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Revision 1.232 by root, Thu Jul 9 01:08:22 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
		35	$w->send; # wake up current and all future recv's
20	$w->wait; # enters "main loop" till $condvar gets ->send	36	$w->recv; # enters "main loop" till $condvar gets ->send
21	$w->send; # wake up current and all future wait's	37	# use a condvar in callback mode:
		38	$w->cb (sub { $_[0]->recv });
		39
		40	=head1 INTRODUCTION/TUTORIAL
		41
		42	This manpage is mainly a reference manual. If you are interested
		43	in a tutorial or some gentle introduction, have a look at the
		44	L<AnyEvent::Intro> manpage.
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 enourmous 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
113	the callback to call, the filehandle to watch, etc.	143	the callback to call, the file handle to watch, etc.
114		144
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
242	Multiple signal occurances can be clumped together into one callback	360	Multiple signal occurrences can be clumped together into one callback
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 guarenteed 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.
249		367
250	This watcher might use C<%SIG>, so programs overwriting those signals	368	This watcher might use C<%SIG>, so programs overwriting those signals
…		…
257	=head2 CHILD PROCESS WATCHERS	375	=head2 CHILD PROCESS WATCHERS
258		376
259	You can also watch on a child process exit and catch its exit status.	377	You can also watch on a child process exit and catch its exit status.
260		378
261	The child process is specified by the C<pid> argument (if set to C<0>, it	379	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	380	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	381	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	382	any trace events (stopped/continued).
265	and exit status (as returned by waitpid), so unlike other watcher types,	383
266	you I<can> rely on child watcher callback arguments.	384	The callback will be called with the pid and exit status (as returned by
		385	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		386	callback arguments.
		387
		388	This watcher type works by installing a signal handler for C<SIGCHLD>,
		389	and since it cannot be shared, nothing else should use SIGCHLD or reap
		390	random child processes (waiting for specific child processes, e.g. inside
		391	C<system>, is just fine).
267		392
268	There is a slight catch to child watchers, however: you usually start them	393	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	394	I<after> the child process was created, and this means the process could
270	have exited already (and no SIGCHLD will be sent anymore).	395	have exited already (and no SIGCHLD will be sent anymore).
271		396
272	Not all event models handle this correctly (POE doesn't), but even for	397	Not all event models handle this correctly (neither POE nor IO::Async do,
		398	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	399	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).	400	the process exits (i.e. before you fork in the first place). AnyEvent's
		401	pure perl event loop handles all cases correctly regardless of when you
		402	start the watcher.
275		403
276	This means you cannot create a child watcher as the very first thing in an	404	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	405	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>).	406	watcher before you C<fork> the child (alternatively, you can call
		407	C<AnyEvent::detect>).
279		408
280	Example: fork a process and wait for it	409	Example: fork a process and wait for it
281		410
282	my $done = AnyEvent->condvar;	411	my $done = AnyEvent->condvar;
283		412
284	AnyEvent::detect; # force event module to be initialised
285
286	my $pid = fork or exit 5;	413	my $pid = fork or exit 5;
287		414
288	my $w = AnyEvent->child (	415	my $w = AnyEvent->child (
289	pid => $pid,	416	pid => $pid,
290	cb => sub {	417	cb => sub {
291	my ($pid, $status) = @_;	418	my ($pid, $status) = @_;
292	warn "pid $pid exited with status $status";	419	warn "pid $pid exited with status $status";
293	$done->send;	420	$done->send;
294	},	421	},
295	);	422	);
296		423
297	# do something else, then wait for process exit	424	# do something else, then wait for process exit
298	$done->wait;	425	$done->recv;
		426
		427	=head2 IDLE WATCHERS
		428
		429	Sometimes there is a need to do something, but it is not so important
		430	to do it instantly, but only when there is nothing better to do. This
		431	"nothing better to do" is usually defined to be "no other events need
		432	attention by the event loop".
		433
		434	Idle watchers ideally get invoked when the event loop has nothing
		435	better to do, just before it would block the process to wait for new
		436	events. Instead of blocking, the idle watcher is invoked.
		437
		438	Most event loops unfortunately do not really support idle watchers (only
		439	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		440	will simply call the callback "from time to time".
		441
		442	Example: read lines from STDIN, but only process them when the
		443	program is otherwise idle:
		444
		445	my @lines; # read data
		446	my $idle_w;
		447	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		448	push @lines, scalar <STDIN>;
		449
		450	# start an idle watcher, if not already done
		451	$idle_w ||= AnyEvent->idle (cb => sub {
		452	# handle only one line, when there are lines left
		453	if (my $line = shift @lines) {
		454	print "handled when idle: $line";
		455	} else {
		456	# otherwise disable the idle watcher again
		457	undef $idle_w;
		458	}
		459	});
		460	});
299		461
300	=head2 CONDITION VARIABLES	462	=head2 CONDITION VARIABLES
301		463
302	If you are familiar with some event loops you will know that all of them	464	If you are familiar with some event loops you will know that all of them
303	require you to run some blocking "loop", "run" or similar function that	465	require you to run some blocking "loop", "run" or similar function that
…		…
309	The instrument to do that is called a "condition variable", so called	471	The instrument to do that is called a "condition variable", so called
310	because they represent a condition that must become true.	472	because they represent a condition that must become true.
311		473
312	Condition variables can be created by calling the C<< AnyEvent->condvar	474	Condition variables can be created by calling the C<< AnyEvent->condvar
313	>> method, usually without arguments. The only argument pair allowed is	475	>> method, usually without arguments. The only argument pair allowed is
		476
314	C<cb>, which specifies a callback to be called when the condition variable	477	C<cb>, which specifies a callback to be called when the condition variable
315	becomes true.	478	becomes true, with the condition variable as the first argument (but not
		479	the results).
316		480
317	After creation, the conditon variable is "false" until it becomes "true"	481	After creation, the condition variable is "false" until it becomes "true"
318	by calling the C<send> method.	482	by calling the C<send> method (or calling the condition variable as if it
		483	were a callback, read about the caveats in the description for the C<<
		484	->send >> method).
319		485
320	Condition variables are similar to callbacks, except that you can	486	Condition variables are similar to callbacks, except that you can
321	optionally wait for them. They can also be called merge points - points	487	optionally wait for them. They can also be called merge points - points
322	in time where multiple outstandign events have been processed. And yet	488	in time where multiple outstanding events have been processed. And yet
323	another way to call them is transations - each condition variable can be	489	another way to call them is transactions - each condition variable can be
324	used to represent a transaction, which finishes at some point and delivers	490	used to represent a transaction, which finishes at some point and delivers
325	a result.	491	a result.
326		492
327	Condition variables are very useful to signal that something has finished,	493	Condition variables are very useful to signal that something has finished,
328	for example, if you write a module that does asynchronous http requests,	494	for example, if you write a module that does asynchronous http requests,
329	then a condition variable would be the ideal candidate to signal the	495	then a condition variable would be the ideal candidate to signal the
330	availability of results. The user can either act when the callback is	496	availability of results. The user can either act when the callback is
331	called or can synchronously C<< ->wait >> for the results.	497	called or can synchronously C<< ->recv >> for the results.
332		498
333	You can also use them to simulate traditional event loops - for example,	499	You can also use them to simulate traditional event loops - for example,
334	you can block your main program until an event occurs - for example, you	500	you can block your main program until an event occurs - for example, you
335	could C<< ->wait >> in your main program until the user clicks the Quit	501	could C<< ->recv >> in your main program until the user clicks the Quit
336	button of your app, which would C<< ->send >> the "quit" event.	502	button of your app, which would C<< ->send >> the "quit" event.
337		503
338	Note that condition variables recurse into the event loop - if you have	504	Note that condition variables recurse into the event loop - if you have
339	two pieces of code that call C<< ->wait >> in a round-robbin fashion, you	505	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
340	lose. Therefore, condition variables are good to export to your caller, but	506	lose. Therefore, condition variables are good to export to your caller, but
341	you should avoid making a blocking wait yourself, at least in callbacks,	507	you should avoid making a blocking wait yourself, at least in callbacks,
342	as this asks for trouble.	508	as this asks for trouble.
343		509
344	Condition variables are represented by hash refs in perl, and the keys	510	Condition variables are represented by hash refs in perl, and the keys
…		…
349		515
350	There are two "sides" to a condition variable - the "producer side" which	516	There are two "sides" to a condition variable - the "producer side" which
351	eventually calls C<< -> send >>, and the "consumer side", which waits	517	eventually calls C<< -> send >>, and the "consumer side", which waits
352	for the send to occur.	518	for the send to occur.
353		519
354	Example:	520	Example: wait for a timer.
355		521
356	# wait till the result is ready	522	# wait till the result is ready
357	my $result_ready = AnyEvent->condvar;	523	my $result_ready = AnyEvent->condvar;
358		524
359	# do something such as adding a timer	525	# do something such as adding a timer
…		…
365	cb => sub { $result_ready->send },	531	cb => sub { $result_ready->send },
366	);	532	);
367		533
368	# this "blocks" (while handling events) till the callback	534	# this "blocks" (while handling events) till the callback
369	# calls send	535	# calls send
370	$result_ready->wait;	536	$result_ready->recv;
		537
		538	Example: wait for a timer, but take advantage of the fact that
		539	condition variables are also code references.
		540
		541	my $done = AnyEvent->condvar;
		542	my $delay = AnyEvent->timer (after => 5, cb => $done);
		543	$done->recv;
		544
		545	Example: Imagine an API that returns a condvar and doesn't support
		546	callbacks. This is how you make a synchronous call, for example from
		547	the main program:
		548
		549	use AnyEvent::CouchDB;
		550
		551	...
		552
		553	my @info = $couchdb->info->recv;
		554
		555	And this is how you would just ste a callback to be called whenever the
		556	results are available:
		557
		558	$couchdb->info->cb (sub {
		559	my @info = $_[0]->recv;
		560	});
371		561
372	=head3 METHODS FOR PRODUCERS	562	=head3 METHODS FOR PRODUCERS
373		563
374	These methods should only be used by the producing side, i.e. the	564	These methods should only be used by the producing side, i.e. the
375	code/module that eventually sends the signal. Note that it is also	565	code/module that eventually sends the signal. Note that it is also
…		…
378		568
379	=over 4	569	=over 4
380		570
381	=item $cv->send (...)	571	=item $cv->send (...)
382		572
383	Flag the condition as ready - a running C<< ->wait >> and all further	573	Flag the condition as ready - a running C<< ->recv >> and all further
384	calls to C<wait> will (eventually) return after this method has been	574	calls to C<recv> will (eventually) return after this method has been
385	called. If nobody is waiting the send will be remembered.	575	called. If nobody is waiting the send will be remembered.
386		576
387	If a callback has been set on the condition variable, it is called	577	If a callback has been set on the condition variable, it is called
388	immediately from within send.	578	immediately from within send.
389		579
390	Any arguments passed to the C<send> call will be returned by all	580	Any arguments passed to the C<send> call will be returned by all
391	future C<< ->wait >> calls.	581	future C<< ->recv >> calls.
		582
		583	Condition variables are overloaded so one can call them directly
		584	(as a code reference). Calling them directly is the same as calling
		585	C<send>. Note, however, that many C-based event loops do not handle
		586	overloading, so as tempting as it may be, passing a condition variable
		587	instead of a callback does not work. Both the pure perl and EV loops
		588	support overloading, however, as well as all functions that use perl to
		589	invoke a callback (as in L<AnyEvent::Socket> and L<AnyEvent::DNS> for
		590	example).
392		591
393	=item $cv->croak ($error)	592	=item $cv->croak ($error)
394		593
395	Similar to send, but causes all call's wait C<< ->wait >> to invoke	594	Similar to send, but causes all call's to C<< ->recv >> to invoke
396	C<Carp::croak> with the given error message/object/scalar.	595	C<Carp::croak> with the given error message/object/scalar.
397		596
398	This can be used to signal any errors to the condition variable	597	This can be used to signal any errors to the condition variable
399	user/consumer.	598	user/consumer.
400		599
…		…
410	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end	609	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
411	>>, the (last) callback passed to C<begin> will be executed. That callback	610	>>, the (last) callback passed to C<begin> will be executed. That callback
412	is I<supposed> to call C<< ->send >>, but that is not required. If no	611	is I<supposed> to call C<< ->send >>, but that is not required. If no
413	callback was set, C<send> will be called without any arguments.	612	callback was set, C<send> will be called without any arguments.
414		613
415	Let's clarify this with the ping example:	614	You can think of C<< $cv->send >> giving you an OR condition (one call
		615	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		616	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		617
		618	Let's start with a simple example: you have two I/O watchers (for example,
		619	STDOUT and STDERR for a program), and you want to wait for both streams to
		620	close before activating a condvar:
		621
		622	my $cv = AnyEvent->condvar;
		623
		624	$cv->begin; # first watcher
		625	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		626	defined sysread $fh1, my $buf, 4096
		627	or $cv->end;
		628	});
		629
		630	$cv->begin; # second watcher
		631	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		632	defined sysread $fh2, my $buf, 4096
		633	or $cv->end;
		634	});
		635
		636	$cv->recv;
		637
		638	This works because for every event source (EOF on file handle), there is
		639	one call to C<begin>, so the condvar waits for all calls to C<end> before
		640	sending.
		641
		642	The ping example mentioned above is slightly more complicated, as the
		643	there are results to be passwd back, and the number of tasks that are
		644	begung can potentially be zero:
416		645
417	my $cv = AnyEvent->condvar;	646	my $cv = AnyEvent->condvar;
418		647
419	my %result;	648	my %result;
420	$cv->begin (sub { $cv->send (\%result) });	649	$cv->begin (sub { $cv->send (\%result) });
…		…
440	loop, which serves two important purposes: first, it sets the callback	669	loop, which serves two important purposes: first, it sets the callback
441	to be called once the counter reaches C<0>, and second, it ensures that	670	to be called once the counter reaches C<0>, and second, it ensures that
442	C<send> is called even when C<no> hosts are being pinged (the loop	671	C<send> is called even when C<no> hosts are being pinged (the loop
443	doesn't execute once).	672	doesn't execute once).
444		673
445	This is the general pattern when you "fan out" into multiple subrequests:	674	This is the general pattern when you "fan out" into multiple (but
446	use an outer C<begin>/C<end> pair to set the callback and ensure C<end>	675	potentially none) subrequests: use an outer C<begin>/C<end> pair to set
447	is called at least once, and then, for each subrequest you start, call	676	the callback and ensure C<end> is called at least once, and then, for each
448	C<begin> and for eahc subrequest you finish, call C<end>.	677	subrequest you start, call C<begin> and for each subrequest you finish,
		678	call C<end>.
449		679
450	=back	680	=back
451		681
452	=head3 METHODS FOR CONSUMERS	682	=head3 METHODS FOR CONSUMERS
453		683
454	These methods should only be used by the consuming side, i.e. the	684	These methods should only be used by the consuming side, i.e. the
455	code awaits the condition.	685	code awaits the condition.
456		686
457	=over 4	687	=over 4
458		688
459	=item $cv->wait	689	=item $cv->recv
460		690
461	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak	691	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
462	>> methods have been called on c<$cv>, while servicing other watchers	692	>> methods have been called on c<$cv>, while servicing other watchers
463	normally.	693	normally.
464		694
…		…
475	(programs might want to do that to stay interactive), so I<if you are	705	(programs might want to do that to stay interactive), so I<if you are
476	using this from a module, never require a blocking wait>, but let the	706	using this from a module, never require a blocking wait>, but let the
477	caller decide whether the call will block or not (for example, by coupling	707	caller decide whether the call will block or not (for example, by coupling
478	condition variables with some kind of request results and supporting	708	condition variables with some kind of request results and supporting
479	callbacks so the caller knows that getting the result will not block,	709	callbacks so the caller knows that getting the result will not block,
480	while still suppporting blocking waits if the caller so desires).	710	while still supporting blocking waits if the caller so desires).
481		711
482	Another reason I<never> to C<< ->wait >> in a module is that you cannot	712	Another reason I<never> to C<< ->recv >> in a module is that you cannot
483	sensibly have two C<< ->wait >>'s in parallel, as that would require	713	sensibly have two C<< ->recv >>'s in parallel, as that would require
484	multiple interpreters or coroutines/threads, none of which C<AnyEvent>	714	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
485	can supply.	715	can supply.
486		716
487	The L<Coro> module, however, I<can> and I<does> supply coroutines and, in	717	The L<Coro> module, however, I<can> and I<does> supply coroutines and, in
488	fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe	718	fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe
489	versions and also integrates coroutines into AnyEvent, making blocking	719	versions and also integrates coroutines into AnyEvent, making blocking
490	C<< ->wait >> calls perfectly safe as long as they are done from another	720	C<< ->recv >> calls perfectly safe as long as they are done from another
491	coroutine (one that doesn't run the event loop).	721	coroutine (one that doesn't run the event loop).
492		722
493	You can ensure that C<< -wait >> never blocks by setting a callback and	723	You can ensure that C<< -recv >> never blocks by setting a callback and
494	only calling C<< ->wait >> from within that callback (or at a later	724	only calling C<< ->recv >> from within that callback (or at a later
495	time). This will work even when the event loop does not support blocking	725	time). This will work even when the event loop does not support blocking
496	waits otherwise.	726	waits otherwise.
497		727
498	=item $bool = $cv->ready	728	=item $bool = $cv->ready
499		729
500	Returns true when the condition is "true", i.e. whether C<send> or	730	Returns true when the condition is "true", i.e. whether C<send> or
501	C<croak> have been called.	731	C<croak> have been called.
502		732
503	=item $cb = $cv->cb ([new callback])	733	=item $cb = $cv->cb ($cb->($cv))
504		734
505	This is a mutator function that returns the callback set and optionally	735	This is a mutator function that returns the callback set and optionally
506	replaces it before doing so.	736	replaces it before doing so.
507		737
508	The callback will be called when the condition becomes "true", i.e. when	738	The callback will be called when the condition becomes "true", i.e. when
509	C<send> or C<croak> are called. Calling C<wait> inside the callback	739	C<send> or C<croak> are called, with the only argument being the condition
510	or at any later time is guaranteed not to block.	740	variable itself. Calling C<recv> inside the callback or at any later time
		741	is guaranteed not to block.
		742
		743	=back
		744
		745	=head1 SUPPORTED EVENT LOOPS/BACKENDS
		746
		747	The available backend classes are (every class has its own manpage):
		748
		749	=over 4
		750
		751	=item Backends that are autoprobed when no other event loop can be found.
		752
		753	EV is the preferred backend when no other event loop seems to be in
		754	use. If EV is not installed, then AnyEvent will try Event, and, failing
		755	that, will fall back to its own pure-perl implementation, which is
		756	available everywhere as it comes with AnyEvent itself.
		757
		758	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		759	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		760	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
		761
		762	=item Backends that are transparently being picked up when they are used.
		763
		764	These will be used when they are currently loaded when the first watcher
		765	is created, in which case it is assumed that the application is using
		766	them. This means that AnyEvent will automatically pick the right backend
		767	when the main program loads an event module before anything starts to
		768	create watchers. Nothing special needs to be done by the main program.
		769
		770	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		771	AnyEvent::Impl::Tk based on Tk, very broken.
		772	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		773	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		774
		775	=item Backends with special needs.
		776
		777	Qt requires the Qt::Application to be instantiated first, but will
		778	otherwise be picked up automatically. As long as the main program
		779	instantiates the application before any AnyEvent watchers are created,
		780	everything should just work.
		781
		782	AnyEvent::Impl::Qt based on Qt.
		783
		784	Support for IO::Async can only be partial, as it is too broken and
		785	architecturally limited to even support the AnyEvent API. It also
		786	is the only event loop that needs the loop to be set explicitly, so
		787	it can only be used by a main program knowing about AnyEvent. See
		788	L<AnyEvent::Impl::Async> for the gory details.
		789
		790	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
		791
		792	=item Event loops that are indirectly supported via other backends.
		793
		794	Some event loops can be supported via other modules:
		795
		796	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		797
		798	B<WxWidgets> has no support for watching file handles. However, you can
		799	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		800	polls 20 times per second, which was considered to be too horrible to even
		801	consider for AnyEvent.
		802
		803	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		804	backend, so it can be supported through POE.
		805
		806	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		807	load L<POE> when detecting them, in the hope that POE will pick them up,
		808	in which case everything will be automatic.
511		809
512	=back	810	=back
513		811
514	=head1 GLOBAL VARIABLES AND FUNCTIONS	812	=head1 GLOBAL VARIABLES AND FUNCTIONS
515		813
…		…
521	contains the event model that is being used, which is the name of the	819	contains the event model that is being used, which is the name of the
522	Perl class implementing the model. This class is usually one of the	820	Perl class implementing the model. This class is usually one of the
523	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	821	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case
524	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	822	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).
525		823
526	The known classes so far are:
527
528	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
529	AnyEvent::Impl::Event based on Event, second best choice.
530	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
531	AnyEvent::Impl::Glib based on Glib, third-best choice.
532	AnyEvent::Impl::Tk based on Tk, very bad choice.
533	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
534	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
535	AnyEvent::Impl::POE based on POE, not generic enough for full support.
536
537	There is no support for WxWidgets, as WxWidgets has no support for
538	watching file handles. However, you can use WxWidgets through the
539	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
540	second, which was considered to be too horrible to even consider for
541	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
542	it's adaptor.
543
544	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
545	autodetecting them.
546
547	=item AnyEvent::detect	824	=item AnyEvent::detect
548		825
549	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	826	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
550	if necessary. You should only call this function right before you would	827	if necessary. You should only call this function right before you would
551	have created an AnyEvent watcher anyway, that is, as late as possible at	828	have created an AnyEvent watcher anyway, that is, as late as possible at
552	runtime.	829	runtime.
553		830
554	=item AnyEvent::on_detect { BLOCK }	831	=item $guard = AnyEvent::post_detect { BLOCK }
555		832
556	Arranges for the code block to be executed as soon as the event model is	833	Arranges for the code block to be executed as soon as the event model is
557	autodetected (or immediately if this has already happened).	834	autodetected (or immediately if this has already happened).
558		835
		836	If called in scalar or list context, then it creates and returns an object
		837	that automatically removes the callback again when it is destroyed. See
		838	L<Coro::BDB> for a case where this is useful.
		839
559	=item @AnyEvent::on_detect	840	=item @AnyEvent::post_detect
560		841
561	If there are any code references in this array (you can C<push> to it	842	If there are any code references in this array (you can C<push> to it
562	before or after loading AnyEvent), then they will called directly after	843	before or after loading AnyEvent), then they will called directly after
563	the event loop has been chosen.	844	the event loop has been chosen.
564		845
565	You should check C<$AnyEvent::MODEL> before adding to this array, though:	846	You should check C<$AnyEvent::MODEL> before adding to this array, though:
566	if it contains a true value then the event loop has already been detected,	847	if it contains a true value then the event loop has already been detected,
567	and the array will be ignored.	848	and the array will be ignored.
568		849
569	Best use C<AnyEvent::on_detect { BLOCK }> instead.	850	Best use C<AnyEvent::post_detect { BLOCK }> instead.
570		851
571	=back	852	=back
572		853
573	=head1 WHAT TO DO IN A MODULE	854	=head1 WHAT TO DO IN A MODULE
574		855
…		…
578	Be careful when you create watchers in the module body - AnyEvent will	859	Be careful when you create watchers in the module body - AnyEvent will
579	decide which event module to use as soon as the first method is called, so	860	decide which event module to use as soon as the first method is called, so
580	by calling AnyEvent in your module body you force the user of your module	861	by calling AnyEvent in your module body you force the user of your module
581	to load the event module first.	862	to load the event module first.
582		863
583	Never call C<< ->wait >> on a condition variable unless you I<know> that	864	Never call C<< ->recv >> on a condition variable unless you I<know> that
584	the C<< ->send >> method has been called on it already. This is	865	the C<< ->send >> method has been called on it already. This is
585	because it will stall the whole program, and the whole point of using	866	because it will stall the whole program, and the whole point of using
586	events is to stay interactive.	867	events is to stay interactive.
587		868
588	It is fine, however, to call C<< ->wait >> when the user of your module	869	It is fine, however, to call C<< ->recv >> when the user of your module
589	requests it (i.e. if you create a http request object ad have a method	870	requests it (i.e. if you create a http request object ad have a method
590	called C<results> that returns the results, it should call C<< ->wait >>	871	called C<results> that returns the results, it should call C<< ->recv >>
591	freely, as the user of your module knows what she is doing. always).	872	freely, as the user of your module knows what she is doing. always).
592		873
593	=head1 WHAT TO DO IN THE MAIN PROGRAM	874	=head1 WHAT TO DO IN THE MAIN PROGRAM
594		875
595	There will always be a single main program - the only place that should	876	There will always be a single main program - the only place that should
…		…
597		878
598	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	879	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
599	do anything special (it does not need to be event-based) and let AnyEvent	880	do anything special (it does not need to be event-based) and let AnyEvent
600	decide which implementation to chose if some module relies on it.	881	decide which implementation to chose if some module relies on it.
601		882
602	If the main program relies on a specific event model. For example, in	883	If the main program relies on a specific event model - for example, in
603	Gtk2 programs you have to rely on the Glib module. You should load the	884	Gtk2 programs you have to rely on the Glib module - you should load the
604	event module before loading AnyEvent or any module that uses it: generally	885	event module before loading AnyEvent or any module that uses it: generally
605	speaking, you should load it as early as possible. The reason is that	886	speaking, you should load it as early as possible. The reason is that
606	modules might create watchers when they are loaded, and AnyEvent will	887	modules might create watchers when they are loaded, and AnyEvent will
607	decide on the event model to use as soon as it creates watchers, and it	888	decide on the event model to use as soon as it creates watchers, and it
608	might chose the wrong one unless you load the correct one yourself.	889	might chose the wrong one unless you load the correct one yourself.
609		890
610	You can chose to use a rather inefficient pure-perl implementation by	891	You can chose to use a pure-perl implementation by loading the
611	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	892	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
612	behaviour everywhere, but letting AnyEvent chose is generally better.	893	everywhere, but letting AnyEvent chose the model is generally better.
		894
		895	=head2 MAINLOOP EMULATION
		896
		897	Sometimes (often for short test scripts, or even standalone programs who
		898	only want to use AnyEvent), you do not want to run a specific event loop.
		899
		900	In that case, you can use a condition variable like this:
		901
		902	AnyEvent->condvar->recv;
		903
		904	This has the effect of entering the event loop and looping forever.
		905
		906	Note that usually your program has some exit condition, in which case
		907	it is better to use the "traditional" approach of storing a condition
		908	variable somewhere, waiting for it, and sending it when the program should
		909	exit cleanly.
		910
613		911
614	=head1 OTHER MODULES	912	=head1 OTHER MODULES
615		913
616	The following is a non-exhaustive list of additional modules that use	914	The following is a non-exhaustive list of additional modules that use
617	AnyEvent and can therefore be mixed easily with other AnyEvent modules	915	AnyEvent as a client and can therefore be mixed easily with other AnyEvent
618	in the same program. Some of the modules come with AnyEvent, some are	916	modules and other event loops in the same program. Some of the modules
619	available via CPAN.	917	come with AnyEvent, most are available via CPAN.
620		918
621	=over 4	919	=over 4
622		920
623	=item L<AnyEvent::Util>	921	=item L<AnyEvent::Util>
624		922
625	Contains various utility functions that replace often-used but blocking	923	Contains various utility functions that replace often-used but blocking
626	functions such as C<inet_aton> by event-/callback-based versions.	924	functions such as C<inet_aton> by event-/callback-based versions.
627		925
		926	=item L<AnyEvent::Socket>
		927
		928	Provides various utility functions for (internet protocol) sockets,
		929	addresses and name resolution. Also functions to create non-blocking tcp
		930	connections or tcp servers, with IPv6 and SRV record support and more.
		931
628	=item L<AnyEvent::Handle>	932	=item L<AnyEvent::Handle>
629		933
630	Provide read and write buffers and manages watchers for reads and writes.	934	Provide read and write buffers, manages watchers for reads and writes,
		935	supports raw and formatted I/O, I/O queued and fully transparent and
		936	non-blocking SSL/TLS (via L<AnyEvent::TLS>.
631		937
632	=item L<AnyEvent::Socket>	938	=item L<AnyEvent::DNS>
633		939
634	Provides a means to do non-blocking connects, accepts etc.	940	Provides rich asynchronous DNS resolver capabilities.
		941
		942	=item L<AnyEvent::HTTP>
		943
		944	A simple-to-use HTTP library that is capable of making a lot of concurrent
		945	HTTP requests.
635		946
636	=item L<AnyEvent::HTTPD>	947	=item L<AnyEvent::HTTPD>
637		948
638	Provides a simple web application server framework.	949	Provides a simple web application server framework.
639		950
640	=item L<AnyEvent::DNS>
641
642	Provides asynchronous DNS resolver capabilities, beyond what
643	L<AnyEvent::Util> offers.
644
645	=item L<AnyEvent::FastPing>	951	=item L<AnyEvent::FastPing>
646		952
647	The fastest ping in the west.	953	The fastest ping in the west.
648		954
		955	=item L<AnyEvent::DBI>
		956
		957	Executes L<DBI> requests asynchronously in a proxy process.
		958
		959	=item L<AnyEvent::AIO>
		960
		961	Truly asynchronous I/O, should be in the toolbox of every event
		962	programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
		963	together.
		964
		965	=item L<AnyEvent::BDB>
		966
		967	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
		968	L<BDB> and AnyEvent together.
		969
		970	=item L<AnyEvent::GPSD>
		971
		972	A non-blocking interface to gpsd, a daemon delivering GPS information.
		973
649	=item L<Net::IRC3>	974	=item L<AnyEvent::IRC>
650		975
651	AnyEvent based IRC client module family.	976	AnyEvent based IRC client module family (replacing the older Net::IRC3).
652		977
653	=item L<Net::XMPP2>	978	=item L<AnyEvent::XMPP>
654		979
655	AnyEvent based XMPP (Jabber protocol) module family.	980	AnyEvent based XMPP (Jabber protocol) module family (replacing the older
		981	Net::XMPP2>.
		982
		983	=item L<AnyEvent::IGS>
		984
		985	A non-blocking interface to the Internet Go Server protocol (used by
		986	L<App::IGS>).
656		987
657	=item L<Net::FCP>	988	=item L<Net::FCP>
658		989
659	AnyEvent-based implementation of the Freenet Client Protocol, birthplace	990	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
660	of AnyEvent.	991	of AnyEvent.
…		…
665		996
666	=item L<Coro>	997	=item L<Coro>
667		998
668	Has special support for AnyEvent via L<Coro::AnyEvent>.	999	Has special support for AnyEvent via L<Coro::AnyEvent>.
669		1000
670	=item L<IO::Lambda>
671
672	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
673
674	=item L<IO::AIO>
675
676	Truly asynchronous I/O, should be in the toolbox of every event
677	programmer. Can be trivially made to use AnyEvent.
678
679	=item L<BDB>
680
681	Truly asynchronous Berkeley DB access. Can be trivially made to use
682	AnyEvent.
683
684	=back	1001	=back
685		1002
686	=cut	1003	=cut
687		1004
688	package AnyEvent;	1005	package AnyEvent;
689		1006
690	no warnings;	1007	no warnings;
691	use strict;	1008	use strict qw(vars subs);
692		1009
693	use Carp;	1010	use Carp;
694		1011
695	our $VERSION = '3.4';	1012	our $VERSION = 4.801;
696	our $MODEL;	1013	our $MODEL;
697		1014
698	our $AUTOLOAD;	1015	our $AUTOLOAD;
699	our @ISA;	1016	our @ISA;
700		1017
		1018	our @REGISTRY;
		1019
		1020	our $WIN32;
		1021
		1022	BEGIN {
		1023	eval "sub WIN32(){ " . (($^O =~ /mswin32/i)*1) ." }";
		1024	eval "sub TAINT(){ " . (${^TAINT}*1) . " }";
		1025
		1026	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1027	if ${^TAINT};
		1028	}
		1029
701	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;	1030	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
702		1031
703	our @REGISTRY;	1032	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		1033
		1034	{
		1035	my $idx;
		1036	$PROTOCOL{$_} = ++$idx
		1037	for reverse split /\s*,\s*/,
		1038	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		1039	}
704		1040
705	my @models = (	1041	my @models = (
706	[EV:: => AnyEvent::Impl::EV::],	1042	[EV:: => AnyEvent::Impl::EV::],
707	[Event:: => AnyEvent::Impl::Event::],	1043	[Event:: => AnyEvent::Impl::Event::],
		1044	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
		1045	# everything below here will not be autoprobed
		1046	# as the pureperl backend should work everywhere
		1047	# and is usually faster
		1048	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers
		1049	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
708	[Tk:: => AnyEvent::Impl::Tk::],	1050	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		1051	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
		1052	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
709	[Wx:: => AnyEvent::Impl::POE::],	1053	[Wx:: => AnyEvent::Impl::POE::],
710	[Prima:: => AnyEvent::Impl::POE::],	1054	[Prima:: => AnyEvent::Impl::POE::],
711	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1055	# IO::Async is just too broken - we would need workarounds for its
712	# everything below here will not be autoprobed as the pureperl backend should work everywhere	1056	# byzantine signal and broken child handling, among others.
713	[Glib:: => AnyEvent::Impl::Glib::],	1057	# IO::Async is rather hard to detect, as it doesn't have any
714	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy	1058	# obvious default class.
715	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program	1059	# [IO::Async:: => AnyEvent::Impl::IOAsync::], # requires special main program
716	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza	1060	# [IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1061	# [IO::Async::Notifier:: => AnyEvent::Impl::IOAsync::], # requires special main program
717	);	1062	);
718		1063
719	our %method = map +($_ => 1), qw(io timer signal child condvar one_event DESTROY);	1064	our %method = map +($_ => 1),
		1065	qw(io timer time now now_update signal child idle condvar one_event DESTROY);
720		1066
721	our @on_detect;	1067	our @post_detect;
722		1068
723	sub on_detect(&) {	1069	sub post_detect(&) {
		1070	my ($cb) = @_;
		1071
724	if ($MODEL) {	1072	if ($MODEL) {
725	$_[0]->();	1073	$cb->();
		1074
		1075	1
726	} else {	1076	} else {
727	push @on_detect, $_[0];	1077	push @post_detect, $cb;
		1078
		1079	defined wantarray
		1080	? bless \$cb, "AnyEvent::Util::postdetect"
		1081	: ()
728	}	1082	}
		1083	}
		1084
		1085	sub AnyEvent::Util::postdetect::DESTROY {
		1086	@post_detect = grep $_ != ${$_[0]}, @post_detect;
729	}	1087	}
730		1088
731	sub detect() {	1089	sub detect() {
732	unless ($MODEL) {	1090	unless ($MODEL) {
733	no strict 'refs';	1091	no strict 'refs';
		1092	local $SIG{__DIE__};
734		1093
735	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	1094	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
736	my $model = "AnyEvent::Impl::$1";	1095	my $model = "AnyEvent::Impl::$1";
737	if (eval "require $model") {	1096	if (eval "require $model") {
738	$MODEL = $model;	1097	$MODEL = $model;
…		…
768	last;	1127	last;
769	}	1128	}
770	}	1129	}
771		1130
772	$MODEL	1131	$MODEL
773	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.";	1132	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.\n";
774	}	1133	}
775	}	1134	}
776		1135
		1136	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		1137
777	unshift @ISA, $MODEL;	1138	unshift @ISA, $MODEL;
778	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
779		1139
		1140	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
		1141
780	(shift @on_detect)->() while @on_detect;	1142	(shift @post_detect)->() while @post_detect;
781	}	1143	}
782		1144
783	$MODEL	1145	$MODEL
784	}	1146	}
785		1147
…		…
793		1155
794	my $class = shift;	1156	my $class = shift;
795	$class->$func (@_);	1157	$class->$func (@_);
796	}	1158	}
797		1159
		1160	# utility function to dup a filehandle. this is used by many backends
		1161	# to support binding more than one watcher per filehandle (they usually
		1162	# allow only one watcher per fd, so we dup it to get a different one).
		1163	sub _dupfh($$;$$) {
		1164	my ($poll, $fh, $r, $w) = @_;
		1165
		1166	# cygwin requires the fh mode to be matching, unix doesn't
		1167	my ($rw, $mode) = $poll eq "r" ? ($r, "<") : ($w, ">");
		1168
		1169	open my $fh2, "$mode&", $fh
		1170	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1171
		1172	# we assume CLOEXEC is already set by perl in all important cases
		1173
		1174	($fh2, $rw)
		1175	}
		1176
798	package AnyEvent::Base;	1177	package AnyEvent::Base;
799		1178
		1179	# default implementations for many methods
		1180
		1181	BEGIN {
		1182	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1183	*_time = \&Time::HiRes::time;
		1184	# if (eval "use POSIX (); (POSIX::times())...
		1185	} else {
		1186	*_time = sub { time }; # epic fail
		1187	}
		1188	}
		1189
		1190	sub time { _time }
		1191	sub now { _time }
		1192	sub now_update { }
		1193
800	# default implementation for ->condvar, ->wait, ->broadcast	1194	# default implementation for ->condvar
801		1195
802	sub condvar {	1196	sub condvar {
803	bless \my $flag, "AnyEvent::Base::CondVar"	1197	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
804	}
805
806	sub AnyEvent::Base::CondVar::broadcast {
807	${$_[0]}++;
808	}
809
810	sub AnyEvent::Base::CondVar::wait {
811	AnyEvent->one_event while !${$_[0]};
812	}	1198	}
813		1199
814	# default implementation for ->signal	1200	# default implementation for ->signal
815		1201
816	our %SIG_CB;	1202	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1203
		1204	sub _signal_exec {
		1205	sysread $SIGPIPE_R, my $dummy, 4;
		1206
		1207	while (%SIG_EV) {
		1208	for (keys %SIG_EV) {
		1209	delete $SIG_EV{$_};
		1210	$_->() for values %{ $SIG_CB{$_} || {} };
		1211	}
		1212	}
		1213	}
817		1214
818	sub signal {	1215	sub signal {
819	my (undef, %arg) = @_;	1216	my (undef, %arg) = @_;
820		1217
		1218	unless ($SIGPIPE_R) {
		1219	require Fcntl;
		1220
		1221	if (AnyEvent::WIN32) {
		1222	require AnyEvent::Util;
		1223
		1224	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1225	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R) if $SIGPIPE_R;
		1226	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W) if $SIGPIPE_W; # just in case
		1227	} else {
		1228	pipe $SIGPIPE_R, $SIGPIPE_W;
		1229	fcntl $SIGPIPE_R, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_R;
		1230	fcntl $SIGPIPE_W, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_W; # just in case
		1231
		1232	# not strictly required, as $^F is normally 2, but let's make sure...
		1233	fcntl $SIGPIPE_R, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1234	fcntl $SIGPIPE_W, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1235	}
		1236
		1237	$SIGPIPE_R
		1238	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1239
		1240	$SIG_IO = AnyEvent->io (fh => $SIGPIPE_R, poll => "r", cb => \&_signal_exec);
		1241	}
		1242
821	my $signal = uc $arg{signal}	1243	my $signal = uc $arg{signal}
822	or Carp::croak "required option 'signal' is missing";	1244	or Carp::croak "required option 'signal' is missing";
823		1245
824	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1246	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
825	$SIG{$signal} ||= sub {	1247	$SIG{$signal} ||= sub {
826	$_->() for values %{ $SIG_CB{$signal} || {} };	1248	local $!;
		1249	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1250	undef $SIG_EV{$signal};
827	};	1251	};
828		1252
829	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1253	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
830	}	1254	}
831		1255
832	sub AnyEvent::Base::Signal::DESTROY {	1256	sub AnyEvent::Base::signal::DESTROY {
833	my ($signal, $cb) = @{$_[0]};	1257	my ($signal, $cb) = @{$_[0]};
834		1258
835	delete $SIG_CB{$signal}{$cb};	1259	delete $SIG_CB{$signal}{$cb};
836		1260
		1261	# delete doesn't work with older perls - they then
		1262	# print weird messages, or just unconditionally exit
		1263	# instead of getting the default action.
837	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };	1264	undef $SIG{$signal} unless keys %{ $SIG_CB{$signal} };
838	}	1265	}
839		1266
840	# default implementation for ->child	1267	# default implementation for ->child
841		1268
842	our %PID_CB;	1269	our %PID_CB;
843	our $CHLD_W;	1270	our $CHLD_W;
844	our $CHLD_DELAY_W;	1271	our $CHLD_DELAY_W;
845	our $PID_IDLE;
846	our $WNOHANG;	1272	our $WNOHANG;
847		1273
848	sub _child_wait {	1274	sub _sigchld {
849	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1275	while (0 < (my $pid = waitpid -1, $WNOHANG)) {
850	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1276	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),
851	(values %{ $PID_CB{0} || {} });	1277	(values %{ $PID_CB{0} || {} });
852	}	1278	}
853
854	undef $PID_IDLE;
855	}
856
857	sub _sigchld {
858	# make sure we deliver these changes "synchronous" with the event loop.
859	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {
860	undef $CHLD_DELAY_W;
861	&_child_wait;
862	});
863	}	1279	}
864		1280
865	sub child {	1281	sub child {
866	my (undef, %arg) = @_;	1282	my (undef, %arg) = @_;
867		1283
868	defined (my $pid = $arg{pid} + 0)	1284	defined (my $pid = $arg{pid} + 0)
869	or Carp::croak "required option 'pid' is missing";	1285	or Carp::croak "required option 'pid' is missing";
870		1286
871	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1287	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
872		1288
873	unless ($WNOHANG) {
874	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;	1289	$WNOHANG ||= eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
875	}
876		1290
877	unless ($CHLD_W) {	1291	unless ($CHLD_W) {
878	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1292	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
879	# child could be a zombie already, so make at least one round	1293	# child could be a zombie already, so make at least one round
880	&_sigchld;	1294	&_sigchld;
881	}	1295	}
882		1296
883	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	1297	bless [$pid, $arg{cb}], "AnyEvent::Base::child"
884	}	1298	}
885		1299
886	sub AnyEvent::Base::Child::DESTROY {	1300	sub AnyEvent::Base::child::DESTROY {
887	my ($pid, $cb) = @{$_[0]};	1301	my ($pid, $cb) = @{$_[0]};
888		1302
889	delete $PID_CB{$pid}{$cb};	1303	delete $PID_CB{$pid}{$cb};
890	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1304	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
891		1305
892	undef $CHLD_W unless keys %PID_CB;	1306	undef $CHLD_W unless keys %PID_CB;
893	}	1307	}
		1308
		1309	# idle emulation is done by simply using a timer, regardless
		1310	# of whether the process is idle or not, and not letting
		1311	# the callback use more than 50% of the time.
		1312	sub idle {
		1313	my (undef, %arg) = @_;
		1314
		1315	my ($cb, $w, $rcb) = $arg{cb};
		1316
		1317	$rcb = sub {
		1318	if ($cb) {
		1319	$w = _time;
		1320	&$cb;
		1321	$w = _time - $w;
		1322
		1323	# never use more then 50% of the time for the idle watcher,
		1324	# within some limits
		1325	$w = 0.0001 if $w < 0.0001;
		1326	$w = 5 if $w > 5;
		1327
		1328	$w = AnyEvent->timer (after => $w, cb => $rcb);
		1329	} else {
		1330	# clean up...
		1331	undef $w;
		1332	undef $rcb;
		1333	}
		1334	};
		1335
		1336	$w = AnyEvent->timer (after => 0.05, cb => $rcb);
		1337
		1338	bless \\$cb, "AnyEvent::Base::idle"
		1339	}
		1340
		1341	sub AnyEvent::Base::idle::DESTROY {
		1342	undef $${$_[0]};
		1343	}
		1344
		1345	package AnyEvent::CondVar;
		1346
		1347	our @ISA = AnyEvent::CondVar::Base::;
		1348
		1349	package AnyEvent::CondVar::Base;
		1350
		1351	use overload
		1352	'&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1353	fallback => 1;
		1354
		1355	sub _send {
		1356	# nop
		1357	}
		1358
		1359	sub send {
		1360	my $cv = shift;
		1361	$cv->{_ae_sent} = [@_];
		1362	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1363	$cv->_send;
		1364	}
		1365
		1366	sub croak {
		1367	$_[0]{_ae_croak} = $_[1];
		1368	$_[0]->send;
		1369	}
		1370
		1371	sub ready {
		1372	$_[0]{_ae_sent}
		1373	}
		1374
		1375	sub _wait {
		1376	AnyEvent->one_event while !$_[0]{_ae_sent};
		1377	}
		1378
		1379	sub recv {
		1380	$_[0]->_wait;
		1381
		1382	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
		1383	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
		1384	}
		1385
		1386	sub cb {
		1387	$_[0]{_ae_cb} = $_[1] if @_ > 1;
		1388	$_[0]{_ae_cb}
		1389	}
		1390
		1391	sub begin {
		1392	++$_[0]{_ae_counter};
		1393	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
		1394	}
		1395
		1396	sub end {
		1397	return if --$_[0]{_ae_counter};
		1398	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		1399	}
		1400
		1401	# undocumented/compatibility with pre-3.4
		1402	*broadcast = \&send;
		1403	*wait = \&_wait;
		1404
		1405	=head1 ERROR AND EXCEPTION HANDLING
		1406
		1407	In general, AnyEvent does not do any error handling - it relies on the
		1408	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1409	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1410	checking of all AnyEvent methods, however, which is highly useful during
		1411	development.
		1412
		1413	As for exception handling (i.e. runtime errors and exceptions thrown while
		1414	executing a callback), this is not only highly event-loop specific, but
		1415	also not in any way wrapped by this module, as this is the job of the main
		1416	program.
		1417
		1418	The pure perl event loop simply re-throws the exception (usually
		1419	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1420	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1421	so on.
		1422
		1423	=head1 ENVIRONMENT VARIABLES
		1424
		1425	The following environment variables are used by this module or its
		1426	submodules.
		1427
		1428	Note that AnyEvent will remove I<all> environment variables starting with
		1429	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		1430	enabled.
		1431
		1432	=over 4
		1433
		1434	=item C<PERL_ANYEVENT_VERBOSE>
		1435
		1436	By default, AnyEvent will be completely silent except in fatal
		1437	conditions. You can set this environment variable to make AnyEvent more
		1438	talkative.
		1439
		1440	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1441	conditions, such as not being able to load the event model specified by
		1442	C<PERL_ANYEVENT_MODEL>.
		1443
		1444	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1445	model it chooses.
		1446
		1447	=item C<PERL_ANYEVENT_STRICT>
		1448
		1449	AnyEvent does not do much argument checking by default, as thorough
		1450	argument checking is very costly. Setting this variable to a true value
		1451	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1452	check the arguments passed to most method calls. If it finds any problems,
		1453	it will croak.
		1454
		1455	In other words, enables "strict" mode.
		1456
		1457	Unlike C<use strict>, it is definitely recommended to keep it off in
		1458	production. Keeping C<PERL_ANYEVENT_STRICT=1> in your environment while
		1459	developing programs can be very useful, however.
		1460
		1461	=item C<PERL_ANYEVENT_MODEL>
		1462
		1463	This can be used to specify the event model to be used by AnyEvent, before
		1464	auto detection and -probing kicks in. It must be a string consisting
		1465	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1466	and the resulting module name is loaded and if the load was successful,
		1467	used as event model. If it fails to load AnyEvent will proceed with
		1468	auto detection and -probing.
		1469
		1470	This functionality might change in future versions.
		1471
		1472	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1473	could start your program like this:
		1474
		1475	PERL_ANYEVENT_MODEL=Perl perl ...
		1476
		1477	=item C<PERL_ANYEVENT_PROTOCOLS>
		1478
		1479	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1480	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1481	of auto probing).
		1482
		1483	Must be set to a comma-separated list of protocols or address families,
		1484	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1485	used, and preference will be given to protocols mentioned earlier in the
		1486	list.
		1487
		1488	This variable can effectively be used for denial-of-service attacks
		1489	against local programs (e.g. when setuid), although the impact is likely
		1490	small, as the program has to handle conenction and other failures anyways.
		1491
		1492	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1493	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1494	- only support IPv4, never try to resolve or contact IPv6
		1495	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1496	IPv6, but prefer IPv6 over IPv4.
		1497
		1498	=item C<PERL_ANYEVENT_EDNS0>
		1499
		1500	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1501	for DNS. This extension is generally useful to reduce DNS traffic, but
		1502	some (broken) firewalls drop such DNS packets, which is why it is off by
		1503	default.
		1504
		1505	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1506	EDNS0 in its DNS requests.
		1507
		1508	=item C<PERL_ANYEVENT_MAX_FORKS>
		1509
		1510	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1511	will create in parallel.
		1512
		1513	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		1514
		1515	The default value for the C<max_outstanding> parameter for the default DNS
		1516	resolver - this is the maximum number of parallel DNS requests that are
		1517	sent to the DNS server.
		1518
		1519	=item C<PERL_ANYEVENT_RESOLV_CONF>
		1520
		1521	The file to use instead of F</etc/resolv.conf> (or OS-specific
		1522	configuration) in the default resolver. When set to the empty string, no
		1523	default config will be used.
		1524
		1525	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		1526
		1527	When neither C<ca_file> nor C<ca_path> was specified during
		1528	L<AnyEvent::TLS> context creation, and either of these environment
		1529	variables exist, they will be used to specify CA certificate locations
		1530	instead of a system-dependent default.
		1531
		1532	=back
894		1533
895	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1534	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
896		1535
897	This is an advanced topic that you do not normally need to use AnyEvent in	1536	This is an advanced topic that you do not normally need to use AnyEvent in
898	a module. This section is only of use to event loop authors who want to	1537	a module. This section is only of use to event loop authors who want to
…		…
932		1571
933	I<rxvt-unicode> also cheats a bit by not providing blocking access to	1572	I<rxvt-unicode> also cheats a bit by not providing blocking access to
934	condition variables: code blocking while waiting for a condition will	1573	condition variables: code blocking while waiting for a condition will
935	C<die>. This still works with most modules/usages, and blocking calls must	1574	C<die>. This still works with most modules/usages, and blocking calls must
936	not be done in an interactive application, so it makes sense.	1575	not be done in an interactive application, so it makes sense.
937
938	=head1 ENVIRONMENT VARIABLES
939
940	The following environment variables are used by this module:
941
942	=over 4
943
944	=item C<PERL_ANYEVENT_VERBOSE>
945
946	By default, AnyEvent will be completely silent except in fatal
947	conditions. You can set this environment variable to make AnyEvent more
948	talkative.
949
950	When set to C<1> or higher, causes AnyEvent to warn about unexpected
951	conditions, such as not being able to load the event model specified by
952	C<PERL_ANYEVENT_MODEL>.
953
954	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
955	model it chooses.
956
957	=item C<PERL_ANYEVENT_MODEL>
958
959	This can be used to specify the event model to be used by AnyEvent, before
960	autodetection and -probing kicks in. It must be a string consisting
961	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
962	and the resulting module name is loaded and if the load was successful,
963	used as event model. If it fails to load AnyEvent will proceed with
964	autodetection and -probing.
965
966	This functionality might change in future versions.
967
968	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
969	could start your program like this:
970
971	PERL_ANYEVENT_MODEL=Perl perl ...
972
973	=back
974		1576
975	=head1 EXAMPLE PROGRAM	1577	=head1 EXAMPLE PROGRAM
976		1578
977	The following program uses an I/O watcher to read data from STDIN, a timer	1579	The following program uses an I/O watcher to read data from STDIN, a timer
978	to display a message once per second, and a condition variable to quit the	1580	to display a message once per second, and a condition variable to quit the
…		…
987	poll => 'r',	1589	poll => 'r',
988	cb => sub {	1590	cb => sub {
989	warn "io event <$_[0]>\n"; # will always output <r>	1591	warn "io event <$_[0]>\n"; # will always output <r>
990	chomp (my $input = <STDIN>); # read a line	1592	chomp (my $input = <STDIN>); # read a line
991	warn "read: $input\n"; # output what has been read	1593	warn "read: $input\n"; # output what has been read
992	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	1594	$cv->send if $input =~ /^q/i; # quit program if /^q/i
993	},	1595	},
994	);	1596	);
995		1597
996	my $time_watcher; # can only be used once	1598	my $time_watcher; # can only be used once
997		1599
…		…
1002	});	1604	});
1003	}	1605	}
1004		1606
1005	new_timer; # create first timer	1607	new_timer; # create first timer
1006		1608
1007	$cv->wait; # wait until user enters /^q/i	1609	$cv->recv; # wait until user enters /^q/i
1008		1610
1009	=head1 REAL-WORLD EXAMPLE	1611	=head1 REAL-WORLD EXAMPLE
1010		1612
1011	Consider the L<Net::FCP> module. It features (among others) the following	1613	Consider the L<Net::FCP> module. It features (among others) the following
1012	API calls, which are to freenet what HTTP GET requests are to http:	1614	API calls, which are to freenet what HTTP GET requests are to http:
…		…
1062	syswrite $txn->{fh}, $txn->{request}	1664	syswrite $txn->{fh}, $txn->{request}
1063	or die "connection or write error";	1665	or die "connection or write error";
1064	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	1666	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
1065		1667
1066	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	1668	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
1067	result and signals any possible waiters that the request ahs finished:	1669	result and signals any possible waiters that the request has finished:
1068		1670
1069	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	1671	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
1070		1672
1071	if (end-of-file or data complete) {	1673	if (end-of-file or data complete) {
1072	$txn->{result} = $txn->{buf};	1674	$txn->{result} = $txn->{buf};
1073	$txn->{finished}->broadcast;	1675	$txn->{finished}->send;
1074	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	1676	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
1075	}	1677	}
1076		1678
1077	The C<result> method, finally, just waits for the finished signal (if the	1679	The C<result> method, finally, just waits for the finished signal (if the
1078	request was already finished, it doesn't wait, of course, and returns the	1680	request was already finished, it doesn't wait, of course, and returns the
1079	data:	1681	data:
1080		1682
1081	$txn->{finished}->wait;	1683	$txn->{finished}->recv;
1082	return $txn->{result};	1684	return $txn->{result};
1083		1685
1084	The actual code goes further and collects all errors (C<die>s, exceptions)	1686	The actual code goes further and collects all errors (C<die>s, exceptions)
1085	that occured during request processing. The C<result> method detects	1687	that occurred during request processing. The C<result> method detects
1086	whether an exception as thrown (it is stored inside the $txn object)	1688	whether an exception as thrown (it is stored inside the $txn object)
1087	and just throws the exception, which means connection errors and other	1689	and just throws the exception, which means connection errors and other
1088	problems get reported tot he code that tries to use the result, not in a	1690	problems get reported tot he code that tries to use the result, not in a
1089	random callback.	1691	random callback.
1090		1692
…		…
1121		1723
1122	my $quit = AnyEvent->condvar;	1724	my $quit = AnyEvent->condvar;
1123		1725
1124	$fcp->txn_client_get ($url)->cb (sub {	1726	$fcp->txn_client_get ($url)->cb (sub {
1125	...	1727	...
1126	$quit->broadcast;	1728	$quit->send;
1127	});	1729	});
1128		1730
1129	$quit->wait;	1731	$quit->recv;
1130		1732
1131		1733
1132	=head1 BENCHMARKS	1734	=head1 BENCHMARKS
1133		1735
1134	To give you an idea of the performance and overheads that AnyEvent adds	1736	To give you an idea of the performance and overheads that AnyEvent adds
…		…
1136	of various event loops I prepared some benchmarks.	1738	of various event loops I prepared some benchmarks.
1137		1739
1138	=head2 BENCHMARKING ANYEVENT OVERHEAD	1740	=head2 BENCHMARKING ANYEVENT OVERHEAD
1139		1741
1140	Here is a benchmark of various supported event models used natively and	1742	Here is a benchmark of various supported event models used natively and
1141	through anyevent. The benchmark creates a lot of timers (with a zero	1743	through AnyEvent. The benchmark creates a lot of timers (with a zero
1142	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,	1744	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
1143	which it is), lets them fire exactly once and destroys them again.	1745	which it is), lets them fire exactly once and destroys them again.
1144		1746
1145	Source code for this benchmark is found as F<eg/bench> in the AnyEvent	1747	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
1146	distribution.	1748	distribution.
…		…
1163	all watchers, to avoid adding memory overhead. That means closure creation	1765	all watchers, to avoid adding memory overhead. That means closure creation
1164	and memory usage is not included in the figures.	1766	and memory usage is not included in the figures.
1165		1767
1166	I<invoke> is the time, in microseconds, used to invoke a simple	1768	I<invoke> is the time, in microseconds, used to invoke a simple
1167	callback. The callback simply counts down a Perl variable and after it was	1769	callback. The callback simply counts down a Perl variable and after it was
1168	invoked "watcher" times, it would C<< ->broadcast >> a condvar once to	1770	invoked "watcher" times, it would C<< ->send >> a condvar once to
1169	signal the end of this phase.	1771	signal the end of this phase.
1170		1772
1171	I<destroy> is the time, in microseconds, that it takes to destroy a single	1773	I<destroy> is the time, in microseconds, that it takes to destroy a single
1172	watcher.	1774	watcher.
1173		1775
1174	=head3 Results	1776	=head3 Results
1175		1777
1176	name watchers bytes create invoke destroy comment	1778	name watchers bytes create invoke destroy comment
1177	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	1779	EV/EV 400000 224 0.47 0.35 0.27 EV native interface
1178	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	1780	EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers
1179	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	1781	CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal
1180	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	1782	Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation
1181	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	1783	Event/Event 16000 517 32.20 31.80 0.81 Event native interface
1182	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers	1784	Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers
		1785	IOAsync/Any 16000 989 38.10 32.77 11.13 via IO::Async::Loop::IO_Poll
		1786	IOAsync/Any 16000 990 37.59 29.50 10.61 via IO::Async::Loop::Epoll
1183	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	1787	Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour
1184	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	1788	Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers
1185	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	1789	POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event
1186	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	1790	POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select
1187		1791
1188	=head3 Discussion	1792	=head3 Discussion
1189		1793
1190	The benchmark does I<not> measure scalability of the event loop very	1794	The benchmark does I<not> measure scalability of the event loop very
1191	well. For example, a select-based event loop (such as the pure perl one)	1795	well. For example, a select-based event loop (such as the pure perl one)
…		…
1216	performance becomes really bad with lots of file descriptors (and few of	1820	performance becomes really bad with lots of file descriptors (and few of
1217	them active), of course, but this was not subject of this benchmark.	1821	them active), of course, but this was not subject of this benchmark.
1218		1822
1219	The C<Event> module has a relatively high setup and callback invocation	1823	The C<Event> module has a relatively high setup and callback invocation
1220	cost, but overall scores in on the third place.	1824	cost, but overall scores in on the third place.
		1825
		1826	C<IO::Async> performs admirably well, about on par with C<Event>, even
		1827	when using its pure perl backend.
1221		1828
1222	C<Glib>'s memory usage is quite a bit higher, but it features a	1829	C<Glib>'s memory usage is quite a bit higher, but it features a
1223	faster callback invocation and overall ends up in the same class as	1830	faster callback invocation and overall ends up in the same class as
1224	C<Event>. However, Glib scales extremely badly, doubling the number of	1831	C<Event>. However, Glib scales extremely badly, doubling the number of
1225	watchers increases the processing time by more than a factor of four,	1832	watchers increases the processing time by more than a factor of four,
…		…
1269		1876
1270	=back	1877	=back
1271		1878
1272	=head2 BENCHMARKING THE LARGE SERVER CASE	1879	=head2 BENCHMARKING THE LARGE SERVER CASE
1273		1880
1274	This benchmark atcually benchmarks the event loop itself. It works by	1881	This benchmark actually benchmarks the event loop itself. It works by
1275	creating a number of "servers": each server consists of a socketpair, a	1882	creating a number of "servers": each server consists of a socket pair, a
1276	timeout watcher that gets reset on activity (but never fires), and an I/O	1883	timeout watcher that gets reset on activity (but never fires), and an I/O
1277	watcher waiting for input on one side of the socket. Each time the socket	1884	watcher waiting for input on one side of the socket. Each time the socket
1278	watcher reads a byte it will write that byte to a random other "server".	1885	watcher reads a byte it will write that byte to a random other "server".
1279		1886
1280	The effect is that there will be a lot of I/O watchers, only part of which	1887	The effect is that there will be a lot of I/O watchers, only part of which
1281	are active at any one point (so there is a constant number of active	1888	are active at any one point (so there is a constant number of active
1282	fds for each loop iterstaion, but which fds these are is random). The	1889	fds for each loop iteration, but which fds these are is random). The
1283	timeout is reset each time something is read because that reflects how	1890	timeout is reset each time something is read because that reflects how
1284	most timeouts work (and puts extra pressure on the event loops).	1891	most timeouts work (and puts extra pressure on the event loops).
1285		1892
1286	In this benchmark, we use 10000 socketpairs (20000 sockets), of which 100	1893	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
1287	(1%) are active. This mirrors the activity of large servers with many	1894	(1%) are active. This mirrors the activity of large servers with many
1288	connections, most of which are idle at any one point in time.	1895	connections, most of which are idle at any one point in time.
1289		1896
1290	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent	1897	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
1291	distribution.	1898	distribution.
…		…
1293	=head3 Explanation of the columns	1900	=head3 Explanation of the columns
1294		1901
1295	I<sockets> is the number of sockets, and twice the number of "servers" (as	1902	I<sockets> is the number of sockets, and twice the number of "servers" (as
1296	each server has a read and write socket end).	1903	each server has a read and write socket end).
1297		1904
1298	I<create> is the time it takes to create a socketpair (which is	1905	I<create> is the time it takes to create a socket pair (which is
1299	nontrivial) and two watchers: an I/O watcher and a timeout watcher.	1906	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
1300		1907
1301	I<request>, the most important value, is the time it takes to handle a	1908	I<request>, the most important value, is the time it takes to handle a
1302	single "request", that is, reading the token from the pipe and forwarding	1909	single "request", that is, reading the token from the pipe and forwarding
1303	it to another server. This includes deleting the old timeout and creating	1910	it to another server. This includes deleting the old timeout and creating
1304	a new one that moves the timeout into the future.	1911	a new one that moves the timeout into the future.
1305		1912
1306	=head3 Results	1913	=head3 Results
1307		1914
1308	name sockets create request	1915	name sockets create request
1309	EV 20000 69.01 11.16	1916	EV 20000 69.01 11.16
1310	Perl 20000 73.32 35.87	1917	Perl 20000 73.32 35.87
		1918	IOAsync 20000 157.00 98.14 epoll
		1919	IOAsync 20000 159.31 616.06 poll
1311	Event 20000 212.62 257.32	1920	Event 20000 212.62 257.32
1312	Glib 20000 651.16 1896.30	1921	Glib 20000 651.16 1896.30
1313	POE 20000 349.67 12317.24 uses POE::Loop::Event	1922	POE 20000 349.67 12317.24 uses POE::Loop::Event
1314		1923
1315	=head3 Discussion	1924	=head3 Discussion
1316		1925
1317	This benchmark I<does> measure scalability and overall performance of the	1926	This benchmark I<does> measure scalability and overall performance of the
1318	particular event loop.	1927	particular event loop.
…		…
1320	EV is again fastest. Since it is using epoll on my system, the setup time	1929	EV is again fastest. Since it is using epoll on my system, the setup time
1321	is relatively high, though.	1930	is relatively high, though.
1322		1931
1323	Perl surprisingly comes second. It is much faster than the C-based event	1932	Perl surprisingly comes second. It is much faster than the C-based event
1324	loops Event and Glib.	1933	loops Event and Glib.
		1934
		1935	IO::Async performs very well when using its epoll backend, and still quite
		1936	good compared to Glib when using its pure perl backend.
1325		1937
1326	Event suffers from high setup time as well (look at its code and you will	1938	Event suffers from high setup time as well (look at its code and you will
1327	understand why). Callback invocation also has a high overhead compared to	1939	understand why). Callback invocation also has a high overhead compared to
1328	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event	1940	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
1329	uses select or poll in basically all documented configurations.	1941	uses select or poll in basically all documented configurations.
…		…
1376	speed most when you have lots of watchers, not when you only have a few of	1988	speed most when you have lots of watchers, not when you only have a few of
1377	them).	1989	them).
1378		1990
1379	EV is again fastest.	1991	EV is again fastest.
1380		1992
1381	Perl again comes second. It is noticably faster than the C-based event	1993	Perl again comes second. It is noticeably faster than the C-based event
1382	loops Event and Glib, although the difference is too small to really	1994	loops Event and Glib, although the difference is too small to really
1383	matter.	1995	matter.
1384		1996
1385	POE also performs much better in this case, but is is still far behind the	1997	POE also performs much better in this case, but is is still far behind the
1386	others.	1998	others.
…		…
1392	=item * C-based event loops perform very well with small number of	2004	=item * C-based event loops perform very well with small number of
1393	watchers, as the management overhead dominates.	2005	watchers, as the management overhead dominates.
1394		2006
1395	=back	2007	=back
1396		2008
		2009	=head2 THE IO::Lambda BENCHMARK
		2010
		2011	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2012	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2013	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2014	shouldn't come as a surprise to anybody). As such, the benchmark is
		2015	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2016	very optimal. But how would AnyEvent compare when used without the extra
		2017	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2018
		2019	The benchmark itself creates an echo-server, and then, for 500 times,
		2020	connects to the echo server, sends a line, waits for the reply, and then
		2021	creates the next connection. This is a rather bad benchmark, as it doesn't
		2022	test the efficiency of the framework or much non-blocking I/O, but it is a
		2023	benchmark nevertheless.
		2024
		2025	name runtime
		2026	Lambda/select 0.330 sec
		2027	+ optimized 0.122 sec
		2028	Lambda/AnyEvent 0.327 sec
		2029	+ optimized 0.138 sec
		2030	Raw sockets/select 0.077 sec
		2031	POE/select, components 0.662 sec
		2032	POE/select, raw sockets 0.226 sec
		2033	POE/select, optimized 0.404 sec
		2034
		2035	AnyEvent/select/nb 0.085 sec
		2036	AnyEvent/EV/nb 0.068 sec
		2037	+state machine 0.134 sec
		2038
		2039	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2040	benchmarks actually make blocking connects and use 100% blocking I/O,
		2041	defeating the purpose of an event-based solution. All of the newly
		2042	written AnyEvent benchmarks use 100% non-blocking connects (using
		2043	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2044	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2045	generally require a lot more bookkeeping and event handling than blocking
		2046	connects (which involve a single syscall only).
		2047
		2048	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2049	offers similar expressive power as POE and IO::Lambda, using conventional
		2050	Perl syntax. This means that both the echo server and the client are 100%
		2051	non-blocking, further placing it at a disadvantage.
		2052
		2053	As you can see, the AnyEvent + EV combination even beats the
		2054	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2055	backend easily beats IO::Lambda and POE.
		2056
		2057	And even the 100% non-blocking version written using the high-level (and
		2058	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda by a
		2059	large margin, even though it does all of DNS, tcp-connect and socket I/O
		2060	in a non-blocking way.
		2061
		2062	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2063	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2064	part of the IO::lambda distribution and were used without any changes.
		2065
		2066
		2067	=head1 SIGNALS
		2068
		2069	AnyEvent currently installs handlers for these signals:
		2070
		2071	=over 4
		2072
		2073	=item SIGCHLD
		2074
		2075	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2076	emulation for event loops that do not support them natively. Also, some
		2077	event loops install a similar handler.
		2078
		2079	If, when AnyEvent is loaded, SIGCHLD is set to IGNORE, then AnyEvent will
		2080	reset it to default, to avoid losing child exit statuses.
		2081
		2082	=item SIGPIPE
		2083
		2084	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2085	when AnyEvent gets loaded.
		2086
		2087	The rationale for this is that AnyEvent users usually do not really depend
		2088	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2089	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2090	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2091	some random socket.
		2092
		2093	The rationale for installing a no-op handler as opposed to ignoring it is
		2094	that this way, the handler will be restored to defaults on exec.
		2095
		2096	Feel free to install your own handler, or reset it to defaults.
		2097
		2098	=back
		2099
		2100	=cut
		2101
		2102	undef $SIG{CHLD}
		2103	if $SIG{CHLD} eq 'IGNORE';
		2104
		2105	$SIG{PIPE} = sub { }
		2106	unless defined $SIG{PIPE};
1397		2107
1398	=head1 FORK	2108	=head1 FORK
1399		2109
1400	Most event libraries are not fork-safe. The ones who are usually are	2110	Most event libraries are not fork-safe. The ones who are usually are
1401	because they rely on inefficient but fork-safe C<select> or C<poll>	2111	because they rely on inefficient but fork-safe C<select> or C<poll>
…		…
1415	specified in the variable.	2125	specified in the variable.
1416		2126
1417	You can make AnyEvent completely ignore this variable by deleting it	2127	You can make AnyEvent completely ignore this variable by deleting it
1418	before the first watcher gets created, e.g. with a C<BEGIN> block:	2128	before the first watcher gets created, e.g. with a C<BEGIN> block:
1419		2129
1420	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	2130	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1421		2131
1422	use AnyEvent;	2132	use AnyEvent;
1423		2133
1424	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can	2134	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1425	be used to probe what backend is used and gain other information (which is	2135	be used to probe what backend is used and gain other information (which is
1426	probably even less useful to an attacker than PERL_ANYEVENT_MODEL).	2136	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2137	$ENV{PERL_ANYEVENT_STRICT}.
		2138
		2139	Note that AnyEvent will remove I<all> environment variables starting with
		2140	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2141	enabled.
		2142
		2143
		2144	=head1 BUGS
		2145
		2146	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2147	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2148	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2149	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2150	pronounced).
1427		2151
1428		2152
1429	=head1 SEE ALSO	2153	=head1 SEE ALSO
		2154
		2155	Utility functions: L<AnyEvent::Util>.
1430		2156
1431	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,	2157	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
1432	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.	2158	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
1433		2159
1434	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,	2160	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
1435	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,	2161	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
1436	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,	2162	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1437	L<AnyEvent::Impl::POE>.	2163	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>.
1438		2164
		2165	Non-blocking file handles, sockets, TCP clients and
		2166	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
		2167
		2168	Asynchronous DNS: L<AnyEvent::DNS>.
		2169
1439	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,	2170	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>,
		2171	L<Coro::Event>,
1440		2172
1441	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	2173	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::XMPP>,
		2174	L<AnyEvent::HTTP>.
1442		2175
1443		2176
1444	=head1 AUTHOR	2177	=head1 AUTHOR
1445		2178
1446	Marc Lehmann <schmorp@schmorp.de>	2179	Marc Lehmann <schmorp@schmorp.de>
1447	http://home.schmorp.de/	2180	http://home.schmorp.de/
1448		2181
1449	=cut	2182	=cut
1450		2183
1451	1	2184	1
1452		2185

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