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Revision 1.132 by root, Sun May 25 01:05:27 2008 UTC vs.
Revision 1.369 by root, Wed Aug 17 02:32:01 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, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event loops	5	EV, Event, Glib, Tk, Perl, Event::Lib, Irssi, rxvt-unicode, IO::Async, Qt,
		6	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
20	$w->send; # wake up current and all future recv's	38	$w->send; # wake up current and all future recv's
21	$w->recv; # enters "main loop" till $condvar gets ->send	39	$w->recv; # enters "main loop" till $condvar gets ->send
		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 enormous 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	=head1 DESCRIPTION	114	=head1 DESCRIPTION
72		115
73	L<AnyEvent> provides an identical interface to multiple event loops. This	116	L<AnyEvent> provides a uniform interface to various event loops. This
74	allows module authors to utilise an event loop without forcing module	117	allows module authors to use event loop functionality without forcing
75	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
76	peacefully at any one time).	119	than one event loop cannot coexist peacefully).
77		120
78	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>
79	module.	122	module.
80		123
81	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
82	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
83	following modules is already loaded: L<EV>,	126	following modules is already loaded: L<EV>, L<AnyEvent::Loop>,
84	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,	127	L<Event>, L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>. The first one
85	L<POE>. The first one found is used. If none are found, the module tries	128	found is used. If none are detected, the module tries to load the first
86	to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl	129	four modules in the order given; but note that if L<EV> is not
87	adaptor should always succeed) in the order given. The first one that can	130	available, the pure-perl L<AnyEvent::Loop> should always work, so
88	be successfully loaded will be used. If, after this, still none could be	131	the other two are not normally tried.
89	found, AnyEvent will fall back to a pure-perl event loop, which is not
90	very efficient, but should work everywhere.
91		132
92	Because AnyEvent first checks for modules that are already loaded, loading	133	Because AnyEvent first checks for modules that are already loaded, loading
93	an event model explicitly before first using AnyEvent will likely make	134	an event model explicitly before first using AnyEvent will likely make
94	that model the default. For example:	135	that model the default. For example:
95		136
…		…
97	use AnyEvent;	138	use AnyEvent;
98		139
99	# .. AnyEvent will likely default to Tk	140	# .. AnyEvent will likely default to Tk
100		141
101	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
102	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,
103	use AnyEvent so their modules work together with others seamlessly...	144	as very few modules hardcode event loops without announcing this very
		145	loudly.
104		146
105	The pure-perl implementation of AnyEvent is called	147	The pure-perl implementation of AnyEvent is called C<AnyEvent::Loop>. Like
106	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
107	explicitly.	149	availability of that event loop :)
108		150
109	=head1 WATCHERS	151	=head1 WATCHERS
110		152
111	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
112	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
…		…
115	These watchers are normal Perl objects with normal Perl lifetime. After	157	These watchers are normal Perl objects with normal Perl lifetime. After
116	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
117	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
118	is in control).	160	is in control).
119		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
120	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
121	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
122	to it).	170	to it).
123		171
124	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.
125		173
126	Many watchers either are used with "recursion" (repeating timers for	174	Many watchers either are used with "recursion" (repeating timers for
127	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.
128		176
129	An any way to achieve that is this pattern:	177	One way to achieve that is this pattern:
130		178
131	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	179	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
132	# you can use $w here, for example to undef it	180	# you can use $w here, for example to undef it
133	undef $w;	181	undef $w;
134	});	182	});
135		183
136	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,
137	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
138	declared.	186	declared.
139		187
140	=head2 I/O WATCHERS	188	=head2 I/O WATCHERS
141		189
		190	$w = AnyEvent->io (
		191	fh => <filehandle_or_fileno>,
		192	poll => <"r" or "w">,
		193	cb => <callback>,
		194	);
		195
142	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
143	with the following mandatory key-value pairs as arguments:	197	with the following mandatory key-value pairs as arguments:
144		198
145	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch	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
146	for events. C<poll> must be a string that is either C<r> or C<w>,	206	C<poll> must be a string that is either C<r> or C<w>, which creates a
147	which creates a watcher waiting for "r"eadable or "w"ritable events,	207	watcher waiting for "r"eadable or "w"ritable events, respectively.
		208
148	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.
149	becomes ready.
150		210
151	Although the callback might get passed parameters, their value and	211	Although the callback might get passed parameters, their value and
152	presence is undefined and you cannot rely on them. Portable AnyEvent	212	presence is undefined and you cannot rely on them. Portable AnyEvent
153	callbacks cannot use arguments passed to I/O watcher callbacks.	213	callbacks cannot use arguments passed to I/O watcher callbacks.
154		214
155	The I/O watcher might use the underlying file descriptor or a copy of it.	215	The I/O watcher might use the underlying file descriptor or a copy of it.
156	You must not close a file handle as long as any watcher is active on the	216	You must not close a file handle as long as any watcher is active on the
157	underlying file descriptor.	217	underlying file descriptor.
158		218
159	Some event loops issue spurious readyness notifications, so you should	219	Some event loops issue spurious readiness notifications, so you should
160	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
161	handles.	221	handles.
162		222
163	Example:
164
165	# 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
166	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	226	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
167	chomp (my $input = <STDIN>);	227	chomp (my $input = <STDIN>);
168	warn "read: $input\n";	228	warn "read: $input\n";
169	undef $w;	229	undef $w;
170	});	230	});
171		231
172	=head2 TIME WATCHERS	232	=head2 TIME WATCHERS
173		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
174	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 >>
175	method with the following mandatory arguments:	243	method with the following mandatory arguments:
176		244
177	C<after> specifies after how many seconds (fractional values are	245	C<after> specifies after how many seconds (fractional values are
178	supported) the callback should be invoked. C<cb> is the callback to invoke	246	supported) the callback should be invoked. C<cb> is the callback to invoke
…		…
180		248
181	Although the callback might get passed parameters, their value and	249	Although the callback might get passed parameters, their value and
182	presence is undefined and you cannot rely on them. Portable AnyEvent	250	presence is undefined and you cannot rely on them. Portable AnyEvent
183	callbacks cannot use arguments passed to time watcher callbacks.	251	callbacks cannot use arguments passed to time watcher callbacks.
184		252
185	The timer callback will be invoked at most once: if you want a repeating	253	The callback will normally be invoked only once. If you specify another
186	timer you have to create a new watcher (this is a limitation by both Tk	254	parameter, C<interval>, as a strictly positive number (> 0), then the
187	and Glib).	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.
188		258
189	Example:	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.
190		262
191	# fire an event after 7.7 seconds	263	Example: fire an event after 7.7 seconds.
		264
192	my $w = AnyEvent->timer (after => 7.7, cb => sub {	265	my $w = AnyEvent->timer (after => 7.7, cb => sub {
193	warn "timeout\n";	266	warn "timeout\n";
194	});	267	});
195		268
196	# to cancel the timer:	269	# to cancel the timer:
197	undef $w;	270	undef $w;
198		271
199	Example 2:
200
201	# 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.
202	my $w;
203		273
204	my $cb = sub {
205	# cancel the old timer while creating a new one
206	$w = AnyEvent->timer (after => 1, cb => $cb);	274	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		275	warn "timeout\n";
207	};	276	};
208
209	# start the "loop" by creating the first watcher
210	$w = AnyEvent->timer (after => 0.5, cb => $cb);
211		277
212	=head3 TIMING ISSUES	278	=head3 TIMING ISSUES
213		279
214	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
215	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
…		…
217		283
218	While most event loops expect timers to specified in a relative way, they	284	While most event loops expect timers to specified in a relative way, they
219	use absolute time internally. This makes a difference when your clock	285	use absolute time internally. This makes a difference when your clock
220	"jumps", for example, when ntp decides to set your clock backwards from	286	"jumps", for example, when ntp decides to set your clock backwards from
221	the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to	287	the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to
222	fire "after" a second might actually take six years to finally fire.	288	fire "after a second" might actually take six years to finally fire.
223		289
224	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
225	about these issues is L<EV>, which offers both relative (ev_timer, based	291	of these issues is L<EV>, which offers both relative (ev_timer, based
226	on true relative time) and absolute (ev_periodic, based on wallclock time)	292	on true relative time) and absolute (ev_periodic, based on wallclock time)
227	timers.	293	timers.
228		294
229	AnyEvent always prefers relative timers, if available, matching the	295	AnyEvent always prefers relative timers, if available, matching the
230	AnyEvent API.	296	AnyEvent API.
231		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
232	=head2 SIGNAL WATCHERS	383	=head2 SIGNAL WATCHERS
233		384
		385	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		386
234	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
235	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
236	be invoked whenever a signal occurs.	389	callback to be invoked whenever a signal occurs.
237		390
238	Although the callback might get passed parameters, their value and	391	Although the callback might get passed parameters, their value and
239	presence is undefined and you cannot rely on them. Portable AnyEvent	392	presence is undefined and you cannot rely on them. Portable AnyEvent
240	callbacks cannot use arguments passed to signal watcher callbacks.	393	callbacks cannot use arguments passed to signal watcher callbacks.
241		394
…		…
243	invocation, and callback invocation will be synchronous. Synchronous means	396	invocation, and callback invocation will be synchronous. Synchronous means
244	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,
245	but it is guaranteed not to interrupt any other callbacks.	398	but it is guaranteed not to interrupt any other callbacks.
246		399
247	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
248	between multiple watchers.	401	between multiple watchers, and AnyEvent will ensure that signals will not
		402	interrupt your program at bad times.
249		403
250	This watcher might use C<%SIG>, so programs overwriting those signals	404	This watcher might use C<%SIG> (depending on the event loop used),
251	directly will likely not work correctly.	405	so programs overwriting those signals directly will likely not work
		406	correctly.
252		407
253	Example: exit on SIGINT	408	Example: exit on SIGINT
254		409
255	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	410	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
256		411
		412	=head3 Restart Behaviour
		413
		414	While restart behaviour is up to the event loop implementation, most will
		415	not restart syscalls (that includes L<Async::Interrupt> and AnyEvent's
		416	pure perl implementation).
		417
		418	=head3 Safe/Unsafe Signals
		419
		420	Perl signals can be either "safe" (synchronous to opcode handling) or
		421	"unsafe" (asynchronous) - the former might get delayed indefinitely, the
		422	latter might corrupt your memory.
		423
		424	AnyEvent signal handlers are, in addition, synchronous to the event loop,
		425	i.e. they will not interrupt your running perl program but will only be
		426	called as part of the normal event handling (just like timer, I/O etc.
		427	callbacks, too).
		428
		429	=head3 Signal Races, Delays and Workarounds
		430
		431	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		432	callbacks to signals in a generic way, which is a pity, as you cannot
		433	do race-free signal handling in perl, requiring C libraries for
		434	this. AnyEvent will try to do its best, which means in some cases,
		435	signals will be delayed. The maximum time a signal might be delayed is
		436	specified in C<$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
257	=head2 CHILD PROCESS WATCHERS	449	=head2 CHILD PROCESS WATCHERS
258		450
		451	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		452
259	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.
260		454
261	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,
262	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
263	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
264	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
265	and exit status (as returned by waitpid), so unlike other watcher types,	459	(stopped/continued).
266	you I<can> rely on child watcher callback arguments.	460
		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.
		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).
267		469
268	There is a slight catch to child watchers, however: you usually start them	470	There is a slight catch to child watchers, however: you usually start them
269	I<after> the child process was created, and this means the process could	471	I<after> the child process was created, and this means the process could
270	have exited already (and no SIGCHLD will be sent anymore).	472	have exited already (and no SIGCHLD will be sent anymore).
271		473
272	Not all event models handle this correctly (POE doesn't), but even for	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
273	event models that I<do> handle this correctly, they usually need to be	476	that I<do> handle this correctly, they usually need to be loaded before
274	loaded before the process exits (i.e. before you fork in the first place).	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.
275		480
276	This means you cannot create a child watcher as the very first thing in an	481	This means you cannot create a child watcher as the very first
277	AnyEvent program, you I<have> to create at least one watcher before you	482	thing in an AnyEvent program, you I<have> to create at least one
278	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).	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.
279		489
280	Example: fork a process and wait for it	490	Example: fork a process and wait for it
281		491
282	my $done = AnyEvent->condvar;	492	my $done = AnyEvent->condvar;
283		493
284	my $pid = fork or exit 5;	494	my $pid = fork or exit 5;
285		495
286	my $w = AnyEvent->child (	496	my $w = AnyEvent->child (
287	pid => $pid,	497	pid => $pid,
288	cb => sub {	498	cb => sub {
289	my ($pid, $status) = @_;	499	my ($pid, $status) = @_;
290	warn "pid $pid exited with status $status";	500	warn "pid $pid exited with status $status";
291	$done->send;	501	$done->send;
292	},	502	},
293	);	503	);
294		504
295	# do something else, then wait for process exit	505	# do something else, then wait for process exit
296	$done->recv;	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	});
297		547
298	=head2 CONDITION VARIABLES	548	=head2 CONDITION VARIABLES
		549
		550	$cv = AnyEvent->condvar;
		551
		552	$cv->send (<list>);
		553	my @res = $cv->recv;
299		554
300	If you are familiar with some event loops you will know that all of them	555	If you are familiar with some event loops you will know that all of them
301	require you to run some blocking "loop", "run" or similar function that	556	require you to run some blocking "loop", "run" or similar function that
302	will actively watch for new events and call your callbacks.	557	will actively watch for new events and call your callbacks.
303		558
304	AnyEvent is different, it expects somebody else to run the event loop and	559	AnyEvent is slightly different: it expects somebody else to run the event
305	will only block when necessary (usually when told by the user).	560	loop and will only block when necessary (usually when told by the user).
306		561
307	The instrument to do that is called a "condition variable", so called	562	The tool to do that is called a "condition variable", so called because
308	because they represent a condition that must become true.	563	they represent a condition that must become true.
		564
		565	Now is probably a good time to look at the examples further below.
309		566
310	Condition variables can be created by calling the C<< AnyEvent->condvar	567	Condition variables can be created by calling the C<< AnyEvent->condvar
311	>> method, usually without arguments. The only argument pair allowed is	568	>> method, usually without arguments. The only argument pair allowed is
312	C<cb>, which specifies a callback to be called when the condition variable	569	C<cb>, which specifies a callback to be called when the condition variable
313	becomes true.	570	becomes true, with the condition variable as the first argument (but not
		571	the results).
314		572
315	After creation, the condition variable is "false" until it becomes "true"	573	After creation, the condition variable is "false" until it becomes "true"
316	by calling the C<send> method (or calling the condition variable as if it	574	by calling the C<send> method (or calling the condition variable as if it
317	were a callback).	575	were a callback, read about the caveats in the description for the C<<
		576	->send >> method).
318		577
319	Condition variables are similar to callbacks, except that you can	578	Since condition variables are the most complex part of the AnyEvent API, here are
320	optionally wait for them. They can also be called merge points - points	579	some different mental models of what they are - pick the ones you can connect to:
321	in time where multiple outstanding events have been processed. And yet	580
322	another way to call them is transactions - each condition variable can be	581	=over 4
323	used to represent a transaction, which finishes at some point and delivers	582
324	a result.	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
325		601
326	Condition variables are very useful to signal that something has finished,	602	Condition variables are very useful to signal that something has finished,
327	for example, if you write a module that does asynchronous http requests,	603	for example, if you write a module that does asynchronous http requests,
328	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
329	availability of results. The user can either act when the callback is	605	availability of results. The user can either act when the callback is
…		…
342		618
343	Condition variables are represented by hash refs in perl, and the keys	619	Condition variables are represented by hash refs in perl, and the keys
344	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing	620	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
345	easy (it is often useful to build your own transaction class on top of	621	easy (it is often useful to build your own transaction class on top of
346	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call	622	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
347	it's C<new> method in your own C<new> method.	623	its C<new> method in your own C<new> method.
348		624
349	There are two "sides" to a condition variable - the "producer side" which	625	There are two "sides" to a condition variable - the "producer side" which
350	eventually calls C<< -> send >>, and the "consumer side", which waits	626	eventually calls C<< -> send >>, and the "consumer side", which waits
351	for the send to occur.	627	for the send to occur.
352		628
353	Example: wait for a timer.	629	Example: wait for a timer.
354		630
355	# wait till the result is ready	631	# condition: "wait till the timer is fired"
356	my $result_ready = AnyEvent->condvar;	632	my $timer_fired = AnyEvent->condvar;
357		633
358	# do something such as adding a timer	634	# create the timer - we could wait for, say
359	# or socket watcher the calls $result_ready->send	635	# a handle becomign ready, or even an
360	# when the "result" is ready.	636	# AnyEvent::HTTP request to finish, but
361	# in this case, we simply use a timer:	637	# in this case, we simply use a timer:
362	my $w = AnyEvent->timer (	638	my $w = AnyEvent->timer (
363	after => 1,	639	after => 1,
364	cb => sub { $result_ready->send },	640	cb => sub { $timer_fired->send },
365	);	641	);
366		642
367	# this "blocks" (while handling events) till the callback	643	# this "blocks" (while handling events) till the callback
368	# calls send	644	# calls ->send
369	$result_ready->recv;	645	$timer_fired->recv;
370		646
371	Example: wait for a timer, but take advantage of the fact that	647	Example: wait for a timer, but take advantage of the fact that condition
372	condition variables are also code references.	648	variables are also callable directly.
373		649
374	my $done = AnyEvent->condvar;	650	my $done = AnyEvent->condvar;
375	my $delay = AnyEvent->timer (after => 5, cb => $done);	651	my $delay = AnyEvent->timer (after => 5, cb => $done);
376	$done->recv;	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	});
377		670
378	=head3 METHODS FOR PRODUCERS	671	=head3 METHODS FOR PRODUCERS
379		672
380	These methods should only be used by the producing side, i.e. the	673	These methods should only be used by the producing side, i.e. the
381	code/module that eventually sends the signal. Note that it is also	674	code/module that eventually sends the signal. Note that it is also
…		…
394	immediately from within send.	687	immediately from within send.
395		688
396	Any arguments passed to the C<send> call will be returned by all	689	Any arguments passed to the C<send> call will be returned by all
397	future C<< ->recv >> calls.	690	future C<< ->recv >> calls.
398		691
399	Condition variables are overloaded so one can call them directly (as a	692	Condition variables are overloaded so one can call them directly (as if
400	code reference). Calling them directly is the same as calling C<send>.	693	they were a code reference). Calling them directly is the same as calling
		694	C<send>.
401		695
402	=item $cv->croak ($error)	696	=item $cv->croak ($error)
403		697
404	Similar to send, but causes all call's to C<< ->recv >> to invoke	698	Similar to send, but causes all calls to C<< ->recv >> to invoke
405	C<Carp::croak> with the given error message/object/scalar.	699	C<Carp::croak> with the given error message/object/scalar.
406		700
407	This can be used to signal any errors to the condition variable	701	This can be used to signal any errors to the condition variable
408	user/consumer.	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.
409		707
410	=item $cv->begin ([group callback])	708	=item $cv->begin ([group callback])
411		709
412	=item $cv->end	710	=item $cv->end
413
414	These two methods are EXPERIMENTAL and MIGHT CHANGE.
415		711
416	These two methods can be used to combine many transactions/events into	712	These two methods can be used to combine many transactions/events into
417	one. For example, a function that pings many hosts in parallel might want	713	one. For example, a function that pings many hosts in parallel might want
418	to use a condition variable for the whole process.	714	to use a condition variable for the whole process.
419		715
420	Every call to C<< ->begin >> will increment a counter, and every call to	716	Every call to C<< ->begin >> will increment a counter, and every call to
421	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end	717	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
422	>>, the (last) callback passed to C<begin> will be executed. That callback	718	>>, the (last) callback passed to C<begin> will be executed, passing the
423	is I<supposed> to call C<< ->send >>, but that is not required. If no	719	condvar as first argument. That callback is I<supposed> to call C<< ->send
424	callback was set, C<send> will be called without any arguments.	720	>>, but that is not required. If no group callback was set, C<send> will
		721	be called without any arguments.
425		722
426	Let's clarify this with the ping example:	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:
427		730
428	my $cv = AnyEvent->condvar;	731	my $cv = AnyEvent->condvar;
429		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
430	my %result;	757	my %result;
431	$cv->begin (sub { $cv->send (\%result) });	758	$cv->begin (sub { shift->send (\%result) });
432		759
433	for my $host (@list_of_hosts) {	760	for my $host (@list_of_hosts) {
434	$cv->begin;	761	$cv->begin;
435	ping_host_then_call_callback $host, sub {	762	ping_host_then_call_callback $host, sub {
436	$result{$host} = ...;	763	$result{$host} = ...;
…		…
451	loop, which serves two important purposes: first, it sets the callback	778	loop, which serves two important purposes: first, it sets the callback
452	to be called once the counter reaches C<0>, and second, it ensures that	779	to be called once the counter reaches C<0>, and second, it ensures that
453	C<send> is called even when C<no> hosts are being pinged (the loop	780	C<send> is called even when C<no> hosts are being pinged (the loop
454	doesn't execute once).	781	doesn't execute once).
455		782
456	This is the general pattern when you "fan out" into multiple subrequests:	783	This is the general pattern when you "fan out" into multiple (but
457	use an outer C<begin>/C<end> pair to set the callback and ensure C<end>	784	potentially zero) subrequests: use an outer C<begin>/C<end> pair to set
458	is called at least once, and then, for each subrequest you start, call	785	the callback and ensure C<end> is called at least once, and then, for each
459	C<begin> and for each subrequest you finish, call C<end>.	786	subrequest you start, call C<begin> and for each subrequest you finish,
		787	call C<end>.
460		788
461	=back	789	=back
462		790
463	=head3 METHODS FOR CONSUMERS	791	=head3 METHODS FOR CONSUMERS
464		792
…		…
468	=over 4	796	=over 4
469		797
470	=item $cv->recv	798	=item $cv->recv
471		799
472	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak	800	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
473	>> methods have been called on c<$cv>, while servicing other watchers	801	>> methods have been called on C<$cv>, while servicing other watchers
474	normally.	802	normally.
475		803
476	You can only wait once on a condition - additional calls are valid but	804	You can only wait once on a condition - additional calls are valid but
477	will return immediately.	805	will return immediately.
478		806
…		…
480	function will call C<croak>.	808	function will call C<croak>.
481		809
482	In list context, all parameters passed to C<send> will be returned,	810	In list context, all parameters passed to C<send> will be returned,
483	in scalar context only the first one will be returned.	811	in scalar context only the first one will be returned.
484		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.
		819
485	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
486	(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
487	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
488	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
489	condition variables with some kind of request results and supporting	824	condition variables with some kind of request results and supporting
490	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,
491	while still supporting blocking waits if the caller so desires).	826	while still supporting blocking waits if the caller so desires).
492		827
493	Another reason I<never> to C<< ->recv >> in a module is that you cannot
494	sensibly have two C<< ->recv >>'s in parallel, as that would require
495	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
496	can supply.
497
498	The L<Coro> module, however, I<can> and I<does> supply coroutines and, in
499	fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe
500	versions and also integrates coroutines into AnyEvent, making blocking
501	C<< ->recv >> calls perfectly safe as long as they are done from another
502	coroutine (one that doesn't run the event loop).
503
504	You can ensure that C<< -recv >> never blocks by setting a callback and	828	You can ensure that C<< ->recv >> never blocks by setting a callback and
505	only calling C<< ->recv >> from within that callback (or at a later	829	only calling C<< ->recv >> from within that callback (or at a later
506	time). This will work even when the event loop does not support blocking	830	time). This will work even when the event loop does not support blocking
507	waits otherwise.	831	waits otherwise.
508		832
509	=item $bool = $cv->ready	833	=item $bool = $cv->ready
510		834
511	Returns true when the condition is "true", i.e. whether C<send> or	835	Returns true when the condition is "true", i.e. whether C<send> or
512	C<croak> have been called.	836	C<croak> have been called.
513		837
514	=item $cb = $cv->cb ([new callback])	838	=item $cb = $cv->cb ($cb->($cv))
515		839
516	This is a mutator function that returns the callback set and optionally	840	This is a mutator function that returns the callback set and optionally
517	replaces it before doing so.	841	replaces it before doing so.
518		842
519	The callback will be called when the condition becomes "true", i.e. when	843	The callback will be called when the condition becomes "true", i.e. when
520	C<send> or C<croak> are called. Calling C<recv> inside the callback	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
521	or at any later time is guaranteed not to block.	847	the callback or at any later time is guaranteed not to block.
522		848
523	=back	849	=back
524		850
		851	=head1 SUPPORTED EVENT LOOPS/BACKENDS
		852
		853	The available backend classes are (every class has its own manpage):
		854
		855	=over 4
		856
		857	=item Backends that are autoprobed when no other event loop can be found.
		858
		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::FLTK2 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
		913
525	=head1 GLOBAL VARIABLES AND FUNCTIONS	914	=head1 GLOBAL VARIABLES AND FUNCTIONS
526		915
		916	These are not normally required to use AnyEvent, but can be useful to
		917	write AnyEvent extension modules.
		918
527	=over 4	919	=over 4
528		920
529	=item $AnyEvent::MODEL	921	=item $AnyEvent::MODEL
530		922
531	Contains C<undef> until the first watcher is being created. Then it	923	Contains C<undef> until the first watcher is being created, before the
		924	backend has been autodetected.
		925
532	contains the event model that is being used, which is the name of the	926	Afterwards it contains the event model that is being used, which is the
533	Perl class implementing the model. This class is usually one of the	927	name of the Perl class implementing the model. This class is usually one
534	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	928	of the C<AnyEvent::Impl::xxx> modules, but can be any other class in the
535	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	929	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
536		930	will be C<urxvt::anyevent>).
537	The known classes so far are:
538
539	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
540	AnyEvent::Impl::Event based on Event, second best choice.
541	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
542	AnyEvent::Impl::Glib based on Glib, third-best choice.
543	AnyEvent::Impl::Tk based on Tk, very bad choice.
544	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
545	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
546	AnyEvent::Impl::POE based on POE, not generic enough for full support.
547
548	There is no support for WxWidgets, as WxWidgets has no support for
549	watching file handles. However, you can use WxWidgets through the
550	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
551	second, which was considered to be too horrible to even consider for
552	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
553	it's adaptor.
554
555	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
556	autodetecting them.
557		931
558	=item AnyEvent::detect	932	=item AnyEvent::detect
559		933
560	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	934	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
561	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
562	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
563	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>.
564		945
565	=item $guard = AnyEvent::post_detect { BLOCK }	946	=item $guard = AnyEvent::post_detect { BLOCK }
566		947
567	Arranges for the code block to be executed as soon as the event model is	948	Arranges for the code block to be executed as soon as the event model is
568	autodetected (or immediately if this has already happened).	949	autodetected (or immediately if that has already happened).
		950
		951	The block will be executed I<after> the actual backend has been detected
		952	(C<$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.
569		961
570	If called in scalar or list context, then it creates and returns an object	962	If called in scalar or list context, then it creates and returns an object
571	that automatically removes the callback again when it is destroyed. See	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
572	L<Coro::BDB> for a case where this is useful.	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 ||= $guard;
573		982
574	=item @AnyEvent::post_detect	983	=item @AnyEvent::post_detect
575		984
576	If there are any code references in this array (you can C<push> to it	985	If there are any code references in this array (you can C<push> to it
577	before or after loading AnyEvent), then they will called directly after	986	before or after loading AnyEvent), then they will be called directly
578	the event loop has been chosen.	987	after the event loop has been chosen.
579		988
580	You should check C<$AnyEvent::MODEL> before adding to this array, though:	989	You should check C<$AnyEvent::MODEL> before adding to this array, though:
581	if it contains a true value then the event loop has already been detected,	990	if it is defined then the event loop has already been detected, and the
582	and the array will be ignored.	991	array will be ignored.
583		992
584	Best use C<AnyEvent::post_detect { BLOCK }> instead.	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	Loads AnyEvent::Log on first use and calls C<AnyEvent::Log::log> -
		1059	consequently, look at the L<AnyEvent::Log> documentation for details.
		1060
		1061	If you want to sprinkle loads of logging calls around your code, consider
		1062	creating a logger callback with the C<AnyEvent::Log::logger< function.
585		1063
586	=back	1064	=back
587		1065
588	=head1 WHAT TO DO IN A MODULE	1066	=head1 WHAT TO DO IN A MODULE
589		1067
…		…
600	because it will stall the whole program, and the whole point of using	1078	because it will stall the whole program, and the whole point of using
601	events is to stay interactive.	1079	events is to stay interactive.
602		1080
603	It is fine, however, to call C<< ->recv >> when the user of your module	1081	It is fine, however, to call C<< ->recv >> when the user of your module
604	requests it (i.e. if you create a http request object ad have a method	1082	requests it (i.e. if you create a http request object ad have a method
605	called C<results> that returns the results, it should call C<< ->recv >>	1083	called C<results> that returns the results, it may call C<< ->recv >>
606	freely, as the user of your module knows what she is doing. always).	1084	freely, as the user of your module knows what she is doing. Always).
607		1085
608	=head1 WHAT TO DO IN THE MAIN PROGRAM	1086	=head1 WHAT TO DO IN THE MAIN PROGRAM
609		1087
610	There will always be a single main program - the only place that should	1088	There will always be a single main program - the only place that should
611	dictate which event model to use.	1089	dictate which event model to use.
612		1090
613	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	1091	If the program is not event-based, it need not do anything special, even
614	do anything special (it does not need to be event-based) and let AnyEvent	1092	when it depends on a module that uses an AnyEvent. If the program itself
615	decide which implementation to chose if some module relies on it.	1093	uses AnyEvent, but does not care which event loop is used, all it needs
		1094	to do is C<use AnyEvent>. In either case, AnyEvent will choose the best
		1095	available loop implementation.
616		1096
617	If the main program relies on a specific event model. For example, in	1097	If the main program relies on a specific event model - for example, in
618	Gtk2 programs you have to rely on the Glib module. You should load the	1098	Gtk2 programs you have to rely on the Glib module - you should load the
619	event module before loading AnyEvent or any module that uses it: generally	1099	event module before loading AnyEvent or any module that uses it: generally
620	speaking, you should load it as early as possible. The reason is that	1100	speaking, you should load it as early as possible. The reason is that
621	modules might create watchers when they are loaded, and AnyEvent will	1101	modules might create watchers when they are loaded, and AnyEvent will
622	decide on the event model to use as soon as it creates watchers, and it	1102	decide on the event model to use as soon as it creates watchers, and it
623	might chose the wrong one unless you load the correct one yourself.	1103	might choose the wrong one unless you load the correct one yourself.
624		1104
625	You can chose to use a rather inefficient pure-perl implementation by	1105	You can chose to use a pure-perl implementation by loading the
626	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	1106	C<AnyEvent::Loop> module, which gives you similar behaviour
627	behaviour everywhere, but letting AnyEvent chose is generally better.	1107	everywhere, but letting AnyEvent chose the model is generally better.
		1108
		1109	=head2 MAINLOOP EMULATION
		1110
		1111	Sometimes (often for short test scripts, or even standalone programs who
		1112	only want to use AnyEvent), you do not want to run a specific event loop.
		1113
		1114	In that case, you can use a condition variable like this:
		1115
		1116	AnyEvent->condvar->recv;
		1117
		1118	This has the effect of entering the event loop and looping forever.
		1119
		1120	Note that usually your program has some exit condition, in which case
		1121	it is better to use the "traditional" approach of storing a condition
		1122	variable somewhere, waiting for it, and sending it when the program should
		1123	exit cleanly.
		1124
628		1125
629	=head1 OTHER MODULES	1126	=head1 OTHER MODULES
630		1127
631	The following is a non-exhaustive list of additional modules that use	1128	The following is a non-exhaustive list of additional modules that use
632	AnyEvent and can therefore be mixed easily with other AnyEvent modules	1129	AnyEvent as a client and can therefore be mixed easily with other
633	in the same program. Some of the modules come with AnyEvent, some are	1130	AnyEvent modules and other event loops in the same program. Some of the
634	available via CPAN.	1131	modules come as part of AnyEvent, the others are available via CPAN (see
		1132	L<http://search.cpan.org/search?m=module&q=anyevent%3A%3A*> for
		1133	a longer non-exhaustive list), and the list is heavily biased towards
		1134	modules of the AnyEvent author himself :)
635		1135
636	=over 4	1136	=over 4
637		1137
638	=item L<AnyEvent::Util>	1138	=item L<AnyEvent::Util>
639		1139
640	Contains various utility functions that replace often-used but blocking	1140	Contains various utility functions that replace often-used blocking
641	functions such as C<inet_aton> by event-/callback-based versions.	1141	functions such as C<inet_aton> with event/callback-based versions.
642
643	=item L<AnyEvent::Handle>
644
645	Provide read and write buffers and manages watchers for reads and writes.
646		1142
647	=item L<AnyEvent::Socket>	1143	=item L<AnyEvent::Socket>
648		1144
649	Provides various utility functions for (internet protocol) sockets,	1145	Provides various utility functions for (internet protocol) sockets,
650	addresses and name resolution. Also functions to create non-blocking tcp	1146	addresses and name resolution. Also functions to create non-blocking tcp
651	connections or tcp servers, with IPv6 and SRV record support and more.	1147	connections or tcp servers, with IPv6 and SRV record support and more.
652		1148
		1149	=item L<AnyEvent::Handle>
		1150
		1151	Provide read and write buffers, manages watchers for reads and writes,
		1152	supports raw and formatted I/O, I/O queued and fully transparent and
		1153	non-blocking SSL/TLS (via L<AnyEvent::TLS>).
		1154
		1155	=item L<AnyEvent::DNS>
		1156
		1157	Provides rich asynchronous DNS resolver capabilities.
		1158
		1159	=item L<AnyEvent::HTTP>, L<AnyEvent::IRC>, L<AnyEvent::XMPP>, L<AnyEvent::GPSD>, L<AnyEvent::IGS>, L<AnyEvent::FCP>
		1160
		1161	Implement event-based interfaces to the protocols of the same name (for
		1162	the curious, IGS is the International Go Server and FCP is the Freenet
		1163	Client Protocol).
		1164
		1165	=item L<AnyEvent::Handle::UDP>
		1166
		1167	Here be danger!
		1168
		1169	As Pauli would put it, "Not only is it not right, it's not even wrong!" -
		1170	there are so many things wrong with AnyEvent::Handle::UDP, most notably
		1171	its use of a stream-based API with a protocol that isn't streamable, that
		1172	the only way to improve it is to delete it.
		1173
		1174	It features data corruption (but typically only under load) and general
		1175	confusion. On top, the author is not only clueless about UDP but also
		1176	fact-resistant - some gems of his understanding: "connect doesn't work
		1177	with UDP", "UDP packets are not IP packets", "UDP only has datagrams, not
		1178	packets", "I don't need to implement proper error checking as UDP doesn't
		1179	support error checking" and so on - he doesn't even understand what's
		1180	wrong with his module when it is explained to him.
		1181
		1182	=item L<AnyEvent::DBI>
		1183
		1184	Executes L<DBI> requests asynchronously in a proxy process for you,
		1185	notifying you in an event-based way when the operation is finished.
		1186
		1187	=item L<AnyEvent::AIO>
		1188
		1189	Truly asynchronous (as opposed to non-blocking) I/O, should be in the
		1190	toolbox of every event programmer. AnyEvent::AIO transparently fuses
		1191	L<IO::AIO> and AnyEvent together, giving AnyEvent access to event-based
		1192	file I/O, and much more.
		1193
653	=item L<AnyEvent::HTTPD>	1194	=item L<AnyEvent::HTTPD>
654		1195
655	Provides a simple web application server framework.	1196	A simple embedded webserver.
656
657	=item L<AnyEvent::DNS>
658
659	Provides rich asynchronous DNS resolver capabilities.
660		1197
661	=item L<AnyEvent::FastPing>	1198	=item L<AnyEvent::FastPing>
662		1199
663	The fastest ping in the west.	1200	The fastest ping in the west.
664		1201
665	=item L<Net::IRC3>
666
667	AnyEvent based IRC client module family.
668
669	=item L<Net::XMPP2>
670
671	AnyEvent based XMPP (Jabber protocol) module family.
672
673	=item L<Net::FCP>
674
675	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
676	of AnyEvent.
677
678	=item L<Event::ExecFlow>
679
680	High level API for event-based execution flow control.
681
682	=item L<Coro>	1202	=item L<Coro>
683		1203
684	Has special support for AnyEvent via L<Coro::AnyEvent>.	1204	Has special support for AnyEvent via L<Coro::AnyEvent>.
685		1205
686	=item L<AnyEvent::AIO>, L<IO::AIO>
687
688	Truly asynchronous I/O, should be in the toolbox of every event
689	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
690	together.
691
692	=item L<AnyEvent::BDB>, L<BDB>
693
694	Truly asynchronous Berkeley DB access. AnyEvent::AIO transparently fuses
695	IO::AIO and AnyEvent together.
696
697	=item L<IO::Lambda>
698
699	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
700
701	=back	1206	=back
702		1207
703	=cut	1208	=cut
704		1209
705	package AnyEvent;	1210	package AnyEvent;
706		1211
707	no warnings;	1212	# basically a tuned-down version of common::sense
708	use strict;	1213	sub common_sense {
		1214	# from common:.sense 3.4
		1215	${^WARNING_BITS} ^= ${^WARNING_BITS} ^ "\x3c\x3f\x33\x00\x0f\xf0\x0f\xc0\xf0\xfc\x33\x00";
		1216	# use strict vars subs - NO UTF-8, as Util.pm doesn't like this atm. (uts46data.pl)
		1217	$^H |= 0x00000600;
		1218	}
709		1219
		1220	BEGIN { AnyEvent::common_sense }
		1221
710	use Carp;	1222	use Carp ();
711		1223
712	our $VERSION = '4.03';	1224	our $VERSION = '6.01';
713	our $MODEL;	1225	our $MODEL;
714		1226
715	our $AUTOLOAD;
716	our @ISA;	1227	our @ISA;
717		1228
718	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
719
720	our @REGISTRY;	1229	our @REGISTRY;
721		1230
722	our %PROTOCOL; # (ipv4|ipv6) => (1|2)	1231	our $VERBOSE;
		1232
		1233	BEGIN {
		1234	require "AnyEvent/constants.pl";
		1235
		1236	eval "sub TAINT (){" . (${^TAINT}*1) . "}";
		1237
		1238	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1239	if ${^TAINT};
		1240
		1241	$VERBOSE = $ENV{PERL_ANYEVENT_VERBOSE}*1;
		1242	}
		1243
		1244	our $MAX_SIGNAL_LATENCY = 10;
		1245
		1246	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
723		1247
724	{	1248	{
725	my $idx;	1249	my $idx;
726	$PROTOCOL{$_} = ++$idx	1250	$PROTOCOL{$_} = ++$idx
		1251	for reverse split /\s*,\s*/,
727	for split /\s*,\s*/, $ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";	1252	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
728	}	1253	}
729		1254
		1255	our @post_detect;
		1256
		1257	sub post_detect(&) {
		1258	my ($cb) = @_;
		1259
		1260	push @post_detect, $cb;
		1261
		1262	defined wantarray
		1263	? bless \$cb, "AnyEvent::Util::postdetect"
		1264	: ()
		1265	}
		1266
		1267	sub AnyEvent::Util::postdetect::DESTROY {
		1268	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		1269	}
		1270
		1271	our $POSTPONE_W;
		1272	our @POSTPONE;
		1273
		1274	sub _postpone_exec {
		1275	undef $POSTPONE_W;
		1276
		1277	&{ shift @POSTPONE }
		1278	while @POSTPONE;
		1279	}
		1280
		1281	sub postpone(&) {
		1282	push @POSTPONE, shift;
		1283
		1284	$POSTPONE_W ||= AE::timer (0, 0, \&_postpone_exec);
		1285
		1286	()
		1287	}
		1288
		1289	sub log($$;@) {
		1290	require AnyEvent::Log;
		1291	# AnyEvent::Log overwrites this function
		1292	goto &log;
		1293	}
		1294
730	my @models = (	1295	our @models = (
731	[EV:: => AnyEvent::Impl::EV::],	1296	[EV:: => AnyEvent::Impl::EV:: , 1],
		1297	[AnyEvent::Loop:: => AnyEvent::Impl::Perl:: , 1],
		1298	# everything below here will not (normally) be autoprobed
		1299	# as the pure perl backend should work everywhere
		1300	# and is usually faster
732	[Event:: => AnyEvent::Impl::Event::],	1301	[Event:: => AnyEvent::Impl::Event::, 1],
		1302	[Glib:: => AnyEvent::Impl::Glib:: , 1], # becomes extremely slow with many watchers
		1303	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		1304	[Irssi:: => AnyEvent::Impl::Irssi::], # Irssi has a bogus "Event" package
733	[Tk:: => AnyEvent::Impl::Tk::],	1305	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		1306	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		1307	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
734	[Wx:: => AnyEvent::Impl::POE::],	1308	[Wx:: => AnyEvent::Impl::POE::],
735	[Prima:: => AnyEvent::Impl::POE::],	1309	[Prima:: => AnyEvent::Impl::POE::],
736	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1310	[IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # a bitch to autodetect
737	# everything below here will not be autoprobed as the pureperl backend should work everywhere	1311	[Cocoa::EventLoop:: => AnyEvent::Impl::Cocoa::],
738	[Glib:: => AnyEvent::Impl::Glib::],	1312	[FLTK:: => AnyEvent::Impl::FLTK2::],
739	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
740	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
741	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
742	);	1313	);
743		1314
744	our %method = map +($_ => 1), qw(io timer signal child condvar one_event DESTROY);	1315	our @isa_hook;
745		1316
746	our @post_detect;	1317	sub _isa_set {
		1318	my @pkg = ("AnyEvent", (map $_->[0], grep defined, @isa_hook), $MODEL);
747		1319
		1320	@{"$pkg[$_-1]::ISA"} = $pkg[$_]
		1321	for 1 .. $#pkg;
		1322
		1323	grep $_ && $_->[1], @isa_hook
		1324	and AE::_reset ();
		1325	}
		1326
		1327	# used for hooking AnyEvent::Strict and AnyEvent::Debug::Wrap into the class hierarchy
		1328	sub _isa_hook($$;$) {
		1329	my ($i, $pkg, $reset_ae) = @_;
		1330
		1331	$isa_hook[$i] = $pkg ? [$pkg, $reset_ae] : undef;
		1332
		1333	_isa_set;
		1334	}
		1335
		1336	# all autoloaded methods reserve the complete glob, not just the method slot.
		1337	# due to bugs in perls method cache implementation.
		1338	our @methods = qw(io timer time now now_update signal child idle condvar);
		1339
748	sub post_detect(&) {	1340	sub detect() {
749	my ($cb) = @_;	1341	return $MODEL if $MODEL; # some programs keep references to detect
750		1342
751	if ($MODEL) {	1343	local $!; # for good measure
752	$cb->();	1344	local $SIG{__DIE__}; # we use eval
753		1345
754	1	1346	# free some memory
		1347	*detect = sub () { $MODEL };
		1348	# undef &func doesn't correctly update the method cache. grmbl.
		1349	# so we delete the whole glob. grmbl.
		1350	# otoh, perl doesn't let me undef an active usb, but it lets me free
		1351	# a glob with an active sub. hrm. i hope it works, but perl is
		1352	# usually buggy in this department. sigh.
		1353	delete @{"AnyEvent::"}{@methods};
		1354	undef @methods;
		1355
		1356	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z0-9:]+)$/) {
		1357	my $model = $1;
		1358	$model = "AnyEvent::Impl::$model" unless $model =~ s/::$//;
		1359	if (eval "require $model") {
		1360	$MODEL = $model;
		1361	AnyEvent::log 7 => "loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it."
		1362	if $VERBOSE >= 7;
755	} else {	1363	} else {
756	push @post_detect, $cb;	1364	AnyEvent::log warn => "unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@";
757		1365	}
758	defined wantarray
759	? bless \$cb, "AnyEvent::Util::PostDetect"
760	: ()
761	}	1366	}
762	}
763		1367
764	sub AnyEvent::Util::PostDetect::DESTROY {	1368	# check for already loaded models
765	@post_detect = grep $_ != ${$_[0]}, @post_detect;
766	}
767
768	sub detect() {
769	unless ($MODEL) {	1369	unless ($MODEL) {
770	no strict 'refs';	1370	for (@REGISTRY, @models) {
771		1371	my ($package, $model) = @$_;
772	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	1372	if (${"$package\::VERSION"} > 0) {
773	my $model = "AnyEvent::Impl::$1";
774	if (eval "require $model") {	1373	if (eval "require $model") {
775	$MODEL = $model;	1374	$MODEL = $model;
776	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	1375	AnyEvent::log 7 => "autodetected model '$model', using it."
777	} else {	1376	if $VERBOSE >= 7;
778	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;	1377	last;
		1378	}
779	}	1379	}
780	}	1380	}
781		1381
782	# check for already loaded models
783	unless ($MODEL) {	1382	unless ($MODEL) {
		1383	# try to autoload a model
784	for (@REGISTRY, @models) {	1384	for (@REGISTRY, @models) {
785	my ($package, $model) = @$_;	1385	my ($package, $model, $autoload) = @$_;
		1386	if (
		1387	$autoload
		1388	and eval "require $package"
786	if (${"$package\::VERSION"} > 0) {	1389	and ${"$package\::VERSION"} > 0
787	if (eval "require $model") {	1390	and eval "require $model"
		1391	) {
788	$MODEL = $model;	1392	$MODEL = $model;
789	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;	1393	AnyEvent::log 7 => "autoloaded model '$model', using it."
		1394	if $VERBOSE >= 7;
790	last;	1395	last;
791	}
792	}	1396	}
793	}	1397	}
794		1398
795	unless ($MODEL) {	1399	$MODEL
796	# try to load a model	1400	or die "AnyEvent: backend autodetection failed - did you properly install AnyEvent?";
		1401	}
		1402	}
797		1403
798	for (@REGISTRY, @models) {	1404	# free memory only needed for probing
799	my ($package, $model) = @$_;	1405	undef @models;
800	if (eval "require $package"	1406	undef @REGISTRY;
801	and ${"$package\::VERSION"} > 0	1407
802	and eval "require $model") {	1408	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
803	$MODEL = $model;	1409
804	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;	1410	# now nuke some methods that are overridden by the backend.
		1411	# SUPER usage is not allowed in these.
		1412	for (qw(time signal child idle)) {
		1413	undef &{"AnyEvent::Base::$_"}
		1414	if defined &{"$MODEL\::$_"};
		1415	}
		1416
		1417	_isa_set;
		1418
		1419	# we're officially open!
		1420
		1421	if ($ENV{PERL_ANYEVENT_STRICT}) {
		1422	require AnyEvent::Strict;
		1423	}
		1424
		1425	if ($ENV{PERL_ANYEVENT_DEBUG_WRAP}) {
		1426	require AnyEvent::Debug;
		1427	AnyEvent::Debug::wrap ($ENV{PERL_ANYEVENT_DEBUG_WRAP});
		1428	}
		1429
		1430	if (length $ENV{PERL_ANYEVENT_DEBUG_SHELL}) {
		1431	require AnyEvent::Socket;
		1432	require AnyEvent::Debug;
		1433
		1434	my $shell = $ENV{PERL_ANYEVENT_DEBUG_SHELL};
		1435	$shell =~ s/\$\$/$$/g;
		1436
		1437	my ($host, $service) = AnyEvent::Socket::parse_hostport ($shell);
		1438	$AnyEvent::Debug::SHELL = AnyEvent::Debug::shell ($host, $service);
		1439	}
		1440
		1441	# now the anyevent environment is set up as the user told us to, so
		1442	# call the actual user code - post detects
		1443
		1444	(shift @post_detect)->() while @post_detect;
		1445	undef @post_detect;
		1446
		1447	*post_detect = sub(&) {
		1448	shift->();
		1449
		1450	undef
		1451	};
		1452
		1453	$MODEL
		1454	}
		1455
		1456	for my $name (@methods) {
		1457	*$name = sub {
		1458	detect;
		1459	# we use goto because
		1460	# a) it makes the thunk more transparent
		1461	# b) it allows us to delete the thunk later
		1462	goto &{ UNIVERSAL::can AnyEvent => "SUPER::$name" }
		1463	};
		1464	}
		1465
		1466	# utility function to dup a filehandle. this is used by many backends
		1467	# to support binding more than one watcher per filehandle (they usually
		1468	# allow only one watcher per fd, so we dup it to get a different one).
		1469	sub _dupfh($$;$$) {
		1470	my ($poll, $fh, $r, $w) = @_;
		1471
		1472	# cygwin requires the fh mode to be matching, unix doesn't
		1473	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1474
		1475	open my $fh2, $mode, $fh
		1476	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1477
		1478	# we assume CLOEXEC is already set by perl in all important cases
		1479
		1480	($fh2, $rw)
		1481	}
		1482
		1483	=head1 SIMPLIFIED AE API
		1484
		1485	Starting with version 5.0, AnyEvent officially supports a second, much
		1486	simpler, API that is designed to reduce the calling, typing and memory
		1487	overhead by using function call syntax and a fixed number of parameters.
		1488
		1489	See the L<AE> manpage for details.
		1490
		1491	=cut
		1492
		1493	package AE;
		1494
		1495	our $VERSION = $AnyEvent::VERSION;
		1496
		1497	sub _reset() {
		1498	eval q{
		1499	# fall back to the main API by default - backends and AnyEvent::Base
		1500	# implementations can overwrite these.
		1501
		1502	sub io($$$) {
		1503	AnyEvent->io (fh => $_[0], poll => $_[1] ? "w" : "r", cb => $_[2])
		1504	}
		1505
		1506	sub timer($$$) {
		1507	AnyEvent->timer (after => $_[0], interval => $_[1], cb => $_[2])
		1508	}
		1509
		1510	sub signal($$) {
		1511	AnyEvent->signal (signal => $_[0], cb => $_[1])
		1512	}
		1513
		1514	sub child($$) {
		1515	AnyEvent->child (pid => $_[0], cb => $_[1])
		1516	}
		1517
		1518	sub idle($) {
		1519	AnyEvent->idle (cb => $_[0]);
		1520	}
		1521
		1522	sub cv(;&) {
		1523	AnyEvent->condvar (@_ ? (cb => $_[0]) : ())
		1524	}
		1525
		1526	sub now() {
		1527	AnyEvent->now
		1528	}
		1529
		1530	sub now_update() {
		1531	AnyEvent->now_update
		1532	}
		1533
		1534	sub time() {
		1535	AnyEvent->time
		1536	}
		1537
		1538	*postpone = \&AnyEvent::postpone;
		1539	*log = \&AnyEvent::log;
		1540	};
		1541	die if $@;
		1542	}
		1543
		1544	BEGIN { _reset }
		1545
		1546	package AnyEvent::Base;
		1547
		1548	# default implementations for many methods
		1549
		1550	sub time {
		1551	eval q{ # poor man's autoloading {}
		1552	# probe for availability of Time::HiRes
		1553	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1554	AnyEvent::log 8 => "AnyEvent: using Time::HiRes for sub-second timing accuracy."
		1555	if $AnyEvent::VERBOSE >= 8;
		1556	*time = sub { Time::HiRes::time () };
		1557	*AE::time = \& Time::HiRes::time ;
		1558	# if (eval "use POSIX (); (POSIX::times())...
		1559	} else {
		1560	AnyEvent::log critical => "using built-in time(), WARNING, no sub-second resolution!";
		1561	*time = sub { CORE::time };
		1562	*AE::time = sub (){ CORE::time };
		1563	}
		1564
		1565	*now = \&time;
		1566	};
		1567	die if $@;
		1568
		1569	&time
		1570	}
		1571
		1572	*now = \&time;
		1573	sub now_update { }
		1574
		1575	sub _poll {
		1576	Carp::croak "$AnyEvent::MODEL does not support blocking waits. Caught";
		1577	}
		1578
		1579	# default implementation for ->condvar
		1580	# in fact, the default should not be overwritten
		1581
		1582	sub condvar {
		1583	eval q{ # poor man's autoloading {}
		1584	*condvar = sub {
		1585	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
		1586	};
		1587
		1588	*AE::cv = sub (;&) {
		1589	bless { @_ ? (_ae_cb => shift) : () }, "AnyEvent::CondVar"
		1590	};
		1591	};
		1592	die if $@;
		1593
		1594	&condvar
		1595	}
		1596
		1597	# default implementation for ->signal
		1598
		1599	our $HAVE_ASYNC_INTERRUPT;
		1600
		1601	sub _have_async_interrupt() {
		1602	$HAVE_ASYNC_INTERRUPT = 1*(!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT}
		1603	&& eval "use Async::Interrupt 1.02 (); 1")
		1604	unless defined $HAVE_ASYNC_INTERRUPT;
		1605
		1606	$HAVE_ASYNC_INTERRUPT
		1607	}
		1608
		1609	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1610	our (%SIG_ASY, %SIG_ASY_W);
		1611	our ($SIG_COUNT, $SIG_TW);
		1612
		1613	# install a dummy wakeup watcher to reduce signal catching latency
		1614	# used by Impls
		1615	sub _sig_add() {
		1616	unless ($SIG_COUNT++) {
		1617	# try to align timer on a full-second boundary, if possible
		1618	my $NOW = AE::now;
		1619
		1620	$SIG_TW = AE::timer
		1621	$MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1622	$MAX_SIGNAL_LATENCY,
		1623	sub { } # just for the PERL_ASYNC_CHECK
		1624	;
		1625	}
		1626	}
		1627
		1628	sub _sig_del {
		1629	undef $SIG_TW
		1630	unless --$SIG_COUNT;
		1631	}
		1632
		1633	our $_sig_name_init; $_sig_name_init = sub {
		1634	eval q{ # poor man's autoloading {}
		1635	undef $_sig_name_init;
		1636
		1637	if (_have_async_interrupt) {
		1638	*sig2num = \&Async::Interrupt::sig2num;
		1639	*sig2name = \&Async::Interrupt::sig2name;
		1640	} else {
		1641	require Config;
		1642
		1643	my %signame2num;
		1644	@signame2num{ split ' ', $Config::Config{sig_name} }
		1645	= split ' ', $Config::Config{sig_num};
		1646
		1647	my @signum2name;
		1648	@signum2name[values %signame2num] = keys %signame2num;
		1649
		1650	*sig2num = sub($) {
		1651	$_[0] > 0 ? shift : $signame2num{+shift}
		1652	};
		1653	*sig2name = sub ($) {
		1654	$_[0] > 0 ? $signum2name[+shift] : shift
		1655	};
		1656	}
		1657	};
		1658	die if $@;
		1659	};
		1660
		1661	sub sig2num ($) { &$_sig_name_init; &sig2num }
		1662	sub sig2name($) { &$_sig_name_init; &sig2name }
		1663
		1664	sub signal {
		1665	eval q{ # poor man's autoloading {}
		1666	# probe for availability of Async::Interrupt
		1667	if (_have_async_interrupt) {
		1668	AnyEvent::log 8 => "using Async::Interrupt for race-free signal handling."
		1669	if $AnyEvent::VERBOSE >= 8;
		1670
		1671	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1672	$SIG_IO = AE::io $SIGPIPE_R->fileno, 0, \&_signal_exec;
		1673
		1674	} else {
		1675	AnyEvent::log 8 => "using emulated perl signal handling with latency timer."
		1676	if $AnyEvent::VERBOSE >= 8;
		1677
		1678	if (AnyEvent::WIN32) {
		1679	require AnyEvent::Util;
		1680
		1681	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1682	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R, 1) if $SIGPIPE_R;
		1683	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W, 1) if $SIGPIPE_W; # just in case
		1684	} else {
		1685	pipe $SIGPIPE_R, $SIGPIPE_W;
		1686	fcntl $SIGPIPE_R, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_R;
		1687	fcntl $SIGPIPE_W, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_W; # just in case
		1688
		1689	# not strictly required, as $^F is normally 2, but let's make sure...
		1690	fcntl $SIGPIPE_R, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1691	fcntl $SIGPIPE_W, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1692	}
		1693
		1694	$SIGPIPE_R
		1695	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1696
		1697	$SIG_IO = AE::io $SIGPIPE_R, 0, \&_signal_exec;
		1698	}
		1699
		1700	*signal = $HAVE_ASYNC_INTERRUPT
		1701	? sub {
		1702	my (undef, %arg) = @_;
		1703
		1704	# async::interrupt
		1705	my $signal = sig2num $arg{signal};
		1706	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1707
		1708	$SIG_ASY{$signal} ||= new Async::Interrupt
		1709	cb => sub { undef $SIG_EV{$signal} },
		1710	signal => $signal,
		1711	pipe => [$SIGPIPE_R->filenos],
		1712	pipe_autodrain => 0,
		1713	;
		1714
		1715	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1716	}
		1717	: sub {
		1718	my (undef, %arg) = @_;
		1719
		1720	# pure perl
		1721	my $signal = sig2name $arg{signal};
		1722	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1723
		1724	$SIG{$signal} ||= sub {
805	last;	1725	local $!;
		1726	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1727	undef $SIG_EV{$signal};
806	}	1728	};
		1729
		1730	# can't do signal processing without introducing races in pure perl,
		1731	# so limit the signal latency.
		1732	_sig_add;
		1733
		1734	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1735	}
		1736	;
		1737
		1738	*AnyEvent::Base::signal::DESTROY = sub {
		1739	my ($signal, $cb) = @{$_[0]};
		1740
		1741	_sig_del;
		1742
		1743	delete $SIG_CB{$signal}{$cb};
		1744
		1745	$HAVE_ASYNC_INTERRUPT
		1746	? delete $SIG_ASY{$signal}
		1747	: # delete doesn't work with older perls - they then
		1748	# print weird messages, or just unconditionally exit
		1749	# instead of getting the default action.
		1750	undef $SIG{$signal}
		1751	unless keys %{ $SIG_CB{$signal} };
		1752	};
		1753
		1754	*_signal_exec = sub {
		1755	$HAVE_ASYNC_INTERRUPT
		1756	? $SIGPIPE_R->drain
		1757	: sysread $SIGPIPE_R, (my $dummy), 9;
		1758
		1759	while (%SIG_EV) {
		1760	for (keys %SIG_EV) {
		1761	delete $SIG_EV{$_};
		1762	&$_ for values %{ $SIG_CB{$_} || {} };
807	}	1763	}
808
809	$MODEL
810	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.";
811	}	1764	}
812	}	1765	};
813
814	unshift @ISA, $MODEL;
815	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
816
817	(shift @post_detect)->() while @post_detect;
818	}
819
820	$MODEL
821	}
822
823	sub AUTOLOAD {
824	(my $func = $AUTOLOAD) =~ s/.*://;
825
826	$method{$func}
827	or croak "$func: not a valid method for AnyEvent objects";
828
829	detect unless $MODEL;
830
831	my $class = shift;
832	$class->$func (@_);
833	}
834
835	package AnyEvent::Base;
836
837	# default implementation for ->condvar
838
839	sub condvar {
840	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, AnyEvent::CondVar::
841	}
842
843	# default implementation for ->signal
844
845	our %SIG_CB;
846
847	sub signal {
848	my (undef, %arg) = @_;
849
850	my $signal = uc $arg{signal}
851	or Carp::croak "required option 'signal' is missing";
852
853	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
854	$SIG{$signal} ||= sub {
855	$_->() for values %{ $SIG_CB{$signal} || {} };
856	};	1766	};
		1767	die if $@;
857		1768
858	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1769	&signal
859	}
860
861	sub AnyEvent::Base::Signal::DESTROY {
862	my ($signal, $cb) = @{$_[0]};
863
864	delete $SIG_CB{$signal}{$cb};
865
866	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };
867	}	1770	}
868		1771
869	# default implementation for ->child	1772	# default implementation for ->child
870		1773
871	our %PID_CB;	1774	our %PID_CB;
872	our $CHLD_W;	1775	our $CHLD_W;
873	our $CHLD_DELAY_W;	1776	our $CHLD_DELAY_W;
874	our $PID_IDLE;
875	our $WNOHANG;
876		1777
877	sub _child_wait {	1778	# used by many Impl's
878	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1779	sub _emit_childstatus($$) {
		1780	my (undef, $rpid, $rstatus) = @_;
		1781
		1782	$_->($rpid, $rstatus)
879	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1783	for values %{ $PID_CB{$rpid} || {} },
880	(values %{ $PID_CB{0} || {} });	1784	values %{ $PID_CB{0} || {} };
881	}
882
883	undef $PID_IDLE;
884	}
885
886	sub _sigchld {
887	# make sure we deliver these changes "synchronous" with the event loop.
888	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {
889	undef $CHLD_DELAY_W;
890	&_child_wait;
891	});
892	}	1785	}
893		1786
894	sub child {	1787	sub child {
		1788	eval q{ # poor man's autoloading {}
		1789	*_sigchld = sub {
		1790	my $pid;
		1791
		1792	AnyEvent->_emit_childstatus ($pid, $?)
		1793	while ($pid = waitpid -1, WNOHANG) > 0;
		1794	};
		1795
		1796	*child = sub {
895	my (undef, %arg) = @_;	1797	my (undef, %arg) = @_;
896		1798
897	defined (my $pid = $arg{pid} + 0)	1799	my $pid = $arg{pid};
898	or Carp::croak "required option 'pid' is missing";	1800	my $cb = $arg{cb};
899		1801
900	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1802	$PID_CB{$pid}{$cb+0} = $cb;
901		1803
902	unless ($WNOHANG) {
903	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;
904	}
905
906	unless ($CHLD_W) {	1804	unless ($CHLD_W) {
907	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1805	$CHLD_W = AE::signal CHLD => \&_sigchld;
908	# child could be a zombie already, so make at least one round	1806	# child could be a zombie already, so make at least one round
909	&_sigchld;	1807	&_sigchld;
910	}	1808	}
911		1809
912	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	1810	bless [$pid, $cb+0], "AnyEvent::Base::child"
913	}	1811	};
914		1812
915	sub AnyEvent::Base::Child::DESTROY {	1813	*AnyEvent::Base::child::DESTROY = sub {
916	my ($pid, $cb) = @{$_[0]};	1814	my ($pid, $icb) = @{$_[0]};
917		1815
918	delete $PID_CB{$pid}{$cb};	1816	delete $PID_CB{$pid}{$icb};
919	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1817	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
920		1818
921	undef $CHLD_W unless keys %PID_CB;	1819	undef $CHLD_W unless keys %PID_CB;
		1820	};
		1821	};
		1822	die if $@;
		1823
		1824	&child
		1825	}
		1826
		1827	# idle emulation is done by simply using a timer, regardless
		1828	# of whether the process is idle or not, and not letting
		1829	# the callback use more than 50% of the time.
		1830	sub idle {
		1831	eval q{ # poor man's autoloading {}
		1832	*idle = sub {
		1833	my (undef, %arg) = @_;
		1834
		1835	my ($cb, $w, $rcb) = $arg{cb};
		1836
		1837	$rcb = sub {
		1838	if ($cb) {
		1839	$w = AE::time;
		1840	&$cb;
		1841	$w = AE::time - $w;
		1842
		1843	# never use more then 50% of the time for the idle watcher,
		1844	# within some limits
		1845	$w = 0.0001 if $w < 0.0001;
		1846	$w = 5 if $w > 5;
		1847
		1848	$w = AE::timer $w, 0, $rcb;
		1849	} else {
		1850	# clean up...
		1851	undef $w;
		1852	undef $rcb;
		1853	}
		1854	};
		1855
		1856	$w = AE::timer 0.05, 0, $rcb;
		1857
		1858	bless \\$cb, "AnyEvent::Base::idle"
		1859	};
		1860
		1861	*AnyEvent::Base::idle::DESTROY = sub {
		1862	undef $${$_[0]};
		1863	};
		1864	};
		1865	die if $@;
		1866
		1867	&idle
922	}	1868	}
923		1869
924	package AnyEvent::CondVar;	1870	package AnyEvent::CondVar;
925		1871
926	our @ISA = AnyEvent::CondVar::Base::;	1872	our @ISA = AnyEvent::CondVar::Base::;
927		1873
		1874	# only to be used for subclassing
		1875	sub new {
		1876	my $class = shift;
		1877	bless AnyEvent->condvar (@_), $class
		1878	}
		1879
928	package AnyEvent::CondVar::Base;	1880	package AnyEvent::CondVar::Base;
929		1881
930	use overload	1882	#use overload
931	'&{}' => sub { my $self = shift; sub { $self->send (@_) } },	1883	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
932	fallback => 1;	1884	# fallback => 1;
		1885
		1886	# save 300+ kilobytes by dirtily hardcoding overloading
		1887	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1888	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1889	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1890	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1891
		1892	our $WAITING;
933		1893
934	sub _send {	1894	sub _send {
935	# nop	1895	# nop
		1896	}
		1897
		1898	sub _wait {
		1899	AnyEvent->_poll until $_[0]{_ae_sent};
936	}	1900	}
937		1901
938	sub send {	1902	sub send {
939	my $cv = shift;	1903	my $cv = shift;
940	$cv->{_ae_sent} = [@_];	1904	$cv->{_ae_sent} = [@_];
…		…
949		1913
950	sub ready {	1914	sub ready {
951	$_[0]{_ae_sent}	1915	$_[0]{_ae_sent}
952	}	1916	}
953		1917
954	sub _wait {
955	AnyEvent->one_event while !$_[0]{_ae_sent};
956	}
957
958	sub recv {	1918	sub recv {
		1919	unless ($_[0]{_ae_sent}) {
		1920	$WAITING
		1921	and Carp::croak "AnyEvent::CondVar: recursive blocking wait attempted";
		1922
		1923	local $WAITING = 1;
959	$_[0]->_wait;	1924	$_[0]->_wait;
		1925	}
960		1926
961	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};	1927	$_[0]{_ae_croak}
962	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]	1928	and Carp::croak $_[0]{_ae_croak};
		1929
		1930	wantarray
		1931	? @{ $_[0]{_ae_sent} }
		1932	: $_[0]{_ae_sent}[0]
963	}	1933	}
964		1934
965	sub cb {	1935	sub cb {
966	$_[0]{_ae_cb} = $_[1] if @_ > 1;	1936	my $cv = shift;
		1937
		1938	@_
		1939	and $cv->{_ae_cb} = shift
		1940	and $cv->{_ae_sent}
		1941	and (delete $cv->{_ae_cb})->($cv);
		1942
967	$_[0]{_ae_cb}	1943	$cv->{_ae_cb}
968	}	1944	}
969		1945
970	sub begin {	1946	sub begin {
971	++$_[0]{_ae_counter};	1947	++$_[0]{_ae_counter};
972	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;	1948	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
…		…
977	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };	1953	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
978	}	1954	}
979		1955
980	# undocumented/compatibility with pre-3.4	1956	# undocumented/compatibility with pre-3.4
981	*broadcast = \&send;	1957	*broadcast = \&send;
982	*wait = \&_wait;	1958	*wait = \&recv;
		1959
		1960	=head1 ERROR AND EXCEPTION HANDLING
		1961
		1962	In general, AnyEvent does not do any error handling - it relies on the
		1963	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1964	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1965	checking of all AnyEvent methods, however, which is highly useful during
		1966	development.
		1967
		1968	As for exception handling (i.e. runtime errors and exceptions thrown while
		1969	executing a callback), this is not only highly event-loop specific, but
		1970	also not in any way wrapped by this module, as this is the job of the main
		1971	program.
		1972
		1973	The pure perl event loop simply re-throws the exception (usually
		1974	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1975	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1976	so on.
		1977
		1978	=head1 ENVIRONMENT VARIABLES
		1979
		1980	The following environment variables are used by this module or its
		1981	submodules.
		1982
		1983	Note that AnyEvent will remove I<all> environment variables starting with
		1984	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		1985	enabled.
		1986
		1987	=over 4
		1988
		1989	=item C<PERL_ANYEVENT_VERBOSE>
		1990
		1991	By default, AnyEvent will be completely silent except in fatal
		1992	conditions. You can set this environment variable to make AnyEvent more
		1993	talkative.
		1994
		1995	When set to C<5> or higher, causes AnyEvent to warn about unexpected
		1996	conditions, such as not being able to load the event model specified by
		1997	C<PERL_ANYEVENT_MODEL>.
		1998
		1999	When set to C<7> or higher, cause AnyEvent to report to STDERR which event
		2000	model it chooses.
		2001
		2002	When set to C<8> or higher, then AnyEvent will report extra information on
		2003	which optional modules it loads and how it implements certain features.
		2004
		2005	=item C<PERL_ANYEVENT_STRICT>
		2006
		2007	AnyEvent does not do much argument checking by default, as thorough
		2008	argument checking is very costly. Setting this variable to a true value
		2009	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		2010	check the arguments passed to most method calls. If it finds any problems,
		2011	it will croak.
		2012
		2013	In other words, enables "strict" mode.
		2014
		2015	Unlike C<use strict> (or its modern cousin, C<< use L<common::sense>
		2016	>>, it is definitely recommended to keep it off in production. Keeping
		2017	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		2018	can be very useful, however.
		2019
		2020	=item C<PERL_ANYEVENT_DEBUG_SHELL>
		2021
		2022	If this env variable is set, then its contents will be interpreted by
		2023	C<AnyEvent::Socket::parse_hostport> (after replacing every occurance of
		2024	C<$$> by the process pid) and an C<AnyEvent::Debug::shell> is bound on
		2025	that port. The shell object is saved in C<$AnyEvent::Debug::SHELL>.
		2026
		2027	This takes place when the first watcher is created.
		2028
		2029	For example, to bind a debug shell on a unix domain socket in
		2030	F<< /tmp/debug<pid>.sock >>, you could use this:
		2031
		2032	PERL_ANYEVENT_DEBUG_SHELL=/tmp/debug\$\$.sock perlprog
		2033
		2034	Note that creating sockets in F</tmp> is very unsafe on multiuser
		2035	systems.
		2036
		2037	=item C<PERL_ANYEVENT_DEBUG_WRAP>
		2038
		2039	Can be set to C<0>, C<1> or C<2> and enables wrapping of all watchers for
		2040	debugging purposes. See C<AnyEvent::Debug::wrap> for details.
		2041
		2042	=item C<PERL_ANYEVENT_MODEL>
		2043
		2044	This can be used to specify the event model to be used by AnyEvent, before
		2045	auto detection and -probing kicks in.
		2046
		2047	It normally is a string consisting entirely of ASCII letters (e.g. C<EV>
		2048	or C<IOAsync>). The string C<AnyEvent::Impl::> gets prepended and the
		2049	resulting module name is loaded and - if the load was successful - used as
		2050	event model backend. If it fails to load then AnyEvent will proceed with
		2051	auto detection and -probing.
		2052
		2053	If the string ends with C<::> instead (e.g. C<AnyEvent::Impl::EV::>) then
		2054	nothing gets prepended and the module name is used as-is (hint: C<::> at
		2055	the end of a string designates a module name and quotes it appropriately).
		2056
		2057	For example, to force the pure perl model (L<AnyEvent::Loop::Perl>) you
		2058	could start your program like this:
		2059
		2060	PERL_ANYEVENT_MODEL=Perl perl ...
		2061
		2062	=item C<PERL_ANYEVENT_PROTOCOLS>
		2063
		2064	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		2065	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		2066	of auto probing).
		2067
		2068	Must be set to a comma-separated list of protocols or address families,
		2069	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		2070	used, and preference will be given to protocols mentioned earlier in the
		2071	list.
		2072
		2073	This variable can effectively be used for denial-of-service attacks
		2074	against local programs (e.g. when setuid), although the impact is likely
		2075	small, as the program has to handle conenction and other failures anyways.
		2076
		2077	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		2078	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		2079	- only support IPv4, never try to resolve or contact IPv6
		2080	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		2081	IPv6, but prefer IPv6 over IPv4.
		2082
		2083	=item C<PERL_ANYEVENT_EDNS0>
		2084
		2085	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		2086	for DNS. This extension is generally useful to reduce DNS traffic, but
		2087	some (broken) firewalls drop such DNS packets, which is why it is off by
		2088	default.
		2089
		2090	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		2091	EDNS0 in its DNS requests.
		2092
		2093	=item C<PERL_ANYEVENT_MAX_FORKS>
		2094
		2095	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		2096	will create in parallel.
		2097
		2098	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		2099
		2100	The default value for the C<max_outstanding> parameter for the default DNS
		2101	resolver - this is the maximum number of parallel DNS requests that are
		2102	sent to the DNS server.
		2103
		2104	=item C<PERL_ANYEVENT_RESOLV_CONF>
		2105
		2106	The file to use instead of F</etc/resolv.conf> (or OS-specific
		2107	configuration) in the default resolver. When set to the empty string, no
		2108	default config will be used.
		2109
		2110	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		2111
		2112	When neither C<ca_file> nor C<ca_path> was specified during
		2113	L<AnyEvent::TLS> context creation, and either of these environment
		2114	variables exist, they will be used to specify CA certificate locations
		2115	instead of a system-dependent default.
		2116
		2117	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		2118
		2119	When these are set to C<1>, then the respective modules are not
		2120	loaded. Mostly good for testing AnyEvent itself.
		2121
		2122	=back
983		2123
984	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	2124	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
985		2125
986	This is an advanced topic that you do not normally need to use AnyEvent in	2126	This is an advanced topic that you do not normally need to use AnyEvent in
987	a module. This section is only of use to event loop authors who want to	2127	a module. This section is only of use to event loop authors who want to
…		…
1021		2161
1022	I<rxvt-unicode> also cheats a bit by not providing blocking access to	2162	I<rxvt-unicode> also cheats a bit by not providing blocking access to
1023	condition variables: code blocking while waiting for a condition will	2163	condition variables: code blocking while waiting for a condition will
1024	C<die>. This still works with most modules/usages, and blocking calls must	2164	C<die>. This still works with most modules/usages, and blocking calls must
1025	not be done in an interactive application, so it makes sense.	2165	not be done in an interactive application, so it makes sense.
1026
1027	=head1 ENVIRONMENT VARIABLES
1028
1029	The following environment variables are used by this module:
1030
1031	=over 4
1032
1033	=item C<PERL_ANYEVENT_VERBOSE>
1034
1035	By default, AnyEvent will be completely silent except in fatal
1036	conditions. You can set this environment variable to make AnyEvent more
1037	talkative.
1038
1039	When set to C<1> or higher, causes AnyEvent to warn about unexpected
1040	conditions, such as not being able to load the event model specified by
1041	C<PERL_ANYEVENT_MODEL>.
1042
1043	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
1044	model it chooses.
1045
1046	=item C<PERL_ANYEVENT_MODEL>
1047
1048	This can be used to specify the event model to be used by AnyEvent, before
1049	auto detection and -probing kicks in. It must be a string consisting
1050	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
1051	and the resulting module name is loaded and if the load was successful,
1052	used as event model. If it fails to load AnyEvent will proceed with
1053	auto detection and -probing.
1054
1055	This functionality might change in future versions.
1056
1057	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
1058	could start your program like this:
1059
1060	PERL_ANYEVENT_MODEL=Perl perl ...
1061
1062	=item C<PERL_ANYEVENT_PROTOCOLS>
1063
1064	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
1065	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
1066	of auto probing).
1067
1068	Must be set to a comma-separated list of protocols or address families,
1069	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
1070	used, and preference will be given to protocols mentioned earlier in the
1071	list.
1072
1073	This variable can effectively be used for denial-of-service attacks
1074	against local programs (e.g. when setuid), although the impact is likely
1075	small, as the program has to handle connection errors already-
1076
1077	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
1078	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
1079	- only support IPv4, never try to resolve or contact IPv6
1080	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
1081	IPv6, but prefer IPv6 over IPv4.
1082
1083	=item C<PERL_ANYEVENT_EDNS0>
1084
1085	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
1086	for DNS. This extension is generally useful to reduce DNS traffic, but
1087	some (broken) firewalls drop such DNS packets, which is why it is off by
1088	default.
1089
1090	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
1091	EDNS0 in its DNS requests.
1092
1093	=back
1094		2166
1095	=head1 EXAMPLE PROGRAM	2167	=head1 EXAMPLE PROGRAM
1096		2168
1097	The following program uses an I/O watcher to read data from STDIN, a timer	2169	The following program uses an I/O watcher to read data from STDIN, a timer
1098	to display a message once per second, and a condition variable to quit the	2170	to display a message once per second, and a condition variable to quit the
…		…
1111	warn "read: $input\n"; # output what has been read	2183	warn "read: $input\n"; # output what has been read
1112	$cv->send if $input =~ /^q/i; # quit program if /^q/i	2184	$cv->send if $input =~ /^q/i; # quit program if /^q/i
1113	},	2185	},
1114	);	2186	);
1115		2187
1116	my $time_watcher; # can only be used once
1117
1118	sub new_timer {
1119	$timer = AnyEvent->timer (after => 1, cb => sub {	2188	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
1120	warn "timeout\n"; # print 'timeout' about every second	2189	warn "timeout\n"; # print 'timeout' at most every second
1121	&new_timer; # and restart the time
1122	});	2190	});
1123	}
1124
1125	new_timer; # create first timer
1126		2191
1127	$cv->recv; # wait until user enters /^q/i	2192	$cv->recv; # wait until user enters /^q/i
1128		2193
1129	=head1 REAL-WORLD EXAMPLE	2194	=head1 REAL-WORLD EXAMPLE
1130		2195
…		…
1203		2268
1204	The actual code goes further and collects all errors (C<die>s, exceptions)	2269	The actual code goes further and collects all errors (C<die>s, exceptions)
1205	that occurred during request processing. The C<result> method detects	2270	that occurred during request processing. The C<result> method detects
1206	whether an exception as thrown (it is stored inside the $txn object)	2271	whether an exception as thrown (it is stored inside the $txn object)
1207	and just throws the exception, which means connection errors and other	2272	and just throws the exception, which means connection errors and other
1208	problems get reported tot he code that tries to use the result, not in a	2273	problems get reported to the code that tries to use the result, not in a
1209	random callback.	2274	random callback.
1210		2275
1211	All of this enables the following usage styles:	2276	All of this enables the following usage styles:
1212		2277
1213	1. Blocking:	2278	1. Blocking:
…		…
1261	through AnyEvent. The benchmark creates a lot of timers (with a zero	2326	through AnyEvent. The benchmark creates a lot of timers (with a zero
1262	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,	2327	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
1263	which it is), lets them fire exactly once and destroys them again.	2328	which it is), lets them fire exactly once and destroys them again.
1264		2329
1265	Source code for this benchmark is found as F<eg/bench> in the AnyEvent	2330	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
1266	distribution.	2331	distribution. It uses the L<AE> interface, which makes a real difference
		2332	for the EV and Perl backends only.
1267		2333
1268	=head3 Explanation of the columns	2334	=head3 Explanation of the columns
1269		2335
1270	I<watcher> is the number of event watchers created/destroyed. Since	2336	I<watcher> is the number of event watchers created/destroyed. Since
1271	different event models feature vastly different performances, each event	2337	different event models feature vastly different performances, each event
…		…
1292	watcher.	2358	watcher.
1293		2359
1294	=head3 Results	2360	=head3 Results
1295		2361
1296	name watchers bytes create invoke destroy comment	2362	name watchers bytes create invoke destroy comment
1297	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	2363	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
1298	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	2364	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
1299	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	2365	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
1300	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	2366	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
1301	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	2367	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
1302	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers	2368	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
		2369	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
		2370	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
1303	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	2371	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
1304	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	2372	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
1305	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	2373	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
1306	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	2374	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
1307		2375
1308	=head3 Discussion	2376	=head3 Discussion
1309		2377
1310	The benchmark does I<not> measure scalability of the event loop very	2378	The benchmark does I<not> measure scalability of the event loop very
1311	well. For example, a select-based event loop (such as the pure perl one)	2379	well. For example, a select-based event loop (such as the pure perl one)
…		…
1323	benchmark machine, handling an event takes roughly 1600 CPU cycles with	2391	benchmark machine, handling an event takes roughly 1600 CPU cycles with
1324	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU	2392	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
1325	cycles with POE.	2393	cycles with POE.
1326		2394
1327	C<EV> is the sole leader regarding speed and memory use, which are both	2395	C<EV> is the sole leader regarding speed and memory use, which are both
1328	maximal/minimal, respectively. Even when going through AnyEvent, it uses	2396	maximal/minimal, respectively. When using the L<AE> API there is zero
		2397	overhead (when going through the AnyEvent API create is about 5-6 times
		2398	slower, with other times being equal, so still uses far less memory than
1329	far less memory than any other event loop and is still faster than Event	2399	any other event loop and is still faster than Event natively).
1330	natively.
1331		2400
1332	The pure perl implementation is hit in a few sweet spots (both the	2401	The pure perl implementation is hit in a few sweet spots (both the
1333	constant timeout and the use of a single fd hit optimisations in the perl	2402	constant timeout and the use of a single fd hit optimisations in the perl
1334	interpreter and the backend itself). Nevertheless this shows that it	2403	interpreter and the backend itself). Nevertheless this shows that it
1335	adds very little overhead in itself. Like any select-based backend its	2404	adds very little overhead in itself. Like any select-based backend its
1336	performance becomes really bad with lots of file descriptors (and few of	2405	performance becomes really bad with lots of file descriptors (and few of
1337	them active), of course, but this was not subject of this benchmark.	2406	them active), of course, but this was not subject of this benchmark.
1338		2407
1339	The C<Event> module has a relatively high setup and callback invocation	2408	The C<Event> module has a relatively high setup and callback invocation
1340	cost, but overall scores in on the third place.	2409	cost, but overall scores in on the third place.
		2410
		2411	C<IO::Async> performs admirably well, about on par with C<Event>, even
		2412	when using its pure perl backend.
1341		2413
1342	C<Glib>'s memory usage is quite a bit higher, but it features a	2414	C<Glib>'s memory usage is quite a bit higher, but it features a
1343	faster callback invocation and overall ends up in the same class as	2415	faster callback invocation and overall ends up in the same class as
1344	C<Event>. However, Glib scales extremely badly, doubling the number of	2416	C<Event>. However, Glib scales extremely badly, doubling the number of
1345	watchers increases the processing time by more than a factor of four,	2417	watchers increases the processing time by more than a factor of four,
…		…
1380	(even when used without AnyEvent), but most event loops have acceptable	2452	(even when used without AnyEvent), but most event loops have acceptable
1381	performance with or without AnyEvent.	2453	performance with or without AnyEvent.
1382		2454
1383	=item * The overhead AnyEvent adds is usually much smaller than the overhead of	2455	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
1384	the actual event loop, only with extremely fast event loops such as EV	2456	the actual event loop, only with extremely fast event loops such as EV
1385	adds AnyEvent significant overhead.	2457	does AnyEvent add significant overhead.
1386		2458
1387	=item * You should avoid POE like the plague if you want performance or	2459	=item * You should avoid POE like the plague if you want performance or
1388	reasonable memory usage.	2460	reasonable memory usage.
1389		2461
1390	=back	2462	=back
…		…
1406	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100	2478	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
1407	(1%) are active. This mirrors the activity of large servers with many	2479	(1%) are active. This mirrors the activity of large servers with many
1408	connections, most of which are idle at any one point in time.	2480	connections, most of which are idle at any one point in time.
1409		2481
1410	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent	2482	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
1411	distribution.	2483	distribution. It uses the L<AE> interface, which makes a real difference
		2484	for the EV and Perl backends only.
1412		2485
1413	=head3 Explanation of the columns	2486	=head3 Explanation of the columns
1414		2487
1415	I<sockets> is the number of sockets, and twice the number of "servers" (as	2488	I<sockets> is the number of sockets, and twice the number of "servers" (as
1416	each server has a read and write socket end).	2489	each server has a read and write socket end).
…		…
1423	it to another server. This includes deleting the old timeout and creating	2496	it to another server. This includes deleting the old timeout and creating
1424	a new one that moves the timeout into the future.	2497	a new one that moves the timeout into the future.
1425		2498
1426	=head3 Results	2499	=head3 Results
1427		2500
1428	name sockets create request	2501	name sockets create request
1429	EV 20000 69.01 11.16	2502	EV 20000 62.66 7.99
1430	Perl 20000 73.32 35.87	2503	Perl 20000 68.32 32.64
1431	Event 20000 212.62 257.32	2504	IOAsync 20000 174.06 101.15 epoll
1432	Glib 20000 651.16 1896.30	2505	IOAsync 20000 174.67 610.84 poll
		2506	Event 20000 202.69 242.91
		2507	Glib 20000 557.01 1689.52
1433	POE 20000 349.67 12317.24 uses POE::Loop::Event	2508	POE 20000 341.54 12086.32 uses POE::Loop::Event
1434		2509
1435	=head3 Discussion	2510	=head3 Discussion
1436		2511
1437	This benchmark I<does> measure scalability and overall performance of the	2512	This benchmark I<does> measure scalability and overall performance of the
1438	particular event loop.	2513	particular event loop.
…		…
1440	EV is again fastest. Since it is using epoll on my system, the setup time	2515	EV is again fastest. Since it is using epoll on my system, the setup time
1441	is relatively high, though.	2516	is relatively high, though.
1442		2517
1443	Perl surprisingly comes second. It is much faster than the C-based event	2518	Perl surprisingly comes second. It is much faster than the C-based event
1444	loops Event and Glib.	2519	loops Event and Glib.
		2520
		2521	IO::Async performs very well when using its epoll backend, and still quite
		2522	good compared to Glib when using its pure perl backend.
1445		2523
1446	Event suffers from high setup time as well (look at its code and you will	2524	Event suffers from high setup time as well (look at its code and you will
1447	understand why). Callback invocation also has a high overhead compared to	2525	understand why). Callback invocation also has a high overhead compared to
1448	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event	2526	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
1449	uses select or poll in basically all documented configurations.	2527	uses select or poll in basically all documented configurations.
…		…
1512	=item * C-based event loops perform very well with small number of	2590	=item * C-based event loops perform very well with small number of
1513	watchers, as the management overhead dominates.	2591	watchers, as the management overhead dominates.
1514		2592
1515	=back	2593	=back
1516		2594
		2595	=head2 THE IO::Lambda BENCHMARK
		2596
		2597	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2598	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2599	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2600	shouldn't come as a surprise to anybody). As such, the benchmark is
		2601	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2602	very optimal. But how would AnyEvent compare when used without the extra
		2603	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2604
		2605	The benchmark itself creates an echo-server, and then, for 500 times,
		2606	connects to the echo server, sends a line, waits for the reply, and then
		2607	creates the next connection. This is a rather bad benchmark, as it doesn't
		2608	test the efficiency of the framework or much non-blocking I/O, but it is a
		2609	benchmark nevertheless.
		2610
		2611	name runtime
		2612	Lambda/select 0.330 sec
		2613	+ optimized 0.122 sec
		2614	Lambda/AnyEvent 0.327 sec
		2615	+ optimized 0.138 sec
		2616	Raw sockets/select 0.077 sec
		2617	POE/select, components 0.662 sec
		2618	POE/select, raw sockets 0.226 sec
		2619	POE/select, optimized 0.404 sec
		2620
		2621	AnyEvent/select/nb 0.085 sec
		2622	AnyEvent/EV/nb 0.068 sec
		2623	+state machine 0.134 sec
		2624
		2625	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2626	benchmarks actually make blocking connects and use 100% blocking I/O,
		2627	defeating the purpose of an event-based solution. All of the newly
		2628	written AnyEvent benchmarks use 100% non-blocking connects (using
		2629	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2630	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2631	generally require a lot more bookkeeping and event handling than blocking
		2632	connects (which involve a single syscall only).
		2633
		2634	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2635	offers similar expressive power as POE and IO::Lambda, using conventional
		2636	Perl syntax. This means that both the echo server and the client are 100%
		2637	non-blocking, further placing it at a disadvantage.
		2638
		2639	As you can see, the AnyEvent + EV combination even beats the
		2640	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2641	backend easily beats IO::Lambda and POE.
		2642
		2643	And even the 100% non-blocking version written using the high-level (and
		2644	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda
		2645	higher level ("unoptimised") abstractions by a large margin, even though
		2646	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
		2647
		2648	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2649	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2650	part of the IO::Lambda distribution and were used without any changes.
		2651
		2652
		2653	=head1 SIGNALS
		2654
		2655	AnyEvent currently installs handlers for these signals:
		2656
		2657	=over 4
		2658
		2659	=item SIGCHLD
		2660
		2661	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2662	emulation for event loops that do not support them natively. Also, some
		2663	event loops install a similar handler.
		2664
		2665	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2666	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2667
		2668	=item SIGPIPE
		2669
		2670	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2671	when AnyEvent gets loaded.
		2672
		2673	The rationale for this is that AnyEvent users usually do not really depend
		2674	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2675	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2676	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2677	some random socket.
		2678
		2679	The rationale for installing a no-op handler as opposed to ignoring it is
		2680	that this way, the handler will be restored to defaults on exec.
		2681
		2682	Feel free to install your own handler, or reset it to defaults.
		2683
		2684	=back
		2685
		2686	=cut
		2687
		2688	undef $SIG{CHLD}
		2689	if $SIG{CHLD} eq 'IGNORE';
		2690
		2691	$SIG{PIPE} = sub { }
		2692	unless defined $SIG{PIPE};
		2693
		2694	=head1 RECOMMENDED/OPTIONAL MODULES
		2695
		2696	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2697	its built-in modules) are required to use it.
		2698
		2699	That does not mean that AnyEvent won't take advantage of some additional
		2700	modules if they are installed.
		2701
		2702	This section explains which additional modules will be used, and how they
		2703	affect AnyEvent's operation.
		2704
		2705	=over 4
		2706
		2707	=item L<Async::Interrupt>
		2708
		2709	This slightly arcane module is used to implement fast signal handling: To
		2710	my knowledge, there is no way to do completely race-free and quick
		2711	signal handling in pure perl. To ensure that signals still get
		2712	delivered, AnyEvent will start an interval timer to wake up perl (and
		2713	catch the signals) with some delay (default is 10 seconds, look for
		2714	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2715
		2716	If this module is available, then it will be used to implement signal
		2717	catching, which means that signals will not be delayed, and the event loop
		2718	will not be interrupted regularly, which is more efficient (and good for
		2719	battery life on laptops).
		2720
		2721	This affects not just the pure-perl event loop, but also other event loops
		2722	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2723
		2724	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2725	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2726	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2727	does nothing for those backends.
		2728
		2729	=item L<EV>
		2730
		2731	This module isn't really "optional", as it is simply one of the backend
		2732	event loops that AnyEvent can use. However, it is simply the best event
		2733	loop available in terms of features, speed and stability: It supports
		2734	the AnyEvent API optimally, implements all the watcher types in XS, does
		2735	automatic timer adjustments even when no monotonic clock is available,
		2736	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2737	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2738	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2739
		2740	If you only use backends that rely on another event loop (e.g. C<Tk>),
		2741	then this module will do nothing for you.
		2742
		2743	=item L<Guard>
		2744
		2745	The guard module, when used, will be used to implement
		2746	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2747	lot less memory), but otherwise doesn't affect guard operation much. It is
		2748	purely used for performance.
		2749
		2750	=item L<JSON> and L<JSON::XS>
		2751
		2752	One of these modules is required when you want to read or write JSON data
		2753	via L<AnyEvent::Handle>. L<JSON> is also written in pure-perl, but can take
		2754	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2755
		2756	=item L<Net::SSLeay>
		2757
		2758	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2759	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2760	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2761
		2762	=item L<Time::HiRes>
		2763
		2764	This module is part of perl since release 5.008. It will be used when the
		2765	chosen event library does not come with a timing source of its own. The
		2766	pure-perl event loop (L<AnyEvent::Loop>) will additionally load it to
		2767	try to use a monotonic clock for timing stability.
		2768
		2769	=back
		2770
1517		2771
1518	=head1 FORK	2772	=head1 FORK
1519		2773
1520	Most event libraries are not fork-safe. The ones who are usually are	2774	Most event libraries are not fork-safe. The ones who are usually are
1521	because they rely on inefficient but fork-safe C<select> or C<poll>	2775	because they rely on inefficient but fork-safe C<select> or C<poll> calls
1522	calls. Only L<EV> is fully fork-aware.	2776	- higher performance APIs such as BSD's kqueue or the dreaded Linux epoll
		2777	are usually badly thought-out hacks that are incompatible with fork in
		2778	one way or another. Only L<EV> is fully fork-aware and ensures that you
		2779	continue event-processing in both parent and child (or both, if you know
		2780	what you are doing).
		2781
		2782	This means that, in general, you cannot fork and do event processing in
		2783	the child if the event library was initialised before the fork (which
		2784	usually happens when the first AnyEvent watcher is created, or the library
		2785	is loaded).
1523		2786
1524	If you have to fork, you must either do so I<before> creating your first	2787	If you have to fork, you must either do so I<before> creating your first
1525	watcher OR you must not use AnyEvent at all in the child.	2788	watcher OR you must not use AnyEvent at all in the child OR you must do
		2789	something completely out of the scope of AnyEvent.
		2790
		2791	The problem of doing event processing in the parent I<and> the child
		2792	is much more complicated: even for backends that I<are> fork-aware or
		2793	fork-safe, their behaviour is not usually what you want: fork clones all
		2794	watchers, that means all timers, I/O watchers etc. are active in both
		2795	parent and child, which is almost never what you want. USing C<exec>
		2796	to start worker children from some kind of manage rprocess is usually
		2797	preferred, because it is much easier and cleaner, at the expense of having
		2798	to have another binary.
1526		2799
1527		2800
1528	=head1 SECURITY CONSIDERATIONS	2801	=head1 SECURITY CONSIDERATIONS
1529		2802
1530	AnyEvent can be forced to load any event model via	2803	AnyEvent can be forced to load any event model via
…		…
1535	specified in the variable.	2808	specified in the variable.
1536		2809
1537	You can make AnyEvent completely ignore this variable by deleting it	2810	You can make AnyEvent completely ignore this variable by deleting it
1538	before the first watcher gets created, e.g. with a C<BEGIN> block:	2811	before the first watcher gets created, e.g. with a C<BEGIN> block:
1539		2812
1540	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	2813	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1541		2814
1542	use AnyEvent;	2815	use AnyEvent;
1543		2816
1544	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can	2817	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1545	be used to probe what backend is used and gain other information (which is	2818	be used to probe what backend is used and gain other information (which is
1546	probably even less useful to an attacker than PERL_ANYEVENT_MODEL).	2819	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2820	$ENV{PERL_ANYEVENT_STRICT}.
		2821
		2822	Note that AnyEvent will remove I<all> environment variables starting with
		2823	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2824	enabled.
		2825
		2826
		2827	=head1 BUGS
		2828
		2829	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2830	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2831	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2832	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2833	pronounced).
1547		2834
1548		2835
1549	=head1 SEE ALSO	2836	=head1 SEE ALSO
1550		2837
1551	Utility functions: L<AnyEvent::Util>.	2838	Tutorial/Introduction: L<AnyEvent::Intro>.
1552		2839
1553	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,	2840	FAQ: L<AnyEvent::FAQ>.
1554	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.	2841
		2842	Utility functions: L<AnyEvent::Util> (misc. grab-bag), L<AnyEvent::Log>
		2843	(simply logging).
		2844
		2845	Development/Debugging: L<AnyEvent::Strict> (stricter checking),
		2846	L<AnyEvent::Debug> (interactive shell, watcher tracing).
		2847
		2848	Supported event modules: L<AnyEvent::Loop>, L<EV>, L<EV::Glib>,
		2849	L<Glib::EV>, L<Event>, L<Glib::Event>, L<Glib>, L<Tk>, L<Event::Lib>,
		2850	L<Qt>, L<POE>, L<FLTK>.
1555		2851
1556	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,	2852	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
1557	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,	2853	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
1558	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,	2854	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
		2855	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>, L<Anyevent::Impl::Irssi>,
1559	L<AnyEvent::Impl::POE>.	2856	L<AnyEvent::Impl::FLTK>.
1560		2857
1561	Non-blocking file handles, sockets, TCP clients and	2858	Non-blocking handles, pipes, stream sockets, TCP clients and
1562	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>.	2859	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
1563		2860
1564	Asynchronous DNS: L<AnyEvent::DNS>.	2861	Asynchronous DNS: L<AnyEvent::DNS>.
1565		2862
1566	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,	2863	Thread support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
1567		2864
1568	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>, L<AnyEvent::DNS>.	2865	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::IRC>,
		2866	L<AnyEvent::HTTP>.
1569		2867
1570		2868
1571	=head1 AUTHOR	2869	=head1 AUTHOR
1572		2870
1573	Marc Lehmann <schmorp@schmorp.de>	2871	Marc Lehmann <schmorp@schmorp.de>
1574	http://home.schmorp.de/	2872	http://home.schmorp.de/
1575		2873
1576	=cut	2874	=cut
1577		2875
1578	1	2876	1
1579		2877

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