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Revision 1.265 by root, Wed Jul 29 13:10:58 2009 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent - provide framework for multiple event loops	3	AnyEvent - the DBI of event loop programming
4		4
5	EV, Event, Coro::EV, Coro::Event, Glib, Tk, Perl, Event::Lib, Qt - various supported event loops	5	EV, Event, Glib, Tk, Perl, Event::Lib, Irssi, rxvt-unicode, IO::Async, Qt
		6	and POE are various supported event loops/environments.
6		7
7	=head1 SYNOPSIS	8	=head1 SYNOPSIS
8		9
9	use AnyEvent;	10	use AnyEvent;
10		11
		12	# file descriptor readable
11	my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub {	13	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
		14
		15	# one-shot or repeating timers
		16	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
		17	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...
		18
		19	print AnyEvent->now; # prints current event loop time
		20	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
		21
		22	# POSIX signal
		23	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
		24
		25	# child process exit
		26	my $w = AnyEvent->child (pid => $pid, cb => sub {
		27	my ($pid, $status) = @_;
12	...	28	...
13	});	29	});
14		30
15	my $w = AnyEvent->timer (after => $seconds, cb => sub {	31	# called when event loop idle (if applicable)
16	...	32	my $w = AnyEvent->idle (cb => sub { ... });
17	});
18		33
19	my $w = AnyEvent->condvar; # stores whether a condition was flagged	34	my $w = AnyEvent->condvar; # stores whether a condition was flagged
		35	$w->send; # wake up current and all future recv's
20	$w->wait; # enters "main loop" till $condvar gets ->broadcast	36	$w->recv; # enters "main loop" till $condvar gets ->send
21	$w->broadcast; # wake up current and all future wait's	37	# use a condvar in callback mode:
		38	$w->cb (sub { $_[0]->recv });
		39
		40	=head1 INTRODUCTION/TUTORIAL
		41
		42	This manpage is mainly a reference manual. If you are interested
		43	in a tutorial or some gentle introduction, have a look at the
		44	L<AnyEvent::Intro> manpage.
		45
		46	=head1 SUPPORT
		47
		48	There is a mailinglist for discussing all things AnyEvent, and an IRC
		49	channel, too.
		50
		51	See the AnyEvent project page at the B<Schmorpforge Ta-Sa Software
		52	Repository>, at L<http://anyevent.schmorp.de>, for more info.
22		53
23	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)	54	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
24		55
25	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	56	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
26	nowadays. So what is different about AnyEvent?	57	nowadays. So what is different about AnyEvent?
27		58
28	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of	59	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
29	policy> and AnyEvent is I<small and efficient>.	60	policy> and AnyEvent is I<small and efficient>.
30		61
31	First and foremost, I<AnyEvent is not an event model> itself, it only	62	First and foremost, I<AnyEvent is not an event model> itself, it only
32	interfaces to whatever event model the main program happens to use in a	63	interfaces to whatever event model the main program happens to use, in a
33	pragmatic way. For event models and certain classes of immortals alike,	64	pragmatic way. For event models and certain classes of immortals alike,
34	the statement "there can only be one" is a bitter reality: In general,	65	the statement "there can only be one" is a bitter reality: In general,
35	only one event loop can be active at the same time in a process. AnyEvent	66	only one event loop can be active at the same time in a process. AnyEvent
36	helps hiding the differences between those event loops.	67	cannot change this, but it can hide the differences between those event
		68	loops.
37		69
38	The goal of AnyEvent is to offer module authors the ability to do event	70	The goal of AnyEvent is to offer module authors the ability to do event
39	programming (waiting for I/O or timer events) without subscribing to a	71	programming (waiting for I/O or timer events) without subscribing to a
40	religion, a way of living, and most importantly: without forcing your	72	religion, a way of living, and most importantly: without forcing your
41	module users into the same thing by forcing them to use the same event	73	module users into the same thing by forcing them to use the same event
42	model you use.	74	model you use.
43		75
44	For modules like POE or IO::Async (which is a total misnomer as it is	76	For modules like POE or IO::Async (which is a total misnomer as it is
45	actually doing all I/O I<synchronously>...), using them in your module is	77	actually doing all I/O I<synchronously>...), using them in your module is
46	like joining a cult: After you joined, you are dependent on them and you	78	like joining a cult: After you joined, you are dependent on them and you
47	cannot use anything else, as it is simply incompatible to everything that	79	cannot use anything else, as they are simply incompatible to everything
48	isn't itself. What's worse, all the potential users of your module are	80	that isn't them. What's worse, all the potential users of your
49	I<also> forced to use the same event loop you use.	81	module are I<also> forced to use the same event loop you use.
50		82
51	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	83	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
52	fine. AnyEvent + Tk works fine etc. etc. but none of these work together	84	fine. AnyEvent + Tk works fine etc. etc. but none of these work together
53	with the rest: POE + IO::Async? no go. Tk + Event? no go. Again: if	85	with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if
54	your module uses one of those, every user of your module has to use it,	86	your module uses one of those, every user of your module has to use it,
55	too. But if your module uses AnyEvent, it works transparently with all	87	too. But if your module uses AnyEvent, it works transparently with all
56	event models it supports (including stuff like POE and IO::Async, as long	88	event models it supports (including stuff like IO::Async, as long as those
57	as those use one of the supported event loops. It is trivial to add new	89	use one of the supported event loops. It is trivial to add new event loops
58	event loops to AnyEvent, too, so it is future-proof).	90	to AnyEvent, too, so it is future-proof).
59		91
60	In addition to being free of having to use I<the one and only true event	92	In addition to being free of having to use I<the one and only true event
61	model>, AnyEvent also is free of bloat and policy: with POE or similar	93	model>, AnyEvent also is free of bloat and policy: with POE or similar
62	modules, you get an enourmous amount of code and strict rules you have to	94	modules, you get an enormous amount of code and strict rules you have to
63	follow. AnyEvent, on the other hand, is lean and up to the point, by only	95	follow. AnyEvent, on the other hand, is lean and up to the point, by only
64	offering the functionality that is necessary, in as thin as a wrapper as	96	offering the functionality that is necessary, in as thin as a wrapper as
65	technically possible.	97	technically possible.
66		98
		99	Of course, AnyEvent comes with a big (and fully optional!) toolbox
		100	of useful functionality, such as an asynchronous DNS resolver, 100%
		101	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
		102	such as Windows) and lots of real-world knowledge and workarounds for
		103	platform bugs and differences.
		104
67	Of course, if you want lots of policy (this can arguably be somewhat	105	Now, if you I<do want> lots of policy (this can arguably be somewhat
68	useful) and you want to force your users to use the one and only event	106	useful) and you want to force your users to use the one and only event
69	model, you should I<not> use this module.	107	model, you should I<not> use this module.
70
71		108
72	=head1 DESCRIPTION	109	=head1 DESCRIPTION
73		110
74	L<AnyEvent> provides an identical interface to multiple event loops. This	111	L<AnyEvent> provides an identical interface to multiple event loops. This
75	allows module authors to utilise an event loop without forcing module	112	allows module authors to utilise an event loop without forcing module
…		…
78		115
79	The interface itself is vaguely similar, but not identical to the L<Event>	116	The interface itself is vaguely similar, but not identical to the L<Event>
80	module.	117	module.
81		118
82	During the first call of any watcher-creation method, the module tries	119	During the first call of any watcher-creation method, the module tries
83	to detect the currently loaded event loop by probing whether one of	120	to detect the currently loaded event loop by probing whether one of the
84	the following modules is already loaded: L<Coro::EV>, L<Coro::Event>,	121	following modules is already loaded: L<EV>,
85	L<EV>, L<Event>, L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>. The first one	122	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,
86	found is used. If none are found, the module tries to load these modules	123	L<POE>. The first one found is used. If none are found, the module tries
87	(excluding Event::Lib and Qt) in the order given. The first one that can	124	to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl
		125	adaptor should always succeed) in the order given. The first one that can
88	be successfully loaded will be used. If, after this, still none could be	126	be successfully loaded will be used. If, after this, still none could be
89	found, AnyEvent will fall back to a pure-perl event loop, which is not	127	found, AnyEvent will fall back to a pure-perl event loop, which is not
90	very efficient, but should work everywhere.	128	very efficient, but should work everywhere.
91		129
92	Because AnyEvent first checks for modules that are already loaded, loading	130	Because AnyEvent first checks for modules that are already loaded, loading
…		…
102	starts using it, all bets are off. Maybe you should tell their authors to	140	starts using it, all bets are off. Maybe you should tell their authors to
103	use AnyEvent so their modules work together with others seamlessly...	141	use AnyEvent so their modules work together with others seamlessly...
104		142
105	The pure-perl implementation of AnyEvent is called	143	The pure-perl implementation of AnyEvent is called
106	C<AnyEvent::Impl::Perl>. Like other event modules you can load it	144	C<AnyEvent::Impl::Perl>. Like other event modules you can load it
107	explicitly.	145	explicitly and enjoy the high availability of that event loop :)
108		146
109	=head1 WATCHERS	147	=head1 WATCHERS
110		148
111	AnyEvent has the central concept of a I<watcher>, which is an object that	149	AnyEvent has the central concept of a I<watcher>, which is an object that
112	stores relevant data for each kind of event you are waiting for, such as	150	stores relevant data for each kind of event you are waiting for, such as
113	the callback to call, the filehandle to watch, etc.	151	the callback to call, the file handle to watch, etc.
114		152
115	These watchers are normal Perl objects with normal Perl lifetime. After	153	These watchers are normal Perl objects with normal Perl lifetime. After
116	creating a watcher it will immediately "watch" for events and invoke the	154	creating a watcher it will immediately "watch" for events and invoke the
117	callback when the event occurs (of course, only when the event model	155	callback when the event occurs (of course, only when the event model
118	is in control).	156	is in control).
119		157
		158	Note that B<callbacks must not permanently change global variables>
		159	potentially in use by the event loop (such as C<$_> or C<$[>) and that B<<
		160	callbacks must not C<die> >>. The former is good programming practise in
		161	Perl and the latter stems from the fact that exception handling differs
		162	widely between event loops.
		163
120	To disable the watcher you have to destroy it (e.g. by setting the	164	To disable the watcher you have to destroy it (e.g. by setting the
121	variable you store it in to C<undef> or otherwise deleting all references	165	variable you store it in to C<undef> or otherwise deleting all references
122	to it).	166	to it).
123		167
124	All watchers are created by calling a method on the C<AnyEvent> class.	168	All watchers are created by calling a method on the C<AnyEvent> class.
…		…
126	Many watchers either are used with "recursion" (repeating timers for	170	Many watchers either are used with "recursion" (repeating timers for
127	example), or need to refer to their watcher object in other ways.	171	example), or need to refer to their watcher object in other ways.
128		172
129	An any way to achieve that is this pattern:	173	An any way to achieve that is this pattern:
130		174
131	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	175	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
132	# you can use $w here, for example to undef it	176	# you can use $w here, for example to undef it
133	undef $w;	177	undef $w;
134	});	178	});
135		179
136	Note that C<my $w; $w => combination. This is necessary because in Perl,	180	Note that C<my $w; $w => combination. This is necessary because in Perl,
137	my variables are only visible after the statement in which they are	181	my variables are only visible after the statement in which they are
138	declared.	182	declared.
139		183
140	=head2 IO WATCHERS	184	=head2 I/O WATCHERS
141		185
142	You can create an I/O watcher by calling the C<< AnyEvent->io >> method	186	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
143	with the following mandatory key-value pairs as arguments:	187	with the following mandatory key-value pairs as arguments:
144		188
145	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch for	189	C<fh> is the Perl I<file handle> (or a naked file descriptor) to watch
		190	for events (AnyEvent might or might not keep a reference to this file
		191	handle). Note that only file handles pointing to things for which
		192	non-blocking operation makes sense are allowed. This includes sockets,
		193	most character devices, pipes, fifos and so on, but not for example files
		194	or block devices.
		195
146	events. C<poll> must be a string that is either C<r> or C<w>, which	196	C<poll> must be a string that is either C<r> or C<w>, which creates a
147	creates a watcher waiting for "r"eadable or "w"ritable events,	197	watcher waiting for "r"eadable or "w"ritable events, respectively.
		198
148	respectively. C<cb> is the callback to invoke each time the file handle	199	C<cb> is the callback to invoke each time the file handle becomes ready.
149	becomes ready.
150		200
151	As long as the I/O watcher exists it will keep the file descriptor or a	201	Although the callback might get passed parameters, their value and
152	copy of it alive/open.	202	presence is undefined and you cannot rely on them. Portable AnyEvent
		203	callbacks cannot use arguments passed to I/O watcher callbacks.
153		204
		205	The I/O watcher might use the underlying file descriptor or a copy of it.
154	It is not allowed to close a file handle as long as any watcher is active	206	You must not close a file handle as long as any watcher is active on the
155	on the underlying file descriptor.	207	underlying file descriptor.
156		208
157	Some event loops issue spurious readyness notifications, so you should	209	Some event loops issue spurious readyness notifications, so you should
158	always use non-blocking calls when reading/writing from/to your file	210	always use non-blocking calls when reading/writing from/to your file
159	handles.	211	handles.
160		212
161	Example:
162
163	# wait for readability of STDIN, then read a line and disable the watcher	213	Example: wait for readability of STDIN, then read a line and disable the
		214	watcher.
		215
164	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	216	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
165	chomp (my $input = <STDIN>);	217	chomp (my $input = <STDIN>);
166	warn "read: $input\n";	218	warn "read: $input\n";
167	undef $w;	219	undef $w;
168	});	220	});
…		…
171		223
172	You can create a time watcher by calling the C<< AnyEvent->timer >>	224	You can create a time watcher by calling the C<< AnyEvent->timer >>
173	method with the following mandatory arguments:	225	method with the following mandatory arguments:
174		226
175	C<after> specifies after how many seconds (fractional values are	227	C<after> specifies after how many seconds (fractional values are
176	supported) should the timer activate. C<cb> the callback to invoke in that	228	supported) the callback should be invoked. C<cb> is the callback to invoke
177	case.	229	in that case.
178		230
179	The timer callback will be invoked at most once: if you want a repeating	231	Although the callback might get passed parameters, their value and
180	timer you have to create a new watcher (this is a limitation by both Tk	232	presence is undefined and you cannot rely on them. Portable AnyEvent
181	and Glib).	233	callbacks cannot use arguments passed to time watcher callbacks.
182		234
183	Example:	235	The callback will normally be invoked once only. If you specify another
		236	parameter, C<interval>, as a strictly positive number (> 0), then the
		237	callback will be invoked regularly at that interval (in fractional
		238	seconds) after the first invocation. If C<interval> is specified with a
		239	false value, then it is treated as if it were missing.
184		240
		241	The callback will be rescheduled before invoking the callback, but no
		242	attempt is done to avoid timer drift in most backends, so the interval is
		243	only approximate.
		244
185	# fire an event after 7.7 seconds	245	Example: fire an event after 7.7 seconds.
		246
186	my $w = AnyEvent->timer (after => 7.7, cb => sub {	247	my $w = AnyEvent->timer (after => 7.7, cb => sub {
187	warn "timeout\n";	248	warn "timeout\n";
188	});	249	});
189		250
190	# to cancel the timer:	251	# to cancel the timer:
191	undef $w;	252	undef $w;
192		253
193	Example 2:
194
195	# fire an event after 0.5 seconds, then roughly every second	254	Example 2: fire an event after 0.5 seconds, then roughly every second.
196	my $w;
197		255
198	my $cb = sub {
199	# cancel the old timer while creating a new one
200	$w = AnyEvent->timer (after => 1, cb => $cb);	256	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		257	warn "timeout\n";
201	};	258	};
202
203	# start the "loop" by creating the first watcher
204	$w = AnyEvent->timer (after => 0.5, cb => $cb);
205		259
206	=head3 TIMING ISSUES	260	=head3 TIMING ISSUES
207		261
208	There are two ways to handle timers: based on real time (relative, "fire	262	There are two ways to handle timers: based on real time (relative, "fire
209	in 10 seconds") and based on wallclock time (absolute, "fire at 12	263	in 10 seconds") and based on wallclock time (absolute, "fire at 12
…		…
221	timers.	275	timers.
222		276
223	AnyEvent always prefers relative timers, if available, matching the	277	AnyEvent always prefers relative timers, if available, matching the
224	AnyEvent API.	278	AnyEvent API.
225		279
		280	AnyEvent has two additional methods that return the "current time":
		281
		282	=over 4
		283
		284	=item AnyEvent->time
		285
		286	This returns the "current wallclock time" as a fractional number of
		287	seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
		288	return, and the result is guaranteed to be compatible with those).
		289
		290	It progresses independently of any event loop processing, i.e. each call
		291	will check the system clock, which usually gets updated frequently.
		292
		293	=item AnyEvent->now
		294
		295	This also returns the "current wallclock time", but unlike C<time>, above,
		296	this value might change only once per event loop iteration, depending on
		297	the event loop (most return the same time as C<time>, above). This is the
		298	time that AnyEvent's timers get scheduled against.
		299
		300	I<In almost all cases (in all cases if you don't care), this is the
		301	function to call when you want to know the current time.>
		302
		303	This function is also often faster then C<< AnyEvent->time >>, and
		304	thus the preferred method if you want some timestamp (for example,
		305	L<AnyEvent::Handle> uses this to update it's activity timeouts).
		306
		307	The rest of this section is only of relevance if you try to be very exact
		308	with your timing, you can skip it without bad conscience.
		309
		310	For a practical example of when these times differ, consider L<Event::Lib>
		311	and L<EV> and the following set-up:
		312
		313	The event loop is running and has just invoked one of your callback at
		314	time=500 (assume no other callbacks delay processing). In your callback,
		315	you wait a second by executing C<sleep 1> (blocking the process for a
		316	second) and then (at time=501) you create a relative timer that fires
		317	after three seconds.
		318
		319	With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
		320	both return C<501>, because that is the current time, and the timer will
		321	be scheduled to fire at time=504 (C<501> + C<3>).
		322
		323	With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
		324	time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
		325	last event processing phase started. With L<EV>, your timer gets scheduled
		326	to run at time=503 (C<500> + C<3>).
		327
		328	In one sense, L<Event::Lib> is more exact, as it uses the current time
		329	regardless of any delays introduced by event processing. However, most
		330	callbacks do not expect large delays in processing, so this causes a
		331	higher drift (and a lot more system calls to get the current time).
		332
		333	In another sense, L<EV> is more exact, as your timer will be scheduled at
		334	the same time, regardless of how long event processing actually took.
		335
		336	In either case, if you care (and in most cases, you don't), then you
		337	can get whatever behaviour you want with any event loop, by taking the
		338	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
		339	account.
		340
		341	=item AnyEvent->now_update
		342
		343	Some event loops (such as L<EV> or L<AnyEvent::Impl::Perl>) cache
		344	the current time for each loop iteration (see the discussion of L<<
		345	AnyEvent->now >>, above).
		346
		347	When a callback runs for a long time (or when the process sleeps), then
		348	this "current" time will differ substantially from the real time, which
		349	might affect timers and time-outs.
		350
		351	When this is the case, you can call this method, which will update the
		352	event loop's idea of "current time".
		353
		354	Note that updating the time I<might> cause some events to be handled.
		355
		356	=back
		357
226	=head2 SIGNAL WATCHERS	358	=head2 SIGNAL WATCHERS
227		359
228	You can watch for signals using a signal watcher, C<signal> is the signal	360	You can watch for signals using a signal watcher, C<signal> is the signal
229	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to	361	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
230	be invoked whenever a signal occurs.	362	callback to be invoked whenever a signal occurs.
231		363
		364	Although the callback might get passed parameters, their value and
		365	presence is undefined and you cannot rely on them. Portable AnyEvent
		366	callbacks cannot use arguments passed to signal watcher callbacks.
		367
232	Multiple signal occurances can be clumped together into one callback	368	Multiple signal occurrences can be clumped together into one callback
233	invocation, and callback invocation will be synchronous. synchronous means	369	invocation, and callback invocation will be synchronous. Synchronous means
234	that it might take a while until the signal gets handled by the process,	370	that it might take a while until the signal gets handled by the process,
235	but it is guarenteed not to interrupt any other callbacks.	371	but it is guaranteed not to interrupt any other callbacks.
236		372
237	The main advantage of using these watchers is that you can share a signal	373	The main advantage of using these watchers is that you can share a signal
238	between multiple watchers.	374	between multiple watchers, and AnyEvent will ensure that signals will not
		375	interrupt your program at bad times.
239		376
240	This watcher might use C<%SIG>, so programs overwriting those signals	377	This watcher might use C<%SIG> (depending on the event loop used),
241	directly will likely not work correctly.	378	so programs overwriting those signals directly will likely not work
		379	correctly.
242		380
243	Example: exit on SIGINT	381	Example: exit on SIGINT
244		382
245	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	383	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
246		384
		385	=head3 Signal Races, Delays and Workarounds
		386
		387	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		388	callbacks to signals in a generic way, which is a pity, as you cannot do
		389	race-free signal handling in perl. AnyEvent will try to do it's best, but
		390	in some cases, signals will be delayed. The maximum time a signal might
		391	be delayed is specified in C<$AnyEvent::MAX_SIGNAL_LATENCY> (default: 10
		392	seconds). This variable can be changed only before the first signal
		393	watcher is created, and should be left alone otherwise. Higher values
		394	will cause fewer spurious wake-ups, which is better for power and CPU
		395	saving. All these problems can be avoided by installing the optional
		396	L<Async::Interrupt> module. This will not work with inherently broken
		397	event loops such as L<Event> or L<Event::Lib> (and not with L<POE>
		398	currently, as POE does it's own workaround with one-second latency). With
		399	those, you just have to suffer the delays.
		400
247	=head2 CHILD PROCESS WATCHERS	401	=head2 CHILD PROCESS WATCHERS
248		402
249	You can also watch on a child process exit and catch its exit status.	403	You can also watch on a child process exit and catch its exit status.
250		404
251	The child process is specified by the C<pid> argument (if set to C<0>, it	405	The child process is specified by the C<pid> argument (one some backends,
252	watches for any child process exit). The watcher will trigger as often	406	using C<0> watches for any child process exit, on others this will
253	as status change for the child are received. This works by installing a	407	croak). The watcher will be triggered only when the child process has
254	signal handler for C<SIGCHLD>. The callback will be called with the pid	408	finished and an exit status is available, not on any trace events
255	and exit status (as returned by waitpid).	409	(stopped/continued).
256		410
257	Example: wait for pid 1333	411	The callback will be called with the pid and exit status (as returned by
		412	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		413	callback arguments.
258		414
		415	This watcher type works by installing a signal handler for C<SIGCHLD>,
		416	and since it cannot be shared, nothing else should use SIGCHLD or reap
		417	random child processes (waiting for specific child processes, e.g. inside
		418	C<system>, is just fine).
		419
		420	There is a slight catch to child watchers, however: you usually start them
		421	I<after> the child process was created, and this means the process could
		422	have exited already (and no SIGCHLD will be sent anymore).
		423
		424	Not all event models handle this correctly (neither POE nor IO::Async do,
		425	see their AnyEvent::Impl manpages for details), but even for event models
		426	that I<do> handle this correctly, they usually need to be loaded before
		427	the process exits (i.e. before you fork in the first place). AnyEvent's
		428	pure perl event loop handles all cases correctly regardless of when you
		429	start the watcher.
		430
		431	This means you cannot create a child watcher as the very first
		432	thing in an AnyEvent program, you I<have> to create at least one
		433	watcher before you C<fork> the child (alternatively, you can call
		434	C<AnyEvent::detect>).
		435
		436	As most event loops do not support waiting for child events, they will be
		437	emulated by AnyEvent in most cases, in which the latency and race problems
		438	mentioned in the description of signal watchers apply.
		439
		440	Example: fork a process and wait for it
		441
		442	my $done = AnyEvent->condvar;
		443
		444	my $pid = fork or exit 5;
		445
259	my $w = AnyEvent->child (	446	my $w = AnyEvent->child (
260	pid => 1333,	447	pid => $pid,
261	cb => sub {	448	cb => sub {
262	my ($pid, $status) = @_;	449	my ($pid, $status) = @_;
263	warn "pid $pid exited with status $status";	450	warn "pid $pid exited with status $status";
		451	$done->send;
264	},	452	},
265	);	453	);
		454
		455	# do something else, then wait for process exit
		456	$done->recv;
		457
		458	=head2 IDLE WATCHERS
		459
		460	Sometimes there is a need to do something, but it is not so important
		461	to do it instantly, but only when there is nothing better to do. This
		462	"nothing better to do" is usually defined to be "no other events need
		463	attention by the event loop".
		464
		465	Idle watchers ideally get invoked when the event loop has nothing
		466	better to do, just before it would block the process to wait for new
		467	events. Instead of blocking, the idle watcher is invoked.
		468
		469	Most event loops unfortunately do not really support idle watchers (only
		470	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		471	will simply call the callback "from time to time".
		472
		473	Example: read lines from STDIN, but only process them when the
		474	program is otherwise idle:
		475
		476	my @lines; # read data
		477	my $idle_w;
		478	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		479	push @lines, scalar <STDIN>;
		480
		481	# start an idle watcher, if not already done
		482	$idle_w ||= AnyEvent->idle (cb => sub {
		483	# handle only one line, when there are lines left
		484	if (my $line = shift @lines) {
		485	print "handled when idle: $line";
		486	} else {
		487	# otherwise disable the idle watcher again
		488	undef $idle_w;
		489	}
		490	});
		491	});
266		492
267	=head2 CONDITION VARIABLES	493	=head2 CONDITION VARIABLES
268		494
		495	If you are familiar with some event loops you will know that all of them
		496	require you to run some blocking "loop", "run" or similar function that
		497	will actively watch for new events and call your callbacks.
		498
		499	AnyEvent is slightly different: it expects somebody else to run the event
		500	loop and will only block when necessary (usually when told by the user).
		501
		502	The instrument to do that is called a "condition variable", so called
		503	because they represent a condition that must become true.
		504
		505	Now is probably a good time to look at the examples further below.
		506
269	Condition variables can be created by calling the C<< AnyEvent->condvar >>	507	Condition variables can be created by calling the C<< AnyEvent->condvar
270	method without any arguments.	508	>> method, usually without arguments. The only argument pair allowed is
		509	C<cb>, which specifies a callback to be called when the condition variable
		510	becomes true, with the condition variable as the first argument (but not
		511	the results).
271		512
272	A condition variable waits for a condition - precisely that the C<<	513	After creation, the condition variable is "false" until it becomes "true"
273	->broadcast >> method has been called.	514	by calling the C<send> method (or calling the condition variable as if it
		515	were a callback, read about the caveats in the description for the C<<
		516	->send >> method).
274		517
275	They are very useful to signal that a condition has been fulfilled, for	518	Condition variables are similar to callbacks, except that you can
		519	optionally wait for them. They can also be called merge points - points
		520	in time where multiple outstanding events have been processed. And yet
		521	another way to call them is transactions - each condition variable can be
		522	used to represent a transaction, which finishes at some point and delivers
		523	a result. And yet some people know them as "futures" - a promise to
		524	compute/deliver something that you can wait for.
		525
		526	Condition variables are very useful to signal that something has finished,
276	example, if you write a module that does asynchronous http requests,	527	for example, if you write a module that does asynchronous http requests,
277	then a condition variable would be the ideal candidate to signal the	528	then a condition variable would be the ideal candidate to signal the
278	availability of results.	529	availability of results. The user can either act when the callback is
		530	called or can synchronously C<< ->recv >> for the results.
279		531
280	You can also use condition variables to block your main program until	532	You can also use them to simulate traditional event loops - for example,
281	an event occurs - for example, you could C<< ->wait >> in your main	533	you can block your main program until an event occurs - for example, you
282	program until the user clicks the Quit button in your app, which would C<<	534	could C<< ->recv >> in your main program until the user clicks the Quit
283	->broadcast >> the "quit" event.	535	button of your app, which would C<< ->send >> the "quit" event.
284		536
285	Note that condition variables recurse into the event loop - if you have	537	Note that condition variables recurse into the event loop - if you have
286	two pirces of code that call C<< ->wait >> in a round-robbin fashion, you	538	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
287	lose. Therefore, condition variables are good to export to your caller, but	539	lose. Therefore, condition variables are good to export to your caller, but
288	you should avoid making a blocking wait yourself, at least in callbacks,	540	you should avoid making a blocking wait yourself, at least in callbacks,
289	as this asks for trouble.	541	as this asks for trouble.
290		542
291	This object has two methods:	543	Condition variables are represented by hash refs in perl, and the keys
		544	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
		545	easy (it is often useful to build your own transaction class on top of
		546	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
		547	it's C<new> method in your own C<new> method.
292		548
293	=over 4	549	There are two "sides" to a condition variable - the "producer side" which
		550	eventually calls C<< -> send >>, and the "consumer side", which waits
		551	for the send to occur.
294		552
295	=item $cv->wait	553	Example: wait for a timer.
296
297	Wait (blocking if necessary) until the C<< ->broadcast >> method has been
298	called on c<$cv>, while servicing other watchers normally.
299
300	You can only wait once on a condition - additional calls will return
301	immediately.
302
303	Not all event models support a blocking wait - some die in that case
304	(programs might want to do that to stay interactive), so I<if you are
305	using this from a module, never require a blocking wait>, but let the
306	caller decide whether the call will block or not (for example, by coupling
307	condition variables with some kind of request results and supporting
308	callbacks so the caller knows that getting the result will not block,
309	while still suppporting blocking waits if the caller so desires).
310
311	Another reason I<never> to C<< ->wait >> in a module is that you cannot
312	sensibly have two C<< ->wait >>'s in parallel, as that would require
313	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
314	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and
315	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
316	from different coroutines, however).
317
318	=item $cv->broadcast
319
320	Flag the condition as ready - a running C<< ->wait >> and all further
321	calls to C<wait> will (eventually) return after this method has been
322	called. If nobody is waiting the broadcast will be remembered..
323
324	=back
325
326	Example:
327		554
328	# wait till the result is ready	555	# wait till the result is ready
329	my $result_ready = AnyEvent->condvar;	556	my $result_ready = AnyEvent->condvar;
330		557
331	# do something such as adding a timer	558	# do something such as adding a timer
332	# or socket watcher the calls $result_ready->broadcast	559	# or socket watcher the calls $result_ready->send
333	# when the "result" is ready.	560	# when the "result" is ready.
334	# in this case, we simply use a timer:	561	# in this case, we simply use a timer:
335	my $w = AnyEvent->timer (	562	my $w = AnyEvent->timer (
336	after => 1,	563	after => 1,
337	cb => sub { $result_ready->broadcast },	564	cb => sub { $result_ready->send },
338	);	565	);
339		566
340	# this "blocks" (while handling events) till the watcher	567	# this "blocks" (while handling events) till the callback
341	# calls broadcast	568	# calls -<send
342	$result_ready->wait;	569	$result_ready->recv;
		570
		571	Example: wait for a timer, but take advantage of the fact that condition
		572	variables are also callable directly.
		573
		574	my $done = AnyEvent->condvar;
		575	my $delay = AnyEvent->timer (after => 5, cb => $done);
		576	$done->recv;
		577
		578	Example: Imagine an API that returns a condvar and doesn't support
		579	callbacks. This is how you make a synchronous call, for example from
		580	the main program:
		581
		582	use AnyEvent::CouchDB;
		583
		584	...
		585
		586	my @info = $couchdb->info->recv;
		587
		588	And this is how you would just set a callback to be called whenever the
		589	results are available:
		590
		591	$couchdb->info->cb (sub {
		592	my @info = $_[0]->recv;
		593	});
		594
		595	=head3 METHODS FOR PRODUCERS
		596
		597	These methods should only be used by the producing side, i.e. the
		598	code/module that eventually sends the signal. Note that it is also
		599	the producer side which creates the condvar in most cases, but it isn't
		600	uncommon for the consumer to create it as well.
		601
		602	=over 4
		603
		604	=item $cv->send (...)
		605
		606	Flag the condition as ready - a running C<< ->recv >> and all further
		607	calls to C<recv> will (eventually) return after this method has been
		608	called. If nobody is waiting the send will be remembered.
		609
		610	If a callback has been set on the condition variable, it is called
		611	immediately from within send.
		612
		613	Any arguments passed to the C<send> call will be returned by all
		614	future C<< ->recv >> calls.
		615
		616	Condition variables are overloaded so one can call them directly (as if
		617	they were a code reference). Calling them directly is the same as calling
		618	C<send>.
		619
		620	=item $cv->croak ($error)
		621
		622	Similar to send, but causes all call's to C<< ->recv >> to invoke
		623	C<Carp::croak> with the given error message/object/scalar.
		624
		625	This can be used to signal any errors to the condition variable
		626	user/consumer. Doing it this way instead of calling C<croak> directly
		627	delays the error detetcion, but has the overwhelmign advantage that it
		628	diagnoses the error at the place where the result is expected, and not
		629	deep in some event clalback without connection to the actual code causing
		630	the problem.
		631
		632	=item $cv->begin ([group callback])
		633
		634	=item $cv->end
		635
		636	These two methods can be used to combine many transactions/events into
		637	one. For example, a function that pings many hosts in parallel might want
		638	to use a condition variable for the whole process.
		639
		640	Every call to C<< ->begin >> will increment a counter, and every call to
		641	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
		642	>>, the (last) callback passed to C<begin> will be executed. That callback
		643	is I<supposed> to call C<< ->send >>, but that is not required. If no
		644	callback was set, C<send> will be called without any arguments.
		645
		646	You can think of C<< $cv->send >> giving you an OR condition (one call
		647	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		648	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		649
		650	Let's start with a simple example: you have two I/O watchers (for example,
		651	STDOUT and STDERR for a program), and you want to wait for both streams to
		652	close before activating a condvar:
		653
		654	my $cv = AnyEvent->condvar;
		655
		656	$cv->begin; # first watcher
		657	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		658	defined sysread $fh1, my $buf, 4096
		659	or $cv->end;
		660	});
		661
		662	$cv->begin; # second watcher
		663	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		664	defined sysread $fh2, my $buf, 4096
		665	or $cv->end;
		666	});
		667
		668	$cv->recv;
		669
		670	This works because for every event source (EOF on file handle), there is
		671	one call to C<begin>, so the condvar waits for all calls to C<end> before
		672	sending.
		673
		674	The ping example mentioned above is slightly more complicated, as the
		675	there are results to be passwd back, and the number of tasks that are
		676	begung can potentially be zero:
		677
		678	my $cv = AnyEvent->condvar;
		679
		680	my %result;
		681	$cv->begin (sub { $cv->send (\%result) });
		682
		683	for my $host (@list_of_hosts) {
		684	$cv->begin;
		685	ping_host_then_call_callback $host, sub {
		686	$result{$host} = ...;
		687	$cv->end;
		688	};
		689	}
		690
		691	$cv->end;
		692
		693	This code fragment supposedly pings a number of hosts and calls
		694	C<send> after results for all then have have been gathered - in any
		695	order. To achieve this, the code issues a call to C<begin> when it starts
		696	each ping request and calls C<end> when it has received some result for
		697	it. Since C<begin> and C<end> only maintain a counter, the order in which
		698	results arrive is not relevant.
		699
		700	There is an additional bracketing call to C<begin> and C<end> outside the
		701	loop, which serves two important purposes: first, it sets the callback
		702	to be called once the counter reaches C<0>, and second, it ensures that
		703	C<send> is called even when C<no> hosts are being pinged (the loop
		704	doesn't execute once).
		705
		706	This is the general pattern when you "fan out" into multiple (but
		707	potentially none) subrequests: use an outer C<begin>/C<end> pair to set
		708	the callback and ensure C<end> is called at least once, and then, for each
		709	subrequest you start, call C<begin> and for each subrequest you finish,
		710	call C<end>.
		711
		712	=back
		713
		714	=head3 METHODS FOR CONSUMERS
		715
		716	These methods should only be used by the consuming side, i.e. the
		717	code awaits the condition.
		718
		719	=over 4
		720
		721	=item $cv->recv
		722
		723	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
		724	>> methods have been called on c<$cv>, while servicing other watchers
		725	normally.
		726
		727	You can only wait once on a condition - additional calls are valid but
		728	will return immediately.
		729
		730	If an error condition has been set by calling C<< ->croak >>, then this
		731	function will call C<croak>.
		732
		733	In list context, all parameters passed to C<send> will be returned,
		734	in scalar context only the first one will be returned.
		735
		736	Note that doing a blocking wait in a callback is not supported by any
		737	event loop, that is, recursive invocation of a blocking C<< ->recv
		738	>> is not allowed, and the C<recv> call will C<croak> if such a
		739	condition is detected. This condition can be slightly loosened by using
		740	L<Coro::AnyEvent>, which allows you to do a blocking C<< ->recv >> from
		741	any thread that doesn't run the event loop itself.
		742
		743	Not all event models support a blocking wait - some die in that case
		744	(programs might want to do that to stay interactive), so I<if you are
		745	using this from a module, never require a blocking wait>. Instead, let the
		746	caller decide whether the call will block or not (for example, by coupling
		747	condition variables with some kind of request results and supporting
		748	callbacks so the caller knows that getting the result will not block,
		749	while still supporting blocking waits if the caller so desires).
		750
		751	You can ensure that C<< -recv >> never blocks by setting a callback and
		752	only calling C<< ->recv >> from within that callback (or at a later
		753	time). This will work even when the event loop does not support blocking
		754	waits otherwise.
		755
		756	=item $bool = $cv->ready
		757
		758	Returns true when the condition is "true", i.e. whether C<send> or
		759	C<croak> have been called.
		760
		761	=item $cb = $cv->cb ($cb->($cv))
		762
		763	This is a mutator function that returns the callback set and optionally
		764	replaces it before doing so.
		765
		766	The callback will be called when the condition becomes "true", i.e. when
		767	C<send> or C<croak> are called, with the only argument being the condition
		768	variable itself. Calling C<recv> inside the callback or at any later time
		769	is guaranteed not to block.
		770
		771	=back
		772
		773	=head1 SUPPORTED EVENT LOOPS/BACKENDS
		774
		775	The available backend classes are (every class has its own manpage):
		776
		777	=over 4
		778
		779	=item Backends that are autoprobed when no other event loop can be found.
		780
		781	EV is the preferred backend when no other event loop seems to be in
		782	use. If EV is not installed, then AnyEvent will try Event, and, failing
		783	that, will fall back to its own pure-perl implementation, which is
		784	available everywhere as it comes with AnyEvent itself.
		785
		786	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		787	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		788	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
		789
		790	=item Backends that are transparently being picked up when they are used.
		791
		792	These will be used when they are currently loaded when the first watcher
		793	is created, in which case it is assumed that the application is using
		794	them. This means that AnyEvent will automatically pick the right backend
		795	when the main program loads an event module before anything starts to
		796	create watchers. Nothing special needs to be done by the main program.
		797
		798	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		799	AnyEvent::Impl::Tk based on Tk, very broken.
		800	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		801	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		802	AnyEvent::Impl::Irssi used when running within irssi.
		803
		804	=item Backends with special needs.
		805
		806	Qt requires the Qt::Application to be instantiated first, but will
		807	otherwise be picked up automatically. As long as the main program
		808	instantiates the application before any AnyEvent watchers are created,
		809	everything should just work.
		810
		811	AnyEvent::Impl::Qt based on Qt.
		812
		813	Support for IO::Async can only be partial, as it is too broken and
		814	architecturally limited to even support the AnyEvent API. It also
		815	is the only event loop that needs the loop to be set explicitly, so
		816	it can only be used by a main program knowing about AnyEvent. See
		817	L<AnyEvent::Impl::Async> for the gory details.
		818
		819	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
		820
		821	=item Event loops that are indirectly supported via other backends.
		822
		823	Some event loops can be supported via other modules:
		824
		825	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		826
		827	B<WxWidgets> has no support for watching file handles. However, you can
		828	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		829	polls 20 times per second, which was considered to be too horrible to even
		830	consider for AnyEvent.
		831
		832	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		833	backend, so it can be supported through POE.
		834
		835	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		836	load L<POE> when detecting them, in the hope that POE will pick them up,
		837	in which case everything will be automatic.
		838
		839	=back
343		840
344	=head1 GLOBAL VARIABLES AND FUNCTIONS	841	=head1 GLOBAL VARIABLES AND FUNCTIONS
345		842
		843	These are not normally required to use AnyEvent, but can be useful to
		844	write AnyEvent extension modules.
		845
346	=over 4	846	=over 4
347		847
348	=item $AnyEvent::MODEL	848	=item $AnyEvent::MODEL
349		849
350	Contains C<undef> until the first watcher is being created. Then it	850	Contains C<undef> until the first watcher is being created, before the
		851	backend has been autodetected.
		852
351	contains the event model that is being used, which is the name of the	853	Afterwards it contains the event model that is being used, which is the
352	Perl class implementing the model. This class is usually one of the	854	name of the Perl class implementing the model. This class is usually one
353	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	855	of the C<AnyEvent::Impl:xxx> modules, but can be any other class in the
354	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	856	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
355		857	will be C<urxvt::anyevent>).
356	The known classes so far are:
357
358	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
359	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
360	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
361	AnyEvent::Impl::Event based on Event, second best choice.
362	AnyEvent::Impl::Glib based on Glib, third-best choice.
363	AnyEvent::Impl::Tk based on Tk, very bad choice.
364	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
365	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
366	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
367		858
368	=item AnyEvent::detect	859	=item AnyEvent::detect
369		860
370	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	861	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
371	if necessary. You should only call this function right before you would	862	if necessary. You should only call this function right before you would
372	have created an AnyEvent watcher anyway, that is, as late as possible at	863	have created an AnyEvent watcher anyway, that is, as late as possible at
373	runtime.	864	runtime, and not e.g. while initialising of your module.
		865
		866	If you need to do some initialisation before AnyEvent watchers are
		867	created, use C<post_detect>.
		868
		869	=item $guard = AnyEvent::post_detect { BLOCK }
		870
		871	Arranges for the code block to be executed as soon as the event model is
		872	autodetected (or immediately if this has already happened).
		873
		874	The block will be executed I<after> the actual backend has been detected
		875	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		876	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		877	other initialisations - see the sources of L<AnyEvent::Strict> or
		878	L<AnyEvent::AIO> to see how this is used.
		879
		880	The most common usage is to create some global watchers, without forcing
		881	event module detection too early, for example, L<AnyEvent::AIO> creates
		882	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		883	avoid autodetecting the event module at load time.
		884
		885	If called in scalar or list context, then it creates and returns an object
		886	that automatically removes the callback again when it is destroyed (or
		887	C<undef> when the hook was immediately executed). See L<AnyEvent::AIO> for
		888	a case where this is useful.
		889
		890	Example: Create a watcher for the IO::AIO module and store it in
		891	C<$WATCHER>. Only do so after the event loop is initialised, though.
		892
		893	our WATCHER;
		894
		895	my $guard = AnyEvent::post_detect {
		896	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		897	};
		898
		899	# the ||= is important in case post_detect immediately runs the block,
		900	# as to not clobber the newly-created watcher. assigning both watcher and
		901	# post_detect guard to the same variable has the advantage of users being
		902	# able to just C<undef $WATCHER> if the watcher causes them grief.
		903
		904	$WATCHER ||= $guard;
		905
		906	=item @AnyEvent::post_detect
		907
		908	If there are any code references in this array (you can C<push> to it
		909	before or after loading AnyEvent), then they will called directly after
		910	the event loop has been chosen.
		911
		912	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		913	if it is defined then the event loop has already been detected, and the
		914	array will be ignored.
		915
		916	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		917	it,as it takes care of these details.
		918
		919	This variable is mainly useful for modules that can do something useful
		920	when AnyEvent is used and thus want to know when it is initialised, but do
		921	not need to even load it by default. This array provides the means to hook
		922	into AnyEvent passively, without loading it.
374		923
375	=back	924	=back
376		925
377	=head1 WHAT TO DO IN A MODULE	926	=head1 WHAT TO DO IN A MODULE
378		927
…		…
382	Be careful when you create watchers in the module body - AnyEvent will	931	Be careful when you create watchers in the module body - AnyEvent will
383	decide which event module to use as soon as the first method is called, so	932	decide which event module to use as soon as the first method is called, so
384	by calling AnyEvent in your module body you force the user of your module	933	by calling AnyEvent in your module body you force the user of your module
385	to load the event module first.	934	to load the event module first.
386		935
387	Never call C<< ->wait >> on a condition variable unless you I<know> that	936	Never call C<< ->recv >> on a condition variable unless you I<know> that
388	the C<< ->broadcast >> method has been called on it already. This is	937	the C<< ->send >> method has been called on it already. This is
389	because it will stall the whole program, and the whole point of using	938	because it will stall the whole program, and the whole point of using
390	events is to stay interactive.	939	events is to stay interactive.
391		940
392	It is fine, however, to call C<< ->wait >> when the user of your module	941	It is fine, however, to call C<< ->recv >> when the user of your module
393	requests it (i.e. if you create a http request object ad have a method	942	requests it (i.e. if you create a http request object ad have a method
394	called C<results> that returns the results, it should call C<< ->wait >>	943	called C<results> that returns the results, it should call C<< ->recv >>
395	freely, as the user of your module knows what she is doing. always).	944	freely, as the user of your module knows what she is doing. always).
396		945
397	=head1 WHAT TO DO IN THE MAIN PROGRAM	946	=head1 WHAT TO DO IN THE MAIN PROGRAM
398		947
399	There will always be a single main program - the only place that should	948	There will always be a single main program - the only place that should
…		…
401		950
402	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	951	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
403	do anything special (it does not need to be event-based) and let AnyEvent	952	do anything special (it does not need to be event-based) and let AnyEvent
404	decide which implementation to chose if some module relies on it.	953	decide which implementation to chose if some module relies on it.
405		954
406	If the main program relies on a specific event model. For example, in	955	If the main program relies on a specific event model - for example, in
407	Gtk2 programs you have to rely on the Glib module. You should load the	956	Gtk2 programs you have to rely on the Glib module - you should load the
408	event module before loading AnyEvent or any module that uses it: generally	957	event module before loading AnyEvent or any module that uses it: generally
409	speaking, you should load it as early as possible. The reason is that	958	speaking, you should load it as early as possible. The reason is that
410	modules might create watchers when they are loaded, and AnyEvent will	959	modules might create watchers when they are loaded, and AnyEvent will
411	decide on the event model to use as soon as it creates watchers, and it	960	decide on the event model to use as soon as it creates watchers, and it
412	might chose the wrong one unless you load the correct one yourself.	961	might chose the wrong one unless you load the correct one yourself.
413		962
414	You can chose to use a rather inefficient pure-perl implementation by	963	You can chose to use a pure-perl implementation by loading the
415	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	964	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
416	behaviour everywhere, but letting AnyEvent chose is generally better.	965	everywhere, but letting AnyEvent chose the model is generally better.
		966
		967	=head2 MAINLOOP EMULATION
		968
		969	Sometimes (often for short test scripts, or even standalone programs who
		970	only want to use AnyEvent), you do not want to run a specific event loop.
		971
		972	In that case, you can use a condition variable like this:
		973
		974	AnyEvent->condvar->recv;
		975
		976	This has the effect of entering the event loop and looping forever.
		977
		978	Note that usually your program has some exit condition, in which case
		979	it is better to use the "traditional" approach of storing a condition
		980	variable somewhere, waiting for it, and sending it when the program should
		981	exit cleanly.
		982
		983
		984	=head1 OTHER MODULES
		985
		986	The following is a non-exhaustive list of additional modules that use
		987	AnyEvent as a client and can therefore be mixed easily with other AnyEvent
		988	modules and other event loops in the same program. Some of the modules
		989	come with AnyEvent, most are available via CPAN.
		990
		991	=over 4
		992
		993	=item L<AnyEvent::Util>
		994
		995	Contains various utility functions that replace often-used but blocking
		996	functions such as C<inet_aton> by event-/callback-based versions.
		997
		998	=item L<AnyEvent::Socket>
		999
		1000	Provides various utility functions for (internet protocol) sockets,
		1001	addresses and name resolution. Also functions to create non-blocking tcp
		1002	connections or tcp servers, with IPv6 and SRV record support and more.
		1003
		1004	=item L<AnyEvent::Handle>
		1005
		1006	Provide read and write buffers, manages watchers for reads and writes,
		1007	supports raw and formatted I/O, I/O queued and fully transparent and
		1008	non-blocking SSL/TLS (via L<AnyEvent::TLS>.
		1009
		1010	=item L<AnyEvent::DNS>
		1011
		1012	Provides rich asynchronous DNS resolver capabilities.
		1013
		1014	=item L<AnyEvent::HTTP>
		1015
		1016	A simple-to-use HTTP library that is capable of making a lot of concurrent
		1017	HTTP requests.
		1018
		1019	=item L<AnyEvent::HTTPD>
		1020
		1021	Provides a simple web application server framework.
		1022
		1023	=item L<AnyEvent::FastPing>
		1024
		1025	The fastest ping in the west.
		1026
		1027	=item L<AnyEvent::DBI>
		1028
		1029	Executes L<DBI> requests asynchronously in a proxy process.
		1030
		1031	=item L<AnyEvent::AIO>
		1032
		1033	Truly asynchronous I/O, should be in the toolbox of every event
		1034	programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
		1035	together.
		1036
		1037	=item L<AnyEvent::BDB>
		1038
		1039	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
		1040	L<BDB> and AnyEvent together.
		1041
		1042	=item L<AnyEvent::GPSD>
		1043
		1044	A non-blocking interface to gpsd, a daemon delivering GPS information.
		1045
		1046	=item L<AnyEvent::IRC>
		1047
		1048	AnyEvent based IRC client module family (replacing the older Net::IRC3).
		1049
		1050	=item L<AnyEvent::XMPP>
		1051
		1052	AnyEvent based XMPP (Jabber protocol) module family (replacing the older
		1053	Net::XMPP2>.
		1054
		1055	=item L<AnyEvent::IGS>
		1056
		1057	A non-blocking interface to the Internet Go Server protocol (used by
		1058	L<App::IGS>).
		1059
		1060	=item L<Net::FCP>
		1061
		1062	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
		1063	of AnyEvent.
		1064
		1065	=item L<Event::ExecFlow>
		1066
		1067	High level API for event-based execution flow control.
		1068
		1069	=item L<Coro>
		1070
		1071	Has special support for AnyEvent via L<Coro::AnyEvent>.
		1072
		1073	=back
417		1074
418	=cut	1075	=cut
419		1076
420	package AnyEvent;	1077	package AnyEvent;
421		1078
		1079	# basically a tuned-down version of common::sense
		1080	sub common_sense {
422	no warnings;	1081	# no warnings
423	use strict;	1082	${^WARNING_BITS} ^= ${^WARNING_BITS};
		1083	# use strict vars subs
		1084	$^H |= 0x00000600;
		1085	}
424		1086
		1087	BEGIN { AnyEvent::common_sense }
		1088
425	use Carp;	1089	use Carp ();
426		1090
427	our $VERSION = '3.2';	1091	our $VERSION = 4.881;
428	our $MODEL;	1092	our $MODEL;
429		1093
430	our $AUTOLOAD;	1094	our $AUTOLOAD;
431	our @ISA;	1095	our @ISA;
432		1096
433	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
434
435	our @REGISTRY;	1097	our @REGISTRY;
436		1098
		1099	our $WIN32;
		1100
		1101	our $VERBOSE;
		1102
		1103	BEGIN {
		1104	eval "sub WIN32(){ " . (($^O =~ /mswin32/i)*1) ." }";
		1105	eval "sub TAINT(){ " . (${^TAINT}*1) . " }";
		1106
		1107	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1108	if ${^TAINT};
		1109
		1110	$VERBOSE = $ENV{PERL_ANYEVENT_VERBOSE}*1;
		1111
		1112	}
		1113
		1114	our $MAX_SIGNAL_LATENCY = 10;
		1115
		1116	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		1117
		1118	{
		1119	my $idx;
		1120	$PROTOCOL{$_} = ++$idx
		1121	for reverse split /\s*,\s*/,
		1122	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		1123	}
		1124
437	my @models = (	1125	my @models = (
438	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
439	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
440	[EV:: => AnyEvent::Impl::EV::],	1126	[EV:: => AnyEvent::Impl::EV:: , 1],
441	[Event:: => AnyEvent::Impl::Event::],	1127	[Event:: => AnyEvent::Impl::Event::, 1],
442	[Glib:: => AnyEvent::Impl::Glib::],
443	[Tk:: => AnyEvent::Impl::Tk::],
444	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1128	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl:: , 1],
		1129	# everything below here will not (normally) be autoprobed
		1130	# as the pureperl backend should work everywhere
		1131	# and is usually faster
		1132	[Glib:: => AnyEvent::Impl::Glib:: , 1], # becomes extremely slow with many watchers
		1133	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		1134	[Irssi:: => AnyEvent::Impl::Irssi::], # Irssi has a bogus "Event" package
		1135	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		1136	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		1137	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
		1138	[Wx:: => AnyEvent::Impl::POE::],
		1139	[Prima:: => AnyEvent::Impl::POE::],
		1140	# IO::Async is just too broken - we would need workarounds for its
		1141	# byzantine signal and broken child handling, among others.
		1142	# IO::Async is rather hard to detect, as it doesn't have any
		1143	# obvious default class.
		1144	# [0, IO::Async:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1145	# [0, IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1146	# [0, IO::Async::Notifier:: => AnyEvent::Impl::IOAsync::], # requires special main program
445	);	1147	);
446	my @models_detect = (
447	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
448	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
449	);
450		1148
451	our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);	1149	our %method = map +($_ => 1),
		1150	qw(io timer time now now_update signal child idle condvar one_event DESTROY);
		1151
		1152	our @post_detect;
		1153
		1154	sub post_detect(&) {
		1155	my ($cb) = @_;
		1156
		1157	if ($MODEL) {
		1158	$cb->();
		1159
		1160	undef
		1161	} else {
		1162	push @post_detect, $cb;
		1163
		1164	defined wantarray
		1165	? bless \$cb, "AnyEvent::Util::postdetect"
		1166	: ()
		1167	}
		1168	}
		1169
		1170	sub AnyEvent::Util::postdetect::DESTROY {
		1171	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		1172	}
452		1173
453	sub detect() {	1174	sub detect() {
454	unless ($MODEL) {	1175	unless ($MODEL) {
455	no strict 'refs';	1176	local $SIG{__DIE__};
456		1177
457	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	1178	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
458	my $model = "AnyEvent::Impl::$1";	1179	my $model = "AnyEvent::Impl::$1";
459	if (eval "require $model") {	1180	if (eval "require $model") {
460	$MODEL = $model;	1181	$MODEL = $model;
461	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	1182	warn "AnyEvent: loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.\n" if $VERBOSE >= 2;
		1183	} else {
		1184	warn "AnyEvent: unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@" if $VERBOSE;
462	}	1185	}
463	}	1186	}
464		1187
465	# check for already loaded models	1188	# check for already loaded models
466	unless ($MODEL) {	1189	unless ($MODEL) {
467	for (@REGISTRY, @models, @models_detect) {	1190	for (@REGISTRY, @models) {
468	my ($package, $model) = @$_;	1191	my ($package, $model) = @$_;
469	if (${"$package\::VERSION"} > 0) {	1192	if (${"$package\::VERSION"} > 0) {
470	if (eval "require $model") {	1193	if (eval "require $model") {
471	$MODEL = $model;	1194	$MODEL = $model;
472	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;	1195	warn "AnyEvent: autodetected model '$model', using it.\n" if $VERBOSE >= 2;
473	last;	1196	last;
474	}	1197	}
475	}	1198	}
476	}	1199	}
477		1200
478	unless ($MODEL) {	1201	unless ($MODEL) {
479	# try to load a model	1202	# try to autoload a model
480
481	for (@REGISTRY, @models) {	1203	for (@REGISTRY, @models) {
482	my ($package, $model) = @$_;	1204	my ($package, $model, $autoload) = @$_;
		1205	if (
		1206	$autoload
483	if (eval "require $package"	1207	and eval "require $package"
484	and ${"$package\::VERSION"} > 0	1208	and ${"$package\::VERSION"} > 0
485	and eval "require $model") {	1209	and eval "require $model"
		1210	) {
486	$MODEL = $model;	1211	$MODEL = $model;
487	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;	1212	warn "AnyEvent: autoloaded model '$model', using it.\n" if $VERBOSE >= 2;
488	last;	1213	last;
489	}	1214	}
490	}	1215	}
491		1216
492	$MODEL	1217	$MODEL
493	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV (or Coro+EV), Event (or Coro+Event) or Glib.";	1218	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.\n";
494	}	1219	}
495	}	1220	}
496		1221
		1222	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		1223
497	unshift @ISA, $MODEL;	1224	unshift @ISA, $MODEL;
498	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	1225
		1226	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
		1227
		1228	(shift @post_detect)->() while @post_detect;
499	}	1229	}
500		1230
501	$MODEL	1231	$MODEL
502	}	1232	}
503		1233
504	sub AUTOLOAD {	1234	sub AUTOLOAD {
505	(my $func = $AUTOLOAD) =~ s/.*://;	1235	(my $func = $AUTOLOAD) =~ s/.*://;
506		1236
507	$method{$func}	1237	$method{$func}
508	or croak "$func: not a valid method for AnyEvent objects";	1238	or Carp::croak "$func: not a valid method for AnyEvent objects";
509		1239
510	detect unless $MODEL;	1240	detect unless $MODEL;
511		1241
512	my $class = shift;	1242	my $class = shift;
513	$class->$func (@_);	1243	$class->$func (@_);
514	}	1244	}
515		1245
		1246	# utility function to dup a filehandle. this is used by many backends
		1247	# to support binding more than one watcher per filehandle (they usually
		1248	# allow only one watcher per fd, so we dup it to get a different one).
		1249	sub _dupfh($$;$$) {
		1250	my ($poll, $fh, $r, $w) = @_;
		1251
		1252	# cygwin requires the fh mode to be matching, unix doesn't
		1253	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1254
		1255	open my $fh2, $mode, $fh
		1256	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1257
		1258	# we assume CLOEXEC is already set by perl in all important cases
		1259
		1260	($fh2, $rw)
		1261	}
		1262
516	package AnyEvent::Base;	1263	package AnyEvent::Base;
517		1264
		1265	# default implementations for many methods
		1266
		1267	sub _time {
		1268	# probe for availability of Time::HiRes
		1269	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1270	warn "AnyEvent: using Time::HiRes for sub-second timing accuracy.\n" if $VERBOSE >= 8;
		1271	*_time = \&Time::HiRes::time;
		1272	# if (eval "use POSIX (); (POSIX::times())...
		1273	} else {
		1274	warn "AnyEvent: using built-in time(), WARNING, no sub-second resolution!\n" if $VERBOSE;
		1275	*_time = sub { time }; # epic fail
		1276	}
		1277
		1278	&_time
		1279	}
		1280
		1281	sub time { _time }
		1282	sub now { _time }
		1283	sub now_update { }
		1284
518	# default implementation for ->condvar, ->wait, ->broadcast	1285	# default implementation for ->condvar
519		1286
520	sub condvar {	1287	sub condvar {
521	bless \my $flag, "AnyEvent::Base::CondVar"	1288	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
522	}
523
524	sub AnyEvent::Base::CondVar::broadcast {
525	${$_[0]}++;
526	}
527
528	sub AnyEvent::Base::CondVar::wait {
529	AnyEvent->one_event while !${$_[0]};
530	}	1289	}
531		1290
532	# default implementation for ->signal	1291	# default implementation for ->signal
533		1292
534	our %SIG_CB;	1293	our $HAVE_ASYNC_INTERRUPT;
		1294
		1295	sub _have_async_interrupt() {
		1296	$HAVE_ASYNC_INTERRUPT = 1*(!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT}
		1297	&& eval "use Async::Interrupt 1.0 (); 1")
		1298	unless defined $HAVE_ASYNC_INTERRUPT;
		1299
		1300	$HAVE_ASYNC_INTERRUPT
		1301	}
		1302
		1303	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1304	our (%SIG_ASY, %SIG_ASY_W);
		1305	our ($SIG_COUNT, $SIG_TW);
		1306
		1307	sub _signal_exec {
		1308	$HAVE_ASYNC_INTERRUPT
		1309	? $SIGPIPE_R->drain
		1310	: sysread $SIGPIPE_R, my $dummy, 9;
		1311
		1312	while (%SIG_EV) {
		1313	for (keys %SIG_EV) {
		1314	delete $SIG_EV{$_};
		1315	$_->() for values %{ $SIG_CB{$_} || {} };
		1316	}
		1317	}
		1318	}
		1319
		1320	# install a dummy wakeup watcher to reduce signal catching latency
		1321	sub _sig_add() {
		1322	unless ($SIG_COUNT++) {
		1323	# try to align timer on a full-second boundary, if possible
		1324	my $NOW = AnyEvent->now;
		1325
		1326	$SIG_TW = AnyEvent->timer (
		1327	after => $MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1328	interval => $MAX_SIGNAL_LATENCY,
		1329	cb => sub { }, # just for the PERL_ASYNC_CHECK
		1330	);
		1331	}
		1332	}
		1333
		1334	sub _sig_del {
		1335	undef $SIG_TW
		1336	unless --$SIG_COUNT;
		1337	}
		1338
		1339	our $_sig_name_init; $_sig_name_init = sub {
		1340	eval q{ # poor man's autoloading
		1341	undef $_sig_name_init;
		1342
		1343	if (_have_async_interrupt) {
		1344	*sig2num = \&Async::Interrupt::sig2num;
		1345	*sig2name = \&Async::Interrupt::sig2name;
		1346	} else {
		1347	require Config;
		1348
		1349	my %signame2num;
		1350	@signame2num{ split ' ', $Config::Config{sig_name} }
		1351	= split ' ', $Config::Config{sig_num};
		1352
		1353	my @signum2name;
		1354	@signum2name[values %signame2num] = keys %signame2num;
		1355
		1356	*sig2num = sub($) {
		1357	$_[0] > 0 ? shift : $signame2num{+shift}
		1358	};
		1359	*sig2name = sub ($) {
		1360	$_[0] > 0 ? $signum2name[+shift] : shift
		1361	};
		1362	}
		1363	};
		1364	die if $@;
		1365	};
		1366
		1367	sub sig2num ($) { &$_sig_name_init; &sig2num }
		1368	sub sig2name($) { &$_sig_name_init; &sig2name }
535		1369
536	sub signal {	1370	sub signal {
		1371	eval q{ # poor man's autoloading {}
		1372	# probe for availability of Async::Interrupt
		1373	if (_have_async_interrupt) {
		1374	warn "AnyEvent: using Async::Interrupt for race-free signal handling.\n" if $VERBOSE >= 8;
		1375
		1376	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1377	$SIG_IO = AnyEvent->io (fh => $SIGPIPE_R->fileno, poll => "r", cb => \&_signal_exec);
		1378
		1379	} else {
		1380	warn "AnyEvent: using emulated perl signal handling with latency timer.\n" if $VERBOSE >= 8;
		1381
		1382	require Fcntl;
		1383
		1384	if (AnyEvent::WIN32) {
		1385	require AnyEvent::Util;
		1386
		1387	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1388	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R, 1) if $SIGPIPE_R;
		1389	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W, 1) if $SIGPIPE_W; # just in case
		1390	} else {
		1391	pipe $SIGPIPE_R, $SIGPIPE_W;
		1392	fcntl $SIGPIPE_R, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_R;
		1393	fcntl $SIGPIPE_W, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_W; # just in case
		1394
		1395	# not strictly required, as $^F is normally 2, but let's make sure...
		1396	fcntl $SIGPIPE_R, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1397	fcntl $SIGPIPE_W, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1398	}
		1399
		1400	$SIGPIPE_R
		1401	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1402
		1403	$SIG_IO = AnyEvent->io (fh => $SIGPIPE_R, poll => "r", cb => \&_signal_exec);
		1404	}
		1405
		1406	*signal = sub {
537	my (undef, %arg) = @_;	1407	my (undef, %arg) = @_;
538		1408
539	my $signal = uc $arg{signal}	1409	my $signal = uc $arg{signal}
540	or Carp::croak "required option 'signal' is missing";	1410	or Carp::croak "required option 'signal' is missing";
541		1411
		1412	if ($HAVE_ASYNC_INTERRUPT) {
		1413	# async::interrupt
		1414
		1415	$signal = sig2num $signal;
542	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1416	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1417
		1418	$SIG_ASY{$signal} ||= new Async::Interrupt
		1419	cb => sub { undef $SIG_EV{$signal} },
		1420	signal => $signal,
		1421	pipe => [$SIGPIPE_R->filenos],
		1422	pipe_autodrain => 0,
		1423	;
		1424
		1425	} else {
		1426	# pure perl
		1427
		1428	# AE::Util has been loaded in signal
		1429	$signal = sig2name $signal;
		1430	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1431
543	$SIG{$signal} ||= sub {	1432	$SIG{$signal} ||= sub {
544	$_->() for values %{ $SIG_CB{$signal} || {} };	1433	local $!;
		1434	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1435	undef $SIG_EV{$signal};
		1436	};
		1437
		1438	# can't do signal processing without introducing races in pure perl,
		1439	# so limit the signal latency.
		1440	_sig_add;
		1441	}
		1442
		1443	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1444	};
		1445
		1446	*AnyEvent::Base::signal::DESTROY = sub {
		1447	my ($signal, $cb) = @{$_[0]};
		1448
		1449	_sig_del;
		1450
		1451	delete $SIG_CB{$signal}{$cb};
		1452
		1453	$HAVE_ASYNC_INTERRUPT
		1454	? delete $SIG_ASY{$signal}
		1455	: # delete doesn't work with older perls - they then
		1456	# print weird messages, or just unconditionally exit
		1457	# instead of getting the default action.
		1458	undef $SIG{$signal}
		1459	unless keys %{ $SIG_CB{$signal} };
		1460	};
545	};	1461	};
546		1462	die if $@;
547	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1463	&signal
548	}
549
550	sub AnyEvent::Base::Signal::DESTROY {
551	my ($signal, $cb) = @{$_[0]};
552
553	delete $SIG_CB{$signal}{$cb};
554
555	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };
556	}	1464	}
557		1465
558	# default implementation for ->child	1466	# default implementation for ->child
559		1467
560	our %PID_CB;	1468	our %PID_CB;
561	our $CHLD_W;	1469	our $CHLD_W;
562	our $CHLD_DELAY_W;	1470	our $CHLD_DELAY_W;
563	our $PID_IDLE;
564	our $WNOHANG;	1471	our $WNOHANG;
565		1472
566	sub _child_wait {	1473	sub _emit_childstatus($$) {
567	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1474	my (undef, $rpid, $rstatus) = @_;
		1475
		1476	$_->($rpid, $rstatus)
568	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1477	for values %{ $PID_CB{$rpid} || {} },
569	(values %{ $PID_CB{0} || {} });	1478	values %{ $PID_CB{0} || {} };
570	}
571
572	undef $PID_IDLE;
573	}	1479	}
574		1480
575	sub _sigchld {	1481	sub _sigchld {
576	# make sure we deliver these changes "synchronous" with the event loop.	1482	my $pid;
577	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {	1483
578	undef $CHLD_DELAY_W;	1484	AnyEvent->_emit_childstatus ($pid, $?)
579	&_child_wait;	1485	while ($pid = waitpid -1, $WNOHANG) > 0;
580	});
581	}	1486	}
582		1487
583	sub child {	1488	sub child {
584	my (undef, %arg) = @_;	1489	my (undef, %arg) = @_;
585		1490
586	defined (my $pid = $arg{pid} + 0)	1491	defined (my $pid = $arg{pid} + 0)
587	or Carp::croak "required option 'pid' is missing";	1492	or Carp::croak "required option 'pid' is missing";
588		1493
589	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1494	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
590		1495
591	unless ($WNOHANG) {	1496	# WNOHANG is almost cetrainly 1 everywhere
592	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;	1497	$WNOHANG ||= $^O =~ /^(?:openbsd|netbsd|linux|freebsd|cygwin|MSWin32)$/
593	}	1498	? 1
		1499	: eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
594		1500
595	unless ($CHLD_W) {	1501	unless ($CHLD_W) {
596	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1502	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
597	# child could be a zombie already, so make at least one round	1503	# child could be a zombie already, so make at least one round
598	&_sigchld;	1504	&_sigchld;
599	}	1505	}
600		1506
601	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	1507	bless [$pid, $arg{cb}], "AnyEvent::Base::child"
602	}	1508	}
603		1509
604	sub AnyEvent::Base::Child::DESTROY {	1510	sub AnyEvent::Base::child::DESTROY {
605	my ($pid, $cb) = @{$_[0]};	1511	my ($pid, $cb) = @{$_[0]};
606		1512
607	delete $PID_CB{$pid}{$cb};	1513	delete $PID_CB{$pid}{$cb};
608	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1514	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
609		1515
610	undef $CHLD_W unless keys %PID_CB;	1516	undef $CHLD_W unless keys %PID_CB;
611	}	1517	}
		1518
		1519	# idle emulation is done by simply using a timer, regardless
		1520	# of whether the process is idle or not, and not letting
		1521	# the callback use more than 50% of the time.
		1522	sub idle {
		1523	my (undef, %arg) = @_;
		1524
		1525	my ($cb, $w, $rcb) = $arg{cb};
		1526
		1527	$rcb = sub {
		1528	if ($cb) {
		1529	$w = _time;
		1530	&$cb;
		1531	$w = _time - $w;
		1532
		1533	# never use more then 50% of the time for the idle watcher,
		1534	# within some limits
		1535	$w = 0.0001 if $w < 0.0001;
		1536	$w = 5 if $w > 5;
		1537
		1538	$w = AnyEvent->timer (after => $w, cb => $rcb);
		1539	} else {
		1540	# clean up...
		1541	undef $w;
		1542	undef $rcb;
		1543	}
		1544	};
		1545
		1546	$w = AnyEvent->timer (after => 0.05, cb => $rcb);
		1547
		1548	bless \\$cb, "AnyEvent::Base::idle"
		1549	}
		1550
		1551	sub AnyEvent::Base::idle::DESTROY {
		1552	undef $${$_[0]};
		1553	}
		1554
		1555	package AnyEvent::CondVar;
		1556
		1557	our @ISA = AnyEvent::CondVar::Base::;
		1558
		1559	package AnyEvent::CondVar::Base;
		1560
		1561	#use overload
		1562	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1563	# fallback => 1;
		1564
		1565	# save 300+ kilobytes by dirtily hardcoding overloading
		1566	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1567	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1568	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1569	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1570
		1571	our $WAITING;
		1572
		1573	sub _send {
		1574	# nop
		1575	}
		1576
		1577	sub send {
		1578	my $cv = shift;
		1579	$cv->{_ae_sent} = [@_];
		1580	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1581	$cv->_send;
		1582	}
		1583
		1584	sub croak {
		1585	$_[0]{_ae_croak} = $_[1];
		1586	$_[0]->send;
		1587	}
		1588
		1589	sub ready {
		1590	$_[0]{_ae_sent}
		1591	}
		1592
		1593	sub _wait {
		1594	$WAITING
		1595	and !$_[0]{_ae_sent}
		1596	and Carp::croak "AnyEvent::CondVar: recursive blocking wait detected";
		1597
		1598	local $WAITING = 1;
		1599	AnyEvent->one_event while !$_[0]{_ae_sent};
		1600	}
		1601
		1602	sub recv {
		1603	$_[0]->_wait;
		1604
		1605	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
		1606	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
		1607	}
		1608
		1609	sub cb {
		1610	$_[0]{_ae_cb} = $_[1] if @_ > 1;
		1611	$_[0]{_ae_cb}
		1612	}
		1613
		1614	sub begin {
		1615	++$_[0]{_ae_counter};
		1616	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
		1617	}
		1618
		1619	sub end {
		1620	return if --$_[0]{_ae_counter};
		1621	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		1622	}
		1623
		1624	# undocumented/compatibility with pre-3.4
		1625	*broadcast = \&send;
		1626	*wait = \&_wait;
		1627
		1628	=head1 ERROR AND EXCEPTION HANDLING
		1629
		1630	In general, AnyEvent does not do any error handling - it relies on the
		1631	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1632	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1633	checking of all AnyEvent methods, however, which is highly useful during
		1634	development.
		1635
		1636	As for exception handling (i.e. runtime errors and exceptions thrown while
		1637	executing a callback), this is not only highly event-loop specific, but
		1638	also not in any way wrapped by this module, as this is the job of the main
		1639	program.
		1640
		1641	The pure perl event loop simply re-throws the exception (usually
		1642	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1643	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1644	so on.
		1645
		1646	=head1 ENVIRONMENT VARIABLES
		1647
		1648	The following environment variables are used by this module or its
		1649	submodules.
		1650
		1651	Note that AnyEvent will remove I<all> environment variables starting with
		1652	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		1653	enabled.
		1654
		1655	=over 4
		1656
		1657	=item C<PERL_ANYEVENT_VERBOSE>
		1658
		1659	By default, AnyEvent will be completely silent except in fatal
		1660	conditions. You can set this environment variable to make AnyEvent more
		1661	talkative.
		1662
		1663	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1664	conditions, such as not being able to load the event model specified by
		1665	C<PERL_ANYEVENT_MODEL>.
		1666
		1667	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1668	model it chooses.
		1669
		1670	When set to C<8> or higher, then AnyEvent will report extra information on
		1671	which optional modules it loads and how it implements certain features.
		1672
		1673	=item C<PERL_ANYEVENT_STRICT>
		1674
		1675	AnyEvent does not do much argument checking by default, as thorough
		1676	argument checking is very costly. Setting this variable to a true value
		1677	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1678	check the arguments passed to most method calls. If it finds any problems,
		1679	it will croak.
		1680
		1681	In other words, enables "strict" mode.
		1682
		1683	Unlike C<use strict> (or it's modern cousin, C<< use L<common::sense>
		1684	>>, it is definitely recommended to keep it off in production. Keeping
		1685	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		1686	can be very useful, however.
		1687
		1688	=item C<PERL_ANYEVENT_MODEL>
		1689
		1690	This can be used to specify the event model to be used by AnyEvent, before
		1691	auto detection and -probing kicks in. It must be a string consisting
		1692	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1693	and the resulting module name is loaded and if the load was successful,
		1694	used as event model. If it fails to load AnyEvent will proceed with
		1695	auto detection and -probing.
		1696
		1697	This functionality might change in future versions.
		1698
		1699	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1700	could start your program like this:
		1701
		1702	PERL_ANYEVENT_MODEL=Perl perl ...
		1703
		1704	=item C<PERL_ANYEVENT_PROTOCOLS>
		1705
		1706	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1707	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1708	of auto probing).
		1709
		1710	Must be set to a comma-separated list of protocols or address families,
		1711	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1712	used, and preference will be given to protocols mentioned earlier in the
		1713	list.
		1714
		1715	This variable can effectively be used for denial-of-service attacks
		1716	against local programs (e.g. when setuid), although the impact is likely
		1717	small, as the program has to handle conenction and other failures anyways.
		1718
		1719	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1720	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1721	- only support IPv4, never try to resolve or contact IPv6
		1722	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1723	IPv6, but prefer IPv6 over IPv4.
		1724
		1725	=item C<PERL_ANYEVENT_EDNS0>
		1726
		1727	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1728	for DNS. This extension is generally useful to reduce DNS traffic, but
		1729	some (broken) firewalls drop such DNS packets, which is why it is off by
		1730	default.
		1731
		1732	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1733	EDNS0 in its DNS requests.
		1734
		1735	=item C<PERL_ANYEVENT_MAX_FORKS>
		1736
		1737	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1738	will create in parallel.
		1739
		1740	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		1741
		1742	The default value for the C<max_outstanding> parameter for the default DNS
		1743	resolver - this is the maximum number of parallel DNS requests that are
		1744	sent to the DNS server.
		1745
		1746	=item C<PERL_ANYEVENT_RESOLV_CONF>
		1747
		1748	The file to use instead of F</etc/resolv.conf> (or OS-specific
		1749	configuration) in the default resolver. When set to the empty string, no
		1750	default config will be used.
		1751
		1752	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		1753
		1754	When neither C<ca_file> nor C<ca_path> was specified during
		1755	L<AnyEvent::TLS> context creation, and either of these environment
		1756	variables exist, they will be used to specify CA certificate locations
		1757	instead of a system-dependent default.
		1758
		1759	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		1760
		1761	When these are set to C<1>, then the respective modules are not
		1762	loaded. Mostly good for testing AnyEvent itself.
		1763
		1764	=back
612		1765
613	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1766	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
614		1767
615	This is an advanced topic that you do not normally need to use AnyEvent in	1768	This is an advanced topic that you do not normally need to use AnyEvent in
616	a module. This section is only of use to event loop authors who want to	1769	a module. This section is only of use to event loop authors who want to
…		…
651	I<rxvt-unicode> also cheats a bit by not providing blocking access to	1804	I<rxvt-unicode> also cheats a bit by not providing blocking access to
652	condition variables: code blocking while waiting for a condition will	1805	condition variables: code blocking while waiting for a condition will
653	C<die>. This still works with most modules/usages, and blocking calls must	1806	C<die>. This still works with most modules/usages, and blocking calls must
654	not be done in an interactive application, so it makes sense.	1807	not be done in an interactive application, so it makes sense.
655		1808
656	=head1 ENVIRONMENT VARIABLES
657
658	The following environment variables are used by this module:
659
660	=over 4
661
662	=item C<PERL_ANYEVENT_VERBOSE>
663
664	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
665	model it chooses.
666
667	=item C<PERL_ANYEVENT_MODEL>
668
669	This can be used to specify the event model to be used by AnyEvent, before
670	autodetection and -probing kicks in. It must be a string consisting
671	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
672	and the resulting module name is loaded and if the load was successful,
673	used as event model. If it fails to load AnyEvent will proceed with
674	autodetection and -probing.
675
676	This functionality might change in future versions.
677
678	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
679	could start your program like this:
680
681	PERL_ANYEVENT_MODEL=Perl perl ...
682
683	=back
684
685	=head1 EXAMPLE PROGRAM	1809	=head1 EXAMPLE PROGRAM
686		1810
687	The following program uses an IO watcher to read data from STDIN, a timer	1811	The following program uses an I/O watcher to read data from STDIN, a timer
688	to display a message once per second, and a condition variable to quit the	1812	to display a message once per second, and a condition variable to quit the
689	program when the user enters quit:	1813	program when the user enters quit:
690		1814
691	use AnyEvent;	1815	use AnyEvent;
692		1816
…		…
697	poll => 'r',	1821	poll => 'r',
698	cb => sub {	1822	cb => sub {
699	warn "io event <$_[0]>\n"; # will always output <r>	1823	warn "io event <$_[0]>\n"; # will always output <r>
700	chomp (my $input = <STDIN>); # read a line	1824	chomp (my $input = <STDIN>); # read a line
701	warn "read: $input\n"; # output what has been read	1825	warn "read: $input\n"; # output what has been read
702	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	1826	$cv->send if $input =~ /^q/i; # quit program if /^q/i
703	},	1827	},
704	);	1828	);
705		1829
706	my $time_watcher; # can only be used once	1830	my $time_watcher; # can only be used once
707		1831
…		…
712	});	1836	});
713	}	1837	}
714		1838
715	new_timer; # create first timer	1839	new_timer; # create first timer
716		1840
717	$cv->wait; # wait until user enters /^q/i	1841	$cv->recv; # wait until user enters /^q/i
718		1842
719	=head1 REAL-WORLD EXAMPLE	1843	=head1 REAL-WORLD EXAMPLE
720		1844
721	Consider the L<Net::FCP> module. It features (among others) the following	1845	Consider the L<Net::FCP> module. It features (among others) the following
722	API calls, which are to freenet what HTTP GET requests are to http:	1846	API calls, which are to freenet what HTTP GET requests are to http:
…		…
772	syswrite $txn->{fh}, $txn->{request}	1896	syswrite $txn->{fh}, $txn->{request}
773	or die "connection or write error";	1897	or die "connection or write error";
774	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	1898	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
775		1899
776	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	1900	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
777	result and signals any possible waiters that the request ahs finished:	1901	result and signals any possible waiters that the request has finished:
778		1902
779	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	1903	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
780		1904
781	if (end-of-file or data complete) {	1905	if (end-of-file or data complete) {
782	$txn->{result} = $txn->{buf};	1906	$txn->{result} = $txn->{buf};
783	$txn->{finished}->broadcast;	1907	$txn->{finished}->send;
784	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	1908	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
785	}	1909	}
786		1910
787	The C<result> method, finally, just waits for the finished signal (if the	1911	The C<result> method, finally, just waits for the finished signal (if the
788	request was already finished, it doesn't wait, of course, and returns the	1912	request was already finished, it doesn't wait, of course, and returns the
789	data:	1913	data:
790		1914
791	$txn->{finished}->wait;	1915	$txn->{finished}->recv;
792	return $txn->{result};	1916	return $txn->{result};
793		1917
794	The actual code goes further and collects all errors (C<die>s, exceptions)	1918	The actual code goes further and collects all errors (C<die>s, exceptions)
795	that occured during request processing. The C<result> method detects	1919	that occurred during request processing. The C<result> method detects
796	whether an exception as thrown (it is stored inside the $txn object)	1920	whether an exception as thrown (it is stored inside the $txn object)
797	and just throws the exception, which means connection errors and other	1921	and just throws the exception, which means connection errors and other
798	problems get reported tot he code that tries to use the result, not in a	1922	problems get reported tot he code that tries to use the result, not in a
799	random callback.	1923	random callback.
800		1924
…		…
831		1955
832	my $quit = AnyEvent->condvar;	1956	my $quit = AnyEvent->condvar;
833		1957
834	$fcp->txn_client_get ($url)->cb (sub {	1958	$fcp->txn_client_get ($url)->cb (sub {
835	...	1959	...
836	$quit->broadcast;	1960	$quit->send;
837	});	1961	});
838		1962
839	$quit->wait;	1963	$quit->recv;
		1964
		1965
		1966	=head1 BENCHMARKS
		1967
		1968	To give you an idea of the performance and overheads that AnyEvent adds
		1969	over the event loops themselves and to give you an impression of the speed
		1970	of various event loops I prepared some benchmarks.
		1971
		1972	=head2 BENCHMARKING ANYEVENT OVERHEAD
		1973
		1974	Here is a benchmark of various supported event models used natively and
		1975	through AnyEvent. The benchmark creates a lot of timers (with a zero
		1976	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
		1977	which it is), lets them fire exactly once and destroys them again.
		1978
		1979	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
		1980	distribution.
		1981
		1982	=head3 Explanation of the columns
		1983
		1984	I<watcher> is the number of event watchers created/destroyed. Since
		1985	different event models feature vastly different performances, each event
		1986	loop was given a number of watchers so that overall runtime is acceptable
		1987	and similar between tested event loop (and keep them from crashing): Glib
		1988	would probably take thousands of years if asked to process the same number
		1989	of watchers as EV in this benchmark.
		1990
		1991	I<bytes> is the number of bytes (as measured by the resident set size,
		1992	RSS) consumed by each watcher. This method of measuring captures both C
		1993	and Perl-based overheads.
		1994
		1995	I<create> is the time, in microseconds (millionths of seconds), that it
		1996	takes to create a single watcher. The callback is a closure shared between
		1997	all watchers, to avoid adding memory overhead. That means closure creation
		1998	and memory usage is not included in the figures.
		1999
		2000	I<invoke> is the time, in microseconds, used to invoke a simple
		2001	callback. The callback simply counts down a Perl variable and after it was
		2002	invoked "watcher" times, it would C<< ->send >> a condvar once to
		2003	signal the end of this phase.
		2004
		2005	I<destroy> is the time, in microseconds, that it takes to destroy a single
		2006	watcher.
		2007
		2008	=head3 Results
		2009
		2010	name watchers bytes create invoke destroy comment
		2011	EV/EV 400000 224 0.47 0.35 0.27 EV native interface
		2012	EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers
		2013	CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal
		2014	Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation
		2015	Event/Event 16000 517 32.20 31.80 0.81 Event native interface
		2016	Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers
		2017	IOAsync/Any 16000 989 38.10 32.77 11.13 via IO::Async::Loop::IO_Poll
		2018	IOAsync/Any 16000 990 37.59 29.50 10.61 via IO::Async::Loop::Epoll
		2019	Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour
		2020	Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers
		2021	POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event
		2022	POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select
		2023
		2024	=head3 Discussion
		2025
		2026	The benchmark does I<not> measure scalability of the event loop very
		2027	well. For example, a select-based event loop (such as the pure perl one)
		2028	can never compete with an event loop that uses epoll when the number of
		2029	file descriptors grows high. In this benchmark, all events become ready at
		2030	the same time, so select/poll-based implementations get an unnatural speed
		2031	boost.
		2032
		2033	Also, note that the number of watchers usually has a nonlinear effect on
		2034	overall speed, that is, creating twice as many watchers doesn't take twice
		2035	the time - usually it takes longer. This puts event loops tested with a
		2036	higher number of watchers at a disadvantage.
		2037
		2038	To put the range of results into perspective, consider that on the
		2039	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		2040	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		2041	cycles with POE.
		2042
		2043	C<EV> is the sole leader regarding speed and memory use, which are both
		2044	maximal/minimal, respectively. Even when going through AnyEvent, it uses
		2045	far less memory than any other event loop and is still faster than Event
		2046	natively.
		2047
		2048	The pure perl implementation is hit in a few sweet spots (both the
		2049	constant timeout and the use of a single fd hit optimisations in the perl
		2050	interpreter and the backend itself). Nevertheless this shows that it
		2051	adds very little overhead in itself. Like any select-based backend its
		2052	performance becomes really bad with lots of file descriptors (and few of
		2053	them active), of course, but this was not subject of this benchmark.
		2054
		2055	The C<Event> module has a relatively high setup and callback invocation
		2056	cost, but overall scores in on the third place.
		2057
		2058	C<IO::Async> performs admirably well, about on par with C<Event>, even
		2059	when using its pure perl backend.
		2060
		2061	C<Glib>'s memory usage is quite a bit higher, but it features a
		2062	faster callback invocation and overall ends up in the same class as
		2063	C<Event>. However, Glib scales extremely badly, doubling the number of
		2064	watchers increases the processing time by more than a factor of four,
		2065	making it completely unusable when using larger numbers of watchers
		2066	(note that only a single file descriptor was used in the benchmark, so
		2067	inefficiencies of C<poll> do not account for this).
		2068
		2069	The C<Tk> adaptor works relatively well. The fact that it crashes with
		2070	more than 2000 watchers is a big setback, however, as correctness takes
		2071	precedence over speed. Nevertheless, its performance is surprising, as the
		2072	file descriptor is dup()ed for each watcher. This shows that the dup()
		2073	employed by some adaptors is not a big performance issue (it does incur a
		2074	hidden memory cost inside the kernel which is not reflected in the figures
		2075	above).
		2076
		2077	C<POE>, regardless of underlying event loop (whether using its pure perl
		2078	select-based backend or the Event module, the POE-EV backend couldn't
		2079	be tested because it wasn't working) shows abysmal performance and
		2080	memory usage with AnyEvent: Watchers use almost 30 times as much memory
		2081	as EV watchers, and 10 times as much memory as Event (the high memory
		2082	requirements are caused by requiring a session for each watcher). Watcher
		2083	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		2084	implementation.
		2085
		2086	The design of the POE adaptor class in AnyEvent can not really account
		2087	for the performance issues, though, as session creation overhead is
		2088	small compared to execution of the state machine, which is coded pretty
		2089	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		2090	using multiple sessions is not a good approach, especially regarding
		2091	memory usage, even the author of POE could not come up with a faster
		2092	design).
		2093
		2094	=head3 Summary
		2095
		2096	=over 4
		2097
		2098	=item * Using EV through AnyEvent is faster than any other event loop
		2099	(even when used without AnyEvent), but most event loops have acceptable
		2100	performance with or without AnyEvent.
		2101
		2102	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
		2103	the actual event loop, only with extremely fast event loops such as EV
		2104	adds AnyEvent significant overhead.
		2105
		2106	=item * You should avoid POE like the plague if you want performance or
		2107	reasonable memory usage.
		2108
		2109	=back
		2110
		2111	=head2 BENCHMARKING THE LARGE SERVER CASE
		2112
		2113	This benchmark actually benchmarks the event loop itself. It works by
		2114	creating a number of "servers": each server consists of a socket pair, a
		2115	timeout watcher that gets reset on activity (but never fires), and an I/O
		2116	watcher waiting for input on one side of the socket. Each time the socket
		2117	watcher reads a byte it will write that byte to a random other "server".
		2118
		2119	The effect is that there will be a lot of I/O watchers, only part of which
		2120	are active at any one point (so there is a constant number of active
		2121	fds for each loop iteration, but which fds these are is random). The
		2122	timeout is reset each time something is read because that reflects how
		2123	most timeouts work (and puts extra pressure on the event loops).
		2124
		2125	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
		2126	(1%) are active. This mirrors the activity of large servers with many
		2127	connections, most of which are idle at any one point in time.
		2128
		2129	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		2130	distribution.
		2131
		2132	=head3 Explanation of the columns
		2133
		2134	I<sockets> is the number of sockets, and twice the number of "servers" (as
		2135	each server has a read and write socket end).
		2136
		2137	I<create> is the time it takes to create a socket pair (which is
		2138	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		2139
		2140	I<request>, the most important value, is the time it takes to handle a
		2141	single "request", that is, reading the token from the pipe and forwarding
		2142	it to another server. This includes deleting the old timeout and creating
		2143	a new one that moves the timeout into the future.
		2144
		2145	=head3 Results
		2146
		2147	name sockets create request
		2148	EV 20000 69.01 11.16
		2149	Perl 20000 73.32 35.87
		2150	IOAsync 20000 157.00 98.14 epoll
		2151	IOAsync 20000 159.31 616.06 poll
		2152	Event 20000 212.62 257.32
		2153	Glib 20000 651.16 1896.30
		2154	POE 20000 349.67 12317.24 uses POE::Loop::Event
		2155
		2156	=head3 Discussion
		2157
		2158	This benchmark I<does> measure scalability and overall performance of the
		2159	particular event loop.
		2160
		2161	EV is again fastest. Since it is using epoll on my system, the setup time
		2162	is relatively high, though.
		2163
		2164	Perl surprisingly comes second. It is much faster than the C-based event
		2165	loops Event and Glib.
		2166
		2167	IO::Async performs very well when using its epoll backend, and still quite
		2168	good compared to Glib when using its pure perl backend.
		2169
		2170	Event suffers from high setup time as well (look at its code and you will
		2171	understand why). Callback invocation also has a high overhead compared to
		2172	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		2173	uses select or poll in basically all documented configurations.
		2174
		2175	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		2176	clearly fails to perform with many filehandles or in busy servers.
		2177
		2178	POE is still completely out of the picture, taking over 1000 times as long
		2179	as EV, and over 100 times as long as the Perl implementation, even though
		2180	it uses a C-based event loop in this case.
		2181
		2182	=head3 Summary
		2183
		2184	=over 4
		2185
		2186	=item * The pure perl implementation performs extremely well.
		2187
		2188	=item * Avoid Glib or POE in large projects where performance matters.
		2189
		2190	=back
		2191
		2192	=head2 BENCHMARKING SMALL SERVERS
		2193
		2194	While event loops should scale (and select-based ones do not...) even to
		2195	large servers, most programs we (or I :) actually write have only a few
		2196	I/O watchers.
		2197
		2198	In this benchmark, I use the same benchmark program as in the large server
		2199	case, but it uses only eight "servers", of which three are active at any
		2200	one time. This should reflect performance for a small server relatively
		2201	well.
		2202
		2203	The columns are identical to the previous table.
		2204
		2205	=head3 Results
		2206
		2207	name sockets create request
		2208	EV 16 20.00 6.54
		2209	Perl 16 25.75 12.62
		2210	Event 16 81.27 35.86
		2211	Glib 16 32.63 15.48
		2212	POE 16 261.87 276.28 uses POE::Loop::Event
		2213
		2214	=head3 Discussion
		2215
		2216	The benchmark tries to test the performance of a typical small
		2217	server. While knowing how various event loops perform is interesting, keep
		2218	in mind that their overhead in this case is usually not as important, due
		2219	to the small absolute number of watchers (that is, you need efficiency and
		2220	speed most when you have lots of watchers, not when you only have a few of
		2221	them).
		2222
		2223	EV is again fastest.
		2224
		2225	Perl again comes second. It is noticeably faster than the C-based event
		2226	loops Event and Glib, although the difference is too small to really
		2227	matter.
		2228
		2229	POE also performs much better in this case, but is is still far behind the
		2230	others.
		2231
		2232	=head3 Summary
		2233
		2234	=over 4
		2235
		2236	=item * C-based event loops perform very well with small number of
		2237	watchers, as the management overhead dominates.
		2238
		2239	=back
		2240
		2241	=head2 THE IO::Lambda BENCHMARK
		2242
		2243	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2244	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2245	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2246	shouldn't come as a surprise to anybody). As such, the benchmark is
		2247	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2248	very optimal. But how would AnyEvent compare when used without the extra
		2249	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2250
		2251	The benchmark itself creates an echo-server, and then, for 500 times,
		2252	connects to the echo server, sends a line, waits for the reply, and then
		2253	creates the next connection. This is a rather bad benchmark, as it doesn't
		2254	test the efficiency of the framework or much non-blocking I/O, but it is a
		2255	benchmark nevertheless.
		2256
		2257	name runtime
		2258	Lambda/select 0.330 sec
		2259	+ optimized 0.122 sec
		2260	Lambda/AnyEvent 0.327 sec
		2261	+ optimized 0.138 sec
		2262	Raw sockets/select 0.077 sec
		2263	POE/select, components 0.662 sec
		2264	POE/select, raw sockets 0.226 sec
		2265	POE/select, optimized 0.404 sec
		2266
		2267	AnyEvent/select/nb 0.085 sec
		2268	AnyEvent/EV/nb 0.068 sec
		2269	+state machine 0.134 sec
		2270
		2271	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2272	benchmarks actually make blocking connects and use 100% blocking I/O,
		2273	defeating the purpose of an event-based solution. All of the newly
		2274	written AnyEvent benchmarks use 100% non-blocking connects (using
		2275	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2276	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2277	generally require a lot more bookkeeping and event handling than blocking
		2278	connects (which involve a single syscall only).
		2279
		2280	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2281	offers similar expressive power as POE and IO::Lambda, using conventional
		2282	Perl syntax. This means that both the echo server and the client are 100%
		2283	non-blocking, further placing it at a disadvantage.
		2284
		2285	As you can see, the AnyEvent + EV combination even beats the
		2286	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2287	backend easily beats IO::Lambda and POE.
		2288
		2289	And even the 100% non-blocking version written using the high-level (and
		2290	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda by a
		2291	large margin, even though it does all of DNS, tcp-connect and socket I/O
		2292	in a non-blocking way.
		2293
		2294	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2295	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2296	part of the IO::lambda distribution and were used without any changes.
		2297
		2298
		2299	=head1 SIGNALS
		2300
		2301	AnyEvent currently installs handlers for these signals:
		2302
		2303	=over 4
		2304
		2305	=item SIGCHLD
		2306
		2307	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2308	emulation for event loops that do not support them natively. Also, some
		2309	event loops install a similar handler.
		2310
		2311	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2312	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2313
		2314	=item SIGPIPE
		2315
		2316	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2317	when AnyEvent gets loaded.
		2318
		2319	The rationale for this is that AnyEvent users usually do not really depend
		2320	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2321	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2322	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2323	some random socket.
		2324
		2325	The rationale for installing a no-op handler as opposed to ignoring it is
		2326	that this way, the handler will be restored to defaults on exec.
		2327
		2328	Feel free to install your own handler, or reset it to defaults.
		2329
		2330	=back
		2331
		2332	=cut
		2333
		2334	undef $SIG{CHLD}
		2335	if $SIG{CHLD} eq 'IGNORE';
		2336
		2337	$SIG{PIPE} = sub { }
		2338	unless defined $SIG{PIPE};
		2339
		2340	=head1 RECOMMENDED/OPTIONAL MODULES
		2341
		2342	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2343	it's built-in modules) are required to use it.
		2344
		2345	That does not mean that AnyEvent won't take advantage of some additional
		2346	modules if they are installed.
		2347
		2348	This section epxlains which additional modules will be used, and how they
		2349	affect AnyEvent's operetion.
		2350
		2351	=over 4
		2352
		2353	=item L<Async::Interrupt>
		2354
		2355	This slightly arcane module is used to implement fast signal handling: To
		2356	my knowledge, there is no way to do completely race-free and quick
		2357	signal handling in pure perl. To ensure that signals still get
		2358	delivered, AnyEvent will start an interval timer to wake up perl (and
		2359	catch the signals) with some delay (default is 10 seconds, look for
		2360	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2361
		2362	If this module is available, then it will be used to implement signal
		2363	catching, which means that signals will not be delayed, and the event loop
		2364	will not be interrupted regularly, which is more efficient (And good for
		2365	battery life on laptops).
		2366
		2367	This affects not just the pure-perl event loop, but also other event loops
		2368	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2369
		2370	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2371	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2372	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2373	does nothing for those backends.
		2374
		2375	=item L<EV>
		2376
		2377	This module isn't really "optional", as it is simply one of the backend
		2378	event loops that AnyEvent can use. However, it is simply the best event
		2379	loop available in terms of features, speed and stability: It supports
		2380	the AnyEvent API optimally, implements all the watcher types in XS, does
		2381	automatic timer adjustments even when no monotonic clock is available,
		2382	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2383	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2384	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2385
		2386	=item L<Guard>
		2387
		2388	The guard module, when used, will be used to implement
		2389	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2390	lot less memory), but otherwise doesn't affect guard operation much. It is
		2391	purely used for performance.
		2392
		2393	=item L<JSON> and L<JSON::XS>
		2394
		2395	This module is required when you want to read or write JSON data via
		2396	L<AnyEvent::Handle>. It is also written in pure-perl, but can take
		2397	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2398
		2399	In fact, L<AnyEvent::Handle> will use L<JSON::XS> by default if it is
		2400	installed.
		2401
		2402	=item L<Net::SSLeay>
		2403
		2404	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2405	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2406	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2407
		2408	=item L<Time::HiRes>
		2409
		2410	This module is part of perl since release 5.008. It will be used when the
		2411	chosen event library does not come with a timing source on it's own. The
		2412	pure-perl event loop (L<AnyEvent::Impl::Perl>) will additionally use it to
		2413	try to use a monotonic clock for timing stability.
		2414
		2415	=back
		2416
840		2417
841	=head1 FORK	2418	=head1 FORK
842		2419
843	Most event libraries are not fork-safe. The ones who are usually are	2420	Most event libraries are not fork-safe. The ones who are usually are
844	because they are so inefficient. Only L<EV> is fully fork-aware.	2421	because they rely on inefficient but fork-safe C<select> or C<poll>
		2422	calls. Only L<EV> is fully fork-aware.
845		2423
846	If you have to fork, you must either do so I<before> creating your first	2424	If you have to fork, you must either do so I<before> creating your first
847	watcher OR you must not use AnyEvent at all in the child.	2425	watcher OR you must not use AnyEvent at all in the child OR you must do
		2426	something completely out of the scope of AnyEvent.
		2427
848		2428
849	=head1 SECURITY CONSIDERATIONS	2429	=head1 SECURITY CONSIDERATIONS
850		2430
851	AnyEvent can be forced to load any event model via	2431	AnyEvent can be forced to load any event model via
852	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to	2432	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
…		…
856	specified in the variable.	2436	specified in the variable.
857		2437
858	You can make AnyEvent completely ignore this variable by deleting it	2438	You can make AnyEvent completely ignore this variable by deleting it
859	before the first watcher gets created, e.g. with a C<BEGIN> block:	2439	before the first watcher gets created, e.g. with a C<BEGIN> block:
860		2440
861	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	2441	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
862		2442
863	use AnyEvent;	2443	use AnyEvent;
		2444
		2445	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		2446	be used to probe what backend is used and gain other information (which is
		2447	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2448	$ENV{PERL_ANYEVENT_STRICT}.
		2449
		2450	Note that AnyEvent will remove I<all> environment variables starting with
		2451	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2452	enabled.
		2453
		2454
		2455	=head1 BUGS
		2456
		2457	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2458	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2459	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2460	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2461	pronounced).
		2462
864		2463
865	=head1 SEE ALSO	2464	=head1 SEE ALSO
866		2465
867	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	2466	Utility functions: L<AnyEvent::Util>.
868	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,
869	L<Event::Lib>, L<Qt>.
870		2467
871	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	2468	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
		2469	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
		2470
		2471	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
		2472	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
		2473	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
872	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,	2474	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>, L<Anyevent::Impl::Irssi>.
873	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,
874	L<AnyEvent::Impl::Qt>.
875		2475
		2476	Non-blocking file handles, sockets, TCP clients and
		2477	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
		2478
		2479	Asynchronous DNS: L<AnyEvent::DNS>.
		2480
		2481	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>,
		2482	L<Coro::Event>,
		2483
876	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	2484	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::XMPP>,
		2485	L<AnyEvent::HTTP>.
		2486
877		2487
878	=head1 AUTHOR	2488	=head1 AUTHOR
879		2489
880	Marc Lehmann <schmorp@schmorp.de>	2490	Marc Lehmann <schmorp@schmorp.de>
881	http://home.schmorp.de/	2491	http://home.schmorp.de/
882		2492
883	=cut	2493	=cut
884		2494
885	1	2495	1
886		2496

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