2055
1161	Source code for this benchmark is found as F<eg/bench> in the AnyEvent	2056	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
1162	distribution.	2057	distribution.
…		…
1179	all watchers, to avoid adding memory overhead. That means closure creation	2074	all watchers, to avoid adding memory overhead. That means closure creation
1180	and memory usage is not included in the figures.	2075	and memory usage is not included in the figures.
1181		2076
1182	I<invoke> is the time, in microseconds, used to invoke a simple	2077	I<invoke> is the time, in microseconds, used to invoke a simple
1183	callback. The callback simply counts down a Perl variable and after it was	2078	callback. The callback simply counts down a Perl variable and after it was
1184	invoked "watcher" times, it would C<< ->broadcast >> a condvar once to	2079	invoked "watcher" times, it would C<< ->send >> a condvar once to
1185	signal the end of this phase.	2080	signal the end of this phase.
1186		2081
1187	I<destroy> is the time, in microseconds, that it takes to destroy a single	2082	I<destroy> is the time, in microseconds, that it takes to destroy a single
1188	watcher.	2083	watcher.
1189		2084
1190	=head3 Results	2085	=head3 Results
1191		2086
1192	name watchers bytes create invoke destroy comment	2087	name watchers bytes create invoke destroy comment
1193	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	2088	EV/EV 400000 224 0.47 0.35 0.27 EV native interface
1194	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	2089	EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers
1195	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	2090	CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal
1196	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	2091	Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation
1197	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	2092	Event/Event 16000 517 32.20 31.80 0.81 Event native interface
1198	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers	2093	Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers
		2094	IOAsync/Any 16000 989 38.10 32.77 11.13 via IO::Async::Loop::IO_Poll
		2095	IOAsync/Any 16000 990 37.59 29.50 10.61 via IO::Async::Loop::Epoll
1199	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	2096	Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour
1200	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	2097	Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers
1201	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	2098	POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event
1202	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	2099	POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select
1203		2100
1204	=head3 Discussion	2101	=head3 Discussion
1205		2102
1206	The benchmark does I<not> measure scalability of the event loop very	2103	The benchmark does I<not> measure scalability of the event loop very
1207	well. For example, a select-based event loop (such as the pure perl one)	2104	well. For example, a select-based event loop (such as the pure perl one)
…		…
1232	performance becomes really bad with lots of file descriptors (and few of	2129	performance becomes really bad with lots of file descriptors (and few of
1233	them active), of course, but this was not subject of this benchmark.	2130	them active), of course, but this was not subject of this benchmark.
1234		2131
1235	The C<Event> module has a relatively high setup and callback invocation	2132	The C<Event> module has a relatively high setup and callback invocation
1236	cost, but overall scores in on the third place.	2133	cost, but overall scores in on the third place.
		2134
		2135	C<IO::Async> performs admirably well, about on par with C<Event>, even
		2136	when using its pure perl backend.
1237		2137
1238	C<Glib>'s memory usage is quite a bit higher, but it features a	2138	C<Glib>'s memory usage is quite a bit higher, but it features a
1239	faster callback invocation and overall ends up in the same class as	2139	faster callback invocation and overall ends up in the same class as
1240	C<Event>. However, Glib scales extremely badly, doubling the number of	2140	C<Event>. However, Glib scales extremely badly, doubling the number of
1241	watchers increases the processing time by more than a factor of four,	2141	watchers increases the processing time by more than a factor of four,
…		…
1285		2185
1286	=back	2186	=back
1287		2187
1288	=head2 BENCHMARKING THE LARGE SERVER CASE	2188	=head2 BENCHMARKING THE LARGE SERVER CASE
1289		2189
1290	This benchmark atcually benchmarks the event loop itself. It works by	2190	This benchmark actually benchmarks the event loop itself. It works by
1291	creating a number of "servers": each server consists of a socketpair, a	2191	creating a number of "servers": each server consists of a socket pair, a
1292	timeout watcher that gets reset on activity (but never fires), and an I/O	2192	timeout watcher that gets reset on activity (but never fires), and an I/O
1293	watcher waiting for input on one side of the socket. Each time the socket	2193	watcher waiting for input on one side of the socket. Each time the socket
1294	watcher reads a byte it will write that byte to a random other "server".	2194	watcher reads a byte it will write that byte to a random other "server".
1295		2195
1296	The effect is that there will be a lot of I/O watchers, only part of which	2196	The effect is that there will be a lot of I/O watchers, only part of which
1297	are active at any one point (so there is a constant number of active	2197	are active at any one point (so there is a constant number of active
1298	fds for each loop iterstaion, but which fds these are is random). The	2198	fds for each loop iteration, but which fds these are is random). The
1299	timeout is reset each time something is read because that reflects how	2199	timeout is reset each time something is read because that reflects how
1300	most timeouts work (and puts extra pressure on the event loops).	2200	most timeouts work (and puts extra pressure on the event loops).
1301		2201
1302	In this benchmark, we use 10000 socketpairs (20000 sockets), of which 100	2202	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
1303	(1%) are active. This mirrors the activity of large servers with many	2203	(1%) are active. This mirrors the activity of large servers with many
1304	connections, most of which are idle at any one point in time.	2204	connections, most of which are idle at any one point in time.
1305		2205
1306	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent	2206	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
1307	distribution.	2207	distribution.
…		…
1309	=head3 Explanation of the columns	2209	=head3 Explanation of the columns
1310		2210
1311	I<sockets> is the number of sockets, and twice the number of "servers" (as	2211	I<sockets> is the number of sockets, and twice the number of "servers" (as
1312	each server has a read and write socket end).	2212	each server has a read and write socket end).
1313		2213
1314	I<create> is the time it takes to create a socketpair (which is	2214	I<create> is the time it takes to create a socket pair (which is
1315	nontrivial) and two watchers: an I/O watcher and a timeout watcher.	2215	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
1316		2216
1317	I<request>, the most important value, is the time it takes to handle a	2217	I<request>, the most important value, is the time it takes to handle a
1318	single "request", that is, reading the token from the pipe and forwarding	2218	single "request", that is, reading the token from the pipe and forwarding
1319	it to another server. This includes deleting the old timeout and creating	2219	it to another server. This includes deleting the old timeout and creating
1320	a new one that moves the timeout into the future.	2220	a new one that moves the timeout into the future.
1321		2221
1322	=head3 Results	2222	=head3 Results
1323		2223
1324	name sockets create request	2224	name sockets create request
1325	EV 20000 69.01 11.16	2225	EV 20000 69.01 11.16
1326	Perl 20000 73.32 35.87	2226	Perl 20000 73.32 35.87
		2227	IOAsync 20000 157.00 98.14 epoll
		2228	IOAsync 20000 159.31 616.06 poll
1327	Event 20000 212.62 257.32	2229	Event 20000 212.62 257.32
1328	Glib 20000 651.16 1896.30	2230	Glib 20000 651.16 1896.30
1329	POE 20000 349.67 12317.24 uses POE::Loop::Event	2231	POE 20000 349.67 12317.24 uses POE::Loop::Event
1330		2232
1331	=head3 Discussion	2233	=head3 Discussion
1332		2234
1333	This benchmark I<does> measure scalability and overall performance of the	2235	This benchmark I<does> measure scalability and overall performance of the
1334	particular event loop.	2236	particular event loop.
…		…
1336	EV is again fastest. Since it is using epoll on my system, the setup time	2238	EV is again fastest. Since it is using epoll on my system, the setup time
1337	is relatively high, though.	2239	is relatively high, though.
1338		2240
1339	Perl surprisingly comes second. It is much faster than the C-based event	2241	Perl surprisingly comes second. It is much faster than the C-based event
1340	loops Event and Glib.	2242	loops Event and Glib.
		2243
		2244	IO::Async performs very well when using its epoll backend, and still quite
		2245	good compared to Glib when using its pure perl backend.
1341		2246
1342	Event suffers from high setup time as well (look at its code and you will	2247	Event suffers from high setup time as well (look at its code and you will
1343	understand why). Callback invocation also has a high overhead compared to	2248	understand why). Callback invocation also has a high overhead compared to
1344	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event	2249	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
1345	uses select or poll in basically all documented configurations.	2250	uses select or poll in basically all documented configurations.
…		…
1392	speed most when you have lots of watchers, not when you only have a few of	2297	speed most when you have lots of watchers, not when you only have a few of
1393	them).	2298	them).
1394		2299
1395	EV is again fastest.	2300	EV is again fastest.
1396		2301
1397	Perl again comes second. It is noticably faster than the C-based event	2302	Perl again comes second. It is noticeably faster than the C-based event
1398	loops Event and Glib, although the difference is too small to really	2303	loops Event and Glib, although the difference is too small to really
1399	matter.	2304	matter.
1400		2305
1401	POE also performs much better in this case, but is is still far behind the	2306	POE also performs much better in this case, but is is still far behind the
1402	others.	2307	others.
…		…
1405		2310
1406	=over 4	2311	=over 4
1407		2312
1408	=item * C-based event loops perform very well with small number of	2313	=item * C-based event loops perform very well with small number of
1409	watchers, as the management overhead dominates.	2314	watchers, as the management overhead dominates.
		2315
		2316	=back
		2317
		2318	=head2 THE IO::Lambda BENCHMARK
		2319
		2320	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2321	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2322	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2323	shouldn't come as a surprise to anybody). As such, the benchmark is
		2324	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2325	very optimal. But how would AnyEvent compare when used without the extra
		2326	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2327
		2328	The benchmark itself creates an echo-server, and then, for 500 times,
		2329	connects to the echo server, sends a line, waits for the reply, and then
		2330	creates the next connection. This is a rather bad benchmark, as it doesn't
		2331	test the efficiency of the framework or much non-blocking I/O, but it is a
		2332	benchmark nevertheless.
		2333
		2334	name runtime
		2335	Lambda/select 0.330 sec
		2336	+ optimized 0.122 sec
		2337	Lambda/AnyEvent 0.327 sec
		2338	+ optimized 0.138 sec
		2339	Raw sockets/select 0.077 sec
		2340	POE/select, components 0.662 sec
		2341	POE/select, raw sockets 0.226 sec
		2342	POE/select, optimized 0.404 sec
		2343
		2344	AnyEvent/select/nb 0.085 sec
		2345	AnyEvent/EV/nb 0.068 sec
		2346	+state machine 0.134 sec
		2347
		2348	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2349	benchmarks actually make blocking connects and use 100% blocking I/O,
		2350	defeating the purpose of an event-based solution. All of the newly
		2351	written AnyEvent benchmarks use 100% non-blocking connects (using
		2352	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2353	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2354	generally require a lot more bookkeeping and event handling than blocking
		2355	connects (which involve a single syscall only).
		2356
		2357	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2358	offers similar expressive power as POE and IO::Lambda, using conventional
		2359	Perl syntax. This means that both the echo server and the client are 100%
		2360	non-blocking, further placing it at a disadvantage.
		2361
		2362	As you can see, the AnyEvent + EV combination even beats the
		2363	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2364	backend easily beats IO::Lambda and POE.
		2365
		2366	And even the 100% non-blocking version written using the high-level (and
		2367	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda by a
		2368	large margin, even though it does all of DNS, tcp-connect and socket I/O
		2369	in a non-blocking way.
		2370
		2371	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2372	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2373	part of the IO::lambda distribution and were used without any changes.
		2374
		2375
		2376	=head1 SIGNALS
		2377
		2378	AnyEvent currently installs handlers for these signals:
		2379
		2380	=over 4
		2381
		2382	=item SIGCHLD
		2383
		2384	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2385	emulation for event loops that do not support them natively. Also, some
		2386	event loops install a similar handler.
		2387
		2388	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2389	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2390
		2391	=item SIGPIPE
		2392
		2393	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2394	when AnyEvent gets loaded.
		2395
		2396	The rationale for this is that AnyEvent users usually do not really depend
		2397	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2398	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2399	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2400	some random socket.
		2401
		2402	The rationale for installing a no-op handler as opposed to ignoring it is
		2403	that this way, the handler will be restored to defaults on exec.
		2404
		2405	Feel free to install your own handler, or reset it to defaults.
		2406
		2407	=back
		2408
		2409	=cut
		2410
		2411	undef $SIG{CHLD}
		2412	if $SIG{CHLD} eq 'IGNORE';
		2413
		2414	$SIG{PIPE} = sub { }
		2415	unless defined $SIG{PIPE};
		2416
		2417	=head1 RECOMMENDED/OPTIONAL MODULES
		2418
		2419	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2420	it's built-in modules) are required to use it.
		2421
		2422	That does not mean that AnyEvent won't take advantage of some additional
		2423	modules if they are installed.
		2424
		2425	This section epxlains which additional modules will be used, and how they
		2426	affect AnyEvent's operetion.
		2427
		2428	=over 4
		2429
		2430	=item L<Async::Interrupt>
		2431
		2432	This slightly arcane module is used to implement fast signal handling: To
		2433	my knowledge, there is no way to do completely race-free and quick
		2434	signal handling in pure perl. To ensure that signals still get
		2435	delivered, AnyEvent will start an interval timer to wake up perl (and
		2436	catch the signals) with some delay (default is 10 seconds, look for
		2437	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2438
		2439	If this module is available, then it will be used to implement signal
		2440	catching, which means that signals will not be delayed, and the event loop
		2441	will not be interrupted regularly, which is more efficient (And good for
		2442	battery life on laptops).
		2443
		2444	This affects not just the pure-perl event loop, but also other event loops
		2445	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2446
		2447	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2448	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2449	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2450	does nothing for those backends.
		2451
		2452	=item L<EV>
		2453
		2454	This module isn't really "optional", as it is simply one of the backend
		2455	event loops that AnyEvent can use. However, it is simply the best event
		2456	loop available in terms of features, speed and stability: It supports
		2457	the AnyEvent API optimally, implements all the watcher types in XS, does
		2458	automatic timer adjustments even when no monotonic clock is available,
		2459	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2460	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2461	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2462
		2463	=item L<Guard>
		2464
		2465	The guard module, when used, will be used to implement
		2466	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2467	lot less memory), but otherwise doesn't affect guard operation much. It is
		2468	purely used for performance.
		2469
		2470	=item L<JSON> and L<JSON::XS>
		2471
		2472	This module is required when you want to read or write JSON data via
		2473	L<AnyEvent::Handle>. It is also written in pure-perl, but can take
		2474	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2475
		2476	In fact, L<AnyEvent::Handle> will use L<JSON::XS> by default if it is
		2477	installed.
		2478
		2479	=item L<Net::SSLeay>
		2480
		2481	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2482	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2483	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2484
		2485	=item L<Time::HiRes>
		2486
		2487	This module is part of perl since release 5.008. It will be used when the
		2488	chosen event library does not come with a timing source on it's own. The
		2489	pure-perl event loop (L<AnyEvent::Impl::Perl>) will additionally use it to
		2490	try to use a monotonic clock for timing stability.
1410		2491
1411	=back	2492	=back
1412		2493
1413		2494
1414	=head1 FORK	2495	=head1 FORK
…		…
1416	Most event libraries are not fork-safe. The ones who are usually are	2497	Most event libraries are not fork-safe. The ones who are usually are
1417	because they rely on inefficient but fork-safe C<select> or C<poll>	2498	because they rely on inefficient but fork-safe C<select> or C<poll>
1418	calls. Only L<EV> is fully fork-aware.	2499	calls. Only L<EV> is fully fork-aware.
1419		2500
1420	If you have to fork, you must either do so I<before> creating your first	2501	If you have to fork, you must either do so I<before> creating your first
1421	watcher OR you must not use AnyEvent at all in the child.	2502	watcher OR you must not use AnyEvent at all in the child OR you must do
		2503	something completely out of the scope of AnyEvent.
1422		2504
1423		2505
1424	=head1 SECURITY CONSIDERATIONS	2506	=head1 SECURITY CONSIDERATIONS
1425		2507
1426	AnyEvent can be forced to load any event model via	2508	AnyEvent can be forced to load any event model via
…		…
1431	specified in the variable.	2513	specified in the variable.
1432		2514
1433	You can make AnyEvent completely ignore this variable by deleting it	2515	You can make AnyEvent completely ignore this variable by deleting it
1434	before the first watcher gets created, e.g. with a C<BEGIN> block:	2516	before the first watcher gets created, e.g. with a C<BEGIN> block:
1435		2517
1436	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	2518	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1437		2519
1438	use AnyEvent;	2520	use AnyEvent;
1439		2521
1440	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can	2522	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1441	be used to probe what backend is used and gain other information (which is	2523	be used to probe what backend is used and gain other information (which is
1442	probably even less useful to an attacker than PERL_ANYEVENT_MODEL).	2524	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2525	$ENV{PERL_ANYEVENT_STRICT}.
		2526
		2527	Note that AnyEvent will remove I<all> environment variables starting with
		2528	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2529	enabled.
		2530
		2531
		2532	=head1 BUGS
		2533
		2534	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2535	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2536	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2537	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2538	pronounced).
1443		2539
1444		2540
1445	=head1 SEE ALSO	2541	=head1 SEE ALSO
		2542
		2543	Utility functions: L<AnyEvent::Util>.
1446		2544
1447	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,	2545	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
1448	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.	2546	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
1449		2547
1450	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,	2548	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
1451	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,	2549	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
1452	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,	2550	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1453	L<AnyEvent::Impl::POE>.	2551	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>, L<Anyevent::Impl::Irssi>.
1454		2552
		2553	Non-blocking file handles, sockets, TCP clients and
		2554	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
		2555
		2556	Asynchronous DNS: L<AnyEvent::DNS>.
		2557
1455	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,	2558	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>,
		2559	L<Coro::Event>,
1456		2560
1457	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	2561	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::XMPP>,
		2562	L<AnyEvent::HTTP>.
1458		2563
1459		2564
1460	=head1 AUTHOR	2565	=head1 AUTHOR
1461		2566
1462	Marc Lehmann <schmorp@schmorp.de>	2567	Marc Lehmann <schmorp@schmorp.de>
1463	http://home.schmorp.de/	2568	http://home.schmorp.de/
1464		2569
1465	=cut	2570	=cut
1466		2571
1467	1	2572	1
1468		2573

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