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Revision 1.55 by root, Wed Apr 23 11:25:42 2008 UTC vs.
Revision 1.381 by root, Thu Sep 1 22:09:25 2011 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 - various supported event loops	5	EV, Event, Glib, Tk, Perl, Event::Lib, Irssi, rxvt-unicode, IO::Async, Qt,
		6	FLTK and POE are various supported event loops/environments.
6		7
7	=head1 SYNOPSIS	8	=head1 SYNOPSIS
8		9
9	use AnyEvent;	10	use AnyEvent;
10		11
		12	# if you prefer function calls, look at the AE manpage for
		13	# an alternative API.
		14
		15	# file handle or descriptor readable
11	my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub {	16	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
		17
		18	# one-shot or repeating timers
		19	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
		20	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...);
		21
		22	print AnyEvent->now; # prints current event loop time
		23	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
		24
		25	# POSIX signal
		26	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
		27
		28	# child process exit
		29	my $w = AnyEvent->child (pid => $pid, cb => sub {
		30	my ($pid, $status) = @_;
12	...	31	...
13	});	32	});
14		33
15	my $w = AnyEvent->timer (after => $seconds, cb => sub {	34	# called when event loop idle (if applicable)
16	...	35	my $w = AnyEvent->idle (cb => sub { ... });
17	});
18		36
19	my $w = AnyEvent->condvar; # stores whether a condition was flagged	37	my $w = AnyEvent->condvar; # stores whether a condition was flagged
		38	$w->send; # wake up current and all future recv's
20	$w->wait; # enters "main loop" till $condvar gets ->broadcast	39	$w->recv; # enters "main loop" till $condvar gets ->send
21	$w->broadcast; # wake up current and all future wait's	40	# use a condvar in callback mode:
		41	$w->cb (sub { $_[0]->recv });
		42
		43	=head1 INTRODUCTION/TUTORIAL
		44
		45	This manpage is mainly a reference manual. If you are interested
		46	in a tutorial or some gentle introduction, have a look at the
		47	L<AnyEvent::Intro> manpage.
		48
		49	=head1 SUPPORT
		50
		51	An FAQ document is available as L<AnyEvent::FAQ>.
		52
		53	There also is a mailinglist for discussing all things AnyEvent, and an IRC
		54	channel, too.
		55
		56	See the AnyEvent project page at the B<Schmorpforge Ta-Sa Software
		57	Repository>, at L<http://anyevent.schmorp.de>, for more info.
22		58
23	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)	59	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
24		60
25	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	61	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
26	nowadays. So what is different about AnyEvent?	62	nowadays. So what is different about AnyEvent?
27		63
28	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of	64	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
29	policy> and AnyEvent is I<small and efficient>.	65	policy> and AnyEvent is I<small and efficient>.
30		66
31	First and foremost, I<AnyEvent is not an event model> itself, it only	67	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	68	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,	69	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,	70	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	71	only one event loop can be active at the same time in a process. AnyEvent
36	helps hiding the differences between those event loops.	72	cannot change this, but it can hide the differences between those event
		73	loops.
37		74
38	The goal of AnyEvent is to offer module authors the ability to do event	75	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	76	programming (waiting for I/O or timer events) without subscribing to a
40	religion, a way of living, and most importantly: without forcing your	77	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	78	module users into the same thing by forcing them to use the same event
42	model you use.	79	model you use.
43		80
44	For modules like POE or IO::Async (which is a total misnomer as it is	81	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	82	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	83	like joining a cult: After you join, you are dependent on them and you
47	cannot use anything else, as it is simply incompatible to everything that	84	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	85	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.	86	module are I<also> forced to use the same event loop you use.
50		87
51	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	88	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
52	fine. AnyEvent + Tk works fine etc. etc. but none of these work together	89	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	90	with the rest: POE + EV? No go. Tk + Event? No go. Again: if your module
54	your module uses one of those, every user of your module has to use it,	91	uses one of those, every user of your module has to use it, too. But if
55	too. But if your module uses AnyEvent, it works transparently with all	92	your module uses AnyEvent, it works transparently with all event models it
56	event models it supports (including stuff like POE and IO::Async, as long	93	supports (including stuff like IO::Async, as long as those use one of the
57	as those use one of the supported event loops. It is trivial to add new	94	supported event loops. It is easy to add new event loops to AnyEvent, too,
58	event loops to AnyEvent, too, so it is future-proof).	95	so it is future-proof).
59		96
60	In addition to being free of having to use I<the one and only true event	97	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	98	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	99	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	100	follow. AnyEvent, on the other hand, is lean and to the point, by only
64	offering the functionality that is necessary, in as thin as a wrapper as	101	offering the functionality that is necessary, in as thin as a wrapper as
65	technically possible.	102	technically possible.
66		103
		104	Of course, AnyEvent comes with a big (and fully optional!) toolbox
		105	of useful functionality, such as an asynchronous DNS resolver, 100%
		106	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
		107	such as Windows) and lots of real-world knowledge and workarounds for
		108	platform bugs and differences.
		109
67	Of course, if you want lots of policy (this can arguably be somewhat	110	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	111	useful) and you want to force your users to use the one and only event
69	model, you should I<not> use this module.	112	model, you should I<not> use this module.
70		113
71
72	=head1 DESCRIPTION	114	=head1 DESCRIPTION
73		115
74	L<AnyEvent> provides an identical interface to multiple event loops. This	116	L<AnyEvent> provides a uniform interface to various event loops. This
75	allows module authors to utilise an event loop without forcing module	117	allows module authors to use event loop functionality without forcing
76	users to use the same event loop (as only a single event loop can coexist	118	module users to use a specific event loop implementation (since more
77	peacefully at any one time).	119	than one event loop cannot coexist peacefully).
78		120
79	The interface itself is vaguely similar, but not identical to the L<Event>	121	The interface itself is vaguely similar, but not identical to the L<Event>
80	module.	122	module.
81		123
82	During the first call of any watcher-creation method, the module tries	124	During the first call of any watcher-creation method, the module tries
83	to detect the currently loaded event loop by probing whether one of the	125	to detect the currently loaded event loop by probing whether one of the
84	following modules is already loaded: L<Coro::EV>, L<Coro::Event>, L<EV>,	126	following modules is already loaded: L<EV>, L<AnyEvent::Loop>,
85	L<Event>, L<Glib>, L<Tk>. The first one found is used. If none are found,	127	L<Event>, L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>. The first one
86	the module tries to load these modules in the stated order. The first one	128	found is used. If none are detected, the module tries to load the first
87	that can be successfully loaded will be used. If, after this, still none	129	four modules in the order given; but note that if L<EV> is not
88	could be found, AnyEvent will fall back to a pure-perl event loop, which	130	available, the pure-perl L<AnyEvent::Loop> should always work, so
89	is not very efficient, but should work everywhere.	131	the other two are not normally tried.
90		132
91	Because AnyEvent first checks for modules that are already loaded, loading	133	Because AnyEvent first checks for modules that are already loaded, loading
92	an event model explicitly before first using AnyEvent will likely make	134	an event model explicitly before first using AnyEvent will likely make
93	that model the default. For example:	135	that model the default. For example:
94		136
…		…
96	use AnyEvent;	138	use AnyEvent;
97		139
98	# .. AnyEvent will likely default to Tk	140	# .. AnyEvent will likely default to Tk
99		141
100	The I<likely> means that, if any module loads another event model and	142	The I<likely> means that, if any module loads another event model and
101	starts using it, all bets are off. Maybe you should tell their authors to	143	starts using it, all bets are off - this case should be very rare though,
102	use AnyEvent so their modules work together with others seamlessly...	144	as very few modules hardcode event loops without announcing this very
		145	loudly.
103		146
104	The pure-perl implementation of AnyEvent is called	147	The pure-perl implementation of AnyEvent is called C<AnyEvent::Loop>. Like
105	C<AnyEvent::Impl::Perl>. Like other event modules you can load it	148	other event modules you can load it explicitly and enjoy the high
106	explicitly.	149	availability of that event loop :)
107		150
108	=head1 WATCHERS	151	=head1 WATCHERS
109		152
110	AnyEvent has the central concept of a I<watcher>, which is an object that	153	AnyEvent has the central concept of a I<watcher>, which is an object that
111	stores relevant data for each kind of event you are waiting for, such as	154	stores relevant data for each kind of event you are waiting for, such as
112	the callback to call, the filehandle to watch, etc.	155	the callback to call, the file handle to watch, etc.
113		156
114	These watchers are normal Perl objects with normal Perl lifetime. After	157	These watchers are normal Perl objects with normal Perl lifetime. After
115	creating a watcher it will immediately "watch" for events and invoke the	158	creating a watcher it will immediately "watch" for events and invoke the
116	callback when the event occurs (of course, only when the event model	159	callback when the event occurs (of course, only when the event model
117	is in control).	160	is in control).
118		161
		162	Note that B<callbacks must not permanently change global variables>
		163	potentially in use by the event loop (such as C<$_> or C<$[>) and that B<<
		164	callbacks must not C<die> >>. The former is good programming practice in
		165	Perl and the latter stems from the fact that exception handling differs
		166	widely between event loops.
		167
119	To disable the watcher you have to destroy it (e.g. by setting the	168	To disable a watcher you have to destroy it (e.g. by setting the
120	variable you store it in to C<undef> or otherwise deleting all references	169	variable you store it in to C<undef> or otherwise deleting all references
121	to it).	170	to it).
122		171
123	All watchers are created by calling a method on the C<AnyEvent> class.	172	All watchers are created by calling a method on the C<AnyEvent> class.
124		173
125	Many watchers either are used with "recursion" (repeating timers for	174	Many watchers either are used with "recursion" (repeating timers for
126	example), or need to refer to their watcher object in other ways.	175	example), or need to refer to their watcher object in other ways.
127		176
128	An any way to achieve that is this pattern:	177	One way to achieve that is this pattern:
129		178
130	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	179	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
131	# you can use $w here, for example to undef it	180	# you can use $w here, for example to undef it
132	undef $w;	181	undef $w;
133	});	182	});
134		183
135	Note that C<my $w; $w => combination. This is necessary because in Perl,	184	Note that C<my $w; $w => combination. This is necessary because in Perl,
136	my variables are only visible after the statement in which they are	185	my variables are only visible after the statement in which they are
137	declared.	186	declared.
138		187
139	=head2 IO WATCHERS	188	=head2 I/O WATCHERS
		189
		190	$w = AnyEvent->io (
		191	fh => <filehandle_or_fileno>,
		192	poll => <"r" or "w">,
		193	cb => <callback>,
		194	);
140		195
141	You can create an I/O watcher by calling the C<< AnyEvent->io >> method	196	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
142	with the following mandatory key-value pairs as arguments:	197	with the following mandatory key-value pairs as arguments:
143		198
144	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch for	199	C<fh> is the Perl I<file handle> (or a naked file descriptor) to watch
		200	for events (AnyEvent might or might not keep a reference to this file
		201	handle). Note that only file handles pointing to things for which
		202	non-blocking operation makes sense are allowed. This includes sockets,
		203	most character devices, pipes, fifos and so on, but not for example files
		204	or block devices.
		205
145	events. C<poll> must be a string that is either C<r> or C<w>, which	206	C<poll> must be a string that is either C<r> or C<w>, which creates a
146	creates a watcher waiting for "r"eadable or "w"ritable events,	207	watcher waiting for "r"eadable or "w"ritable events, respectively.
		208
147	respectively. C<cb> is the callback to invoke each time the file handle	209	C<cb> is the callback to invoke each time the file handle becomes ready.
148	becomes ready.
149		210
150	File handles will be kept alive, so as long as the watcher exists, the	211	Although the callback might get passed parameters, their value and
151	file handle exists, too.	212	presence is undefined and you cannot rely on them. Portable AnyEvent
		213	callbacks cannot use arguments passed to I/O watcher callbacks.
152		214
		215	The I/O watcher might use the underlying file descriptor or a copy of it.
153	It is not allowed to close a file handle as long as any watcher is active	216	You must not close a file handle as long as any watcher is active on the
154	on the underlying file descriptor.	217	underlying file descriptor.
155		218
156	Some event loops issue spurious readyness notifications, so you should	219	Some event loops issue spurious readiness notifications, so you should
157	always use non-blocking calls when reading/writing from/to your file	220	always use non-blocking calls when reading/writing from/to your file
158	handles.	221	handles.
159		222
160	Example:
161
162	# wait for readability of STDIN, then read a line and disable the watcher	223	Example: wait for readability of STDIN, then read a line and disable the
		224	watcher.
		225
163	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	226	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
164	chomp (my $input = <STDIN>);	227	chomp (my $input = <STDIN>);
165	warn "read: $input\n";	228	warn "read: $input\n";
166	undef $w;	229	undef $w;
167	});	230	});
168		231
169	=head2 TIME WATCHERS	232	=head2 TIME WATCHERS
170		233
		234	$w = AnyEvent->timer (after => <seconds>, cb => <callback>);
		235
		236	$w = AnyEvent->timer (
		237	after => <fractional_seconds>,
		238	interval => <fractional_seconds>,
		239	cb => <callback>,
		240	);
		241
171	You can create a time watcher by calling the C<< AnyEvent->timer >>	242	You can create a time watcher by calling the C<< AnyEvent->timer >>
172	method with the following mandatory arguments:	243	method with the following mandatory arguments:
173		244
174	C<after> specifies after how many seconds (fractional values are	245	C<after> specifies after how many seconds (fractional values are
175	supported) should the timer activate. C<cb> the callback to invoke in that	246	supported) the callback should be invoked. C<cb> is the callback to invoke
176	case.	247	in that case.
177		248
178	The timer callback will be invoked at most once: if you want a repeating	249	Although the callback might get passed parameters, their value and
179	timer you have to create a new watcher (this is a limitation by both Tk	250	presence is undefined and you cannot rely on them. Portable AnyEvent
180	and Glib).	251	callbacks cannot use arguments passed to time watcher callbacks.
181		252
182	Example:	253	The callback will normally be invoked only once. If you specify another
		254	parameter, C<interval>, as a strictly positive number (> 0), then the
		255	callback will be invoked regularly at that interval (in fractional
		256	seconds) after the first invocation. If C<interval> is specified with a
		257	false value, then it is treated as if it were not specified at all.
183		258
		259	The callback will be rescheduled before invoking the callback, but no
		260	attempt is made to avoid timer drift in most backends, so the interval is
		261	only approximate.
		262
184	# fire an event after 7.7 seconds	263	Example: fire an event after 7.7 seconds.
		264
185	my $w = AnyEvent->timer (after => 7.7, cb => sub {	265	my $w = AnyEvent->timer (after => 7.7, cb => sub {
186	warn "timeout\n";	266	warn "timeout\n";
187	});	267	});
188		268
189	# to cancel the timer:	269	# to cancel the timer:
190	undef $w;	270	undef $w;
191		271
192	Example 2:
193
194	# fire an event after 0.5 seconds, then roughly every second	272	Example 2: fire an event after 0.5 seconds, then roughly every second.
195	my $w;
196		273
197	my $cb = sub {
198	# cancel the old timer while creating a new one
199	$w = AnyEvent->timer (after => 1, cb => $cb);	274	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		275	warn "timeout\n";
200	};	276	};
201
202	# start the "loop" by creating the first watcher
203	$w = AnyEvent->timer (after => 0.5, cb => $cb);
204		277
205	=head3 TIMING ISSUES	278	=head3 TIMING ISSUES
206		279
207	There are two ways to handle timers: based on real time (relative, "fire	280	There are two ways to handle timers: based on real time (relative, "fire
208	in 10 seconds") and based on wallclock time (absolute, "fire at 12	281	in 10 seconds") and based on wallclock time (absolute, "fire at 12
209	o'clock").	282	o'clock").
210		283
211	While most event loops expect timers to specified in a relative way, they use	284	While most event loops expect timers to specified in a relative way, they
212	absolute time internally. This makes a difference when your clock "jumps",	285	use absolute time internally. This makes a difference when your clock
213	for example, when ntp decides to set your clock backwards from the wrong 2014-01-01 to	286	"jumps", for example, when ntp decides to set your clock backwards from
214	2008-01-01, a watcher that you created to fire "after" a second might actually take	287	the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to
215	six years to finally fire.	288	fire "after a second" might actually take six years to finally fire.
216		289
217	AnyEvent cannot compensate for this. The only event loop that is conscious	290	AnyEvent cannot compensate for this. The only event loop that is conscious
218	about these issues is L<EV>, which offers both relative (ev_timer) and	291	of these issues is L<EV>, which offers both relative (ev_timer, based
219	absolute (ev_periodic) timers.	292	on true relative time) and absolute (ev_periodic, based on wallclock time)
		293	timers.
220		294
221	AnyEvent always prefers relative timers, if available, matching the	295	AnyEvent always prefers relative timers, if available, matching the
222	AnyEvent API.	296	AnyEvent API.
223		297
		298	AnyEvent has two additional methods that return the "current time":
		299
		300	=over 4
		301
		302	=item AnyEvent->time
		303
		304	This returns the "current wallclock time" as a fractional number of
		305	seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
		306	return, and the result is guaranteed to be compatible with those).
		307
		308	It progresses independently of any event loop processing, i.e. each call
		309	will check the system clock, which usually gets updated frequently.
		310
		311	=item AnyEvent->now
		312
		313	This also returns the "current wallclock time", but unlike C<time>, above,
		314	this value might change only once per event loop iteration, depending on
		315	the event loop (most return the same time as C<time>, above). This is the
		316	time that AnyEvent's timers get scheduled against.
		317
		318	I<In almost all cases (in all cases if you don't care), this is the
		319	function to call when you want to know the current time.>
		320
		321	This function is also often faster then C<< AnyEvent->time >>, and
		322	thus the preferred method if you want some timestamp (for example,
		323	L<AnyEvent::Handle> uses this to update its activity timeouts).
		324
		325	The rest of this section is only of relevance if you try to be very exact
		326	with your timing; you can skip it without a bad conscience.
		327
		328	For a practical example of when these times differ, consider L<Event::Lib>
		329	and L<EV> and the following set-up:
		330
		331	The event loop is running and has just invoked one of your callbacks at
		332	time=500 (assume no other callbacks delay processing). In your callback,
		333	you wait a second by executing C<sleep 1> (blocking the process for a
		334	second) and then (at time=501) you create a relative timer that fires
		335	after three seconds.
		336
		337	With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
		338	both return C<501>, because that is the current time, and the timer will
		339	be scheduled to fire at time=504 (C<501> + C<3>).
		340
		341	With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
		342	time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
		343	last event processing phase started. With L<EV>, your timer gets scheduled
		344	to run at time=503 (C<500> + C<3>).
		345
		346	In one sense, L<Event::Lib> is more exact, as it uses the current time
		347	regardless of any delays introduced by event processing. However, most
		348	callbacks do not expect large delays in processing, so this causes a
		349	higher drift (and a lot more system calls to get the current time).
		350
		351	In another sense, L<EV> is more exact, as your timer will be scheduled at
		352	the same time, regardless of how long event processing actually took.
		353
		354	In either case, if you care (and in most cases, you don't), then you
		355	can get whatever behaviour you want with any event loop, by taking the
		356	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
		357	account.
		358
		359	=item AnyEvent->now_update
		360
		361	Some event loops (such as L<EV> or L<AnyEvent::Loop>) cache the current
		362	time for each loop iteration (see the discussion of L<< AnyEvent->now >>,
		363	above).
		364
		365	When a callback runs for a long time (or when the process sleeps), then
		366	this "current" time will differ substantially from the real time, which
		367	might affect timers and time-outs.
		368
		369	When this is the case, you can call this method, which will update the
		370	event loop's idea of "current time".
		371
		372	A typical example would be a script in a web server (e.g. C<mod_perl>) -
		373	when mod_perl executes the script, then the event loop will have the wrong
		374	idea about the "current time" (being potentially far in the past, when the
		375	script ran the last time). In that case you should arrange a call to C<<
		376	AnyEvent->now_update >> each time the web server process wakes up again
		377	(e.g. at the start of your script, or in a handler).
		378
		379	Note that updating the time I<might> cause some events to be handled.
		380
		381	=back
		382
224	=head2 SIGNAL WATCHERS	383	=head2 SIGNAL WATCHERS
225		384
		385	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		386
226	You can watch for signals using a signal watcher, C<signal> is the signal	387	You can watch for signals using a signal watcher, C<signal> is the signal
227	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to	388	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
228	be invoked whenever a signal occurs.	389	callback to be invoked whenever a signal occurs.
229		390
		391	Although the callback might get passed parameters, their value and
		392	presence is undefined and you cannot rely on them. Portable AnyEvent
		393	callbacks cannot use arguments passed to signal watcher callbacks.
		394
230	Multiple signals occurances can be clumped together into one callback	395	Multiple signal occurrences can be clumped together into one callback
231	invocation, and callback invocation will be synchronous. synchronous means	396	invocation, and callback invocation will be synchronous. Synchronous means
232	that it might take a while until the signal gets handled by the process,	397	that it might take a while until the signal gets handled by the process,
233	but it is guarenteed not to interrupt any other callbacks.	398	but it is guaranteed not to interrupt any other callbacks.
234		399
235	The main advantage of using these watchers is that you can share a signal	400	The main advantage of using these watchers is that you can share a signal
236	between multiple watchers.	401	between multiple watchers, and AnyEvent will ensure that signals will not
		402	interrupt your program at bad times.
237		403
238	This watcher might use C<%SIG>, so programs overwriting those signals	404	This watcher might use C<%SIG> (depending on the event loop used),
239	directly will likely not work correctly.	405	so programs overwriting those signals directly will likely not work
		406	correctly.
240		407
241	Example: exit on SIGINT	408	Example: exit on SIGINT
242		409
243	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	410	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
244		411
		412	=head3 Restart Behaviour
		413
		414	While restart behaviour is up to the event loop implementation, most will
		415	not restart syscalls (that includes L<Async::Interrupt> and AnyEvent's
		416	pure perl implementation).
		417
		418	=head3 Safe/Unsafe Signals
		419
		420	Perl signals can be either "safe" (synchronous to opcode handling) or
		421	"unsafe" (asynchronous) - the former might get delayed indefinitely, the
		422	latter might corrupt your memory.
		423
		424	AnyEvent signal handlers are, in addition, synchronous to the event loop,
		425	i.e. they will not interrupt your running perl program but will only be
		426	called as part of the normal event handling (just like timer, I/O etc.
		427	callbacks, too).
		428
		429	=head3 Signal Races, Delays and Workarounds
		430
		431	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		432	callbacks to signals in a generic way, which is a pity, as you cannot
		433	do race-free signal handling in perl, requiring C libraries for
		434	this. AnyEvent will try to do its best, which means in some cases,
		435	signals will be delayed. The maximum time a signal might be delayed is
		436	specified in C<$AnyEvent::MAX_SIGNAL_LATENCY> (default: 10 seconds). This
		437	variable can be changed only before the first signal watcher is created,
		438	and should be left alone otherwise. This variable determines how often
		439	AnyEvent polls for signals (in case a wake-up was missed). Higher values
		440	will cause fewer spurious wake-ups, which is better for power and CPU
		441	saving.
		442
		443	All these problems can be avoided by installing the optional
		444	L<Async::Interrupt> module, which works with most event loops. It will not
		445	work with inherently broken event loops such as L<Event> or L<Event::Lib>
		446	(and not with L<POE> currently, as POE does its own workaround with
		447	one-second latency). For those, you just have to suffer the delays.
		448
245	=head2 CHILD PROCESS WATCHERS	449	=head2 CHILD PROCESS WATCHERS
246		450
		451	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		452
247	You can also watch on a child process exit and catch its exit status.	453	You can also watch for a child process exit and catch its exit status.
248		454
249	The child process is specified by the C<pid> argument (if set to C<0>, it	455	The child process is specified by the C<pid> argument (on some backends,
250	watches for any child process exit). The watcher will trigger as often	456	using C<0> watches for any child process exit, on others this will
251	as status change for the child are received. This works by installing a	457	croak). The watcher will be triggered only when the child process has
252	signal handler for C<SIGCHLD>. The callback will be called with the pid	458	finished and an exit status is available, not on any trace events
253	and exit status (as returned by waitpid).	459	(stopped/continued).
254		460
255	Example: wait for pid 1333	461	The callback will be called with the pid and exit status (as returned by
		462	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		463	callback arguments.
256		464
		465	This watcher type works by installing a signal handler for C<SIGCHLD>,
		466	and since it cannot be shared, nothing else should use SIGCHLD or reap
		467	random child processes (waiting for specific child processes, e.g. inside
		468	C<system>, is just fine).
		469
		470	There is a slight catch to child watchers, however: you usually start them
		471	I<after> the child process was created, and this means the process could
		472	have exited already (and no SIGCHLD will be sent anymore).
		473
		474	Not all event models handle this correctly (neither POE nor IO::Async do,
		475	see their AnyEvent::Impl manpages for details), but even for event models
		476	that I<do> handle this correctly, they usually need to be loaded before
		477	the process exits (i.e. before you fork in the first place). AnyEvent's
		478	pure perl event loop handles all cases correctly regardless of when you
		479	start the watcher.
		480
		481	This means you cannot create a child watcher as the very first
		482	thing in an AnyEvent program, you I<have> to create at least one
		483	watcher before you C<fork> the child (alternatively, you can call
		484	C<AnyEvent::detect>).
		485
		486	As most event loops do not support waiting for child events, they will be
		487	emulated by AnyEvent in most cases, in which case the latency and race
		488	problems mentioned in the description of signal watchers apply.
		489
		490	Example: fork a process and wait for it
		491
		492	my $done = AnyEvent->condvar;
		493
		494	my $pid = fork or exit 5;
		495
257	my $w = AnyEvent->child (	496	my $w = AnyEvent->child (
258	pid => 1333,	497	pid => $pid,
259	cb => sub {	498	cb => sub {
260	my ($pid, $status) = @_;	499	my ($pid, $status) = @_;
261	warn "pid $pid exited with status $status";	500	warn "pid $pid exited with status $status";
		501	$done->send;
262	},	502	},
263	);	503	);
		504
		505	# do something else, then wait for process exit
		506	$done->recv;
		507
		508	=head2 IDLE WATCHERS
		509
		510	$w = AnyEvent->idle (cb => <callback>);
		511
		512	This will repeatedly invoke the callback after the process becomes idle,
		513	until either the watcher is destroyed or new events have been detected.
		514
		515	Idle watchers are useful when there is a need to do something, but it
		516	is not so important (or wise) to do it instantly. The callback will be
		517	invoked only when there is "nothing better to do", which is usually
		518	defined as "all outstanding events have been handled and no new events
		519	have been detected". That means that idle watchers ideally get invoked
		520	when the event loop has just polled for new events but none have been
		521	detected. Instead of blocking to wait for more events, the idle watchers
		522	will be invoked.
		523
		524	Unfortunately, most event loops do not really support idle watchers (only
		525	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		526	will simply call the callback "from time to time".
		527
		528	Example: read lines from STDIN, but only process them when the
		529	program is otherwise idle:
		530
		531	my @lines; # read data
		532	my $idle_w;
		533	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		534	push @lines, scalar <STDIN>;
		535
		536	# start an idle watcher, if not already done
		537	$idle_w ||= AnyEvent->idle (cb => sub {
		538	# handle only one line, when there are lines left
		539	if (my $line = shift @lines) {
		540	print "handled when idle: $line";
		541	} else {
		542	# otherwise disable the idle watcher again
		543	undef $idle_w;
		544	}
		545	});
		546	});
264		547
265	=head2 CONDITION VARIABLES	548	=head2 CONDITION VARIABLES
266		549
		550	$cv = AnyEvent->condvar;
		551
		552	$cv->send (<list>);
		553	my @res = $cv->recv;
		554
		555	If you are familiar with some event loops you will know that all of them
		556	require you to run some blocking "loop", "run" or similar function that
		557	will actively watch for new events and call your callbacks.
		558
		559	AnyEvent is slightly different: it expects somebody else to run the event
		560	loop and will only block when necessary (usually when told by the user).
		561
		562	The tool to do that is called a "condition variable", so called because
		563	they represent a condition that must become true.
		564
		565	Now is probably a good time to look at the examples further below.
		566
267	Condition variables can be created by calling the C<< AnyEvent->condvar >>	567	Condition variables can be created by calling the C<< AnyEvent->condvar
268	method without any arguments.	568	>> method, usually without arguments. The only argument pair allowed is
		569	C<cb>, which specifies a callback to be called when the condition variable
		570	becomes true, with the condition variable as the first argument (but not
		571	the results).
269		572
270	A condition variable waits for a condition - precisely that the C<<	573	After creation, the condition variable is "false" until it becomes "true"
271	->broadcast >> method has been called.	574	by calling the C<send> method (or calling the condition variable as if it
		575	were a callback, read about the caveats in the description for the C<<
		576	->send >> method).
272		577
273	They are very useful to signal that a condition has been fulfilled, for	578	Since condition variables are the most complex part of the AnyEvent API, here are
		579	some different mental models of what they are - pick the ones you can connect to:
		580
		581	=over 4
		582
		583	=item * Condition variables are like callbacks - you can call them (and pass them instead
		584	of callbacks). Unlike callbacks however, you can also wait for them to be called.
		585
		586	=item * Condition variables are signals - one side can emit or send them,
		587	the other side can wait for them, or install a handler that is called when
		588	the signal fires.
		589
		590	=item * Condition variables are like "Merge Points" - points in your program
		591	where you merge multiple independent results/control flows into one.
		592
		593	=item * Condition variables represent a transaction - functions that start
		594	some kind of transaction can return them, leaving the caller the choice
		595	between waiting in a blocking fashion, or setting a callback.
		596
		597	=item * Condition variables represent future values, or promises to deliver
		598	some result, long before the result is available.
		599
		600	=back
		601
		602	Condition variables are very useful to signal that something has finished,
274	example, if you write a module that does asynchronous http requests,	603	for example, if you write a module that does asynchronous http requests,
275	then a condition variable would be the ideal candidate to signal the	604	then a condition variable would be the ideal candidate to signal the
276	availability of results.	605	availability of results. The user can either act when the callback is
		606	called or can synchronously C<< ->recv >> for the results.
277		607
278	You can also use condition variables to block your main program until	608	You can also use them to simulate traditional event loops - for example,
279	an event occurs - for example, you could C<< ->wait >> in your main	609	you can block your main program until an event occurs - for example, you
280	program until the user clicks the Quit button in your app, which would C<<	610	could C<< ->recv >> in your main program until the user clicks the Quit
281	->broadcast >> the "quit" event.	611	button of your app, which would C<< ->send >> the "quit" event.
282		612
283	Note that condition variables recurse into the event loop - if you have	613	Note that condition variables recurse into the event loop - if you have
284	two pirces of code that call C<< ->wait >> in a round-robbin fashion, you	614	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
285	lose. Therefore, condition variables are good to export to your caller, but	615	lose. Therefore, condition variables are good to export to your caller, but
286	you should avoid making a blocking wait yourself, at least in callbacks,	616	you should avoid making a blocking wait yourself, at least in callbacks,
287	as this asks for trouble.	617	as this asks for trouble.
288		618
289	This object has two methods:	619	Condition variables are represented by hash refs in perl, and the keys
		620	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
		621	easy (it is often useful to build your own transaction class on top of
		622	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
		623	its C<new> method in your own C<new> method.
		624
		625	There are two "sides" to a condition variable - the "producer side" which
		626	eventually calls C<< -> send >>, and the "consumer side", which waits
		627	for the send to occur.
		628
		629	Example: wait for a timer.
		630
		631	# condition: "wait till the timer is fired"
		632	my $timer_fired = AnyEvent->condvar;
		633
		634	# create the timer - we could wait for, say
		635	# a handle becomign ready, or even an
		636	# AnyEvent::HTTP request to finish, but
		637	# in this case, we simply use a timer:
		638	my $w = AnyEvent->timer (
		639	after => 1,
		640	cb => sub { $timer_fired->send },
		641	);
		642
		643	# this "blocks" (while handling events) till the callback
		644	# calls ->send
		645	$timer_fired->recv;
		646
		647	Example: wait for a timer, but take advantage of the fact that condition
		648	variables are also callable directly.
		649
		650	my $done = AnyEvent->condvar;
		651	my $delay = AnyEvent->timer (after => 5, cb => $done);
		652	$done->recv;
		653
		654	Example: Imagine an API that returns a condvar and doesn't support
		655	callbacks. This is how you make a synchronous call, for example from
		656	the main program:
		657
		658	use AnyEvent::CouchDB;
		659
		660	...
		661
		662	my @info = $couchdb->info->recv;
		663
		664	And this is how you would just set a callback to be called whenever the
		665	results are available:
		666
		667	$couchdb->info->cb (sub {
		668	my @info = $_[0]->recv;
		669	});
		670
		671	=head3 METHODS FOR PRODUCERS
		672
		673	These methods should only be used by the producing side, i.e. the
		674	code/module that eventually sends the signal. Note that it is also
		675	the producer side which creates the condvar in most cases, but it isn't
		676	uncommon for the consumer to create it as well.
290		677
291	=over 4	678	=over 4
292		679
		680	=item $cv->send (...)
		681
		682	Flag the condition as ready - a running C<< ->recv >> and all further
		683	calls to C<recv> will (eventually) return after this method has been
		684	called. If nobody is waiting the send will be remembered.
		685
		686	If a callback has been set on the condition variable, it is called
		687	immediately from within send.
		688
		689	Any arguments passed to the C<send> call will be returned by all
		690	future C<< ->recv >> calls.
		691
		692	Condition variables are overloaded so one can call them directly (as if
		693	they were a code reference). Calling them directly is the same as calling
		694	C<send>.
		695
		696	=item $cv->croak ($error)
		697
		698	Similar to send, but causes all calls to C<< ->recv >> to invoke
		699	C<Carp::croak> with the given error message/object/scalar.
		700
		701	This can be used to signal any errors to the condition variable
		702	user/consumer. Doing it this way instead of calling C<croak> directly
		703	delays the error detection, but has the overwhelming advantage that it
		704	diagnoses the error at the place where the result is expected, and not
		705	deep in some event callback with no connection to the actual code causing
		706	the problem.
		707
		708	=item $cv->begin ([group callback])
		709
293	=item $cv->wait	710	=item $cv->end
294		711
295	Wait (blocking if necessary) until the C<< ->broadcast >> method has been	712	These two methods can be used to combine many transactions/events into
296	called on c<$cv>, while servicing other watchers normally.	713	one. For example, a function that pings many hosts in parallel might want
		714	to use a condition variable for the whole process.
297		715
		716	Every call to C<< ->begin >> will increment a counter, and every call to
		717	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
		718	>>, the (last) callback passed to C<begin> will be executed, passing the
		719	condvar as first argument. That callback is I<supposed> to call C<< ->send
		720	>>, but that is not required. If no group callback was set, C<send> will
		721	be called without any arguments.
		722
		723	You can think of C<< $cv->send >> giving you an OR condition (one call
		724	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		725	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		726
		727	Let's start with a simple example: you have two I/O watchers (for example,
		728	STDOUT and STDERR for a program), and you want to wait for both streams to
		729	close before activating a condvar:
		730
		731	my $cv = AnyEvent->condvar;
		732
		733	$cv->begin; # first watcher
		734	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		735	defined sysread $fh1, my $buf, 4096
		736	or $cv->end;
		737	});
		738
		739	$cv->begin; # second watcher
		740	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		741	defined sysread $fh2, my $buf, 4096
		742	or $cv->end;
		743	});
		744
		745	$cv->recv;
		746
		747	This works because for every event source (EOF on file handle), there is
		748	one call to C<begin>, so the condvar waits for all calls to C<end> before
		749	sending.
		750
		751	The ping example mentioned above is slightly more complicated, as the
		752	there are results to be passwd back, and the number of tasks that are
		753	begun can potentially be zero:
		754
		755	my $cv = AnyEvent->condvar;
		756
		757	my %result;
		758	$cv->begin (sub { shift->send (\%result) });
		759
		760	for my $host (@list_of_hosts) {
		761	$cv->begin;
		762	ping_host_then_call_callback $host, sub {
		763	$result{$host} = ...;
		764	$cv->end;
		765	};
		766	}
		767
		768	$cv->end;
		769
		770	This code fragment supposedly pings a number of hosts and calls
		771	C<send> after results for all then have have been gathered - in any
		772	order. To achieve this, the code issues a call to C<begin> when it starts
		773	each ping request and calls C<end> when it has received some result for
		774	it. Since C<begin> and C<end> only maintain a counter, the order in which
		775	results arrive is not relevant.
		776
		777	There is an additional bracketing call to C<begin> and C<end> outside the
		778	loop, which serves two important purposes: first, it sets the callback
		779	to be called once the counter reaches C<0>, and second, it ensures that
		780	C<send> is called even when C<no> hosts are being pinged (the loop
		781	doesn't execute once).
		782
		783	This is the general pattern when you "fan out" into multiple (but
		784	potentially zero) subrequests: use an outer C<begin>/C<end> pair to set
		785	the callback and ensure C<end> is called at least once, and then, for each
		786	subrequest you start, call C<begin> and for each subrequest you finish,
		787	call C<end>.
		788
		789	=back
		790
		791	=head3 METHODS FOR CONSUMERS
		792
		793	These methods should only be used by the consuming side, i.e. the
		794	code awaits the condition.
		795
		796	=over 4
		797
		798	=item $cv->recv
		799
		800	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
		801	>> methods have been called on C<$cv>, while servicing other watchers
		802	normally.
		803
298	You can only wait once on a condition - additional calls will return	804	You can only wait once on a condition - additional calls are valid but
299	immediately.	805	will return immediately.
		806
		807	If an error condition has been set by calling C<< ->croak >>, then this
		808	function will call C<croak>.
		809
		810	In list context, all parameters passed to C<send> will be returned,
		811	in scalar context only the first one will be returned.
		812
		813	Note that doing a blocking wait in a callback is not supported by any
		814	event loop, that is, recursive invocation of a blocking C<< ->recv
		815	>> is not allowed, and the C<recv> call will C<croak> if such a
		816	condition is detected. This condition can be slightly loosened by using
		817	L<Coro::AnyEvent>, which allows you to do a blocking C<< ->recv >> from
		818	any thread that doesn't run the event loop itself.
300		819
301	Not all event models support a blocking wait - some die in that case	820	Not all event models support a blocking wait - some die in that case
302	(programs might want to do that to stay interactive), so I<if you are	821	(programs might want to do that to stay interactive), so I<if you are
303	using this from a module, never require a blocking wait>, but let the	822	using this from a module, never require a blocking wait>. Instead, let the
304	caller decide whether the call will block or not (for example, by coupling	823	caller decide whether the call will block or not (for example, by coupling
305	condition variables with some kind of request results and supporting	824	condition variables with some kind of request results and supporting
306	callbacks so the caller knows that getting the result will not block,	825	callbacks so the caller knows that getting the result will not block,
307	while still suppporting blocking waits if the caller so desires).	826	while still supporting blocking waits if the caller so desires).
308		827
309	Another reason I<never> to C<< ->wait >> in a module is that you cannot	828	You can ensure that C<< ->recv >> never blocks by setting a callback and
310	sensibly have two C<< ->wait >>'s in parallel, as that would require	829	only calling C<< ->recv >> from within that callback (or at a later
311	multiple interpreters or coroutines/threads, none of which C<AnyEvent>	830	time). This will work even when the event loop does not support blocking
312	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and	831	waits otherwise.
313	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
314	from different coroutines, however).
315		832
316	=item $cv->broadcast	833	=item $bool = $cv->ready
317		834
318	Flag the condition as ready - a running C<< ->wait >> and all further	835	Returns true when the condition is "true", i.e. whether C<send> or
319	calls to C<wait> will (eventually) return after this method has been	836	C<croak> have been called.
320	called. If nobody is waiting the broadcast will be remembered..	837
		838	=item $cb = $cv->cb ($cb->($cv))
		839
		840	This is a mutator function that returns the callback set and optionally
		841	replaces it before doing so.
		842
		843	The callback will be called when the condition becomes "true", i.e. when
		844	C<send> or C<croak> are called, with the only argument being the
		845	condition variable itself. If the condition is already true, the
		846	callback is called immediately when it is set. Calling C<recv> inside
		847	the callback or at any later time is guaranteed not to block.
321		848
322	=back	849	=back
323		850
324	Example:	851	=head1 SUPPORTED EVENT LOOPS/BACKENDS
325		852
326	# wait till the result is ready	853	The available backend classes are (every class has its own manpage):
327	my $result_ready = AnyEvent->condvar;
328		854
329	# do something such as adding a timer	855	=over 4
330	# or socket watcher the calls $result_ready->broadcast
331	# when the "result" is ready.
332	# in this case, we simply use a timer:
333	my $w = AnyEvent->timer (
334	after => 1,
335	cb => sub { $result_ready->broadcast },
336	);
337		856
338	# this "blocks" (while handling events) till the watcher	857	=item Backends that are autoprobed when no other event loop can be found.
339	# calls broadcast	858
340	$result_ready->wait;	859	EV is the preferred backend when no other event loop seems to be in
		860	use. If EV is not installed, then AnyEvent will fall back to its own
		861	pure-perl implementation, which is available everywhere as it comes with
		862	AnyEvent itself.
		863
		864	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		865	AnyEvent::Impl::Perl pure-perl AnyEvent::Loop, fast and portable.
		866
		867	=item Backends that are transparently being picked up when they are used.
		868
		869	These will be used if they are already loaded when the first watcher
		870	is created, in which case it is assumed that the application is using
		871	them. This means that AnyEvent will automatically pick the right backend
		872	when the main program loads an event module before anything starts to
		873	create watchers. Nothing special needs to be done by the main program.
		874
		875	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		876	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		877	AnyEvent::Impl::Tk based on Tk, very broken.
		878	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		879	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		880	AnyEvent::Impl::Irssi used when running within irssi.
		881	AnyEvent::Impl::IOAsync based on IO::Async.
		882	AnyEvent::Impl::Cocoa based on Cocoa::EventLoop.
		883	AnyEvent::Impl::FLTK based on FLTK (fltk 2 binding).
		884
		885	=item Backends with special needs.
		886
		887	Qt requires the Qt::Application to be instantiated first, but will
		888	otherwise be picked up automatically. As long as the main program
		889	instantiates the application before any AnyEvent watchers are created,
		890	everything should just work.
		891
		892	AnyEvent::Impl::Qt based on Qt.
		893
		894	=item Event loops that are indirectly supported via other backends.
		895
		896	Some event loops can be supported via other modules:
		897
		898	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		899
		900	B<WxWidgets> has no support for watching file handles. However, you can
		901	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		902	polls 20 times per second, which was considered to be too horrible to even
		903	consider for AnyEvent.
		904
		905	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		906	backend, so it can be supported through POE.
		907
		908	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		909	load L<POE> when detecting them, in the hope that POE will pick them up,
		910	in which case everything will be automatic.
		911
		912	=back
341		913
342	=head1 GLOBAL VARIABLES AND FUNCTIONS	914	=head1 GLOBAL VARIABLES AND FUNCTIONS
343		915
		916	These are not normally required to use AnyEvent, but can be useful to
		917	write AnyEvent extension modules.
		918
344	=over 4	919	=over 4
345		920
346	=item $AnyEvent::MODEL	921	=item $AnyEvent::MODEL
347		922
348	Contains C<undef> until the first watcher is being created. Then it	923	Contains C<undef> until the first watcher is being created, before the
		924	backend has been autodetected.
		925
349	contains the event model that is being used, which is the name of the	926	Afterwards it contains the event model that is being used, which is the
350	Perl class implementing the model. This class is usually one of the	927	name of the Perl class implementing the model. This class is usually one
351	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	928	of the C<AnyEvent::Impl::xxx> modules, but can be any other class in the
352	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	929	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
353		930	will be C<urxvt::anyevent>).
354	The known classes so far are:
355
356	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
357	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
358	AnyEvent::Impl::EV based on EV (an interface to libev, also best choice).
359	AnyEvent::Impl::Event based on Event, also second best choice :)
360	AnyEvent::Impl::Glib based on Glib, third-best choice.
361	AnyEvent::Impl::Tk based on Tk, very bad choice.
362	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
363	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
364		931
365	=item AnyEvent::detect	932	=item AnyEvent::detect
366		933
367	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	934	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
368	if necessary. You should only call this function right before you would	935	if necessary. You should only call this function right before you would
369	have created an AnyEvent watcher anyway, that is, as late as possible at	936	have created an AnyEvent watcher anyway, that is, as late as possible at
370	runtime.	937	runtime, and not e.g. during initialisation of your module.
		938
		939	The effect of calling this function is as if a watcher had been created
		940	(specifically, actions that happen "when the first watcher is created"
		941	happen when calling detetc as well).
		942
		943	If you need to do some initialisation before AnyEvent watchers are
		944	created, use C<post_detect>.
		945
		946	=item $guard = AnyEvent::post_detect { BLOCK }
		947
		948	Arranges for the code block to be executed as soon as the event model is
		949	autodetected (or immediately if that has already happened).
		950
		951	The block will be executed I<after> the actual backend has been detected
		952	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		953	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		954	other initialisations - see the sources of L<AnyEvent::Strict> or
		955	L<AnyEvent::AIO> to see how this is used.
		956
		957	The most common usage is to create some global watchers, without forcing
		958	event module detection too early, for example, L<AnyEvent::AIO> creates
		959	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		960	avoid autodetecting the event module at load time.
		961
		962	If called in scalar or list context, then it creates and returns an object
		963	that automatically removes the callback again when it is destroyed (or
		964	C<undef> when the hook was immediately executed). See L<AnyEvent::AIO> for
		965	a case where this is useful.
		966
		967	Example: Create a watcher for the IO::AIO module and store it in
		968	C<$WATCHER>, but do so only do so after the event loop is initialised.
		969
		970	our WATCHER;
		971
		972	my $guard = AnyEvent::post_detect {
		973	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		974	};
		975
		976	# the ||= is important in case post_detect immediately runs the block,
		977	# as to not clobber the newly-created watcher. assigning both watcher and
		978	# post_detect guard to the same variable has the advantage of users being
		979	# able to just C<undef $WATCHER> if the watcher causes them grief.
		980
		981	$WATCHER ||= $guard;
		982
		983	=item @AnyEvent::post_detect
		984
		985	If there are any code references in this array (you can C<push> to it
		986	before or after loading AnyEvent), then they will be called directly
		987	after the event loop has been chosen.
		988
		989	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		990	if it is defined then the event loop has already been detected, and the
		991	array will be ignored.
		992
		993	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		994	it, as it takes care of these details.
		995
		996	This variable is mainly useful for modules that can do something useful
		997	when AnyEvent is used and thus want to know when it is initialised, but do
		998	not need to even load it by default. This array provides the means to hook
		999	into AnyEvent passively, without loading it.
		1000
		1001	Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used
		1002	together, you could put this into Coro (this is the actual code used by
		1003	Coro to accomplish this):
		1004
		1005	if (defined $AnyEvent::MODEL) {
		1006	# AnyEvent already initialised, so load Coro::AnyEvent
		1007	require Coro::AnyEvent;
		1008	} else {
		1009	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent
		1010	# as soon as it is
		1011	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };
		1012	}
		1013
		1014	=item AnyEvent::postpone { BLOCK }
		1015
		1016	Arranges for the block to be executed as soon as possible, but not before
		1017	the call itself returns. In practise, the block will be executed just
		1018	before the event loop polls for new events, or shortly afterwards.
		1019
		1020	This function never returns anything (to make the C<return postpone { ...
		1021	}> idiom more useful.
		1022
		1023	To understand the usefulness of this function, consider a function that
		1024	asynchronously does something for you and returns some transaction
		1025	object or guard to let you cancel the operation. For example,
		1026	C<AnyEvent::Socket::tcp_connect>:
		1027
		1028	# start a conenction attempt unless one is active
		1029	$self->{connect_guard} ||= AnyEvent::Socket::tcp_connect "www.example.net", 80, sub {
		1030	delete $self->{connect_guard};
		1031	...
		1032	};
		1033
		1034	Imagine that this function could instantly call the callback, for
		1035	example, because it detects an obvious error such as a negative port
		1036	number. Invoking the callback before the function returns causes problems
		1037	however: the callback will be called and will try to delete the guard
		1038	object. But since the function hasn't returned yet, there is nothing to
		1039	delete. When the function eventually returns it will assign the guard
		1040	object to C<< $self->{connect_guard} >>, where it will likely never be
		1041	deleted, so the program thinks it is still trying to connect.
		1042
		1043	This is where C<AnyEvent::postpone> should be used. Instead of calling the
		1044	callback directly on error:
		1045
		1046	$cb->(undef), return # signal error to callback, BAD!
		1047	if $some_error_condition;
		1048
		1049	It should use C<postpone>:
		1050
		1051	AnyEvent::postpone { $cb->(undef) }, return # signal error to callback, later
		1052	if $some_error_condition;
		1053
		1054	=item AnyEvent::log $level, $msg[, @args]
		1055
		1056	Log the given C<$msg> at the given C<$level>.
		1057
		1058	If L<AnyEvent::Log> is not loaded then this function makes a simple test
		1059	to see whether the message will be logged. If the test succeeds it will
		1060	load AnyEvent::Log and call C<AnyEvent::Log::log> - consequently, look at
		1061	the L<AnyEvent::Log> documentation for details.
		1062
		1063	If the test fails it will simply return. Right now this happens when a
		1064	numerical loglevel is used and it is larger than the level specified via
		1065	C<$ENV{PERL_ANYEVENT_VERBOSE}>.
		1066
		1067	If you want to sprinkle loads of logging calls around your code, consider
		1068	creating a logger callback with the C<AnyEvent::Log::logger> function,
		1069	which can reduce typing, codesize and can reduce the logging overhead
		1070	enourmously.
371		1071
372	=back	1072	=back
373		1073
374	=head1 WHAT TO DO IN A MODULE	1074	=head1 WHAT TO DO IN A MODULE
375		1075
…		…
379	Be careful when you create watchers in the module body - AnyEvent will	1079	Be careful when you create watchers in the module body - AnyEvent will
380	decide which event module to use as soon as the first method is called, so	1080	decide which event module to use as soon as the first method is called, so
381	by calling AnyEvent in your module body you force the user of your module	1081	by calling AnyEvent in your module body you force the user of your module
382	to load the event module first.	1082	to load the event module first.
383		1083
384	Never call C<< ->wait >> on a condition variable unless you I<know> that	1084	Never call C<< ->recv >> on a condition variable unless you I<know> that
385	the C<< ->broadcast >> method has been called on it already. This is	1085	the C<< ->send >> method has been called on it already. This is
386	because it will stall the whole program, and the whole point of using	1086	because it will stall the whole program, and the whole point of using
387	events is to stay interactive.	1087	events is to stay interactive.
388		1088
389	It is fine, however, to call C<< ->wait >> when the user of your module	1089	It is fine, however, to call C<< ->recv >> when the user of your module
390	requests it (i.e. if you create a http request object ad have a method	1090	requests it (i.e. if you create a http request object ad have a method
391	called C<results> that returns the results, it should call C<< ->wait >>	1091	called C<results> that returns the results, it may call C<< ->recv >>
392	freely, as the user of your module knows what she is doing. always).	1092	freely, as the user of your module knows what she is doing. Always).
393		1093
394	=head1 WHAT TO DO IN THE MAIN PROGRAM	1094	=head1 WHAT TO DO IN THE MAIN PROGRAM
395		1095
396	There will always be a single main program - the only place that should	1096	There will always be a single main program - the only place that should
397	dictate which event model to use.	1097	dictate which event model to use.
398		1098
399	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	1099	If the program is not event-based, it need not do anything special, even
400	do anything special (it does not need to be event-based) and let AnyEvent	1100	when it depends on a module that uses an AnyEvent. If the program itself
401	decide which implementation to chose if some module relies on it.	1101	uses AnyEvent, but does not care which event loop is used, all it needs
		1102	to do is C<use AnyEvent>. In either case, AnyEvent will choose the best
		1103	available loop implementation.
402		1104
403	If the main program relies on a specific event model. For example, in	1105	If the main program relies on a specific event model - for example, in
404	Gtk2 programs you have to rely on the Glib module. You should load the	1106	Gtk2 programs you have to rely on the Glib module - you should load the
405	event module before loading AnyEvent or any module that uses it: generally	1107	event module before loading AnyEvent or any module that uses it: generally
406	speaking, you should load it as early as possible. The reason is that	1108	speaking, you should load it as early as possible. The reason is that
407	modules might create watchers when they are loaded, and AnyEvent will	1109	modules might create watchers when they are loaded, and AnyEvent will
408	decide on the event model to use as soon as it creates watchers, and it	1110	decide on the event model to use as soon as it creates watchers, and it
409	might chose the wrong one unless you load the correct one yourself.	1111	might choose the wrong one unless you load the correct one yourself.
410		1112
411	You can chose to use a rather inefficient pure-perl implementation by	1113	You can chose to use a pure-perl implementation by loading the
412	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	1114	C<AnyEvent::Loop> module, which gives you similar behaviour
413	behaviour everywhere, but letting AnyEvent chose is generally better.	1115	everywhere, but letting AnyEvent chose the model is generally better.
		1116
		1117	=head2 MAINLOOP EMULATION
		1118
		1119	Sometimes (often for short test scripts, or even standalone programs who
		1120	only want to use AnyEvent), you do not want to run a specific event loop.
		1121
		1122	In that case, you can use a condition variable like this:
		1123
		1124	AnyEvent->condvar->recv;
		1125
		1126	This has the effect of entering the event loop and looping forever.
		1127
		1128	Note that usually your program has some exit condition, in which case
		1129	it is better to use the "traditional" approach of storing a condition
		1130	variable somewhere, waiting for it, and sending it when the program should
		1131	exit cleanly.
		1132
		1133
		1134	=head1 OTHER MODULES
		1135
		1136	The following is a non-exhaustive list of additional modules that use
		1137	AnyEvent as a client and can therefore be mixed easily with other
		1138	AnyEvent modules and other event loops in the same program. Some of the
		1139	modules come as part of AnyEvent, the others are available via CPAN (see
		1140	L<http://search.cpan.org/search?m=module&q=anyevent%3A%3A*> for
		1141	a longer non-exhaustive list), and the list is heavily biased towards
		1142	modules of the AnyEvent author himself :)
		1143
		1144	=over 4
		1145
		1146	=item L<AnyEvent::Util>
		1147
		1148	Contains various utility functions that replace often-used blocking
		1149	functions such as C<inet_aton> with event/callback-based versions.
		1150
		1151	=item L<AnyEvent::Socket>
		1152
		1153	Provides various utility functions for (internet protocol) sockets,
		1154	addresses and name resolution. Also functions to create non-blocking tcp
		1155	connections or tcp servers, with IPv6 and SRV record support and more.
		1156
		1157	=item L<AnyEvent::Handle>
		1158
		1159	Provide read and write buffers, manages watchers for reads and writes,
		1160	supports raw and formatted I/O, I/O queued and fully transparent and
		1161	non-blocking SSL/TLS (via L<AnyEvent::TLS>).
		1162
		1163	=item L<AnyEvent::DNS>
		1164
		1165	Provides rich asynchronous DNS resolver capabilities.
		1166
		1167	=item L<AnyEvent::HTTP>, L<AnyEvent::IRC>, L<AnyEvent::XMPP>, L<AnyEvent::GPSD>, L<AnyEvent::IGS>, L<AnyEvent::FCP>
		1168
		1169	Implement event-based interfaces to the protocols of the same name (for
		1170	the curious, IGS is the International Go Server and FCP is the Freenet
		1171	Client Protocol).
		1172
		1173	=item L<AnyEvent::AIO>
		1174
		1175	Truly asynchronous (as opposed to non-blocking) I/O, should be in the
		1176	toolbox of every event programmer. AnyEvent::AIO transparently fuses
		1177	L<IO::AIO> and AnyEvent together, giving AnyEvent access to event-based
		1178	file I/O, and much more.
		1179
		1180	=item L<AnyEvent::Filesys::Notify>
		1181
		1182	AnyEvent is good for non-blocking stuff, but it can't detect file or
		1183	path changes (e.g. "watch this directory for new files", "watch this
		1184	file for changes"). The L<AnyEvent::Filesys::Notify> module promises to
		1185	do just that in a portbale fashion, supporting inotify on GNU/Linux and
		1186	some weird, without doubt broken, stuff on OS X to monitor files. It can
		1187	fall back to blocking scans at regular intervals transparently on other
		1188	platforms, so it's about as portable as it gets.
		1189
		1190	(I haven't used it myself, but I haven't heard anybody complaining about
		1191	it yet).
		1192
		1193	=item L<AnyEvent::DBI>
		1194
		1195	Executes L<DBI> requests asynchronously in a proxy process for you,
		1196	notifying you in an event-based way when the operation is finished.
		1197
		1198	=item L<AnyEvent::HTTPD>
		1199
		1200	A simple embedded webserver.
		1201
		1202	=item L<AnyEvent::FastPing>
		1203
		1204	The fastest ping in the west.
		1205
		1206	=item L<Coro>
		1207
		1208	Has special support for AnyEvent via L<Coro::AnyEvent>, which allows you
		1209	to simply invert the flow control - don't call us, we will call you:
		1210
		1211	async {
		1212	Coro::AnyEvent::sleep 5; # creates a 5s timer and waits for it
		1213	print "5 seconds later!\n";
		1214
		1215	Coro::AnyEvent::readable *STDIN; # uses an I/O watcher
		1216	my $line = <STDIN>; # works for ttys
		1217
		1218	AnyEvent::HTTP::http_get "url", Coro::rouse_cb;
		1219	my ($body, $hdr) = Coro::rouse_wait;
		1220	};
		1221
		1222	=back
414		1223
415	=cut	1224	=cut
416		1225
417	package AnyEvent;	1226	package AnyEvent;
418		1227
419	no warnings;	1228	# basically a tuned-down version of common::sense
420	use strict;	1229	sub common_sense {
		1230	# from common:.sense 3.4
		1231	${^WARNING_BITS} ^= ${^WARNING_BITS} ^ "\x3c\x3f\x33\x00\x0f\xf0\x0f\xc0\xf0\xfc\x33\x00";
		1232	# use strict vars subs - NO UTF-8, as Util.pm doesn't like this atm. (uts46data.pl)
		1233	$^H |= 0x00000600;
		1234	}
421		1235
		1236	BEGIN { AnyEvent::common_sense }
		1237
422	use Carp;	1238	use Carp ();
423		1239
424	our $VERSION = '3.12';	1240	our $VERSION = '6.02';
425	our $MODEL;	1241	our $MODEL;
426		1242
427	our $AUTOLOAD;
428	our @ISA;	1243	our @ISA;
429		1244
430	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
431
432	our @REGISTRY;	1245	our @REGISTRY;
433		1246
		1247	our $VERBOSE;
		1248
		1249	BEGIN {
		1250	require "AnyEvent/constants.pl";
		1251
		1252	eval "sub TAINT (){" . (${^TAINT}*1) . "}";
		1253
		1254	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1255	if ${^TAINT};
		1256
		1257	$ENV{"PERL_ANYEVENT_$_"} = $ENV{"AE_$_"}
		1258	for grep s/^AE_// && !exists $ENV{"PERL_ANYEVENT_$_"}, keys %ENV;
		1259
		1260	@ENV{grep /^PERL_ANYEVENT_/, keys %ENV} = ()
		1261	if ${^TAINT};
		1262
		1263	# $ENV{PERL_ANYEVENT_xxx} now valid
		1264
		1265	$VERBOSE = length $ENV{PERL_ANYEVENT_VERBOSE} ? $ENV{PERL_ANYEVENT_VERBOSE}*1 : 3;
		1266	}
		1267
		1268	our $MAX_SIGNAL_LATENCY = 10;
		1269
		1270	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		1271
		1272	{
		1273	my $idx;
		1274	$PROTOCOL{$_} = ++$idx
		1275	for reverse split /\s*,\s*/,
		1276	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		1277	}
		1278
		1279	our @post_detect;
		1280
		1281	sub post_detect(&) {
		1282	my ($cb) = @_;
		1283
		1284	push @post_detect, $cb;
		1285
		1286	defined wantarray
		1287	? bless \$cb, "AnyEvent::Util::postdetect"
		1288	: ()
		1289	}
		1290
		1291	sub AnyEvent::Util::postdetect::DESTROY {
		1292	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		1293	}
		1294
		1295	our $POSTPONE_W;
		1296	our @POSTPONE;
		1297
		1298	sub _postpone_exec {
		1299	undef $POSTPONE_W;
		1300
		1301	&{ shift @POSTPONE }
		1302	while @POSTPONE;
		1303	}
		1304
		1305	sub postpone(&) {
		1306	push @POSTPONE, shift;
		1307
		1308	$POSTPONE_W ||= AE::timer (0, 0, \&_postpone_exec);
		1309
		1310	()
		1311	}
		1312
		1313	sub log($$;@) {
		1314	# only load the big bloated module when we actually are about to log something
		1315	if ($_[0] <= $VERBOSE) { # also catches non-numeric levels(!)
		1316	require AnyEvent::Log;
		1317	# AnyEvent::Log overwrites this function
		1318	goto &log;
		1319	}
		1320
		1321	0 # not logged
		1322	}
		1323
		1324	if (length $ENV{PERL_ANYEVENT_LOG}) {
		1325	require AnyEvent::Log; # AnyEvent::Log does the thing for us
		1326	}
		1327
434	my @models = (	1328	our @models = (
435	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
436	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
437	[EV:: => AnyEvent::Impl::EV::],	1329	[EV:: => AnyEvent::Impl::EV:: , 1],
		1330	[AnyEvent::Loop:: => AnyEvent::Impl::Perl:: , 1],
		1331	# everything below here will not (normally) be autoprobed
		1332	# as the pure perl backend should work everywhere
		1333	# and is usually faster
438	[Event:: => AnyEvent::Impl::Event::],	1334	[Event:: => AnyEvent::Impl::Event::, 1],
439	[Glib:: => AnyEvent::Impl::Glib::],	1335	[Glib:: => AnyEvent::Impl::Glib:: , 1], # becomes extremely slow with many watchers
		1336	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		1337	[Irssi:: => AnyEvent::Impl::Irssi::], # Irssi has a bogus "Event" package
		1338	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		1339	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		1340	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
440	[Tk:: => AnyEvent::Impl::Tk::],	1341	[Wx:: => AnyEvent::Impl::POE::],
441	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1342	[Prima:: => AnyEvent::Impl::POE::],
442	[Event::Lib:: => AnyEvent::Impl::EventLib::],	1343	[IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # a bitch to autodetect
		1344	[Cocoa::EventLoop:: => AnyEvent::Impl::Cocoa::],
		1345	[FLTK:: => AnyEvent::Impl::FLTK::],
443	);	1346	);
444		1347
445	our %method = map +($_ => 1), qw(io timer condvar broadcast wait signal one_event DESTROY);	1348	our @isa_hook;
		1349
		1350	sub _isa_set {
		1351	my @pkg = ("AnyEvent", (map $_->[0], grep defined, @isa_hook), $MODEL);
		1352
		1353	@{"$pkg[$_-1]::ISA"} = $pkg[$_]
		1354	for 1 .. $#pkg;
		1355
		1356	grep $_ && $_->[1], @isa_hook
		1357	and AE::_reset ();
		1358	}
		1359
		1360	# used for hooking AnyEvent::Strict and AnyEvent::Debug::Wrap into the class hierarchy
		1361	sub _isa_hook($$;$) {
		1362	my ($i, $pkg, $reset_ae) = @_;
		1363
		1364	$isa_hook[$i] = $pkg ? [$pkg, $reset_ae] : undef;
		1365
		1366	_isa_set;
		1367	}
		1368
		1369	# all autoloaded methods reserve the complete glob, not just the method slot.
		1370	# due to bugs in perls method cache implementation.
		1371	our @methods = qw(io timer time now now_update signal child idle condvar);
446		1372
447	sub detect() {	1373	sub detect() {
		1374	return $MODEL if $MODEL; # some programs keep references to detect
		1375
		1376	local $!; # for good measure
		1377	local $SIG{__DIE__}; # we use eval
		1378
		1379	# free some memory
		1380	*detect = sub () { $MODEL };
		1381	# undef &func doesn't correctly update the method cache. grmbl.
		1382	# so we delete the whole glob. grmbl.
		1383	# otoh, perl doesn't let me undef an active usb, but it lets me free
		1384	# a glob with an active sub. hrm. i hope it works, but perl is
		1385	# usually buggy in this department. sigh.
		1386	delete @{"AnyEvent::"}{@methods};
		1387	undef @methods;
		1388
		1389	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z0-9:]+)$/) {
		1390	my $model = $1;
		1391	$model = "AnyEvent::Impl::$model" unless $model =~ s/::$//;
		1392	if (eval "require $model") {
		1393	AnyEvent::log 7 => "loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.";
		1394	$MODEL = $model;
		1395	} else {
		1396	AnyEvent::log 5 => "unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@";
		1397	}
		1398	}
		1399
		1400	# check for already loaded models
448	unless ($MODEL) {	1401	unless ($MODEL) {
449	no strict 'refs';	1402	for (@REGISTRY, @models) {
450		1403	my ($package, $model) = @$_;
451	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	1404	if (${"$package\::VERSION"} > 0) {
452	my $model = "AnyEvent::Impl::$1";
453	if (eval "require $model") {	1405	if (eval "require $model") {
		1406	AnyEvent::log 7 => "autodetected model '$model', using it.";
454	$MODEL = $model;	1407	$MODEL = $model;
455	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	1408	last;
		1409	}
456	}	1410	}
457	}	1411	}
458		1412
459	# check for already loaded models
460	unless ($MODEL) {	1413	unless ($MODEL) {
		1414	# try to autoload a model
461	for (@REGISTRY, @models) {	1415	for (@REGISTRY, @models) {
462	my ($package, $model) = @$_;	1416	my ($package, $model, $autoload) = @$_;
		1417	if (
		1418	$autoload
		1419	and eval "require $package"
463	if (${"$package\::VERSION"} > 0) {	1420	and ${"$package\::VERSION"} > 0
464	if (eval "require $model") {	1421	and eval "require $model"
		1422	) {
		1423	AnyEvent::log 7 => "autoloaded model '$model', using it.";
465	$MODEL = $model;	1424	$MODEL = $model;
466	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;
467	last;	1425	last;
468	}
469	}	1426	}
470	}	1427	}
471		1428
472	unless ($MODEL) {	1429	$MODEL
473	# try to load a model	1430	or die "AnyEvent: backend autodetection failed - did you properly install AnyEvent?";
		1431	}
		1432	}
474		1433
475	for (@REGISTRY, @models) {	1434	# free memory only needed for probing
476	my ($package, $model) = @$_;	1435	undef @models;
477	if (eval "require $package"	1436	undef @REGISTRY;
478	and ${"$package\::VERSION"} > 0	1437
479	and eval "require $model") {	1438	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
480	$MODEL = $model;	1439
481	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;	1440	# now nuke some methods that are overridden by the backend.
		1441	# SUPER usage is not allowed in these.
		1442	for (qw(time signal child idle)) {
		1443	undef &{"AnyEvent::Base::$_"}
		1444	if defined &{"$MODEL\::$_"};
		1445	}
		1446
		1447	_isa_set;
		1448
		1449	# we're officially open!
		1450
		1451	if ($ENV{PERL_ANYEVENT_STRICT}) {
		1452	require AnyEvent::Strict;
		1453	}
		1454
		1455	if ($ENV{PERL_ANYEVENT_DEBUG_WRAP}) {
		1456	require AnyEvent::Debug;
		1457	AnyEvent::Debug::wrap ($ENV{PERL_ANYEVENT_DEBUG_WRAP});
		1458	}
		1459
		1460	if (length $ENV{PERL_ANYEVENT_DEBUG_SHELL}) {
		1461	require AnyEvent::Socket;
		1462	require AnyEvent::Debug;
		1463
		1464	my $shell = $ENV{PERL_ANYEVENT_DEBUG_SHELL};
		1465	$shell =~ s/\$\$/$$/g;
		1466
		1467	my ($host, $service) = AnyEvent::Socket::parse_hostport ($shell);
		1468	$AnyEvent::Debug::SHELL = AnyEvent::Debug::shell ($host, $service);
		1469	}
		1470
		1471	# now the anyevent environment is set up as the user told us to, so
		1472	# call the actual user code - post detects
		1473
		1474	(shift @post_detect)->() while @post_detect;
		1475	undef @post_detect;
		1476
		1477	*post_detect = sub(&) {
		1478	shift->();
		1479
		1480	undef
		1481	};
		1482
		1483	$MODEL
		1484	}
		1485
		1486	for my $name (@methods) {
		1487	*$name = sub {
		1488	detect;
		1489	# we use goto because
		1490	# a) it makes the thunk more transparent
		1491	# b) it allows us to delete the thunk later
		1492	goto &{ UNIVERSAL::can AnyEvent => "SUPER::$name" }
		1493	};
		1494	}
		1495
		1496	# utility function to dup a filehandle. this is used by many backends
		1497	# to support binding more than one watcher per filehandle (they usually
		1498	# allow only one watcher per fd, so we dup it to get a different one).
		1499	sub _dupfh($$;$$) {
		1500	my ($poll, $fh, $r, $w) = @_;
		1501
		1502	# cygwin requires the fh mode to be matching, unix doesn't
		1503	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1504
		1505	open my $fh2, $mode, $fh
		1506	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1507
		1508	# we assume CLOEXEC is already set by perl in all important cases
		1509
		1510	($fh2, $rw)
		1511	}
		1512
		1513	=head1 SIMPLIFIED AE API
		1514
		1515	Starting with version 5.0, AnyEvent officially supports a second, much
		1516	simpler, API that is designed to reduce the calling, typing and memory
		1517	overhead by using function call syntax and a fixed number of parameters.
		1518
		1519	See the L<AE> manpage for details.
		1520
		1521	=cut
		1522
		1523	package AE;
		1524
		1525	our $VERSION = $AnyEvent::VERSION;
		1526
		1527	sub _reset() {
		1528	eval q{
		1529	# fall back to the main API by default - backends and AnyEvent::Base
		1530	# implementations can overwrite these.
		1531
		1532	sub io($$$) {
		1533	AnyEvent->io (fh => $_[0], poll => $_[1] ? "w" : "r", cb => $_[2])
		1534	}
		1535
		1536	sub timer($$$) {
		1537	AnyEvent->timer (after => $_[0], interval => $_[1], cb => $_[2])
		1538	}
		1539
		1540	sub signal($$) {
		1541	AnyEvent->signal (signal => $_[0], cb => $_[1])
		1542	}
		1543
		1544	sub child($$) {
		1545	AnyEvent->child (pid => $_[0], cb => $_[1])
		1546	}
		1547
		1548	sub idle($) {
		1549	AnyEvent->idle (cb => $_[0]);
		1550	}
		1551
		1552	sub cv(;&) {
		1553	AnyEvent->condvar (@_ ? (cb => $_[0]) : ())
		1554	}
		1555
		1556	sub now() {
		1557	AnyEvent->now
		1558	}
		1559
		1560	sub now_update() {
		1561	AnyEvent->now_update
		1562	}
		1563
		1564	sub time() {
		1565	AnyEvent->time
		1566	}
		1567
		1568	*postpone = \&AnyEvent::postpone;
		1569	*log = \&AnyEvent::log;
		1570	};
		1571	die if $@;
		1572	}
		1573
		1574	BEGIN { _reset }
		1575
		1576	package AnyEvent::Base;
		1577
		1578	# default implementations for many methods
		1579
		1580	sub time {
		1581	eval q{ # poor man's autoloading {}
		1582	# probe for availability of Time::HiRes
		1583	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1584	*time = sub { Time::HiRes::time () };
		1585	*AE::time = \& Time::HiRes::time ;
		1586	*now = \&time;
		1587	AnyEvent::log 8 => "AnyEvent: using Time::HiRes for sub-second timing accuracy.";
		1588	# if (eval "use POSIX (); (POSIX::times())...
		1589	} else {
		1590	*time = sub { CORE::time };
		1591	*AE::time = sub (){ CORE::time };
		1592	*now = \&time;
		1593	AnyEvent::log 3 => "using built-in time(), WARNING, no sub-second resolution!";
		1594	}
		1595	};
		1596	die if $@;
		1597
		1598	&time
		1599	}
		1600
		1601	*now = \&time;
		1602	sub now_update { }
		1603
		1604	sub _poll {
		1605	Carp::croak "$AnyEvent::MODEL does not support blocking waits. Caught";
		1606	}
		1607
		1608	# default implementation for ->condvar
		1609	# in fact, the default should not be overwritten
		1610
		1611	sub condvar {
		1612	eval q{ # poor man's autoloading {}
		1613	*condvar = sub {
		1614	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
		1615	};
		1616
		1617	*AE::cv = sub (;&) {
		1618	bless { @_ ? (_ae_cb => shift) : () }, "AnyEvent::CondVar"
		1619	};
		1620	};
		1621	die if $@;
		1622
		1623	&condvar
		1624	}
		1625
		1626	# default implementation for ->signal
		1627
		1628	our $HAVE_ASYNC_INTERRUPT;
		1629
		1630	sub _have_async_interrupt() {
		1631	$HAVE_ASYNC_INTERRUPT = 1*(!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT}
		1632	&& eval "use Async::Interrupt 1.02 (); 1")
		1633	unless defined $HAVE_ASYNC_INTERRUPT;
		1634
		1635	$HAVE_ASYNC_INTERRUPT
		1636	}
		1637
		1638	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1639	our (%SIG_ASY, %SIG_ASY_W);
		1640	our ($SIG_COUNT, $SIG_TW);
		1641
		1642	# install a dummy wakeup watcher to reduce signal catching latency
		1643	# used by Impls
		1644	sub _sig_add() {
		1645	unless ($SIG_COUNT++) {
		1646	# try to align timer on a full-second boundary, if possible
		1647	my $NOW = AE::now;
		1648
		1649	$SIG_TW = AE::timer
		1650	$MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1651	$MAX_SIGNAL_LATENCY,
		1652	sub { } # just for the PERL_ASYNC_CHECK
		1653	;
		1654	}
		1655	}
		1656
		1657	sub _sig_del {
		1658	undef $SIG_TW
		1659	unless --$SIG_COUNT;
		1660	}
		1661
		1662	our $_sig_name_init; $_sig_name_init = sub {
		1663	eval q{ # poor man's autoloading {}
		1664	undef $_sig_name_init;
		1665
		1666	if (_have_async_interrupt) {
		1667	*sig2num = \&Async::Interrupt::sig2num;
		1668	*sig2name = \&Async::Interrupt::sig2name;
		1669	} else {
		1670	require Config;
		1671
		1672	my %signame2num;
		1673	@signame2num{ split ' ', $Config::Config{sig_name} }
		1674	= split ' ', $Config::Config{sig_num};
		1675
		1676	my @signum2name;
		1677	@signum2name[values %signame2num] = keys %signame2num;
		1678
		1679	*sig2num = sub($) {
		1680	$_[0] > 0 ? shift : $signame2num{+shift}
		1681	};
		1682	*sig2name = sub ($) {
		1683	$_[0] > 0 ? $signum2name[+shift] : shift
		1684	};
		1685	}
		1686	};
		1687	die if $@;
		1688	};
		1689
		1690	sub sig2num ($) { &$_sig_name_init; &sig2num }
		1691	sub sig2name($) { &$_sig_name_init; &sig2name }
		1692
		1693	sub signal {
		1694	eval q{ # poor man's autoloading {}
		1695	# probe for availability of Async::Interrupt
		1696	if (_have_async_interrupt) {
		1697	AnyEvent::log 8 => "using Async::Interrupt for race-free signal handling.";
		1698
		1699	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1700	$SIG_IO = AE::io $SIGPIPE_R->fileno, 0, \&_signal_exec;
		1701
		1702	} else {
		1703	AnyEvent::log 8 => "using emulated perl signal handling with latency timer.";
		1704
		1705	if (AnyEvent::WIN32) {
		1706	require AnyEvent::Util;
		1707
		1708	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1709	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R, 1) if $SIGPIPE_R;
		1710	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W, 1) if $SIGPIPE_W; # just in case
		1711	} else {
		1712	pipe $SIGPIPE_R, $SIGPIPE_W;
		1713	fcntl $SIGPIPE_R, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_R;
		1714	fcntl $SIGPIPE_W, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_W; # just in case
		1715
		1716	# not strictly required, as $^F is normally 2, but let's make sure...
		1717	fcntl $SIGPIPE_R, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1718	fcntl $SIGPIPE_W, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1719	}
		1720
		1721	$SIGPIPE_R
		1722	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1723
		1724	$SIG_IO = AE::io $SIGPIPE_R, 0, \&_signal_exec;
		1725	}
		1726
		1727	*signal = $HAVE_ASYNC_INTERRUPT
		1728	? sub {
		1729	my (undef, %arg) = @_;
		1730
		1731	# async::interrupt
		1732	my $signal = sig2num $arg{signal};
		1733	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1734
		1735	$SIG_ASY{$signal} ||= new Async::Interrupt
		1736	cb => sub { undef $SIG_EV{$signal} },
		1737	signal => $signal,
		1738	pipe => [$SIGPIPE_R->filenos],
		1739	pipe_autodrain => 0,
		1740	;
		1741
		1742	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1743	}
		1744	: sub {
		1745	my (undef, %arg) = @_;
		1746
		1747	# pure perl
		1748	my $signal = sig2name $arg{signal};
		1749	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1750
		1751	$SIG{$signal} ||= sub {
482	last;	1752	local $!;
		1753	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1754	undef $SIG_EV{$signal};
483	}	1755	};
		1756
		1757	# can't do signal processing without introducing races in pure perl,
		1758	# so limit the signal latency.
		1759	_sig_add;
		1760
		1761	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1762	}
		1763	;
		1764
		1765	*AnyEvent::Base::signal::DESTROY = sub {
		1766	my ($signal, $cb) = @{$_[0]};
		1767
		1768	_sig_del;
		1769
		1770	delete $SIG_CB{$signal}{$cb};
		1771
		1772	$HAVE_ASYNC_INTERRUPT
		1773	? delete $SIG_ASY{$signal}
		1774	: # delete doesn't work with older perls - they then
		1775	# print weird messages, or just unconditionally exit
		1776	# instead of getting the default action.
		1777	undef $SIG{$signal}
		1778	unless keys %{ $SIG_CB{$signal} };
		1779	};
		1780
		1781	*_signal_exec = sub {
		1782	$HAVE_ASYNC_INTERRUPT
		1783	? $SIGPIPE_R->drain
		1784	: sysread $SIGPIPE_R, (my $dummy), 9;
		1785
		1786	while (%SIG_EV) {
		1787	for (keys %SIG_EV) {
		1788	delete $SIG_EV{$_};
		1789	&$_ for values %{ $SIG_CB{$_} || {} };
484	}	1790	}
485
486	$MODEL
487	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.";
488	}	1791	}
489	}	1792	};
490
491	unshift @ISA, $MODEL;
492	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
493	}
494
495	$MODEL
496	}
497
498	sub AUTOLOAD {
499	(my $func = $AUTOLOAD) =~ s/.*://;
500
501	$method{$func}
502	or croak "$func: not a valid method for AnyEvent objects";
503
504	detect unless $MODEL;
505
506	my $class = shift;
507	$class->$func (@_);
508	}
509
510	package AnyEvent::Base;
511
512	# default implementation for ->condvar, ->wait, ->broadcast
513
514	sub condvar {
515	bless \my $flag, "AnyEvent::Base::CondVar"
516	}
517
518	sub AnyEvent::Base::CondVar::broadcast {
519	${$_[0]}++;
520	}
521
522	sub AnyEvent::Base::CondVar::wait {
523	AnyEvent->one_event while !${$_[0]};
524	}
525
526	# default implementation for ->signal
527
528	our %SIG_CB;
529
530	sub signal {
531	my (undef, %arg) = @_;
532
533	my $signal = uc $arg{signal}
534	or Carp::croak "required option 'signal' is missing";
535
536	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
537	$SIG{$signal} ||= sub {
538	$_->() for values %{ $SIG_CB{$signal} || {} };
539	};	1793	};
		1794	die if $@;
540		1795
541	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1796	&signal
542	}
543
544	sub AnyEvent::Base::Signal::DESTROY {
545	my ($signal, $cb) = @{$_[0]};
546
547	delete $SIG_CB{$signal}{$cb};
548
549	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };
550	}	1797	}
551		1798
552	# default implementation for ->child	1799	# default implementation for ->child
553		1800
554	our %PID_CB;	1801	our %PID_CB;
555	our $CHLD_W;	1802	our $CHLD_W;
556	our $CHLD_DELAY_W;	1803	our $CHLD_DELAY_W;
557	our $PID_IDLE;
558	our $WNOHANG;
559		1804
560	sub _child_wait {	1805	# used by many Impl's
561	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1806	sub _emit_childstatus($$) {
		1807	my (undef, $rpid, $rstatus) = @_;
		1808
		1809	$_->($rpid, $rstatus)
562	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1810	for values %{ $PID_CB{$rpid} || {} },
563	(values %{ $PID_CB{0} || {} });	1811	values %{ $PID_CB{0} || {} };
		1812	}
		1813
		1814	sub child {
		1815	eval q{ # poor man's autoloading {}
		1816	*_sigchld = sub {
		1817	my $pid;
		1818
		1819	AnyEvent->_emit_childstatus ($pid, $?)
		1820	while ($pid = waitpid -1, WNOHANG) > 0;
		1821	};
		1822
		1823	*child = sub {
		1824	my (undef, %arg) = @_;
		1825
		1826	my $pid = $arg{pid};
		1827	my $cb = $arg{cb};
		1828
		1829	$PID_CB{$pid}{$cb+0} = $cb;
		1830
		1831	unless ($CHLD_W) {
		1832	$CHLD_W = AE::signal CHLD => \&_sigchld;
		1833	# child could be a zombie already, so make at least one round
		1834	&_sigchld;
		1835	}
		1836
		1837	bless [$pid, $cb+0], "AnyEvent::Base::child"
		1838	};
		1839
		1840	*AnyEvent::Base::child::DESTROY = sub {
		1841	my ($pid, $icb) = @{$_[0]};
		1842
		1843	delete $PID_CB{$pid}{$icb};
		1844	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
		1845
		1846	undef $CHLD_W unless keys %PID_CB;
		1847	};
		1848	};
		1849	die if $@;
		1850
		1851	&child
		1852	}
		1853
		1854	# idle emulation is done by simply using a timer, regardless
		1855	# of whether the process is idle or not, and not letting
		1856	# the callback use more than 50% of the time.
		1857	sub idle {
		1858	eval q{ # poor man's autoloading {}
		1859	*idle = sub {
		1860	my (undef, %arg) = @_;
		1861
		1862	my ($cb, $w, $rcb) = $arg{cb};
		1863
		1864	$rcb = sub {
		1865	if ($cb) {
		1866	$w = AE::time;
		1867	&$cb;
		1868	$w = AE::time - $w;
		1869
		1870	# never use more then 50% of the time for the idle watcher,
		1871	# within some limits
		1872	$w = 0.0001 if $w < 0.0001;
		1873	$w = 5 if $w > 5;
		1874
		1875	$w = AE::timer $w, 0, $rcb;
		1876	} else {
		1877	# clean up...
		1878	undef $w;
		1879	undef $rcb;
		1880	}
		1881	};
		1882
		1883	$w = AE::timer 0.05, 0, $rcb;
		1884
		1885	bless \\$cb, "AnyEvent::Base::idle"
		1886	};
		1887
		1888	*AnyEvent::Base::idle::DESTROY = sub {
		1889	undef $${$_[0]};
		1890	};
		1891	};
		1892	die if $@;
		1893
		1894	&idle
		1895	}
		1896
		1897	package AnyEvent::CondVar;
		1898
		1899	our @ISA = AnyEvent::CondVar::Base::;
		1900
		1901	# only to be used for subclassing
		1902	sub new {
		1903	my $class = shift;
		1904	bless AnyEvent->condvar (@_), $class
		1905	}
		1906
		1907	package AnyEvent::CondVar::Base;
		1908
		1909	#use overload
		1910	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1911	# fallback => 1;
		1912
		1913	# save 300+ kilobytes by dirtily hardcoding overloading
		1914	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1915	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1916	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1917	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1918
		1919	our $WAITING;
		1920
		1921	sub _send {
		1922	# nop
		1923	}
		1924
		1925	sub _wait {
		1926	AnyEvent->_poll until $_[0]{_ae_sent};
		1927	}
		1928
		1929	sub send {
		1930	my $cv = shift;
		1931	$cv->{_ae_sent} = [@_];
		1932	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1933	$cv->_send;
		1934	}
		1935
		1936	sub croak {
		1937	$_[0]{_ae_croak} = $_[1];
		1938	$_[0]->send;
		1939	}
		1940
		1941	sub ready {
		1942	$_[0]{_ae_sent}
		1943	}
		1944
		1945	sub recv {
		1946	unless ($_[0]{_ae_sent}) {
		1947	$WAITING
		1948	and Carp::croak "AnyEvent::CondVar: recursive blocking wait attempted";
		1949
		1950	local $WAITING = 1;
		1951	$_[0]->_wait;
564	}	1952	}
565		1953
566	undef $PID_IDLE;	1954	$_[0]{_ae_croak}
567	}	1955	and Carp::croak $_[0]{_ae_croak};
568		1956
569	sub _sigchld {	1957	wantarray
570	# make sure we deliver these changes "synchronous" with the event loop.	1958	? @{ $_[0]{_ae_sent} }
571	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {	1959	: $_[0]{_ae_sent}[0]
572	undef $CHLD_DELAY_W;
573	&_child_wait;
574	});
575	}	1960	}
576		1961
577	sub child {	1962	sub cb {
578	my (undef, %arg) = @_;	1963	my $cv = shift;
579		1964
580	defined (my $pid = $arg{pid} + 0)	1965	@_
581	or Carp::croak "required option 'pid' is missing";	1966	and $cv->{_ae_cb} = shift
		1967	and $cv->{_ae_sent}
		1968	and (delete $cv->{_ae_cb})->($cv);
582		1969
583	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1970	$cv->{_ae_cb}
584
585	unless ($WNOHANG) {
586	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;
587	}
588
589	unless ($CHLD_W) {
590	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
591	# child could be a zombie already, so make at least one round
592	&_sigchld;
593	}
594
595	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"
596	}	1971	}
597		1972
598	sub AnyEvent::Base::Child::DESTROY {	1973	sub begin {
599	my ($pid, $cb) = @{$_[0]};	1974	++$_[0]{_ae_counter};
600		1975	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
601	delete $PID_CB{$pid}{$cb};
602	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
603
604	undef $CHLD_W unless keys %PID_CB;
605	}	1976	}
		1977
		1978	sub end {
		1979	return if --$_[0]{_ae_counter};
		1980	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		1981	}
		1982
		1983	# undocumented/compatibility with pre-3.4
		1984	*broadcast = \&send;
		1985	*wait = \&recv;
		1986
		1987	=head1 ERROR AND EXCEPTION HANDLING
		1988
		1989	In general, AnyEvent does not do any error handling - it relies on the
		1990	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1991	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1992	checking of all AnyEvent methods, however, which is highly useful during
		1993	development.
		1994
		1995	As for exception handling (i.e. runtime errors and exceptions thrown while
		1996	executing a callback), this is not only highly event-loop specific, but
		1997	also not in any way wrapped by this module, as this is the job of the main
		1998	program.
		1999
		2000	The pure perl event loop simply re-throws the exception (usually
		2001	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		2002	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		2003	so on.
		2004
		2005	=head1 ENVIRONMENT VARIABLES
		2006
		2007	AnyEvent supports a number of environment variables that tune the
		2008	runtime behaviour. They are usually evaluated when AnyEvent is
		2009	loaded, initialised, or a submodule that uses them is loaded. Many of
		2010	them also cause AnyEvent to load additional modules - for example,
		2011	C<PERL_ANYEVENT_DEBUG_WRAP> causes the L<AnyEvent::Debug> module to be
		2012	loaded.
		2013
		2014	All the environment variables documented here start with
		2015	C<PERL_ANYEVENT_>, which is what AnyEvent considers its own
		2016	namespace. Other modules are encouraged (but by no means required) to use
		2017	C<PERL_ANYEVENT_SUBMODULE> if they have registered the AnyEvent::Submodule
		2018	namespace on CPAN, for any submodule. For example, L<AnyEvent::HTTP> could
		2019	be expected to use C<PERL_ANYEVENT_HTTP_PROXY> (it should not access env
		2020	variables starting with C<AE_>, see below).
		2021
		2022	All variables can also be set via the C<AE_> prefix, that is, instead
		2023	of setting C<PERL_ANYEVENT_VERBOSE> you can also set C<AE_VERBOSE>. In
		2024	case there is a clash btween anyevent and another program that uses
		2025	C<AE_something> you can set the corresponding C<PERL_ANYEVENT_something>
		2026	variable to the empty string, as those variables take precedence.
		2027
		2028	When AnyEvent is first loaded, it copies all C<AE_xxx> env variables
		2029	to their C<PERL_ANYEVENT_xxx> counterpart unless that variable already
		2030	exists. If taint mode is on, then AnyEvent will remove I<all> environment
		2031	variables starting with C<PERL_ANYEVENT_> from C<%ENV> (or replace them
		2032	with C<undef> or the empty string, if the corresaponding C<AE_> variable
		2033	is set).
		2034
		2035	The exact algorithm is currently:
		2036
		2037	1. if taint mode enabled, delete all PERL_ANYEVENT_xyz variables from %ENV
		2038	2. copy over AE_xyz to PERL_ANYEVENT_xyz unless the latter alraedy exists
		2039	3. if taint mode enabled, set all PERL_ANYEVENT_xyz variables to undef.
		2040
		2041	This ensures that child processes will not see the C<AE_> variables.
		2042
		2043	The following environment variables are currently known to AnyEvent:
		2044
		2045	=over 4
		2046
		2047	=item C<PERL_ANYEVENT_VERBOSE>
		2048
		2049	By default, AnyEvent will only log messages with loglevel C<3>
		2050	(C<critical>) or higher (see L<AnyEvent::Log>). You can set this
		2051	environment variable to a numerical loglevel to make AnyEvent more (or
		2052	less) talkative.
		2053
		2054	If you want to do more than just set the global logging level
		2055	you should have a look at C<PERL_ANYEVENT_LOG>, which allows much more
		2056	complex specifications.
		2057
		2058	When set to C<0> (C<off>), then no messages whatsoever will be logged with
		2059	the default logging settings.
		2060
		2061	When set to C<5> or higher (C<warn>), causes AnyEvent to warn about
		2062	unexpected conditions, such as not being able to load the event model
		2063	specified by C<PERL_ANYEVENT_MODEL>, or a guard callback throwing an
		2064	exception - this is the minimum recommended level.
		2065
		2066	When set to C<7> or higher (info), cause AnyEvent to report which event model it
		2067	chooses.
		2068
		2069	When set to C<8> or higher (debug), then AnyEvent will report extra information on
		2070	which optional modules it loads and how it implements certain features.
		2071
		2072	=item C<PERL_ANYEVENT_LOG>
		2073
		2074	Accepts rather complex logging specifications. For example, you could log
		2075	all C<debug> messages of some module to stderr, warnings and above to
		2076	stderr, and errors and above to syslog, with:
		2077
		2078	PERL_ANYEVENT_LOG=Some::Module=debug,+log:filter=warn,+%syslog:%syslog=error,syslog
		2079
		2080	For the rather extensive details, see L<AnyEvent::Log>.
		2081
		2082	This variable is evaluated when AnyEvent (or L<AnyEvent::Log>) is loaded,
		2083	so will take effect even before AnyEvent has initialised itself.
		2084
		2085	Note that specifying this environment variable causes the L<AnyEvent::Log>
		2086	module to be loaded, while C<PERL_ANYEVENT_VERBOSE> does not, so only
		2087	using the latter saves a few hundred kB of memory until the first message
		2088	is being logged.
		2089
		2090	=item C<PERL_ANYEVENT_STRICT>
		2091
		2092	AnyEvent does not do much argument checking by default, as thorough
		2093	argument checking is very costly. Setting this variable to a true value
		2094	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		2095	check the arguments passed to most method calls. If it finds any problems,
		2096	it will croak.
		2097
		2098	In other words, enables "strict" mode.
		2099
		2100	Unlike C<use strict> (or its modern cousin, C<< use L<common::sense>
		2101	>>, it is definitely recommended to keep it off in production. Keeping
		2102	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		2103	can be very useful, however.
		2104
		2105	=item C<PERL_ANYEVENT_DEBUG_SHELL>
		2106
		2107	If this env variable is set, then its contents will be interpreted by
		2108	C<AnyEvent::Socket::parse_hostport> (after replacing every occurance of
		2109	C<$$> by the process pid) and an C<AnyEvent::Debug::shell> is bound on
		2110	that port. The shell object is saved in C<$AnyEvent::Debug::SHELL>.
		2111
		2112	This happens when the first watcher is created.
		2113
		2114	For example, to bind a debug shell on a unix domain socket in
		2115	F<< /tmp/debug<pid>.sock >>, you could use this:
		2116
		2117	PERL_ANYEVENT_DEBUG_SHELL=/tmp/debug\$\$.sock perlprog
		2118
		2119	Note that creating sockets in F</tmp> is very unsafe on multiuser
		2120	systems.
		2121
		2122	=item C<PERL_ANYEVENT_DEBUG_WRAP>
		2123
		2124	Can be set to C<0>, C<1> or C<2> and enables wrapping of all watchers for
		2125	debugging purposes. See C<AnyEvent::Debug::wrap> for details.
		2126
		2127	=item C<PERL_ANYEVENT_MODEL>
		2128
		2129	This can be used to specify the event model to be used by AnyEvent, before
		2130	auto detection and -probing kicks in.
		2131
		2132	It normally is a string consisting entirely of ASCII letters (e.g. C<EV>
		2133	or C<IOAsync>). The string C<AnyEvent::Impl::> gets prepended and the
		2134	resulting module name is loaded and - if the load was successful - used as
		2135	event model backend. If it fails to load then AnyEvent will proceed with
		2136	auto detection and -probing.
		2137
		2138	If the string ends with C<::> instead (e.g. C<AnyEvent::Impl::EV::>) then
		2139	nothing gets prepended and the module name is used as-is (hint: C<::> at
		2140	the end of a string designates a module name and quotes it appropriately).
		2141
		2142	For example, to force the pure perl model (L<AnyEvent::Loop::Perl>) you
		2143	could start your program like this:
		2144
		2145	PERL_ANYEVENT_MODEL=Perl perl ...
		2146
		2147	=item C<PERL_ANYEVENT_PROTOCOLS>
		2148
		2149	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		2150	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		2151	of auto probing).
		2152
		2153	Must be set to a comma-separated list of protocols or address families,
		2154	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		2155	used, and preference will be given to protocols mentioned earlier in the
		2156	list.
		2157
		2158	This variable can effectively be used for denial-of-service attacks
		2159	against local programs (e.g. when setuid), although the impact is likely
		2160	small, as the program has to handle conenction and other failures anyways.
		2161
		2162	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		2163	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		2164	- only support IPv4, never try to resolve or contact IPv6
		2165	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		2166	IPv6, but prefer IPv6 over IPv4.
		2167
		2168	=item C<PERL_ANYEVENT_HOSTS>
		2169
		2170	This variable, if specified, overrides the F</etc/hosts> file used by
		2171	L<AnyEvent::Socket>C<::resolve_sockaddr>, i.e. hosts aliases will be read
		2172	from that file instead.
		2173
		2174	=item C<PERL_ANYEVENT_EDNS0>
		2175
		2176	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension for
		2177	DNS. This extension is generally useful to reduce DNS traffic, especially
		2178	when DNSSEC is involved, but some (broken) firewalls drop such DNS
		2179	packets, which is why it is off by default.
		2180
		2181	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		2182	EDNS0 in its DNS requests.
		2183
		2184	=item C<PERL_ANYEVENT_MAX_FORKS>
		2185
		2186	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		2187	will create in parallel.
		2188
		2189	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		2190
		2191	The default value for the C<max_outstanding> parameter for the default DNS
		2192	resolver - this is the maximum number of parallel DNS requests that are
		2193	sent to the DNS server.
		2194
		2195	=item C<PERL_ANYEVENT_RESOLV_CONF>
		2196
		2197	The absolute path to a F<resolv.conf>-style file to use instead of
		2198	F</etc/resolv.conf> (or the OS-specific configuration) in the default
		2199	resolver, or the empty string to select the default configuration.
		2200
		2201	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		2202
		2203	When neither C<ca_file> nor C<ca_path> was specified during
		2204	L<AnyEvent::TLS> context creation, and either of these environment
		2205	variables are nonempty, they will be used to specify CA certificate
		2206	locations instead of a system-dependent default.
		2207
		2208	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		2209
		2210	When these are set to C<1>, then the respective modules are not
		2211	loaded. Mostly good for testing AnyEvent itself.
		2212
		2213	=back
606		2214
607	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	2215	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
608		2216
609	This is an advanced topic that you do not normally need to use AnyEvent in	2217	This is an advanced topic that you do not normally need to use AnyEvent in
610	a module. This section is only of use to event loop authors who want to	2218	a module. This section is only of use to event loop authors who want to
…		…
645	I<rxvt-unicode> also cheats a bit by not providing blocking access to	2253	I<rxvt-unicode> also cheats a bit by not providing blocking access to
646	condition variables: code blocking while waiting for a condition will	2254	condition variables: code blocking while waiting for a condition will
647	C<die>. This still works with most modules/usages, and blocking calls must	2255	C<die>. This still works with most modules/usages, and blocking calls must
648	not be done in an interactive application, so it makes sense.	2256	not be done in an interactive application, so it makes sense.
649		2257
650	=head1 ENVIRONMENT VARIABLES
651
652	The following environment variables are used by this module:
653
654	=over 4
655
656	=item C<PERL_ANYEVENT_VERBOSE>
657
658	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
659	model it chooses.
660
661	=item C<PERL_ANYEVENT_MODEL>
662
663	This can be used to specify the event model to be used by AnyEvent, before
664	autodetection and -probing kicks in. It must be a string consisting
665	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
666	and the resulting module name is loaded and if the load was successful,
667	used as event model. If it fails to load AnyEvent will proceed with
668	autodetection and -probing.
669
670	This functionality might change in future versions.
671
672	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
673	could start your program like this:
674
675	PERL_ANYEVENT_MODEL=Perl perl ...
676
677	=back
678
679	=head1 EXAMPLE PROGRAM	2258	=head1 EXAMPLE PROGRAM
680		2259
681	The following program uses an IO watcher to read data from STDIN, a timer	2260	The following program uses an I/O watcher to read data from STDIN, a timer
682	to display a message once per second, and a condition variable to quit the	2261	to display a message once per second, and a condition variable to quit the
683	program when the user enters quit:	2262	program when the user enters quit:
684		2263
685	use AnyEvent;	2264	use AnyEvent;
686		2265
…		…
691	poll => 'r',	2270	poll => 'r',
692	cb => sub {	2271	cb => sub {
693	warn "io event <$_[0]>\n"; # will always output <r>	2272	warn "io event <$_[0]>\n"; # will always output <r>
694	chomp (my $input = <STDIN>); # read a line	2273	chomp (my $input = <STDIN>); # read a line
695	warn "read: $input\n"; # output what has been read	2274	warn "read: $input\n"; # output what has been read
696	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	2275	$cv->send if $input =~ /^q/i; # quit program if /^q/i
697	},	2276	},
698	);	2277	);
699		2278
700	my $time_watcher; # can only be used once
701
702	sub new_timer {
703	$timer = AnyEvent->timer (after => 1, cb => sub {	2279	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
704	warn "timeout\n"; # print 'timeout' about every second	2280	warn "timeout\n"; # print 'timeout' at most every second
705	&new_timer; # and restart the time
706	});	2281	});
707	}
708		2282
709	new_timer; # create first timer
710
711	$cv->wait; # wait until user enters /^q/i	2283	$cv->recv; # wait until user enters /^q/i
712		2284
713	=head1 REAL-WORLD EXAMPLE	2285	=head1 REAL-WORLD EXAMPLE
714		2286
715	Consider the L<Net::FCP> module. It features (among others) the following	2287	Consider the L<Net::FCP> module. It features (among others) the following
716	API calls, which are to freenet what HTTP GET requests are to http:	2288	API calls, which are to freenet what HTTP GET requests are to http:
…		…
766	syswrite $txn->{fh}, $txn->{request}	2338	syswrite $txn->{fh}, $txn->{request}
767	or die "connection or write error";	2339	or die "connection or write error";
768	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	2340	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
769		2341
770	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	2342	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
771	result and signals any possible waiters that the request ahs finished:	2343	result and signals any possible waiters that the request has finished:
772		2344
773	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	2345	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
774		2346
775	if (end-of-file or data complete) {	2347	if (end-of-file or data complete) {
776	$txn->{result} = $txn->{buf};	2348	$txn->{result} = $txn->{buf};
777	$txn->{finished}->broadcast;	2349	$txn->{finished}->send;
778	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	2350	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
779	}	2351	}
780		2352
781	The C<result> method, finally, just waits for the finished signal (if the	2353	The C<result> method, finally, just waits for the finished signal (if the
782	request was already finished, it doesn't wait, of course, and returns the	2354	request was already finished, it doesn't wait, of course, and returns the
783	data:	2355	data:
784		2356
785	$txn->{finished}->wait;	2357	$txn->{finished}->recv;
786	return $txn->{result};	2358	return $txn->{result};
787		2359
788	The actual code goes further and collects all errors (C<die>s, exceptions)	2360	The actual code goes further and collects all errors (C<die>s, exceptions)
789	that occured during request processing. The C<result> method detects	2361	that occurred during request processing. The C<result> method detects
790	whether an exception as thrown (it is stored inside the $txn object)	2362	whether an exception as thrown (it is stored inside the $txn object)
791	and just throws the exception, which means connection errors and other	2363	and just throws the exception, which means connection errors and other
792	problems get reported tot he code that tries to use the result, not in a	2364	problems get reported to the code that tries to use the result, not in a
793	random callback.	2365	random callback.
794		2366
795	All of this enables the following usage styles:	2367	All of this enables the following usage styles:
796		2368
797	1. Blocking:	2369	1. Blocking:
…		…
825		2397
826	my $quit = AnyEvent->condvar;	2398	my $quit = AnyEvent->condvar;
827		2399
828	$fcp->txn_client_get ($url)->cb (sub {	2400	$fcp->txn_client_get ($url)->cb (sub {
829	...	2401	...
830	$quit->broadcast;	2402	$quit->send;
831	});	2403	});
832		2404
833	$quit->wait;	2405	$quit->recv;
		2406
		2407
		2408	=head1 BENCHMARKS
		2409
		2410	To give you an idea of the performance and overheads that AnyEvent adds
		2411	over the event loops themselves and to give you an impression of the speed
		2412	of various event loops I prepared some benchmarks.
		2413
		2414	=head2 BENCHMARKING ANYEVENT OVERHEAD
		2415
		2416	Here is a benchmark of various supported event models used natively and
		2417	through AnyEvent. The benchmark creates a lot of timers (with a zero
		2418	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
		2419	which it is), lets them fire exactly once and destroys them again.
		2420
		2421	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
		2422	distribution. It uses the L<AE> interface, which makes a real difference
		2423	for the EV and Perl backends only.
		2424
		2425	=head3 Explanation of the columns
		2426
		2427	I<watcher> is the number of event watchers created/destroyed. Since
		2428	different event models feature vastly different performances, each event
		2429	loop was given a number of watchers so that overall runtime is acceptable
		2430	and similar between tested event loop (and keep them from crashing): Glib
		2431	would probably take thousands of years if asked to process the same number
		2432	of watchers as EV in this benchmark.
		2433
		2434	I<bytes> is the number of bytes (as measured by the resident set size,
		2435	RSS) consumed by each watcher. This method of measuring captures both C
		2436	and Perl-based overheads.
		2437
		2438	I<create> is the time, in microseconds (millionths of seconds), that it
		2439	takes to create a single watcher. The callback is a closure shared between
		2440	all watchers, to avoid adding memory overhead. That means closure creation
		2441	and memory usage is not included in the figures.
		2442
		2443	I<invoke> is the time, in microseconds, used to invoke a simple
		2444	callback. The callback simply counts down a Perl variable and after it was
		2445	invoked "watcher" times, it would C<< ->send >> a condvar once to
		2446	signal the end of this phase.
		2447
		2448	I<destroy> is the time, in microseconds, that it takes to destroy a single
		2449	watcher.
		2450
		2451	=head3 Results
		2452
		2453	name watchers bytes create invoke destroy comment
		2454	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
		2455	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
		2456	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
		2457	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
		2458	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
		2459	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
		2460	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
		2461	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
		2462	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
		2463	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
		2464	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
		2465	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
		2466
		2467	=head3 Discussion
		2468
		2469	The benchmark does I<not> measure scalability of the event loop very
		2470	well. For example, a select-based event loop (such as the pure perl one)
		2471	can never compete with an event loop that uses epoll when the number of
		2472	file descriptors grows high. In this benchmark, all events become ready at
		2473	the same time, so select/poll-based implementations get an unnatural speed
		2474	boost.
		2475
		2476	Also, note that the number of watchers usually has a nonlinear effect on
		2477	overall speed, that is, creating twice as many watchers doesn't take twice
		2478	the time - usually it takes longer. This puts event loops tested with a
		2479	higher number of watchers at a disadvantage.
		2480
		2481	To put the range of results into perspective, consider that on the
		2482	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		2483	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		2484	cycles with POE.
		2485
		2486	C<EV> is the sole leader regarding speed and memory use, which are both
		2487	maximal/minimal, respectively. When using the L<AE> API there is zero
		2488	overhead (when going through the AnyEvent API create is about 5-6 times
		2489	slower, with other times being equal, so still uses far less memory than
		2490	any other event loop and is still faster than Event natively).
		2491
		2492	The pure perl implementation is hit in a few sweet spots (both the
		2493	constant timeout and the use of a single fd hit optimisations in the perl
		2494	interpreter and the backend itself). Nevertheless this shows that it
		2495	adds very little overhead in itself. Like any select-based backend its
		2496	performance becomes really bad with lots of file descriptors (and few of
		2497	them active), of course, but this was not subject of this benchmark.
		2498
		2499	The C<Event> module has a relatively high setup and callback invocation
		2500	cost, but overall scores in on the third place.
		2501
		2502	C<IO::Async> performs admirably well, about on par with C<Event>, even
		2503	when using its pure perl backend.
		2504
		2505	C<Glib>'s memory usage is quite a bit higher, but it features a
		2506	faster callback invocation and overall ends up in the same class as
		2507	C<Event>. However, Glib scales extremely badly, doubling the number of
		2508	watchers increases the processing time by more than a factor of four,
		2509	making it completely unusable when using larger numbers of watchers
		2510	(note that only a single file descriptor was used in the benchmark, so
		2511	inefficiencies of C<poll> do not account for this).
		2512
		2513	The C<Tk> adaptor works relatively well. The fact that it crashes with
		2514	more than 2000 watchers is a big setback, however, as correctness takes
		2515	precedence over speed. Nevertheless, its performance is surprising, as the
		2516	file descriptor is dup()ed for each watcher. This shows that the dup()
		2517	employed by some adaptors is not a big performance issue (it does incur a
		2518	hidden memory cost inside the kernel which is not reflected in the figures
		2519	above).
		2520
		2521	C<POE>, regardless of underlying event loop (whether using its pure perl
		2522	select-based backend or the Event module, the POE-EV backend couldn't
		2523	be tested because it wasn't working) shows abysmal performance and
		2524	memory usage with AnyEvent: Watchers use almost 30 times as much memory
		2525	as EV watchers, and 10 times as much memory as Event (the high memory
		2526	requirements are caused by requiring a session for each watcher). Watcher
		2527	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		2528	implementation.
		2529
		2530	The design of the POE adaptor class in AnyEvent can not really account
		2531	for the performance issues, though, as session creation overhead is
		2532	small compared to execution of the state machine, which is coded pretty
		2533	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		2534	using multiple sessions is not a good approach, especially regarding
		2535	memory usage, even the author of POE could not come up with a faster
		2536	design).
		2537
		2538	=head3 Summary
		2539
		2540	=over 4
		2541
		2542	=item * Using EV through AnyEvent is faster than any other event loop
		2543	(even when used without AnyEvent), but most event loops have acceptable
		2544	performance with or without AnyEvent.
		2545
		2546	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
		2547	the actual event loop, only with extremely fast event loops such as EV
		2548	does AnyEvent add significant overhead.
		2549
		2550	=item * You should avoid POE like the plague if you want performance or
		2551	reasonable memory usage.
		2552
		2553	=back
		2554
		2555	=head2 BENCHMARKING THE LARGE SERVER CASE
		2556
		2557	This benchmark actually benchmarks the event loop itself. It works by
		2558	creating a number of "servers": each server consists of a socket pair, a
		2559	timeout watcher that gets reset on activity (but never fires), and an I/O
		2560	watcher waiting for input on one side of the socket. Each time the socket
		2561	watcher reads a byte it will write that byte to a random other "server".
		2562
		2563	The effect is that there will be a lot of I/O watchers, only part of which
		2564	are active at any one point (so there is a constant number of active
		2565	fds for each loop iteration, but which fds these are is random). The
		2566	timeout is reset each time something is read because that reflects how
		2567	most timeouts work (and puts extra pressure on the event loops).
		2568
		2569	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
		2570	(1%) are active. This mirrors the activity of large servers with many
		2571	connections, most of which are idle at any one point in time.
		2572
		2573	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		2574	distribution. It uses the L<AE> interface, which makes a real difference
		2575	for the EV and Perl backends only.
		2576
		2577	=head3 Explanation of the columns
		2578
		2579	I<sockets> is the number of sockets, and twice the number of "servers" (as
		2580	each server has a read and write socket end).
		2581
		2582	I<create> is the time it takes to create a socket pair (which is
		2583	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		2584
		2585	I<request>, the most important value, is the time it takes to handle a
		2586	single "request", that is, reading the token from the pipe and forwarding
		2587	it to another server. This includes deleting the old timeout and creating
		2588	a new one that moves the timeout into the future.
		2589
		2590	=head3 Results
		2591
		2592	name sockets create request
		2593	EV 20000 62.66 7.99
		2594	Perl 20000 68.32 32.64
		2595	IOAsync 20000 174.06 101.15 epoll
		2596	IOAsync 20000 174.67 610.84 poll
		2597	Event 20000 202.69 242.91
		2598	Glib 20000 557.01 1689.52
		2599	POE 20000 341.54 12086.32 uses POE::Loop::Event
		2600
		2601	=head3 Discussion
		2602
		2603	This benchmark I<does> measure scalability and overall performance of the
		2604	particular event loop.
		2605
		2606	EV is again fastest. Since it is using epoll on my system, the setup time
		2607	is relatively high, though.
		2608
		2609	Perl surprisingly comes second. It is much faster than the C-based event
		2610	loops Event and Glib.
		2611
		2612	IO::Async performs very well when using its epoll backend, and still quite
		2613	good compared to Glib when using its pure perl backend.
		2614
		2615	Event suffers from high setup time as well (look at its code and you will
		2616	understand why). Callback invocation also has a high overhead compared to
		2617	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		2618	uses select or poll in basically all documented configurations.
		2619
		2620	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		2621	clearly fails to perform with many filehandles or in busy servers.
		2622
		2623	POE is still completely out of the picture, taking over 1000 times as long
		2624	as EV, and over 100 times as long as the Perl implementation, even though
		2625	it uses a C-based event loop in this case.
		2626
		2627	=head3 Summary
		2628
		2629	=over 4
		2630
		2631	=item * The pure perl implementation performs extremely well.
		2632
		2633	=item * Avoid Glib or POE in large projects where performance matters.
		2634
		2635	=back
		2636
		2637	=head2 BENCHMARKING SMALL SERVERS
		2638
		2639	While event loops should scale (and select-based ones do not...) even to
		2640	large servers, most programs we (or I :) actually write have only a few
		2641	I/O watchers.
		2642
		2643	In this benchmark, I use the same benchmark program as in the large server
		2644	case, but it uses only eight "servers", of which three are active at any
		2645	one time. This should reflect performance for a small server relatively
		2646	well.
		2647
		2648	The columns are identical to the previous table.
		2649
		2650	=head3 Results
		2651
		2652	name sockets create request
		2653	EV 16 20.00 6.54
		2654	Perl 16 25.75 12.62
		2655	Event 16 81.27 35.86
		2656	Glib 16 32.63 15.48
		2657	POE 16 261.87 276.28 uses POE::Loop::Event
		2658
		2659	=head3 Discussion
		2660
		2661	The benchmark tries to test the performance of a typical small
		2662	server. While knowing how various event loops perform is interesting, keep
		2663	in mind that their overhead in this case is usually not as important, due
		2664	to the small absolute number of watchers (that is, you need efficiency and
		2665	speed most when you have lots of watchers, not when you only have a few of
		2666	them).
		2667
		2668	EV is again fastest.
		2669
		2670	Perl again comes second. It is noticeably faster than the C-based event
		2671	loops Event and Glib, although the difference is too small to really
		2672	matter.
		2673
		2674	POE also performs much better in this case, but is is still far behind the
		2675	others.
		2676
		2677	=head3 Summary
		2678
		2679	=over 4
		2680
		2681	=item * C-based event loops perform very well with small number of
		2682	watchers, as the management overhead dominates.
		2683
		2684	=back
		2685
		2686	=head2 THE IO::Lambda BENCHMARK
		2687
		2688	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2689	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2690	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2691	shouldn't come as a surprise to anybody). As such, the benchmark is
		2692	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2693	very optimal. But how would AnyEvent compare when used without the extra
		2694	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2695
		2696	The benchmark itself creates an echo-server, and then, for 500 times,
		2697	connects to the echo server, sends a line, waits for the reply, and then
		2698	creates the next connection. This is a rather bad benchmark, as it doesn't
		2699	test the efficiency of the framework or much non-blocking I/O, but it is a
		2700	benchmark nevertheless.
		2701
		2702	name runtime
		2703	Lambda/select 0.330 sec
		2704	+ optimized 0.122 sec
		2705	Lambda/AnyEvent 0.327 sec
		2706	+ optimized 0.138 sec
		2707	Raw sockets/select 0.077 sec
		2708	POE/select, components 0.662 sec
		2709	POE/select, raw sockets 0.226 sec
		2710	POE/select, optimized 0.404 sec
		2711
		2712	AnyEvent/select/nb 0.085 sec
		2713	AnyEvent/EV/nb 0.068 sec
		2714	+state machine 0.134 sec
		2715
		2716	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2717	benchmarks actually make blocking connects and use 100% blocking I/O,
		2718	defeating the purpose of an event-based solution. All of the newly
		2719	written AnyEvent benchmarks use 100% non-blocking connects (using
		2720	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2721	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2722	generally require a lot more bookkeeping and event handling than blocking
		2723	connects (which involve a single syscall only).
		2724
		2725	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2726	offers similar expressive power as POE and IO::Lambda, using conventional
		2727	Perl syntax. This means that both the echo server and the client are 100%
		2728	non-blocking, further placing it at a disadvantage.
		2729
		2730	As you can see, the AnyEvent + EV combination even beats the
		2731	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2732	backend easily beats IO::Lambda and POE.
		2733
		2734	And even the 100% non-blocking version written using the high-level (and
		2735	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda
		2736	higher level ("unoptimised") abstractions by a large margin, even though
		2737	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
		2738
		2739	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2740	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2741	part of the IO::Lambda distribution and were used without any changes.
		2742
		2743
		2744	=head1 SIGNALS
		2745
		2746	AnyEvent currently installs handlers for these signals:
		2747
		2748	=over 4
		2749
		2750	=item SIGCHLD
		2751
		2752	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2753	emulation for event loops that do not support them natively. Also, some
		2754	event loops install a similar handler.
		2755
		2756	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2757	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2758
		2759	=item SIGPIPE
		2760
		2761	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2762	when AnyEvent gets loaded.
		2763
		2764	The rationale for this is that AnyEvent users usually do not really depend
		2765	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2766	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2767	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2768	some random socket.
		2769
		2770	The rationale for installing a no-op handler as opposed to ignoring it is
		2771	that this way, the handler will be restored to defaults on exec.
		2772
		2773	Feel free to install your own handler, or reset it to defaults.
		2774
		2775	=back
		2776
		2777	=cut
		2778
		2779	undef $SIG{CHLD}
		2780	if $SIG{CHLD} eq 'IGNORE';
		2781
		2782	$SIG{PIPE} = sub { }
		2783	unless defined $SIG{PIPE};
		2784
		2785	=head1 RECOMMENDED/OPTIONAL MODULES
		2786
		2787	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2788	its built-in modules) are required to use it.
		2789
		2790	That does not mean that AnyEvent won't take advantage of some additional
		2791	modules if they are installed.
		2792
		2793	This section explains which additional modules will be used, and how they
		2794	affect AnyEvent's operation.
		2795
		2796	=over 4
		2797
		2798	=item L<Async::Interrupt>
		2799
		2800	This slightly arcane module is used to implement fast signal handling: To
		2801	my knowledge, there is no way to do completely race-free and quick
		2802	signal handling in pure perl. To ensure that signals still get
		2803	delivered, AnyEvent will start an interval timer to wake up perl (and
		2804	catch the signals) with some delay (default is 10 seconds, look for
		2805	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2806
		2807	If this module is available, then it will be used to implement signal
		2808	catching, which means that signals will not be delayed, and the event loop
		2809	will not be interrupted regularly, which is more efficient (and good for
		2810	battery life on laptops).
		2811
		2812	This affects not just the pure-perl event loop, but also other event loops
		2813	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2814
		2815	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2816	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2817	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2818	does nothing for those backends.
		2819
		2820	=item L<EV>
		2821
		2822	This module isn't really "optional", as it is simply one of the backend
		2823	event loops that AnyEvent can use. However, it is simply the best event
		2824	loop available in terms of features, speed and stability: It supports
		2825	the AnyEvent API optimally, implements all the watcher types in XS, does
		2826	automatic timer adjustments even when no monotonic clock is available,
		2827	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2828	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2829	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2830
		2831	If you only use backends that rely on another event loop (e.g. C<Tk>),
		2832	then this module will do nothing for you.
		2833
		2834	=item L<Guard>
		2835
		2836	The guard module, when used, will be used to implement
		2837	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2838	lot less memory), but otherwise doesn't affect guard operation much. It is
		2839	purely used for performance.
		2840
		2841	=item L<JSON> and L<JSON::XS>
		2842
		2843	One of these modules is required when you want to read or write JSON data
		2844	via L<AnyEvent::Handle>. L<JSON> is also written in pure-perl, but can take
		2845	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2846
		2847	=item L<Net::SSLeay>
		2848
		2849	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2850	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2851	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2852
		2853	=item L<Time::HiRes>
		2854
		2855	This module is part of perl since release 5.008. It will be used when the
		2856	chosen event library does not come with a timing source of its own. The
		2857	pure-perl event loop (L<AnyEvent::Loop>) will additionally load it to
		2858	try to use a monotonic clock for timing stability.
		2859
		2860	=back
		2861
834		2862
835	=head1 FORK	2863	=head1 FORK
836		2864
837	Most event libraries are not fork-safe. The ones who are usually are	2865	Most event libraries are not fork-safe. The ones who are usually are
838	because they are so inefficient. Only L<EV> is fully fork-aware.	2866	because they rely on inefficient but fork-safe C<select> or C<poll> calls
		2867	- higher performance APIs such as BSD's kqueue or the dreaded Linux epoll
		2868	are usually badly thought-out hacks that are incompatible with fork in
		2869	one way or another. Only L<EV> is fully fork-aware and ensures that you
		2870	continue event-processing in both parent and child (or both, if you know
		2871	what you are doing).
		2872
		2873	This means that, in general, you cannot fork and do event processing in
		2874	the child if the event library was initialised before the fork (which
		2875	usually happens when the first AnyEvent watcher is created, or the library
		2876	is loaded).
839		2877
840	If you have to fork, you must either do so I<before> creating your first	2878	If you have to fork, you must either do so I<before> creating your first
841	watcher OR you must not use AnyEvent at all in the child.	2879	watcher OR you must not use AnyEvent at all in the child OR you must do
		2880	something completely out of the scope of AnyEvent.
		2881
		2882	The problem of doing event processing in the parent I<and> the child
		2883	is much more complicated: even for backends that I<are> fork-aware or
		2884	fork-safe, their behaviour is not usually what you want: fork clones all
		2885	watchers, that means all timers, I/O watchers etc. are active in both
		2886	parent and child, which is almost never what you want. USing C<exec>
		2887	to start worker children from some kind of manage rprocess is usually
		2888	preferred, because it is much easier and cleaner, at the expense of having
		2889	to have another binary.
		2890
842		2891
843	=head1 SECURITY CONSIDERATIONS	2892	=head1 SECURITY CONSIDERATIONS
844		2893
845	AnyEvent can be forced to load any event model via	2894	AnyEvent can be forced to load any event model via
846	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to	2895	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
…		…
850	specified in the variable.	2899	specified in the variable.
851		2900
852	You can make AnyEvent completely ignore this variable by deleting it	2901	You can make AnyEvent completely ignore this variable by deleting it
853	before the first watcher gets created, e.g. with a C<BEGIN> block:	2902	before the first watcher gets created, e.g. with a C<BEGIN> block:
854		2903
855	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	2904	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
856		2905
857	use AnyEvent;	2906	use AnyEvent;
		2907
		2908	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		2909	be used to probe what backend is used and gain other information (which is
		2910	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2911	$ENV{PERL_ANYEVENT_STRICT}.
		2912
		2913	Note that AnyEvent will remove I<all> environment variables starting with
		2914	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2915	enabled.
		2916
		2917
		2918	=head1 BUGS
		2919
		2920	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2921	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2922	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2923	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2924	pronounced).
		2925
858		2926
859	=head1 SEE ALSO	2927	=head1 SEE ALSO
860		2928
861	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	2929	Tutorial/Introduction: L<AnyEvent::Intro>.
862	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,
863	L<Event::Lib>.
864		2930
865	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	2931	FAQ: L<AnyEvent::FAQ>.
		2932
		2933	Utility functions: L<AnyEvent::Util> (misc. grab-bag), L<AnyEvent::Log>
		2934	(simply logging).
		2935
		2936	Development/Debugging: L<AnyEvent::Strict> (stricter checking),
		2937	L<AnyEvent::Debug> (interactive shell, watcher tracing).
		2938
		2939	Supported event modules: L<AnyEvent::Loop>, L<EV>, L<EV::Glib>,
		2940	L<Glib::EV>, L<Event>, L<Glib::Event>, L<Glib>, L<Tk>, L<Event::Lib>,
		2941	L<Qt>, L<POE>, L<FLTK>.
		2942
		2943	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
		2944	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
		2945	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
866	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,	2946	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>, L<Anyevent::Impl::Irssi>,
867	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>.	2947	L<AnyEvent::Impl::FLTK>.
868		2948
		2949	Non-blocking handles, pipes, stream sockets, TCP clients and
		2950	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
		2951
		2952	Asynchronous DNS: L<AnyEvent::DNS>.
		2953
		2954	Thread support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
		2955
869	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	2956	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::IRC>,
		2957	L<AnyEvent::HTTP>.
		2958
870		2959
871	=head1 AUTHOR	2960	=head1 AUTHOR
872		2961
873	Marc Lehmann <schmorp@schmorp.de>	2962	Marc Lehmann <schmorp@schmorp.de>
874	http://home.schmorp.de/	2963	http://home.schmorp.de/
875		2964
876	=cut	2965	=cut
877		2966
878	1	2967	1
879		2968

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