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Revision 1.310 by root, Tue Jan 5 10:45:25 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, Event::Lib, Qt, POE - various supported event loops	5	EV, Event, Glib, Tk, Perl, Event::Lib, Irssi, rxvt-unicode, IO::Async, Qt
		6	and POE are various supported event loops/environments.
6		7
7	=head1 SYNOPSIS	8	=head1 SYNOPSIS
8		9
9	use AnyEvent;	10	use AnyEvent;
10		11
		12	# file descriptor readable
11	my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub {	13	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
		14
		15	# one-shot or repeating timers
		16	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
		17	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...
		18
		19	print AnyEvent->now; # prints current event loop time
		20	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
		21
		22	# POSIX signal
		23	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
		24
		25	# child process exit
		26	my $w = AnyEvent->child (pid => $pid, cb => sub {
		27	my ($pid, $status) = @_;
12	...	28	...
13	});	29	});
14		30
15	my $w = AnyEvent->timer (after => $seconds, cb => sub {	31	# called when event loop idle (if applicable)
16	...	32	my $w = AnyEvent->idle (cb => sub { ... });
17	});
18		33
19	my $w = AnyEvent->condvar; # stores whether a condition was flagged	34	my $w = AnyEvent->condvar; # stores whether a condition was flagged
		35	$w->send; # wake up current and all future recv's
20	$w->wait; # enters "main loop" till $condvar gets ->broadcast	36	$w->recv; # enters "main loop" till $condvar gets ->send
21	$w->broadcast; # wake up current and all future wait's	37	# use a condvar in callback mode:
		38	$w->cb (sub { $_[0]->recv });
		39
		40	=head1 INTRODUCTION/TUTORIAL
		41
		42	This manpage is mainly a reference manual. If you are interested
		43	in a tutorial or some gentle introduction, have a look at the
		44	L<AnyEvent::Intro> manpage.
		45
		46	=head1 SUPPORT
		47
		48	There is a mailinglist for discussing all things AnyEvent, and an IRC
		49	channel, too.
		50
		51	See the AnyEvent project page at the B<Schmorpforge Ta-Sa Software
		52	Repository>, at L<http://anyevent.schmorp.de>, for more info.
22		53
23	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)	54	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
24		55
25	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	56	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
26	nowadays. So what is different about AnyEvent?	57	nowadays. So what is different about AnyEvent?
27		58
28	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of	59	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
29	policy> and AnyEvent is I<small and efficient>.	60	policy> and AnyEvent is I<small and efficient>.
30		61
31	First and foremost, I<AnyEvent is not an event model> itself, it only	62	First and foremost, I<AnyEvent is not an event model> itself, it only
32	interfaces to whatever event model the main program happens to use in a	63	interfaces to whatever event model the main program happens to use, in a
33	pragmatic way. For event models and certain classes of immortals alike,	64	pragmatic way. For event models and certain classes of immortals alike,
34	the statement "there can only be one" is a bitter reality: In general,	65	the statement "there can only be one" is a bitter reality: In general,
35	only one event loop can be active at the same time in a process. AnyEvent	66	only one event loop can be active at the same time in a process. AnyEvent
36	helps hiding the differences between those event loops.	67	cannot change this, but it can hide the differences between those event
		68	loops.
37		69
38	The goal of AnyEvent is to offer module authors the ability to do event	70	The goal of AnyEvent is to offer module authors the ability to do event
39	programming (waiting for I/O or timer events) without subscribing to a	71	programming (waiting for I/O or timer events) without subscribing to a
40	religion, a way of living, and most importantly: without forcing your	72	religion, a way of living, and most importantly: without forcing your
41	module users into the same thing by forcing them to use the same event	73	module users into the same thing by forcing them to use the same event
42	model you use.	74	model you use.
43		75
44	For modules like POE or IO::Async (which is a total misnomer as it is	76	For modules like POE or IO::Async (which is a total misnomer as it is
45	actually doing all I/O I<synchronously>...), using them in your module is	77	actually doing all I/O I<synchronously>...), using them in your module is
46	like joining a cult: After you joined, you are dependent on them and you	78	like joining a cult: After you joined, you are dependent on them and you
47	cannot use anything else, as it is simply incompatible to everything that	79	cannot use anything else, as they are simply incompatible to everything
48	isn't itself. What's worse, all the potential users of your module are	80	that isn't them. What's worse, all the potential users of your
49	I<also> forced to use the same event loop you use.	81	module are I<also> forced to use the same event loop you use.
50		82
51	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	83	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
52	fine. AnyEvent + Tk works fine etc. etc. but none of these work together	84	fine. AnyEvent + Tk works fine etc. etc. but none of these work together
53	with the rest: POE + IO::Async? no go. Tk + Event? no go. Again: if	85	with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if
54	your module uses one of those, every user of your module has to use it,	86	your module uses one of those, every user of your module has to use it,
55	too. But if your module uses AnyEvent, it works transparently with all	87	too. But if your module uses AnyEvent, it works transparently with all
56	event models it supports (including stuff like POE and IO::Async, as long	88	event models it supports (including stuff like IO::Async, as long as those
57	as those use one of the supported event loops. It is trivial to add new	89	use one of the supported event loops. It is trivial to add new event loops
58	event loops to AnyEvent, too, so it is future-proof).	90	to AnyEvent, too, so it is future-proof).
59		91
60	In addition to being free of having to use I<the one and only true event	92	In addition to being free of having to use I<the one and only true event
61	model>, AnyEvent also is free of bloat and policy: with POE or similar	93	model>, AnyEvent also is free of bloat and policy: with POE or similar
62	modules, you get an enourmous amount of code and strict rules you have to	94	modules, you get an enormous amount of code and strict rules you have to
63	follow. AnyEvent, on the other hand, is lean and up to the point, by only	95	follow. AnyEvent, on the other hand, is lean and up to the point, by only
64	offering the functionality that is necessary, in as thin as a wrapper as	96	offering the functionality that is necessary, in as thin as a wrapper as
65	technically possible.	97	technically possible.
66		98
		99	Of course, AnyEvent comes with a big (and fully optional!) toolbox
		100	of useful functionality, such as an asynchronous DNS resolver, 100%
		101	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
		102	such as Windows) and lots of real-world knowledge and workarounds for
		103	platform bugs and differences.
		104
67	Of course, if you want lots of policy (this can arguably be somewhat	105	Now, if you I<do want> lots of policy (this can arguably be somewhat
68	useful) and you want to force your users to use the one and only event	106	useful) and you want to force your users to use the one and only event
69	model, you should I<not> use this module.	107	model, you should I<not> use this module.
70
71		108
72	=head1 DESCRIPTION	109	=head1 DESCRIPTION
73		110
74	L<AnyEvent> provides an identical interface to multiple event loops. This	111	L<AnyEvent> provides an identical interface to multiple event loops. This
75	allows module authors to utilise an event loop without forcing module	112	allows module authors to utilise an event loop without forcing module
…		…
79	The interface itself is vaguely similar, but not identical to the L<Event>	116	The interface itself is vaguely similar, but not identical to the L<Event>
80	module.	117	module.
81		118
82	During the first call of any watcher-creation method, the module tries	119	During the first call of any watcher-creation method, the module tries
83	to detect the currently loaded event loop by probing whether one of the	120	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>,	121	following modules is already loaded: L<EV>,
85	L<Event>, L<Glib>, L<Tk>, L<AnyEvent::Impl::Perl>, L<Event::Lib>, L<Qt>,	122	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,
86	L<POE>. The first one found is used. If none are found, the module tries	123	L<POE>. The first one found is used. If none are found, the module tries
87	to load these modules (excluding Event::Lib, Qt and POE as the pure perl	124	to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl
88	adaptor should always succeed) in the order given. The first one that can	125	adaptor should always succeed) in the order given. The first one that can
89	be successfully loaded will be used. If, after this, still none could be	126	be successfully loaded will be used. If, after this, still none could be
90	found, AnyEvent will fall back to a pure-perl event loop, which is not	127	found, AnyEvent will fall back to a pure-perl event loop, which is not
91	very efficient, but should work everywhere.	128	very efficient, but should work everywhere.
92		129
…		…
103	starts using it, all bets are off. Maybe you should tell their authors to	140	starts using it, all bets are off. Maybe you should tell their authors to
104	use AnyEvent so their modules work together with others seamlessly...	141	use AnyEvent so their modules work together with others seamlessly...
105		142
106	The pure-perl implementation of AnyEvent is called	143	The pure-perl implementation of AnyEvent is called
107	C<AnyEvent::Impl::Perl>. Like other event modules you can load it	144	C<AnyEvent::Impl::Perl>. Like other event modules you can load it
108	explicitly.	145	explicitly and enjoy the high availability of that event loop :)
109		146
110	=head1 WATCHERS	147	=head1 WATCHERS
111		148
112	AnyEvent has the central concept of a I<watcher>, which is an object that	149	AnyEvent has the central concept of a I<watcher>, which is an object that
113	stores relevant data for each kind of event you are waiting for, such as	150	stores relevant data for each kind of event you are waiting for, such as
114	the callback to call, the filehandle to watch, etc.	151	the callback to call, the file handle to watch, etc.
115		152
116	These watchers are normal Perl objects with normal Perl lifetime. After	153	These watchers are normal Perl objects with normal Perl lifetime. After
117	creating a watcher it will immediately "watch" for events and invoke the	154	creating a watcher it will immediately "watch" for events and invoke the
118	callback when the event occurs (of course, only when the event model	155	callback when the event occurs (of course, only when the event model
119	is in control).	156	is in control).
120		157
		158	Note that B<callbacks must not permanently change global variables>
		159	potentially in use by the event loop (such as C<$_> or C<$[>) and that B<<
		160	callbacks must not C<die> >>. The former is good programming practise in
		161	Perl and the latter stems from the fact that exception handling differs
		162	widely between event loops.
		163
121	To disable the watcher you have to destroy it (e.g. by setting the	164	To disable the watcher you have to destroy it (e.g. by setting the
122	variable you store it in to C<undef> or otherwise deleting all references	165	variable you store it in to C<undef> or otherwise deleting all references
123	to it).	166	to it).
124		167
125	All watchers are created by calling a method on the C<AnyEvent> class.	168	All watchers are created by calling a method on the C<AnyEvent> class.
…		…
127	Many watchers either are used with "recursion" (repeating timers for	170	Many watchers either are used with "recursion" (repeating timers for
128	example), or need to refer to their watcher object in other ways.	171	example), or need to refer to their watcher object in other ways.
129		172
130	An any way to achieve that is this pattern:	173	An any way to achieve that is this pattern:
131		174
132	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	175	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
133	# you can use $w here, for example to undef it	176	# you can use $w here, for example to undef it
134	undef $w;	177	undef $w;
135	});	178	});
136		179
137	Note that C<my $w; $w => combination. This is necessary because in Perl,	180	Note that C<my $w; $w => combination. This is necessary because in Perl,
138	my variables are only visible after the statement in which they are	181	my variables are only visible after the statement in which they are
139	declared.	182	declared.
140		183
141	=head2 IO WATCHERS	184	=head2 I/O WATCHERS
		185
		186	$w = AnyEvent->io (
		187	fh => <filehandle_or_fileno>,
		188	poll => <"r" or "w">,
		189	cb => <callback>,
		190	);
142		191
143	You can create an I/O watcher by calling the C<< AnyEvent->io >> method	192	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
144	with the following mandatory key-value pairs as arguments:	193	with the following mandatory key-value pairs as arguments:
145		194
146	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch for	195	C<fh> is the Perl I<file handle> (or a naked file descriptor) to watch
		196	for events (AnyEvent might or might not keep a reference to this file
		197	handle). Note that only file handles pointing to things for which
		198	non-blocking operation makes sense are allowed. This includes sockets,
		199	most character devices, pipes, fifos and so on, but not for example files
		200	or block devices.
		201
147	events. C<poll> must be a string that is either C<r> or C<w>, which	202	C<poll> must be a string that is either C<r> or C<w>, which creates a
148	creates a watcher waiting for "r"eadable or "w"ritable events,	203	watcher waiting for "r"eadable or "w"ritable events, respectively.
		204
149	respectively. C<cb> is the callback to invoke each time the file handle	205	C<cb> is the callback to invoke each time the file handle becomes ready.
150	becomes ready.
151		206
152	As long as the I/O watcher exists it will keep the file descriptor or a	207	Although the callback might get passed parameters, their value and
153	copy of it alive/open.	208	presence is undefined and you cannot rely on them. Portable AnyEvent
		209	callbacks cannot use arguments passed to I/O watcher callbacks.
154		210
		211	The I/O watcher might use the underlying file descriptor or a copy of it.
155	It is not allowed to close a file handle as long as any watcher is active	212	You must not close a file handle as long as any watcher is active on the
156	on the underlying file descriptor.	213	underlying file descriptor.
157		214
158	Some event loops issue spurious readyness notifications, so you should	215	Some event loops issue spurious readyness notifications, so you should
159	always use non-blocking calls when reading/writing from/to your file	216	always use non-blocking calls when reading/writing from/to your file
160	handles.	217	handles.
161		218
162	Example:
163
164	# wait for readability of STDIN, then read a line and disable the watcher	219	Example: wait for readability of STDIN, then read a line and disable the
		220	watcher.
		221
165	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	222	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
166	chomp (my $input = <STDIN>);	223	chomp (my $input = <STDIN>);
167	warn "read: $input\n";	224	warn "read: $input\n";
168	undef $w;	225	undef $w;
169	});	226	});
170		227
171	=head2 TIME WATCHERS	228	=head2 TIME WATCHERS
172		229
		230	$w = AnyEvent->timer (after => <seconds>, cb => <callback>);
		231
		232	$w = AnyEvent->timer (
		233	after => <fractional_seconds>,
		234	interval => <fractional_seconds>,
		235	cb => <callback>,
		236	);
		237
173	You can create a time watcher by calling the C<< AnyEvent->timer >>	238	You can create a time watcher by calling the C<< AnyEvent->timer >>
174	method with the following mandatory arguments:	239	method with the following mandatory arguments:
175		240
176	C<after> specifies after how many seconds (fractional values are	241	C<after> specifies after how many seconds (fractional values are
177	supported) should the timer activate. C<cb> the callback to invoke in that	242	supported) the callback should be invoked. C<cb> is the callback to invoke
178	case.	243	in that case.
179		244
180	The timer callback will be invoked at most once: if you want a repeating	245	Although the callback might get passed parameters, their value and
181	timer you have to create a new watcher (this is a limitation by both Tk	246	presence is undefined and you cannot rely on them. Portable AnyEvent
182	and Glib).	247	callbacks cannot use arguments passed to time watcher callbacks.
183		248
184	Example:	249	The callback will normally be invoked once only. If you specify another
		250	parameter, C<interval>, as a strictly positive number (> 0), then the
		251	callback will be invoked regularly at that interval (in fractional
		252	seconds) after the first invocation. If C<interval> is specified with a
		253	false value, then it is treated as if it were missing.
185		254
		255	The callback will be rescheduled before invoking the callback, but no
		256	attempt is done to avoid timer drift in most backends, so the interval is
		257	only approximate.
		258
186	# fire an event after 7.7 seconds	259	Example: fire an event after 7.7 seconds.
		260
187	my $w = AnyEvent->timer (after => 7.7, cb => sub {	261	my $w = AnyEvent->timer (after => 7.7, cb => sub {
188	warn "timeout\n";	262	warn "timeout\n";
189	});	263	});
190		264
191	# to cancel the timer:	265	# to cancel the timer:
192	undef $w;	266	undef $w;
193		267
194	Example 2:
195
196	# fire an event after 0.5 seconds, then roughly every second	268	Example 2: fire an event after 0.5 seconds, then roughly every second.
197	my $w;
198		269
199	my $cb = sub {
200	# cancel the old timer while creating a new one
201	$w = AnyEvent->timer (after => 1, cb => $cb);	270	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		271	warn "timeout\n";
202	};	272	};
203
204	# start the "loop" by creating the first watcher
205	$w = AnyEvent->timer (after => 0.5, cb => $cb);
206		273
207	=head3 TIMING ISSUES	274	=head3 TIMING ISSUES
208		275
209	There are two ways to handle timers: based on real time (relative, "fire	276	There are two ways to handle timers: based on real time (relative, "fire
210	in 10 seconds") and based on wallclock time (absolute, "fire at 12	277	in 10 seconds") and based on wallclock time (absolute, "fire at 12
…		…
222	timers.	289	timers.
223		290
224	AnyEvent always prefers relative timers, if available, matching the	291	AnyEvent always prefers relative timers, if available, matching the
225	AnyEvent API.	292	AnyEvent API.
226		293
		294	AnyEvent has two additional methods that return the "current time":
		295
		296	=over 4
		297
		298	=item AnyEvent->time
		299
		300	This returns the "current wallclock time" as a fractional number of
		301	seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
		302	return, and the result is guaranteed to be compatible with those).
		303
		304	It progresses independently of any event loop processing, i.e. each call
		305	will check the system clock, which usually gets updated frequently.
		306
		307	=item AnyEvent->now
		308
		309	This also returns the "current wallclock time", but unlike C<time>, above,
		310	this value might change only once per event loop iteration, depending on
		311	the event loop (most return the same time as C<time>, above). This is the
		312	time that AnyEvent's timers get scheduled against.
		313
		314	I<In almost all cases (in all cases if you don't care), this is the
		315	function to call when you want to know the current time.>
		316
		317	This function is also often faster then C<< AnyEvent->time >>, and
		318	thus the preferred method if you want some timestamp (for example,
		319	L<AnyEvent::Handle> uses this to update it's activity timeouts).
		320
		321	The rest of this section is only of relevance if you try to be very exact
		322	with your timing, you can skip it without bad conscience.
		323
		324	For a practical example of when these times differ, consider L<Event::Lib>
		325	and L<EV> and the following set-up:
		326
		327	The event loop is running and has just invoked one of your callback at
		328	time=500 (assume no other callbacks delay processing). In your callback,
		329	you wait a second by executing C<sleep 1> (blocking the process for a
		330	second) and then (at time=501) you create a relative timer that fires
		331	after three seconds.
		332
		333	With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
		334	both return C<501>, because that is the current time, and the timer will
		335	be scheduled to fire at time=504 (C<501> + C<3>).
		336
		337	With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
		338	time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
		339	last event processing phase started. With L<EV>, your timer gets scheduled
		340	to run at time=503 (C<500> + C<3>).
		341
		342	In one sense, L<Event::Lib> is more exact, as it uses the current time
		343	regardless of any delays introduced by event processing. However, most
		344	callbacks do not expect large delays in processing, so this causes a
		345	higher drift (and a lot more system calls to get the current time).
		346
		347	In another sense, L<EV> is more exact, as your timer will be scheduled at
		348	the same time, regardless of how long event processing actually took.
		349
		350	In either case, if you care (and in most cases, you don't), then you
		351	can get whatever behaviour you want with any event loop, by taking the
		352	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
		353	account.
		354
		355	=item AnyEvent->now_update
		356
		357	Some event loops (such as L<EV> or L<AnyEvent::Impl::Perl>) cache
		358	the current time for each loop iteration (see the discussion of L<<
		359	AnyEvent->now >>, above).
		360
		361	When a callback runs for a long time (or when the process sleeps), then
		362	this "current" time will differ substantially from the real time, which
		363	might affect timers and time-outs.
		364
		365	When this is the case, you can call this method, which will update the
		366	event loop's idea of "current time".
		367
		368	A typical example would be a script in a web server (e.g. C<mod_perl>) -
		369	when mod_perl executes the script, then the event loop will have the wrong
		370	idea about the "current time" (being potentially far in the past, when the
		371	script ran the last time). In that case you should arrange a call to C<<
		372	AnyEvent->now_update >> each time the web server process wakes up again
		373	(e.g. at the start of your script, or in a handler).
		374
		375	Note that updating the time I<might> cause some events to be handled.
		376
		377	=back
		378
227	=head2 SIGNAL WATCHERS	379	=head2 SIGNAL WATCHERS
228		380
		381	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		382
229	You can watch for signals using a signal watcher, C<signal> is the signal	383	You can watch for signals using a signal watcher, C<signal> is the signal
230	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to	384	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
231	be invoked whenever a signal occurs.	385	callback to be invoked whenever a signal occurs.
232		386
		387	Although the callback might get passed parameters, their value and
		388	presence is undefined and you cannot rely on them. Portable AnyEvent
		389	callbacks cannot use arguments passed to signal watcher callbacks.
		390
233	Multiple signal occurances can be clumped together into one callback	391	Multiple signal occurrences can be clumped together into one callback
234	invocation, and callback invocation will be synchronous. synchronous means	392	invocation, and callback invocation will be synchronous. Synchronous means
235	that it might take a while until the signal gets handled by the process,	393	that it might take a while until the signal gets handled by the process,
236	but it is guarenteed not to interrupt any other callbacks.	394	but it is guaranteed not to interrupt any other callbacks.
237		395
238	The main advantage of using these watchers is that you can share a signal	396	The main advantage of using these watchers is that you can share a signal
239	between multiple watchers.	397	between multiple watchers, and AnyEvent will ensure that signals will not
		398	interrupt your program at bad times.
240		399
241	This watcher might use C<%SIG>, so programs overwriting those signals	400	This watcher might use C<%SIG> (depending on the event loop used),
242	directly will likely not work correctly.	401	so programs overwriting those signals directly will likely not work
		402	correctly.
243		403
244	Example: exit on SIGINT	404	Example: exit on SIGINT
245		405
246	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	406	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
247		407
		408	=head3 Restart Behaviour
		409
		410	While restart behaviour is up to the event loop implementation, most will
		411	not restart syscalls (that includes L<Async::Interrupt> and AnyEvent's
		412	pure perl implementation).
		413
		414	=head3 Safe/Unsafe Signals
		415
		416	Perl signals can be either "safe" (synchronous to opcode handling) or
		417	"unsafe" (asynchronous) - the former might get delayed indefinitely, the
		418	latter might corrupt your memory.
		419
		420	AnyEvent signal handlers are, in addition, synchronous to the event loop,
		421	i.e. they will not interrupt your running perl program but will only be
		422	called as part of the normal event handling (just like timer, I/O etc.
		423	callbacks, too).
		424
		425	=head3 Signal Races, Delays and Workarounds
		426
		427	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		428	callbacks to signals in a generic way, which is a pity, as you cannot
		429	do race-free signal handling in perl, requiring C libraries for
		430	this. AnyEvent will try to do it's best, which means in some cases,
		431	signals will be delayed. The maximum time a signal might be delayed is
		432	specified in C<$AnyEvent::MAX_SIGNAL_LATENCY> (default: 10 seconds). This
		433	variable can be changed only before the first signal watcher is created,
		434	and should be left alone otherwise. This variable determines how often
		435	AnyEvent polls for signals (in case a wake-up was missed). Higher values
		436	will cause fewer spurious wake-ups, which is better for power and CPU
		437	saving.
		438
		439	All these problems can be avoided by installing the optional
		440	L<Async::Interrupt> module, which works with most event loops. It will not
		441	work with inherently broken event loops such as L<Event> or L<Event::Lib>
		442	(and not with L<POE> currently, as POE does it's own workaround with
		443	one-second latency). For those, you just have to suffer the delays.
		444
248	=head2 CHILD PROCESS WATCHERS	445	=head2 CHILD PROCESS WATCHERS
249		446
		447	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		448
250	You can also watch on a child process exit and catch its exit status.	449	You can also watch on a child process exit and catch its exit status.
251		450
252	The child process is specified by the C<pid> argument (if set to C<0>, it	451	The child process is specified by the C<pid> argument (one some backends,
253	watches for any child process exit). The watcher will trigger as often	452	using C<0> watches for any child process exit, on others this will
254	as status change for the child are received. This works by installing a	453	croak). The watcher will be triggered only when the child process has
255	signal handler for C<SIGCHLD>. The callback will be called with the pid	454	finished and an exit status is available, not on any trace events
256	and exit status (as returned by waitpid).	455	(stopped/continued).
257		456
258	Example: wait for pid 1333	457	The callback will be called with the pid and exit status (as returned by
		458	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		459	callback arguments.
259		460
		461	This watcher type works by installing a signal handler for C<SIGCHLD>,
		462	and since it cannot be shared, nothing else should use SIGCHLD or reap
		463	random child processes (waiting for specific child processes, e.g. inside
		464	C<system>, is just fine).
		465
		466	There is a slight catch to child watchers, however: you usually start them
		467	I<after> the child process was created, and this means the process could
		468	have exited already (and no SIGCHLD will be sent anymore).
		469
		470	Not all event models handle this correctly (neither POE nor IO::Async do,
		471	see their AnyEvent::Impl manpages for details), but even for event models
		472	that I<do> handle this correctly, they usually need to be loaded before
		473	the process exits (i.e. before you fork in the first place). AnyEvent's
		474	pure perl event loop handles all cases correctly regardless of when you
		475	start the watcher.
		476
		477	This means you cannot create a child watcher as the very first
		478	thing in an AnyEvent program, you I<have> to create at least one
		479	watcher before you C<fork> the child (alternatively, you can call
		480	C<AnyEvent::detect>).
		481
		482	As most event loops do not support waiting for child events, they will be
		483	emulated by AnyEvent in most cases, in which the latency and race problems
		484	mentioned in the description of signal watchers apply.
		485
		486	Example: fork a process and wait for it
		487
		488	my $done = AnyEvent->condvar;
		489
		490	my $pid = fork or exit 5;
		491
260	my $w = AnyEvent->child (	492	my $w = AnyEvent->child (
261	pid => 1333,	493	pid => $pid,
262	cb => sub {	494	cb => sub {
263	my ($pid, $status) = @_;	495	my ($pid, $status) = @_;
264	warn "pid $pid exited with status $status";	496	warn "pid $pid exited with status $status";
		497	$done->send;
265	},	498	},
266	);	499	);
		500
		501	# do something else, then wait for process exit
		502	$done->recv;
		503
		504	=head2 IDLE WATCHERS
		505
		506	$w = AnyEvent->idle (cb => <callback>);
		507
		508	Repeatedly invoke the callback after the process becomes idle, until
		509	either the watcher is destroyed or new events have been detected.
		510
		511	Idle watchers are useful when there is a need to do something, but it
		512	is not so important (or wise) to do it instantly. The callback will be
		513	invoked only when there is "nothing better to do", which is usually
		514	defined as "all outstanding events have been handled and no new events
		515	have been detected". That means that idle watchers ideally get invoked
		516	when the event loop has just polled for new events but none have been
		517	detected. Instead of blocking to wait for more events, the idle watchers
		518	will be invoked.
		519
		520	Unfortunately, most event loops do not really support idle watchers (only
		521	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		522	will simply call the callback "from time to time".
		523
		524	Example: read lines from STDIN, but only process them when the
		525	program is otherwise idle:
		526
		527	my @lines; # read data
		528	my $idle_w;
		529	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		530	push @lines, scalar <STDIN>;
		531
		532	# start an idle watcher, if not already done
		533	$idle_w ||= AnyEvent->idle (cb => sub {
		534	# handle only one line, when there are lines left
		535	if (my $line = shift @lines) {
		536	print "handled when idle: $line";
		537	} else {
		538	# otherwise disable the idle watcher again
		539	undef $idle_w;
		540	}
		541	});
		542	});
267		543
268	=head2 CONDITION VARIABLES	544	=head2 CONDITION VARIABLES
269		545
		546	$cv = AnyEvent->condvar;
		547
		548	$cv->send (<list>);
		549	my @res = $cv->recv;
		550
		551	If you are familiar with some event loops you will know that all of them
		552	require you to run some blocking "loop", "run" or similar function that
		553	will actively watch for new events and call your callbacks.
		554
		555	AnyEvent is slightly different: it expects somebody else to run the event
		556	loop and will only block when necessary (usually when told by the user).
		557
		558	The instrument to do that is called a "condition variable", so called
		559	because they represent a condition that must become true.
		560
		561	Now is probably a good time to look at the examples further below.
		562
270	Condition variables can be created by calling the C<< AnyEvent->condvar >>	563	Condition variables can be created by calling the C<< AnyEvent->condvar
271	method without any arguments.	564	>> method, usually without arguments. The only argument pair allowed is
		565	C<cb>, which specifies a callback to be called when the condition variable
		566	becomes true, with the condition variable as the first argument (but not
		567	the results).
272		568
273	A condition variable waits for a condition - precisely that the C<<	569	After creation, the condition variable is "false" until it becomes "true"
274	->broadcast >> method has been called.	570	by calling the C<send> method (or calling the condition variable as if it
		571	were a callback, read about the caveats in the description for the C<<
		572	->send >> method).
275		573
276	They are very useful to signal that a condition has been fulfilled, for	574	Condition variables are similar to callbacks, except that you can
		575	optionally wait for them. They can also be called merge points - points
		576	in time where multiple outstanding events have been processed. And yet
		577	another way to call them is transactions - each condition variable can be
		578	used to represent a transaction, which finishes at some point and delivers
		579	a result. And yet some people know them as "futures" - a promise to
		580	compute/deliver something that you can wait for.
		581
		582	Condition variables are very useful to signal that something has finished,
277	example, if you write a module that does asynchronous http requests,	583	for example, if you write a module that does asynchronous http requests,
278	then a condition variable would be the ideal candidate to signal the	584	then a condition variable would be the ideal candidate to signal the
279	availability of results.	585	availability of results. The user can either act when the callback is
		586	called or can synchronously C<< ->recv >> for the results.
280		587
281	You can also use condition variables to block your main program until	588	You can also use them to simulate traditional event loops - for example,
282	an event occurs - for example, you could C<< ->wait >> in your main	589	you can block your main program until an event occurs - for example, you
283	program until the user clicks the Quit button in your app, which would C<<	590	could C<< ->recv >> in your main program until the user clicks the Quit
284	->broadcast >> the "quit" event.	591	button of your app, which would C<< ->send >> the "quit" event.
285		592
286	Note that condition variables recurse into the event loop - if you have	593	Note that condition variables recurse into the event loop - if you have
287	two pirces of code that call C<< ->wait >> in a round-robbin fashion, you	594	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
288	lose. Therefore, condition variables are good to export to your caller, but	595	lose. Therefore, condition variables are good to export to your caller, but
289	you should avoid making a blocking wait yourself, at least in callbacks,	596	you should avoid making a blocking wait yourself, at least in callbacks,
290	as this asks for trouble.	597	as this asks for trouble.
291		598
292	This object has two methods:	599	Condition variables are represented by hash refs in perl, and the keys
		600	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
		601	easy (it is often useful to build your own transaction class on top of
		602	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
		603	it's C<new> method in your own C<new> method.
293		604
294	=over 4	605	There are two "sides" to a condition variable - the "producer side" which
		606	eventually calls C<< -> send >>, and the "consumer side", which waits
		607	for the send to occur.
295		608
296	=item $cv->wait	609	Example: wait for a timer.
297
298	Wait (blocking if necessary) until the C<< ->broadcast >> method has been
299	called on c<$cv>, while servicing other watchers normally.
300
301	You can only wait once on a condition - additional calls will return
302	immediately.
303
304	Not all event models support a blocking wait - some die in that case
305	(programs might want to do that to stay interactive), so I<if you are
306	using this from a module, never require a blocking wait>, but let the
307	caller decide whether the call will block or not (for example, by coupling
308	condition variables with some kind of request results and supporting
309	callbacks so the caller knows that getting the result will not block,
310	while still suppporting blocking waits if the caller so desires).
311
312	Another reason I<never> to C<< ->wait >> in a module is that you cannot
313	sensibly have two C<< ->wait >>'s in parallel, as that would require
314	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
315	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and
316	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
317	from different coroutines, however).
318
319	=item $cv->broadcast
320
321	Flag the condition as ready - a running C<< ->wait >> and all further
322	calls to C<wait> will (eventually) return after this method has been
323	called. If nobody is waiting the broadcast will be remembered..
324
325	=back
326
327	Example:
328		610
329	# wait till the result is ready	611	# wait till the result is ready
330	my $result_ready = AnyEvent->condvar;	612	my $result_ready = AnyEvent->condvar;
331		613
332	# do something such as adding a timer	614	# do something such as adding a timer
333	# or socket watcher the calls $result_ready->broadcast	615	# or socket watcher the calls $result_ready->send
334	# when the "result" is ready.	616	# when the "result" is ready.
335	# in this case, we simply use a timer:	617	# in this case, we simply use a timer:
336	my $w = AnyEvent->timer (	618	my $w = AnyEvent->timer (
337	after => 1,	619	after => 1,
338	cb => sub { $result_ready->broadcast },	620	cb => sub { $result_ready->send },
339	);	621	);
340		622
341	# this "blocks" (while handling events) till the watcher	623	# this "blocks" (while handling events) till the callback
342	# calls broadcast	624	# calls ->send
343	$result_ready->wait;	625	$result_ready->recv;
		626
		627	Example: wait for a timer, but take advantage of the fact that condition
		628	variables are also callable directly.
		629
		630	my $done = AnyEvent->condvar;
		631	my $delay = AnyEvent->timer (after => 5, cb => $done);
		632	$done->recv;
		633
		634	Example: Imagine an API that returns a condvar and doesn't support
		635	callbacks. This is how you make a synchronous call, for example from
		636	the main program:
		637
		638	use AnyEvent::CouchDB;
		639
		640	...
		641
		642	my @info = $couchdb->info->recv;
		643
		644	And this is how you would just set a callback to be called whenever the
		645	results are available:
		646
		647	$couchdb->info->cb (sub {
		648	my @info = $_[0]->recv;
		649	});
		650
		651	=head3 METHODS FOR PRODUCERS
		652
		653	These methods should only be used by the producing side, i.e. the
		654	code/module that eventually sends the signal. Note that it is also
		655	the producer side which creates the condvar in most cases, but it isn't
		656	uncommon for the consumer to create it as well.
		657
		658	=over 4
		659
		660	=item $cv->send (...)
		661
		662	Flag the condition as ready - a running C<< ->recv >> and all further
		663	calls to C<recv> will (eventually) return after this method has been
		664	called. If nobody is waiting the send will be remembered.
		665
		666	If a callback has been set on the condition variable, it is called
		667	immediately from within send.
		668
		669	Any arguments passed to the C<send> call will be returned by all
		670	future C<< ->recv >> calls.
		671
		672	Condition variables are overloaded so one can call them directly (as if
		673	they were a code reference). Calling them directly is the same as calling
		674	C<send>.
		675
		676	=item $cv->croak ($error)
		677
		678	Similar to send, but causes all call's to C<< ->recv >> to invoke
		679	C<Carp::croak> with the given error message/object/scalar.
		680
		681	This can be used to signal any errors to the condition variable
		682	user/consumer. Doing it this way instead of calling C<croak> directly
		683	delays the error detetcion, but has the overwhelmign advantage that it
		684	diagnoses the error at the place where the result is expected, and not
		685	deep in some event clalback without connection to the actual code causing
		686	the problem.
		687
		688	=item $cv->begin ([group callback])
		689
		690	=item $cv->end
		691
		692	These two methods can be used to combine many transactions/events into
		693	one. For example, a function that pings many hosts in parallel might want
		694	to use a condition variable for the whole process.
		695
		696	Every call to C<< ->begin >> will increment a counter, and every call to
		697	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
		698	>>, the (last) callback passed to C<begin> will be executed, passing the
		699	condvar as first argument. That callback is I<supposed> to call C<< ->send
		700	>>, but that is not required. If no group callback was set, C<send> will
		701	be called without any arguments.
		702
		703	You can think of C<< $cv->send >> giving you an OR condition (one call
		704	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		705	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		706
		707	Let's start with a simple example: you have two I/O watchers (for example,
		708	STDOUT and STDERR for a program), and you want to wait for both streams to
		709	close before activating a condvar:
		710
		711	my $cv = AnyEvent->condvar;
		712
		713	$cv->begin; # first watcher
		714	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		715	defined sysread $fh1, my $buf, 4096
		716	or $cv->end;
		717	});
		718
		719	$cv->begin; # second watcher
		720	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		721	defined sysread $fh2, my $buf, 4096
		722	or $cv->end;
		723	});
		724
		725	$cv->recv;
		726
		727	This works because for every event source (EOF on file handle), there is
		728	one call to C<begin>, so the condvar waits for all calls to C<end> before
		729	sending.
		730
		731	The ping example mentioned above is slightly more complicated, as the
		732	there are results to be passwd back, and the number of tasks that are
		733	begung can potentially be zero:
		734
		735	my $cv = AnyEvent->condvar;
		736
		737	my %result;
		738	$cv->begin (sub { shift->send (\%result) });
		739
		740	for my $host (@list_of_hosts) {
		741	$cv->begin;
		742	ping_host_then_call_callback $host, sub {
		743	$result{$host} = ...;
		744	$cv->end;
		745	};
		746	}
		747
		748	$cv->end;
		749
		750	This code fragment supposedly pings a number of hosts and calls
		751	C<send> after results for all then have have been gathered - in any
		752	order. To achieve this, the code issues a call to C<begin> when it starts
		753	each ping request and calls C<end> when it has received some result for
		754	it. Since C<begin> and C<end> only maintain a counter, the order in which
		755	results arrive is not relevant.
		756
		757	There is an additional bracketing call to C<begin> and C<end> outside the
		758	loop, which serves two important purposes: first, it sets the callback
		759	to be called once the counter reaches C<0>, and second, it ensures that
		760	C<send> is called even when C<no> hosts are being pinged (the loop
		761	doesn't execute once).
		762
		763	This is the general pattern when you "fan out" into multiple (but
		764	potentially none) subrequests: use an outer C<begin>/C<end> pair to set
		765	the callback and ensure C<end> is called at least once, and then, for each
		766	subrequest you start, call C<begin> and for each subrequest you finish,
		767	call C<end>.
		768
		769	=back
		770
		771	=head3 METHODS FOR CONSUMERS
		772
		773	These methods should only be used by the consuming side, i.e. the
		774	code awaits the condition.
		775
		776	=over 4
		777
		778	=item $cv->recv
		779
		780	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
		781	>> methods have been called on c<$cv>, while servicing other watchers
		782	normally.
		783
		784	You can only wait once on a condition - additional calls are valid but
		785	will return immediately.
		786
		787	If an error condition has been set by calling C<< ->croak >>, then this
		788	function will call C<croak>.
		789
		790	In list context, all parameters passed to C<send> will be returned,
		791	in scalar context only the first one will be returned.
		792
		793	Note that doing a blocking wait in a callback is not supported by any
		794	event loop, that is, recursive invocation of a blocking C<< ->recv
		795	>> is not allowed, and the C<recv> call will C<croak> if such a
		796	condition is detected. This condition can be slightly loosened by using
		797	L<Coro::AnyEvent>, which allows you to do a blocking C<< ->recv >> from
		798	any thread that doesn't run the event loop itself.
		799
		800	Not all event models support a blocking wait - some die in that case
		801	(programs might want to do that to stay interactive), so I<if you are
		802	using this from a module, never require a blocking wait>. Instead, let the
		803	caller decide whether the call will block or not (for example, by coupling
		804	condition variables with some kind of request results and supporting
		805	callbacks so the caller knows that getting the result will not block,
		806	while still supporting blocking waits if the caller so desires).
		807
		808	You can ensure that C<< -recv >> never blocks by setting a callback and
		809	only calling C<< ->recv >> from within that callback (or at a later
		810	time). This will work even when the event loop does not support blocking
		811	waits otherwise.
		812
		813	=item $bool = $cv->ready
		814
		815	Returns true when the condition is "true", i.e. whether C<send> or
		816	C<croak> have been called.
		817
		818	=item $cb = $cv->cb ($cb->($cv))
		819
		820	This is a mutator function that returns the callback set and optionally
		821	replaces it before doing so.
		822
		823	The callback will be called when the condition becomes (or already was)
		824	"true", i.e. when C<send> or C<croak> are called (or were called), with
		825	the only argument being the condition variable itself. Calling C<recv>
		826	inside the callback or at any later time is guaranteed not to block.
		827
		828	=back
		829
		830	=head1 SUPPORTED EVENT LOOPS/BACKENDS
		831
		832	The available backend classes are (every class has its own manpage):
		833
		834	=over 4
		835
		836	=item Backends that are autoprobed when no other event loop can be found.
		837
		838	EV is the preferred backend when no other event loop seems to be in
		839	use. If EV is not installed, then AnyEvent will fall back to its own
		840	pure-perl implementation, which is available everywhere as it comes with
		841	AnyEvent itself.
		842
		843	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		844	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
		845
		846	=item Backends that are transparently being picked up when they are used.
		847
		848	These will be used when they are currently loaded when the first watcher
		849	is created, in which case it is assumed that the application is using
		850	them. This means that AnyEvent will automatically pick the right backend
		851	when the main program loads an event module before anything starts to
		852	create watchers. Nothing special needs to be done by the main program.
		853
		854	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		855	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		856	AnyEvent::Impl::Tk based on Tk, very broken.
		857	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		858	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		859	AnyEvent::Impl::Irssi used when running within irssi.
		860
		861	=item Backends with special needs.
		862
		863	Qt requires the Qt::Application to be instantiated first, but will
		864	otherwise be picked up automatically. As long as the main program
		865	instantiates the application before any AnyEvent watchers are created,
		866	everything should just work.
		867
		868	AnyEvent::Impl::Qt based on Qt.
		869
		870	Support for IO::Async can only be partial, as it is too broken and
		871	architecturally limited to even support the AnyEvent API. It also
		872	is the only event loop that needs the loop to be set explicitly, so
		873	it can only be used by a main program knowing about AnyEvent. See
		874	L<AnyEvent::Impl::Async> for the gory details.
		875
		876	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
		877
		878	=item Event loops that are indirectly supported via other backends.
		879
		880	Some event loops can be supported via other modules:
		881
		882	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		883
		884	B<WxWidgets> has no support for watching file handles. However, you can
		885	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		886	polls 20 times per second, which was considered to be too horrible to even
		887	consider for AnyEvent.
		888
		889	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		890	backend, so it can be supported through POE.
		891
		892	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		893	load L<POE> when detecting them, in the hope that POE will pick them up,
		894	in which case everything will be automatic.
		895
		896	=back
344		897
345	=head1 GLOBAL VARIABLES AND FUNCTIONS	898	=head1 GLOBAL VARIABLES AND FUNCTIONS
346		899
		900	These are not normally required to use AnyEvent, but can be useful to
		901	write AnyEvent extension modules.
		902
347	=over 4	903	=over 4
348		904
349	=item $AnyEvent::MODEL	905	=item $AnyEvent::MODEL
350		906
351	Contains C<undef> until the first watcher is being created. Then it	907	Contains C<undef> until the first watcher is being created, before the
		908	backend has been autodetected.
		909
352	contains the event model that is being used, which is the name of the	910	Afterwards it contains the event model that is being used, which is the
353	Perl class implementing the model. This class is usually one of the	911	name of the Perl class implementing the model. This class is usually one
354	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	912	of the C<AnyEvent::Impl:xxx> modules, but can be any other class in the
355	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	913	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
356		914	will be C<urxvt::anyevent>).
357	The known classes so far are:
358
359	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
360	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
361	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
362	AnyEvent::Impl::Event based on Event, second best choice.
363	AnyEvent::Impl::Glib based on Glib, third-best choice.
364	AnyEvent::Impl::Tk based on Tk, very bad choice.
365	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
366	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
367	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
368	AnyEvent::Impl::POE based on POE, not generic enough for full support.
369
370	There is no support for WxWidgets, as WxWidgets has no support for
371	watching file handles. However, you can use WxWidgets through the
372	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
373	second, which was considered to be too horrible to even consider for
374	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
375	it's adaptor.
376
377	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
378	autodetecting them.
379		915
380	=item AnyEvent::detect	916	=item AnyEvent::detect
381		917
382	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	918	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
383	if necessary. You should only call this function right before you would	919	if necessary. You should only call this function right before you would
384	have created an AnyEvent watcher anyway, that is, as late as possible at	920	have created an AnyEvent watcher anyway, that is, as late as possible at
385	runtime.	921	runtime, and not e.g. while initialising of your module.
		922
		923	If you need to do some initialisation before AnyEvent watchers are
		924	created, use C<post_detect>.
		925
		926	=item $guard = AnyEvent::post_detect { BLOCK }
		927
		928	Arranges for the code block to be executed as soon as the event model is
		929	autodetected (or immediately if this has already happened).
		930
		931	The block will be executed I<after> the actual backend has been detected
		932	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		933	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		934	other initialisations - see the sources of L<AnyEvent::Strict> or
		935	L<AnyEvent::AIO> to see how this is used.
		936
		937	The most common usage is to create some global watchers, without forcing
		938	event module detection too early, for example, L<AnyEvent::AIO> creates
		939	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		940	avoid autodetecting the event module at load time.
		941
		942	If called in scalar or list context, then it creates and returns an object
		943	that automatically removes the callback again when it is destroyed (or
		944	C<undef> when the hook was immediately executed). See L<AnyEvent::AIO> for
		945	a case where this is useful.
		946
		947	Example: Create a watcher for the IO::AIO module and store it in
		948	C<$WATCHER>. Only do so after the event loop is initialised, though.
		949
		950	our WATCHER;
		951
		952	my $guard = AnyEvent::post_detect {
		953	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		954	};
		955
		956	# the ||= is important in case post_detect immediately runs the block,
		957	# as to not clobber the newly-created watcher. assigning both watcher and
		958	# post_detect guard to the same variable has the advantage of users being
		959	# able to just C<undef $WATCHER> if the watcher causes them grief.
		960
		961	$WATCHER ||= $guard;
		962
		963	=item @AnyEvent::post_detect
		964
		965	If there are any code references in this array (you can C<push> to it
		966	before or after loading AnyEvent), then they will called directly after
		967	the event loop has been chosen.
		968
		969	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		970	if it is defined then the event loop has already been detected, and the
		971	array will be ignored.
		972
		973	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		974	it, as it takes care of these details.
		975
		976	This variable is mainly useful for modules that can do something useful
		977	when AnyEvent is used and thus want to know when it is initialised, but do
		978	not need to even load it by default. This array provides the means to hook
		979	into AnyEvent passively, without loading it.
		980
		981	Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used
		982	together, you could put this into Coro (this is the actual code used by
		983	Coro to accomplish this):
		984
		985	if (defined $AnyEvent::MODEL) {
		986	# AnyEvent already initialised, so load Coro::AnyEvent
		987	require Coro::AnyEvent;
		988	} else {
		989	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent
		990	# as soon as it is
		991	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };
		992	}
386		993
387	=back	994	=back
388		995
389	=head1 WHAT TO DO IN A MODULE	996	=head1 WHAT TO DO IN A MODULE
390		997
…		…
394	Be careful when you create watchers in the module body - AnyEvent will	1001	Be careful when you create watchers in the module body - AnyEvent will
395	decide which event module to use as soon as the first method is called, so	1002	decide which event module to use as soon as the first method is called, so
396	by calling AnyEvent in your module body you force the user of your module	1003	by calling AnyEvent in your module body you force the user of your module
397	to load the event module first.	1004	to load the event module first.
398		1005
399	Never call C<< ->wait >> on a condition variable unless you I<know> that	1006	Never call C<< ->recv >> on a condition variable unless you I<know> that
400	the C<< ->broadcast >> method has been called on it already. This is	1007	the C<< ->send >> method has been called on it already. This is
401	because it will stall the whole program, and the whole point of using	1008	because it will stall the whole program, and the whole point of using
402	events is to stay interactive.	1009	events is to stay interactive.
403		1010
404	It is fine, however, to call C<< ->wait >> when the user of your module	1011	It is fine, however, to call C<< ->recv >> when the user of your module
405	requests it (i.e. if you create a http request object ad have a method	1012	requests it (i.e. if you create a http request object ad have a method
406	called C<results> that returns the results, it should call C<< ->wait >>	1013	called C<results> that returns the results, it should call C<< ->recv >>
407	freely, as the user of your module knows what she is doing. always).	1014	freely, as the user of your module knows what she is doing. always).
408		1015
409	=head1 WHAT TO DO IN THE MAIN PROGRAM	1016	=head1 WHAT TO DO IN THE MAIN PROGRAM
410		1017
411	There will always be a single main program - the only place that should	1018	There will always be a single main program - the only place that should
…		…
413		1020
414	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	1021	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
415	do anything special (it does not need to be event-based) and let AnyEvent	1022	do anything special (it does not need to be event-based) and let AnyEvent
416	decide which implementation to chose if some module relies on it.	1023	decide which implementation to chose if some module relies on it.
417		1024
418	If the main program relies on a specific event model. For example, in	1025	If the main program relies on a specific event model - for example, in
419	Gtk2 programs you have to rely on the Glib module. You should load the	1026	Gtk2 programs you have to rely on the Glib module - you should load the
420	event module before loading AnyEvent or any module that uses it: generally	1027	event module before loading AnyEvent or any module that uses it: generally
421	speaking, you should load it as early as possible. The reason is that	1028	speaking, you should load it as early as possible. The reason is that
422	modules might create watchers when they are loaded, and AnyEvent will	1029	modules might create watchers when they are loaded, and AnyEvent will
423	decide on the event model to use as soon as it creates watchers, and it	1030	decide on the event model to use as soon as it creates watchers, and it
424	might chose the wrong one unless you load the correct one yourself.	1031	might chose the wrong one unless you load the correct one yourself.
425		1032
426	You can chose to use a rather inefficient pure-perl implementation by	1033	You can chose to use a pure-perl implementation by loading the
427	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	1034	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
428	behaviour everywhere, but letting AnyEvent chose is generally better.	1035	everywhere, but letting AnyEvent chose the model is generally better.
		1036
		1037	=head2 MAINLOOP EMULATION
		1038
		1039	Sometimes (often for short test scripts, or even standalone programs who
		1040	only want to use AnyEvent), you do not want to run a specific event loop.
		1041
		1042	In that case, you can use a condition variable like this:
		1043
		1044	AnyEvent->condvar->recv;
		1045
		1046	This has the effect of entering the event loop and looping forever.
		1047
		1048	Note that usually your program has some exit condition, in which case
		1049	it is better to use the "traditional" approach of storing a condition
		1050	variable somewhere, waiting for it, and sending it when the program should
		1051	exit cleanly.
		1052
		1053
		1054	=head1 OTHER MODULES
		1055
		1056	The following is a non-exhaustive list of additional modules that use
		1057	AnyEvent as a client and can therefore be mixed easily with other AnyEvent
		1058	modules and other event loops in the same program. Some of the modules
		1059	come with AnyEvent, most are available via CPAN.
		1060
		1061	=over 4
		1062
		1063	=item L<AnyEvent::Util>
		1064
		1065	Contains various utility functions that replace often-used but blocking
		1066	functions such as C<inet_aton> by event-/callback-based versions.
		1067
		1068	=item L<AnyEvent::Socket>
		1069
		1070	Provides various utility functions for (internet protocol) sockets,
		1071	addresses and name resolution. Also functions to create non-blocking tcp
		1072	connections or tcp servers, with IPv6 and SRV record support and more.
		1073
		1074	=item L<AnyEvent::Handle>
		1075
		1076	Provide read and write buffers, manages watchers for reads and writes,
		1077	supports raw and formatted I/O, I/O queued and fully transparent and
		1078	non-blocking SSL/TLS (via L<AnyEvent::TLS>.
		1079
		1080	=item L<AnyEvent::DNS>
		1081
		1082	Provides rich asynchronous DNS resolver capabilities.
		1083
		1084	=item L<AnyEvent::HTTP>
		1085
		1086	A simple-to-use HTTP library that is capable of making a lot of concurrent
		1087	HTTP requests.
		1088
		1089	=item L<AnyEvent::HTTPD>
		1090
		1091	Provides a simple web application server framework.
		1092
		1093	=item L<AnyEvent::FastPing>
		1094
		1095	The fastest ping in the west.
		1096
		1097	=item L<AnyEvent::DBI>
		1098
		1099	Executes L<DBI> requests asynchronously in a proxy process.
		1100
		1101	=item L<AnyEvent::AIO>
		1102
		1103	Truly asynchronous I/O, should be in the toolbox of every event
		1104	programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
		1105	together.
		1106
		1107	=item L<AnyEvent::BDB>
		1108
		1109	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
		1110	L<BDB> and AnyEvent together.
		1111
		1112	=item L<AnyEvent::GPSD>
		1113
		1114	A non-blocking interface to gpsd, a daemon delivering GPS information.
		1115
		1116	=item L<AnyEvent::IRC>
		1117
		1118	AnyEvent based IRC client module family (replacing the older Net::IRC3).
		1119
		1120	=item L<AnyEvent::XMPP>
		1121
		1122	AnyEvent based XMPP (Jabber protocol) module family (replacing the older
		1123	Net::XMPP2>.
		1124
		1125	=item L<AnyEvent::IGS>
		1126
		1127	A non-blocking interface to the Internet Go Server protocol (used by
		1128	L<App::IGS>).
		1129
		1130	=item L<Net::FCP>
		1131
		1132	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
		1133	of AnyEvent.
		1134
		1135	=item L<Event::ExecFlow>
		1136
		1137	High level API for event-based execution flow control.
		1138
		1139	=item L<Coro>
		1140
		1141	Has special support for AnyEvent via L<Coro::AnyEvent>.
		1142
		1143	=back
429		1144
430	=cut	1145	=cut
431		1146
432	package AnyEvent;	1147	package AnyEvent;
433		1148
434	no warnings;	1149	# basically a tuned-down version of common::sense
435	use strict;	1150	sub common_sense {
		1151	# from common:.sense 1.0
		1152	${^WARNING_BITS} = "\xfc\x3f\x33\x00\x0f\xf3\xcf\xc0\xf3\xfc\x33\x00";
		1153	# use strict vars subs - NO UTF-8, as Util.pm doesn't like this atm. (uts46data.pl)
		1154	$^H |= 0x00000600;
		1155	}
436		1156
		1157	BEGIN { AnyEvent::common_sense }
		1158
437	use Carp;	1159	use Carp ();
438		1160
439	our $VERSION = '3.3';	1161	our $VERSION = '5.24';
440	our $MODEL;	1162	our $MODEL;
441		1163
442	our $AUTOLOAD;	1164	our $AUTOLOAD;
443	our @ISA;	1165	our @ISA;
444		1166
445	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
446
447	our @REGISTRY;	1167	our @REGISTRY;
448		1168
		1169	our $VERBOSE;
		1170
		1171	BEGIN {
		1172	eval "sub CYGWIN(){" . (($^O =~ /cygwin/i) *1) . "}";
		1173	eval "sub WIN32 (){" . (($^O =~ /mswin32/i)*1) . "}";
		1174	eval "sub TAINT (){" . (${^TAINT} *1) . "}";
		1175
		1176	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1177	if ${^TAINT};
		1178
		1179	$VERBOSE = $ENV{PERL_ANYEVENT_VERBOSE}*1;
		1180
		1181	}
		1182
		1183	our $MAX_SIGNAL_LATENCY = 10;
		1184
		1185	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		1186
		1187	{
		1188	my $idx;
		1189	$PROTOCOL{$_} = ++$idx
		1190	for reverse split /\s*,\s*/,
		1191	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		1192	}
		1193
449	my @models = (	1194	my @models = (
450	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
451	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
452	[EV:: => AnyEvent::Impl::EV::],	1195	[EV:: => AnyEvent::Impl::EV:: , 1],
		1196	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl:: , 1],
		1197	# everything below here will not (normally) be autoprobed
		1198	# as the pureperl backend should work everywhere
		1199	# and is usually faster
453	[Event:: => AnyEvent::Impl::Event::],	1200	[Event:: => AnyEvent::Impl::Event::, 1],
454	[Glib:: => AnyEvent::Impl::Glib::],	1201	[Glib:: => AnyEvent::Impl::Glib:: , 1], # becomes extremely slow with many watchers
		1202	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		1203	[Irssi:: => AnyEvent::Impl::Irssi::], # Irssi has a bogus "Event" package
455	[Tk:: => AnyEvent::Impl::Tk::],	1204	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		1205	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		1206	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
456	[Wx:: => AnyEvent::Impl::POE::],	1207	[Wx:: => AnyEvent::Impl::POE::],
457	[Prima:: => AnyEvent::Impl::POE::],	1208	[Prima:: => AnyEvent::Impl::POE::],
458	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1209	# IO::Async is just too broken - we would need workarounds for its
459	# everything below here will not be autoprobed as the pureperl backend should work everywhere	1210	# byzantine signal and broken child handling, among others.
460	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy	1211	# IO::Async is rather hard to detect, as it doesn't have any
		1212	# obvious default class.
461	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program	1213	[IO::Async:: => AnyEvent::Impl::IOAsync::], # requires special main program
462	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza	1214	[IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1215	[IO::Async::Notifier:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1216	[AnyEvent::Impl::IOAsync:: => AnyEvent::Impl::IOAsync::], # requires special main program
463	);	1217	);
464		1218
465	our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);	1219	our %method = map +($_ => 1),
		1220	qw(io timer time now now_update signal child idle condvar one_event DESTROY);
		1221
		1222	our @post_detect;
		1223
		1224	sub post_detect(&) {
		1225	my ($cb) = @_;
		1226
		1227	if ($MODEL) {
		1228	$cb->();
		1229
		1230	undef
		1231	} else {
		1232	push @post_detect, $cb;
		1233
		1234	defined wantarray
		1235	? bless \$cb, "AnyEvent::Util::postdetect"
		1236	: ()
		1237	}
		1238	}
		1239
		1240	sub AnyEvent::Util::postdetect::DESTROY {
		1241	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		1242	}
466		1243
467	sub detect() {	1244	sub detect() {
468	unless ($MODEL) {	1245	unless ($MODEL) {
469	no strict 'refs';	1246	local $SIG{__DIE__};
470		1247
471	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	1248	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
472	my $model = "AnyEvent::Impl::$1";	1249	my $model = "AnyEvent::Impl::$1";
473	if (eval "require $model") {	1250	if (eval "require $model") {
474	$MODEL = $model;	1251	$MODEL = $model;
475	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	1252	warn "AnyEvent: loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.\n" if $VERBOSE >= 2;
476	} else {	1253	} else {
477	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;	1254	warn "AnyEvent: unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@" if $VERBOSE;
478	}	1255	}
479	}	1256	}
480		1257
481	# check for already loaded models	1258	# check for already loaded models
482	unless ($MODEL) {	1259	unless ($MODEL) {
483	for (@REGISTRY, @models) {	1260	for (@REGISTRY, @models) {
484	my ($package, $model) = @$_;	1261	my ($package, $model) = @$_;
485	if (${"$package\::VERSION"} > 0) {	1262	if (${"$package\::VERSION"} > 0) {
486	if (eval "require $model") {	1263	if (eval "require $model") {
487	$MODEL = $model;	1264	$MODEL = $model;
488	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;	1265	warn "AnyEvent: autodetected model '$model', using it.\n" if $VERBOSE >= 2;
489	last;	1266	last;
490	}	1267	}
491	}	1268	}
492	}	1269	}
493		1270
494	unless ($MODEL) {	1271	unless ($MODEL) {
495	# try to load a model	1272	# try to autoload a model
496
497	for (@REGISTRY, @models) {	1273	for (@REGISTRY, @models) {
498	my ($package, $model) = @$_;	1274	my ($package, $model, $autoload) = @$_;
		1275	if (
		1276	$autoload
499	if (eval "require $package"	1277	and eval "require $package"
500	and ${"$package\::VERSION"} > 0	1278	and ${"$package\::VERSION"} > 0
501	and eval "require $model") {	1279	and eval "require $model"
		1280	) {
502	$MODEL = $model;	1281	$MODEL = $model;
503	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;	1282	warn "AnyEvent: autoloaded model '$model', using it.\n" if $VERBOSE >= 2;
504	last;	1283	last;
505	}	1284	}
506	}	1285	}
507		1286
508	$MODEL	1287	$MODEL
509	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV (or Coro+EV), Event (or Coro+Event) or Glib.";	1288	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.\n";
510	}	1289	}
511	}	1290	}
512		1291
		1292	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		1293
513	unshift @ISA, $MODEL;	1294	unshift @ISA, $MODEL;
514	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	1295
		1296	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
		1297
		1298	(shift @post_detect)->() while @post_detect;
515	}	1299	}
516		1300
517	$MODEL	1301	$MODEL
518	}	1302	}
519		1303
520	sub AUTOLOAD {	1304	sub AUTOLOAD {
521	(my $func = $AUTOLOAD) =~ s/.*://;	1305	(my $func = $AUTOLOAD) =~ s/.*://;
522		1306
523	$method{$func}	1307	$method{$func}
524	or croak "$func: not a valid method for AnyEvent objects";	1308	or Carp::croak "$func: not a valid method for AnyEvent objects";
525		1309
526	detect unless $MODEL;	1310	detect unless $MODEL;
527		1311
528	my $class = shift;	1312	my $class = shift;
529	$class->$func (@_);	1313	$class->$func (@_);
530	}	1314	}
531		1315
		1316	# utility function to dup a filehandle. this is used by many backends
		1317	# to support binding more than one watcher per filehandle (they usually
		1318	# allow only one watcher per fd, so we dup it to get a different one).
		1319	sub _dupfh($$;$$) {
		1320	my ($poll, $fh, $r, $w) = @_;
		1321
		1322	# cygwin requires the fh mode to be matching, unix doesn't
		1323	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1324
		1325	open my $fh2, $mode, $fh
		1326	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1327
		1328	# we assume CLOEXEC is already set by perl in all important cases
		1329
		1330	($fh2, $rw)
		1331	}
		1332
		1333	=head1 SIMPLIFIED AE API
		1334
		1335	Starting with version 5.0, AnyEvent officially supports a second, much
		1336	simpler, API that is designed to reduce the calling, typing and memory
		1337	overhead.
		1338
		1339	See the L<AE> manpage for details.
		1340
		1341	=cut
		1342
		1343	package AE;
		1344
		1345	our $VERSION = $AnyEvent::VERSION;
		1346
		1347	sub io($$$) {
		1348	AnyEvent->io (fh => $_[0], poll => $_[1] ? "w" : "r", cb => $_[2])
		1349	}
		1350
		1351	sub timer($$$) {
		1352	AnyEvent->timer (after => $_[0], interval => $_[1], cb => $_[2])
		1353	}
		1354
		1355	sub signal($$) {
		1356	AnyEvent->signal (signal => $_[0], cb => $_[1])
		1357	}
		1358
		1359	sub child($$) {
		1360	AnyEvent->child (pid => $_[0], cb => $_[1])
		1361	}
		1362
		1363	sub idle($) {
		1364	AnyEvent->idle (cb => $_[0])
		1365	}
		1366
		1367	sub cv(;&) {
		1368	AnyEvent->condvar (@_ ? (cb => $_[0]) : ())
		1369	}
		1370
		1371	sub now() {
		1372	AnyEvent->now
		1373	}
		1374
		1375	sub now_update() {
		1376	AnyEvent->now_update
		1377	}
		1378
		1379	sub time() {
		1380	AnyEvent->time
		1381	}
		1382
532	package AnyEvent::Base;	1383	package AnyEvent::Base;
533		1384
		1385	# default implementations for many methods
		1386
		1387	sub _time() {
		1388	# probe for availability of Time::HiRes
		1389	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1390	warn "AnyEvent: using Time::HiRes for sub-second timing accuracy.\n" if $VERBOSE >= 8;
		1391	*_time = \&Time::HiRes::time;
		1392	# if (eval "use POSIX (); (POSIX::times())...
		1393	} else {
		1394	warn "AnyEvent: using built-in time(), WARNING, no sub-second resolution!\n" if $VERBOSE;
		1395	*_time = sub { time }; # epic fail
		1396	}
		1397
		1398	&_time
		1399	}
		1400
		1401	sub time { _time }
		1402	sub now { _time }
		1403	sub now_update { }
		1404
534	# default implementation for ->condvar, ->wait, ->broadcast	1405	# default implementation for ->condvar
535		1406
536	sub condvar {	1407	sub condvar {
537	bless \my $flag, "AnyEvent::Base::CondVar"	1408	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
538	}
539
540	sub AnyEvent::Base::CondVar::broadcast {
541	${$_[0]}++;
542	}
543
544	sub AnyEvent::Base::CondVar::wait {
545	AnyEvent->one_event while !${$_[0]};
546	}	1409	}
547		1410
548	# default implementation for ->signal	1411	# default implementation for ->signal
549		1412
550	our %SIG_CB;	1413	our $HAVE_ASYNC_INTERRUPT;
		1414
		1415	sub _have_async_interrupt() {
		1416	$HAVE_ASYNC_INTERRUPT = 1*(!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT}
		1417	&& eval "use Async::Interrupt 1.02 (); 1")
		1418	unless defined $HAVE_ASYNC_INTERRUPT;
		1419
		1420	$HAVE_ASYNC_INTERRUPT
		1421	}
		1422
		1423	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1424	our (%SIG_ASY, %SIG_ASY_W);
		1425	our ($SIG_COUNT, $SIG_TW);
		1426
		1427	sub _signal_exec {
		1428	$HAVE_ASYNC_INTERRUPT
		1429	? $SIGPIPE_R->drain
		1430	: sysread $SIGPIPE_R, (my $dummy), 9;
		1431
		1432	while (%SIG_EV) {
		1433	for (keys %SIG_EV) {
		1434	delete $SIG_EV{$_};
		1435	$_->() for values %{ $SIG_CB{$_} || {} };
		1436	}
		1437	}
		1438	}
		1439
		1440	# install a dummy wakeup watcher to reduce signal catching latency
		1441	sub _sig_add() {
		1442	unless ($SIG_COUNT++) {
		1443	# try to align timer on a full-second boundary, if possible
		1444	my $NOW = AE::now;
		1445
		1446	$SIG_TW = AE::timer
		1447	$MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1448	$MAX_SIGNAL_LATENCY,
		1449	sub { } # just for the PERL_ASYNC_CHECK
		1450	;
		1451	}
		1452	}
		1453
		1454	sub _sig_del {
		1455	undef $SIG_TW
		1456	unless --$SIG_COUNT;
		1457	}
		1458
		1459	our $_sig_name_init; $_sig_name_init = sub {
		1460	eval q{ # poor man's autoloading
		1461	undef $_sig_name_init;
		1462
		1463	if (_have_async_interrupt) {
		1464	*sig2num = \&Async::Interrupt::sig2num;
		1465	*sig2name = \&Async::Interrupt::sig2name;
		1466	} else {
		1467	require Config;
		1468
		1469	my %signame2num;
		1470	@signame2num{ split ' ', $Config::Config{sig_name} }
		1471	= split ' ', $Config::Config{sig_num};
		1472
		1473	my @signum2name;
		1474	@signum2name[values %signame2num] = keys %signame2num;
		1475
		1476	*sig2num = sub($) {
		1477	$_[0] > 0 ? shift : $signame2num{+shift}
		1478	};
		1479	*sig2name = sub ($) {
		1480	$_[0] > 0 ? $signum2name[+shift] : shift
		1481	};
		1482	}
		1483	};
		1484	die if $@;
		1485	};
		1486
		1487	sub sig2num ($) { &$_sig_name_init; &sig2num }
		1488	sub sig2name($) { &$_sig_name_init; &sig2name }
551		1489
552	sub signal {	1490	sub signal {
		1491	eval q{ # poor man's autoloading {}
		1492	# probe for availability of Async::Interrupt
		1493	if (_have_async_interrupt) {
		1494	warn "AnyEvent: using Async::Interrupt for race-free signal handling.\n" if $VERBOSE >= 8;
		1495
		1496	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1497	$SIG_IO = AE::io $SIGPIPE_R->fileno, 0, \&_signal_exec;
		1498
		1499	} else {
		1500	warn "AnyEvent: using emulated perl signal handling with latency timer.\n" if $VERBOSE >= 8;
		1501
		1502	require Fcntl;
		1503
		1504	if (AnyEvent::WIN32) {
		1505	require AnyEvent::Util;
		1506
		1507	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1508	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R, 1) if $SIGPIPE_R;
		1509	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W, 1) if $SIGPIPE_W; # just in case
		1510	} else {
		1511	pipe $SIGPIPE_R, $SIGPIPE_W;
		1512	fcntl $SIGPIPE_R, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_R;
		1513	fcntl $SIGPIPE_W, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_W; # just in case
		1514
		1515	# not strictly required, as $^F is normally 2, but let's make sure...
		1516	fcntl $SIGPIPE_R, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1517	fcntl $SIGPIPE_W, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1518	}
		1519
		1520	$SIGPIPE_R
		1521	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1522
		1523	$SIG_IO = AE::io $SIGPIPE_R, 0, \&_signal_exec;
		1524	}
		1525
		1526	*signal = sub {
553	my (undef, %arg) = @_;	1527	my (undef, %arg) = @_;
554		1528
555	my $signal = uc $arg{signal}	1529	my $signal = uc $arg{signal}
556	or Carp::croak "required option 'signal' is missing";	1530	or Carp::croak "required option 'signal' is missing";
557		1531
		1532	if ($HAVE_ASYNC_INTERRUPT) {
		1533	# async::interrupt
		1534
		1535	$signal = sig2num $signal;
558	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1536	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1537
		1538	$SIG_ASY{$signal} ||= new Async::Interrupt
		1539	cb => sub { undef $SIG_EV{$signal} },
		1540	signal => $signal,
		1541	pipe => [$SIGPIPE_R->filenos],
		1542	pipe_autodrain => 0,
		1543	;
		1544
		1545	} else {
		1546	# pure perl
		1547
		1548	# AE::Util has been loaded in signal
		1549	$signal = sig2name $signal;
		1550	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1551
559	$SIG{$signal} ||= sub {	1552	$SIG{$signal} ||= sub {
560	$_->() for values %{ $SIG_CB{$signal} || {} };	1553	local $!;
		1554	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1555	undef $SIG_EV{$signal};
		1556	};
		1557
		1558	# can't do signal processing without introducing races in pure perl,
		1559	# so limit the signal latency.
		1560	_sig_add;
		1561	}
		1562
		1563	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1564	};
		1565
		1566	*AnyEvent::Base::signal::DESTROY = sub {
		1567	my ($signal, $cb) = @{$_[0]};
		1568
		1569	_sig_del;
		1570
		1571	delete $SIG_CB{$signal}{$cb};
		1572
		1573	$HAVE_ASYNC_INTERRUPT
		1574	? delete $SIG_ASY{$signal}
		1575	: # delete doesn't work with older perls - they then
		1576	# print weird messages, or just unconditionally exit
		1577	# instead of getting the default action.
		1578	undef $SIG{$signal}
		1579	unless keys %{ $SIG_CB{$signal} };
		1580	};
561	};	1581	};
562		1582	die if $@;
563	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1583	&signal
564	}
565
566	sub AnyEvent::Base::Signal::DESTROY {
567	my ($signal, $cb) = @{$_[0]};
568
569	delete $SIG_CB{$signal}{$cb};
570
571	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };
572	}	1584	}
573		1585
574	# default implementation for ->child	1586	# default implementation for ->child
575		1587
576	our %PID_CB;	1588	our %PID_CB;
577	our $CHLD_W;	1589	our $CHLD_W;
578	our $CHLD_DELAY_W;	1590	our $CHLD_DELAY_W;
579	our $PID_IDLE;
580	our $WNOHANG;	1591	our $WNOHANG;
581		1592
582	sub _child_wait {	1593	sub _emit_childstatus($$) {
583	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1594	my (undef, $rpid, $rstatus) = @_;
		1595
		1596	$_->($rpid, $rstatus)
584	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1597	for values %{ $PID_CB{$rpid} || {} },
585	(values %{ $PID_CB{0} || {} });	1598	values %{ $PID_CB{0} || {} };
586	}
587
588	undef $PID_IDLE;
589	}	1599	}
590		1600
591	sub _sigchld {	1601	sub _sigchld {
592	# make sure we deliver these changes "synchronous" with the event loop.	1602	my $pid;
593	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {	1603
594	undef $CHLD_DELAY_W;	1604	AnyEvent->_emit_childstatus ($pid, $?)
595	&_child_wait;	1605	while ($pid = waitpid -1, $WNOHANG) > 0;
596	});
597	}	1606	}
598		1607
599	sub child {	1608	sub child {
600	my (undef, %arg) = @_;	1609	my (undef, %arg) = @_;
601		1610
602	defined (my $pid = $arg{pid} + 0)	1611	defined (my $pid = $arg{pid} + 0)
603	or Carp::croak "required option 'pid' is missing";	1612	or Carp::croak "required option 'pid' is missing";
604		1613
605	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1614	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
606		1615
607	unless ($WNOHANG) {	1616	# WNOHANG is almost cetrainly 1 everywhere
608	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;	1617	$WNOHANG ||= $^O =~ /^(?:openbsd|netbsd|linux|freebsd|cygwin|MSWin32)$/
609	}	1618	? 1
		1619	: eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
610		1620
611	unless ($CHLD_W) {	1621	unless ($CHLD_W) {
612	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1622	$CHLD_W = AE::signal CHLD => \&_sigchld;
613	# child could be a zombie already, so make at least one round	1623	# child could be a zombie already, so make at least one round
614	&_sigchld;	1624	&_sigchld;
615	}	1625	}
616		1626
617	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	1627	bless [$pid, $arg{cb}], "AnyEvent::Base::child"
618	}	1628	}
619		1629
620	sub AnyEvent::Base::Child::DESTROY {	1630	sub AnyEvent::Base::child::DESTROY {
621	my ($pid, $cb) = @{$_[0]};	1631	my ($pid, $cb) = @{$_[0]};
622		1632
623	delete $PID_CB{$pid}{$cb};	1633	delete $PID_CB{$pid}{$cb};
624	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1634	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
625		1635
626	undef $CHLD_W unless keys %PID_CB;	1636	undef $CHLD_W unless keys %PID_CB;
627	}	1637	}
		1638
		1639	# idle emulation is done by simply using a timer, regardless
		1640	# of whether the process is idle or not, and not letting
		1641	# the callback use more than 50% of the time.
		1642	sub idle {
		1643	my (undef, %arg) = @_;
		1644
		1645	my ($cb, $w, $rcb) = $arg{cb};
		1646
		1647	$rcb = sub {
		1648	if ($cb) {
		1649	$w = _time;
		1650	&$cb;
		1651	$w = _time - $w;
		1652
		1653	# never use more then 50% of the time for the idle watcher,
		1654	# within some limits
		1655	$w = 0.0001 if $w < 0.0001;
		1656	$w = 5 if $w > 5;
		1657
		1658	$w = AE::timer $w, 0, $rcb;
		1659	} else {
		1660	# clean up...
		1661	undef $w;
		1662	undef $rcb;
		1663	}
		1664	};
		1665
		1666	$w = AE::timer 0.05, 0, $rcb;
		1667
		1668	bless \\$cb, "AnyEvent::Base::idle"
		1669	}
		1670
		1671	sub AnyEvent::Base::idle::DESTROY {
		1672	undef $${$_[0]};
		1673	}
		1674
		1675	package AnyEvent::CondVar;
		1676
		1677	our @ISA = AnyEvent::CondVar::Base::;
		1678
		1679	package AnyEvent::CondVar::Base;
		1680
		1681	#use overload
		1682	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1683	# fallback => 1;
		1684
		1685	# save 300+ kilobytes by dirtily hardcoding overloading
		1686	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1687	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1688	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1689	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1690
		1691	our $WAITING;
		1692
		1693	sub _send {
		1694	# nop
		1695	}
		1696
		1697	sub send {
		1698	my $cv = shift;
		1699	$cv->{_ae_sent} = [@_];
		1700	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1701	$cv->_send;
		1702	}
		1703
		1704	sub croak {
		1705	$_[0]{_ae_croak} = $_[1];
		1706	$_[0]->send;
		1707	}
		1708
		1709	sub ready {
		1710	$_[0]{_ae_sent}
		1711	}
		1712
		1713	sub _wait {
		1714	$WAITING
		1715	and !$_[0]{_ae_sent}
		1716	and Carp::croak "AnyEvent::CondVar: recursive blocking wait detected";
		1717
		1718	local $WAITING = 1;
		1719	AnyEvent->one_event while !$_[0]{_ae_sent};
		1720	}
		1721
		1722	sub recv {
		1723	$_[0]->_wait;
		1724
		1725	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
		1726	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
		1727	}
		1728
		1729	sub cb {
		1730	my $cv = shift;
		1731
		1732	@_
		1733	and $cv->{_ae_cb} = shift
		1734	and $cv->{_ae_sent}
		1735	and (delete $cv->{_ae_cb})->($cv);
		1736
		1737	$cv->{_ae_cb}
		1738	}
		1739
		1740	sub begin {
		1741	++$_[0]{_ae_counter};
		1742	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
		1743	}
		1744
		1745	sub end {
		1746	return if --$_[0]{_ae_counter};
		1747	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		1748	}
		1749
		1750	# undocumented/compatibility with pre-3.4
		1751	*broadcast = \&send;
		1752	*wait = \&_wait;
		1753
		1754	=head1 ERROR AND EXCEPTION HANDLING
		1755
		1756	In general, AnyEvent does not do any error handling - it relies on the
		1757	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1758	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1759	checking of all AnyEvent methods, however, which is highly useful during
		1760	development.
		1761
		1762	As for exception handling (i.e. runtime errors and exceptions thrown while
		1763	executing a callback), this is not only highly event-loop specific, but
		1764	also not in any way wrapped by this module, as this is the job of the main
		1765	program.
		1766
		1767	The pure perl event loop simply re-throws the exception (usually
		1768	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1769	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1770	so on.
		1771
		1772	=head1 ENVIRONMENT VARIABLES
		1773
		1774	The following environment variables are used by this module or its
		1775	submodules.
		1776
		1777	Note that AnyEvent will remove I<all> environment variables starting with
		1778	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		1779	enabled.
		1780
		1781	=over 4
		1782
		1783	=item C<PERL_ANYEVENT_VERBOSE>
		1784
		1785	By default, AnyEvent will be completely silent except in fatal
		1786	conditions. You can set this environment variable to make AnyEvent more
		1787	talkative.
		1788
		1789	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1790	conditions, such as not being able to load the event model specified by
		1791	C<PERL_ANYEVENT_MODEL>.
		1792
		1793	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1794	model it chooses.
		1795
		1796	When set to C<8> or higher, then AnyEvent will report extra information on
		1797	which optional modules it loads and how it implements certain features.
		1798
		1799	=item C<PERL_ANYEVENT_STRICT>
		1800
		1801	AnyEvent does not do much argument checking by default, as thorough
		1802	argument checking is very costly. Setting this variable to a true value
		1803	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1804	check the arguments passed to most method calls. If it finds any problems,
		1805	it will croak.
		1806
		1807	In other words, enables "strict" mode.
		1808
		1809	Unlike C<use strict> (or it's modern cousin, C<< use L<common::sense>
		1810	>>, it is definitely recommended to keep it off in production. Keeping
		1811	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		1812	can be very useful, however.
		1813
		1814	=item C<PERL_ANYEVENT_MODEL>
		1815
		1816	This can be used to specify the event model to be used by AnyEvent, before
		1817	auto detection and -probing kicks in. It must be a string consisting
		1818	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1819	and the resulting module name is loaded and if the load was successful,
		1820	used as event model. If it fails to load AnyEvent will proceed with
		1821	auto detection and -probing.
		1822
		1823	This functionality might change in future versions.
		1824
		1825	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1826	could start your program like this:
		1827
		1828	PERL_ANYEVENT_MODEL=Perl perl ...
		1829
		1830	=item C<PERL_ANYEVENT_PROTOCOLS>
		1831
		1832	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1833	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1834	of auto probing).
		1835
		1836	Must be set to a comma-separated list of protocols or address families,
		1837	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1838	used, and preference will be given to protocols mentioned earlier in the
		1839	list.
		1840
		1841	This variable can effectively be used for denial-of-service attacks
		1842	against local programs (e.g. when setuid), although the impact is likely
		1843	small, as the program has to handle conenction and other failures anyways.
		1844
		1845	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1846	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1847	- only support IPv4, never try to resolve or contact IPv6
		1848	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1849	IPv6, but prefer IPv6 over IPv4.
		1850
		1851	=item C<PERL_ANYEVENT_EDNS0>
		1852
		1853	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1854	for DNS. This extension is generally useful to reduce DNS traffic, but
		1855	some (broken) firewalls drop such DNS packets, which is why it is off by
		1856	default.
		1857
		1858	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1859	EDNS0 in its DNS requests.
		1860
		1861	=item C<PERL_ANYEVENT_MAX_FORKS>
		1862
		1863	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1864	will create in parallel.
		1865
		1866	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		1867
		1868	The default value for the C<max_outstanding> parameter for the default DNS
		1869	resolver - this is the maximum number of parallel DNS requests that are
		1870	sent to the DNS server.
		1871
		1872	=item C<PERL_ANYEVENT_RESOLV_CONF>
		1873
		1874	The file to use instead of F</etc/resolv.conf> (or OS-specific
		1875	configuration) in the default resolver. When set to the empty string, no
		1876	default config will be used.
		1877
		1878	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		1879
		1880	When neither C<ca_file> nor C<ca_path> was specified during
		1881	L<AnyEvent::TLS> context creation, and either of these environment
		1882	variables exist, they will be used to specify CA certificate locations
		1883	instead of a system-dependent default.
		1884
		1885	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		1886
		1887	When these are set to C<1>, then the respective modules are not
		1888	loaded. Mostly good for testing AnyEvent itself.
		1889
		1890	=back
628		1891
629	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1892	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
630		1893
631	This is an advanced topic that you do not normally need to use AnyEvent in	1894	This is an advanced topic that you do not normally need to use AnyEvent in
632	a module. This section is only of use to event loop authors who want to	1895	a module. This section is only of use to event loop authors who want to
…		…
667	I<rxvt-unicode> also cheats a bit by not providing blocking access to	1930	I<rxvt-unicode> also cheats a bit by not providing blocking access to
668	condition variables: code blocking while waiting for a condition will	1931	condition variables: code blocking while waiting for a condition will
669	C<die>. This still works with most modules/usages, and blocking calls must	1932	C<die>. This still works with most modules/usages, and blocking calls must
670	not be done in an interactive application, so it makes sense.	1933	not be done in an interactive application, so it makes sense.
671		1934
672	=head1 ENVIRONMENT VARIABLES
673
674	The following environment variables are used by this module:
675
676	=over 4
677
678	=item C<PERL_ANYEVENT_VERBOSE>
679
680	By default, AnyEvent will be completely silent except in fatal
681	conditions. You can set this environment variable to make AnyEvent more
682	talkative.
683
684	When set to C<1> or higher, causes AnyEvent to warn about unexpected
685	conditions, such as not being able to load the event model specified by
686	C<PERL_ANYEVENT_MODEL>.
687
688	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
689	model it chooses.
690
691	=item C<PERL_ANYEVENT_MODEL>
692
693	This can be used to specify the event model to be used by AnyEvent, before
694	autodetection and -probing kicks in. It must be a string consisting
695	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
696	and the resulting module name is loaded and if the load was successful,
697	used as event model. If it fails to load AnyEvent will proceed with
698	autodetection and -probing.
699
700	This functionality might change in future versions.
701
702	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
703	could start your program like this:
704
705	PERL_ANYEVENT_MODEL=Perl perl ...
706
707	=back
708
709	=head1 EXAMPLE PROGRAM	1935	=head1 EXAMPLE PROGRAM
710		1936
711	The following program uses an IO watcher to read data from STDIN, a timer	1937	The following program uses an I/O watcher to read data from STDIN, a timer
712	to display a message once per second, and a condition variable to quit the	1938	to display a message once per second, and a condition variable to quit the
713	program when the user enters quit:	1939	program when the user enters quit:
714		1940
715	use AnyEvent;	1941	use AnyEvent;
716		1942
…		…
721	poll => 'r',	1947	poll => 'r',
722	cb => sub {	1948	cb => sub {
723	warn "io event <$_[0]>\n"; # will always output <r>	1949	warn "io event <$_[0]>\n"; # will always output <r>
724	chomp (my $input = <STDIN>); # read a line	1950	chomp (my $input = <STDIN>); # read a line
725	warn "read: $input\n"; # output what has been read	1951	warn "read: $input\n"; # output what has been read
726	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	1952	$cv->send if $input =~ /^q/i; # quit program if /^q/i
727	},	1953	},
728	);	1954	);
729		1955
730	my $time_watcher; # can only be used once
731
732	sub new_timer {
733	$timer = AnyEvent->timer (after => 1, cb => sub {	1956	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
734	warn "timeout\n"; # print 'timeout' about every second	1957	warn "timeout\n"; # print 'timeout' at most every second
735	&new_timer; # and restart the time
736	});	1958	});
737	}
738		1959
739	new_timer; # create first timer
740
741	$cv->wait; # wait until user enters /^q/i	1960	$cv->recv; # wait until user enters /^q/i
742		1961
743	=head1 REAL-WORLD EXAMPLE	1962	=head1 REAL-WORLD EXAMPLE
744		1963
745	Consider the L<Net::FCP> module. It features (among others) the following	1964	Consider the L<Net::FCP> module. It features (among others) the following
746	API calls, which are to freenet what HTTP GET requests are to http:	1965	API calls, which are to freenet what HTTP GET requests are to http:
…		…
796	syswrite $txn->{fh}, $txn->{request}	2015	syswrite $txn->{fh}, $txn->{request}
797	or die "connection or write error";	2016	or die "connection or write error";
798	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	2017	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
799		2018
800	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	2019	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
801	result and signals any possible waiters that the request ahs finished:	2020	result and signals any possible waiters that the request has finished:
802		2021
803	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	2022	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
804		2023
805	if (end-of-file or data complete) {	2024	if (end-of-file or data complete) {
806	$txn->{result} = $txn->{buf};	2025	$txn->{result} = $txn->{buf};
807	$txn->{finished}->broadcast;	2026	$txn->{finished}->send;
808	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	2027	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
809	}	2028	}
810		2029
811	The C<result> method, finally, just waits for the finished signal (if the	2030	The C<result> method, finally, just waits for the finished signal (if the
812	request was already finished, it doesn't wait, of course, and returns the	2031	request was already finished, it doesn't wait, of course, and returns the
813	data:	2032	data:
814		2033
815	$txn->{finished}->wait;	2034	$txn->{finished}->recv;
816	return $txn->{result};	2035	return $txn->{result};
817		2036
818	The actual code goes further and collects all errors (C<die>s, exceptions)	2037	The actual code goes further and collects all errors (C<die>s, exceptions)
819	that occured during request processing. The C<result> method detects	2038	that occurred during request processing. The C<result> method detects
820	whether an exception as thrown (it is stored inside the $txn object)	2039	whether an exception as thrown (it is stored inside the $txn object)
821	and just throws the exception, which means connection errors and other	2040	and just throws the exception, which means connection errors and other
822	problems get reported tot he code that tries to use the result, not in a	2041	problems get reported tot he code that tries to use the result, not in a
823	random callback.	2042	random callback.
824		2043
…		…
855		2074
856	my $quit = AnyEvent->condvar;	2075	my $quit = AnyEvent->condvar;
857		2076
858	$fcp->txn_client_get ($url)->cb (sub {	2077	$fcp->txn_client_get ($url)->cb (sub {
859	...	2078	...
860	$quit->broadcast;	2079	$quit->send;
861	});	2080	});
862		2081
863	$quit->wait;	2082	$quit->recv;
864		2083
865		2084
866	=head1 BENCHMARK	2085	=head1 BENCHMARKS
867		2086
868	To give you an idea of the performance and overheads that AnyEvent adds	2087	To give you an idea of the performance and overheads that AnyEvent adds
869	over the event loops themselves (and to give you an impression of the	2088	over the event loops themselves and to give you an impression of the speed
870	speed of various event loops), here is a benchmark of various supported	2089	of various event loops I prepared some benchmarks.
871	event models natively and with anyevent. The benchmark creates a lot of	2090
872	timers (with a zero timeout) and io watchers (watching STDOUT, a pty, to	2091	=head2 BENCHMARKING ANYEVENT OVERHEAD
		2092
		2093	Here is a benchmark of various supported event models used natively and
		2094	through AnyEvent. The benchmark creates a lot of timers (with a zero
		2095	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
873	become writable, which it is), lets them fire exactly once and destroys	2096	which it is), lets them fire exactly once and destroys them again.
874	them again.
875		2097
		2098	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
		2099	distribution. It uses the L<AE> interface, which makes a real difference
		2100	for the EV and Perl backends only.
		2101
876	=head2 Explanation of the columns	2102	=head3 Explanation of the columns
877		2103
878	I<watcher> is the number of event watchers created/destroyed. Since	2104	I<watcher> is the number of event watchers created/destroyed. Since
879	different event models feature vastly different performances, each event	2105	different event models feature vastly different performances, each event
880	loop was given a number of watchers so that overall runtime is acceptable	2106	loop was given a number of watchers so that overall runtime is acceptable
881	and similar between tested event loop (and keep them from crashing): Glib	2107	and similar between tested event loop (and keep them from crashing): Glib
…		…
891	all watchers, to avoid adding memory overhead. That means closure creation	2117	all watchers, to avoid adding memory overhead. That means closure creation
892	and memory usage is not included in the figures.	2118	and memory usage is not included in the figures.
893		2119
894	I<invoke> is the time, in microseconds, used to invoke a simple	2120	I<invoke> is the time, in microseconds, used to invoke a simple
895	callback. The callback simply counts down a Perl variable and after it was	2121	callback. The callback simply counts down a Perl variable and after it was
896	invoked "watcher" times, it would C<< ->broadcast >> a condvar once to	2122	invoked "watcher" times, it would C<< ->send >> a condvar once to
897	signal the end of this phase.	2123	signal the end of this phase.
898		2124
899	I<destroy> is the time, in microseconds, that it takes to destroy a single	2125	I<destroy> is the time, in microseconds, that it takes to destroy a single
900	watcher.	2126	watcher.
901		2127
902	=head2 Results	2128	=head3 Results
903		2129
904	name watchers bytes create invoke destroy comment	2130	name watchers bytes create invoke destroy comment
905	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	2131	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
906	EV/Any 100000 610 3.52 0.91 0.75 EV + AnyEvent watchers	2132	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
907	CoroEV/Any 100000 610 3.49 0.92 0.75 coroutines + Coro::Signal	2133	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
908	Perl/Any 16000 654 4.64 1.22 0.77 pure perl implementation	2134	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
909	Event/Event 16000 523 28.05 21.38 0.86 Event native interface	2135	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
910	Event/Any 16000 943 34.43 20.48 1.39 Event + AnyEvent watchers	2136	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
		2137	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
		2138	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
911	Glib/Any 16000 1357 96.99 12.55 55.51 quadratic behaviour	2139	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
912	Tk/Any 2000 1855 27.01 66.61 14.03 SEGV with >> 2000 watchers	2140	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
913	POE/Event 2000 6644 108.15 768.19 14.33 via POE::Loop::Event	2141	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
914	POE/Select 2000 6343 94.69 807.65 562.69 via POE::Loop::Select	2142	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
915		2143
916	=head2 Discussion	2144	=head3 Discussion
917		2145
918	The benchmark does I<not> measure scalability of the event loop very	2146	The benchmark does I<not> measure scalability of the event loop very
919	well. For example, a select-based event loop (such as the pure perl one)	2147	well. For example, a select-based event loop (such as the pure perl one)
920	can never compete with an event loop that uses epoll when the number of	2148	can never compete with an event loop that uses epoll when the number of
921	file descriptors grows high. In this benchmark, only a single filehandle	2149	file descriptors grows high. In this benchmark, all events become ready at
922	is used (although some of the AnyEvent adaptors dup() its file descriptor	2150	the same time, so select/poll-based implementations get an unnatural speed
923	to worka round bugs).	2151	boost.
		2152
		2153	Also, note that the number of watchers usually has a nonlinear effect on
		2154	overall speed, that is, creating twice as many watchers doesn't take twice
		2155	the time - usually it takes longer. This puts event loops tested with a
		2156	higher number of watchers at a disadvantage.
		2157
		2158	To put the range of results into perspective, consider that on the
		2159	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		2160	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		2161	cycles with POE.
924		2162
925	C<EV> is the sole leader regarding speed and memory use, which are both	2163	C<EV> is the sole leader regarding speed and memory use, which are both
926	maximal/minimal, respectively. Even when going through AnyEvent, there is	2164	maximal/minimal, respectively. When using the L<AE> API there is zero
927	only one event loop that uses less memory (the C<Event> module natively), and	2165	overhead (when going through the AnyEvent API create is about 5-6 times
928	no faster event model, not event C<Event> natively.	2166	slower, with other times being equal, so still uses far less memory than
		2167	any other event loop and is still faster than Event natively).
929		2168
930	The pure perl implementation is hit in a few sweet spots (both the	2169	The pure perl implementation is hit in a few sweet spots (both the
931	zero timeout and the use of a single fd hit optimisations in the perl	2170	constant timeout and the use of a single fd hit optimisations in the perl
932	interpreter and the backend itself). Nevertheless tis shows that it	2171	interpreter and the backend itself). Nevertheless this shows that it
933	adds very little overhead in itself. Like any select-based backend its	2172	adds very little overhead in itself. Like any select-based backend its
934	performance becomes really bad with lots of file descriptors, of course,	2173	performance becomes really bad with lots of file descriptors (and few of
935	but this was not subjetc of this benchmark.	2174	them active), of course, but this was not subject of this benchmark.
936		2175
937	The C<Event> module has a relatively high setup and callback invocation cost,	2176	The C<Event> module has a relatively high setup and callback invocation
938	but overall scores on the third place.	2177	cost, but overall scores in on the third place.
939		2178
		2179	C<IO::Async> performs admirably well, about on par with C<Event>, even
		2180	when using its pure perl backend.
		2181
940	C<Glib>'s memory usage is quite a bit bit higher, but it features a	2182	C<Glib>'s memory usage is quite a bit higher, but it features a
941	faster callback invocation and overall ends up in the same class as	2183	faster callback invocation and overall ends up in the same class as
942	C<Event>. However, Glib scales extremely badly, doubling the number of	2184	C<Event>. However, Glib scales extremely badly, doubling the number of
943	watchers increases the processing time by more than a factor of four,	2185	watchers increases the processing time by more than a factor of four,
944	making it completely unusable when using larger numbers of watchers	2186	making it completely unusable when using larger numbers of watchers
945	(note that only a single file descriptor was used in the benchmark, so	2187	(note that only a single file descriptor was used in the benchmark, so
…		…
948	The C<Tk> adaptor works relatively well. The fact that it crashes with	2190	The C<Tk> adaptor works relatively well. The fact that it crashes with
949	more than 2000 watchers is a big setback, however, as correctness takes	2191	more than 2000 watchers is a big setback, however, as correctness takes
950	precedence over speed. Nevertheless, its performance is surprising, as the	2192	precedence over speed. Nevertheless, its performance is surprising, as the
951	file descriptor is dup()ed for each watcher. This shows that the dup()	2193	file descriptor is dup()ed for each watcher. This shows that the dup()
952	employed by some adaptors is not a big performance issue (it does incur a	2194	employed by some adaptors is not a big performance issue (it does incur a
953	hidden memory cost inside the kernel, though, that is not reflected in the	2195	hidden memory cost inside the kernel which is not reflected in the figures
954	figures above).	2196	above).
955		2197
956	C<POE>, regardless of underlying event loop (wether using its pure perl	2198	C<POE>, regardless of underlying event loop (whether using its pure perl
957	select-based backend or the Event module) shows abysmal performance and	2199	select-based backend or the Event module, the POE-EV backend couldn't
		2200	be tested because it wasn't working) shows abysmal performance and
958	memory usage: Watchers use almost 30 times as much memory as EV watchers,	2201	memory usage with AnyEvent: Watchers use almost 30 times as much memory
959	and 10 times as much memory as both Event or EV via AnyEvent. Watcher	2202	as EV watchers, and 10 times as much memory as Event (the high memory
		2203	requirements are caused by requiring a session for each watcher). Watcher
960	invocation is almost 700 times slower than with AnyEvent's pure perl	2204	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		2205	implementation.
		2206
961	implementation. The design of the POE adaptor class in AnyEvent can not	2207	The design of the POE adaptor class in AnyEvent can not really account
962	really account for this, as session creation overhead is small compared	2208	for the performance issues, though, as session creation overhead is
963	to execution of the state machine, which is coded pretty optimally within	2209	small compared to execution of the state machine, which is coded pretty
964	L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow.	2210	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		2211	using multiple sessions is not a good approach, especially regarding
		2212	memory usage, even the author of POE could not come up with a faster
		2213	design).
965		2214
966	=head2 Summary	2215	=head3 Summary
967		2216
		2217	=over 4
		2218
968	Using EV through AnyEvent is faster than any other event loop, but most	2219	=item * Using EV through AnyEvent is faster than any other event loop
969	event loops have acceptable performance with or without AnyEvent.	2220	(even when used without AnyEvent), but most event loops have acceptable
		2221	performance with or without AnyEvent.
970		2222
971	The overhead AnyEvent adds is usually much smaller than the overhead of	2223	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
972	the actual event loop, only with extremely fast event loops such as the EV	2224	the actual event loop, only with extremely fast event loops such as EV
973	adds AnyEvent significant overhead.	2225	adds AnyEvent significant overhead.
974		2226
975	And you should simply avoid POE like the plague if you want performance or	2227	=item * You should avoid POE like the plague if you want performance or
976	reasonable memory usage.	2228	reasonable memory usage.
977		2229
		2230	=back
		2231
		2232	=head2 BENCHMARKING THE LARGE SERVER CASE
		2233
		2234	This benchmark actually benchmarks the event loop itself. It works by
		2235	creating a number of "servers": each server consists of a socket pair, a
		2236	timeout watcher that gets reset on activity (but never fires), and an I/O
		2237	watcher waiting for input on one side of the socket. Each time the socket
		2238	watcher reads a byte it will write that byte to a random other "server".
		2239
		2240	The effect is that there will be a lot of I/O watchers, only part of which
		2241	are active at any one point (so there is a constant number of active
		2242	fds for each loop iteration, but which fds these are is random). The
		2243	timeout is reset each time something is read because that reflects how
		2244	most timeouts work (and puts extra pressure on the event loops).
		2245
		2246	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
		2247	(1%) are active. This mirrors the activity of large servers with many
		2248	connections, most of which are idle at any one point in time.
		2249
		2250	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		2251	distribution. It uses the L<AE> interface, which makes a real difference
		2252	for the EV and Perl backends only.
		2253
		2254	=head3 Explanation of the columns
		2255
		2256	I<sockets> is the number of sockets, and twice the number of "servers" (as
		2257	each server has a read and write socket end).
		2258
		2259	I<create> is the time it takes to create a socket pair (which is
		2260	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		2261
		2262	I<request>, the most important value, is the time it takes to handle a
		2263	single "request", that is, reading the token from the pipe and forwarding
		2264	it to another server. This includes deleting the old timeout and creating
		2265	a new one that moves the timeout into the future.
		2266
		2267	=head3 Results
		2268
		2269	name sockets create request
		2270	EV 20000 62.66 7.99
		2271	Perl 20000 68.32 32.64
		2272	IOAsync 20000 174.06 101.15 epoll
		2273	IOAsync 20000 174.67 610.84 poll
		2274	Event 20000 202.69 242.91
		2275	Glib 20000 557.01 1689.52
		2276	POE 20000 341.54 12086.32 uses POE::Loop::Event
		2277
		2278	=head3 Discussion
		2279
		2280	This benchmark I<does> measure scalability and overall performance of the
		2281	particular event loop.
		2282
		2283	EV is again fastest. Since it is using epoll on my system, the setup time
		2284	is relatively high, though.
		2285
		2286	Perl surprisingly comes second. It is much faster than the C-based event
		2287	loops Event and Glib.
		2288
		2289	IO::Async performs very well when using its epoll backend, and still quite
		2290	good compared to Glib when using its pure perl backend.
		2291
		2292	Event suffers from high setup time as well (look at its code and you will
		2293	understand why). Callback invocation also has a high overhead compared to
		2294	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		2295	uses select or poll in basically all documented configurations.
		2296
		2297	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		2298	clearly fails to perform with many filehandles or in busy servers.
		2299
		2300	POE is still completely out of the picture, taking over 1000 times as long
		2301	as EV, and over 100 times as long as the Perl implementation, even though
		2302	it uses a C-based event loop in this case.
		2303
		2304	=head3 Summary
		2305
		2306	=over 4
		2307
		2308	=item * The pure perl implementation performs extremely well.
		2309
		2310	=item * Avoid Glib or POE in large projects where performance matters.
		2311
		2312	=back
		2313
		2314	=head2 BENCHMARKING SMALL SERVERS
		2315
		2316	While event loops should scale (and select-based ones do not...) even to
		2317	large servers, most programs we (or I :) actually write have only a few
		2318	I/O watchers.
		2319
		2320	In this benchmark, I use the same benchmark program as in the large server
		2321	case, but it uses only eight "servers", of which three are active at any
		2322	one time. This should reflect performance for a small server relatively
		2323	well.
		2324
		2325	The columns are identical to the previous table.
		2326
		2327	=head3 Results
		2328
		2329	name sockets create request
		2330	EV 16 20.00 6.54
		2331	Perl 16 25.75 12.62
		2332	Event 16 81.27 35.86
		2333	Glib 16 32.63 15.48
		2334	POE 16 261.87 276.28 uses POE::Loop::Event
		2335
		2336	=head3 Discussion
		2337
		2338	The benchmark tries to test the performance of a typical small
		2339	server. While knowing how various event loops perform is interesting, keep
		2340	in mind that their overhead in this case is usually not as important, due
		2341	to the small absolute number of watchers (that is, you need efficiency and
		2342	speed most when you have lots of watchers, not when you only have a few of
		2343	them).
		2344
		2345	EV is again fastest.
		2346
		2347	Perl again comes second. It is noticeably faster than the C-based event
		2348	loops Event and Glib, although the difference is too small to really
		2349	matter.
		2350
		2351	POE also performs much better in this case, but is is still far behind the
		2352	others.
		2353
		2354	=head3 Summary
		2355
		2356	=over 4
		2357
		2358	=item * C-based event loops perform very well with small number of
		2359	watchers, as the management overhead dominates.
		2360
		2361	=back
		2362
		2363	=head2 THE IO::Lambda BENCHMARK
		2364
		2365	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2366	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2367	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2368	shouldn't come as a surprise to anybody). As such, the benchmark is
		2369	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2370	very optimal. But how would AnyEvent compare when used without the extra
		2371	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2372
		2373	The benchmark itself creates an echo-server, and then, for 500 times,
		2374	connects to the echo server, sends a line, waits for the reply, and then
		2375	creates the next connection. This is a rather bad benchmark, as it doesn't
		2376	test the efficiency of the framework or much non-blocking I/O, but it is a
		2377	benchmark nevertheless.
		2378
		2379	name runtime
		2380	Lambda/select 0.330 sec
		2381	+ optimized 0.122 sec
		2382	Lambda/AnyEvent 0.327 sec
		2383	+ optimized 0.138 sec
		2384	Raw sockets/select 0.077 sec
		2385	POE/select, components 0.662 sec
		2386	POE/select, raw sockets 0.226 sec
		2387	POE/select, optimized 0.404 sec
		2388
		2389	AnyEvent/select/nb 0.085 sec
		2390	AnyEvent/EV/nb 0.068 sec
		2391	+state machine 0.134 sec
		2392
		2393	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2394	benchmarks actually make blocking connects and use 100% blocking I/O,
		2395	defeating the purpose of an event-based solution. All of the newly
		2396	written AnyEvent benchmarks use 100% non-blocking connects (using
		2397	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2398	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2399	generally require a lot more bookkeeping and event handling than blocking
		2400	connects (which involve a single syscall only).
		2401
		2402	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2403	offers similar expressive power as POE and IO::Lambda, using conventional
		2404	Perl syntax. This means that both the echo server and the client are 100%
		2405	non-blocking, further placing it at a disadvantage.
		2406
		2407	As you can see, the AnyEvent + EV combination even beats the
		2408	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2409	backend easily beats IO::Lambda and POE.
		2410
		2411	And even the 100% non-blocking version written using the high-level (and
		2412	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda
		2413	higher level ("unoptimised") abstractions by a large margin, even though
		2414	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
		2415
		2416	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2417	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2418	part of the IO::Lambda distribution and were used without any changes.
		2419
		2420
		2421	=head1 SIGNALS
		2422
		2423	AnyEvent currently installs handlers for these signals:
		2424
		2425	=over 4
		2426
		2427	=item SIGCHLD
		2428
		2429	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2430	emulation for event loops that do not support them natively. Also, some
		2431	event loops install a similar handler.
		2432
		2433	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2434	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2435
		2436	=item SIGPIPE
		2437
		2438	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2439	when AnyEvent gets loaded.
		2440
		2441	The rationale for this is that AnyEvent users usually do not really depend
		2442	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2443	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2444	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2445	some random socket.
		2446
		2447	The rationale for installing a no-op handler as opposed to ignoring it is
		2448	that this way, the handler will be restored to defaults on exec.
		2449
		2450	Feel free to install your own handler, or reset it to defaults.
		2451
		2452	=back
		2453
		2454	=cut
		2455
		2456	undef $SIG{CHLD}
		2457	if $SIG{CHLD} eq 'IGNORE';
		2458
		2459	$SIG{PIPE} = sub { }
		2460	unless defined $SIG{PIPE};
		2461
		2462	=head1 RECOMMENDED/OPTIONAL MODULES
		2463
		2464	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2465	it's built-in modules) are required to use it.
		2466
		2467	That does not mean that AnyEvent won't take advantage of some additional
		2468	modules if they are installed.
		2469
		2470	This section explains which additional modules will be used, and how they
		2471	affect AnyEvent's operation.
		2472
		2473	=over 4
		2474
		2475	=item L<Async::Interrupt>
		2476
		2477	This slightly arcane module is used to implement fast signal handling: To
		2478	my knowledge, there is no way to do completely race-free and quick
		2479	signal handling in pure perl. To ensure that signals still get
		2480	delivered, AnyEvent will start an interval timer to wake up perl (and
		2481	catch the signals) with some delay (default is 10 seconds, look for
		2482	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2483
		2484	If this module is available, then it will be used to implement signal
		2485	catching, which means that signals will not be delayed, and the event loop
		2486	will not be interrupted regularly, which is more efficient (and good for
		2487	battery life on laptops).
		2488
		2489	This affects not just the pure-perl event loop, but also other event loops
		2490	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2491
		2492	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2493	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2494	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2495	does nothing for those backends.
		2496
		2497	=item L<EV>
		2498
		2499	This module isn't really "optional", as it is simply one of the backend
		2500	event loops that AnyEvent can use. However, it is simply the best event
		2501	loop available in terms of features, speed and stability: It supports
		2502	the AnyEvent API optimally, implements all the watcher types in XS, does
		2503	automatic timer adjustments even when no monotonic clock is available,
		2504	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2505	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2506	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2507
		2508	=item L<Guard>
		2509
		2510	The guard module, when used, will be used to implement
		2511	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2512	lot less memory), but otherwise doesn't affect guard operation much. It is
		2513	purely used for performance.
		2514
		2515	=item L<JSON> and L<JSON::XS>
		2516
		2517	One of these modules is required when you want to read or write JSON data
		2518	via L<AnyEvent::Handle>. It is also written in pure-perl, but can take
		2519	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2520
		2521	In fact, L<AnyEvent::Handle> will use L<JSON::XS> by default if it is
		2522	installed.
		2523
		2524	=item L<Net::SSLeay>
		2525
		2526	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2527	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2528	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2529
		2530	=item L<Time::HiRes>
		2531
		2532	This module is part of perl since release 5.008. It will be used when the
		2533	chosen event library does not come with a timing source on it's own. The
		2534	pure-perl event loop (L<AnyEvent::Impl::Perl>) will additionally use it to
		2535	try to use a monotonic clock for timing stability.
		2536
		2537	=back
		2538
978		2539
979	=head1 FORK	2540	=head1 FORK
980		2541
981	Most event libraries are not fork-safe. The ones who are usually are	2542	Most event libraries are not fork-safe. The ones who are usually are
982	because they are so inefficient. Only L<EV> is fully fork-aware.	2543	because they rely on inefficient but fork-safe C<select> or C<poll> calls
		2544	- higher performance APIs such as BSD's kqueue or the dreaded Linux epoll
		2545	are usually badly thought-out hacks that are incompatible with fork in
		2546	one way or another. Only L<EV> is fully fork-aware and ensures that you
		2547	continue event-processing in both parent and child (or both, if you know
		2548	what you are doing).
		2549
		2550	This means that, in general, you cannot fork and do event processing in
		2551	the child if the event library was initialised before the fork (which
		2552	usually happens when the first AnyEvent watcher is created, or the library
		2553	is loaded).
983		2554
984	If you have to fork, you must either do so I<before> creating your first	2555	If you have to fork, you must either do so I<before> creating your first
985	watcher OR you must not use AnyEvent at all in the child.	2556	watcher OR you must not use AnyEvent at all in the child OR you must do
		2557	something completely out of the scope of AnyEvent.
		2558
		2559	The problem of doing event processing in the parent I<and> the child
		2560	is much more complicated: even for backends that I<are> fork-aware or
		2561	fork-safe, their behaviour is not usually what you want: fork clones all
		2562	watchers, that means all timers, I/O watchers etc. are active in both
		2563	parent and child, which is almost never what you want. USing C<exec>
		2564	to start worker children from some kind of manage rprocess is usually
		2565	preferred, because it is much easier and cleaner, at the expense of having
		2566	to have another binary.
986		2567
987		2568
988	=head1 SECURITY CONSIDERATIONS	2569	=head1 SECURITY CONSIDERATIONS
989		2570
990	AnyEvent can be forced to load any event model via	2571	AnyEvent can be forced to load any event model via
…		…
995	specified in the variable.	2576	specified in the variable.
996		2577
997	You can make AnyEvent completely ignore this variable by deleting it	2578	You can make AnyEvent completely ignore this variable by deleting it
998	before the first watcher gets created, e.g. with a C<BEGIN> block:	2579	before the first watcher gets created, e.g. with a C<BEGIN> block:
999		2580
1000	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	2581	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1001		2582
1002	use AnyEvent;	2583	use AnyEvent;
		2584
		2585	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		2586	be used to probe what backend is used and gain other information (which is
		2587	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2588	$ENV{PERL_ANYEVENT_STRICT}.
		2589
		2590	Note that AnyEvent will remove I<all> environment variables starting with
		2591	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2592	enabled.
		2593
		2594
		2595	=head1 BUGS
		2596
		2597	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2598	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2599	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2600	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2601	pronounced).
1003		2602
1004		2603
1005	=head1 SEE ALSO	2604	=head1 SEE ALSO
1006		2605
1007	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	2606	Utility functions: L<AnyEvent::Util>.
1008	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,	2607
		2608	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
1009	L<Event::Lib>, L<Qt>, L<POE>.	2609	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
1010		2610
1011	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	2611	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
		2612	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
		2613	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1012	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,	2614	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>, L<Anyevent::Impl::Irssi>.
1013	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,
1014	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.
1015		2615
		2616	Non-blocking file handles, sockets, TCP clients and
		2617	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
		2618
		2619	Asynchronous DNS: L<AnyEvent::DNS>.
		2620
		2621	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>,
		2622	L<Coro::Event>,
		2623
1016	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	2624	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::XMPP>,
		2625	L<AnyEvent::HTTP>.
1017		2626
1018		2627
1019	=head1 AUTHOR	2628	=head1 AUTHOR
1020		2629
1021	Marc Lehmann <schmorp@schmorp.de>	2630	Marc Lehmann <schmorp@schmorp.de>
1022	http://home.schmorp.de/	2631	http://home.schmorp.de/
1023		2632
1024	=cut	2633	=cut
1025		2634
1026	1	2635	1
1027		2636

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