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Revision 1.242 by root, Fri Jul 17 22:05:12 2009 UTC

1	=head1 => NAME	1	=head1 NAME
2		2
3	AnyEvent - provide framework for multiple event loops	3	AnyEvent - provide framework for multiple event loops
4		4
5	EV, Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event loops	5	EV, Event, Glib, Tk, Perl, Event::Lib, Qt and POE are various supported
		6	event loops.
6		7
7	=head1 SYNOPSIS	8	=head1 SYNOPSIS
8		9
9	use AnyEvent;	10	use AnyEvent;
10		11
		12	# file descriptor readable
11	my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub {	13	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
		14
		15	# one-shot or repeating timers
		16	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
		17	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...
		18
		19	print AnyEvent->now; # prints current event loop time
		20	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
		21
		22	# POSIX signal
		23	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
		24
		25	# child process exit
		26	my $w = AnyEvent->child (pid => $pid, cb => sub {
		27	my ($pid, $status) = @_;
12	...	28	...
13	});	29	});
14		30
15	my $w = AnyEvent->timer (after => $seconds, cb => sub {	31	# called when event loop idle (if applicable)
16	...	32	my $w = AnyEvent->idle (cb => sub { ... });
17	});
18		33
19	my $w = AnyEvent->condvar; # stores whether a condition was flagged	34	my $w = AnyEvent->condvar; # stores whether a condition was flagged
20	$w->send; # wake up current and all future recv's	35	$w->send; # wake up current and all future recv's
21	$w->recv; # enters "main loop" till $condvar gets ->send	36	$w->recv; # enters "main loop" till $condvar gets ->send
		37	# use a condvar in callback mode:
		38	$w->cb (sub { $_[0]->recv });
		39
		40	=head1 INTRODUCTION/TUTORIAL
		41
		42	This manpage is mainly a reference manual. If you are interested
		43	in a tutorial or some gentle introduction, have a look at the
		44	L<AnyEvent::Intro> manpage.
22		45
23	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)	46	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
24		47
25	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	48	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
26	nowadays. So what is different about AnyEvent?	49	nowadays. So what is different about AnyEvent?
27		50
28	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of	51	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
29	policy> and AnyEvent is I<small and efficient>.	52	policy> and AnyEvent is I<small and efficient>.
30		53
31	First and foremost, I<AnyEvent is not an event model> itself, it only	54	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	55	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,	56	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,	57	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	58	only one event loop can be active at the same time in a process. AnyEvent
36	helps hiding the differences between those event loops.	59	cannot change this, but it can hide the differences between those event
		60	loops.
37		61
38	The goal of AnyEvent is to offer module authors the ability to do event	62	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	63	programming (waiting for I/O or timer events) without subscribing to a
40	religion, a way of living, and most importantly: without forcing your	64	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	65	module users into the same thing by forcing them to use the same event
42	model you use.	66	model you use.
43		67
44	For modules like POE or IO::Async (which is a total misnomer as it is	68	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	69	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	70	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	71	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	72	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.	73	module are I<also> forced to use the same event loop you use.
50		74
51	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	75	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
52	fine. AnyEvent + Tk works fine etc. etc. but none of these work together	76	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	77	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,	78	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	79	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	80	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	81	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).	82	to AnyEvent, too, so it is future-proof).
59		83
60	In addition to being free of having to use I<the one and only true event	84	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	85	model>, AnyEvent also is free of bloat and policy: with POE or similar
62	modules, you get an enormous amount of code and strict rules you have to	86	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	87	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	88	offering the functionality that is necessary, in as thin as a wrapper as
65	technically possible.	89	technically possible.
66		90
		91	Of course, AnyEvent comes with a big (and fully optional!) toolbox
		92	of useful functionality, such as an asynchronous DNS resolver, 100%
		93	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
		94	such as Windows) and lots of real-world knowledge and workarounds for
		95	platform bugs and differences.
		96
67	Of course, if you want lots of policy (this can arguably be somewhat	97	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	98	useful) and you want to force your users to use the one and only event
69	model, you should I<not> use this module.	99	model, you should I<not> use this module.
70		100
71	=head1 DESCRIPTION	101	=head1 DESCRIPTION
72		102
…		…
102	starts using it, all bets are off. Maybe you should tell their authors to	132	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...	133	use AnyEvent so their modules work together with others seamlessly...
104		134
105	The pure-perl implementation of AnyEvent is called	135	The pure-perl implementation of AnyEvent is called
106	C<AnyEvent::Impl::Perl>. Like other event modules you can load it	136	C<AnyEvent::Impl::Perl>. Like other event modules you can load it
107	explicitly.	137	explicitly and enjoy the high availability of that event loop :)
108		138
109	=head1 WATCHERS	139	=head1 WATCHERS
110		140
111	AnyEvent has the central concept of a I<watcher>, which is an object that	141	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	142	stores relevant data for each kind of event you are waiting for, such as
…		…
115	These watchers are normal Perl objects with normal Perl lifetime. After	145	These watchers are normal Perl objects with normal Perl lifetime. After
116	creating a watcher it will immediately "watch" for events and invoke the	146	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	147	callback when the event occurs (of course, only when the event model
118	is in control).	148	is in control).
119		149
		150	Note that B<callbacks must not permanently change global variables>
		151	potentially in use by the event loop (such as C<$_> or C<$[>) and that B<<
		152	callbacks must not C<die> >>. The former is good programming practise in
		153	Perl and the latter stems from the fact that exception handling differs
		154	widely between event loops.
		155
120	To disable the watcher you have to destroy it (e.g. by setting the	156	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	157	variable you store it in to C<undef> or otherwise deleting all references
122	to it).	158	to it).
123		159
124	All watchers are created by calling a method on the C<AnyEvent> class.	160	All watchers are created by calling a method on the C<AnyEvent> class.
…		…
126	Many watchers either are used with "recursion" (repeating timers for	162	Many watchers either are used with "recursion" (repeating timers for
127	example), or need to refer to their watcher object in other ways.	163	example), or need to refer to their watcher object in other ways.
128		164
129	An any way to achieve that is this pattern:	165	An any way to achieve that is this pattern:
130		166
131	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	167	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
132	# you can use $w here, for example to undef it	168	# you can use $w here, for example to undef it
133	undef $w;	169	undef $w;
134	});	170	});
135		171
136	Note that C<my $w; $w => combination. This is necessary because in Perl,	172	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	173	my variables are only visible after the statement in which they are
138	declared.	174	declared.
139		175
140	=head2 I/O WATCHERS	176	=head2 I/O WATCHERS
141		177
142	You can create an I/O watcher by calling the C<< AnyEvent->io >> method	178	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
143	with the following mandatory key-value pairs as arguments:	179	with the following mandatory key-value pairs as arguments:
144		180
145	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch	181	C<fh> is the Perl I<file handle> (or a naked file descriptor) to watch
		182	for events (AnyEvent might or might not keep a reference to this file
		183	handle). Note that only file handles pointing to things for which
		184	non-blocking operation makes sense are allowed. This includes sockets,
		185	most character devices, pipes, fifos and so on, but not for example files
		186	or block devices.
		187
146	for events. C<poll> must be a string that is either C<r> or C<w>,	188	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,	189	watcher waiting for "r"eadable or "w"ritable events, respectively.
		190
148	respectively. C<cb> is the callback to invoke each time the file handle	191	C<cb> is the callback to invoke each time the file handle becomes ready.
149	becomes ready.
150		192
151	Although the callback might get passed parameters, their value and	193	Although the callback might get passed parameters, their value and
152	presence is undefined and you cannot rely on them. Portable AnyEvent	194	presence is undefined and you cannot rely on them. Portable AnyEvent
153	callbacks cannot use arguments passed to I/O watcher callbacks.	195	callbacks cannot use arguments passed to I/O watcher callbacks.
154		196
…		…
158		200
159	Some event loops issue spurious readyness notifications, so you should	201	Some event loops issue spurious readyness notifications, so you should
160	always use non-blocking calls when reading/writing from/to your file	202	always use non-blocking calls when reading/writing from/to your file
161	handles.	203	handles.
162		204
163	Example:
164
165	# wait for readability of STDIN, then read a line and disable the watcher	205	Example: wait for readability of STDIN, then read a line and disable the
		206	watcher.
		207
166	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	208	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
167	chomp (my $input = <STDIN>);	209	chomp (my $input = <STDIN>);
168	warn "read: $input\n";	210	warn "read: $input\n";
169	undef $w;	211	undef $w;
170	});	212	});
…		…
180		222
181	Although the callback might get passed parameters, their value and	223	Although the callback might get passed parameters, their value and
182	presence is undefined and you cannot rely on them. Portable AnyEvent	224	presence is undefined and you cannot rely on them. Portable AnyEvent
183	callbacks cannot use arguments passed to time watcher callbacks.	225	callbacks cannot use arguments passed to time watcher callbacks.
184		226
185	The timer callback will be invoked at most once: if you want a repeating	227	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	228	parameter, C<interval>, as a strictly positive number (> 0), then the
187	and Glib).	229	callback will be invoked regularly at that interval (in fractional
		230	seconds) after the first invocation. If C<interval> is specified with a
		231	false value, then it is treated as if it were missing.
188		232
189	Example:	233	The callback will be rescheduled before invoking the callback, but no
		234	attempt is done to avoid timer drift in most backends, so the interval is
		235	only approximate.
190		236
191	# fire an event after 7.7 seconds	237	Example: fire an event after 7.7 seconds.
		238
192	my $w = AnyEvent->timer (after => 7.7, cb => sub {	239	my $w = AnyEvent->timer (after => 7.7, cb => sub {
193	warn "timeout\n";	240	warn "timeout\n";
194	});	241	});
195		242
196	# to cancel the timer:	243	# to cancel the timer:
197	undef $w;	244	undef $w;
198		245
199	Example 2:
200
201	# fire an event after 0.5 seconds, then roughly every second	246	Example 2: fire an event after 0.5 seconds, then roughly every second.
202	my $w;
203		247
204	my $cb = sub {
205	# cancel the old timer while creating a new one
206	$w = AnyEvent->timer (after => 1, cb => $cb);	248	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		249	warn "timeout\n";
207	};	250	};
208
209	# start the "loop" by creating the first watcher
210	$w = AnyEvent->timer (after => 0.5, cb => $cb);
211		251
212	=head3 TIMING ISSUES	252	=head3 TIMING ISSUES
213		253
214	There are two ways to handle timers: based on real time (relative, "fire	254	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	255	in 10 seconds") and based on wallclock time (absolute, "fire at 12
…		…
227	timers.	267	timers.
228		268
229	AnyEvent always prefers relative timers, if available, matching the	269	AnyEvent always prefers relative timers, if available, matching the
230	AnyEvent API.	270	AnyEvent API.
231		271
		272	AnyEvent has two additional methods that return the "current time":
		273
		274	=over 4
		275
		276	=item AnyEvent->time
		277
		278	This returns the "current wallclock time" as a fractional number of
		279	seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
		280	return, and the result is guaranteed to be compatible with those).
		281
		282	It progresses independently of any event loop processing, i.e. each call
		283	will check the system clock, which usually gets updated frequently.
		284
		285	=item AnyEvent->now
		286
		287	This also returns the "current wallclock time", but unlike C<time>, above,
		288	this value might change only once per event loop iteration, depending on
		289	the event loop (most return the same time as C<time>, above). This is the
		290	time that AnyEvent's timers get scheduled against.
		291
		292	I<In almost all cases (in all cases if you don't care), this is the
		293	function to call when you want to know the current time.>
		294
		295	This function is also often faster then C<< AnyEvent->time >>, and
		296	thus the preferred method if you want some timestamp (for example,
		297	L<AnyEvent::Handle> uses this to update it's activity timeouts).
		298
		299	The rest of this section is only of relevance if you try to be very exact
		300	with your timing, you can skip it without bad conscience.
		301
		302	For a practical example of when these times differ, consider L<Event::Lib>
		303	and L<EV> and the following set-up:
		304
		305	The event loop is running and has just invoked one of your callback at
		306	time=500 (assume no other callbacks delay processing). In your callback,
		307	you wait a second by executing C<sleep 1> (blocking the process for a
		308	second) and then (at time=501) you create a relative timer that fires
		309	after three seconds.
		310
		311	With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
		312	both return C<501>, because that is the current time, and the timer will
		313	be scheduled to fire at time=504 (C<501> + C<3>).
		314
		315	With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
		316	time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
		317	last event processing phase started. With L<EV>, your timer gets scheduled
		318	to run at time=503 (C<500> + C<3>).
		319
		320	In one sense, L<Event::Lib> is more exact, as it uses the current time
		321	regardless of any delays introduced by event processing. However, most
		322	callbacks do not expect large delays in processing, so this causes a
		323	higher drift (and a lot more system calls to get the current time).
		324
		325	In another sense, L<EV> is more exact, as your timer will be scheduled at
		326	the same time, regardless of how long event processing actually took.
		327
		328	In either case, if you care (and in most cases, you don't), then you
		329	can get whatever behaviour you want with any event loop, by taking the
		330	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
		331	account.
		332
		333	=item AnyEvent->now_update
		334
		335	Some event loops (such as L<EV> or L<AnyEvent::Impl::Perl>) cache
		336	the current time for each loop iteration (see the discussion of L<<
		337	AnyEvent->now >>, above).
		338
		339	When a callback runs for a long time (or when the process sleeps), then
		340	this "current" time will differ substantially from the real time, which
		341	might affect timers and time-outs.
		342
		343	When this is the case, you can call this method, which will update the
		344	event loop's idea of "current time".
		345
		346	Note that updating the time I<might> cause some events to be handled.
		347
		348	=back
		349
232	=head2 SIGNAL WATCHERS	350	=head2 SIGNAL WATCHERS
233		351
234	You can watch for signals using a signal watcher, C<signal> is the signal	352	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	353	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
236	be invoked whenever a signal occurs.	354	callback to be invoked whenever a signal occurs.
237		355
238	Although the callback might get passed parameters, their value and	356	Although the callback might get passed parameters, their value and
239	presence is undefined and you cannot rely on them. Portable AnyEvent	357	presence is undefined and you cannot rely on them. Portable AnyEvent
240	callbacks cannot use arguments passed to signal watcher callbacks.	358	callbacks cannot use arguments passed to signal watcher callbacks.
241		359
…		…
243	invocation, and callback invocation will be synchronous. Synchronous means	361	invocation, and callback invocation will be synchronous. Synchronous means
244	that it might take a while until the signal gets handled by the process,	362	that it might take a while until the signal gets handled by the process,
245	but it is guaranteed not to interrupt any other callbacks.	363	but it is guaranteed not to interrupt any other callbacks.
246		364
247	The main advantage of using these watchers is that you can share a signal	365	The main advantage of using these watchers is that you can share a signal
248	between multiple watchers.	366	between multiple watchers, and AnyEvent will ensure that signals will not
		367	interrupt your program at bad times.
249		368
250	This watcher might use C<%SIG>, so programs overwriting those signals	369	This watcher might use C<%SIG> (depending on the event loop used),
251	directly will likely not work correctly.	370	so programs overwriting those signals directly will likely not work
		371	correctly.
		372
		373	Also note that many event loops (e.g. Glib, Tk, Qt, IO::Async) do not
		374	support attaching callbacks to signals, which is a pity, as you cannot do
		375	race-free signal handling in perl. AnyEvent will try to do it's best, but
		376	in some cases, signals will be delayed. The maximum time a signal might
		377	be delayed is specified in C<$AnyEvent::MAX_SIGNAL_LATENCY> (default: 10
		378	seconds). This variable can be changed only before the first signal
		379	watcher is created, and should be left alone otherwise. Higher values
		380	will cause fewer spurious wake-ups, which is better for power and CPU
		381	saving. All these problems can be avoided by installing the optional
		382	L<Async::Interrupt> module.
252		383
253	Example: exit on SIGINT	384	Example: exit on SIGINT
254		385
255	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	386	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
256		387
257	=head2 CHILD PROCESS WATCHERS	388	=head2 CHILD PROCESS WATCHERS
258		389
259	You can also watch on a child process exit and catch its exit status.	390	You can also watch on a child process exit and catch its exit status.
260		391
261	The child process is specified by the C<pid> argument (if set to C<0>, it	392	The child process is specified by the C<pid> argument (if set to C<0>, it
262	watches for any child process exit). The watcher will trigger as often	393	watches for any child process exit). The watcher will triggered only when
263	as status change for the child are received. This works by installing a	394	the child process has finished and an exit status is available, not on
264	signal handler for C<SIGCHLD>. The callback will be called with the pid	395	any trace events (stopped/continued).
265	and exit status (as returned by waitpid), so unlike other watcher types,	396
266	you I<can> rely on child watcher callback arguments.	397	The callback will be called with the pid and exit status (as returned by
		398	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		399	callback arguments.
		400
		401	This watcher type works by installing a signal handler for C<SIGCHLD>,
		402	and since it cannot be shared, nothing else should use SIGCHLD or reap
		403	random child processes (waiting for specific child processes, e.g. inside
		404	C<system>, is just fine).
267		405
268	There is a slight catch to child watchers, however: you usually start them	406	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	407	I<after> the child process was created, and this means the process could
270	have exited already (and no SIGCHLD will be sent anymore).	408	have exited already (and no SIGCHLD will be sent anymore).
271		409
272	Not all event models handle this correctly (POE doesn't), but even for	410	Not all event models handle this correctly (neither POE nor IO::Async do,
		411	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	412	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).	413	the process exits (i.e. before you fork in the first place). AnyEvent's
		414	pure perl event loop handles all cases correctly regardless of when you
		415	start the watcher.
275		416
276	This means you cannot create a child watcher as the very first thing in an	417	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	418	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>).	419	watcher before you C<fork> the child (alternatively, you can call
		420	C<AnyEvent::detect>).
		421
		422	As most event loops do not support waiting for child events, they will be
		423	emulated by AnyEvent in most cases, in which the latency and race problems
		424	mentioned in the description of signal watchers apply.
279		425
280	Example: fork a process and wait for it	426	Example: fork a process and wait for it
281		427
282	my $done = AnyEvent->condvar;	428	my $done = AnyEvent->condvar;
283		429
284	my $pid = fork or exit 5;	430	my $pid = fork or exit 5;
285		431
286	my $w = AnyEvent->child (	432	my $w = AnyEvent->child (
287	pid => $pid,	433	pid => $pid,
288	cb => sub {	434	cb => sub {
289	my ($pid, $status) = @_;	435	my ($pid, $status) = @_;
290	warn "pid $pid exited with status $status";	436	warn "pid $pid exited with status $status";
291	$done->send;	437	$done->send;
292	},	438	},
293	);	439	);
294		440
295	# do something else, then wait for process exit	441	# do something else, then wait for process exit
296	$done->recv;	442	$done->recv;
		443
		444	=head2 IDLE WATCHERS
		445
		446	Sometimes there is a need to do something, but it is not so important
		447	to do it instantly, but only when there is nothing better to do. This
		448	"nothing better to do" is usually defined to be "no other events need
		449	attention by the event loop".
		450
		451	Idle watchers ideally get invoked when the event loop has nothing
		452	better to do, just before it would block the process to wait for new
		453	events. Instead of blocking, the idle watcher is invoked.
		454
		455	Most event loops unfortunately do not really support idle watchers (only
		456	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		457	will simply call the callback "from time to time".
		458
		459	Example: read lines from STDIN, but only process them when the
		460	program is otherwise idle:
		461
		462	my @lines; # read data
		463	my $idle_w;
		464	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		465	push @lines, scalar <STDIN>;
		466
		467	# start an idle watcher, if not already done
		468	$idle_w ||= AnyEvent->idle (cb => sub {
		469	# handle only one line, when there are lines left
		470	if (my $line = shift @lines) {
		471	print "handled when idle: $line";
		472	} else {
		473	# otherwise disable the idle watcher again
		474	undef $idle_w;
		475	}
		476	});
		477	});
297		478
298	=head2 CONDITION VARIABLES	479	=head2 CONDITION VARIABLES
299		480
300	If you are familiar with some event loops you will know that all of them	481	If you are familiar with some event loops you will know that all of them
301	require you to run some blocking "loop", "run" or similar function that	482	require you to run some blocking "loop", "run" or similar function that
302	will actively watch for new events and call your callbacks.	483	will actively watch for new events and call your callbacks.
303		484
304	AnyEvent is different, it expects somebody else to run the event loop and	485	AnyEvent is slightly different: it expects somebody else to run the event
305	will only block when necessary (usually when told by the user).	486	loop and will only block when necessary (usually when told by the user).
306		487
307	The instrument to do that is called a "condition variable", so called	488	The instrument to do that is called a "condition variable", so called
308	because they represent a condition that must become true.	489	because they represent a condition that must become true.
		490
		491	Now is probably a good time to look at the examples further below.
309		492
310	Condition variables can be created by calling the C<< AnyEvent->condvar	493	Condition variables can be created by calling the C<< AnyEvent->condvar
311	>> method, usually without arguments. The only argument pair allowed is	494	>> method, usually without arguments. The only argument pair allowed is
312	C<cb>, which specifies a callback to be called when the condition variable	495	C<cb>, which specifies a callback to be called when the condition variable
313	becomes true.	496	becomes true, with the condition variable as the first argument (but not
		497	the results).
314		498
315	After creation, the condition variable is "false" until it becomes "true"	499	After creation, the condition variable is "false" until it becomes "true"
316	by calling the C<send> method (or calling the condition variable as if it	500	by calling the C<send> method (or calling the condition variable as if it
317	were a callback, read about the caveats in the description for the C<<	501	were a callback, read about the caveats in the description for the C<<
318	->send >> method).	502	->send >> method).
…		…
364	after => 1,	548	after => 1,
365	cb => sub { $result_ready->send },	549	cb => sub { $result_ready->send },
366	);	550	);
367		551
368	# this "blocks" (while handling events) till the callback	552	# this "blocks" (while handling events) till the callback
369	# calls send	553	# calls -<send
370	$result_ready->recv;	554	$result_ready->recv;
371		555
372	Example: wait for a timer, but take advantage of the fact that	556	Example: wait for a timer, but take advantage of the fact that condition
373	condition variables are also code references.	557	variables are also callable directly.
374		558
375	my $done = AnyEvent->condvar;	559	my $done = AnyEvent->condvar;
376	my $delay = AnyEvent->timer (after => 5, cb => $done);	560	my $delay = AnyEvent->timer (after => 5, cb => $done);
377	$done->recv;	561	$done->recv;
		562
		563	Example: Imagine an API that returns a condvar and doesn't support
		564	callbacks. This is how you make a synchronous call, for example from
		565	the main program:
		566
		567	use AnyEvent::CouchDB;
		568
		569	...
		570
		571	my @info = $couchdb->info->recv;
		572
		573	And this is how you would just set a callback to be called whenever the
		574	results are available:
		575
		576	$couchdb->info->cb (sub {
		577	my @info = $_[0]->recv;
		578	});
378		579
379	=head3 METHODS FOR PRODUCERS	580	=head3 METHODS FOR PRODUCERS
380		581
381	These methods should only be used by the producing side, i.e. the	582	These methods should only be used by the producing side, i.e. the
382	code/module that eventually sends the signal. Note that it is also	583	code/module that eventually sends the signal. Note that it is also
…		…
395	immediately from within send.	596	immediately from within send.
396		597
397	Any arguments passed to the C<send> call will be returned by all	598	Any arguments passed to the C<send> call will be returned by all
398	future C<< ->recv >> calls.	599	future C<< ->recv >> calls.
399		600
400	Condition variables are overloaded so one can call them directly	601	Condition variables are overloaded so one can call them directly (as if
401	(as a code reference). Calling them directly is the same as calling	602	they were a code reference). Calling them directly is the same as calling
402	C<send>. Note, however, that many C-based event loops do not handle	603	C<send>.
403	overloading, so as tempting as it may be, passing a condition variable
404	instead of a callback does not work. Both the pure perl and EV loops
405	support overloading, however, as well as all functions that use perl to
406	invoke a callback (as in L<AnyEvent::Socket> and L<AnyEvent::DNS> for
407	example).
408		604
409	=item $cv->croak ($error)	605	=item $cv->croak ($error)
410		606
411	Similar to send, but causes all call's to C<< ->recv >> to invoke	607	Similar to send, but causes all call's to C<< ->recv >> to invoke
412	C<Carp::croak> with the given error message/object/scalar.	608	C<Carp::croak> with the given error message/object/scalar.
413		609
414	This can be used to signal any errors to the condition variable	610	This can be used to signal any errors to the condition variable
415	user/consumer.	611	user/consumer. Doing it this way instead of calling C<croak> directly
		612	delays the error detetcion, but has the overwhelmign advantage that it
		613	diagnoses the error at the place where the result is expected, and not
		614	deep in some event clalback without connection to the actual code causing
		615	the problem.
416		616
417	=item $cv->begin ([group callback])	617	=item $cv->begin ([group callback])
418		618
419	=item $cv->end	619	=item $cv->end
420
421	These two methods are EXPERIMENTAL and MIGHT CHANGE.
422		620
423	These two methods can be used to combine many transactions/events into	621	These two methods can be used to combine many transactions/events into
424	one. For example, a function that pings many hosts in parallel might want	622	one. For example, a function that pings many hosts in parallel might want
425	to use a condition variable for the whole process.	623	to use a condition variable for the whole process.
426		624
…		…
428	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end	626	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
429	>>, the (last) callback passed to C<begin> will be executed. That callback	627	>>, the (last) callback passed to C<begin> will be executed. That callback
430	is I<supposed> to call C<< ->send >>, but that is not required. If no	628	is I<supposed> to call C<< ->send >>, but that is not required. If no
431	callback was set, C<send> will be called without any arguments.	629	callback was set, C<send> will be called without any arguments.
432		630
433	Let's clarify this with the ping example:	631	You can think of C<< $cv->send >> giving you an OR condition (one call
		632	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		633	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		634
		635	Let's start with a simple example: you have two I/O watchers (for example,
		636	STDOUT and STDERR for a program), and you want to wait for both streams to
		637	close before activating a condvar:
		638
		639	my $cv = AnyEvent->condvar;
		640
		641	$cv->begin; # first watcher
		642	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		643	defined sysread $fh1, my $buf, 4096
		644	or $cv->end;
		645	});
		646
		647	$cv->begin; # second watcher
		648	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		649	defined sysread $fh2, my $buf, 4096
		650	or $cv->end;
		651	});
		652
		653	$cv->recv;
		654
		655	This works because for every event source (EOF on file handle), there is
		656	one call to C<begin>, so the condvar waits for all calls to C<end> before
		657	sending.
		658
		659	The ping example mentioned above is slightly more complicated, as the
		660	there are results to be passwd back, and the number of tasks that are
		661	begung can potentially be zero:
434		662
435	my $cv = AnyEvent->condvar;	663	my $cv = AnyEvent->condvar;
436		664
437	my %result;	665	my %result;
438	$cv->begin (sub { $cv->send (\%result) });	666	$cv->begin (sub { $cv->send (\%result) });
…		…
458	loop, which serves two important purposes: first, it sets the callback	686	loop, which serves two important purposes: first, it sets the callback
459	to be called once the counter reaches C<0>, and second, it ensures that	687	to be called once the counter reaches C<0>, and second, it ensures that
460	C<send> is called even when C<no> hosts are being pinged (the loop	688	C<send> is called even when C<no> hosts are being pinged (the loop
461	doesn't execute once).	689	doesn't execute once).
462		690
463	This is the general pattern when you "fan out" into multiple subrequests:	691	This is the general pattern when you "fan out" into multiple (but
464	use an outer C<begin>/C<end> pair to set the callback and ensure C<end>	692	potentially none) subrequests: use an outer C<begin>/C<end> pair to set
465	is called at least once, and then, for each subrequest you start, call	693	the callback and ensure C<end> is called at least once, and then, for each
466	C<begin> and for each subrequest you finish, call C<end>.	694	subrequest you start, call C<begin> and for each subrequest you finish,
		695	call C<end>.
467		696
468	=back	697	=back
469		698
470	=head3 METHODS FOR CONSUMERS	699	=head3 METHODS FOR CONSUMERS
471		700
…		…
487	function will call C<croak>.	716	function will call C<croak>.
488		717
489	In list context, all parameters passed to C<send> will be returned,	718	In list context, all parameters passed to C<send> will be returned,
490	in scalar context only the first one will be returned.	719	in scalar context only the first one will be returned.
491		720
		721	Note that doing a blocking wait in a callback is not supported by any
		722	event loop, that is, recursive invocation of a blocking C<< ->recv
		723	>> is not allowed, and the C<recv> call will C<croak> if such a
		724	condition is detected. This condition can be slightly loosened by using
		725	L<Coro::AnyEvent>, which allows you to do a blocking C<< ->recv >> from
		726	any thread that doesn't run the event loop itself.
		727
492	Not all event models support a blocking wait - some die in that case	728	Not all event models support a blocking wait - some die in that case
493	(programs might want to do that to stay interactive), so I<if you are	729	(programs might want to do that to stay interactive), so I<if you are
494	using this from a module, never require a blocking wait>, but let the	730	using this from a module, never require a blocking wait>. Instead, let the
495	caller decide whether the call will block or not (for example, by coupling	731	caller decide whether the call will block or not (for example, by coupling
496	condition variables with some kind of request results and supporting	732	condition variables with some kind of request results and supporting
497	callbacks so the caller knows that getting the result will not block,	733	callbacks so the caller knows that getting the result will not block,
498	while still supporting blocking waits if the caller so desires).	734	while still supporting blocking waits if the caller so desires).
499		735
500	Another reason I<never> to C<< ->recv >> in a module is that you cannot
501	sensibly have two C<< ->recv >>'s in parallel, as that would require
502	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
503	can supply.
504
505	The L<Coro> module, however, I<can> and I<does> supply coroutines and, in
506	fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe
507	versions and also integrates coroutines into AnyEvent, making blocking
508	C<< ->recv >> calls perfectly safe as long as they are done from another
509	coroutine (one that doesn't run the event loop).
510
511	You can ensure that C<< -recv >> never blocks by setting a callback and	736	You can ensure that C<< -recv >> never blocks by setting a callback and
512	only calling C<< ->recv >> from within that callback (or at a later	737	only calling C<< ->recv >> from within that callback (or at a later
513	time). This will work even when the event loop does not support blocking	738	time). This will work even when the event loop does not support blocking
514	waits otherwise.	739	waits otherwise.
515		740
516	=item $bool = $cv->ready	741	=item $bool = $cv->ready
517		742
518	Returns true when the condition is "true", i.e. whether C<send> or	743	Returns true when the condition is "true", i.e. whether C<send> or
519	C<croak> have been called.	744	C<croak> have been called.
520		745
521	=item $cb = $cv->cb ([new callback])	746	=item $cb = $cv->cb ($cb->($cv))
522		747
523	This is a mutator function that returns the callback set and optionally	748	This is a mutator function that returns the callback set and optionally
524	replaces it before doing so.	749	replaces it before doing so.
525		750
526	The callback will be called when the condition becomes "true", i.e. when	751	The callback will be called when the condition becomes "true", i.e. when
527	C<send> or C<croak> are called. Calling C<recv> inside the callback	752	C<send> or C<croak> are called, with the only argument being the condition
528	or at any later time is guaranteed not to block.	753	variable itself. Calling C<recv> inside the callback or at any later time
		754	is guaranteed not to block.
529		755
530	=back	756	=back
531		757
		758	=head1 SUPPORTED EVENT LOOPS/BACKENDS
		759
		760	The available backend classes are (every class has its own manpage):
		761
		762	=over 4
		763
		764	=item Backends that are autoprobed when no other event loop can be found.
		765
		766	EV is the preferred backend when no other event loop seems to be in
		767	use. If EV is not installed, then AnyEvent will try Event, and, failing
		768	that, will fall back to its own pure-perl implementation, which is
		769	available everywhere as it comes with AnyEvent itself.
		770
		771	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		772	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		773	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
		774
		775	=item Backends that are transparently being picked up when they are used.
		776
		777	These will be used when they are currently loaded when the first watcher
		778	is created, in which case it is assumed that the application is using
		779	them. This means that AnyEvent will automatically pick the right backend
		780	when the main program loads an event module before anything starts to
		781	create watchers. Nothing special needs to be done by the main program.
		782
		783	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		784	AnyEvent::Impl::Tk based on Tk, very broken.
		785	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		786	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		787
		788	=item Backends with special needs.
		789
		790	Qt requires the Qt::Application to be instantiated first, but will
		791	otherwise be picked up automatically. As long as the main program
		792	instantiates the application before any AnyEvent watchers are created,
		793	everything should just work.
		794
		795	AnyEvent::Impl::Qt based on Qt.
		796
		797	Support for IO::Async can only be partial, as it is too broken and
		798	architecturally limited to even support the AnyEvent API. It also
		799	is the only event loop that needs the loop to be set explicitly, so
		800	it can only be used by a main program knowing about AnyEvent. See
		801	L<AnyEvent::Impl::Async> for the gory details.
		802
		803	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
		804
		805	=item Event loops that are indirectly supported via other backends.
		806
		807	Some event loops can be supported via other modules:
		808
		809	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		810
		811	B<WxWidgets> has no support for watching file handles. However, you can
		812	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		813	polls 20 times per second, which was considered to be too horrible to even
		814	consider for AnyEvent.
		815
		816	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		817	backend, so it can be supported through POE.
		818
		819	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		820	load L<POE> when detecting them, in the hope that POE will pick them up,
		821	in which case everything will be automatic.
		822
		823	=back
		824
532	=head1 GLOBAL VARIABLES AND FUNCTIONS	825	=head1 GLOBAL VARIABLES AND FUNCTIONS
533		826
		827	These are not normally required to use AnyEvent, but can be useful to
		828	write AnyEvent extension modules.
		829
534	=over 4	830	=over 4
535		831
536	=item $AnyEvent::MODEL	832	=item $AnyEvent::MODEL
537		833
538	Contains C<undef> until the first watcher is being created. Then it	834	Contains C<undef> until the first watcher is being created, before the
		835	backend has been autodetected.
		836
539	contains the event model that is being used, which is the name of the	837	Afterwards it contains the event model that is being used, which is the
540	Perl class implementing the model. This class is usually one of the	838	name of the Perl class implementing the model. This class is usually one
541	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	839	of the C<AnyEvent::Impl:xxx> modules, but can be any other class in the
542	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	840	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
543		841	will be C<urxvt::anyevent>).
544	The known classes so far are:
545
546	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
547	AnyEvent::Impl::Event based on Event, second best choice.
548	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
549	AnyEvent::Impl::Glib based on Glib, third-best choice.
550	AnyEvent::Impl::Tk based on Tk, very bad choice.
551	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
552	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
553	AnyEvent::Impl::POE based on POE, not generic enough for full support.
554
555	There is no support for WxWidgets, as WxWidgets has no support for
556	watching file handles. However, you can use WxWidgets through the
557	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
558	second, which was considered to be too horrible to even consider for
559	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
560	it's adaptor.
561
562	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
563	autodetecting them.
564		842
565	=item AnyEvent::detect	843	=item AnyEvent::detect
566		844
567	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	845	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
568	if necessary. You should only call this function right before you would	846	if necessary. You should only call this function right before you would
569	have created an AnyEvent watcher anyway, that is, as late as possible at	847	have created an AnyEvent watcher anyway, that is, as late as possible at
570	runtime.	848	runtime, and not e.g. while initialising of your module.
		849
		850	If you need to do some initialisation before AnyEvent watchers are
		851	created, use C<post_detect>.
571		852
572	=item $guard = AnyEvent::post_detect { BLOCK }	853	=item $guard = AnyEvent::post_detect { BLOCK }
573		854
574	Arranges for the code block to be executed as soon as the event model is	855	Arranges for the code block to be executed as soon as the event model is
575	autodetected (or immediately if this has already happened).	856	autodetected (or immediately if this has already happened).
		857
		858	The block will be executed I<after> the actual backend has been detected
		859	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		860	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		861	other initialisations - see the sources of L<AnyEvent::Strict> or
		862	L<AnyEvent::AIO> to see how this is used.
		863
		864	The most common usage is to create some global watchers, without forcing
		865	event module detection too early, for example, L<AnyEvent::AIO> creates
		866	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		867	avoid autodetecting the event module at load time.
576		868
577	If called in scalar or list context, then it creates and returns an object	869	If called in scalar or list context, then it creates and returns an object
578	that automatically removes the callback again when it is destroyed. See	870	that automatically removes the callback again when it is destroyed. See
579	L<Coro::BDB> for a case where this is useful.	871	L<Coro::BDB> for a case where this is useful.
580		872
…		…
583	If there are any code references in this array (you can C<push> to it	875	If there are any code references in this array (you can C<push> to it
584	before or after loading AnyEvent), then they will called directly after	876	before or after loading AnyEvent), then they will called directly after
585	the event loop has been chosen.	877	the event loop has been chosen.
586		878
587	You should check C<$AnyEvent::MODEL> before adding to this array, though:	879	You should check C<$AnyEvent::MODEL> before adding to this array, though:
588	if it contains a true value then the event loop has already been detected,	880	if it is defined then the event loop has already been detected, and the
589	and the array will be ignored.	881	array will be ignored.
590		882
591	Best use C<AnyEvent::post_detect { BLOCK }> instead.	883	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		884	it,as it takes care of these details.
		885
		886	This variable is mainly useful for modules that can do something useful
		887	when AnyEvent is used and thus want to know when it is initialised, but do
		888	not need to even load it by default. This array provides the means to hook
		889	into AnyEvent passively, without loading it.
592		890
593	=back	891	=back
594		892
595	=head1 WHAT TO DO IN A MODULE	893	=head1 WHAT TO DO IN A MODULE
596		894
…		…
651		949
652		950
653	=head1 OTHER MODULES	951	=head1 OTHER MODULES
654		952
655	The following is a non-exhaustive list of additional modules that use	953	The following is a non-exhaustive list of additional modules that use
656	AnyEvent and can therefore be mixed easily with other AnyEvent modules	954	AnyEvent as a client and can therefore be mixed easily with other AnyEvent
657	in the same program. Some of the modules come with AnyEvent, some are	955	modules and other event loops in the same program. Some of the modules
658	available via CPAN.	956	come with AnyEvent, most are available via CPAN.
659		957
660	=over 4	958	=over 4
661		959
662	=item L<AnyEvent::Util>	960	=item L<AnyEvent::Util>
663		961
664	Contains various utility functions that replace often-used but blocking	962	Contains various utility functions that replace often-used but blocking
665	functions such as C<inet_aton> by event-/callback-based versions.	963	functions such as C<inet_aton> by event-/callback-based versions.
666
667	=item L<AnyEvent::Handle>
668
669	Provide read and write buffers and manages watchers for reads and writes.
670		964
671	=item L<AnyEvent::Socket>	965	=item L<AnyEvent::Socket>
672		966
673	Provides various utility functions for (internet protocol) sockets,	967	Provides various utility functions for (internet protocol) sockets,
674	addresses and name resolution. Also functions to create non-blocking tcp	968	addresses and name resolution. Also functions to create non-blocking tcp
675	connections or tcp servers, with IPv6 and SRV record support and more.	969	connections or tcp servers, with IPv6 and SRV record support and more.
676		970
		971	=item L<AnyEvent::Handle>
		972
		973	Provide read and write buffers, manages watchers for reads and writes,
		974	supports raw and formatted I/O, I/O queued and fully transparent and
		975	non-blocking SSL/TLS (via L<AnyEvent::TLS>.
		976
677	=item L<AnyEvent::DNS>	977	=item L<AnyEvent::DNS>
678		978
679	Provides rich asynchronous DNS resolver capabilities.	979	Provides rich asynchronous DNS resolver capabilities.
680		980
		981	=item L<AnyEvent::HTTP>
		982
		983	A simple-to-use HTTP library that is capable of making a lot of concurrent
		984	HTTP requests.
		985
681	=item L<AnyEvent::HTTPD>	986	=item L<AnyEvent::HTTPD>
682		987
683	Provides a simple web application server framework.	988	Provides a simple web application server framework.
684		989
685	=item L<AnyEvent::FastPing>	990	=item L<AnyEvent::FastPing>
686		991
687	The fastest ping in the west.	992	The fastest ping in the west.
688		993
		994	=item L<AnyEvent::DBI>
		995
		996	Executes L<DBI> requests asynchronously in a proxy process.
		997
		998	=item L<AnyEvent::AIO>
		999
		1000	Truly asynchronous I/O, should be in the toolbox of every event
		1001	programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
		1002	together.
		1003
		1004	=item L<AnyEvent::BDB>
		1005
		1006	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
		1007	L<BDB> and AnyEvent together.
		1008
		1009	=item L<AnyEvent::GPSD>
		1010
		1011	A non-blocking interface to gpsd, a daemon delivering GPS information.
		1012
689	=item L<Net::IRC3>	1013	=item L<AnyEvent::IRC>
690		1014
691	AnyEvent based IRC client module family.	1015	AnyEvent based IRC client module family (replacing the older Net::IRC3).
692		1016
693	=item L<Net::XMPP2>	1017	=item L<AnyEvent::XMPP>
694		1018
695	AnyEvent based XMPP (Jabber protocol) module family.	1019	AnyEvent based XMPP (Jabber protocol) module family (replacing the older
		1020	Net::XMPP2>.
		1021
		1022	=item L<AnyEvent::IGS>
		1023
		1024	A non-blocking interface to the Internet Go Server protocol (used by
		1025	L<App::IGS>).
696		1026
697	=item L<Net::FCP>	1027	=item L<Net::FCP>
698		1028
699	AnyEvent-based implementation of the Freenet Client Protocol, birthplace	1029	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
700	of AnyEvent.	1030	of AnyEvent.
…		…
705		1035
706	=item L<Coro>	1036	=item L<Coro>
707		1037
708	Has special support for AnyEvent via L<Coro::AnyEvent>.	1038	Has special support for AnyEvent via L<Coro::AnyEvent>.
709		1039
710	=item L<AnyEvent::AIO>, L<IO::AIO>
711
712	Truly asynchronous I/O, should be in the toolbox of every event
713	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
714	together.
715
716	=item L<AnyEvent::BDB>, L<BDB>
717
718	Truly asynchronous Berkeley DB access. AnyEvent::AIO transparently fuses
719	IO::AIO and AnyEvent together.
720
721	=item L<IO::Lambda>
722
723	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
724
725	=back	1040	=back
726		1041
727	=cut	1042	=cut
728		1043
729	package AnyEvent;	1044	package AnyEvent;
730		1045
731	no warnings;	1046	no warnings;
732	use strict;	1047	use strict qw(vars subs);
733		1048
734	use Carp;	1049	use Carp ();
735		1050
736	our $VERSION = '4.03';	1051	our $VERSION = 4.83;
737	our $MODEL;	1052	our $MODEL;
738		1053
739	our $AUTOLOAD;	1054	our $AUTOLOAD;
740	our @ISA;	1055	our @ISA;
741		1056
742	our @REGISTRY;	1057	our @REGISTRY;
743		1058
		1059	our $WIN32;
		1060
		1061	our $VERBOSE;
		1062
		1063	BEGIN {
		1064	eval "sub WIN32(){ " . (($^O =~ /mswin32/i)*1) ." }";
		1065	eval "sub TAINT(){ " . (${^TAINT}*1) . " }";
		1066
		1067	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1068	if ${^TAINT};
		1069
744	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;	1070	$VERBOSE = $ENV{PERL_ANYEVENT_VERBOSE}*1;
745		1071
746	our %PROTOCOL; # (ipv4|ipv6) => (1|2)	1072	}
		1073
		1074	our $MAX_SIGNAL_LATENCY = 10;
		1075
		1076	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
747		1077
748	{	1078	{
749	my $idx;	1079	my $idx;
750	$PROTOCOL{$_} = ++$idx	1080	$PROTOCOL{$_} = ++$idx
		1081	for reverse split /\s*,\s*/,
751	for split /\s*,\s*/, $ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";	1082	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
752	}	1083	}
753		1084
754	my @models = (	1085	my @models = (
755	[EV:: => AnyEvent::Impl::EV::],	1086	[EV:: => AnyEvent::Impl::EV::],
756	[Event:: => AnyEvent::Impl::Event::],	1087	[Event:: => AnyEvent::Impl::Event::],
757	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1088	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
758	# everything below here will not be autoprobed	1089	# everything below here will not be autoprobed
759	# as the pureperl backend should work everywhere	1090	# as the pureperl backend should work everywhere
760	# and is usually faster	1091	# and is usually faster
761	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
762	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers	1092	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers
763	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy	1093	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		1094	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
764	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program	1095	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
765	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza	1096	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
766	[Wx:: => AnyEvent::Impl::POE::],	1097	[Wx:: => AnyEvent::Impl::POE::],
767	[Prima:: => AnyEvent::Impl::POE::],	1098	[Prima:: => AnyEvent::Impl::POE::],
		1099	# IO::Async is just too broken - we would need workarounds for its
		1100	# byzantine signal and broken child handling, among others.
		1101	# IO::Async is rather hard to detect, as it doesn't have any
		1102	# obvious default class.
		1103	# [IO::Async:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1104	# [IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1105	# [IO::Async::Notifier:: => AnyEvent::Impl::IOAsync::], # requires special main program
768	);	1106	);
769		1107
770	our %method = map +($_ => 1), qw(io timer signal child condvar one_event DESTROY);	1108	our %method = map +($_ => 1),
		1109	qw(io timer time now now_update signal child idle condvar one_event DESTROY);
771		1110
772	our @post_detect;	1111	our @post_detect;
773		1112
774	sub post_detect(&) {	1113	sub post_detect(&) {
775	my ($cb) = @_;	1114	my ($cb) = @_;
…		…
780	1	1119	1
781	} else {	1120	} else {
782	push @post_detect, $cb;	1121	push @post_detect, $cb;
783		1122
784	defined wantarray	1123	defined wantarray
785	? bless \$cb, "AnyEvent::Util::PostDetect"	1124	? bless \$cb, "AnyEvent::Util::postdetect"
786	: ()	1125	: ()
787	}	1126	}
788	}	1127	}
789		1128
790	sub AnyEvent::Util::PostDetect::DESTROY {	1129	sub AnyEvent::Util::postdetect::DESTROY {
791	@post_detect = grep $_ != ${$_[0]}, @post_detect;	1130	@post_detect = grep $_ != ${$_[0]}, @post_detect;
792	}	1131	}
793		1132
794	sub detect() {	1133	sub detect() {
795	unless ($MODEL) {	1134	unless ($MODEL) {
796	no strict 'refs';	1135	no strict 'refs';
		1136	local $SIG{__DIE__};
797		1137
798	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	1138	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
799	my $model = "AnyEvent::Impl::$1";	1139	my $model = "AnyEvent::Impl::$1";
800	if (eval "require $model") {	1140	if (eval "require $model") {
801	$MODEL = $model;	1141	$MODEL = $model;
802	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	1142	warn "AnyEvent: loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.\n" if $VERBOSE >= 2;
803	} else {	1143	} else {
804	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;	1144	warn "AnyEvent: unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@" if $VERBOSE;
805	}	1145	}
806	}	1146	}
807		1147
808	# check for already loaded models	1148	# check for already loaded models
809	unless ($MODEL) {	1149	unless ($MODEL) {
810	for (@REGISTRY, @models) {	1150	for (@REGISTRY, @models) {
811	my ($package, $model) = @$_;	1151	my ($package, $model) = @$_;
812	if (${"$package\::VERSION"} > 0) {	1152	if (${"$package\::VERSION"} > 0) {
813	if (eval "require $model") {	1153	if (eval "require $model") {
814	$MODEL = $model;	1154	$MODEL = $model;
815	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;	1155	warn "AnyEvent: autodetected model '$model', using it.\n" if $VERBOSE >= 2;
816	last;	1156	last;
817	}	1157	}
818	}	1158	}
819	}	1159	}
820		1160
…		…
825	my ($package, $model) = @$_;	1165	my ($package, $model) = @$_;
826	if (eval "require $package"	1166	if (eval "require $package"
827	and ${"$package\::VERSION"} > 0	1167	and ${"$package\::VERSION"} > 0
828	and eval "require $model") {	1168	and eval "require $model") {
829	$MODEL = $model;	1169	$MODEL = $model;
830	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;	1170	warn "AnyEvent: autoprobed model '$model', using it.\n" if $VERBOSE >= 2;
831	last;	1171	last;
832	}	1172	}
833	}	1173	}
834		1174
835	$MODEL	1175	$MODEL
836	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.";	1176	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.\n";
837	}	1177	}
838	}	1178	}
839		1179
		1180	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		1181
840	unshift @ISA, $MODEL;	1182	unshift @ISA, $MODEL;
841	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	1183
		1184	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
842		1185
843	(shift @post_detect)->() while @post_detect;	1186	(shift @post_detect)->() while @post_detect;
844	}	1187	}
845		1188
846	$MODEL	1189	$MODEL
…		…
848		1191
849	sub AUTOLOAD {	1192	sub AUTOLOAD {
850	(my $func = $AUTOLOAD) =~ s/.*://;	1193	(my $func = $AUTOLOAD) =~ s/.*://;
851		1194
852	$method{$func}	1195	$method{$func}
853	or croak "$func: not a valid method for AnyEvent objects";	1196	or Carp::croak "$func: not a valid method for AnyEvent objects";
854		1197
855	detect unless $MODEL;	1198	detect unless $MODEL;
856		1199
857	my $class = shift;	1200	my $class = shift;
858	$class->$func (@_);	1201	$class->$func (@_);
859	}	1202	}
860		1203
		1204	# utility function to dup a filehandle. this is used by many backends
		1205	# to support binding more than one watcher per filehandle (they usually
		1206	# allow only one watcher per fd, so we dup it to get a different one).
		1207	sub _dupfh($$;$$) {
		1208	my ($poll, $fh, $r, $w) = @_;
		1209
		1210	# cygwin requires the fh mode to be matching, unix doesn't
		1211	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1212
		1213	open my $fh2, $mode, $fh
		1214	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1215
		1216	# we assume CLOEXEC is already set by perl in all important cases
		1217
		1218	($fh2, $rw)
		1219	}
		1220
861	package AnyEvent::Base;	1221	package AnyEvent::Base;
862		1222
		1223	# default implementations for many methods
		1224
		1225	sub _time {
		1226	# probe for availability of Time::HiRes
		1227	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1228	warn "AnyEvent: using Time::HiRes for sub-second timing accuracy.\n" if $VERBOSE >= 8;
		1229	*_time = \&Time::HiRes::time;
		1230	# if (eval "use POSIX (); (POSIX::times())...
		1231	} else {
		1232	warn "AnyEvent: using built-in time(), WARNING, no sub-second resolution!\n" if $VERBOSE;
		1233	*_time = sub { time }; # epic fail
		1234	}
		1235
		1236	&_time
		1237	}
		1238
		1239	sub time { _time }
		1240	sub now { _time }
		1241	sub now_update { }
		1242
863	# default implementation for ->condvar	1243	# default implementation for ->condvar
864		1244
865	sub condvar {	1245	sub condvar {
866	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, AnyEvent::CondVar::	1246	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
867	}	1247	}
868		1248
869	# default implementation for ->signal	1249	# default implementation for ->signal
870		1250
871	our %SIG_CB;	1251	our $HAVE_ASYNC_INTERRUPT;
		1252	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1253	our (%SIG_ASY, %SIG_ASY_W);
		1254	our ($SIG_COUNT, $SIG_TW);
872		1255
		1256	sub _signal_exec {
		1257	$HAVE_ASYNC_INTERRUPT
		1258	? $SIGPIPE_R->drain
		1259	: sysread $SIGPIPE_R, my $dummy, 9;
		1260
		1261	while (%SIG_EV) {
		1262	for (keys %SIG_EV) {
		1263	delete $SIG_EV{$_};
		1264	$_->() for values %{ $SIG_CB{$_} || {} };
		1265	}
		1266	}
		1267	}
		1268
873	sub signal {	1269	sub _signal {
874	my (undef, %arg) = @_;	1270	my (undef, %arg) = @_;
875		1271
876	my $signal = uc $arg{signal}	1272	my $signal = uc $arg{signal}
877	or Carp::croak "required option 'signal' is missing";	1273	or Carp::croak "required option 'signal' is missing";
878		1274
879	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1275	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1276
		1277	if ($HAVE_ASYNC_INTERRUPT) {
		1278	# async::interrupt
		1279
		1280	$SIG_ASY{$signal} ||= do {
		1281	my $asy = new Async::Interrupt
		1282	cb => sub { undef $SIG_EV{$signal} },
		1283	signal => $signal,
		1284	pipe => [$SIGPIPE_R->filenos],
		1285	;
		1286	$asy->pipe_autodrain (0);
		1287
		1288	$asy
		1289	};
		1290
		1291	} else {
		1292	# pure perl
		1293
880	$SIG{$signal} ||= sub {	1294	$SIG{$signal} ||= sub {
881	$_->() for values %{ $SIG_CB{$signal} || {} };	1295	local $!;
		1296	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1297	undef $SIG_EV{$signal};
		1298	};
		1299
		1300	# can't do signal processing without introducing races in pure perl,
		1301	# so limit the signal latency.
		1302	++$SIG_COUNT;
		1303	$SIG_TW ||= AnyEvent->timer (
		1304	after => $MAX_SIGNAL_LATENCY,
		1305	interval => $MAX_SIGNAL_LATENCY,
		1306	cb => sub { }, # just for the PERL_ASYNC_CHECK
		1307	);
882	};	1308	}
883		1309
884	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1310	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
885	}	1311	}
886		1312
		1313	sub signal {
		1314	# probe for availability of Async::Interrupt
		1315	if (!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT} && eval "use Async::Interrupt 0.6 (); 1") {
		1316	warn "AnyEvent: using Async::Interrupt for race-free signal handling.\n" if $VERBOSE >= 8;
		1317
		1318	$HAVE_ASYNC_INTERRUPT = 1;
		1319	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1320	$SIG_IO = AnyEvent->io (fh => $SIGPIPE_R->fileno, poll => "r", cb => \&_signal_exec);
		1321
		1322	} else {
		1323	warn "AnyEvent: using emulated perl signal handling with latency timer.\n" if $VERBOSE >= 8;
		1324
		1325	require Fcntl;
		1326
		1327	if (AnyEvent::WIN32) {
		1328	require AnyEvent::Util;
		1329
		1330	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1331	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R) if $SIGPIPE_R;
		1332	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W) if $SIGPIPE_W; # just in case
		1333	} else {
		1334	pipe $SIGPIPE_R, $SIGPIPE_W;
		1335	fcntl $SIGPIPE_R, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_R;
		1336	fcntl $SIGPIPE_W, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_W; # just in case
		1337
		1338	# not strictly required, as $^F is normally 2, but let's make sure...
		1339	fcntl $SIGPIPE_R, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1340	fcntl $SIGPIPE_W, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1341	}
		1342
		1343	$SIGPIPE_R
		1344	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1345
		1346	$SIG_IO = AnyEvent->io (fh => $SIGPIPE_R, poll => "r", cb => \&_signal_exec);
		1347	}
		1348
		1349	*signal = \&_signal;
		1350	&signal
		1351	}
		1352
887	sub AnyEvent::Base::Signal::DESTROY {	1353	sub AnyEvent::Base::signal::DESTROY {
888	my ($signal, $cb) = @{$_[0]};	1354	my ($signal, $cb) = @{$_[0]};
889		1355
		1356	undef $SIG_TW
		1357	unless --$SIG_COUNT;
		1358
890	delete $SIG_CB{$signal}{$cb};	1359	delete $SIG_CB{$signal}{$cb};
891		1360
892	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };	1361	# delete doesn't work with older perls - they then
		1362	# print weird messages, or just unconditionally exit
		1363	# instead of getting the default action.
		1364	undef $SIG{$signal}
		1365	unless keys %{ $SIG_CB{$signal} };
893	}	1366	}
894		1367
895	# default implementation for ->child	1368	# default implementation for ->child
896		1369
897	our %PID_CB;	1370	our %PID_CB;
898	our $CHLD_W;	1371	our $CHLD_W;
899	our $CHLD_DELAY_W;	1372	our $CHLD_DELAY_W;
900	our $PID_IDLE;
901	our $WNOHANG;	1373	our $WNOHANG;
902		1374
903	sub _child_wait {	1375	sub _sigchld {
904	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1376	while (0 < (my $pid = waitpid -1, $WNOHANG)) {
		1377	$_->($pid, $?)
905	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1378	for values %{ $PID_CB{$pid} || {} },
906	(values %{ $PID_CB{0} || {} });	1379	values %{ $PID_CB{0} || {} };
907	}	1380	}
908
909	undef $PID_IDLE;
910	}
911
912	sub _sigchld {
913	# make sure we deliver these changes "synchronous" with the event loop.
914	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {
915	undef $CHLD_DELAY_W;
916	&_child_wait;
917	});
918	}	1381	}
919		1382
920	sub child {	1383	sub child {
921	my (undef, %arg) = @_;	1384	my (undef, %arg) = @_;
922		1385
923	defined (my $pid = $arg{pid} + 0)	1386	defined (my $pid = $arg{pid} + 0)
924	or Carp::croak "required option 'pid' is missing";	1387	or Carp::croak "required option 'pid' is missing";
925		1388
926	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1389	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
927		1390
928	unless ($WNOHANG) {
929	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;	1391	$WNOHANG ||= eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
930	}
931		1392
932	unless ($CHLD_W) {	1393	unless ($CHLD_W) {
933	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1394	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
934	# child could be a zombie already, so make at least one round	1395	# child could be a zombie already, so make at least one round
935	&_sigchld;	1396	&_sigchld;
936	}	1397	}
937		1398
938	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	1399	bless [$pid, $arg{cb}], "AnyEvent::Base::child"
939	}	1400	}
940		1401
941	sub AnyEvent::Base::Child::DESTROY {	1402	sub AnyEvent::Base::child::DESTROY {
942	my ($pid, $cb) = @{$_[0]};	1403	my ($pid, $cb) = @{$_[0]};
943		1404
944	delete $PID_CB{$pid}{$cb};	1405	delete $PID_CB{$pid}{$cb};
945	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1406	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
946		1407
947	undef $CHLD_W unless keys %PID_CB;	1408	undef $CHLD_W unless keys %PID_CB;
		1409	}
		1410
		1411	# idle emulation is done by simply using a timer, regardless
		1412	# of whether the process is idle or not, and not letting
		1413	# the callback use more than 50% of the time.
		1414	sub idle {
		1415	my (undef, %arg) = @_;
		1416
		1417	my ($cb, $w, $rcb) = $arg{cb};
		1418
		1419	$rcb = sub {
		1420	if ($cb) {
		1421	$w = _time;
		1422	&$cb;
		1423	$w = _time - $w;
		1424
		1425	# never use more then 50% of the time for the idle watcher,
		1426	# within some limits
		1427	$w = 0.0001 if $w < 0.0001;
		1428	$w = 5 if $w > 5;
		1429
		1430	$w = AnyEvent->timer (after => $w, cb => $rcb);
		1431	} else {
		1432	# clean up...
		1433	undef $w;
		1434	undef $rcb;
		1435	}
		1436	};
		1437
		1438	$w = AnyEvent->timer (after => 0.05, cb => $rcb);
		1439
		1440	bless \\$cb, "AnyEvent::Base::idle"
		1441	}
		1442
		1443	sub AnyEvent::Base::idle::DESTROY {
		1444	undef $${$_[0]};
948	}	1445	}
949		1446
950	package AnyEvent::CondVar;	1447	package AnyEvent::CondVar;
951		1448
952	our @ISA = AnyEvent::CondVar::Base::;	1449	our @ISA = AnyEvent::CondVar::Base::;
…		…
954	package AnyEvent::CondVar::Base;	1451	package AnyEvent::CondVar::Base;
955		1452
956	use overload	1453	use overload
957	'&{}' => sub { my $self = shift; sub { $self->send (@_) } },	1454	'&{}' => sub { my $self = shift; sub { $self->send (@_) } },
958	fallback => 1;	1455	fallback => 1;
		1456
		1457	our $WAITING;
959		1458
960	sub _send {	1459	sub _send {
961	# nop	1460	# nop
962	}	1461	}
963		1462
…		…
976	sub ready {	1475	sub ready {
977	$_[0]{_ae_sent}	1476	$_[0]{_ae_sent}
978	}	1477	}
979		1478
980	sub _wait {	1479	sub _wait {
		1480	$WAITING
		1481	and !$_[0]{_ae_sent}
		1482	and Carp::croak "AnyEvent::CondVar: recursive blocking wait detected";
		1483
		1484	local $WAITING = 1;
981	AnyEvent->one_event while !$_[0]{_ae_sent};	1485	AnyEvent->one_event while !$_[0]{_ae_sent};
982	}	1486	}
983		1487
984	sub recv {	1488	sub recv {
985	$_[0]->_wait;	1489	$_[0]->_wait;
…		…
1004	}	1508	}
1005		1509
1006	# undocumented/compatibility with pre-3.4	1510	# undocumented/compatibility with pre-3.4
1007	*broadcast = \&send;	1511	*broadcast = \&send;
1008	*wait = \&_wait;	1512	*wait = \&_wait;
		1513
		1514	=head1 ERROR AND EXCEPTION HANDLING
		1515
		1516	In general, AnyEvent does not do any error handling - it relies on the
		1517	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1518	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1519	checking of all AnyEvent methods, however, which is highly useful during
		1520	development.
		1521
		1522	As for exception handling (i.e. runtime errors and exceptions thrown while
		1523	executing a callback), this is not only highly event-loop specific, but
		1524	also not in any way wrapped by this module, as this is the job of the main
		1525	program.
		1526
		1527	The pure perl event loop simply re-throws the exception (usually
		1528	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1529	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1530	so on.
		1531
		1532	=head1 ENVIRONMENT VARIABLES
		1533
		1534	The following environment variables are used by this module or its
		1535	submodules.
		1536
		1537	Note that AnyEvent will remove I<all> environment variables starting with
		1538	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		1539	enabled.
		1540
		1541	=over 4
		1542
		1543	=item C<PERL_ANYEVENT_VERBOSE>
		1544
		1545	By default, AnyEvent will be completely silent except in fatal
		1546	conditions. You can set this environment variable to make AnyEvent more
		1547	talkative.
		1548
		1549	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1550	conditions, such as not being able to load the event model specified by
		1551	C<PERL_ANYEVENT_MODEL>.
		1552
		1553	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1554	model it chooses.
		1555
		1556	=item C<PERL_ANYEVENT_STRICT>
		1557
		1558	AnyEvent does not do much argument checking by default, as thorough
		1559	argument checking is very costly. Setting this variable to a true value
		1560	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1561	check the arguments passed to most method calls. If it finds any problems,
		1562	it will croak.
		1563
		1564	In other words, enables "strict" mode.
		1565
		1566	Unlike C<use strict>, it is definitely recommended to keep it off in
		1567	production. Keeping C<PERL_ANYEVENT_STRICT=1> in your environment while
		1568	developing programs can be very useful, however.
		1569
		1570	=item C<PERL_ANYEVENT_MODEL>
		1571
		1572	This can be used to specify the event model to be used by AnyEvent, before
		1573	auto detection and -probing kicks in. It must be a string consisting
		1574	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1575	and the resulting module name is loaded and if the load was successful,
		1576	used as event model. If it fails to load AnyEvent will proceed with
		1577	auto detection and -probing.
		1578
		1579	This functionality might change in future versions.
		1580
		1581	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1582	could start your program like this:
		1583
		1584	PERL_ANYEVENT_MODEL=Perl perl ...
		1585
		1586	=item C<PERL_ANYEVENT_PROTOCOLS>
		1587
		1588	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1589	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1590	of auto probing).
		1591
		1592	Must be set to a comma-separated list of protocols or address families,
		1593	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1594	used, and preference will be given to protocols mentioned earlier in the
		1595	list.
		1596
		1597	This variable can effectively be used for denial-of-service attacks
		1598	against local programs (e.g. when setuid), although the impact is likely
		1599	small, as the program has to handle conenction and other failures anyways.
		1600
		1601	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1602	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1603	- only support IPv4, never try to resolve or contact IPv6
		1604	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1605	IPv6, but prefer IPv6 over IPv4.
		1606
		1607	=item C<PERL_ANYEVENT_EDNS0>
		1608
		1609	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1610	for DNS. This extension is generally useful to reduce DNS traffic, but
		1611	some (broken) firewalls drop such DNS packets, which is why it is off by
		1612	default.
		1613
		1614	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1615	EDNS0 in its DNS requests.
		1616
		1617	=item C<PERL_ANYEVENT_MAX_FORKS>
		1618
		1619	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1620	will create in parallel.
		1621
		1622	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		1623
		1624	The default value for the C<max_outstanding> parameter for the default DNS
		1625	resolver - this is the maximum number of parallel DNS requests that are
		1626	sent to the DNS server.
		1627
		1628	=item C<PERL_ANYEVENT_RESOLV_CONF>
		1629
		1630	The file to use instead of F</etc/resolv.conf> (or OS-specific
		1631	configuration) in the default resolver. When set to the empty string, no
		1632	default config will be used.
		1633
		1634	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		1635
		1636	When neither C<ca_file> nor C<ca_path> was specified during
		1637	L<AnyEvent::TLS> context creation, and either of these environment
		1638	variables exist, they will be used to specify CA certificate locations
		1639	instead of a system-dependent default.
		1640
		1641	=back
1009		1642
1010	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1643	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
1011		1644
1012	This is an advanced topic that you do not normally need to use AnyEvent in	1645	This is an advanced topic that you do not normally need to use AnyEvent in
1013	a module. This section is only of use to event loop authors who want to	1646	a module. This section is only of use to event loop authors who want to
…		…
1047		1680
1048	I<rxvt-unicode> also cheats a bit by not providing blocking access to	1681	I<rxvt-unicode> also cheats a bit by not providing blocking access to
1049	condition variables: code blocking while waiting for a condition will	1682	condition variables: code blocking while waiting for a condition will
1050	C<die>. This still works with most modules/usages, and blocking calls must	1683	C<die>. This still works with most modules/usages, and blocking calls must
1051	not be done in an interactive application, so it makes sense.	1684	not be done in an interactive application, so it makes sense.
1052
1053	=head1 ENVIRONMENT VARIABLES
1054
1055	The following environment variables are used by this module:
1056
1057	=over 4
1058
1059	=item C<PERL_ANYEVENT_VERBOSE>
1060
1061	By default, AnyEvent will be completely silent except in fatal
1062	conditions. You can set this environment variable to make AnyEvent more
1063	talkative.
1064
1065	When set to C<1> or higher, causes AnyEvent to warn about unexpected
1066	conditions, such as not being able to load the event model specified by
1067	C<PERL_ANYEVENT_MODEL>.
1068
1069	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
1070	model it chooses.
1071
1072	=item C<PERL_ANYEVENT_MODEL>
1073
1074	This can be used to specify the event model to be used by AnyEvent, before
1075	auto detection and -probing kicks in. It must be a string consisting
1076	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
1077	and the resulting module name is loaded and if the load was successful,
1078	used as event model. If it fails to load AnyEvent will proceed with
1079	auto detection and -probing.
1080
1081	This functionality might change in future versions.
1082
1083	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
1084	could start your program like this:
1085
1086	PERL_ANYEVENT_MODEL=Perl perl ...
1087
1088	=item C<PERL_ANYEVENT_PROTOCOLS>
1089
1090	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
1091	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
1092	of auto probing).
1093
1094	Must be set to a comma-separated list of protocols or address families,
1095	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
1096	used, and preference will be given to protocols mentioned earlier in the
1097	list.
1098
1099	This variable can effectively be used for denial-of-service attacks
1100	against local programs (e.g. when setuid), although the impact is likely
1101	small, as the program has to handle connection errors already-
1102
1103	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
1104	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
1105	- only support IPv4, never try to resolve or contact IPv6
1106	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
1107	IPv6, but prefer IPv6 over IPv4.
1108
1109	=item C<PERL_ANYEVENT_EDNS0>
1110
1111	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
1112	for DNS. This extension is generally useful to reduce DNS traffic, but
1113	some (broken) firewalls drop such DNS packets, which is why it is off by
1114	default.
1115
1116	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
1117	EDNS0 in its DNS requests.
1118
1119	=back
1120		1685
1121	=head1 EXAMPLE PROGRAM	1686	=head1 EXAMPLE PROGRAM
1122		1687
1123	The following program uses an I/O watcher to read data from STDIN, a timer	1688	The following program uses an I/O watcher to read data from STDIN, a timer
1124	to display a message once per second, and a condition variable to quit the	1689	to display a message once per second, and a condition variable to quit the
…		…
1318	watcher.	1883	watcher.
1319		1884
1320	=head3 Results	1885	=head3 Results
1321		1886
1322	name watchers bytes create invoke destroy comment	1887	name watchers bytes create invoke destroy comment
1323	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	1888	EV/EV 400000 224 0.47 0.35 0.27 EV native interface
1324	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	1889	EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers
1325	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	1890	CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal
1326	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	1891	Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation
1327	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	1892	Event/Event 16000 517 32.20 31.80 0.81 Event native interface
1328	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers	1893	Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers
		1894	IOAsync/Any 16000 989 38.10 32.77 11.13 via IO::Async::Loop::IO_Poll
		1895	IOAsync/Any 16000 990 37.59 29.50 10.61 via IO::Async::Loop::Epoll
1329	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	1896	Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour
1330	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	1897	Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers
1331	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	1898	POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event
1332	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	1899	POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select
1333		1900
1334	=head3 Discussion	1901	=head3 Discussion
1335		1902
1336	The benchmark does I<not> measure scalability of the event loop very	1903	The benchmark does I<not> measure scalability of the event loop very
1337	well. For example, a select-based event loop (such as the pure perl one)	1904	well. For example, a select-based event loop (such as the pure perl one)
…		…
1362	performance becomes really bad with lots of file descriptors (and few of	1929	performance becomes really bad with lots of file descriptors (and few of
1363	them active), of course, but this was not subject of this benchmark.	1930	them active), of course, but this was not subject of this benchmark.
1364		1931
1365	The C<Event> module has a relatively high setup and callback invocation	1932	The C<Event> module has a relatively high setup and callback invocation
1366	cost, but overall scores in on the third place.	1933	cost, but overall scores in on the third place.
		1934
		1935	C<IO::Async> performs admirably well, about on par with C<Event>, even
		1936	when using its pure perl backend.
1367		1937
1368	C<Glib>'s memory usage is quite a bit higher, but it features a	1938	C<Glib>'s memory usage is quite a bit higher, but it features a
1369	faster callback invocation and overall ends up in the same class as	1939	faster callback invocation and overall ends up in the same class as
1370	C<Event>. However, Glib scales extremely badly, doubling the number of	1940	C<Event>. However, Glib scales extremely badly, doubling the number of
1371	watchers increases the processing time by more than a factor of four,	1941	watchers increases the processing time by more than a factor of four,
…		…
1449	it to another server. This includes deleting the old timeout and creating	2019	it to another server. This includes deleting the old timeout and creating
1450	a new one that moves the timeout into the future.	2020	a new one that moves the timeout into the future.
1451		2021
1452	=head3 Results	2022	=head3 Results
1453		2023
1454	name sockets create request	2024	name sockets create request
1455	EV 20000 69.01 11.16	2025	EV 20000 69.01 11.16
1456	Perl 20000 73.32 35.87	2026	Perl 20000 73.32 35.87
		2027	IOAsync 20000 157.00 98.14 epoll
		2028	IOAsync 20000 159.31 616.06 poll
1457	Event 20000 212.62 257.32	2029	Event 20000 212.62 257.32
1458	Glib 20000 651.16 1896.30	2030	Glib 20000 651.16 1896.30
1459	POE 20000 349.67 12317.24 uses POE::Loop::Event	2031	POE 20000 349.67 12317.24 uses POE::Loop::Event
1460		2032
1461	=head3 Discussion	2033	=head3 Discussion
1462		2034
1463	This benchmark I<does> measure scalability and overall performance of the	2035	This benchmark I<does> measure scalability and overall performance of the
1464	particular event loop.	2036	particular event loop.
…		…
1466	EV is again fastest. Since it is using epoll on my system, the setup time	2038	EV is again fastest. Since it is using epoll on my system, the setup time
1467	is relatively high, though.	2039	is relatively high, though.
1468		2040
1469	Perl surprisingly comes second. It is much faster than the C-based event	2041	Perl surprisingly comes second. It is much faster than the C-based event
1470	loops Event and Glib.	2042	loops Event and Glib.
		2043
		2044	IO::Async performs very well when using its epoll backend, and still quite
		2045	good compared to Glib when using its pure perl backend.
1471		2046
1472	Event suffers from high setup time as well (look at its code and you will	2047	Event suffers from high setup time as well (look at its code and you will
1473	understand why). Callback invocation also has a high overhead compared to	2048	understand why). Callback invocation also has a high overhead compared to
1474	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event	2049	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
1475	uses select or poll in basically all documented configurations.	2050	uses select or poll in basically all documented configurations.
…		…
1538	=item * C-based event loops perform very well with small number of	2113	=item * C-based event loops perform very well with small number of
1539	watchers, as the management overhead dominates.	2114	watchers, as the management overhead dominates.
1540		2115
1541	=back	2116	=back
1542		2117
		2118	=head2 THE IO::Lambda BENCHMARK
		2119
		2120	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2121	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2122	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2123	shouldn't come as a surprise to anybody). As such, the benchmark is
		2124	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2125	very optimal. But how would AnyEvent compare when used without the extra
		2126	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2127
		2128	The benchmark itself creates an echo-server, and then, for 500 times,
		2129	connects to the echo server, sends a line, waits for the reply, and then
		2130	creates the next connection. This is a rather bad benchmark, as it doesn't
		2131	test the efficiency of the framework or much non-blocking I/O, but it is a
		2132	benchmark nevertheless.
		2133
		2134	name runtime
		2135	Lambda/select 0.330 sec
		2136	+ optimized 0.122 sec
		2137	Lambda/AnyEvent 0.327 sec
		2138	+ optimized 0.138 sec
		2139	Raw sockets/select 0.077 sec
		2140	POE/select, components 0.662 sec
		2141	POE/select, raw sockets 0.226 sec
		2142	POE/select, optimized 0.404 sec
		2143
		2144	AnyEvent/select/nb 0.085 sec
		2145	AnyEvent/EV/nb 0.068 sec
		2146	+state machine 0.134 sec
		2147
		2148	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2149	benchmarks actually make blocking connects and use 100% blocking I/O,
		2150	defeating the purpose of an event-based solution. All of the newly
		2151	written AnyEvent benchmarks use 100% non-blocking connects (using
		2152	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2153	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2154	generally require a lot more bookkeeping and event handling than blocking
		2155	connects (which involve a single syscall only).
		2156
		2157	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2158	offers similar expressive power as POE and IO::Lambda, using conventional
		2159	Perl syntax. This means that both the echo server and the client are 100%
		2160	non-blocking, further placing it at a disadvantage.
		2161
		2162	As you can see, the AnyEvent + EV combination even beats the
		2163	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2164	backend easily beats IO::Lambda and POE.
		2165
		2166	And even the 100% non-blocking version written using the high-level (and
		2167	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda by a
		2168	large margin, even though it does all of DNS, tcp-connect and socket I/O
		2169	in a non-blocking way.
		2170
		2171	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2172	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2173	part of the IO::lambda distribution and were used without any changes.
		2174
		2175
		2176	=head1 SIGNALS
		2177
		2178	AnyEvent currently installs handlers for these signals:
		2179
		2180	=over 4
		2181
		2182	=item SIGCHLD
		2183
		2184	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2185	emulation for event loops that do not support them natively. Also, some
		2186	event loops install a similar handler.
		2187
		2188	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2189	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2190
		2191	=item SIGPIPE
		2192
		2193	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2194	when AnyEvent gets loaded.
		2195
		2196	The rationale for this is that AnyEvent users usually do not really depend
		2197	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2198	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2199	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2200	some random socket.
		2201
		2202	The rationale for installing a no-op handler as opposed to ignoring it is
		2203	that this way, the handler will be restored to defaults on exec.
		2204
		2205	Feel free to install your own handler, or reset it to defaults.
		2206
		2207	=back
		2208
		2209	=cut
		2210
		2211	undef $SIG{CHLD}
		2212	if $SIG{CHLD} eq 'IGNORE';
		2213
		2214	$SIG{PIPE} = sub { }
		2215	unless defined $SIG{PIPE};
		2216
		2217	=head1 RECOMMENDED/OPTIONAL MODULES
		2218
		2219	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2220	it's built-in modules) are required to use it.
		2221
		2222	That does not mean that AnyEvent won't take advantage of some additional
		2223	modules if they are installed.
		2224
		2225	This section epxlains which additional modules will be used, and how they
		2226	affect AnyEvent's operetion.
		2227
		2228	=over 4
		2229
		2230	=item L<Async::Interrupt>
		2231
		2232	This slightly arcane module is used to implement fast signal handling: To
		2233	my knowledge, there is no way to do completely race-free and quick
		2234	signal handling in pure perl. To ensure that signals still get
		2235	delivered, AnyEvent will start an interval timer to wake up perl (and
		2236	catch the signals) with soemd elay (default is 10 seconds, look for
		2237	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2238
		2239	If this module is available, then it will be used to implement signal
		2240	catching, which means that signals will not be delayed, and the event loop
		2241	will not be interrupted regularly, which is more efficient (And good for
		2242	battery life on laptops).
		2243
		2244	This affects not just the pure-perl event loop, but also other event loops
		2245	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2246
		2247	=item L<EV>
		2248
		2249	This module isn't really "optional", as it is simply one of the backend
		2250	event loops that AnyEvent can use. However, it is simply the best event
		2251	loop available in terms of features, speed and stability: It supports
		2252	the AnyEvent API optimally, implements all the watcher types in XS, does
		2253	automatic timer adjustments even when no monotonic clock is available,
		2254	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2255	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2256	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2257
		2258	=item L<Guard>
		2259
		2260	The guard module, when used, will be used to implement
		2261	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2262	lot less memory), but otherwise doesn't affect guard operation much. It is
		2263	purely used for performance.
		2264
		2265	=item L<JSON> and L<JSON::XS>
		2266
		2267	This module is required when you want to read or write JSON data via
		2268	L<AnyEvent::Handle>. It is also written in pure-perl, but can take
		2269	advantage of the ulta-high-speed L<JSON::XS> module when it is installed.
		2270
		2271	In fact, L<AnyEvent::Handle> will use L<JSON::XS> by default if it is
		2272	installed.
		2273
		2274	=item L<Net::SSLeay>
		2275
		2276	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2277	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2278	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2279
		2280	=item L<Time::HiRes>
		2281
		2282	This module is part of perl since release 5.008. It will be used when the
		2283	chosen event library does not come with a timing source on it's own. The
		2284	pure-perl event loop (L<AnyEvent::Impl::Perl>) will additionally use it to
		2285	try to use a monotonic clock for timing stability.
		2286
		2287	=back
		2288
1543		2289
1544	=head1 FORK	2290	=head1 FORK
1545		2291
1546	Most event libraries are not fork-safe. The ones who are usually are	2292	Most event libraries are not fork-safe. The ones who are usually are
1547	because they rely on inefficient but fork-safe C<select> or C<poll>	2293	because they rely on inefficient but fork-safe C<select> or C<poll>
1548	calls. Only L<EV> is fully fork-aware.	2294	calls. Only L<EV> is fully fork-aware.
1549		2295
1550	If you have to fork, you must either do so I<before> creating your first	2296	If you have to fork, you must either do so I<before> creating your first
1551	watcher OR you must not use AnyEvent at all in the child.	2297	watcher OR you must not use AnyEvent at all in the child OR you must do
		2298	something completely out of the scope of AnyEvent.
1552		2299
1553		2300
1554	=head1 SECURITY CONSIDERATIONS	2301	=head1 SECURITY CONSIDERATIONS
1555		2302
1556	AnyEvent can be forced to load any event model via	2303	AnyEvent can be forced to load any event model via
…		…
1561	specified in the variable.	2308	specified in the variable.
1562		2309
1563	You can make AnyEvent completely ignore this variable by deleting it	2310	You can make AnyEvent completely ignore this variable by deleting it
1564	before the first watcher gets created, e.g. with a C<BEGIN> block:	2311	before the first watcher gets created, e.g. with a C<BEGIN> block:
1565		2312
1566	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	2313	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1567		2314
1568	use AnyEvent;	2315	use AnyEvent;
1569		2316
1570	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can	2317	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1571	be used to probe what backend is used and gain other information (which is	2318	be used to probe what backend is used and gain other information (which is
1572	probably even less useful to an attacker than PERL_ANYEVENT_MODEL).	2319	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2320	$ENV{PERL_ANYEVENT_STRICT}.
		2321
		2322	Note that AnyEvent will remove I<all> environment variables starting with
		2323	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2324	enabled.
		2325
		2326
		2327	=head1 BUGS
		2328
		2329	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2330	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2331	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2332	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2333	pronounced).
1573		2334
1574		2335
1575	=head1 SEE ALSO	2336	=head1 SEE ALSO
1576		2337
1577	Utility functions: L<AnyEvent::Util>.	2338	Utility functions: L<AnyEvent::Util>.
…		…
1580	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.	2341	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
1581		2342
1582	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,	2343	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
1583	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,	2344	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
1584	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,	2345	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1585	L<AnyEvent::Impl::POE>.	2346	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>.
1586		2347
1587	Non-blocking file handles, sockets, TCP clients and	2348	Non-blocking file handles, sockets, TCP clients and
1588	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>.	2349	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
1589		2350
1590	Asynchronous DNS: L<AnyEvent::DNS>.	2351	Asynchronous DNS: L<AnyEvent::DNS>.
1591		2352
1592	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,	2353	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>,
		2354	L<Coro::Event>,
1593		2355
1594	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>, L<AnyEvent::DNS>.	2356	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::XMPP>,
		2357	L<AnyEvent::HTTP>.
1595		2358
1596		2359
1597	=head1 AUTHOR	2360	=head1 AUTHOR
1598		2361
1599	Marc Lehmann <schmorp@schmorp.de>	2362	Marc Lehmann <schmorp@schmorp.de>
1600	http://home.schmorp.de/	2363	http://home.schmorp.de/
1601		2364
1602	=cut	2365	=cut
1603		2366
1604	1	2367	1
1605		2368

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