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Revision 1.53 by root, Sat Apr 19 04:58:14 2008 UTC vs.
Revision 1.318 by root, Wed Mar 24 23:28:06 2010 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 - 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	# if you prefer function calls, look at the L<AE> manpage for
		13	# an alternative API.
		14
		15	# file handle or descriptor readable
11	my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub {	16	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
		17
		18	# one-shot or repeating timers
		19	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
		20	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...
		21
		22	print AnyEvent->now; # prints current event loop time
		23	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
		24
		25	# POSIX signal
		26	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
		27
		28	# child process exit
		29	my $w = AnyEvent->child (pid => $pid, cb => sub {
		30	my ($pid, $status) = @_;
12	...	31	...
13	});	32	});
14		33
15	my $w = AnyEvent->timer (after => $seconds, cb => sub {	34	# called when event loop idle (if applicable)
16	...	35	my $w = AnyEvent->idle (cb => sub { ... });
17	});
18		36
19	my $w = AnyEvent->condvar; # stores whether a condition was flagged	37	my $w = AnyEvent->condvar; # stores whether a condition was flagged
		38	$w->send; # wake up current and all future recv's
20	$w->wait; # enters "main loop" till $condvar gets ->broadcast	39	$w->recv; # enters "main loop" till $condvar gets ->send
21	$w->broadcast; # wake up current and all future wait's	40	# use a condvar in callback mode:
		41	$w->cb (sub { $_[0]->recv });
		42
		43	=head1 INTRODUCTION/TUTORIAL
		44
		45	This manpage is mainly a reference manual. If you are interested
		46	in a tutorial or some gentle introduction, have a look at the
		47	L<AnyEvent::Intro> manpage.
		48
		49	=head1 SUPPORT
		50
		51	There is a mailinglist for discussing all things AnyEvent, and an IRC
		52	channel, too.
		53
		54	See the AnyEvent project page at the B<Schmorpforge Ta-Sa Software
		55	Repository>, at L<http://anyevent.schmorp.de>, for more info.
22		56
23	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)	57	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
24		58
25	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	59	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
26	nowadays. So what is different about AnyEvent?	60	nowadays. So what is different about AnyEvent?
27		61
28	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of	62	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
29	policy> and AnyEvent is I<small and efficient>.	63	policy> and AnyEvent is I<small and efficient>.
30		64
31	First and foremost, I<AnyEvent is not an event model> itself, it only	65	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	66	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,	67	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,	68	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	69	only one event loop can be active at the same time in a process. AnyEvent
36	helps hiding the differences between those event loops.	70	cannot change this, but it can hide the differences between those event
		71	loops.
37		72
38	The goal of AnyEvent is to offer module authors the ability to do event	73	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	74	programming (waiting for I/O or timer events) without subscribing to a
40	religion, a way of living, and most importantly: without forcing your	75	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	76	module users into the same thing by forcing them to use the same event
42	model you use.	77	model you use.
43		78
44	For modules like POE or IO::Async (which is a total misnomer as it is	79	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	80	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	81	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	82	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	83	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.	84	module are I<also> forced to use the same event loop you use.
50		85
51	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	86	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
52	fine. AnyEvent + Tk works fine etc. etc. but none of these work together	87	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	88	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,	89	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	90	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	91	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	92	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).	93	to AnyEvent, too, so it is future-proof).
59		94
60	In addition to being free of having to use I<the one and only true event	95	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	96	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	97	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	98	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	99	offering the functionality that is necessary, in as thin as a wrapper as
65	technically possible.	100	technically possible.
66		101
		102	Of course, AnyEvent comes with a big (and fully optional!) toolbox
		103	of useful functionality, such as an asynchronous DNS resolver, 100%
		104	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
		105	such as Windows) and lots of real-world knowledge and workarounds for
		106	platform bugs and differences.
		107
67	Of course, if you want lots of policy (this can arguably be somewhat	108	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	109	useful) and you want to force your users to use the one and only event
69	model, you should I<not> use this module.	110	model, you should I<not> use this module.
70
71		111
72	=head1 DESCRIPTION	112	=head1 DESCRIPTION
73		113
74	L<AnyEvent> provides an identical interface to multiple event loops. This	114	L<AnyEvent> provides an identical interface to multiple event loops. This
75	allows module authors to utilise an event loop without forcing module	115	allows module authors to utilise an event loop without forcing module
…		…
79	The interface itself is vaguely similar, but not identical to the L<Event>	119	The interface itself is vaguely similar, but not identical to the L<Event>
80	module.	120	module.
81		121
82	During the first call of any watcher-creation method, the module tries	122	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 the	123	to detect the currently loaded event loop by probing whether one of the
84	following modules is already loaded: L<Coro::EV>, L<Coro::Event>, L<EV>,	124	following modules is already loaded: L<EV>,
85	L<Event>, L<Glib>, L<Tk>. The first one found is used. If none are found,	125	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,
86	the module tries to load these modules in the stated order. The first one	126	L<POE>. The first one found is used. If none are found, the module tries
		127	to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl
		128	adaptor should always succeed) in the order given. The first one that can
87	that can be successfully loaded will be used. If, after this, still none	129	be successfully loaded will be used. If, after this, still none could be
88	could be found, AnyEvent will fall back to a pure-perl event loop, which	130	found, AnyEvent will fall back to a pure-perl event loop, which is not
89	is not very efficient, but should work everywhere.	131	very efficient, but should work everywhere.
90		132
91	Because AnyEvent first checks for modules that are already loaded, loading	133	Because AnyEvent first checks for modules that are already loaded, loading
92	an event model explicitly before first using AnyEvent will likely make	134	an event model explicitly before first using AnyEvent will likely make
93	that model the default. For example:	135	that model the default. For example:
94		136
…		…
101	starts using it, all bets are off. Maybe you should tell their authors to	143	starts using it, all bets are off. Maybe you should tell their authors to
102	use AnyEvent so their modules work together with others seamlessly...	144	use AnyEvent so their modules work together with others seamlessly...
103		145
104	The pure-perl implementation of AnyEvent is called	146	The pure-perl implementation of AnyEvent is called
105	C<AnyEvent::Impl::Perl>. Like other event modules you can load it	147	C<AnyEvent::Impl::Perl>. Like other event modules you can load it
106	explicitly.	148	explicitly and enjoy the high availability of that event loop :)
107		149
108	=head1 WATCHERS	150	=head1 WATCHERS
109		151
110	AnyEvent has the central concept of a I<watcher>, which is an object that	152	AnyEvent has the central concept of a I<watcher>, which is an object that
111	stores relevant data for each kind of event you are waiting for, such as	153	stores relevant data for each kind of event you are waiting for, such as
112	the callback to call, the filehandle to watch, etc.	154	the callback to call, the file handle to watch, etc.
113		155
114	These watchers are normal Perl objects with normal Perl lifetime. After	156	These watchers are normal Perl objects with normal Perl lifetime. After
115	creating a watcher it will immediately "watch" for events and invoke the	157	creating a watcher it will immediately "watch" for events and invoke the
116	callback when the event occurs (of course, only when the event model	158	callback when the event occurs (of course, only when the event model
117	is in control).	159	is in control).
118		160
		161	Note that B<callbacks must not permanently change global variables>
		162	potentially in use by the event loop (such as C<$_> or C<$[>) and that B<<
		163	callbacks must not C<die> >>. The former is good programming practise in
		164	Perl and the latter stems from the fact that exception handling differs
		165	widely between event loops.
		166
119	To disable the watcher you have to destroy it (e.g. by setting the	167	To disable the watcher you have to destroy it (e.g. by setting the
120	variable you store it in to C<undef> or otherwise deleting all references	168	variable you store it in to C<undef> or otherwise deleting all references
121	to it).	169	to it).
122		170
123	All watchers are created by calling a method on the C<AnyEvent> class.	171	All watchers are created by calling a method on the C<AnyEvent> class.
…		…
125	Many watchers either are used with "recursion" (repeating timers for	173	Many watchers either are used with "recursion" (repeating timers for
126	example), or need to refer to their watcher object in other ways.	174	example), or need to refer to their watcher object in other ways.
127		175
128	An any way to achieve that is this pattern:	176	An any way to achieve that is this pattern:
129		177
130	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	178	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
131	# you can use $w here, for example to undef it	179	# you can use $w here, for example to undef it
132	undef $w;	180	undef $w;
133	});	181	});
134		182
135	Note that C<my $w; $w => combination. This is necessary because in Perl,	183	Note that C<my $w; $w => combination. This is necessary because in Perl,
136	my variables are only visible after the statement in which they are	184	my variables are only visible after the statement in which they are
137	declared.	185	declared.
138		186
139	=head2 IO WATCHERS	187	=head2 I/O WATCHERS
		188
		189	$w = AnyEvent->io (
		190	fh => <filehandle_or_fileno>,
		191	poll => <"r" or "w">,
		192	cb => <callback>,
		193	);
140		194
141	You can create an I/O watcher by calling the C<< AnyEvent->io >> method	195	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
142	with the following mandatory key-value pairs as arguments:	196	with the following mandatory key-value pairs as arguments:
143		197
144	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch for	198	C<fh> is the Perl I<file handle> (or a naked file descriptor) to watch
		199	for events (AnyEvent might or might not keep a reference to this file
		200	handle). Note that only file handles pointing to things for which
		201	non-blocking operation makes sense are allowed. This includes sockets,
		202	most character devices, pipes, fifos and so on, but not for example files
		203	or block devices.
		204
145	events. C<poll> must be a string that is either C<r> or C<w>, which	205	C<poll> must be a string that is either C<r> or C<w>, which creates a
146	creates a watcher waiting for "r"eadable or "w"ritable events,	206	watcher waiting for "r"eadable or "w"ritable events, respectively.
		207
147	respectively. C<cb> is the callback to invoke each time the file handle	208	C<cb> is the callback to invoke each time the file handle becomes ready.
148	becomes ready.
149		209
150	File handles will be kept alive, so as long as the watcher exists, the	210	Although the callback might get passed parameters, their value and
151	file handle exists, too.	211	presence is undefined and you cannot rely on them. Portable AnyEvent
		212	callbacks cannot use arguments passed to I/O watcher callbacks.
152		213
		214	The I/O watcher might use the underlying file descriptor or a copy of it.
153	It is not allowed to close a file handle as long as any watcher is active	215	You must not close a file handle as long as any watcher is active on the
154	on the underlying file descriptor.	216	underlying file descriptor.
155		217
156	Some event loops issue spurious readyness notifications, so you should	218	Some event loops issue spurious readyness notifications, so you should
157	always use non-blocking calls when reading/writing from/to your file	219	always use non-blocking calls when reading/writing from/to your file
158	handles.	220	handles.
159		221
160	Example:
161
162	# wait for readability of STDIN, then read a line and disable the watcher	222	Example: wait for readability of STDIN, then read a line and disable the
		223	watcher.
		224
163	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	225	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
164	chomp (my $input = <STDIN>);	226	chomp (my $input = <STDIN>);
165	warn "read: $input\n";	227	warn "read: $input\n";
166	undef $w;	228	undef $w;
167	});	229	});
168		230
169	=head2 TIME WATCHERS	231	=head2 TIME WATCHERS
170		232
		233	$w = AnyEvent->timer (after => <seconds>, cb => <callback>);
		234
		235	$w = AnyEvent->timer (
		236	after => <fractional_seconds>,
		237	interval => <fractional_seconds>,
		238	cb => <callback>,
		239	);
		240
171	You can create a time watcher by calling the C<< AnyEvent->timer >>	241	You can create a time watcher by calling the C<< AnyEvent->timer >>
172	method with the following mandatory arguments:	242	method with the following mandatory arguments:
173		243
174	C<after> specifies after how many seconds (fractional values are	244	C<after> specifies after how many seconds (fractional values are
175	supported) should the timer activate. C<cb> the callback to invoke in that	245	supported) the callback should be invoked. C<cb> is the callback to invoke
176	case.	246	in that case.
177		247
178	The timer callback will be invoked at most once: if you want a repeating	248	Although the callback might get passed parameters, their value and
179	timer you have to create a new watcher (this is a limitation by both Tk	249	presence is undefined and you cannot rely on them. Portable AnyEvent
180	and Glib).	250	callbacks cannot use arguments passed to time watcher callbacks.
181		251
182	Example:	252	The callback will normally be invoked once only. If you specify another
		253	parameter, C<interval>, as a strictly positive number (> 0), then the
		254	callback will be invoked regularly at that interval (in fractional
		255	seconds) after the first invocation. If C<interval> is specified with a
		256	false value, then it is treated as if it were missing.
183		257
		258	The callback will be rescheduled before invoking the callback, but no
		259	attempt is done to avoid timer drift in most backends, so the interval is
		260	only approximate.
		261
184	# fire an event after 7.7 seconds	262	Example: fire an event after 7.7 seconds.
		263
185	my $w = AnyEvent->timer (after => 7.7, cb => sub {	264	my $w = AnyEvent->timer (after => 7.7, cb => sub {
186	warn "timeout\n";	265	warn "timeout\n";
187	});	266	});
188		267
189	# to cancel the timer:	268	# to cancel the timer:
190	undef $w;	269	undef $w;
191		270
192	Example 2:
193
194	# fire an event after 0.5 seconds, then roughly every second	271	Example 2: fire an event after 0.5 seconds, then roughly every second.
195	my $w;
196		272
197	my $cb = sub {
198	# cancel the old timer while creating a new one
199	$w = AnyEvent->timer (after => 1, cb => $cb);	273	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		274	warn "timeout\n";
200	};	275	};
201
202	# start the "loop" by creating the first watcher
203	$w = AnyEvent->timer (after => 0.5, cb => $cb);
204		276
205	=head3 TIMING ISSUES	277	=head3 TIMING ISSUES
206		278
207	There are two ways to handle timers: based on real time (relative, "fire	279	There are two ways to handle timers: based on real time (relative, "fire
208	in 10 seconds") and based on wallclock time (absolute, "fire at 12	280	in 10 seconds") and based on wallclock time (absolute, "fire at 12
209	o'clock").	281	o'clock").
210		282
211	While most event loops expect timers to specified in a relative way, they use	283	While most event loops expect timers to specified in a relative way, they
212	absolute time internally. This makes a difference when your clock "jumps",	284	use absolute time internally. This makes a difference when your clock
213	for example, when ntp decides to set your clock backwards from the wrong 2014-01-01 to	285	"jumps", for example, when ntp decides to set your clock backwards from
214	2008-01-01, a watcher that you created to fire "after" a second might actually take	286	the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to
215	six years to finally fire.	287	fire "after" a second might actually take six years to finally fire.
216		288
217	AnyEvent cannot compensate for this. The only event loop that is conscious	289	AnyEvent cannot compensate for this. The only event loop that is conscious
218	about these issues is L<EV>, which offers both relative (ev_timer) and	290	about these issues is L<EV>, which offers both relative (ev_timer, based
219	absolute (ev_periodic) timers.	291	on true relative time) and absolute (ev_periodic, based on wallclock time)
		292	timers.
220		293
221	AnyEvent always prefers relative timers, if available, matching the	294	AnyEvent always prefers relative timers, if available, matching the
222	AnyEvent API.	295	AnyEvent API.
223		296
		297	AnyEvent has two additional methods that return the "current time":
		298
		299	=over 4
		300
		301	=item AnyEvent->time
		302
		303	This returns the "current wallclock time" as a fractional number of
		304	seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
		305	return, and the result is guaranteed to be compatible with those).
		306
		307	It progresses independently of any event loop processing, i.e. each call
		308	will check the system clock, which usually gets updated frequently.
		309
		310	=item AnyEvent->now
		311
		312	This also returns the "current wallclock time", but unlike C<time>, above,
		313	this value might change only once per event loop iteration, depending on
		314	the event loop (most return the same time as C<time>, above). This is the
		315	time that AnyEvent's timers get scheduled against.
		316
		317	I<In almost all cases (in all cases if you don't care), this is the
		318	function to call when you want to know the current time.>
		319
		320	This function is also often faster then C<< AnyEvent->time >>, and
		321	thus the preferred method if you want some timestamp (for example,
		322	L<AnyEvent::Handle> uses this to update it's activity timeouts).
		323
		324	The rest of this section is only of relevance if you try to be very exact
		325	with your timing, you can skip it without bad conscience.
		326
		327	For a practical example of when these times differ, consider L<Event::Lib>
		328	and L<EV> and the following set-up:
		329
		330	The event loop is running and has just invoked one of your callback at
		331	time=500 (assume no other callbacks delay processing). In your callback,
		332	you wait a second by executing C<sleep 1> (blocking the process for a
		333	second) and then (at time=501) you create a relative timer that fires
		334	after three seconds.
		335
		336	With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
		337	both return C<501>, because that is the current time, and the timer will
		338	be scheduled to fire at time=504 (C<501> + C<3>).
		339
		340	With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
		341	time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
		342	last event processing phase started. With L<EV>, your timer gets scheduled
		343	to run at time=503 (C<500> + C<3>).
		344
		345	In one sense, L<Event::Lib> is more exact, as it uses the current time
		346	regardless of any delays introduced by event processing. However, most
		347	callbacks do not expect large delays in processing, so this causes a
		348	higher drift (and a lot more system calls to get the current time).
		349
		350	In another sense, L<EV> is more exact, as your timer will be scheduled at
		351	the same time, regardless of how long event processing actually took.
		352
		353	In either case, if you care (and in most cases, you don't), then you
		354	can get whatever behaviour you want with any event loop, by taking the
		355	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
		356	account.
		357
		358	=item AnyEvent->now_update
		359
		360	Some event loops (such as L<EV> or L<AnyEvent::Impl::Perl>) cache
		361	the current time for each loop iteration (see the discussion of L<<
		362	AnyEvent->now >>, above).
		363
		364	When a callback runs for a long time (or when the process sleeps), then
		365	this "current" time will differ substantially from the real time, which
		366	might affect timers and time-outs.
		367
		368	When this is the case, you can call this method, which will update the
		369	event loop's idea of "current time".
		370
		371	A typical example would be a script in a web server (e.g. C<mod_perl>) -
		372	when mod_perl executes the script, then the event loop will have the wrong
		373	idea about the "current time" (being potentially far in the past, when the
		374	script ran the last time). In that case you should arrange a call to C<<
		375	AnyEvent->now_update >> each time the web server process wakes up again
		376	(e.g. at the start of your script, or in a handler).
		377
		378	Note that updating the time I<might> cause some events to be handled.
		379
		380	=back
		381
224	=head2 SIGNAL WATCHERS	382	=head2 SIGNAL WATCHERS
225		383
		384	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		385
226	You can watch for signals using a signal watcher, C<signal> is the signal	386	You can watch for signals using a signal watcher, C<signal> is the signal
227	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to	387	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
228	be invoked whenever a signal occurs.	388	callback to be invoked whenever a signal occurs.
229		389
		390	Although the callback might get passed parameters, their value and
		391	presence is undefined and you cannot rely on them. Portable AnyEvent
		392	callbacks cannot use arguments passed to signal watcher callbacks.
		393
230	Multiple signals occurances can be clumped together into one callback	394	Multiple signal occurrences can be clumped together into one callback
231	invocation, and callback invocation will be synchronous. synchronous means	395	invocation, and callback invocation will be synchronous. Synchronous means
232	that it might take a while until the signal gets handled by the process,	396	that it might take a while until the signal gets handled by the process,
233	but it is guarenteed not to interrupt any other callbacks.	397	but it is guaranteed not to interrupt any other callbacks.
234		398
235	The main advantage of using these watchers is that you can share a signal	399	The main advantage of using these watchers is that you can share a signal
236	between multiple watchers.	400	between multiple watchers, and AnyEvent will ensure that signals will not
		401	interrupt your program at bad times.
237		402
238	This watcher might use C<%SIG>, so programs overwriting those signals	403	This watcher might use C<%SIG> (depending on the event loop used),
239	directly will likely not work correctly.	404	so programs overwriting those signals directly will likely not work
		405	correctly.
240		406
241	Example: exit on SIGINT	407	Example: exit on SIGINT
242		408
243	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	409	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
244		410
		411	=head3 Restart Behaviour
		412
		413	While restart behaviour is up to the event loop implementation, most will
		414	not restart syscalls (that includes L<Async::Interrupt> and AnyEvent's
		415	pure perl implementation).
		416
		417	=head3 Safe/Unsafe Signals
		418
		419	Perl signals can be either "safe" (synchronous to opcode handling) or
		420	"unsafe" (asynchronous) - the former might get delayed indefinitely, the
		421	latter might corrupt your memory.
		422
		423	AnyEvent signal handlers are, in addition, synchronous to the event loop,
		424	i.e. they will not interrupt your running perl program but will only be
		425	called as part of the normal event handling (just like timer, I/O etc.
		426	callbacks, too).
		427
		428	=head3 Signal Races, Delays and Workarounds
		429
		430	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		431	callbacks to signals in a generic way, which is a pity, as you cannot
		432	do race-free signal handling in perl, requiring C libraries for
		433	this. AnyEvent will try to do it's best, which means in some cases,
		434	signals will be delayed. The maximum time a signal might be delayed is
		435	specified in C<$AnyEvent::MAX_SIGNAL_LATENCY> (default: 10 seconds). This
		436	variable can be changed only before the first signal watcher is created,
		437	and should be left alone otherwise. This variable determines how often
		438	AnyEvent polls for signals (in case a wake-up was missed). Higher values
		439	will cause fewer spurious wake-ups, which is better for power and CPU
		440	saving.
		441
		442	All these problems can be avoided by installing the optional
		443	L<Async::Interrupt> module, which works with most event loops. It will not
		444	work with inherently broken event loops such as L<Event> or L<Event::Lib>
		445	(and not with L<POE> currently, as POE does it's own workaround with
		446	one-second latency). For those, you just have to suffer the delays.
		447
245	=head2 CHILD PROCESS WATCHERS	448	=head2 CHILD PROCESS WATCHERS
246		449
		450	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		451
247	You can also watch on a child process exit and catch its exit status.	452	You can also watch on a child process exit and catch its exit status.
248		453
249	The child process is specified by the C<pid> argument (if set to C<0>, it	454	The child process is specified by the C<pid> argument (one some backends,
250	watches for any child process exit). The watcher will trigger as often	455	using C<0> watches for any child process exit, on others this will
251	as status change for the child are received. This works by installing a	456	croak). The watcher will be triggered only when the child process has
252	signal handler for C<SIGCHLD>. The callback will be called with the pid	457	finished and an exit status is available, not on any trace events
253	and exit status (as returned by waitpid).	458	(stopped/continued).
254		459
255	Example: wait for pid 1333	460	The callback will be called with the pid and exit status (as returned by
		461	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		462	callback arguments.
256		463
		464	This watcher type works by installing a signal handler for C<SIGCHLD>,
		465	and since it cannot be shared, nothing else should use SIGCHLD or reap
		466	random child processes (waiting for specific child processes, e.g. inside
		467	C<system>, is just fine).
		468
		469	There is a slight catch to child watchers, however: you usually start them
		470	I<after> the child process was created, and this means the process could
		471	have exited already (and no SIGCHLD will be sent anymore).
		472
		473	Not all event models handle this correctly (neither POE nor IO::Async do,
		474	see their AnyEvent::Impl manpages for details), but even for event models
		475	that I<do> handle this correctly, they usually need to be loaded before
		476	the process exits (i.e. before you fork in the first place). AnyEvent's
		477	pure perl event loop handles all cases correctly regardless of when you
		478	start the watcher.
		479
		480	This means you cannot create a child watcher as the very first
		481	thing in an AnyEvent program, you I<have> to create at least one
		482	watcher before you C<fork> the child (alternatively, you can call
		483	C<AnyEvent::detect>).
		484
		485	As most event loops do not support waiting for child events, they will be
		486	emulated by AnyEvent in most cases, in which the latency and race problems
		487	mentioned in the description of signal watchers apply.
		488
		489	Example: fork a process and wait for it
		490
		491	my $done = AnyEvent->condvar;
		492
		493	my $pid = fork or exit 5;
		494
257	my $w = AnyEvent->child (	495	my $w = AnyEvent->child (
258	pid => 1333,	496	pid => $pid,
259	cb => sub {	497	cb => sub {
260	my ($pid, $status) = @_;	498	my ($pid, $status) = @_;
261	warn "pid $pid exited with status $status";	499	warn "pid $pid exited with status $status";
		500	$done->send;
262	},	501	},
263	);	502	);
		503
		504	# do something else, then wait for process exit
		505	$done->recv;
		506
		507	=head2 IDLE WATCHERS
		508
		509	$w = AnyEvent->idle (cb => <callback>);
		510
		511	Repeatedly invoke the callback after the process becomes idle, until
		512	either the watcher is destroyed or new events have been detected.
		513
		514	Idle watchers are useful when there is a need to do something, but it
		515	is not so important (or wise) to do it instantly. The callback will be
		516	invoked only when there is "nothing better to do", which is usually
		517	defined as "all outstanding events have been handled and no new events
		518	have been detected". That means that idle watchers ideally get invoked
		519	when the event loop has just polled for new events but none have been
		520	detected. Instead of blocking to wait for more events, the idle watchers
		521	will be invoked.
		522
		523	Unfortunately, most event loops do not really support idle watchers (only
		524	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		525	will simply call the callback "from time to time".
		526
		527	Example: read lines from STDIN, but only process them when the
		528	program is otherwise idle:
		529
		530	my @lines; # read data
		531	my $idle_w;
		532	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		533	push @lines, scalar <STDIN>;
		534
		535	# start an idle watcher, if not already done
		536	$idle_w ||= AnyEvent->idle (cb => sub {
		537	# handle only one line, when there are lines left
		538	if (my $line = shift @lines) {
		539	print "handled when idle: $line";
		540	} else {
		541	# otherwise disable the idle watcher again
		542	undef $idle_w;
		543	}
		544	});
		545	});
264		546
265	=head2 CONDITION VARIABLES	547	=head2 CONDITION VARIABLES
266		548
		549	$cv = AnyEvent->condvar;
		550
		551	$cv->send (<list>);
		552	my @res = $cv->recv;
		553
		554	If you are familiar with some event loops you will know that all of them
		555	require you to run some blocking "loop", "run" or similar function that
		556	will actively watch for new events and call your callbacks.
		557
		558	AnyEvent is slightly different: it expects somebody else to run the event
		559	loop and will only block when necessary (usually when told by the user).
		560
		561	The instrument to do that is called a "condition variable", so called
		562	because they represent a condition that must become true.
		563
		564	Now is probably a good time to look at the examples further below.
		565
267	Condition variables can be created by calling the C<< AnyEvent->condvar >>	566	Condition variables can be created by calling the C<< AnyEvent->condvar
268	method without any arguments.	567	>> method, usually without arguments. The only argument pair allowed is
		568	C<cb>, which specifies a callback to be called when the condition variable
		569	becomes true, with the condition variable as the first argument (but not
		570	the results).
269		571
270	A condition variable waits for a condition - precisely that the C<<	572	After creation, the condition variable is "false" until it becomes "true"
271	->broadcast >> method has been called.	573	by calling the C<send> method (or calling the condition variable as if it
		574	were a callback, read about the caveats in the description for the C<<
		575	->send >> method).
272		576
273	They are very useful to signal that a condition has been fulfilled, for	577	Condition variables are similar to callbacks, except that you can
		578	optionally wait for them. They can also be called merge points - points
		579	in time where multiple outstanding events have been processed. And yet
		580	another way to call them is transactions - each condition variable can be
		581	used to represent a transaction, which finishes at some point and delivers
		582	a result. And yet some people know them as "futures" - a promise to
		583	compute/deliver something that you can wait for.
		584
		585	Condition variables are very useful to signal that something has finished,
274	example, if you write a module that does asynchronous http requests,	586	for example, if you write a module that does asynchronous http requests,
275	then a condition variable would be the ideal candidate to signal the	587	then a condition variable would be the ideal candidate to signal the
276	availability of results.	588	availability of results. The user can either act when the callback is
		589	called or can synchronously C<< ->recv >> for the results.
277		590
278	You can also use condition variables to block your main program until	591	You can also use them to simulate traditional event loops - for example,
279	an event occurs - for example, you could C<< ->wait >> in your main	592	you can block your main program until an event occurs - for example, you
280	program until the user clicks the Quit button in your app, which would C<<	593	could C<< ->recv >> in your main program until the user clicks the Quit
281	->broadcast >> the "quit" event.	594	button of your app, which would C<< ->send >> the "quit" event.
282		595
283	Note that condition variables recurse into the event loop - if you have	596	Note that condition variables recurse into the event loop - if you have
284	two pirces of code that call C<< ->wait >> in a round-robbin fashion, you	597	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
285	lose. Therefore, condition variables are good to export to your caller, but	598	lose. Therefore, condition variables are good to export to your caller, but
286	you should avoid making a blocking wait yourself, at least in callbacks,	599	you should avoid making a blocking wait yourself, at least in callbacks,
287	as this asks for trouble.	600	as this asks for trouble.
288		601
289	This object has two methods:	602	Condition variables are represented by hash refs in perl, and the keys
		603	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
		604	easy (it is often useful to build your own transaction class on top of
		605	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
		606	it's C<new> method in your own C<new> method.
290		607
291	=over 4	608	There are two "sides" to a condition variable - the "producer side" which
		609	eventually calls C<< -> send >>, and the "consumer side", which waits
		610	for the send to occur.
292		611
293	=item $cv->wait	612	Example: wait for a timer.
294
295	Wait (blocking if necessary) until the C<< ->broadcast >> method has been
296	called on c<$cv>, while servicing other watchers normally.
297
298	You can only wait once on a condition - additional calls will return
299	immediately.
300
301	Not all event models support a blocking wait - some die in that case
302	(programs might want to do that to stay interactive), so I<if you are
303	using this from a module, never require a blocking wait>, but let the
304	caller decide whether the call will block or not (for example, by coupling
305	condition variables with some kind of request results and supporting
306	callbacks so the caller knows that getting the result will not block,
307	while still suppporting blocking waits if the caller so desires).
308
309	Another reason I<never> to C<< ->wait >> in a module is that you cannot
310	sensibly have two C<< ->wait >>'s in parallel, as that would require
311	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
312	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and
313	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
314	from different coroutines, however).
315
316	=item $cv->broadcast
317
318	Flag the condition as ready - a running C<< ->wait >> and all further
319	calls to C<wait> will (eventually) return after this method has been
320	called. If nobody is waiting the broadcast will be remembered..
321
322	=back
323
324	Example:
325		613
326	# wait till the result is ready	614	# wait till the result is ready
327	my $result_ready = AnyEvent->condvar;	615	my $result_ready = AnyEvent->condvar;
328		616
329	# do something such as adding a timer	617	# do something such as adding a timer
330	# or socket watcher the calls $result_ready->broadcast	618	# or socket watcher the calls $result_ready->send
331	# when the "result" is ready.	619	# when the "result" is ready.
332	# in this case, we simply use a timer:	620	# in this case, we simply use a timer:
333	my $w = AnyEvent->timer (	621	my $w = AnyEvent->timer (
334	after => 1,	622	after => 1,
335	cb => sub { $result_ready->broadcast },	623	cb => sub { $result_ready->send },
336	);	624	);
337		625
338	# this "blocks" (while handling events) till the watcher	626	# this "blocks" (while handling events) till the callback
339	# calls broadcast	627	# calls ->send
340	$result_ready->wait;	628	$result_ready->recv;
		629
		630	Example: wait for a timer, but take advantage of the fact that condition
		631	variables are also callable directly.
		632
		633	my $done = AnyEvent->condvar;
		634	my $delay = AnyEvent->timer (after => 5, cb => $done);
		635	$done->recv;
		636
		637	Example: Imagine an API that returns a condvar and doesn't support
		638	callbacks. This is how you make a synchronous call, for example from
		639	the main program:
		640
		641	use AnyEvent::CouchDB;
		642
		643	...
		644
		645	my @info = $couchdb->info->recv;
		646
		647	And this is how you would just set a callback to be called whenever the
		648	results are available:
		649
		650	$couchdb->info->cb (sub {
		651	my @info = $_[0]->recv;
		652	});
		653
		654	=head3 METHODS FOR PRODUCERS
		655
		656	These methods should only be used by the producing side, i.e. the
		657	code/module that eventually sends the signal. Note that it is also
		658	the producer side which creates the condvar in most cases, but it isn't
		659	uncommon for the consumer to create it as well.
		660
		661	=over 4
		662
		663	=item $cv->send (...)
		664
		665	Flag the condition as ready - a running C<< ->recv >> and all further
		666	calls to C<recv> will (eventually) return after this method has been
		667	called. If nobody is waiting the send will be remembered.
		668
		669	If a callback has been set on the condition variable, it is called
		670	immediately from within send.
		671
		672	Any arguments passed to the C<send> call will be returned by all
		673	future C<< ->recv >> calls.
		674
		675	Condition variables are overloaded so one can call them directly (as if
		676	they were a code reference). Calling them directly is the same as calling
		677	C<send>.
		678
		679	=item $cv->croak ($error)
		680
		681	Similar to send, but causes all call's to C<< ->recv >> to invoke
		682	C<Carp::croak> with the given error message/object/scalar.
		683
		684	This can be used to signal any errors to the condition variable
		685	user/consumer. Doing it this way instead of calling C<croak> directly
		686	delays the error detetcion, but has the overwhelmign advantage that it
		687	diagnoses the error at the place where the result is expected, and not
		688	deep in some event clalback without connection to the actual code causing
		689	the problem.
		690
		691	=item $cv->begin ([group callback])
		692
		693	=item $cv->end
		694
		695	These two methods can be used to combine many transactions/events into
		696	one. For example, a function that pings many hosts in parallel might want
		697	to use a condition variable for the whole process.
		698
		699	Every call to C<< ->begin >> will increment a counter, and every call to
		700	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
		701	>>, the (last) callback passed to C<begin> will be executed, passing the
		702	condvar as first argument. That callback is I<supposed> to call C<< ->send
		703	>>, but that is not required. If no group callback was set, C<send> will
		704	be called without any arguments.
		705
		706	You can think of C<< $cv->send >> giving you an OR condition (one call
		707	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		708	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		709
		710	Let's start with a simple example: you have two I/O watchers (for example,
		711	STDOUT and STDERR for a program), and you want to wait for both streams to
		712	close before activating a condvar:
		713
		714	my $cv = AnyEvent->condvar;
		715
		716	$cv->begin; # first watcher
		717	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		718	defined sysread $fh1, my $buf, 4096
		719	or $cv->end;
		720	});
		721
		722	$cv->begin; # second watcher
		723	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		724	defined sysread $fh2, my $buf, 4096
		725	or $cv->end;
		726	});
		727
		728	$cv->recv;
		729
		730	This works because for every event source (EOF on file handle), there is
		731	one call to C<begin>, so the condvar waits for all calls to C<end> before
		732	sending.
		733
		734	The ping example mentioned above is slightly more complicated, as the
		735	there are results to be passwd back, and the number of tasks that are
		736	begung can potentially be zero:
		737
		738	my $cv = AnyEvent->condvar;
		739
		740	my %result;
		741	$cv->begin (sub { shift->send (\%result) });
		742
		743	for my $host (@list_of_hosts) {
		744	$cv->begin;
		745	ping_host_then_call_callback $host, sub {
		746	$result{$host} = ...;
		747	$cv->end;
		748	};
		749	}
		750
		751	$cv->end;
		752
		753	This code fragment supposedly pings a number of hosts and calls
		754	C<send> after results for all then have have been gathered - in any
		755	order. To achieve this, the code issues a call to C<begin> when it starts
		756	each ping request and calls C<end> when it has received some result for
		757	it. Since C<begin> and C<end> only maintain a counter, the order in which
		758	results arrive is not relevant.
		759
		760	There is an additional bracketing call to C<begin> and C<end> outside the
		761	loop, which serves two important purposes: first, it sets the callback
		762	to be called once the counter reaches C<0>, and second, it ensures that
		763	C<send> is called even when C<no> hosts are being pinged (the loop
		764	doesn't execute once).
		765
		766	This is the general pattern when you "fan out" into multiple (but
		767	potentially none) subrequests: use an outer C<begin>/C<end> pair to set
		768	the callback and ensure C<end> is called at least once, and then, for each
		769	subrequest you start, call C<begin> and for each subrequest you finish,
		770	call C<end>.
		771
		772	=back
		773
		774	=head3 METHODS FOR CONSUMERS
		775
		776	These methods should only be used by the consuming side, i.e. the
		777	code awaits the condition.
		778
		779	=over 4
		780
		781	=item $cv->recv
		782
		783	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
		784	>> methods have been called on c<$cv>, while servicing other watchers
		785	normally.
		786
		787	You can only wait once on a condition - additional calls are valid but
		788	will return immediately.
		789
		790	If an error condition has been set by calling C<< ->croak >>, then this
		791	function will call C<croak>.
		792
		793	In list context, all parameters passed to C<send> will be returned,
		794	in scalar context only the first one will be returned.
		795
		796	Note that doing a blocking wait in a callback is not supported by any
		797	event loop, that is, recursive invocation of a blocking C<< ->recv
		798	>> is not allowed, and the C<recv> call will C<croak> if such a
		799	condition is detected. This condition can be slightly loosened by using
		800	L<Coro::AnyEvent>, which allows you to do a blocking C<< ->recv >> from
		801	any thread that doesn't run the event loop itself.
		802
		803	Not all event models support a blocking wait - some die in that case
		804	(programs might want to do that to stay interactive), so I<if you are
		805	using this from a module, never require a blocking wait>. Instead, let the
		806	caller decide whether the call will block or not (for example, by coupling
		807	condition variables with some kind of request results and supporting
		808	callbacks so the caller knows that getting the result will not block,
		809	while still supporting blocking waits if the caller so desires).
		810
		811	You can ensure that C<< -recv >> never blocks by setting a callback and
		812	only calling C<< ->recv >> from within that callback (or at a later
		813	time). This will work even when the event loop does not support blocking
		814	waits otherwise.
		815
		816	=item $bool = $cv->ready
		817
		818	Returns true when the condition is "true", i.e. whether C<send> or
		819	C<croak> have been called.
		820
		821	=item $cb = $cv->cb ($cb->($cv))
		822
		823	This is a mutator function that returns the callback set and optionally
		824	replaces it before doing so.
		825
		826	The callback will be called when the condition becomes (or already was)
		827	"true", i.e. when C<send> or C<croak> are called (or were called), with
		828	the only argument being the condition variable itself. Calling C<recv>
		829	inside the callback or at any later time is guaranteed not to block.
		830
		831	=back
		832
		833	=head1 SUPPORTED EVENT LOOPS/BACKENDS
		834
		835	The available backend classes are (every class has its own manpage):
		836
		837	=over 4
		838
		839	=item Backends that are autoprobed when no other event loop can be found.
		840
		841	EV is the preferred backend when no other event loop seems to be in
		842	use. If EV is not installed, then AnyEvent will fall back to its own
		843	pure-perl implementation, which is available everywhere as it comes with
		844	AnyEvent itself.
		845
		846	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		847	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
		848
		849	=item Backends that are transparently being picked up when they are used.
		850
		851	These will be used when they are currently loaded when the first watcher
		852	is created, in which case it is assumed that the application is using
		853	them. This means that AnyEvent will automatically pick the right backend
		854	when the main program loads an event module before anything starts to
		855	create watchers. Nothing special needs to be done by the main program.
		856
		857	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		858	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		859	AnyEvent::Impl::Tk based on Tk, very broken.
		860	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		861	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		862	AnyEvent::Impl::Irssi used when running within irssi.
		863
		864	=item Backends with special needs.
		865
		866	Qt requires the Qt::Application to be instantiated first, but will
		867	otherwise be picked up automatically. As long as the main program
		868	instantiates the application before any AnyEvent watchers are created,
		869	everything should just work.
		870
		871	AnyEvent::Impl::Qt based on Qt.
		872
		873	Support for IO::Async can only be partial, as it is too broken and
		874	architecturally limited to even support the AnyEvent API. It also
		875	is the only event loop that needs the loop to be set explicitly, so
		876	it can only be used by a main program knowing about AnyEvent. See
		877	L<AnyEvent::Impl::Async> for the gory details.
		878
		879	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
		880
		881	=item Event loops that are indirectly supported via other backends.
		882
		883	Some event loops can be supported via other modules:
		884
		885	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		886
		887	B<WxWidgets> has no support for watching file handles. However, you can
		888	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		889	polls 20 times per second, which was considered to be too horrible to even
		890	consider for AnyEvent.
		891
		892	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		893	backend, so it can be supported through POE.
		894
		895	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		896	load L<POE> when detecting them, in the hope that POE will pick them up,
		897	in which case everything will be automatic.
		898
		899	=back
341		900
342	=head1 GLOBAL VARIABLES AND FUNCTIONS	901	=head1 GLOBAL VARIABLES AND FUNCTIONS
343		902
		903	These are not normally required to use AnyEvent, but can be useful to
		904	write AnyEvent extension modules.
		905
344	=over 4	906	=over 4
345		907
346	=item $AnyEvent::MODEL	908	=item $AnyEvent::MODEL
347		909
348	Contains C<undef> until the first watcher is being created. Then it	910	Contains C<undef> until the first watcher is being created, before the
		911	backend has been autodetected.
		912
349	contains the event model that is being used, which is the name of the	913	Afterwards it contains the event model that is being used, which is the
350	Perl class implementing the model. This class is usually one of the	914	name of the Perl class implementing the model. This class is usually one
351	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	915	of the C<AnyEvent::Impl:xxx> modules, but can be any other class in the
352	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	916	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
353		917	will be C<urxvt::anyevent>).
354	The known classes so far are:
355
356	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
357	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
358	AnyEvent::Impl::EV based on EV (an interface to libev, also best choice).
359	AnyEvent::Impl::Event based on Event, also second best choice :)
360	AnyEvent::Impl::Glib based on Glib, third-best choice.
361	AnyEvent::Impl::Tk based on Tk, very bad choice.
362	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
363		918
364	=item AnyEvent::detect	919	=item AnyEvent::detect
365		920
366	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	921	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
367	if necessary. You should only call this function right before you would	922	if necessary. You should only call this function right before you would
368	have created an AnyEvent watcher anyway, that is, as late as possible at	923	have created an AnyEvent watcher anyway, that is, as late as possible at
369	runtime.	924	runtime, and not e.g. while initialising of your module.
		925
		926	If you need to do some initialisation before AnyEvent watchers are
		927	created, use C<post_detect>.
		928
		929	=item $guard = AnyEvent::post_detect { BLOCK }
		930
		931	Arranges for the code block to be executed as soon as the event model is
		932	autodetected (or immediately if this has already happened).
		933
		934	The block will be executed I<after> the actual backend has been detected
		935	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		936	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		937	other initialisations - see the sources of L<AnyEvent::Strict> or
		938	L<AnyEvent::AIO> to see how this is used.
		939
		940	The most common usage is to create some global watchers, without forcing
		941	event module detection too early, for example, L<AnyEvent::AIO> creates
		942	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		943	avoid autodetecting the event module at load time.
		944
		945	If called in scalar or list context, then it creates and returns an object
		946	that automatically removes the callback again when it is destroyed (or
		947	C<undef> when the hook was immediately executed). See L<AnyEvent::AIO> for
		948	a case where this is useful.
		949
		950	Example: Create a watcher for the IO::AIO module and store it in
		951	C<$WATCHER>. Only do so after the event loop is initialised, though.
		952
		953	our WATCHER;
		954
		955	my $guard = AnyEvent::post_detect {
		956	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		957	};
		958
		959	# the ||= is important in case post_detect immediately runs the block,
		960	# as to not clobber the newly-created watcher. assigning both watcher and
		961	# post_detect guard to the same variable has the advantage of users being
		962	# able to just C<undef $WATCHER> if the watcher causes them grief.
		963
		964	$WATCHER ||= $guard;
		965
		966	=item @AnyEvent::post_detect
		967
		968	If there are any code references in this array (you can C<push> to it
		969	before or after loading AnyEvent), then they will called directly after
		970	the event loop has been chosen.
		971
		972	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		973	if it is defined then the event loop has already been detected, and the
		974	array will be ignored.
		975
		976	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		977	it, as it takes care of these details.
		978
		979	This variable is mainly useful for modules that can do something useful
		980	when AnyEvent is used and thus want to know when it is initialised, but do
		981	not need to even load it by default. This array provides the means to hook
		982	into AnyEvent passively, without loading it.
		983
		984	Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used
		985	together, you could put this into Coro (this is the actual code used by
		986	Coro to accomplish this):
		987
		988	if (defined $AnyEvent::MODEL) {
		989	# AnyEvent already initialised, so load Coro::AnyEvent
		990	require Coro::AnyEvent;
		991	} else {
		992	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent
		993	# as soon as it is
		994	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };
		995	}
370		996
371	=back	997	=back
372		998
373	=head1 WHAT TO DO IN A MODULE	999	=head1 WHAT TO DO IN A MODULE
374		1000
…		…
378	Be careful when you create watchers in the module body - AnyEvent will	1004	Be careful when you create watchers in the module body - AnyEvent will
379	decide which event module to use as soon as the first method is called, so	1005	decide which event module to use as soon as the first method is called, so
380	by calling AnyEvent in your module body you force the user of your module	1006	by calling AnyEvent in your module body you force the user of your module
381	to load the event module first.	1007	to load the event module first.
382		1008
383	Never call C<< ->wait >> on a condition variable unless you I<know> that	1009	Never call C<< ->recv >> on a condition variable unless you I<know> that
384	the C<< ->broadcast >> method has been called on it already. This is	1010	the C<< ->send >> method has been called on it already. This is
385	because it will stall the whole program, and the whole point of using	1011	because it will stall the whole program, and the whole point of using
386	events is to stay interactive.	1012	events is to stay interactive.
387		1013
388	It is fine, however, to call C<< ->wait >> when the user of your module	1014	It is fine, however, to call C<< ->recv >> when the user of your module
389	requests it (i.e. if you create a http request object ad have a method	1015	requests it (i.e. if you create a http request object ad have a method
390	called C<results> that returns the results, it should call C<< ->wait >>	1016	called C<results> that returns the results, it should call C<< ->recv >>
391	freely, as the user of your module knows what she is doing. always).	1017	freely, as the user of your module knows what she is doing. always).
392		1018
393	=head1 WHAT TO DO IN THE MAIN PROGRAM	1019	=head1 WHAT TO DO IN THE MAIN PROGRAM
394		1020
395	There will always be a single main program - the only place that should	1021	There will always be a single main program - the only place that should
…		…
397		1023
398	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	1024	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
399	do anything special (it does not need to be event-based) and let AnyEvent	1025	do anything special (it does not need to be event-based) and let AnyEvent
400	decide which implementation to chose if some module relies on it.	1026	decide which implementation to chose if some module relies on it.
401		1027
402	If the main program relies on a specific event model. For example, in	1028	If the main program relies on a specific event model - for example, in
403	Gtk2 programs you have to rely on the Glib module. You should load the	1029	Gtk2 programs you have to rely on the Glib module - you should load the
404	event module before loading AnyEvent or any module that uses it: generally	1030	event module before loading AnyEvent or any module that uses it: generally
405	speaking, you should load it as early as possible. The reason is that	1031	speaking, you should load it as early as possible. The reason is that
406	modules might create watchers when they are loaded, and AnyEvent will	1032	modules might create watchers when they are loaded, and AnyEvent will
407	decide on the event model to use as soon as it creates watchers, and it	1033	decide on the event model to use as soon as it creates watchers, and it
408	might chose the wrong one unless you load the correct one yourself.	1034	might chose the wrong one unless you load the correct one yourself.
409		1035
410	You can chose to use a rather inefficient pure-perl implementation by	1036	You can chose to use a pure-perl implementation by loading the
411	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	1037	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
412	behaviour everywhere, but letting AnyEvent chose is generally better.	1038	everywhere, but letting AnyEvent chose the model is generally better.
		1039
		1040	=head2 MAINLOOP EMULATION
		1041
		1042	Sometimes (often for short test scripts, or even standalone programs who
		1043	only want to use AnyEvent), you do not want to run a specific event loop.
		1044
		1045	In that case, you can use a condition variable like this:
		1046
		1047	AnyEvent->condvar->recv;
		1048
		1049	This has the effect of entering the event loop and looping forever.
		1050
		1051	Note that usually your program has some exit condition, in which case
		1052	it is better to use the "traditional" approach of storing a condition
		1053	variable somewhere, waiting for it, and sending it when the program should
		1054	exit cleanly.
		1055
		1056
		1057	=head1 OTHER MODULES
		1058
		1059	The following is a non-exhaustive list of additional modules that use
		1060	AnyEvent as a client and can therefore be mixed easily with other AnyEvent
		1061	modules and other event loops in the same program. Some of the modules
		1062	come with AnyEvent, most are available via CPAN.
		1063
		1064	=over 4
		1065
		1066	=item L<AnyEvent::Util>
		1067
		1068	Contains various utility functions that replace often-used but blocking
		1069	functions such as C<inet_aton> by event-/callback-based versions.
		1070
		1071	=item L<AnyEvent::Socket>
		1072
		1073	Provides various utility functions for (internet protocol) sockets,
		1074	addresses and name resolution. Also functions to create non-blocking tcp
		1075	connections or tcp servers, with IPv6 and SRV record support and more.
		1076
		1077	=item L<AnyEvent::Handle>
		1078
		1079	Provide read and write buffers, manages watchers for reads and writes,
		1080	supports raw and formatted I/O, I/O queued and fully transparent and
		1081	non-blocking SSL/TLS (via L<AnyEvent::TLS>.
		1082
		1083	=item L<AnyEvent::DNS>
		1084
		1085	Provides rich asynchronous DNS resolver capabilities.
		1086
		1087	=item L<AnyEvent::HTTP>
		1088
		1089	A simple-to-use HTTP library that is capable of making a lot of concurrent
		1090	HTTP requests.
		1091
		1092	=item L<AnyEvent::HTTPD>
		1093
		1094	Provides a simple web application server framework.
		1095
		1096	=item L<AnyEvent::FastPing>
		1097
		1098	The fastest ping in the west.
		1099
		1100	=item L<AnyEvent::DBI>
		1101
		1102	Executes L<DBI> requests asynchronously in a proxy process.
		1103
		1104	=item L<AnyEvent::AIO>
		1105
		1106	Truly asynchronous I/O, should be in the toolbox of every event
		1107	programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
		1108	together.
		1109
		1110	=item L<AnyEvent::BDB>
		1111
		1112	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
		1113	L<BDB> and AnyEvent together.
		1114
		1115	=item L<AnyEvent::GPSD>
		1116
		1117	A non-blocking interface to gpsd, a daemon delivering GPS information.
		1118
		1119	=item L<AnyEvent::IRC>
		1120
		1121	AnyEvent based IRC client module family (replacing the older Net::IRC3).
		1122
		1123	=item L<AnyEvent::XMPP>
		1124
		1125	AnyEvent based XMPP (Jabber protocol) module family (replacing the older
		1126	Net::XMPP2>.
		1127
		1128	=item L<AnyEvent::IGS>
		1129
		1130	A non-blocking interface to the Internet Go Server protocol (used by
		1131	L<App::IGS>).
		1132
		1133	=item L<Net::FCP>
		1134
		1135	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
		1136	of AnyEvent.
		1137
		1138	=item L<Event::ExecFlow>
		1139
		1140	High level API for event-based execution flow control.
		1141
		1142	=item L<Coro>
		1143
		1144	Has special support for AnyEvent via L<Coro::AnyEvent>.
		1145
		1146	=back
413		1147
414	=cut	1148	=cut
415		1149
416	package AnyEvent;	1150	package AnyEvent;
417		1151
418	no warnings;	1152	# basically a tuned-down version of common::sense
419	use strict;	1153	sub common_sense {
		1154	# from common:.sense 1.0
		1155	${^WARNING_BITS} = "\xfc\x3f\x33\x00\x0f\xf3\xcf\xc0\xf3\xfc\x33\x00";
		1156	# use strict vars subs - NO UTF-8, as Util.pm doesn't like this atm. (uts46data.pl)
		1157	$^H |= 0x00000600;
		1158	}
420		1159
		1160	BEGIN { AnyEvent::common_sense }
		1161
421	use Carp;	1162	use Carp ();
422		1163
423	our $VERSION = '3.11';	1164	our $VERSION = '5.251';
424	our $MODEL;	1165	our $MODEL;
425		1166
426	our $AUTOLOAD;	1167	our $AUTOLOAD;
427	our @ISA;	1168	our @ISA;
428		1169
429	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
430
431	our @REGISTRY;	1170	our @REGISTRY;
432		1171
		1172	our $VERBOSE;
		1173
		1174	BEGIN {
		1175	require "AnyEvent/constants.pl";
		1176
		1177	eval "sub TAINT (){" . (${^TAINT}*1) . "}";
		1178
		1179	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1180	if ${^TAINT};
		1181
		1182	$VERBOSE = $ENV{PERL_ANYEVENT_VERBOSE}*1;
		1183
		1184	}
		1185
		1186	our $MAX_SIGNAL_LATENCY = 10;
		1187
		1188	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		1189
		1190	{
		1191	my $idx;
		1192	$PROTOCOL{$_} = ++$idx
		1193	for reverse split /\s*,\s*/,
		1194	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		1195	}
		1196
433	my @models = (	1197	my @models = (
434	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
435	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
436	[EV:: => AnyEvent::Impl::EV::],	1198	[EV:: => AnyEvent::Impl::EV:: , 1],
		1199	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl:: , 1],
		1200	# everything below here will not (normally) be autoprobed
		1201	# as the pureperl backend should work everywhere
		1202	# and is usually faster
437	[Event:: => AnyEvent::Impl::Event::],	1203	[Event:: => AnyEvent::Impl::Event::, 1],
438	[Glib:: => AnyEvent::Impl::Glib::],	1204	[Glib:: => AnyEvent::Impl::Glib:: , 1], # becomes extremely slow with many watchers
		1205	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		1206	[Irssi:: => AnyEvent::Impl::Irssi::], # Irssi has a bogus "Event" package
		1207	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		1208	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		1209	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
439	[Tk:: => AnyEvent::Impl::Tk::],	1210	[Wx:: => AnyEvent::Impl::POE::],
440	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1211	[Prima:: => AnyEvent::Impl::POE::],
		1212	# IO::Async is just too broken - we would need workarounds for its
		1213	# byzantine signal and broken child handling, among others.
		1214	# IO::Async is rather hard to detect, as it doesn't have any
		1215	# obvious default class.
		1216	[IO::Async:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1217	[IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1218	[IO::Async::Notifier:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1219	[AnyEvent::Impl::IOAsync:: => AnyEvent::Impl::IOAsync::], # requires special main program
441	);	1220	);
442		1221
443	our %method = map +($_ => 1), qw(io timer condvar broadcast wait signal one_event DESTROY);	1222	our %method = map +($_ => 1),
		1223	qw(io timer time now now_update signal child idle condvar one_event DESTROY);
		1224
		1225	our @post_detect;
		1226
		1227	sub post_detect(&) {
		1228	my ($cb) = @_;
		1229
		1230	push @post_detect, $cb;
		1231
		1232	defined wantarray
		1233	? bless \$cb, "AnyEvent::Util::postdetect"
		1234	: ()
		1235	}
		1236
		1237	sub AnyEvent::Util::postdetect::DESTROY {
		1238	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		1239	}
444		1240
445	sub detect() {	1241	sub detect() {
		1242	# free some memory
		1243	*detect = sub () { $MODEL };
		1244
		1245	local $!; # for good measure
		1246	local $SIG{__DIE__};
		1247
		1248	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
		1249	my $model = "AnyEvent::Impl::$1";
		1250	if (eval "require $model") {
		1251	$MODEL = $model;
		1252	warn "AnyEvent: loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.\n" if $VERBOSE >= 2;
		1253	} else {
		1254	warn "AnyEvent: unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@" if $VERBOSE;
		1255	}
		1256	}
		1257
		1258	# check for already loaded models
446	unless ($MODEL) {	1259	unless ($MODEL) {
447	no strict 'refs';
448
449	# check for already loaded models
450	for (@REGISTRY, @models) {	1260	for (@REGISTRY, @models) {
451	my ($package, $model) = @$_;	1261	my ($package, $model) = @$_;
452	if (${"$package\::VERSION"} > 0) {	1262	if (${"$package\::VERSION"} > 0) {
453	if (eval "require $model") {	1263	if (eval "require $model") {
454	$MODEL = $model;	1264	$MODEL = $model;
455	warn "AnyEvent: found model '$model', using it.\n" if $verbose > 1;	1265	warn "AnyEvent: autodetected model '$model', using it.\n" if $VERBOSE >= 2;
456	last;	1266	last;
457	}	1267	}
458	}	1268	}
459	}	1269	}
460		1270
461	unless ($MODEL) {	1271	unless ($MODEL) {
462	# try to load a model	1272	# try to autoload a model
463
464	for (@REGISTRY, @models) {	1273	for (@REGISTRY, @models) {
465	my ($package, $model) = @$_;	1274	my ($package, $model, $autoload) = @$_;
		1275	if (
		1276	$autoload
466	if (eval "require $package"	1277	and eval "require $package"
467	and ${"$package\::VERSION"} > 0	1278	and ${"$package\::VERSION"} > 0
468	and eval "require $model") {	1279	and eval "require $model"
		1280	) {
469	$MODEL = $model;	1281	$MODEL = $model;
470	warn "AnyEvent: autoprobed and loaded model '$model', using it.\n" if $verbose > 1;	1282	warn "AnyEvent: autoloaded model '$model', using it.\n" if $VERBOSE >= 2;
471	last;	1283	last;
472	}	1284	}
473	}	1285	}
474		1286
475	$MODEL	1287	$MODEL
476	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), Glib or Tk.";	1288	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.\n";
477	}	1289	}
478
479	unshift @ISA, $MODEL;
480	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
481	}	1290	}
		1291
		1292	@models = (); # free probe data
		1293
		1294	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		1295	unshift @ISA, $MODEL;
		1296
		1297	# now nuke some methods that are overriden by the backend.
		1298	# SUPER is not allowed.
		1299	for (qw(time signal child idle)) {
		1300	undef &{"AnyEvent::Base::$_"}
		1301	if defined &{"$MODEL\::$_"};
		1302	}
		1303
		1304	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
		1305
		1306	(shift @post_detect)->() while @post_detect;
		1307
		1308	*post_detect = sub(&) {
		1309	shift->();
		1310
		1311	undef
		1312	};
482		1313
483	$MODEL	1314	$MODEL
484	}	1315	}
485		1316
486	sub AUTOLOAD {	1317	sub AUTOLOAD {
487	(my $func = $AUTOLOAD) =~ s/.*://;	1318	(my $func = $AUTOLOAD) =~ s/.*://;
488		1319
489	$method{$func}	1320	$method{$func}
490	or croak "$func: not a valid method for AnyEvent objects";	1321	or Carp::croak "$func: not a valid AnyEvent class method";
491		1322
492	detect unless $MODEL;	1323	detect;
493		1324
494	my $class = shift;	1325	my $class = shift;
495	$class->$func (@_);	1326	$class->$func (@_);
496	}	1327	}
497		1328
		1329	# utility function to dup a filehandle. this is used by many backends
		1330	# to support binding more than one watcher per filehandle (they usually
		1331	# allow only one watcher per fd, so we dup it to get a different one).
		1332	sub _dupfh($$;$$) {
		1333	my ($poll, $fh, $r, $w) = @_;
		1334
		1335	# cygwin requires the fh mode to be matching, unix doesn't
		1336	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1337
		1338	open my $fh2, $mode, $fh
		1339	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1340
		1341	# we assume CLOEXEC is already set by perl in all important cases
		1342
		1343	($fh2, $rw)
		1344	}
		1345
		1346	=head1 SIMPLIFIED AE API
		1347
		1348	Starting with version 5.0, AnyEvent officially supports a second, much
		1349	simpler, API that is designed to reduce the calling, typing and memory
		1350	overhead by using function call syntax and a fixed number of parameters.
		1351
		1352	See the L<AE> manpage for details.
		1353
		1354	=cut
		1355
		1356	package AE;
		1357
		1358	our $VERSION = $AnyEvent::VERSION;
		1359
		1360	# fall back to the main API by default - backends and AnyEvent::Base
		1361	# implementations can overwrite these.
		1362
		1363	sub io($$$) {
		1364	AnyEvent->io (fh => $_[0], poll => $_[1] ? "w" : "r", cb => $_[2])
		1365	}
		1366
		1367	sub timer($$$) {
		1368	AnyEvent->timer (after => $_[0], interval => $_[1], cb => $_[2])
		1369	}
		1370
		1371	sub signal($$) {
		1372	AnyEvent->signal (signal => $_[0], cb => $_[1])
		1373	}
		1374
		1375	sub child($$) {
		1376	AnyEvent->child (pid => $_[0], cb => $_[1])
		1377	}
		1378
		1379	sub idle($) {
		1380	AnyEvent->idle (cb => $_[0])
		1381	}
		1382
		1383	sub cv(;&) {
		1384	AnyEvent->condvar (@_ ? (cb => $_[0]) : ())
		1385	}
		1386
		1387	sub now() {
		1388	AnyEvent->now
		1389	}
		1390
		1391	sub now_update() {
		1392	AnyEvent->now_update
		1393	}
		1394
		1395	sub time() {
		1396	AnyEvent->time
		1397	}
		1398
498	package AnyEvent::Base;	1399	package AnyEvent::Base;
499		1400
		1401	# default implementations for many methods
		1402
		1403	sub time {
		1404	eval q{ # poor man's autoloading {}
		1405	# probe for availability of Time::HiRes
		1406	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1407	warn "AnyEvent: using Time::HiRes for sub-second timing accuracy.\n" if $VERBOSE >= 8;
		1408	*AE::time = \&Time::HiRes::time;
		1409	# if (eval "use POSIX (); (POSIX::times())...
		1410	} else {
		1411	warn "AnyEvent: using built-in time(), WARNING, no sub-second resolution!\n" if $VERBOSE;
		1412	*AE::time = sub (){ time }; # epic fail
		1413	}
		1414
		1415	*time = sub { AE::time }; # different prototypes
		1416	};
		1417	die if $@;
		1418
		1419	&time
		1420	}
		1421
		1422	*now = \&time;
		1423
		1424	sub now_update { }
		1425
500	# default implementation for ->condvar, ->wait, ->broadcast	1426	# default implementation for ->condvar
501		1427
502	sub condvar {	1428	sub condvar {
503	bless \my $flag, "AnyEvent::Base::CondVar"	1429	eval q{ # poor man's autoloading {}
504	}	1430	*condvar = sub {
		1431	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
		1432	};
505		1433
506	sub AnyEvent::Base::CondVar::broadcast {	1434	*AE::cv = sub (;&) {
507	${$_[0]}++;	1435	bless { @_ ? (_ae_cb => shift) : () }, "AnyEvent::CondVar"
508	}	1436	};
		1437	};
		1438	die if $@;
509		1439
510	sub AnyEvent::Base::CondVar::wait {	1440	&condvar
511	AnyEvent->one_event while !${$_[0]};
512	}	1441	}
513		1442
514	# default implementation for ->signal	1443	# default implementation for ->signal
515		1444
516	our %SIG_CB;	1445	our $HAVE_ASYNC_INTERRUPT;
		1446
		1447	sub _have_async_interrupt() {
		1448	$HAVE_ASYNC_INTERRUPT = 1*(!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT}
		1449	&& eval "use Async::Interrupt 1.02 (); 1")
		1450	unless defined $HAVE_ASYNC_INTERRUPT;
		1451
		1452	$HAVE_ASYNC_INTERRUPT
		1453	}
		1454
		1455	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1456	our (%SIG_ASY, %SIG_ASY_W);
		1457	our ($SIG_COUNT, $SIG_TW);
		1458
		1459	# install a dummy wakeup watcher to reduce signal catching latency
		1460	# used by Impls
		1461	sub _sig_add() {
		1462	unless ($SIG_COUNT++) {
		1463	# try to align timer on a full-second boundary, if possible
		1464	my $NOW = AE::now;
		1465
		1466	$SIG_TW = AE::timer
		1467	$MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1468	$MAX_SIGNAL_LATENCY,
		1469	sub { } # just for the PERL_ASYNC_CHECK
		1470	;
		1471	}
		1472	}
		1473
		1474	sub _sig_del {
		1475	undef $SIG_TW
		1476	unless --$SIG_COUNT;
		1477	}
		1478
		1479	our $_sig_name_init; $_sig_name_init = sub {
		1480	eval q{ # poor man's autoloading {}
		1481	undef $_sig_name_init;
		1482
		1483	if (_have_async_interrupt) {
		1484	*sig2num = \&Async::Interrupt::sig2num;
		1485	*sig2name = \&Async::Interrupt::sig2name;
		1486	} else {
		1487	require Config;
		1488
		1489	my %signame2num;
		1490	@signame2num{ split ' ', $Config::Config{sig_name} }
		1491	= split ' ', $Config::Config{sig_num};
		1492
		1493	my @signum2name;
		1494	@signum2name[values %signame2num] = keys %signame2num;
		1495
		1496	*sig2num = sub($) {
		1497	$_[0] > 0 ? shift : $signame2num{+shift}
		1498	};
		1499	*sig2name = sub ($) {
		1500	$_[0] > 0 ? $signum2name[+shift] : shift
		1501	};
		1502	}
		1503	};
		1504	die if $@;
		1505	};
		1506
		1507	sub sig2num ($) { &$_sig_name_init; &sig2num }
		1508	sub sig2name($) { &$_sig_name_init; &sig2name }
517		1509
518	sub signal {	1510	sub signal {
		1511	eval q{ # poor man's autoloading {}
		1512	# probe for availability of Async::Interrupt
		1513	if (_have_async_interrupt) {
		1514	warn "AnyEvent: using Async::Interrupt for race-free signal handling.\n" if $VERBOSE >= 8;
		1515
		1516	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1517	$SIG_IO = AE::io $SIGPIPE_R->fileno, 0, \&_signal_exec;
		1518
		1519	} else {
		1520	warn "AnyEvent: using emulated perl signal handling with latency timer.\n" if $VERBOSE >= 8;
		1521
		1522	if (AnyEvent::WIN32) {
		1523	require AnyEvent::Util;
		1524
		1525	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1526	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R, 1) if $SIGPIPE_R;
		1527	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W, 1) if $SIGPIPE_W; # just in case
		1528	} else {
		1529	pipe $SIGPIPE_R, $SIGPIPE_W;
		1530	fcntl $SIGPIPE_R, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_R;
		1531	fcntl $SIGPIPE_W, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_W; # just in case
		1532
		1533	# not strictly required, as $^F is normally 2, but let's make sure...
		1534	fcntl $SIGPIPE_R, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1535	fcntl $SIGPIPE_W, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1536	}
		1537
		1538	$SIGPIPE_R
		1539	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1540
		1541	$SIG_IO = AE::io $SIGPIPE_R, 0, \&_signal_exec;
		1542	}
		1543
		1544	*signal = $HAVE_ASYNC_INTERRUPT
		1545	? sub {
519	my (undef, %arg) = @_;	1546	my (undef, %arg) = @_;
520		1547
		1548	# async::interrupt
521	my $signal = uc $arg{signal}	1549	my $signal = sig2num $arg{signal};
522	or Carp::croak "required option 'signal' is missing";
523
524	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1550	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1551
		1552	$SIG_ASY{$signal} ||= new Async::Interrupt
		1553	cb => sub { undef $SIG_EV{$signal} },
		1554	signal => $signal,
		1555	pipe => [$SIGPIPE_R->filenos],
		1556	pipe_autodrain => 0,
		1557	;
		1558
		1559	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1560	}
		1561	: sub {
		1562	my (undef, %arg) = @_;
		1563
		1564	# pure perl
		1565	my $signal = sig2name $arg{signal};
		1566	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1567
525	$SIG{$signal} ||= sub {	1568	$SIG{$signal} ||= sub {
		1569	local $!;
		1570	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1571	undef $SIG_EV{$signal};
		1572	};
		1573
		1574	# can't do signal processing without introducing races in pure perl,
		1575	# so limit the signal latency.
		1576	_sig_add;
		1577
		1578	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1579	}
		1580	;
		1581
		1582	*AnyEvent::Base::signal::DESTROY = sub {
		1583	my ($signal, $cb) = @{$_[0]};
		1584
		1585	_sig_del;
		1586
		1587	delete $SIG_CB{$signal}{$cb};
		1588
		1589	$HAVE_ASYNC_INTERRUPT
		1590	? delete $SIG_ASY{$signal}
		1591	: # delete doesn't work with older perls - they then
		1592	# print weird messages, or just unconditionally exit
		1593	# instead of getting the default action.
		1594	undef $SIG{$signal}
		1595	unless keys %{ $SIG_CB{$signal} };
		1596	};
		1597
		1598	*_signal_exec = sub {
		1599	$HAVE_ASYNC_INTERRUPT
		1600	? $SIGPIPE_R->drain
		1601	: sysread $SIGPIPE_R, (my $dummy), 9;
		1602
		1603	while (%SIG_EV) {
		1604	for (keys %SIG_EV) {
		1605	delete $SIG_EV{$_};
526	$_->() for values %{ $SIG_CB{$signal} || {} };	1606	$_->() for values %{ $SIG_CB{$_} || {} };
		1607	}
		1608	}
		1609	};
527	};	1610	};
		1611	die if $@;
528		1612
529	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1613	&signal
530	}
531
532	sub AnyEvent::Base::Signal::DESTROY {
533	my ($signal, $cb) = @{$_[0]};
534
535	delete $SIG_CB{$signal}{$cb};
536
537	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };
538	}	1614	}
539		1615
540	# default implementation for ->child	1616	# default implementation for ->child
541		1617
542	our %PID_CB;	1618	our %PID_CB;
543	our $CHLD_W;	1619	our $CHLD_W;
544	our $CHLD_DELAY_W;	1620	our $CHLD_DELAY_W;
545	our $PID_IDLE;
546	our $WNOHANG;	1621	our $WNOHANG;
547		1622
548	sub _child_wait {	1623	# used by many Impl's
549	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1624	sub _emit_childstatus($$) {
		1625	my (undef, $rpid, $rstatus) = @_;
		1626
		1627	$_->($rpid, $rstatus)
550	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1628	for values %{ $PID_CB{$rpid} || {} },
551	(values %{ $PID_CB{0} || {} });	1629	values %{ $PID_CB{0} || {} };
552	}
553
554	undef $PID_IDLE;
555	}
556
557	sub _sigchld {
558	# make sure we deliver these changes "synchronous" with the event loop.
559	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {
560	undef $CHLD_DELAY_W;
561	&_child_wait;
562	});
563	}	1630	}
564		1631
565	sub child {	1632	sub child {
		1633	eval q{ # poor man's autoloading {}
		1634	*_sigchld = sub {
		1635	my $pid;
		1636
		1637	AnyEvent->_emit_childstatus ($pid, $?)
		1638	while ($pid = waitpid -1, $WNOHANG) > 0;
		1639	};
		1640
		1641	*child = sub {
566	my (undef, %arg) = @_;	1642	my (undef, %arg) = @_;
567		1643
568	defined (my $pid = $arg{pid} + 0)	1644	defined (my $pid = $arg{pid} + 0)
569	or Carp::croak "required option 'pid' is missing";	1645	or Carp::croak "required option 'pid' is missing";
570		1646
571	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1647	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
572		1648
573	unless ($WNOHANG) {	1649	# WNOHANG is almost cetrainly 1 everywhere
574	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;	1650	$WNOHANG ||= $^O =~ /^(?:openbsd|netbsd|linux|freebsd|cygwin|MSWin32)$/
575	}	1651	? 1
		1652	: eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
576		1653
577	unless ($CHLD_W) {	1654	unless ($CHLD_W) {
578	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1655	$CHLD_W = AE::signal CHLD => \&_sigchld;
579	# child could be a zombie already, so make at least one round	1656	# child could be a zombie already, so make at least one round
580	&_sigchld;	1657	&_sigchld;
581	}	1658	}
582		1659
583	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	1660	bless [$pid, $arg{cb}], "AnyEvent::Base::child"
584	}	1661	};
585		1662
586	sub AnyEvent::Base::Child::DESTROY {	1663	*AnyEvent::Base::child::DESTROY = sub {
587	my ($pid, $cb) = @{$_[0]};	1664	my ($pid, $cb) = @{$_[0]};
588		1665
589	delete $PID_CB{$pid}{$cb};	1666	delete $PID_CB{$pid}{$cb};
590	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1667	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
591		1668
592	undef $CHLD_W unless keys %PID_CB;	1669	undef $CHLD_W unless keys %PID_CB;
		1670	};
		1671	};
		1672	die if $@;
		1673
		1674	&child
593	}	1675	}
		1676
		1677	# idle emulation is done by simply using a timer, regardless
		1678	# of whether the process is idle or not, and not letting
		1679	# the callback use more than 50% of the time.
		1680	sub idle {
		1681	eval q{ # poor man's autoloading {}
		1682	*idle = sub {
		1683	my (undef, %arg) = @_;
		1684
		1685	my ($cb, $w, $rcb) = $arg{cb};
		1686
		1687	$rcb = sub {
		1688	if ($cb) {
		1689	$w = _time;
		1690	&$cb;
		1691	$w = _time - $w;
		1692
		1693	# never use more then 50% of the time for the idle watcher,
		1694	# within some limits
		1695	$w = 0.0001 if $w < 0.0001;
		1696	$w = 5 if $w > 5;
		1697
		1698	$w = AE::timer $w, 0, $rcb;
		1699	} else {
		1700	# clean up...
		1701	undef $w;
		1702	undef $rcb;
		1703	}
		1704	};
		1705
		1706	$w = AE::timer 0.05, 0, $rcb;
		1707
		1708	bless \\$cb, "AnyEvent::Base::idle"
		1709	};
		1710
		1711	*AnyEvent::Base::idle::DESTROY = sub {
		1712	undef $${$_[0]};
		1713	};
		1714	};
		1715	die if $@;
		1716
		1717	&idle
		1718	}
		1719
		1720	package AnyEvent::CondVar;
		1721
		1722	our @ISA = AnyEvent::CondVar::Base::;
		1723
		1724	package AnyEvent::CondVar::Base;
		1725
		1726	#use overload
		1727	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1728	# fallback => 1;
		1729
		1730	# save 300+ kilobytes by dirtily hardcoding overloading
		1731	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1732	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1733	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1734	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1735
		1736	our $WAITING;
		1737
		1738	sub _send {
		1739	# nop
		1740	}
		1741
		1742	sub send {
		1743	my $cv = shift;
		1744	$cv->{_ae_sent} = [@_];
		1745	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1746	$cv->_send;
		1747	}
		1748
		1749	sub croak {
		1750	$_[0]{_ae_croak} = $_[1];
		1751	$_[0]->send;
		1752	}
		1753
		1754	sub ready {
		1755	$_[0]{_ae_sent}
		1756	}
		1757
		1758	sub _wait {
		1759	$WAITING
		1760	and !$_[0]{_ae_sent}
		1761	and Carp::croak "AnyEvent::CondVar: recursive blocking wait detected";
		1762
		1763	local $WAITING = 1;
		1764	AnyEvent->one_event while !$_[0]{_ae_sent};
		1765	}
		1766
		1767	sub recv {
		1768	$_[0]->_wait;
		1769
		1770	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
		1771	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
		1772	}
		1773
		1774	sub cb {
		1775	my $cv = shift;
		1776
		1777	@_
		1778	and $cv->{_ae_cb} = shift
		1779	and $cv->{_ae_sent}
		1780	and (delete $cv->{_ae_cb})->($cv);
		1781
		1782	$cv->{_ae_cb}
		1783	}
		1784
		1785	sub begin {
		1786	++$_[0]{_ae_counter};
		1787	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
		1788	}
		1789
		1790	sub end {
		1791	return if --$_[0]{_ae_counter};
		1792	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		1793	}
		1794
		1795	# undocumented/compatibility with pre-3.4
		1796	*broadcast = \&send;
		1797	*wait = \&_wait;
		1798
		1799	=head1 ERROR AND EXCEPTION HANDLING
		1800
		1801	In general, AnyEvent does not do any error handling - it relies on the
		1802	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1803	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1804	checking of all AnyEvent methods, however, which is highly useful during
		1805	development.
		1806
		1807	As for exception handling (i.e. runtime errors and exceptions thrown while
		1808	executing a callback), this is not only highly event-loop specific, but
		1809	also not in any way wrapped by this module, as this is the job of the main
		1810	program.
		1811
		1812	The pure perl event loop simply re-throws the exception (usually
		1813	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1814	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1815	so on.
		1816
		1817	=head1 ENVIRONMENT VARIABLES
		1818
		1819	The following environment variables are used by this module or its
		1820	submodules.
		1821
		1822	Note that AnyEvent will remove I<all> environment variables starting with
		1823	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		1824	enabled.
		1825
		1826	=over 4
		1827
		1828	=item C<PERL_ANYEVENT_VERBOSE>
		1829
		1830	By default, AnyEvent will be completely silent except in fatal
		1831	conditions. You can set this environment variable to make AnyEvent more
		1832	talkative.
		1833
		1834	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1835	conditions, such as not being able to load the event model specified by
		1836	C<PERL_ANYEVENT_MODEL>.
		1837
		1838	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1839	model it chooses.
		1840
		1841	When set to C<8> or higher, then AnyEvent will report extra information on
		1842	which optional modules it loads and how it implements certain features.
		1843
		1844	=item C<PERL_ANYEVENT_STRICT>
		1845
		1846	AnyEvent does not do much argument checking by default, as thorough
		1847	argument checking is very costly. Setting this variable to a true value
		1848	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1849	check the arguments passed to most method calls. If it finds any problems,
		1850	it will croak.
		1851
		1852	In other words, enables "strict" mode.
		1853
		1854	Unlike C<use strict> (or it's modern cousin, C<< use L<common::sense>
		1855	>>, it is definitely recommended to keep it off in production. Keeping
		1856	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		1857	can be very useful, however.
		1858
		1859	=item C<PERL_ANYEVENT_MODEL>
		1860
		1861	This can be used to specify the event model to be used by AnyEvent, before
		1862	auto detection and -probing kicks in. It must be a string consisting
		1863	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1864	and the resulting module name is loaded and if the load was successful,
		1865	used as event model. If it fails to load AnyEvent will proceed with
		1866	auto detection and -probing.
		1867
		1868	This functionality might change in future versions.
		1869
		1870	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1871	could start your program like this:
		1872
		1873	PERL_ANYEVENT_MODEL=Perl perl ...
		1874
		1875	=item C<PERL_ANYEVENT_PROTOCOLS>
		1876
		1877	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1878	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1879	of auto probing).
		1880
		1881	Must be set to a comma-separated list of protocols or address families,
		1882	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1883	used, and preference will be given to protocols mentioned earlier in the
		1884	list.
		1885
		1886	This variable can effectively be used for denial-of-service attacks
		1887	against local programs (e.g. when setuid), although the impact is likely
		1888	small, as the program has to handle conenction and other failures anyways.
		1889
		1890	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1891	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1892	- only support IPv4, never try to resolve or contact IPv6
		1893	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1894	IPv6, but prefer IPv6 over IPv4.
		1895
		1896	=item C<PERL_ANYEVENT_EDNS0>
		1897
		1898	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1899	for DNS. This extension is generally useful to reduce DNS traffic, but
		1900	some (broken) firewalls drop such DNS packets, which is why it is off by
		1901	default.
		1902
		1903	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1904	EDNS0 in its DNS requests.
		1905
		1906	=item C<PERL_ANYEVENT_MAX_FORKS>
		1907
		1908	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1909	will create in parallel.
		1910
		1911	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		1912
		1913	The default value for the C<max_outstanding> parameter for the default DNS
		1914	resolver - this is the maximum number of parallel DNS requests that are
		1915	sent to the DNS server.
		1916
		1917	=item C<PERL_ANYEVENT_RESOLV_CONF>
		1918
		1919	The file to use instead of F</etc/resolv.conf> (or OS-specific
		1920	configuration) in the default resolver. When set to the empty string, no
		1921	default config will be used.
		1922
		1923	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		1924
		1925	When neither C<ca_file> nor C<ca_path> was specified during
		1926	L<AnyEvent::TLS> context creation, and either of these environment
		1927	variables exist, they will be used to specify CA certificate locations
		1928	instead of a system-dependent default.
		1929
		1930	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		1931
		1932	When these are set to C<1>, then the respective modules are not
		1933	loaded. Mostly good for testing AnyEvent itself.
		1934
		1935	=back
594		1936
595	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1937	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
596		1938
597	This is an advanced topic that you do not normally need to use AnyEvent in	1939	This is an advanced topic that you do not normally need to use AnyEvent in
598	a module. This section is only of use to event loop authors who want to	1940	a module. This section is only of use to event loop authors who want to
…		…
633	I<rxvt-unicode> also cheats a bit by not providing blocking access to	1975	I<rxvt-unicode> also cheats a bit by not providing blocking access to
634	condition variables: code blocking while waiting for a condition will	1976	condition variables: code blocking while waiting for a condition will
635	C<die>. This still works with most modules/usages, and blocking calls must	1977	C<die>. This still works with most modules/usages, and blocking calls must
636	not be done in an interactive application, so it makes sense.	1978	not be done in an interactive application, so it makes sense.
637		1979
638	=head1 ENVIRONMENT VARIABLES
639
640	The following environment variables are used by this module:
641
642	C<PERL_ANYEVENT_VERBOSE> when set to C<2> or higher, cause AnyEvent to
643	report to STDERR which event model it chooses.
644
645	=head1 EXAMPLE PROGRAM	1980	=head1 EXAMPLE PROGRAM
646		1981
647	The following program uses an IO watcher to read data from STDIN, a timer	1982	The following program uses an I/O watcher to read data from STDIN, a timer
648	to display a message once per second, and a condition variable to quit the	1983	to display a message once per second, and a condition variable to quit the
649	program when the user enters quit:	1984	program when the user enters quit:
650		1985
651	use AnyEvent;	1986	use AnyEvent;
652		1987
…		…
657	poll => 'r',	1992	poll => 'r',
658	cb => sub {	1993	cb => sub {
659	warn "io event <$_[0]>\n"; # will always output <r>	1994	warn "io event <$_[0]>\n"; # will always output <r>
660	chomp (my $input = <STDIN>); # read a line	1995	chomp (my $input = <STDIN>); # read a line
661	warn "read: $input\n"; # output what has been read	1996	warn "read: $input\n"; # output what has been read
662	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	1997	$cv->send if $input =~ /^q/i; # quit program if /^q/i
663	},	1998	},
664	);	1999	);
665		2000
666	my $time_watcher; # can only be used once
667
668	sub new_timer {
669	$timer = AnyEvent->timer (after => 1, cb => sub {	2001	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
670	warn "timeout\n"; # print 'timeout' about every second	2002	warn "timeout\n"; # print 'timeout' at most every second
671	&new_timer; # and restart the time
672	});	2003	});
673	}
674		2004
675	new_timer; # create first timer
676
677	$cv->wait; # wait until user enters /^q/i	2005	$cv->recv; # wait until user enters /^q/i
678		2006
679	=head1 REAL-WORLD EXAMPLE	2007	=head1 REAL-WORLD EXAMPLE
680		2008
681	Consider the L<Net::FCP> module. It features (among others) the following	2009	Consider the L<Net::FCP> module. It features (among others) the following
682	API calls, which are to freenet what HTTP GET requests are to http:	2010	API calls, which are to freenet what HTTP GET requests are to http:
…		…
732	syswrite $txn->{fh}, $txn->{request}	2060	syswrite $txn->{fh}, $txn->{request}
733	or die "connection or write error";	2061	or die "connection or write error";
734	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	2062	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
735		2063
736	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	2064	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
737	result and signals any possible waiters that the request ahs finished:	2065	result and signals any possible waiters that the request has finished:
738		2066
739	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	2067	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
740		2068
741	if (end-of-file or data complete) {	2069	if (end-of-file or data complete) {
742	$txn->{result} = $txn->{buf};	2070	$txn->{result} = $txn->{buf};
743	$txn->{finished}->broadcast;	2071	$txn->{finished}->send;
744	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	2072	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
745	}	2073	}
746		2074
747	The C<result> method, finally, just waits for the finished signal (if the	2075	The C<result> method, finally, just waits for the finished signal (if the
748	request was already finished, it doesn't wait, of course, and returns the	2076	request was already finished, it doesn't wait, of course, and returns the
749	data:	2077	data:
750		2078
751	$txn->{finished}->wait;	2079	$txn->{finished}->recv;
752	return $txn->{result};	2080	return $txn->{result};
753		2081
754	The actual code goes further and collects all errors (C<die>s, exceptions)	2082	The actual code goes further and collects all errors (C<die>s, exceptions)
755	that occured during request processing. The C<result> method detects	2083	that occurred during request processing. The C<result> method detects
756	whether an exception as thrown (it is stored inside the $txn object)	2084	whether an exception as thrown (it is stored inside the $txn object)
757	and just throws the exception, which means connection errors and other	2085	and just throws the exception, which means connection errors and other
758	problems get reported tot he code that tries to use the result, not in a	2086	problems get reported to the code that tries to use the result, not in a
759	random callback.	2087	random callback.
760		2088
761	All of this enables the following usage styles:	2089	All of this enables the following usage styles:
762		2090
763	1. Blocking:	2091	1. Blocking:
…		…
791		2119
792	my $quit = AnyEvent->condvar;	2120	my $quit = AnyEvent->condvar;
793		2121
794	$fcp->txn_client_get ($url)->cb (sub {	2122	$fcp->txn_client_get ($url)->cb (sub {
795	...	2123	...
796	$quit->broadcast;	2124	$quit->send;
797	});	2125	});
798		2126
799	$quit->wait;	2127	$quit->recv;
		2128
		2129
		2130	=head1 BENCHMARKS
		2131
		2132	To give you an idea of the performance and overheads that AnyEvent adds
		2133	over the event loops themselves and to give you an impression of the speed
		2134	of various event loops I prepared some benchmarks.
		2135
		2136	=head2 BENCHMARKING ANYEVENT OVERHEAD
		2137
		2138	Here is a benchmark of various supported event models used natively and
		2139	through AnyEvent. The benchmark creates a lot of timers (with a zero
		2140	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
		2141	which it is), lets them fire exactly once and destroys them again.
		2142
		2143	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
		2144	distribution. It uses the L<AE> interface, which makes a real difference
		2145	for the EV and Perl backends only.
		2146
		2147	=head3 Explanation of the columns
		2148
		2149	I<watcher> is the number of event watchers created/destroyed. Since
		2150	different event models feature vastly different performances, each event
		2151	loop was given a number of watchers so that overall runtime is acceptable
		2152	and similar between tested event loop (and keep them from crashing): Glib
		2153	would probably take thousands of years if asked to process the same number
		2154	of watchers as EV in this benchmark.
		2155
		2156	I<bytes> is the number of bytes (as measured by the resident set size,
		2157	RSS) consumed by each watcher. This method of measuring captures both C
		2158	and Perl-based overheads.
		2159
		2160	I<create> is the time, in microseconds (millionths of seconds), that it
		2161	takes to create a single watcher. The callback is a closure shared between
		2162	all watchers, to avoid adding memory overhead. That means closure creation
		2163	and memory usage is not included in the figures.
		2164
		2165	I<invoke> is the time, in microseconds, used to invoke a simple
		2166	callback. The callback simply counts down a Perl variable and after it was
		2167	invoked "watcher" times, it would C<< ->send >> a condvar once to
		2168	signal the end of this phase.
		2169
		2170	I<destroy> is the time, in microseconds, that it takes to destroy a single
		2171	watcher.
		2172
		2173	=head3 Results
		2174
		2175	name watchers bytes create invoke destroy comment
		2176	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
		2177	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
		2178	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
		2179	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
		2180	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
		2181	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
		2182	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
		2183	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
		2184	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
		2185	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
		2186	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
		2187	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
		2188
		2189	=head3 Discussion
		2190
		2191	The benchmark does I<not> measure scalability of the event loop very
		2192	well. For example, a select-based event loop (such as the pure perl one)
		2193	can never compete with an event loop that uses epoll when the number of
		2194	file descriptors grows high. In this benchmark, all events become ready at
		2195	the same time, so select/poll-based implementations get an unnatural speed
		2196	boost.
		2197
		2198	Also, note that the number of watchers usually has a nonlinear effect on
		2199	overall speed, that is, creating twice as many watchers doesn't take twice
		2200	the time - usually it takes longer. This puts event loops tested with a
		2201	higher number of watchers at a disadvantage.
		2202
		2203	To put the range of results into perspective, consider that on the
		2204	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		2205	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		2206	cycles with POE.
		2207
		2208	C<EV> is the sole leader regarding speed and memory use, which are both
		2209	maximal/minimal, respectively. When using the L<AE> API there is zero
		2210	overhead (when going through the AnyEvent API create is about 5-6 times
		2211	slower, with other times being equal, so still uses far less memory than
		2212	any other event loop and is still faster than Event natively).
		2213
		2214	The pure perl implementation is hit in a few sweet spots (both the
		2215	constant timeout and the use of a single fd hit optimisations in the perl
		2216	interpreter and the backend itself). Nevertheless this shows that it
		2217	adds very little overhead in itself. Like any select-based backend its
		2218	performance becomes really bad with lots of file descriptors (and few of
		2219	them active), of course, but this was not subject of this benchmark.
		2220
		2221	The C<Event> module has a relatively high setup and callback invocation
		2222	cost, but overall scores in on the third place.
		2223
		2224	C<IO::Async> performs admirably well, about on par with C<Event>, even
		2225	when using its pure perl backend.
		2226
		2227	C<Glib>'s memory usage is quite a bit higher, but it features a
		2228	faster callback invocation and overall ends up in the same class as
		2229	C<Event>. However, Glib scales extremely badly, doubling the number of
		2230	watchers increases the processing time by more than a factor of four,
		2231	making it completely unusable when using larger numbers of watchers
		2232	(note that only a single file descriptor was used in the benchmark, so
		2233	inefficiencies of C<poll> do not account for this).
		2234
		2235	The C<Tk> adaptor works relatively well. The fact that it crashes with
		2236	more than 2000 watchers is a big setback, however, as correctness takes
		2237	precedence over speed. Nevertheless, its performance is surprising, as the
		2238	file descriptor is dup()ed for each watcher. This shows that the dup()
		2239	employed by some adaptors is not a big performance issue (it does incur a
		2240	hidden memory cost inside the kernel which is not reflected in the figures
		2241	above).
		2242
		2243	C<POE>, regardless of underlying event loop (whether using its pure perl
		2244	select-based backend or the Event module, the POE-EV backend couldn't
		2245	be tested because it wasn't working) shows abysmal performance and
		2246	memory usage with AnyEvent: Watchers use almost 30 times as much memory
		2247	as EV watchers, and 10 times as much memory as Event (the high memory
		2248	requirements are caused by requiring a session for each watcher). Watcher
		2249	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		2250	implementation.
		2251
		2252	The design of the POE adaptor class in AnyEvent can not really account
		2253	for the performance issues, though, as session creation overhead is
		2254	small compared to execution of the state machine, which is coded pretty
		2255	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		2256	using multiple sessions is not a good approach, especially regarding
		2257	memory usage, even the author of POE could not come up with a faster
		2258	design).
		2259
		2260	=head3 Summary
		2261
		2262	=over 4
		2263
		2264	=item * Using EV through AnyEvent is faster than any other event loop
		2265	(even when used without AnyEvent), but most event loops have acceptable
		2266	performance with or without AnyEvent.
		2267
		2268	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
		2269	the actual event loop, only with extremely fast event loops such as EV
		2270	adds AnyEvent significant overhead.
		2271
		2272	=item * You should avoid POE like the plague if you want performance or
		2273	reasonable memory usage.
		2274
		2275	=back
		2276
		2277	=head2 BENCHMARKING THE LARGE SERVER CASE
		2278
		2279	This benchmark actually benchmarks the event loop itself. It works by
		2280	creating a number of "servers": each server consists of a socket pair, a
		2281	timeout watcher that gets reset on activity (but never fires), and an I/O
		2282	watcher waiting for input on one side of the socket. Each time the socket
		2283	watcher reads a byte it will write that byte to a random other "server".
		2284
		2285	The effect is that there will be a lot of I/O watchers, only part of which
		2286	are active at any one point (so there is a constant number of active
		2287	fds for each loop iteration, but which fds these are is random). The
		2288	timeout is reset each time something is read because that reflects how
		2289	most timeouts work (and puts extra pressure on the event loops).
		2290
		2291	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
		2292	(1%) are active. This mirrors the activity of large servers with many
		2293	connections, most of which are idle at any one point in time.
		2294
		2295	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		2296	distribution. It uses the L<AE> interface, which makes a real difference
		2297	for the EV and Perl backends only.
		2298
		2299	=head3 Explanation of the columns
		2300
		2301	I<sockets> is the number of sockets, and twice the number of "servers" (as
		2302	each server has a read and write socket end).
		2303
		2304	I<create> is the time it takes to create a socket pair (which is
		2305	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		2306
		2307	I<request>, the most important value, is the time it takes to handle a
		2308	single "request", that is, reading the token from the pipe and forwarding
		2309	it to another server. This includes deleting the old timeout and creating
		2310	a new one that moves the timeout into the future.
		2311
		2312	=head3 Results
		2313
		2314	name sockets create request
		2315	EV 20000 62.66 7.99
		2316	Perl 20000 68.32 32.64
		2317	IOAsync 20000 174.06 101.15 epoll
		2318	IOAsync 20000 174.67 610.84 poll
		2319	Event 20000 202.69 242.91
		2320	Glib 20000 557.01 1689.52
		2321	POE 20000 341.54 12086.32 uses POE::Loop::Event
		2322
		2323	=head3 Discussion
		2324
		2325	This benchmark I<does> measure scalability and overall performance of the
		2326	particular event loop.
		2327
		2328	EV is again fastest. Since it is using epoll on my system, the setup time
		2329	is relatively high, though.
		2330
		2331	Perl surprisingly comes second. It is much faster than the C-based event
		2332	loops Event and Glib.
		2333
		2334	IO::Async performs very well when using its epoll backend, and still quite
		2335	good compared to Glib when using its pure perl backend.
		2336
		2337	Event suffers from high setup time as well (look at its code and you will
		2338	understand why). Callback invocation also has a high overhead compared to
		2339	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		2340	uses select or poll in basically all documented configurations.
		2341
		2342	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		2343	clearly fails to perform with many filehandles or in busy servers.
		2344
		2345	POE is still completely out of the picture, taking over 1000 times as long
		2346	as EV, and over 100 times as long as the Perl implementation, even though
		2347	it uses a C-based event loop in this case.
		2348
		2349	=head3 Summary
		2350
		2351	=over 4
		2352
		2353	=item * The pure perl implementation performs extremely well.
		2354
		2355	=item * Avoid Glib or POE in large projects where performance matters.
		2356
		2357	=back
		2358
		2359	=head2 BENCHMARKING SMALL SERVERS
		2360
		2361	While event loops should scale (and select-based ones do not...) even to
		2362	large servers, most programs we (or I :) actually write have only a few
		2363	I/O watchers.
		2364
		2365	In this benchmark, I use the same benchmark program as in the large server
		2366	case, but it uses only eight "servers", of which three are active at any
		2367	one time. This should reflect performance for a small server relatively
		2368	well.
		2369
		2370	The columns are identical to the previous table.
		2371
		2372	=head3 Results
		2373
		2374	name sockets create request
		2375	EV 16 20.00 6.54
		2376	Perl 16 25.75 12.62
		2377	Event 16 81.27 35.86
		2378	Glib 16 32.63 15.48
		2379	POE 16 261.87 276.28 uses POE::Loop::Event
		2380
		2381	=head3 Discussion
		2382
		2383	The benchmark tries to test the performance of a typical small
		2384	server. While knowing how various event loops perform is interesting, keep
		2385	in mind that their overhead in this case is usually not as important, due
		2386	to the small absolute number of watchers (that is, you need efficiency and
		2387	speed most when you have lots of watchers, not when you only have a few of
		2388	them).
		2389
		2390	EV is again fastest.
		2391
		2392	Perl again comes second. It is noticeably faster than the C-based event
		2393	loops Event and Glib, although the difference is too small to really
		2394	matter.
		2395
		2396	POE also performs much better in this case, but is is still far behind the
		2397	others.
		2398
		2399	=head3 Summary
		2400
		2401	=over 4
		2402
		2403	=item * C-based event loops perform very well with small number of
		2404	watchers, as the management overhead dominates.
		2405
		2406	=back
		2407
		2408	=head2 THE IO::Lambda BENCHMARK
		2409
		2410	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2411	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2412	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2413	shouldn't come as a surprise to anybody). As such, the benchmark is
		2414	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2415	very optimal. But how would AnyEvent compare when used without the extra
		2416	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2417
		2418	The benchmark itself creates an echo-server, and then, for 500 times,
		2419	connects to the echo server, sends a line, waits for the reply, and then
		2420	creates the next connection. This is a rather bad benchmark, as it doesn't
		2421	test the efficiency of the framework or much non-blocking I/O, but it is a
		2422	benchmark nevertheless.
		2423
		2424	name runtime
		2425	Lambda/select 0.330 sec
		2426	+ optimized 0.122 sec
		2427	Lambda/AnyEvent 0.327 sec
		2428	+ optimized 0.138 sec
		2429	Raw sockets/select 0.077 sec
		2430	POE/select, components 0.662 sec
		2431	POE/select, raw sockets 0.226 sec
		2432	POE/select, optimized 0.404 sec
		2433
		2434	AnyEvent/select/nb 0.085 sec
		2435	AnyEvent/EV/nb 0.068 sec
		2436	+state machine 0.134 sec
		2437
		2438	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2439	benchmarks actually make blocking connects and use 100% blocking I/O,
		2440	defeating the purpose of an event-based solution. All of the newly
		2441	written AnyEvent benchmarks use 100% non-blocking connects (using
		2442	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2443	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2444	generally require a lot more bookkeeping and event handling than blocking
		2445	connects (which involve a single syscall only).
		2446
		2447	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2448	offers similar expressive power as POE and IO::Lambda, using conventional
		2449	Perl syntax. This means that both the echo server and the client are 100%
		2450	non-blocking, further placing it at a disadvantage.
		2451
		2452	As you can see, the AnyEvent + EV combination even beats the
		2453	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2454	backend easily beats IO::Lambda and POE.
		2455
		2456	And even the 100% non-blocking version written using the high-level (and
		2457	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda
		2458	higher level ("unoptimised") abstractions by a large margin, even though
		2459	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
		2460
		2461	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2462	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2463	part of the IO::Lambda distribution and were used without any changes.
		2464
		2465
		2466	=head1 SIGNALS
		2467
		2468	AnyEvent currently installs handlers for these signals:
		2469
		2470	=over 4
		2471
		2472	=item SIGCHLD
		2473
		2474	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2475	emulation for event loops that do not support them natively. Also, some
		2476	event loops install a similar handler.
		2477
		2478	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2479	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2480
		2481	=item SIGPIPE
		2482
		2483	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2484	when AnyEvent gets loaded.
		2485
		2486	The rationale for this is that AnyEvent users usually do not really depend
		2487	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2488	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2489	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2490	some random socket.
		2491
		2492	The rationale for installing a no-op handler as opposed to ignoring it is
		2493	that this way, the handler will be restored to defaults on exec.
		2494
		2495	Feel free to install your own handler, or reset it to defaults.
		2496
		2497	=back
		2498
		2499	=cut
		2500
		2501	undef $SIG{CHLD}
		2502	if $SIG{CHLD} eq 'IGNORE';
		2503
		2504	$SIG{PIPE} = sub { }
		2505	unless defined $SIG{PIPE};
		2506
		2507	=head1 RECOMMENDED/OPTIONAL MODULES
		2508
		2509	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2510	it's built-in modules) are required to use it.
		2511
		2512	That does not mean that AnyEvent won't take advantage of some additional
		2513	modules if they are installed.
		2514
		2515	This section explains which additional modules will be used, and how they
		2516	affect AnyEvent's operation.
		2517
		2518	=over 4
		2519
		2520	=item L<Async::Interrupt>
		2521
		2522	This slightly arcane module is used to implement fast signal handling: To
		2523	my knowledge, there is no way to do completely race-free and quick
		2524	signal handling in pure perl. To ensure that signals still get
		2525	delivered, AnyEvent will start an interval timer to wake up perl (and
		2526	catch the signals) with some delay (default is 10 seconds, look for
		2527	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2528
		2529	If this module is available, then it will be used to implement signal
		2530	catching, which means that signals will not be delayed, and the event loop
		2531	will not be interrupted regularly, which is more efficient (and good for
		2532	battery life on laptops).
		2533
		2534	This affects not just the pure-perl event loop, but also other event loops
		2535	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2536
		2537	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2538	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2539	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2540	does nothing for those backends.
		2541
		2542	=item L<EV>
		2543
		2544	This module isn't really "optional", as it is simply one of the backend
		2545	event loops that AnyEvent can use. However, it is simply the best event
		2546	loop available in terms of features, speed and stability: It supports
		2547	the AnyEvent API optimally, implements all the watcher types in XS, does
		2548	automatic timer adjustments even when no monotonic clock is available,
		2549	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2550	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2551	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2552
		2553	If you only use backends that rely on another event loop (e.g. C<Tk>),
		2554	then this module will do nothing for you.
		2555
		2556	=item L<Guard>
		2557
		2558	The guard module, when used, will be used to implement
		2559	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2560	lot less memory), but otherwise doesn't affect guard operation much. It is
		2561	purely used for performance.
		2562
		2563	=item L<JSON> and L<JSON::XS>
		2564
		2565	One of these modules is required when you want to read or write JSON data
		2566	via L<AnyEvent::Handle>. L<JSON> is also written in pure-perl, but can take
		2567	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2568
		2569	=item L<Net::SSLeay>
		2570
		2571	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2572	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2573	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2574
		2575	=item L<Time::HiRes>
		2576
		2577	This module is part of perl since release 5.008. It will be used when the
		2578	chosen event library does not come with a timing source on it's own. The
		2579	pure-perl event loop (L<AnyEvent::Impl::Perl>) will additionally use it to
		2580	try to use a monotonic clock for timing stability.
		2581
		2582	=back
		2583
		2584
		2585	=head1 FORK
		2586
		2587	Most event libraries are not fork-safe. The ones who are usually are
		2588	because they rely on inefficient but fork-safe C<select> or C<poll> calls
		2589	- higher performance APIs such as BSD's kqueue or the dreaded Linux epoll
		2590	are usually badly thought-out hacks that are incompatible with fork in
		2591	one way or another. Only L<EV> is fully fork-aware and ensures that you
		2592	continue event-processing in both parent and child (or both, if you know
		2593	what you are doing).
		2594
		2595	This means that, in general, you cannot fork and do event processing in
		2596	the child if the event library was initialised before the fork (which
		2597	usually happens when the first AnyEvent watcher is created, or the library
		2598	is loaded).
		2599
		2600	If you have to fork, you must either do so I<before> creating your first
		2601	watcher OR you must not use AnyEvent at all in the child OR you must do
		2602	something completely out of the scope of AnyEvent.
		2603
		2604	The problem of doing event processing in the parent I<and> the child
		2605	is much more complicated: even for backends that I<are> fork-aware or
		2606	fork-safe, their behaviour is not usually what you want: fork clones all
		2607	watchers, that means all timers, I/O watchers etc. are active in both
		2608	parent and child, which is almost never what you want. USing C<exec>
		2609	to start worker children from some kind of manage rprocess is usually
		2610	preferred, because it is much easier and cleaner, at the expense of having
		2611	to have another binary.
		2612
		2613
		2614	=head1 SECURITY CONSIDERATIONS
		2615
		2616	AnyEvent can be forced to load any event model via
		2617	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
		2618	execute arbitrary code or directly gain access, it can easily be used to
		2619	make the program hang or malfunction in subtle ways, as AnyEvent watchers
		2620	will not be active when the program uses a different event model than
		2621	specified in the variable.
		2622
		2623	You can make AnyEvent completely ignore this variable by deleting it
		2624	before the first watcher gets created, e.g. with a C<BEGIN> block:
		2625
		2626	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
		2627
		2628	use AnyEvent;
		2629
		2630	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		2631	be used to probe what backend is used and gain other information (which is
		2632	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2633	$ENV{PERL_ANYEVENT_STRICT}.
		2634
		2635	Note that AnyEvent will remove I<all> environment variables starting with
		2636	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2637	enabled.
		2638
		2639
		2640	=head1 BUGS
		2641
		2642	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2643	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2644	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2645	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2646	pronounced).
		2647
800		2648
801	=head1 SEE ALSO	2649	=head1 SEE ALSO
802		2650
803	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	2651	Utility functions: L<AnyEvent::Util>.
804	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>.
805		2652
806	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	2653	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
		2654	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
		2655
807	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>,	2656	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
808	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>.	2657	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
		2658	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
		2659	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>, L<Anyevent::Impl::Irssi>.
809		2660
		2661	Non-blocking file handles, sockets, TCP clients and
		2662	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
		2663
		2664	Asynchronous DNS: L<AnyEvent::DNS>.
		2665
		2666	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>,
		2667	L<Coro::Event>,
		2668
810	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	2669	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::XMPP>,
		2670	L<AnyEvent::HTTP>.
811		2671
812	=head1	2672
		2673	=head1 AUTHOR
		2674
		2675	Marc Lehmann <schmorp@schmorp.de>
		2676	http://home.schmorp.de/
813		2677
814	=cut	2678	=cut
815		2679
816	1	2680	1
817		2681

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