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Revision 1.312 by root, Mon Feb 15 18:02:35 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 ->send	36	$w->recv; # enters "main loop" till $condvar gets ->send
21	$w->send; # wake up current and all future wait's	37	# use a condvar in callback mode:
		38	$w->cb (sub { $_[0]->recv });
		39
		40	=head1 INTRODUCTION/TUTORIAL
		41
		42	This manpage is mainly a reference manual. If you are interested
		43	in a tutorial or some gentle introduction, have a look at the
		44	L<AnyEvent::Intro> manpage.
		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		108
71	=head1 DESCRIPTION	109	=head1 DESCRIPTION
72		110
…		…
78	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>
79	module.	117	module.
80		118
81	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
82	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
83	following modules is already loaded: L<Coro::EV>, L<Coro::Event>, L<EV>,	121	following modules is already loaded: L<EV>,
84	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,	122	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,
85	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
86	to load these modules (excluding Tk, 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
87	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
88	be successfully loaded will be used. If, after this, still none could be	126	be successfully loaded will be used. If, after this, still none could be
…		…
102	starts using it, all bets are off. Maybe you should tell their authors to	140	starts using it, all bets are off. Maybe you should tell their authors to
103	use AnyEvent so their modules work together with others seamlessly...	141	use AnyEvent so their modules work together with others seamlessly...
104		142
105	The pure-perl implementation of AnyEvent is called	143	The pure-perl implementation of AnyEvent is called
106	C<AnyEvent::Impl::Perl>. Like other event modules you can load it	144	C<AnyEvent::Impl::Perl>. Like other event modules you can load it
107	explicitly.	145	explicitly and enjoy the high availability of that event loop :)
108		146
109	=head1 WATCHERS	147	=head1 WATCHERS
110		148
111	AnyEvent has the central concept of a I<watcher>, which is an object that	149	AnyEvent has the central concept of a I<watcher>, which is an object that
112	stores relevant data for each kind of event you are waiting for, such as	150	stores relevant data for each kind of event you are waiting for, such as
113	the callback to call, the filehandle to watch, etc.	151	the callback to call, the file handle to watch, etc.
114		152
115	These watchers are normal Perl objects with normal Perl lifetime. After	153	These watchers are normal Perl objects with normal Perl lifetime. After
116	creating a watcher it will immediately "watch" for events and invoke the	154	creating a watcher it will immediately "watch" for events and invoke the
117	callback when the event occurs (of course, only when the event model	155	callback when the event occurs (of course, only when the event model
118	is in control).	156	is in control).
119		157
		158	Note that B<callbacks must not permanently change global variables>
		159	potentially in use by the event loop (such as C<$_> or C<$[>) and that B<<
		160	callbacks must not C<die> >>. The former is good programming practise in
		161	Perl and the latter stems from the fact that exception handling differs
		162	widely between event loops.
		163
120	To disable the watcher you have to destroy it (e.g. by setting the	164	To disable the watcher you have to destroy it (e.g. by setting the
121	variable you store it in to C<undef> or otherwise deleting all references	165	variable you store it in to C<undef> or otherwise deleting all references
122	to it).	166	to it).
123		167
124	All watchers are created by calling a method on the C<AnyEvent> class.	168	All watchers are created by calling a method on the C<AnyEvent> class.
…		…
126	Many watchers either are used with "recursion" (repeating timers for	170	Many watchers either are used with "recursion" (repeating timers for
127	example), or need to refer to their watcher object in other ways.	171	example), or need to refer to their watcher object in other ways.
128		172
129	An any way to achieve that is this pattern:	173	An any way to achieve that is this pattern:
130		174
131	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	175	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
132	# you can use $w here, for example to undef it	176	# you can use $w here, for example to undef it
133	undef $w;	177	undef $w;
134	});	178	});
135		179
136	Note that C<my $w; $w => combination. This is necessary because in Perl,	180	Note that C<my $w; $w => combination. This is necessary because in Perl,
137	my variables are only visible after the statement in which they are	181	my variables are only visible after the statement in which they are
138	declared.	182	declared.
139		183
140	=head2 I/O WATCHERS	184	=head2 I/O WATCHERS
141		185
		186	$w = AnyEvent->io (
		187	fh => <filehandle_or_fileno>,
		188	poll => <"r" or "w">,
		189	cb => <callback>,
		190	);
		191
142	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
143	with the following mandatory key-value pairs as arguments:	193	with the following mandatory key-value pairs as arguments:
144		194
145	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch	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
146	for events. C<poll> must be a string that is either C<r> or C<w>,	202	C<poll> must be a string that is either C<r> or C<w>, which creates a
147	which creates a watcher waiting for "r"eadable or "w"ritable events,	203	watcher waiting for "r"eadable or "w"ritable events, respectively.
		204
148	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.
149	becomes ready.
150		206
151	Although the callback might get passed parameters, their value and	207	Although the callback might get passed parameters, their value and
152	presence is undefined and you cannot rely on them. Portable AnyEvent	208	presence is undefined and you cannot rely on them. Portable AnyEvent
153	callbacks cannot use arguments passed to I/O watcher callbacks.	209	callbacks cannot use arguments passed to I/O watcher callbacks.
154		210
…		…
158		214
159	Some event loops issue spurious readyness notifications, so you should	215	Some event loops issue spurious readyness notifications, so you should
160	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
161	handles.	217	handles.
162		218
163	Example:
164
165	# 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
166	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	222	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
167	chomp (my $input = <STDIN>);	223	chomp (my $input = <STDIN>);
168	warn "read: $input\n";	224	warn "read: $input\n";
169	undef $w;	225	undef $w;
170	});	226	});
171		227
172	=head2 TIME WATCHERS	228	=head2 TIME WATCHERS
173		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
174	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 >>
175	method with the following mandatory arguments:	239	method with the following mandatory arguments:
176		240
177	C<after> specifies after how many seconds (fractional values are	241	C<after> specifies after how many seconds (fractional values are
178	supported) the callback should be invoked. C<cb> is the callback to invoke	242	supported) the callback should be invoked. C<cb> is the callback to invoke
…		…
180		244
181	Although the callback might get passed parameters, their value and	245	Although the callback might get passed parameters, their value and
182	presence is undefined and you cannot rely on them. Portable AnyEvent	246	presence is undefined and you cannot rely on them. Portable AnyEvent
183	callbacks cannot use arguments passed to time watcher callbacks.	247	callbacks cannot use arguments passed to time watcher callbacks.
184		248
185	The timer callback will be invoked at most once: if you want a repeating	249	The callback will normally be invoked once only. If you specify another
186	timer you have to create a new watcher (this is a limitation by both Tk	250	parameter, C<interval>, as a strictly positive number (> 0), then the
187	and Glib).	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.
188		254
189	Example:	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.
190		258
191	# fire an event after 7.7 seconds	259	Example: fire an event after 7.7 seconds.
		260
192	my $w = AnyEvent->timer (after => 7.7, cb => sub {	261	my $w = AnyEvent->timer (after => 7.7, cb => sub {
193	warn "timeout\n";	262	warn "timeout\n";
194	});	263	});
195		264
196	# to cancel the timer:	265	# to cancel the timer:
197	undef $w;	266	undef $w;
198		267
199	Example 2:
200
201	# 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.
202	my $w;
203		269
204	my $cb = sub {
205	# cancel the old timer while creating a new one
206	$w = AnyEvent->timer (after => 1, cb => $cb);	270	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		271	warn "timeout\n";
207	};	272	};
208
209	# start the "loop" by creating the first watcher
210	$w = AnyEvent->timer (after => 0.5, cb => $cb);
211		273
212	=head3 TIMING ISSUES	274	=head3 TIMING ISSUES
213		275
214	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
215	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
…		…
227	timers.	289	timers.
228		290
229	AnyEvent always prefers relative timers, if available, matching the	291	AnyEvent always prefers relative timers, if available, matching the
230	AnyEvent API.	292	AnyEvent API.
231		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
232	=head2 SIGNAL WATCHERS	379	=head2 SIGNAL WATCHERS
233		380
		381	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		382
234	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
235	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
236	be invoked whenever a signal occurs.	385	callback to be invoked whenever a signal occurs.
237		386
238	Although the callback might get passed parameters, their value and	387	Although the callback might get passed parameters, their value and
239	presence is undefined and you cannot rely on them. Portable AnyEvent	388	presence is undefined and you cannot rely on them. Portable AnyEvent
240	callbacks cannot use arguments passed to signal watcher callbacks.	389	callbacks cannot use arguments passed to signal watcher callbacks.
241		390
242	Multiple signal occurances can be clumped together into one callback	391	Multiple signal occurrences can be clumped together into one callback
243	invocation, and callback invocation will be synchronous. synchronous means	392	invocation, and callback invocation will be synchronous. Synchronous means
244	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,
245	but it is guarenteed not to interrupt any other callbacks.	394	but it is guaranteed not to interrupt any other callbacks.
246		395
247	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
248	between multiple watchers.	397	between multiple watchers, and AnyEvent will ensure that signals will not
		398	interrupt your program at bad times.
249		399
250	This watcher might use C<%SIG>, so programs overwriting those signals	400	This watcher might use C<%SIG> (depending on the event loop used),
251	directly will likely not work correctly.	401	so programs overwriting those signals directly will likely not work
		402	correctly.
252		403
253	Example: exit on SIGINT	404	Example: exit on SIGINT
254		405
255	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	406	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
256		407
		408	=head3 Restart Behaviour
		409
		410	While restart behaviour is up to the event loop implementation, most will
		411	not restart syscalls (that includes L<Async::Interrupt> and AnyEvent's
		412	pure perl implementation).
		413
		414	=head3 Safe/Unsafe Signals
		415
		416	Perl signals can be either "safe" (synchronous to opcode handling) or
		417	"unsafe" (asynchronous) - the former might get delayed indefinitely, the
		418	latter might corrupt your memory.
		419
		420	AnyEvent signal handlers are, in addition, synchronous to the event loop,
		421	i.e. they will not interrupt your running perl program but will only be
		422	called as part of the normal event handling (just like timer, I/O etc.
		423	callbacks, too).
		424
		425	=head3 Signal Races, Delays and Workarounds
		426
		427	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		428	callbacks to signals in a generic way, which is a pity, as you cannot
		429	do race-free signal handling in perl, requiring C libraries for
		430	this. AnyEvent will try to do it's best, which means in some cases,
		431	signals will be delayed. The maximum time a signal might be delayed is
		432	specified in C<$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
257	=head2 CHILD PROCESS WATCHERS	445	=head2 CHILD PROCESS WATCHERS
258		446
		447	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		448
259	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.
260		450
261	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,
262	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
263	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
264	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
265	and exit status (as returned by waitpid), so unlike other watcher types,	455	(stopped/continued).
266	you I<can> rely on child watcher callback arguments.	456
		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.
		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).
267		465
268	There is a slight catch to child watchers, however: you usually start them	466	There is a slight catch to child watchers, however: you usually start them
269	I<after> the child process was created, and this means the process could	467	I<after> the child process was created, and this means the process could
270	have exited already (and no SIGCHLD will be sent anymore).	468	have exited already (and no SIGCHLD will be sent anymore).
271		469
272	Not all event models handle this correctly (POE doesn't), but even for	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
273	event models that I<do> handle this correctly, they usually need to be	472	that I<do> handle this correctly, they usually need to be loaded before
274	loaded before the process exits (i.e. before you fork in the first place).	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.
275		476
276	This means you cannot create a child watcher as the very first thing in an	477	This means you cannot create a child watcher as the very first
277	AnyEvent program, you I<have> to create at least one watcher before you	478	thing in an AnyEvent program, you I<have> to create at least one
278	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).	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.
279		485
280	Example: fork a process and wait for it	486	Example: fork a process and wait for it
281		487
282	my $done = AnyEvent->condvar;	488	my $done = AnyEvent->condvar;
283		489
284	AnyEvent::detect; # force event module to be initialised
285
286	my $pid = fork or exit 5;	490	my $pid = fork or exit 5;
287		491
288	my $w = AnyEvent->child (	492	my $w = AnyEvent->child (
289	pid => $pid,	493	pid => $pid,
290	cb => sub {	494	cb => sub {
291	my ($pid, $status) = @_;	495	my ($pid, $status) = @_;
292	warn "pid $pid exited with status $status";	496	warn "pid $pid exited with status $status";
293	$done->send;	497	$done->send;
294	},	498	},
295	);	499	);
296		500
297	# do something else, then wait for process exit	501	# do something else, then wait for process exit
298	$done->wait;	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	});
299		543
300	=head2 CONDITION VARIABLES	544	=head2 CONDITION VARIABLES
		545
		546	$cv = AnyEvent->condvar;
		547
		548	$cv->send (<list>);
		549	my @res = $cv->recv;
301		550
302	If you are familiar with some event loops you will know that all of them	551	If you are familiar with some event loops you will know that all of them
303	require you to run some blocking "loop", "run" or similar function that	552	require you to run some blocking "loop", "run" or similar function that
304	will actively watch for new events and call your callbacks.	553	will actively watch for new events and call your callbacks.
305		554
306	AnyEvent is different, it expects somebody else to run the event loop and	555	AnyEvent is slightly different: it expects somebody else to run the event
307	will only block when necessary (usually when told by the user).	556	loop and will only block when necessary (usually when told by the user).
308		557
309	The instrument to do that is called a "condition variable", so called	558	The instrument to do that is called a "condition variable", so called
310	because they represent a condition that must become true.	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.
311		562
312	Condition variables can be created by calling the C<< AnyEvent->condvar	563	Condition variables can be created by calling the C<< AnyEvent->condvar
313	>> method, usually without arguments. The only argument pair allowed is	564	>> method, usually without arguments. The only argument pair allowed is
314	C<cb>, which specifies a callback to be called when the condition variable	565	C<cb>, which specifies a callback to be called when the condition variable
315	becomes true.	566	becomes true, with the condition variable as the first argument (but not
		567	the results).
316		568
317	After creation, the conditon variable is "false" until it becomes "true"	569	After creation, the condition variable is "false" until it becomes "true"
318	by calling the C<send> method.	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).
319		573
320	Condition variables are similar to callbacks, except that you can	574	Condition variables are similar to callbacks, except that you can
321	optionally wait for them. They can also be called merge points - points	575	optionally wait for them. They can also be called merge points - points
322	in time where multiple outstandign events have been processed. And yet	576	in time where multiple outstanding events have been processed. And yet
323	another way to call them is transations - each condition variable can be	577	another way to call them is transactions - each condition variable can be
324	used to represent a transaction, which finishes at some point and delivers	578	used to represent a transaction, which finishes at some point and delivers
325	a result.	579	a result. And yet some people know them as "futures" - a promise to
		580	compute/deliver something that you can wait for.
326		581
327	Condition variables are very useful to signal that something has finished,	582	Condition variables are very useful to signal that something has finished,
328	for example, if you write a module that does asynchronous http requests,	583	for example, if you write a module that does asynchronous http requests,
329	then a condition variable would be the ideal candidate to signal the	584	then a condition variable would be the ideal candidate to signal the
330	availability of results. The user can either act when the callback is	585	availability of results. The user can either act when the callback is
331	called or can synchronously C<< ->wait >> for the results.	586	called or can synchronously C<< ->recv >> for the results.
332		587
333	You can also use them to simulate traditional event loops - for example,	588	You can also use them to simulate traditional event loops - for example,
334	you can block your main program until an event occurs - for example, you	589	you can block your main program until an event occurs - for example, you
335	could C<< ->wait >> in your main program until the user clicks the Quit	590	could C<< ->recv >> in your main program until the user clicks the Quit
336	button of your app, which would C<< ->send >> the "quit" event.	591	button of your app, which would C<< ->send >> the "quit" event.
337		592
338	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
339	two pieces 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
340	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
341	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,
342	as this asks for trouble.	597	as this asks for trouble.
343		598
344	Condition variables are represented by hash refs in perl, and the keys	599	Condition variables are represented by hash refs in perl, and the keys
…		…
349		604
350	There are two "sides" to a condition variable - the "producer side" which	605	There are two "sides" to a condition variable - the "producer side" which
351	eventually calls C<< -> send >>, and the "consumer side", which waits	606	eventually calls C<< -> send >>, and the "consumer side", which waits
352	for the send to occur.	607	for the send to occur.
353		608
354	Example:	609	Example: wait for a timer.
355		610
356	# wait till the result is ready	611	# wait till the result is ready
357	my $result_ready = AnyEvent->condvar;	612	my $result_ready = AnyEvent->condvar;
358		613
359	# do something such as adding a timer	614	# do something such as adding a timer
…		…
364	after => 1,	619	after => 1,
365	cb => sub { $result_ready->send },	620	cb => sub { $result_ready->send },
366	);	621	);
367		622
368	# this "blocks" (while handling events) till the callback	623	# this "blocks" (while handling events) till the callback
369	# calls send	624	# calls ->send
370	$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	});
371		650
372	=head3 METHODS FOR PRODUCERS	651	=head3 METHODS FOR PRODUCERS
373		652
374	These methods should only be used by the producing side, i.e. the	653	These methods should only be used by the producing side, i.e. the
375	code/module that eventually sends the signal. Note that it is also	654	code/module that eventually sends the signal. Note that it is also
…		…
378		657
379	=over 4	658	=over 4
380		659
381	=item $cv->send (...)	660	=item $cv->send (...)
382		661
383	Flag the condition as ready - a running C<< ->wait >> and all further	662	Flag the condition as ready - a running C<< ->recv >> and all further
384	calls to C<wait> will (eventually) return after this method has been	663	calls to C<recv> will (eventually) return after this method has been
385	called. If nobody is waiting the send will be remembered.	664	called. If nobody is waiting the send will be remembered.
386		665
387	If a callback has been set on the condition variable, it is called	666	If a callback has been set on the condition variable, it is called
388	immediately from within send.	667	immediately from within send.
389		668
390	Any arguments passed to the C<send> call will be returned by all	669	Any arguments passed to the C<send> call will be returned by all
391	future C<< ->wait >> calls.	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>.
392		675
393	=item $cv->croak ($error)	676	=item $cv->croak ($error)
394		677
395	Similar to send, but causes all call's wait C<< ->wait >> to invoke	678	Similar to send, but causes all call's to C<< ->recv >> to invoke
396	C<Carp::croak> with the given error message/object/scalar.	679	C<Carp::croak> with the given error message/object/scalar.
397		680
398	This can be used to signal any errors to the condition variable	681	This can be used to signal any errors to the condition variable
399	user/consumer.	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.
400		687
401	=item $cv->begin ([group callback])	688	=item $cv->begin ([group callback])
402		689
403	=item $cv->end	690	=item $cv->end
404		691
…		…
406	one. For example, a function that pings many hosts in parallel might want	693	one. For example, a function that pings many hosts in parallel might want
407	to use a condition variable for the whole process.	694	to use a condition variable for the whole process.
408		695
409	Every call to C<< ->begin >> will increment a counter, and every call to	696	Every call to C<< ->begin >> will increment a counter, and every call to
410	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end	697	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
411	>>, the (last) callback passed to C<begin> will be executed. That callback	698	>>, the (last) callback passed to C<begin> will be executed, passing the
412	is I<supposed> to call C<< ->send >>, but that is not required. If no	699	condvar as first argument. That callback is I<supposed> to call C<< ->send
413	callback was set, C<send> will be called without any arguments.	700	>>, but that is not required. If no group callback was set, C<send> will
		701	be called without any arguments.
414		702
415	Let's clarify this with the ping example:	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:
416		710
417	my $cv = AnyEvent->condvar;	711	my $cv = AnyEvent->condvar;
418		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
419	my %result;	737	my %result;
420	$cv->begin (sub { $cv->send (\%result) });	738	$cv->begin (sub { shift->send (\%result) });
421		739
422	for my $host (@list_of_hosts) {	740	for my $host (@list_of_hosts) {
423	$cv->begin;	741	$cv->begin;
424	ping_host_then_call_callback $host, sub {	742	ping_host_then_call_callback $host, sub {
425	$result{$host} = ...;	743	$result{$host} = ...;
…		…
440	loop, which serves two important purposes: first, it sets the callback	758	loop, which serves two important purposes: first, it sets the callback
441	to be called once the counter reaches C<0>, and second, it ensures that	759	to be called once the counter reaches C<0>, and second, it ensures that
442	C<send> is called even when C<no> hosts are being pinged (the loop	760	C<send> is called even when C<no> hosts are being pinged (the loop
443	doesn't execute once).	761	doesn't execute once).
444		762
445	This is the general pattern when you "fan out" into multiple subrequests:	763	This is the general pattern when you "fan out" into multiple (but
446	use an outer C<begin>/C<end> pair to set the callback and ensure C<end>	764	potentially none) subrequests: use an outer C<begin>/C<end> pair to set
447	is called at least once, and then, for each subrequest you start, call	765	the callback and ensure C<end> is called at least once, and then, for each
448	C<begin> and for eahc subrequest you finish, call C<end>.	766	subrequest you start, call C<begin> and for each subrequest you finish,
		767	call C<end>.
449		768
450	=back	769	=back
451		770
452	=head3 METHODS FOR CONSUMERS	771	=head3 METHODS FOR CONSUMERS
453		772
454	These methods should only be used by the consuming side, i.e. the	773	These methods should only be used by the consuming side, i.e. the
455	code awaits the condition.	774	code awaits the condition.
456		775
457	=over 4	776	=over 4
458		777
459	=item $cv->wait	778	=item $cv->recv
460		779
461	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak	780	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
462	>> methods have been called on c<$cv>, while servicing other watchers	781	>> methods have been called on c<$cv>, while servicing other watchers
463	normally.	782	normally.
464		783
…		…
469	function will call C<croak>.	788	function will call C<croak>.
470		789
471	In list context, all parameters passed to C<send> will be returned,	790	In list context, all parameters passed to C<send> will be returned,
472	in scalar context only the first one will be returned.	791	in scalar context only the first one will be returned.
473		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
474	Not all event models support a blocking wait - some die in that case	800	Not all event models support a blocking wait - some die in that case
475	(programs might want to do that to stay interactive), so I<if you are	801	(programs might want to do that to stay interactive), so I<if you are
476	using this from a module, never require a blocking wait>, but let the	802	using this from a module, never require a blocking wait>. Instead, let the
477	caller decide whether the call will block or not (for example, by coupling	803	caller decide whether the call will block or not (for example, by coupling
478	condition variables with some kind of request results and supporting	804	condition variables with some kind of request results and supporting
479	callbacks so the caller knows that getting the result will not block,	805	callbacks so the caller knows that getting the result will not block,
480	while still suppporting blocking waits if the caller so desires).	806	while still supporting blocking waits if the caller so desires).
481		807
482	Another reason I<never> to C<< ->wait >> in a module is that you cannot
483	sensibly have two C<< ->wait >>'s in parallel, as that would require
484	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
485	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and
486	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
487	from different coroutines, however).
488
489	You can ensure that C<< -wait >> never blocks by setting a callback and	808	You can ensure that C<< -recv >> never blocks by setting a callback and
490	only calling C<< ->wait >> from within that callback (or at a later	809	only calling C<< ->recv >> from within that callback (or at a later
491	time). This will work even when the event loop does not support blocking	810	time). This will work even when the event loop does not support blocking
492	waits otherwise.	811	waits otherwise.
493		812
494	=item $bool = $cv->ready	813	=item $bool = $cv->ready
495		814
496	Returns true when the condition is "true", i.e. whether C<send> or	815	Returns true when the condition is "true", i.e. whether C<send> or
497	C<croak> have been called.	816	C<croak> have been called.
498		817
499	=item $cb = $cv->cb ([new callback])	818	=item $cb = $cv->cb ($cb->($cv))
500		819
501	This is a mutator function that returns the callback set and optionally	820	This is a mutator function that returns the callback set and optionally
502	replaces it before doing so.	821	replaces it before doing so.
503		822
504	The callback will be called when the condition becomes "true", i.e. when	823	The callback will be called when the condition becomes (or already was)
505	C<send> or C<croak> are called. Calling C<wait> inside the callback	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>
506	or at any later time is guaranteed not to block.	826	inside the callback or at any later time is guaranteed not to block.
507		827
508	=back	828	=back
509		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
		897
510	=head1 GLOBAL VARIABLES AND FUNCTIONS	898	=head1 GLOBAL VARIABLES AND FUNCTIONS
511		899
		900	These are not normally required to use AnyEvent, but can be useful to
		901	write AnyEvent extension modules.
		902
512	=over 4	903	=over 4
513		904
514	=item $AnyEvent::MODEL	905	=item $AnyEvent::MODEL
515		906
516	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
517	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
518	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
519	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
520	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
521		914	will be C<urxvt::anyevent>).
522	The known classes so far are:
523
524	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
525	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
526	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
527	AnyEvent::Impl::Event based on Event, second best choice.
528	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
529	AnyEvent::Impl::Glib based on Glib, third-best choice.
530	AnyEvent::Impl::Tk based on Tk, very bad choice.
531	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
532	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
533	AnyEvent::Impl::POE based on POE, not generic enough for full support.
534
535	There is no support for WxWidgets, as WxWidgets has no support for
536	watching file handles. However, you can use WxWidgets through the
537	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
538	second, which was considered to be too horrible to even consider for
539	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
540	it's adaptor.
541
542	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
543	autodetecting them.
544		915
545	=item AnyEvent::detect	916	=item AnyEvent::detect
546		917
547	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	918	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
548	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
549	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
550	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	}
551		993
552	=back	994	=back
553		995
554	=head1 WHAT TO DO IN A MODULE	996	=head1 WHAT TO DO IN A MODULE
555		997
…		…
559	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
560	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
561	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
562	to load the event module first.	1004	to load the event module first.
563		1005
564	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
565	the C<< ->send >> method has been called on it already. This is	1007	the C<< ->send >> method has been called on it already. This is
566	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
567	events is to stay interactive.	1009	events is to stay interactive.
568		1010
569	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
570	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
571	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 >>
572	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).
573		1015
574	=head1 WHAT TO DO IN THE MAIN PROGRAM	1016	=head1 WHAT TO DO IN THE MAIN PROGRAM
575		1017
576	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
…		…
578		1020
579	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
580	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
581	decide which implementation to chose if some module relies on it.	1023	decide which implementation to chose if some module relies on it.
582		1024
583	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
584	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
585	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
586	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
587	modules might create watchers when they are loaded, and AnyEvent will	1029	modules might create watchers when they are loaded, and AnyEvent will
588	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
589	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.
590		1032
591	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
592	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	1034	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
593	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
594		1053
595	=head1 OTHER MODULES	1054	=head1 OTHER MODULES
596		1055
597	The following is a non-exhaustive list of additional modules that use	1056	The following is a non-exhaustive list of additional modules that use
598	AnyEvent and can therefore be mixed easily with other AnyEvent modules	1057	AnyEvent as a client and can therefore be mixed easily with other AnyEvent
599	in the same program. Some of the modules come with AnyEvent, some are	1058	modules and other event loops in the same program. Some of the modules
600	available via CPAN.	1059	come with AnyEvent, most are available via CPAN.
601		1060
602	=over 4	1061	=over 4
603		1062
604	=item L<AnyEvent::Util>	1063	=item L<AnyEvent::Util>
605		1064
606	Contains various utility functions that replace often-used but blocking	1065	Contains various utility functions that replace often-used but blocking
607	functions such as C<inet_aton> by event-/callback-based versions.	1066	functions such as C<inet_aton> by event-/callback-based versions.
608		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
609	=item L<AnyEvent::Handle>	1074	=item L<AnyEvent::Handle>
610		1075
611	Provide read and write buffers and manages watchers for reads and writes.	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>.
612		1079
613	=item L<AnyEvent::Socket>	1080	=item L<AnyEvent::DNS>
614		1081
615	Provides a means to do non-blocking connects, accepts etc.	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.
616		1088
617	=item L<AnyEvent::HTTPD>	1089	=item L<AnyEvent::HTTPD>
618		1090
619	Provides a simple web application server framework.	1091	Provides a simple web application server framework.
620		1092
621	=item L<AnyEvent::DNS>
622
623	Provides asynchronous DNS resolver capabilities, beyond what
624	L<AnyEvent::Util> offers.
625
626	=item L<AnyEvent::FastPing>	1093	=item L<AnyEvent::FastPing>
627		1094
628	The fastest ping in the west.	1095	The fastest ping in the west.
629		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
630	=item L<Net::IRC3>	1116	=item L<AnyEvent::IRC>
631		1117
632	AnyEvent based IRC client module family.	1118	AnyEvent based IRC client module family (replacing the older Net::IRC3).
633		1119
634	=item L<Net::XMPP2>	1120	=item L<AnyEvent::XMPP>
635		1121
636	AnyEvent based XMPP (Jabber protocol) module family.	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>).
637		1129
638	=item L<Net::FCP>	1130	=item L<Net::FCP>
639		1131
640	AnyEvent-based implementation of the Freenet Client Protocol, birthplace	1132	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
641	of AnyEvent.	1133	of AnyEvent.
…		…
644		1136
645	High level API for event-based execution flow control.	1137	High level API for event-based execution flow control.
646		1138
647	=item L<Coro>	1139	=item L<Coro>
648		1140
649	Has special support for AnyEvent.	1141	Has special support for AnyEvent via L<Coro::AnyEvent>.
650
651	=item L<IO::Lambda>
652
653	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
654
655	=item L<IO::AIO>
656
657	Truly asynchronous I/O, should be in the toolbox of every event
658	programmer. Can be trivially made to use AnyEvent.
659
660	=item L<BDB>
661
662	Truly asynchronous Berkeley DB access. Can be trivially made to use
663	AnyEvent.
664		1142
665	=back	1143	=back
666		1144
667	=cut	1145	=cut
668		1146
669	package AnyEvent;	1147	package AnyEvent;
670		1148
671	no warnings;	1149	# basically a tuned-down version of common::sense
672	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	}
673		1156
		1157	BEGIN { AnyEvent::common_sense }
		1158
674	use Carp;	1159	use Carp ();
675		1160
676	our $VERSION = '3.3';	1161	our $VERSION = '5.24';
677	our $MODEL;	1162	our $MODEL;
678		1163
679	our $AUTOLOAD;	1164	our $AUTOLOAD;
680	our @ISA;	1165	our @ISA;
681		1166
682	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
683
684	our @REGISTRY;	1167	our @REGISTRY;
685		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
686	my @models = (	1194	my @models = (
687	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
688	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
689	[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
690	[Event:: => AnyEvent::Impl::Event::],	1200	[Event:: => AnyEvent::Impl::Event::, 1],
		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
691	[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
692	[Wx:: => AnyEvent::Impl::POE::],	1207	[Wx:: => AnyEvent::Impl::POE::],
693	[Prima:: => AnyEvent::Impl::POE::],	1208	[Prima:: => AnyEvent::Impl::POE::],
694	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1209	# IO::Async is just too broken - we would need workarounds for its
695	# everything below here will not be autoprobed as the pureperl backend should work everywhere	1210	# byzantine signal and broken child handling, among others.
696	[Glib:: => AnyEvent::Impl::Glib::],	1211	# IO::Async is rather hard to detect, as it doesn't have any
697	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy	1212	# obvious default class.
698	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program	1213	[IO::Async:: => AnyEvent::Impl::IOAsync::], # requires special main program
699	[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
700	);	1217	);
701		1218
702	our %method = map +($_ => 1), qw(io timer signal child condvar 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	}
703		1243
704	sub detect() {	1244	sub detect() {
		1245	# free some memory
		1246	*detect = sub () { $MODEL };
		1247
		1248	local $!; # for good measure
		1249	local $SIG{__DIE__};
		1250
		1251	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
		1252	my $model = "AnyEvent::Impl::$1";
		1253	if (eval "require $model") {
		1254	$MODEL = $model;
		1255	warn "AnyEvent: loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.\n" if $VERBOSE >= 2;
		1256	} else {
		1257	warn "AnyEvent: unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@" if $VERBOSE;
		1258	}
		1259	}
		1260
		1261	# check for already loaded models
705	unless ($MODEL) {	1262	unless ($MODEL) {
706	no strict 'refs';	1263	for (@REGISTRY, @models) {
707		1264	my ($package, $model) = @$_;
708	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	1265	if (${"$package\::VERSION"} > 0) {
709	my $model = "AnyEvent::Impl::$1";
710	if (eval "require $model") {	1266	if (eval "require $model") {
711	$MODEL = $model;	1267	$MODEL = $model;
712	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	1268	warn "AnyEvent: autodetected model '$model', using it.\n" if $VERBOSE >= 2;
713	} else {	1269	last;
714	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;	1270	}
715	}	1271	}
716	}	1272	}
717		1273
718	# check for already loaded models
719	unless ($MODEL) {	1274	unless ($MODEL) {
		1275	# try to autoload a model
720	for (@REGISTRY, @models) {	1276	for (@REGISTRY, @models) {
721	my ($package, $model) = @$_;	1277	my ($package, $model, $autoload) = @$_;
		1278	if (
		1279	$autoload
		1280	and eval "require $package"
722	if (${"$package\::VERSION"} > 0) {	1281	and ${"$package\::VERSION"} > 0
723	if (eval "require $model") {	1282	and eval "require $model"
		1283	) {
724	$MODEL = $model;	1284	$MODEL = $model;
725	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;	1285	warn "AnyEvent: autoloaded model '$model', using it.\n" if $VERBOSE >= 2;
726	last;	1286	last;
727	}
728	}	1287	}
729	}	1288	}
730		1289
731	unless ($MODEL) {
732	# try to load a model
733
734	for (@REGISTRY, @models) {
735	my ($package, $model) = @$_;
736	if (eval "require $package"
737	and ${"$package\::VERSION"} > 0
738	and eval "require $model") {
739	$MODEL = $model;
740	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;
741	last;
742	}
743	}
744
745	$MODEL	1290	$MODEL
746	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.";	1291	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.\n";
747	}
748	}	1292	}
749
750	unshift @ISA, $MODEL;
751	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
752	}	1293	}
		1294
		1295	@models = (); # free probe data
		1296
		1297	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		1298	unshift @ISA, $MODEL;
		1299
		1300	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
		1301
		1302	(shift @post_detect)->() while @post_detect;
753		1303
754	$MODEL	1304	$MODEL
755	}	1305	}
756		1306
757	sub AUTOLOAD {	1307	sub AUTOLOAD {
758	(my $func = $AUTOLOAD) =~ s/.*://;	1308	(my $func = $AUTOLOAD) =~ s/.*://;
759		1309
760	$method{$func}	1310	$method{$func}
761	or croak "$func: not a valid method for AnyEvent objects";	1311	or Carp::croak "$func: not a valid AnyEvent class method";
762		1312
763	detect unless $MODEL;	1313	detect;
764		1314
765	my $class = shift;	1315	my $class = shift;
766	$class->$func (@_);	1316	$class->$func (@_);
767	}	1317	}
768		1318
		1319	# utility function to dup a filehandle. this is used by many backends
		1320	# to support binding more than one watcher per filehandle (they usually
		1321	# allow only one watcher per fd, so we dup it to get a different one).
		1322	sub _dupfh($$;$$) {
		1323	my ($poll, $fh, $r, $w) = @_;
		1324
		1325	# cygwin requires the fh mode to be matching, unix doesn't
		1326	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1327
		1328	open my $fh2, $mode, $fh
		1329	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1330
		1331	# we assume CLOEXEC is already set by perl in all important cases
		1332
		1333	($fh2, $rw)
		1334	}
		1335
		1336	=head1 SIMPLIFIED AE API
		1337
		1338	Starting with version 5.0, AnyEvent officially supports a second, much
		1339	simpler, API that is designed to reduce the calling, typing and memory
		1340	overhead.
		1341
		1342	See the L<AE> manpage for details.
		1343
		1344	=cut
		1345
		1346	package AE;
		1347
		1348	our $VERSION = $AnyEvent::VERSION;
		1349
		1350	sub io($$$) {
		1351	AnyEvent->io (fh => $_[0], poll => $_[1] ? "w" : "r", cb => $_[2])
		1352	}
		1353
		1354	sub timer($$$) {
		1355	AnyEvent->timer (after => $_[0], interval => $_[1], cb => $_[2])
		1356	}
		1357
		1358	sub signal($$) {
		1359	AnyEvent->signal (signal => $_[0], cb => $_[1])
		1360	}
		1361
		1362	sub child($$) {
		1363	AnyEvent->child (pid => $_[0], cb => $_[1])
		1364	}
		1365
		1366	sub idle($) {
		1367	AnyEvent->idle (cb => $_[0])
		1368	}
		1369
		1370	sub cv(;&) {
		1371	AnyEvent->condvar (@_ ? (cb => $_[0]) : ())
		1372	}
		1373
		1374	sub now() {
		1375	AnyEvent->now
		1376	}
		1377
		1378	sub now_update() {
		1379	AnyEvent->now_update
		1380	}
		1381
		1382	sub time() {
		1383	AnyEvent->time
		1384	}
		1385
769	package AnyEvent::Base;	1386	package AnyEvent::Base;
770		1387
		1388	# default implementations for many methods
		1389
		1390	sub _time() {
		1391	eval q{ # poor man's autoloading
		1392	# probe for availability of Time::HiRes
		1393	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1394	warn "AnyEvent: using Time::HiRes for sub-second timing accuracy.\n" if $VERBOSE >= 8;
		1395	*_time = \&Time::HiRes::time;
		1396	# if (eval "use POSIX (); (POSIX::times())...
		1397	} else {
		1398	warn "AnyEvent: using built-in time(), WARNING, no sub-second resolution!\n" if $VERBOSE;
		1399	*_time = sub (){ time }; # epic fail
		1400	}
		1401	};
		1402	die if $@;
		1403
		1404	&_time
		1405	}
		1406
		1407	sub time { _time }
		1408	sub now { _time }
		1409	sub now_update { }
		1410
771	# default implementation for ->condvar, ->wait, ->broadcast	1411	# default implementation for ->condvar
772		1412
773	sub condvar {	1413	sub condvar {
774	bless \my $flag, "AnyEvent::Base::CondVar"	1414	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
775	}
776
777	sub AnyEvent::Base::CondVar::broadcast {
778	${$_[0]}++;
779	}
780
781	sub AnyEvent::Base::CondVar::wait {
782	AnyEvent->one_event while !${$_[0]};
783	}	1415	}
784		1416
785	# default implementation for ->signal	1417	# default implementation for ->signal
786		1418
787	our %SIG_CB;	1419	our $HAVE_ASYNC_INTERRUPT;
		1420
		1421	sub _have_async_interrupt() {
		1422	$HAVE_ASYNC_INTERRUPT = 1*(!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT}
		1423	&& eval "use Async::Interrupt 1.02 (); 1")
		1424	unless defined $HAVE_ASYNC_INTERRUPT;
		1425
		1426	$HAVE_ASYNC_INTERRUPT
		1427	}
		1428
		1429	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1430	our (%SIG_ASY, %SIG_ASY_W);
		1431	our ($SIG_COUNT, $SIG_TW);
		1432
		1433	# install a dummy wakeup watcher to reduce signal catching latency
		1434	# used by Impls
		1435	sub _sig_add() {
		1436	unless ($SIG_COUNT++) {
		1437	# try to align timer on a full-second boundary, if possible
		1438	my $NOW = AE::now;
		1439
		1440	$SIG_TW = AE::timer
		1441	$MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1442	$MAX_SIGNAL_LATENCY,
		1443	sub { } # just for the PERL_ASYNC_CHECK
		1444	;
		1445	}
		1446	}
		1447
		1448	sub _sig_del {
		1449	undef $SIG_TW
		1450	unless --$SIG_COUNT;
		1451	}
		1452
		1453	our $_sig_name_init; $_sig_name_init = sub {
		1454	eval q{ # poor man's autoloading
		1455	undef $_sig_name_init;
		1456
		1457	if (_have_async_interrupt) {
		1458	*sig2num = \&Async::Interrupt::sig2num;
		1459	*sig2name = \&Async::Interrupt::sig2name;
		1460	} else {
		1461	require Config;
		1462
		1463	my %signame2num;
		1464	@signame2num{ split ' ', $Config::Config{sig_name} }
		1465	= split ' ', $Config::Config{sig_num};
		1466
		1467	my @signum2name;
		1468	@signum2name[values %signame2num] = keys %signame2num;
		1469
		1470	*sig2num = sub($) {
		1471	$_[0] > 0 ? shift : $signame2num{+shift}
		1472	};
		1473	*sig2name = sub ($) {
		1474	$_[0] > 0 ? $signum2name[+shift] : shift
		1475	};
		1476	}
		1477	};
		1478	die if $@;
		1479	};
		1480
		1481	sub sig2num ($) { &$_sig_name_init; &sig2num }
		1482	sub sig2name($) { &$_sig_name_init; &sig2name }
788		1483
789	sub signal {	1484	sub signal {
		1485	eval q{ # poor man's autoloading {}
		1486	# probe for availability of Async::Interrupt
		1487	if (_have_async_interrupt) {
		1488	warn "AnyEvent: using Async::Interrupt for race-free signal handling.\n" if $VERBOSE >= 8;
		1489
		1490	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1491	$SIG_IO = AE::io $SIGPIPE_R->fileno, 0, \&_signal_exec;
		1492
		1493	} else {
		1494	warn "AnyEvent: using emulated perl signal handling with latency timer.\n" if $VERBOSE >= 8;
		1495
		1496	require Fcntl;
		1497
		1498	if (AnyEvent::WIN32) {
		1499	require AnyEvent::Util;
		1500
		1501	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1502	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R, 1) if $SIGPIPE_R;
		1503	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W, 1) if $SIGPIPE_W; # just in case
		1504	} else {
		1505	pipe $SIGPIPE_R, $SIGPIPE_W;
		1506	fcntl $SIGPIPE_R, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_R;
		1507	fcntl $SIGPIPE_W, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_W; # just in case
		1508
		1509	# not strictly required, as $^F is normally 2, but let's make sure...
		1510	fcntl $SIGPIPE_R, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1511	fcntl $SIGPIPE_W, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1512	}
		1513
		1514	$SIGPIPE_R
		1515	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1516
		1517	$SIG_IO = AE::io $SIGPIPE_R, 0, \&_signal_exec;
		1518	}
		1519
		1520	*signal = sub {
790	my (undef, %arg) = @_;	1521	my (undef, %arg) = @_;
791		1522
792	my $signal = uc $arg{signal}	1523	my $signal = uc $arg{signal}
793	or Carp::croak "required option 'signal' is missing";	1524	or Carp::croak "required option 'signal' is missing";
794		1525
		1526	if ($HAVE_ASYNC_INTERRUPT) {
		1527	# async::interrupt
		1528
		1529	$signal = sig2num $signal;
795	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1530	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1531
		1532	$SIG_ASY{$signal} ||= new Async::Interrupt
		1533	cb => sub { undef $SIG_EV{$signal} },
		1534	signal => $signal,
		1535	pipe => [$SIGPIPE_R->filenos],
		1536	pipe_autodrain => 0,
		1537	;
		1538
		1539	} else {
		1540	# pure perl
		1541
		1542	# AE::Util has been loaded in signal
		1543	$signal = sig2name $signal;
		1544	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1545
796	$SIG{$signal} ||= sub {	1546	$SIG{$signal} ||= sub {
		1547	local $!;
		1548	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1549	undef $SIG_EV{$signal};
		1550	};
		1551
		1552	# can't do signal processing without introducing races in pure perl,
		1553	# so limit the signal latency.
		1554	_sig_add;
		1555	}
		1556
		1557	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1558	};
		1559
		1560	*AnyEvent::Base::signal::DESTROY = sub {
		1561	my ($signal, $cb) = @{$_[0]};
		1562
		1563	_sig_del;
		1564
		1565	delete $SIG_CB{$signal}{$cb};
		1566
		1567	$HAVE_ASYNC_INTERRUPT
		1568	? delete $SIG_ASY{$signal}
		1569	: # delete doesn't work with older perls - they then
		1570	# print weird messages, or just unconditionally exit
		1571	# instead of getting the default action.
		1572	undef $SIG{$signal}
		1573	unless keys %{ $SIG_CB{$signal} };
		1574	};
		1575
		1576	*_signal_exec = sub {
		1577	$HAVE_ASYNC_INTERRUPT
		1578	? $SIGPIPE_R->drain
		1579	: sysread $SIGPIPE_R, (my $dummy), 9;
		1580
		1581	while (%SIG_EV) {
		1582	for (keys %SIG_EV) {
		1583	delete $SIG_EV{$_};
797	$_->() for values %{ $SIG_CB{$signal} || {} };	1584	$_->() for values %{ $SIG_CB{$_} || {} };
		1585	}
		1586	}
		1587	};
798	};	1588	};
		1589	die if $@;
799		1590
800	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1591	&signal
801	}
802
803	sub AnyEvent::Base::Signal::DESTROY {
804	my ($signal, $cb) = @{$_[0]};
805
806	delete $SIG_CB{$signal}{$cb};
807
808	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };
809	}	1592	}
810		1593
811	# default implementation for ->child	1594	# default implementation for ->child
812		1595
813	our %PID_CB;	1596	our %PID_CB;
814	our $CHLD_W;	1597	our $CHLD_W;
815	our $CHLD_DELAY_W;	1598	our $CHLD_DELAY_W;
816	our $PID_IDLE;
817	our $WNOHANG;	1599	our $WNOHANG;
818		1600
819	sub _child_wait {	1601	# used by many Impl's
820	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1602	sub _emit_childstatus($$) {
		1603	my (undef, $rpid, $rstatus) = @_;
		1604
		1605	$_->($rpid, $rstatus)
821	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1606	for values %{ $PID_CB{$rpid} || {} },
822	(values %{ $PID_CB{0} || {} });	1607	values %{ $PID_CB{0} || {} };
823	}
824
825	undef $PID_IDLE;
826	}
827
828	sub _sigchld {
829	# make sure we deliver these changes "synchronous" with the event loop.
830	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {
831	undef $CHLD_DELAY_W;
832	&_child_wait;
833	});
834	}	1608	}
835		1609
836	sub child {	1610	sub child {
		1611	eval q{ # poor man's autoloading {}
		1612	*_sigchld = sub {
		1613	my $pid;
		1614
		1615	AnyEvent->_emit_childstatus ($pid, $?)
		1616	while ($pid = waitpid -1, $WNOHANG) > 0;
		1617	};
		1618
		1619	*child = sub {
837	my (undef, %arg) = @_;	1620	my (undef, %arg) = @_;
838		1621
839	defined (my $pid = $arg{pid} + 0)	1622	defined (my $pid = $arg{pid} + 0)
840	or Carp::croak "required option 'pid' is missing";	1623	or Carp::croak "required option 'pid' is missing";
841		1624
842	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1625	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
843		1626
844	unless ($WNOHANG) {	1627	# WNOHANG is almost cetrainly 1 everywhere
845	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;	1628	$WNOHANG ||= $^O =~ /^(?:openbsd|netbsd|linux|freebsd|cygwin|MSWin32)$/
846	}	1629	? 1
		1630	: eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
847		1631
848	unless ($CHLD_W) {	1632	unless ($CHLD_W) {
849	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1633	$CHLD_W = AE::signal CHLD => \&_sigchld;
850	# child could be a zombie already, so make at least one round	1634	# child could be a zombie already, so make at least one round
851	&_sigchld;	1635	&_sigchld;
852	}	1636	}
853		1637
854	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	1638	bless [$pid, $arg{cb}], "AnyEvent::Base::child"
855	}	1639	};
856		1640
857	sub AnyEvent::Base::Child::DESTROY {	1641	*AnyEvent::Base::child::DESTROY = sub {
858	my ($pid, $cb) = @{$_[0]};	1642	my ($pid, $cb) = @{$_[0]};
859		1643
860	delete $PID_CB{$pid}{$cb};	1644	delete $PID_CB{$pid}{$cb};
861	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1645	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
862		1646
863	undef $CHLD_W unless keys %PID_CB;	1647	undef $CHLD_W unless keys %PID_CB;
		1648	};
		1649	};
		1650	die if $@;
		1651
		1652	&child
864	}	1653	}
		1654
		1655	# idle emulation is done by simply using a timer, regardless
		1656	# of whether the process is idle or not, and not letting
		1657	# the callback use more than 50% of the time.
		1658	sub idle {
		1659	eval q{ # poor man's autoloading {}
		1660	*idle = sub {
		1661	my (undef, %arg) = @_;
		1662
		1663	my ($cb, $w, $rcb) = $arg{cb};
		1664
		1665	$rcb = sub {
		1666	if ($cb) {
		1667	$w = _time;
		1668	&$cb;
		1669	$w = _time - $w;
		1670
		1671	# never use more then 50% of the time for the idle watcher,
		1672	# within some limits
		1673	$w = 0.0001 if $w < 0.0001;
		1674	$w = 5 if $w > 5;
		1675
		1676	$w = AE::timer $w, 0, $rcb;
		1677	} else {
		1678	# clean up...
		1679	undef $w;
		1680	undef $rcb;
		1681	}
		1682	};
		1683
		1684	$w = AE::timer 0.05, 0, $rcb;
		1685
		1686	bless \\$cb, "AnyEvent::Base::idle"
		1687	};
		1688
		1689	*AnyEvent::Base::idle::DESTROY = sub {
		1690	undef $${$_[0]};
		1691	};
		1692	};
		1693	die if $@;
		1694
		1695	&idle
		1696	}
		1697
		1698	package AnyEvent::CondVar;
		1699
		1700	our @ISA = AnyEvent::CondVar::Base::;
		1701
		1702	package AnyEvent::CondVar::Base;
		1703
		1704	#use overload
		1705	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1706	# fallback => 1;
		1707
		1708	# save 300+ kilobytes by dirtily hardcoding overloading
		1709	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1710	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1711	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1712	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1713
		1714	our $WAITING;
		1715
		1716	sub _send {
		1717	# nop
		1718	}
		1719
		1720	sub send {
		1721	my $cv = shift;
		1722	$cv->{_ae_sent} = [@_];
		1723	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1724	$cv->_send;
		1725	}
		1726
		1727	sub croak {
		1728	$_[0]{_ae_croak} = $_[1];
		1729	$_[0]->send;
		1730	}
		1731
		1732	sub ready {
		1733	$_[0]{_ae_sent}
		1734	}
		1735
		1736	sub _wait {
		1737	$WAITING
		1738	and !$_[0]{_ae_sent}
		1739	and Carp::croak "AnyEvent::CondVar: recursive blocking wait detected";
		1740
		1741	local $WAITING = 1;
		1742	AnyEvent->one_event while !$_[0]{_ae_sent};
		1743	}
		1744
		1745	sub recv {
		1746	$_[0]->_wait;
		1747
		1748	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
		1749	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
		1750	}
		1751
		1752	sub cb {
		1753	my $cv = shift;
		1754
		1755	@_
		1756	and $cv->{_ae_cb} = shift
		1757	and $cv->{_ae_sent}
		1758	and (delete $cv->{_ae_cb})->($cv);
		1759
		1760	$cv->{_ae_cb}
		1761	}
		1762
		1763	sub begin {
		1764	++$_[0]{_ae_counter};
		1765	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
		1766	}
		1767
		1768	sub end {
		1769	return if --$_[0]{_ae_counter};
		1770	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		1771	}
		1772
		1773	# undocumented/compatibility with pre-3.4
		1774	*broadcast = \&send;
		1775	*wait = \&_wait;
		1776
		1777	=head1 ERROR AND EXCEPTION HANDLING
		1778
		1779	In general, AnyEvent does not do any error handling - it relies on the
		1780	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1781	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1782	checking of all AnyEvent methods, however, which is highly useful during
		1783	development.
		1784
		1785	As for exception handling (i.e. runtime errors and exceptions thrown while
		1786	executing a callback), this is not only highly event-loop specific, but
		1787	also not in any way wrapped by this module, as this is the job of the main
		1788	program.
		1789
		1790	The pure perl event loop simply re-throws the exception (usually
		1791	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1792	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1793	so on.
		1794
		1795	=head1 ENVIRONMENT VARIABLES
		1796
		1797	The following environment variables are used by this module or its
		1798	submodules.
		1799
		1800	Note that AnyEvent will remove I<all> environment variables starting with
		1801	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		1802	enabled.
		1803
		1804	=over 4
		1805
		1806	=item C<PERL_ANYEVENT_VERBOSE>
		1807
		1808	By default, AnyEvent will be completely silent except in fatal
		1809	conditions. You can set this environment variable to make AnyEvent more
		1810	talkative.
		1811
		1812	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1813	conditions, such as not being able to load the event model specified by
		1814	C<PERL_ANYEVENT_MODEL>.
		1815
		1816	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1817	model it chooses.
		1818
		1819	When set to C<8> or higher, then AnyEvent will report extra information on
		1820	which optional modules it loads and how it implements certain features.
		1821
		1822	=item C<PERL_ANYEVENT_STRICT>
		1823
		1824	AnyEvent does not do much argument checking by default, as thorough
		1825	argument checking is very costly. Setting this variable to a true value
		1826	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1827	check the arguments passed to most method calls. If it finds any problems,
		1828	it will croak.
		1829
		1830	In other words, enables "strict" mode.
		1831
		1832	Unlike C<use strict> (or it's modern cousin, C<< use L<common::sense>
		1833	>>, it is definitely recommended to keep it off in production. Keeping
		1834	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		1835	can be very useful, however.
		1836
		1837	=item C<PERL_ANYEVENT_MODEL>
		1838
		1839	This can be used to specify the event model to be used by AnyEvent, before
		1840	auto detection and -probing kicks in. It must be a string consisting
		1841	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1842	and the resulting module name is loaded and if the load was successful,
		1843	used as event model. If it fails to load AnyEvent will proceed with
		1844	auto detection and -probing.
		1845
		1846	This functionality might change in future versions.
		1847
		1848	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1849	could start your program like this:
		1850
		1851	PERL_ANYEVENT_MODEL=Perl perl ...
		1852
		1853	=item C<PERL_ANYEVENT_PROTOCOLS>
		1854
		1855	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1856	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1857	of auto probing).
		1858
		1859	Must be set to a comma-separated list of protocols or address families,
		1860	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1861	used, and preference will be given to protocols mentioned earlier in the
		1862	list.
		1863
		1864	This variable can effectively be used for denial-of-service attacks
		1865	against local programs (e.g. when setuid), although the impact is likely
		1866	small, as the program has to handle conenction and other failures anyways.
		1867
		1868	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1869	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1870	- only support IPv4, never try to resolve or contact IPv6
		1871	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1872	IPv6, but prefer IPv6 over IPv4.
		1873
		1874	=item C<PERL_ANYEVENT_EDNS0>
		1875
		1876	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1877	for DNS. This extension is generally useful to reduce DNS traffic, but
		1878	some (broken) firewalls drop such DNS packets, which is why it is off by
		1879	default.
		1880
		1881	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1882	EDNS0 in its DNS requests.
		1883
		1884	=item C<PERL_ANYEVENT_MAX_FORKS>
		1885
		1886	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1887	will create in parallel.
		1888
		1889	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		1890
		1891	The default value for the C<max_outstanding> parameter for the default DNS
		1892	resolver - this is the maximum number of parallel DNS requests that are
		1893	sent to the DNS server.
		1894
		1895	=item C<PERL_ANYEVENT_RESOLV_CONF>
		1896
		1897	The file to use instead of F</etc/resolv.conf> (or OS-specific
		1898	configuration) in the default resolver. When set to the empty string, no
		1899	default config will be used.
		1900
		1901	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		1902
		1903	When neither C<ca_file> nor C<ca_path> was specified during
		1904	L<AnyEvent::TLS> context creation, and either of these environment
		1905	variables exist, they will be used to specify CA certificate locations
		1906	instead of a system-dependent default.
		1907
		1908	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		1909
		1910	When these are set to C<1>, then the respective modules are not
		1911	loaded. Mostly good for testing AnyEvent itself.
		1912
		1913	=back
865		1914
866	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1915	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
867		1916
868	This is an advanced topic that you do not normally need to use AnyEvent in	1917	This is an advanced topic that you do not normally need to use AnyEvent in
869	a module. This section is only of use to event loop authors who want to	1918	a module. This section is only of use to event loop authors who want to
…		…
903		1952
904	I<rxvt-unicode> also cheats a bit by not providing blocking access to	1953	I<rxvt-unicode> also cheats a bit by not providing blocking access to
905	condition variables: code blocking while waiting for a condition will	1954	condition variables: code blocking while waiting for a condition will
906	C<die>. This still works with most modules/usages, and blocking calls must	1955	C<die>. This still works with most modules/usages, and blocking calls must
907	not be done in an interactive application, so it makes sense.	1956	not be done in an interactive application, so it makes sense.
908
909	=head1 ENVIRONMENT VARIABLES
910
911	The following environment variables are used by this module:
912
913	=over 4
914
915	=item C<PERL_ANYEVENT_VERBOSE>
916
917	By default, AnyEvent will be completely silent except in fatal
918	conditions. You can set this environment variable to make AnyEvent more
919	talkative.
920
921	When set to C<1> or higher, causes AnyEvent to warn about unexpected
922	conditions, such as not being able to load the event model specified by
923	C<PERL_ANYEVENT_MODEL>.
924
925	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
926	model it chooses.
927
928	=item C<PERL_ANYEVENT_MODEL>
929
930	This can be used to specify the event model to be used by AnyEvent, before
931	autodetection and -probing kicks in. It must be a string consisting
932	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
933	and the resulting module name is loaded and if the load was successful,
934	used as event model. If it fails to load AnyEvent will proceed with
935	autodetection and -probing.
936
937	This functionality might change in future versions.
938
939	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
940	could start your program like this:
941
942	PERL_ANYEVENT_MODEL=Perl perl ...
943
944	=back
945		1957
946	=head1 EXAMPLE PROGRAM	1958	=head1 EXAMPLE PROGRAM
947		1959
948	The following program uses an I/O watcher to read data from STDIN, a timer	1960	The following program uses an I/O watcher to read data from STDIN, a timer
949	to display a message once per second, and a condition variable to quit the	1961	to display a message once per second, and a condition variable to quit the
…		…
958	poll => 'r',	1970	poll => 'r',
959	cb => sub {	1971	cb => sub {
960	warn "io event <$_[0]>\n"; # will always output <r>	1972	warn "io event <$_[0]>\n"; # will always output <r>
961	chomp (my $input = <STDIN>); # read a line	1973	chomp (my $input = <STDIN>); # read a line
962	warn "read: $input\n"; # output what has been read	1974	warn "read: $input\n"; # output what has been read
963	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	1975	$cv->send if $input =~ /^q/i; # quit program if /^q/i
964	},	1976	},
965	);	1977	);
966		1978
967	my $time_watcher; # can only be used once
968
969	sub new_timer {
970	$timer = AnyEvent->timer (after => 1, cb => sub {	1979	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
971	warn "timeout\n"; # print 'timeout' about every second	1980	warn "timeout\n"; # print 'timeout' at most every second
972	&new_timer; # and restart the time
973	});	1981	});
974	}
975		1982
976	new_timer; # create first timer
977
978	$cv->wait; # wait until user enters /^q/i	1983	$cv->recv; # wait until user enters /^q/i
979		1984
980	=head1 REAL-WORLD EXAMPLE	1985	=head1 REAL-WORLD EXAMPLE
981		1986
982	Consider the L<Net::FCP> module. It features (among others) the following	1987	Consider the L<Net::FCP> module. It features (among others) the following
983	API calls, which are to freenet what HTTP GET requests are to http:	1988	API calls, which are to freenet what HTTP GET requests are to http:
…		…
1033	syswrite $txn->{fh}, $txn->{request}	2038	syswrite $txn->{fh}, $txn->{request}
1034	or die "connection or write error";	2039	or die "connection or write error";
1035	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	2040	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
1036		2041
1037	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	2042	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
1038	result and signals any possible waiters that the request ahs finished:	2043	result and signals any possible waiters that the request has finished:
1039		2044
1040	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	2045	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
1041		2046
1042	if (end-of-file or data complete) {	2047	if (end-of-file or data complete) {
1043	$txn->{result} = $txn->{buf};	2048	$txn->{result} = $txn->{buf};
1044	$txn->{finished}->broadcast;	2049	$txn->{finished}->send;
1045	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	2050	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
1046	}	2051	}
1047		2052
1048	The C<result> method, finally, just waits for the finished signal (if the	2053	The C<result> method, finally, just waits for the finished signal (if the
1049	request was already finished, it doesn't wait, of course, and returns the	2054	request was already finished, it doesn't wait, of course, and returns the
1050	data:	2055	data:
1051		2056
1052	$txn->{finished}->wait;	2057	$txn->{finished}->recv;
1053	return $txn->{result};	2058	return $txn->{result};
1054		2059
1055	The actual code goes further and collects all errors (C<die>s, exceptions)	2060	The actual code goes further and collects all errors (C<die>s, exceptions)
1056	that occured during request processing. The C<result> method detects	2061	that occurred during request processing. The C<result> method detects
1057	whether an exception as thrown (it is stored inside the $txn object)	2062	whether an exception as thrown (it is stored inside the $txn object)
1058	and just throws the exception, which means connection errors and other	2063	and just throws the exception, which means connection errors and other
1059	problems get reported tot he code that tries to use the result, not in a	2064	problems get reported tot he code that tries to use the result, not in a
1060	random callback.	2065	random callback.
1061		2066
…		…
1092		2097
1093	my $quit = AnyEvent->condvar;	2098	my $quit = AnyEvent->condvar;
1094		2099
1095	$fcp->txn_client_get ($url)->cb (sub {	2100	$fcp->txn_client_get ($url)->cb (sub {
1096	...	2101	...
1097	$quit->broadcast;	2102	$quit->send;
1098	});	2103	});
1099		2104
1100	$quit->wait;	2105	$quit->recv;
1101		2106
1102		2107
1103	=head1 BENCHMARKS	2108	=head1 BENCHMARKS
1104		2109
1105	To give you an idea of the performance and overheads that AnyEvent adds	2110	To give you an idea of the performance and overheads that AnyEvent adds
…		…
1107	of various event loops I prepared some benchmarks.	2112	of various event loops I prepared some benchmarks.
1108		2113
1109	=head2 BENCHMARKING ANYEVENT OVERHEAD	2114	=head2 BENCHMARKING ANYEVENT OVERHEAD
1110		2115
1111	Here is a benchmark of various supported event models used natively and	2116	Here is a benchmark of various supported event models used natively and
1112	through anyevent. The benchmark creates a lot of timers (with a zero	2117	through AnyEvent. The benchmark creates a lot of timers (with a zero
1113	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,	2118	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
1114	which it is), lets them fire exactly once and destroys them again.	2119	which it is), lets them fire exactly once and destroys them again.
1115		2120
1116	Source code for this benchmark is found as F<eg/bench> in the AnyEvent	2121	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
1117	distribution.	2122	distribution. It uses the L<AE> interface, which makes a real difference
		2123	for the EV and Perl backends only.
1118		2124
1119	=head3 Explanation of the columns	2125	=head3 Explanation of the columns
1120		2126
1121	I<watcher> is the number of event watchers created/destroyed. Since	2127	I<watcher> is the number of event watchers created/destroyed. Since
1122	different event models feature vastly different performances, each event	2128	different event models feature vastly different performances, each event
…		…
1134	all watchers, to avoid adding memory overhead. That means closure creation	2140	all watchers, to avoid adding memory overhead. That means closure creation
1135	and memory usage is not included in the figures.	2141	and memory usage is not included in the figures.
1136		2142
1137	I<invoke> is the time, in microseconds, used to invoke a simple	2143	I<invoke> is the time, in microseconds, used to invoke a simple
1138	callback. The callback simply counts down a Perl variable and after it was	2144	callback. The callback simply counts down a Perl variable and after it was
1139	invoked "watcher" times, it would C<< ->broadcast >> a condvar once to	2145	invoked "watcher" times, it would C<< ->send >> a condvar once to
1140	signal the end of this phase.	2146	signal the end of this phase.
1141		2147
1142	I<destroy> is the time, in microseconds, that it takes to destroy a single	2148	I<destroy> is the time, in microseconds, that it takes to destroy a single
1143	watcher.	2149	watcher.
1144		2150
1145	=head3 Results	2151	=head3 Results
1146		2152
1147	name watchers bytes create invoke destroy comment	2153	name watchers bytes create invoke destroy comment
1148	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	2154	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
1149	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	2155	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
1150	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	2156	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
1151	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	2157	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
1152	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	2158	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
1153	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers	2159	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
		2160	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
		2161	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
1154	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	2162	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
1155	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	2163	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
1156	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	2164	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
1157	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	2165	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
1158		2166
1159	=head3 Discussion	2167	=head3 Discussion
1160		2168
1161	The benchmark does I<not> measure scalability of the event loop very	2169	The benchmark does I<not> measure scalability of the event loop very
1162	well. For example, a select-based event loop (such as the pure perl one)	2170	well. For example, a select-based event loop (such as the pure perl one)
…		…
1174	benchmark machine, handling an event takes roughly 1600 CPU cycles with	2182	benchmark machine, handling an event takes roughly 1600 CPU cycles with
1175	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU	2183	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
1176	cycles with POE.	2184	cycles with POE.
1177		2185
1178	C<EV> is the sole leader regarding speed and memory use, which are both	2186	C<EV> is the sole leader regarding speed and memory use, which are both
1179	maximal/minimal, respectively. Even when going through AnyEvent, it uses	2187	maximal/minimal, respectively. When using the L<AE> API there is zero
		2188	overhead (when going through the AnyEvent API create is about 5-6 times
		2189	slower, with other times being equal, so still uses far less memory than
1180	far less memory than any other event loop and is still faster than Event	2190	any other event loop and is still faster than Event natively).
1181	natively.
1182		2191
1183	The pure perl implementation is hit in a few sweet spots (both the	2192	The pure perl implementation is hit in a few sweet spots (both the
1184	constant timeout and the use of a single fd hit optimisations in the perl	2193	constant timeout and the use of a single fd hit optimisations in the perl
1185	interpreter and the backend itself). Nevertheless this shows that it	2194	interpreter and the backend itself). Nevertheless this shows that it
1186	adds very little overhead in itself. Like any select-based backend its	2195	adds very little overhead in itself. Like any select-based backend its
1187	performance becomes really bad with lots of file descriptors (and few of	2196	performance becomes really bad with lots of file descriptors (and few of
1188	them active), of course, but this was not subject of this benchmark.	2197	them active), of course, but this was not subject of this benchmark.
1189		2198
1190	The C<Event> module has a relatively high setup and callback invocation	2199	The C<Event> module has a relatively high setup and callback invocation
1191	cost, but overall scores in on the third place.	2200	cost, but overall scores in on the third place.
		2201
		2202	C<IO::Async> performs admirably well, about on par with C<Event>, even
		2203	when using its pure perl backend.
1192		2204
1193	C<Glib>'s memory usage is quite a bit higher, but it features a	2205	C<Glib>'s memory usage is quite a bit higher, but it features a
1194	faster callback invocation and overall ends up in the same class as	2206	faster callback invocation and overall ends up in the same class as
1195	C<Event>. However, Glib scales extremely badly, doubling the number of	2207	C<Event>. However, Glib scales extremely badly, doubling the number of
1196	watchers increases the processing time by more than a factor of four,	2208	watchers increases the processing time by more than a factor of four,
…		…
1240		2252
1241	=back	2253	=back
1242		2254
1243	=head2 BENCHMARKING THE LARGE SERVER CASE	2255	=head2 BENCHMARKING THE LARGE SERVER CASE
1244		2256
1245	This benchmark atcually benchmarks the event loop itself. It works by	2257	This benchmark actually benchmarks the event loop itself. It works by
1246	creating a number of "servers": each server consists of a socketpair, a	2258	creating a number of "servers": each server consists of a socket pair, a
1247	timeout watcher that gets reset on activity (but never fires), and an I/O	2259	timeout watcher that gets reset on activity (but never fires), and an I/O
1248	watcher waiting for input on one side of the socket. Each time the socket	2260	watcher waiting for input on one side of the socket. Each time the socket
1249	watcher reads a byte it will write that byte to a random other "server".	2261	watcher reads a byte it will write that byte to a random other "server".
1250		2262
1251	The effect is that there will be a lot of I/O watchers, only part of which	2263	The effect is that there will be a lot of I/O watchers, only part of which
1252	are active at any one point (so there is a constant number of active	2264	are active at any one point (so there is a constant number of active
1253	fds for each loop iterstaion, but which fds these are is random). The	2265	fds for each loop iteration, but which fds these are is random). The
1254	timeout is reset each time something is read because that reflects how	2266	timeout is reset each time something is read because that reflects how
1255	most timeouts work (and puts extra pressure on the event loops).	2267	most timeouts work (and puts extra pressure on the event loops).
1256		2268
1257	In this benchmark, we use 10000 socketpairs (20000 sockets), of which 100	2269	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
1258	(1%) are active. This mirrors the activity of large servers with many	2270	(1%) are active. This mirrors the activity of large servers with many
1259	connections, most of which are idle at any one point in time.	2271	connections, most of which are idle at any one point in time.
1260		2272
1261	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent	2273	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
1262	distribution.	2274	distribution. It uses the L<AE> interface, which makes a real difference
		2275	for the EV and Perl backends only.
1263		2276
1264	=head3 Explanation of the columns	2277	=head3 Explanation of the columns
1265		2278
1266	I<sockets> is the number of sockets, and twice the number of "servers" (as	2279	I<sockets> is the number of sockets, and twice the number of "servers" (as
1267	each server has a read and write socket end).	2280	each server has a read and write socket end).
1268		2281
1269	I<create> is the time it takes to create a socketpair (which is	2282	I<create> is the time it takes to create a socket pair (which is
1270	nontrivial) and two watchers: an I/O watcher and a timeout watcher.	2283	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
1271		2284
1272	I<request>, the most important value, is the time it takes to handle a	2285	I<request>, the most important value, is the time it takes to handle a
1273	single "request", that is, reading the token from the pipe and forwarding	2286	single "request", that is, reading the token from the pipe and forwarding
1274	it to another server. This includes deleting the old timeout and creating	2287	it to another server. This includes deleting the old timeout and creating
1275	a new one that moves the timeout into the future.	2288	a new one that moves the timeout into the future.
1276		2289
1277	=head3 Results	2290	=head3 Results
1278		2291
1279	name sockets create request	2292	name sockets create request
1280	EV 20000 69.01 11.16	2293	EV 20000 62.66 7.99
1281	Perl 20000 73.32 35.87	2294	Perl 20000 68.32 32.64
1282	Event 20000 212.62 257.32	2295	IOAsync 20000 174.06 101.15 epoll
1283	Glib 20000 651.16 1896.30	2296	IOAsync 20000 174.67 610.84 poll
		2297	Event 20000 202.69 242.91
		2298	Glib 20000 557.01 1689.52
1284	POE 20000 349.67 12317.24 uses POE::Loop::Event	2299	POE 20000 341.54 12086.32 uses POE::Loop::Event
1285		2300
1286	=head3 Discussion	2301	=head3 Discussion
1287		2302
1288	This benchmark I<does> measure scalability and overall performance of the	2303	This benchmark I<does> measure scalability and overall performance of the
1289	particular event loop.	2304	particular event loop.
…		…
1291	EV is again fastest. Since it is using epoll on my system, the setup time	2306	EV is again fastest. Since it is using epoll on my system, the setup time
1292	is relatively high, though.	2307	is relatively high, though.
1293		2308
1294	Perl surprisingly comes second. It is much faster than the C-based event	2309	Perl surprisingly comes second. It is much faster than the C-based event
1295	loops Event and Glib.	2310	loops Event and Glib.
		2311
		2312	IO::Async performs very well when using its epoll backend, and still quite
		2313	good compared to Glib when using its pure perl backend.
1296		2314
1297	Event suffers from high setup time as well (look at its code and you will	2315	Event suffers from high setup time as well (look at its code and you will
1298	understand why). Callback invocation also has a high overhead compared to	2316	understand why). Callback invocation also has a high overhead compared to
1299	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event	2317	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
1300	uses select or poll in basically all documented configurations.	2318	uses select or poll in basically all documented configurations.
…		…
1347	speed most when you have lots of watchers, not when you only have a few of	2365	speed most when you have lots of watchers, not when you only have a few of
1348	them).	2366	them).
1349		2367
1350	EV is again fastest.	2368	EV is again fastest.
1351		2369
1352	Perl again comes second. It is noticably faster than the C-based event	2370	Perl again comes second. It is noticeably faster than the C-based event
1353	loops Event and Glib, although the difference is too small to really	2371	loops Event and Glib, although the difference is too small to really
1354	matter.	2372	matter.
1355		2373
1356	POE also performs much better in this case, but is is still far behind the	2374	POE also performs much better in this case, but is is still far behind the
1357	others.	2375	others.
…		…
1363	=item * C-based event loops perform very well with small number of	2381	=item * C-based event loops perform very well with small number of
1364	watchers, as the management overhead dominates.	2382	watchers, as the management overhead dominates.
1365		2383
1366	=back	2384	=back
1367		2385
		2386	=head2 THE IO::Lambda BENCHMARK
		2387
		2388	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2389	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2390	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2391	shouldn't come as a surprise to anybody). As such, the benchmark is
		2392	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2393	very optimal. But how would AnyEvent compare when used without the extra
		2394	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2395
		2396	The benchmark itself creates an echo-server, and then, for 500 times,
		2397	connects to the echo server, sends a line, waits for the reply, and then
		2398	creates the next connection. This is a rather bad benchmark, as it doesn't
		2399	test the efficiency of the framework or much non-blocking I/O, but it is a
		2400	benchmark nevertheless.
		2401
		2402	name runtime
		2403	Lambda/select 0.330 sec
		2404	+ optimized 0.122 sec
		2405	Lambda/AnyEvent 0.327 sec
		2406	+ optimized 0.138 sec
		2407	Raw sockets/select 0.077 sec
		2408	POE/select, components 0.662 sec
		2409	POE/select, raw sockets 0.226 sec
		2410	POE/select, optimized 0.404 sec
		2411
		2412	AnyEvent/select/nb 0.085 sec
		2413	AnyEvent/EV/nb 0.068 sec
		2414	+state machine 0.134 sec
		2415
		2416	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2417	benchmarks actually make blocking connects and use 100% blocking I/O,
		2418	defeating the purpose of an event-based solution. All of the newly
		2419	written AnyEvent benchmarks use 100% non-blocking connects (using
		2420	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2421	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2422	generally require a lot more bookkeeping and event handling than blocking
		2423	connects (which involve a single syscall only).
		2424
		2425	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2426	offers similar expressive power as POE and IO::Lambda, using conventional
		2427	Perl syntax. This means that both the echo server and the client are 100%
		2428	non-blocking, further placing it at a disadvantage.
		2429
		2430	As you can see, the AnyEvent + EV combination even beats the
		2431	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2432	backend easily beats IO::Lambda and POE.
		2433
		2434	And even the 100% non-blocking version written using the high-level (and
		2435	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda
		2436	higher level ("unoptimised") abstractions by a large margin, even though
		2437	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
		2438
		2439	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2440	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2441	part of the IO::Lambda distribution and were used without any changes.
		2442
		2443
		2444	=head1 SIGNALS
		2445
		2446	AnyEvent currently installs handlers for these signals:
		2447
		2448	=over 4
		2449
		2450	=item SIGCHLD
		2451
		2452	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2453	emulation for event loops that do not support them natively. Also, some
		2454	event loops install a similar handler.
		2455
		2456	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2457	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2458
		2459	=item SIGPIPE
		2460
		2461	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2462	when AnyEvent gets loaded.
		2463
		2464	The rationale for this is that AnyEvent users usually do not really depend
		2465	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2466	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2467	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2468	some random socket.
		2469
		2470	The rationale for installing a no-op handler as opposed to ignoring it is
		2471	that this way, the handler will be restored to defaults on exec.
		2472
		2473	Feel free to install your own handler, or reset it to defaults.
		2474
		2475	=back
		2476
		2477	=cut
		2478
		2479	undef $SIG{CHLD}
		2480	if $SIG{CHLD} eq 'IGNORE';
		2481
		2482	$SIG{PIPE} = sub { }
		2483	unless defined $SIG{PIPE};
		2484
		2485	=head1 RECOMMENDED/OPTIONAL MODULES
		2486
		2487	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2488	it's built-in modules) are required to use it.
		2489
		2490	That does not mean that AnyEvent won't take advantage of some additional
		2491	modules if they are installed.
		2492
		2493	This section explains which additional modules will be used, and how they
		2494	affect AnyEvent's operation.
		2495
		2496	=over 4
		2497
		2498	=item L<Async::Interrupt>
		2499
		2500	This slightly arcane module is used to implement fast signal handling: To
		2501	my knowledge, there is no way to do completely race-free and quick
		2502	signal handling in pure perl. To ensure that signals still get
		2503	delivered, AnyEvent will start an interval timer to wake up perl (and
		2504	catch the signals) with some delay (default is 10 seconds, look for
		2505	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2506
		2507	If this module is available, then it will be used to implement signal
		2508	catching, which means that signals will not be delayed, and the event loop
		2509	will not be interrupted regularly, which is more efficient (and good for
		2510	battery life on laptops).
		2511
		2512	This affects not just the pure-perl event loop, but also other event loops
		2513	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2514
		2515	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2516	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2517	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2518	does nothing for those backends.
		2519
		2520	=item L<EV>
		2521
		2522	This module isn't really "optional", as it is simply one of the backend
		2523	event loops that AnyEvent can use. However, it is simply the best event
		2524	loop available in terms of features, speed and stability: It supports
		2525	the AnyEvent API optimally, implements all the watcher types in XS, does
		2526	automatic timer adjustments even when no monotonic clock is available,
		2527	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2528	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2529	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2530
		2531	=item L<Guard>
		2532
		2533	The guard module, when used, will be used to implement
		2534	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2535	lot less memory), but otherwise doesn't affect guard operation much. It is
		2536	purely used for performance.
		2537
		2538	=item L<JSON> and L<JSON::XS>
		2539
		2540	One of these modules is required when you want to read or write JSON data
		2541	via L<AnyEvent::Handle>. It is also written in pure-perl, but can take
		2542	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2543
		2544	In fact, L<AnyEvent::Handle> will use L<JSON::XS> by default if it is
		2545	installed.
		2546
		2547	=item L<Net::SSLeay>
		2548
		2549	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2550	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2551	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2552
		2553	=item L<Time::HiRes>
		2554
		2555	This module is part of perl since release 5.008. It will be used when the
		2556	chosen event library does not come with a timing source on it's own. The
		2557	pure-perl event loop (L<AnyEvent::Impl::Perl>) will additionally use it to
		2558	try to use a monotonic clock for timing stability.
		2559
		2560	=back
		2561
1368		2562
1369	=head1 FORK	2563	=head1 FORK
1370		2564
1371	Most event libraries are not fork-safe. The ones who are usually are	2565	Most event libraries are not fork-safe. The ones who are usually are
1372	because they rely on inefficient but fork-safe C<select> or C<poll>	2566	because they rely on inefficient but fork-safe C<select> or C<poll> calls
1373	calls. Only L<EV> is fully fork-aware.	2567	- higher performance APIs such as BSD's kqueue or the dreaded Linux epoll
		2568	are usually badly thought-out hacks that are incompatible with fork in
		2569	one way or another. Only L<EV> is fully fork-aware and ensures that you
		2570	continue event-processing in both parent and child (or both, if you know
		2571	what you are doing).
		2572
		2573	This means that, in general, you cannot fork and do event processing in
		2574	the child if the event library was initialised before the fork (which
		2575	usually happens when the first AnyEvent watcher is created, or the library
		2576	is loaded).
1374		2577
1375	If you have to fork, you must either do so I<before> creating your first	2578	If you have to fork, you must either do so I<before> creating your first
1376	watcher OR you must not use AnyEvent at all in the child.	2579	watcher OR you must not use AnyEvent at all in the child OR you must do
		2580	something completely out of the scope of AnyEvent.
		2581
		2582	The problem of doing event processing in the parent I<and> the child
		2583	is much more complicated: even for backends that I<are> fork-aware or
		2584	fork-safe, their behaviour is not usually what you want: fork clones all
		2585	watchers, that means all timers, I/O watchers etc. are active in both
		2586	parent and child, which is almost never what you want. USing C<exec>
		2587	to start worker children from some kind of manage rprocess is usually
		2588	preferred, because it is much easier and cleaner, at the expense of having
		2589	to have another binary.
1377		2590
1378		2591
1379	=head1 SECURITY CONSIDERATIONS	2592	=head1 SECURITY CONSIDERATIONS
1380		2593
1381	AnyEvent can be forced to load any event model via	2594	AnyEvent can be forced to load any event model via
…		…
1386	specified in the variable.	2599	specified in the variable.
1387		2600
1388	You can make AnyEvent completely ignore this variable by deleting it	2601	You can make AnyEvent completely ignore this variable by deleting it
1389	before the first watcher gets created, e.g. with a C<BEGIN> block:	2602	before the first watcher gets created, e.g. with a C<BEGIN> block:
1390		2603
1391	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	2604	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1392		2605
1393	use AnyEvent;	2606	use AnyEvent;
1394		2607
1395	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can	2608	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1396	be used to probe what backend is used and gain other information (which is	2609	be used to probe what backend is used and gain other information (which is
1397	probably even less useful to an attacker than PERL_ANYEVENT_MODEL).	2610	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2611	$ENV{PERL_ANYEVENT_STRICT}.
		2612
		2613	Note that AnyEvent will remove I<all> environment variables starting with
		2614	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2615	enabled.
		2616
		2617
		2618	=head1 BUGS
		2619
		2620	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2621	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2622	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2623	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2624	pronounced).
1398		2625
1399		2626
1400	=head1 SEE ALSO	2627	=head1 SEE ALSO
1401		2628
1402	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	2629	Utility functions: L<AnyEvent::Util>.
1403	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,	2630
		2631	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
1404	L<Event::Lib>, L<Qt>, L<POE>.	2632	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
1405		2633
1406	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	2634	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
		2635	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
		2636	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1407	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,	2637	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>, L<Anyevent::Impl::Irssi>.
1408	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,
1409	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.
1410		2638
		2639	Non-blocking file handles, sockets, TCP clients and
		2640	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
		2641
		2642	Asynchronous DNS: L<AnyEvent::DNS>.
		2643
		2644	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>,
		2645	L<Coro::Event>,
		2646
1411	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	2647	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::XMPP>,
		2648	L<AnyEvent::HTTP>.
1412		2649
1413		2650
1414	=head1 AUTHOR	2651	=head1 AUTHOR
1415		2652
1416	Marc Lehmann <schmorp@schmorp.de>	2653	Marc Lehmann <schmorp@schmorp.de>
1417	http://home.schmorp.de/	2654	http://home.schmorp.de/
1418		2655
1419	=cut	2656	=cut
1420		2657
1421	1	2658	1
1422		2659

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