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Revision 1.375 by root, Thu Aug 25 05:39:47 2011 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent - provide framework for multiple event loops	3	AnyEvent - the DBI of event loop programming
4		4
5	EV, Event, Coro::EV, Coro::Event, Glib, Tk, Perl, Event::Lib, 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
		38	$w->send; # wake up current and all future recv's
20	$w->wait; # enters "main loop" till $condvar gets ->send	39	$w->recv; # enters "main loop" till $condvar gets ->send
21	$w->send; # wake up current and all future wait's	40	# use a condvar in callback mode:
		41	$w->cb (sub { $_[0]->recv });
		42
		43	=head1 INTRODUCTION/TUTORIAL
		44
		45	This manpage is mainly a reference manual. If you are interested
		46	in a tutorial or some gentle introduction, have a look at the
		47	L<AnyEvent::Intro> manpage.
		48
		49	=head1 SUPPORT
		50
		51	An FAQ document is available as L<AnyEvent::FAQ>.
		52
		53	There also is a mailinglist for discussing all things AnyEvent, and an IRC
		54	channel, too.
		55
		56	See the AnyEvent project page at the B<Schmorpforge Ta-Sa Software
		57	Repository>, at L<http://anyevent.schmorp.de>, for more info.
22		58
23	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)	59	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
24		60
25	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	61	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
26	nowadays. So what is different about AnyEvent?	62	nowadays. So what is different about AnyEvent?
27		63
28	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of	64	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
29	policy> and AnyEvent is I<small and efficient>.	65	policy> and AnyEvent is I<small and efficient>.
30		66
31	First and foremost, I<AnyEvent is not an event model> itself, it only	67	First and foremost, I<AnyEvent is not an event model> itself, it only
32	interfaces to whatever event model the main program happens to use in a	68	interfaces to whatever event model the main program happens to use, in a
33	pragmatic way. For event models and certain classes of immortals alike,	69	pragmatic way. For event models and certain classes of immortals alike,
34	the statement "there can only be one" is a bitter reality: In general,	70	the statement "there can only be one" is a bitter reality: In general,
35	only one event loop can be active at the same time in a process. AnyEvent	71	only one event loop can be active at the same time in a process. AnyEvent
36	helps hiding the differences between those event loops.	72	cannot change this, but it can hide the differences between those event
		73	loops.
37		74
38	The goal of AnyEvent is to offer module authors the ability to do event	75	The goal of AnyEvent is to offer module authors the ability to do event
39	programming (waiting for I/O or timer events) without subscribing to a	76	programming (waiting for I/O or timer events) without subscribing to a
40	religion, a way of living, and most importantly: without forcing your	77	religion, a way of living, and most importantly: without forcing your
41	module users into the same thing by forcing them to use the same event	78	module users into the same thing by forcing them to use the same event
42	model you use.	79	model you use.
43		80
44	For modules like POE or IO::Async (which is a total misnomer as it is	81	For modules like POE or IO::Async (which is a total misnomer as it is
45	actually doing all I/O I<synchronously>...), using them in your module is	82	actually doing all I/O I<synchronously>...), using them in your module is
46	like joining a cult: After you joined, you are dependent on them and you	83	like joining a cult: After you join, you are dependent on them and you
47	cannot use anything else, as it is simply incompatible to everything that	84	cannot use anything else, as they are simply incompatible to everything
48	isn't itself. What's worse, all the potential users of your module are	85	that isn't them. What's worse, all the potential users of your
49	I<also> forced to use the same event loop you use.	86	module are I<also> forced to use the same event loop you use.
50		87
51	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	88	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
52	fine. AnyEvent + Tk works fine etc. etc. but none of these work together	89	fine. AnyEvent + Tk works fine etc. etc. but none of these work together
53	with the rest: POE + IO::Async? no go. Tk + Event? no go. Again: if	90	with the rest: POE + EV? No go. Tk + Event? No go. Again: if your module
54	your module uses one of those, every user of your module has to use it,	91	uses one of those, every user of your module has to use it, too. But if
55	too. But if your module uses AnyEvent, it works transparently with all	92	your module uses AnyEvent, it works transparently with all event models it
56	event models it supports (including stuff like POE and IO::Async, as long	93	supports (including stuff like IO::Async, as long as those use one of the
57	as those use one of the supported event loops. It is trivial to add new	94	supported event loops. It is easy to add new event loops to AnyEvent, too,
58	event loops to AnyEvent, too, so it is future-proof).	95	so it is future-proof).
59		96
60	In addition to being free of having to use I<the one and only true event	97	In addition to being free of having to use I<the one and only true event
61	model>, AnyEvent also is free of bloat and policy: with POE or similar	98	model>, AnyEvent also is free of bloat and policy: with POE or similar
62	modules, you get an enourmous amount of code and strict rules you have to	99	modules, you get an enormous amount of code and strict rules you have to
63	follow. AnyEvent, on the other hand, is lean and up to the point, by only	100	follow. AnyEvent, on the other hand, is lean and to the point, by only
64	offering the functionality that is necessary, in as thin as a wrapper as	101	offering the functionality that is necessary, in as thin as a wrapper as
65	technically possible.	102	technically possible.
66		103
		104	Of course, AnyEvent comes with a big (and fully optional!) toolbox
		105	of useful functionality, such as an asynchronous DNS resolver, 100%
		106	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
		107	such as Windows) and lots of real-world knowledge and workarounds for
		108	platform bugs and differences.
		109
67	Of course, if you want lots of policy (this can arguably be somewhat	110	Now, if you I<do want> lots of policy (this can arguably be somewhat
68	useful) and you want to force your users to use the one and only event	111	useful) and you want to force your users to use the one and only event
69	model, you should I<not> use this module.	112	model, you should I<not> use this module.
70		113
71	=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<Coro::EV>, L<Coro::Event>, 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
113	the callback to call, the filehandle to watch, etc.	155	the callback to call, the file handle to watch, etc.
114		156
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
242	Multiple signal occurances can be clumped together into one callback	395	Multiple signal occurrences can be clumped together into one callback
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 guarenteed 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	AnyEvent::detect; # force event module to be initialised
285
286	my $pid = fork or exit 5;	494	my $pid = fork or exit 5;
287		495
288	my $w = AnyEvent->child (	496	my $w = AnyEvent->child (
289	pid => $pid,	497	pid => $pid,
290	cb => sub {	498	cb => sub {
291	my ($pid, $status) = @_;	499	my ($pid, $status) = @_;
292	warn "pid $pid exited with status $status";	500	warn "pid $pid exited with status $status";
293	$done->send;	501	$done->send;
294	},	502	},
295	);	503	);
296		504
297	# do something else, then wait for process exit	505	# do something else, then wait for process exit
298	$done->wait;	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	});
299		547
300	=head2 CONDITION VARIABLES	548	=head2 CONDITION VARIABLES
		549
		550	$cv = AnyEvent->condvar;
		551
		552	$cv->send (<list>);
		553	my @res = $cv->recv;
301		554
302	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
303	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
304	will actively watch for new events and call your callbacks.	557	will actively watch for new events and call your callbacks.
305		558
306	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
307	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).
308		561
309	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
310	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.
311		566
312	Condition variables can be created by calling the C<< AnyEvent->condvar	567	Condition variables can be created by calling the C<< AnyEvent->condvar
313	>> method, usually without arguments. The only argument pair allowed is	568	>> method, usually without arguments. The only argument pair allowed is
314	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
315	becomes true.	570	becomes true, with the condition variable as the first argument (but not
		571	the results).
316		572
317	After creation, the conditon variable is "false" until it becomes "true"	573	After creation, the condition variable is "false" until it becomes "true"
318	by calling the C<send> method.	574	by calling the C<send> method (or calling the condition variable as if it
		575	were a callback, read about the caveats in the description for the C<<
		576	->send >> method).
319		577
320	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
321	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:
322	in time where multiple outstandign events have been processed. And yet	580
323	another way to call them is transations - each condition variable can be	581	=over 4
324	used to represent a transaction, which finishes at some point and delivers	582
325	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
326		601
327	Condition variables are very useful to signal that something has finished,	602	Condition variables are very useful to signal that something has finished,
328	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,
329	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
330	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
331	called or can synchronously C<< ->wait >> for the results.	606	called or can synchronously C<< ->recv >> for the results.
332		607
333	You can also use them to simulate traditional event loops - for example,	608	You can also use them to simulate traditional event loops - for example,
334	you can block your main program until an event occurs - for example, you	609	you can block your main program until an event occurs - for example, you
335	could C<< ->wait >> in your main program until the user clicks the Quit	610	could C<< ->recv >> in your main program until the user clicks the Quit
336	button of your app, which would C<< ->send >> the "quit" event.	611	button of your app, which would C<< ->send >> the "quit" event.
337		612
338	Note that condition variables recurse into the event loop - if you have	613	Note that condition variables recurse into the event loop - if you have
339	two pieces of code that call C<< ->wait >> in a round-robbin fashion, you	614	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
340	lose. Therefore, condition variables are good to export to your caller, but	615	lose. Therefore, condition variables are good to export to your caller, but
341	you should avoid making a blocking wait yourself, at least in callbacks,	616	you should avoid making a blocking wait yourself, at least in callbacks,
342	as this asks for trouble.	617	as this asks for trouble.
343		618
344	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
345	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
346	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
347	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
348	it's C<new> method in your own C<new> method.	623	its C<new> method in your own C<new> method.
349		624
350	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
351	eventually calls C<< -> send >>, and the "consumer side", which waits	626	eventually calls C<< -> send >>, and the "consumer side", which waits
352	for the send to occur.	627	for the send to occur.
353		628
354	Example:	629	Example: wait for a timer.
355		630
356	# wait till the result is ready	631	# condition: "wait till the timer is fired"
357	my $result_ready = AnyEvent->condvar;	632	my $timer_fired = AnyEvent->condvar;
358		633
359	# do something such as adding a timer	634	# create the timer - we could wait for, say
360	# or socket watcher the calls $result_ready->send	635	# a handle becomign ready, or even an
361	# when the "result" is ready.	636	# AnyEvent::HTTP request to finish, but
362	# in this case, we simply use a timer:	637	# in this case, we simply use a timer:
363	my $w = AnyEvent->timer (	638	my $w = AnyEvent->timer (
364	after => 1,	639	after => 1,
365	cb => sub { $result_ready->send },	640	cb => sub { $timer_fired->send },
366	);	641	);
367		642
368	# this "blocks" (while handling events) till the callback	643	# this "blocks" (while handling events) till the callback
369	# calls send	644	# calls ->send
370	$result_ready->wait;	645	$timer_fired->recv;
		646
		647	Example: wait for a timer, but take advantage of the fact that condition
		648	variables are also callable directly.
		649
		650	my $done = AnyEvent->condvar;
		651	my $delay = AnyEvent->timer (after => 5, cb => $done);
		652	$done->recv;
		653
		654	Example: Imagine an API that returns a condvar and doesn't support
		655	callbacks. This is how you make a synchronous call, for example from
		656	the main program:
		657
		658	use AnyEvent::CouchDB;
		659
		660	...
		661
		662	my @info = $couchdb->info->recv;
		663
		664	And this is how you would just set a callback to be called whenever the
		665	results are available:
		666
		667	$couchdb->info->cb (sub {
		668	my @info = $_[0]->recv;
		669	});
371		670
372	=head3 METHODS FOR PRODUCERS	671	=head3 METHODS FOR PRODUCERS
373		672
374	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
375	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
…		…
378		677
379	=over 4	678	=over 4
380		679
381	=item $cv->send (...)	680	=item $cv->send (...)
382		681
383	Flag the condition as ready - a running C<< ->wait >> and all further	682	Flag the condition as ready - a running C<< ->recv >> and all further
384	calls to C<wait> will (eventually) return after this method has been	683	calls to C<recv> will (eventually) return after this method has been
385	called. If nobody is waiting the send will be remembered.	684	called. If nobody is waiting the send will be remembered.
386		685
387	If a callback has been set on the condition variable, it is called	686	If a callback has been set on the condition variable, it is called
388	immediately from within send.	687	immediately from within send.
389		688
390	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
391	future C<< ->wait >> calls.	690	future C<< ->recv >> calls.
		691
		692	Condition variables are overloaded so one can call them directly (as if
		693	they were a code reference). Calling them directly is the same as calling
		694	C<send>.
392		695
393	=item $cv->croak ($error)	696	=item $cv->croak ($error)
394		697
395	Similar to send, but causes all call's wait C<< ->wait >> to invoke	698	Similar to send, but causes all calls to C<< ->recv >> to invoke
396	C<Carp::croak> with the given error message/object/scalar.	699	C<Carp::croak> with the given error message/object/scalar.
397		700
398	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
399	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.
400		707
401	=item $cv->begin ([group callback])	708	=item $cv->begin ([group callback])
402		709
403	=item $cv->end	710	=item $cv->end
404		711
…		…
406	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
407	to use a condition variable for the whole process.	714	to use a condition variable for the whole process.
408		715
409	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
410	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
411	>>, 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
412	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
413	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.
414		722
415	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:
416		730
417	my $cv = AnyEvent->condvar;	731	my $cv = AnyEvent->condvar;
418		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
419	my %result;	757	my %result;
420	$cv->begin (sub { $cv->send (\%result) });	758	$cv->begin (sub { shift->send (\%result) });
421		759
422	for my $host (@list_of_hosts) {	760	for my $host (@list_of_hosts) {
423	$cv->begin;	761	$cv->begin;
424	ping_host_then_call_callback $host, sub {	762	ping_host_then_call_callback $host, sub {
425	$result{$host} = ...;	763	$result{$host} = ...;
…		…
440	loop, which serves two important purposes: first, it sets the callback	778	loop, which serves two important purposes: first, it sets the callback
441	to be called once the counter reaches C<0>, and second, it ensures that	779	to be called once the counter reaches C<0>, and second, it ensures that
442	C<send> is called even when C<no> hosts are being pinged (the loop	780	C<send> is called even when C<no> hosts are being pinged (the loop
443	doesn't execute once).	781	doesn't execute once).
444		782
445	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
446	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
447	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
448	C<begin> and for eahc subrequest you finish, call C<end>.	786	subrequest you start, call C<begin> and for each subrequest you finish,
		787	call C<end>.
449		788
450	=back	789	=back
451		790
452	=head3 METHODS FOR CONSUMERS	791	=head3 METHODS FOR CONSUMERS
453		792
454	These methods should only be used by the consuming side, i.e. the	793	These methods should only be used by the consuming side, i.e. the
455	code awaits the condition.	794	code awaits the condition.
456		795
457	=over 4	796	=over 4
458		797
459	=item $cv->wait	798	=item $cv->recv
460		799
461	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak	800	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
462	>> methods have been called on c<$cv>, while servicing other watchers	801	>> methods have been called on C<$cv>, while servicing other watchers
463	normally.	802	normally.
464		803
465	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
466	will return immediately.	805	will return immediately.
467		806
…		…
469	function will call C<croak>.	808	function will call C<croak>.
470		809
471	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,
472	in scalar context only the first one will be returned.	811	in scalar context only the first one will be returned.
473		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
474	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
475	(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
476	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
477	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
478	condition variables with some kind of request results and supporting	824	condition variables with some kind of request results and supporting
479	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,
480	while still suppporting blocking waits if the caller so desires).	826	while still supporting blocking waits if the caller so desires).
481		827
482	Another reason I<never> to C<< ->wait >> in a module is that you cannot
483	sensibly have two C<< ->wait >>'s in parallel, as that would require
484	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
485	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and
486	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
487	from different coroutines, however).
488
489	You can ensure that C<< -wait >> never blocks by setting a callback and	828	You can ensure that C<< ->recv >> never blocks by setting a callback and
490	only calling C<< ->wait >> from within that callback (or at a later	829	only calling C<< ->recv >> from within that callback (or at a later
491	time). This will work even when the event loop does not support blocking	830	time). This will work even when the event loop does not support blocking
492	waits otherwise.	831	waits otherwise.
493		832
494	=item $bool = $cv->ready	833	=item $bool = $cv->ready
495		834
496	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
497	C<croak> have been called.	836	C<croak> have been called.
498		837
499	=item $cb = $cv->cb ([new callback])	838	=item $cb = $cv->cb ($cb->($cv))
500		839
501	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
502	replaces it before doing so.	841	replaces it before doing so.
503		842
504	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
505	C<send> or C<croak> are called. Calling C<wait> 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
506	or at any later time is guaranteed not to block.	847	the callback or at any later time is guaranteed not to block.
507		848
508	=back	849	=back
509		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
510	=head1 GLOBAL VARIABLES AND FUNCTIONS	914	=head1 GLOBAL VARIABLES AND FUNCTIONS
511		915
		916	These are not normally required to use AnyEvent, but can be useful to
		917	write AnyEvent extension modules.
		918
512	=over 4	919	=over 4
513		920
514	=item $AnyEvent::MODEL	921	=item $AnyEvent::MODEL
515		922
516	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
517	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
518	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
519	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
520	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
521		930	will be C<urxvt::anyevent>).
522	The known classes so far are:
523
524	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
525	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
526	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
527	AnyEvent::Impl::Event based on Event, second best choice.
528	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
529	AnyEvent::Impl::Glib based on Glib, third-best choice.
530	AnyEvent::Impl::Tk based on Tk, very bad choice.
531	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
532	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
533	AnyEvent::Impl::POE based on POE, not generic enough for full support.
534
535	There is no support for WxWidgets, as WxWidgets has no support for
536	watching file handles. However, you can use WxWidgets through the
537	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
538	second, which was considered to be too horrible to even consider for
539	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
540	it's adaptor.
541
542	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
543	autodetecting them.
544		931
545	=item AnyEvent::detect	932	=item AnyEvent::detect
546		933
547	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	934	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
548	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
549	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
550	runtime.	937	runtime, and not e.g. during initialisation of your module.
		938
		939	The effect of calling this function is as if a watcher had been created
		940	(specifically, actions that happen "when the first watcher is created"
		941	happen when calling detetc as well).
		942
		943	If you need to do some initialisation before AnyEvent watchers are
		944	created, use C<post_detect>.
		945
		946	=item $guard = AnyEvent::post_detect { BLOCK }
		947
		948	Arranges for the code block to be executed as soon as the event model is
		949	autodetected (or immediately if that has already happened).
		950
		951	The block will be executed I<after> the actual backend has been detected
		952	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		953	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		954	other initialisations - see the sources of L<AnyEvent::Strict> or
		955	L<AnyEvent::AIO> to see how this is used.
		956
		957	The most common usage is to create some global watchers, without forcing
		958	event module detection too early, for example, L<AnyEvent::AIO> creates
		959	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		960	avoid autodetecting the event module at load time.
		961
		962	If called in scalar or list context, then it creates and returns an object
		963	that automatically removes the callback again when it is destroyed (or
		964	C<undef> when the hook was immediately executed). See L<AnyEvent::AIO> for
		965	a case where this is useful.
		966
		967	Example: Create a watcher for the IO::AIO module and store it in
		968	C<$WATCHER>, but do so only do so after the event loop is initialised.
		969
		970	our WATCHER;
		971
		972	my $guard = AnyEvent::post_detect {
		973	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		974	};
		975
		976	# the ||= is important in case post_detect immediately runs the block,
		977	# as to not clobber the newly-created watcher. assigning both watcher and
		978	# post_detect guard to the same variable has the advantage of users being
		979	# able to just C<undef $WATCHER> if the watcher causes them grief.
		980
		981	$WATCHER ||= $guard;
		982
		983	=item @AnyEvent::post_detect
		984
		985	If there are any code references in this array (you can C<push> to it
		986	before or after loading AnyEvent), then they will be called directly
		987	after the event loop has been chosen.
		988
		989	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		990	if it is defined then the event loop has already been detected, and the
		991	array will be ignored.
		992
		993	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		994	it, as it takes care of these details.
		995
		996	This variable is mainly useful for modules that can do something useful
		997	when AnyEvent is used and thus want to know when it is initialised, but do
		998	not need to even load it by default. This array provides the means to hook
		999	into AnyEvent passively, without loading it.
		1000
		1001	Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used
		1002	together, you could put this into Coro (this is the actual code used by
		1003	Coro to accomplish this):
		1004
		1005	if (defined $AnyEvent::MODEL) {
		1006	# AnyEvent already initialised, so load Coro::AnyEvent
		1007	require Coro::AnyEvent;
		1008	} else {
		1009	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent
		1010	# as soon as it is
		1011	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };
		1012	}
		1013
		1014	=item AnyEvent::postpone { BLOCK }
		1015
		1016	Arranges for the block to be executed as soon as possible, but not before
		1017	the call itself returns. In practise, the block will be executed just
		1018	before the event loop polls for new events, or shortly afterwards.
		1019
		1020	This function never returns anything (to make the C<return postpone { ...
		1021	}> idiom more useful.
		1022
		1023	To understand the usefulness of this function, consider a function that
		1024	asynchronously does something for you and returns some transaction
		1025	object or guard to let you cancel the operation. For example,
		1026	C<AnyEvent::Socket::tcp_connect>:
		1027
		1028	# start a conenction attempt unless one is active
		1029	$self->{connect_guard} ||= AnyEvent::Socket::tcp_connect "www.example.net", 80, sub {
		1030	delete $self->{connect_guard};
		1031	...
		1032	};
		1033
		1034	Imagine that this function could instantly call the callback, for
		1035	example, because it detects an obvious error such as a negative port
		1036	number. Invoking the callback before the function returns causes problems
		1037	however: the callback will be called and will try to delete the guard
		1038	object. But since the function hasn't returned yet, there is nothing to
		1039	delete. When the function eventually returns it will assign the guard
		1040	object to C<< $self->{connect_guard} >>, where it will likely never be
		1041	deleted, so the program thinks it is still trying to connect.
		1042
		1043	This is where C<AnyEvent::postpone> should be used. Instead of calling the
		1044	callback directly on error:
		1045
		1046	$cb->(undef), return # signal error to callback, BAD!
		1047	if $some_error_condition;
		1048
		1049	It should use C<postpone>:
		1050
		1051	AnyEvent::postpone { $cb->(undef) }, return # signal error to callback, later
		1052	if $some_error_condition;
		1053
		1054	=item AnyEvent::log $level, $msg[, @args]
		1055
		1056	Log the given C<$msg> at the given C<$level>.
		1057
		1058	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.
551		1063
552	=back	1064	=back
553		1065
554	=head1 WHAT TO DO IN A MODULE	1066	=head1 WHAT TO DO IN A MODULE
555		1067
…		…
559	Be careful when you create watchers in the module body - AnyEvent will	1071	Be careful when you create watchers in the module body - AnyEvent will
560	decide which event module to use as soon as the first method is called, so	1072	decide which event module to use as soon as the first method is called, so
561	by calling AnyEvent in your module body you force the user of your module	1073	by calling AnyEvent in your module body you force the user of your module
562	to load the event module first.	1074	to load the event module first.
563		1075
564	Never call C<< ->wait >> on a condition variable unless you I<know> that	1076	Never call C<< ->recv >> on a condition variable unless you I<know> that
565	the C<< ->send >> method has been called on it already. This is	1077	the C<< ->send >> method has been called on it already. This is
566	because it will stall the whole program, and the whole point of using	1078	because it will stall the whole program, and the whole point of using
567	events is to stay interactive.	1079	events is to stay interactive.
568		1080
569	It is fine, however, to call C<< ->wait >> when the user of your module	1081	It is fine, however, to call C<< ->recv >> when the user of your module
570	requests it (i.e. if you create a http request object ad have a method	1082	requests it (i.e. if you create a http request object ad have a method
571	called C<results> that returns the results, it should call C<< ->wait >>	1083	called C<results> that returns the results, it may call C<< ->recv >>
572	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).
573		1085
574	=head1 WHAT TO DO IN THE MAIN PROGRAM	1086	=head1 WHAT TO DO IN THE MAIN PROGRAM
575		1087
576	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
577	dictate which event model to use.	1089	dictate which event model to use.
578		1090
579	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
580	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
581	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.
582		1096
583	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
584	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
585	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
586	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
587	modules might create watchers when they are loaded, and AnyEvent will	1101	modules might create watchers when they are loaded, and AnyEvent will
588	decide on the event model to use as soon as it creates watchers, and it	1102	decide on the event model to use as soon as it creates watchers, and it
589	might chose the wrong one unless you load the correct one yourself.	1103	might choose the wrong one unless you load the correct one yourself.
590		1104
591	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
592	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	1106	C<AnyEvent::Loop> module, which gives you similar behaviour
593	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
594		1125
595	=head1 OTHER MODULES	1126	=head1 OTHER MODULES
596		1127
597	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
598	AnyEvent and can therefore be mixed easily with other AnyEvent modules	1129	AnyEvent as a client and can therefore be mixed easily with other
599	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
600	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 :)
601		1135
602	=over 4	1136	=over 4
603		1137
604	=item L<AnyEvent::Util>	1138	=item L<AnyEvent::Util>
605		1139
606	Contains various utility functions that replace often-used but blocking	1140	Contains various utility functions that replace often-used blocking
607	functions such as C<inet_aton> by event-/callback-based versions.	1141	functions such as C<inet_aton> with event/callback-based versions.
		1142
		1143	=item L<AnyEvent::Socket>
		1144
		1145	Provides various utility functions for (internet protocol) sockets,
		1146	addresses and name resolution. Also functions to create non-blocking tcp
		1147	connections or tcp servers, with IPv6 and SRV record support and more.
608		1148
609	=item L<AnyEvent::Handle>	1149	=item L<AnyEvent::Handle>
610		1150
611	Provide read and write buffers and manages watchers for reads and writes.	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>).
612		1154
613	=item L<AnyEvent::Socket>	1155	=item L<AnyEvent::DNS>
614		1156
615	Provides a means to do non-blocking connects, accepts etc.	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.
616		1193
617	=item L<AnyEvent::HTTPD>	1194	=item L<AnyEvent::HTTPD>
618		1195
619	Provides a simple web application server framework.	1196	A simple embedded webserver.
620
621	=item L<AnyEvent::DNS>
622
623	Provides asynchronous DNS resolver capabilities, beyond what
624	L<AnyEvent::Util> offers.
625		1197
626	=item L<AnyEvent::FastPing>	1198	=item L<AnyEvent::FastPing>
627		1199
628	The fastest ping in the west.	1200	The fastest ping in the west.
629		1201
630	=item L<Net::IRC3>
631
632	AnyEvent based IRC client module family.
633
634	=item L<Net::XMPP2>
635
636	AnyEvent based XMPP (Jabber protocol) module family.
637
638	=item L<Net::FCP>
639
640	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
641	of AnyEvent.
642
643	=item L<Event::ExecFlow>
644
645	High level API for event-based execution flow control.
646
647	=item L<Coro>	1202	=item L<Coro>
648		1203
649	Has special support for AnyEvent.	1204	Has special support for AnyEvent via L<Coro::AnyEvent>.
650
651	=item L<IO::Lambda>
652
653	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
654
655	=item L<IO::AIO>
656
657	Truly asynchronous I/O, should be in the toolbox of every event
658	programmer. Can be trivially made to use AnyEvent.
659
660	=item L<BDB>
661
662	Truly asynchronous Berkeley DB access. Can be trivially made to use
663	AnyEvent.
664		1205
665	=back	1206	=back
666		1207
667	=cut	1208	=cut
668		1209
669	package AnyEvent;	1210	package AnyEvent;
670		1211
671	no warnings;	1212	# basically a tuned-down version of common::sense
672	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	}
673		1219
		1220	BEGIN { AnyEvent::common_sense }
		1221
674	use Carp;	1222	use Carp ();
675		1223
676	our $VERSION = '3.3';	1224	our $VERSION = '6.01';
677	our $MODEL;	1225	our $MODEL;
678		1226
679	our $AUTOLOAD;
680	our @ISA;	1227	our @ISA;
681		1228
682	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
683
684	our @REGISTRY;	1229	our @REGISTRY;
685		1230
		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	$ENV{"PERL_ANYEVENT_$_"} = $ENV{"AE_$_"}
		1242	for grep s/^AE_// && !exists $ENV{"PERL_ANYEVENT_$_"}, keys %ENV;
		1243
		1244	@ENV{grep /^PERL_ANYEVENT_/, keys %ENV} = ()
		1245	if ${^TAINT};
		1246
		1247	$VERBOSE = $ENV{PERL_ANYEVENT_VERBOSE}*1;
		1248	}
		1249
		1250	our $MAX_SIGNAL_LATENCY = 10;
		1251
		1252	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		1253
		1254	{
		1255	my $idx;
		1256	$PROTOCOL{$_} = ++$idx
		1257	for reverse split /\s*,\s*/,
		1258	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		1259	}
		1260
		1261	our @post_detect;
		1262
		1263	sub post_detect(&) {
		1264	my ($cb) = @_;
		1265
		1266	push @post_detect, $cb;
		1267
		1268	defined wantarray
		1269	? bless \$cb, "AnyEvent::Util::postdetect"
		1270	: ()
		1271	}
		1272
		1273	sub AnyEvent::Util::postdetect::DESTROY {
		1274	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		1275	}
		1276
		1277	our $POSTPONE_W;
		1278	our @POSTPONE;
		1279
		1280	sub _postpone_exec {
		1281	undef $POSTPONE_W;
		1282
		1283	&{ shift @POSTPONE }
		1284	while @POSTPONE;
		1285	}
		1286
		1287	sub postpone(&) {
		1288	push @POSTPONE, shift;
		1289
		1290	$POSTPONE_W ||= AE::timer (0, 0, \&_postpone_exec);
		1291
		1292	()
		1293	}
		1294
		1295	sub log($$;@) {
		1296	# only load the bug bloated module when we actually are about to log something
		1297	if ($_[0] <= $VERBOSE) {
		1298	require AnyEvent::Log;
		1299	# AnyEvent::Log overwrites this function
		1300	goto &log;
		1301	}
		1302	}
		1303
		1304	if (length $ENV{PERL_ANYEVENT_LOG}) {
		1305	require AnyEvent::Log; # AnyEvent::Log does the thing for us
		1306	}
		1307
686	my @models = (	1308	our @models = (
687	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
688	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
689	[EV:: => AnyEvent::Impl::EV::],	1309	[EV:: => AnyEvent::Impl::EV:: , 1],
		1310	[AnyEvent::Loop:: => AnyEvent::Impl::Perl:: , 1],
		1311	# everything below here will not (normally) be autoprobed
		1312	# as the pure perl backend should work everywhere
		1313	# and is usually faster
690	[Event:: => AnyEvent::Impl::Event::],	1314	[Event:: => AnyEvent::Impl::Event::, 1],
		1315	[Glib:: => AnyEvent::Impl::Glib:: , 1], # becomes extremely slow with many watchers
		1316	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		1317	[Irssi:: => AnyEvent::Impl::Irssi::], # Irssi has a bogus "Event" package
691	[Tk:: => AnyEvent::Impl::Tk::],	1318	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		1319	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		1320	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
692	[Wx:: => AnyEvent::Impl::POE::],	1321	[Wx:: => AnyEvent::Impl::POE::],
693	[Prima:: => AnyEvent::Impl::POE::],	1322	[Prima:: => AnyEvent::Impl::POE::],
694	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1323	[IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # a bitch to autodetect
695	# everything below here will not be autoprobed as the pureperl backend should work everywhere	1324	[Cocoa::EventLoop:: => AnyEvent::Impl::Cocoa::],
696	[Glib:: => AnyEvent::Impl::Glib::],	1325	[FLTK:: => AnyEvent::Impl::FLTK2::],
697	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
698	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
699	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
700	);	1326	);
701		1327
702	our %method = map +($_ => 1), qw(io timer signal child condvar one_event DESTROY);	1328	our @isa_hook;
		1329
		1330	sub _isa_set {
		1331	my @pkg = ("AnyEvent", (map $_->[0], grep defined, @isa_hook), $MODEL);
		1332
		1333	@{"$pkg[$_-1]::ISA"} = $pkg[$_]
		1334	for 1 .. $#pkg;
		1335
		1336	grep $_ && $_->[1], @isa_hook
		1337	and AE::_reset ();
		1338	}
		1339
		1340	# used for hooking AnyEvent::Strict and AnyEvent::Debug::Wrap into the class hierarchy
		1341	sub _isa_hook($$;$) {
		1342	my ($i, $pkg, $reset_ae) = @_;
		1343
		1344	$isa_hook[$i] = $pkg ? [$pkg, $reset_ae] : undef;
		1345
		1346	_isa_set;
		1347	}
		1348
		1349	# all autoloaded methods reserve the complete glob, not just the method slot.
		1350	# due to bugs in perls method cache implementation.
		1351	our @methods = qw(io timer time now now_update signal child idle condvar);
703		1352
704	sub detect() {	1353	sub detect() {
		1354	return $MODEL if $MODEL; # some programs keep references to detect
		1355
		1356	local $!; # for good measure
		1357	local $SIG{__DIE__}; # we use eval
		1358
		1359	# free some memory
		1360	*detect = sub () { $MODEL };
		1361	# undef &func doesn't correctly update the method cache. grmbl.
		1362	# so we delete the whole glob. grmbl.
		1363	# otoh, perl doesn't let me undef an active usb, but it lets me free
		1364	# a glob with an active sub. hrm. i hope it works, but perl is
		1365	# usually buggy in this department. sigh.
		1366	delete @{"AnyEvent::"}{@methods};
		1367	undef @methods;
		1368
		1369	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z0-9:]+)$/) {
		1370	my $model = $1;
		1371	$model = "AnyEvent::Impl::$model" unless $model =~ s/::$//;
		1372	if (eval "require $model") {
		1373	AnyEvent::log 7 => "loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.";
		1374	$MODEL = $model;
		1375	} else {
		1376	AnyEvent::log warn => "unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@";
		1377	}
		1378	}
		1379
		1380	# check for already loaded models
705	unless ($MODEL) {	1381	unless ($MODEL) {
706	no strict 'refs';	1382	for (@REGISTRY, @models) {
707		1383	my ($package, $model) = @$_;
708	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	1384	if (${"$package\::VERSION"} > 0) {
709	my $model = "AnyEvent::Impl::$1";
710	if (eval "require $model") {	1385	if (eval "require $model") {
		1386	AnyEvent::log 7 => "autodetected model '$model', using it.";
711	$MODEL = $model;	1387	$MODEL = $model;
712	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	1388	last;
713	} else {	1389	}
714	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;
715	}	1390	}
716	}	1391	}
717		1392
718	# check for already loaded models
719	unless ($MODEL) {	1393	unless ($MODEL) {
		1394	# try to autoload a model
720	for (@REGISTRY, @models) {	1395	for (@REGISTRY, @models) {
721	my ($package, $model) = @$_;	1396	my ($package, $model, $autoload) = @$_;
		1397	if (
		1398	$autoload
		1399	and eval "require $package"
722	if (${"$package\::VERSION"} > 0) {	1400	and ${"$package\::VERSION"} > 0
723	if (eval "require $model") {	1401	and eval "require $model"
		1402	) {
		1403	AnyEvent::log 7 => "autoloaded model '$model', using it.";
724	$MODEL = $model;	1404	$MODEL = $model;
725	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;
726	last;	1405	last;
727	}
728	}	1406	}
729	}	1407	}
730		1408
731	unless ($MODEL) {	1409	$MODEL
732	# try to load a model	1410	or die "AnyEvent: backend autodetection failed - did you properly install AnyEvent?";
		1411	}
		1412	}
733		1413
734	for (@REGISTRY, @models) {	1414	# free memory only needed for probing
735	my ($package, $model) = @$_;	1415	undef @models;
736	if (eval "require $package"	1416	undef @REGISTRY;
737	and ${"$package\::VERSION"} > 0	1417
738	and eval "require $model") {	1418	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
739	$MODEL = $model;	1419
740	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;	1420	# now nuke some methods that are overridden by the backend.
		1421	# SUPER usage is not allowed in these.
		1422	for (qw(time signal child idle)) {
		1423	undef &{"AnyEvent::Base::$_"}
		1424	if defined &{"$MODEL\::$_"};
		1425	}
		1426
		1427	_isa_set;
		1428
		1429	# we're officially open!
		1430
		1431	if ($ENV{PERL_ANYEVENT_STRICT}) {
		1432	require AnyEvent::Strict;
		1433	}
		1434
		1435	if ($ENV{PERL_ANYEVENT_DEBUG_WRAP}) {
		1436	require AnyEvent::Debug;
		1437	AnyEvent::Debug::wrap ($ENV{PERL_ANYEVENT_DEBUG_WRAP});
		1438	}
		1439
		1440	if (length $ENV{PERL_ANYEVENT_DEBUG_SHELL}) {
		1441	require AnyEvent::Socket;
		1442	require AnyEvent::Debug;
		1443
		1444	my $shell = $ENV{PERL_ANYEVENT_DEBUG_SHELL};
		1445	$shell =~ s/\$\$/$$/g;
		1446
		1447	my ($host, $service) = AnyEvent::Socket::parse_hostport ($shell);
		1448	$AnyEvent::Debug::SHELL = AnyEvent::Debug::shell ($host, $service);
		1449	}
		1450
		1451	# now the anyevent environment is set up as the user told us to, so
		1452	# call the actual user code - post detects
		1453
		1454	(shift @post_detect)->() while @post_detect;
		1455	undef @post_detect;
		1456
		1457	*post_detect = sub(&) {
		1458	shift->();
		1459
		1460	undef
		1461	};
		1462
		1463	$MODEL
		1464	}
		1465
		1466	for my $name (@methods) {
		1467	*$name = sub {
		1468	detect;
		1469	# we use goto because
		1470	# a) it makes the thunk more transparent
		1471	# b) it allows us to delete the thunk later
		1472	goto &{ UNIVERSAL::can AnyEvent => "SUPER::$name" }
		1473	};
		1474	}
		1475
		1476	# utility function to dup a filehandle. this is used by many backends
		1477	# to support binding more than one watcher per filehandle (they usually
		1478	# allow only one watcher per fd, so we dup it to get a different one).
		1479	sub _dupfh($$;$$) {
		1480	my ($poll, $fh, $r, $w) = @_;
		1481
		1482	# cygwin requires the fh mode to be matching, unix doesn't
		1483	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1484
		1485	open my $fh2, $mode, $fh
		1486	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1487
		1488	# we assume CLOEXEC is already set by perl in all important cases
		1489
		1490	($fh2, $rw)
		1491	}
		1492
		1493	=head1 SIMPLIFIED AE API
		1494
		1495	Starting with version 5.0, AnyEvent officially supports a second, much
		1496	simpler, API that is designed to reduce the calling, typing and memory
		1497	overhead by using function call syntax and a fixed number of parameters.
		1498
		1499	See the L<AE> manpage for details.
		1500
		1501	=cut
		1502
		1503	package AE;
		1504
		1505	our $VERSION = $AnyEvent::VERSION;
		1506
		1507	sub _reset() {
		1508	eval q{
		1509	# fall back to the main API by default - backends and AnyEvent::Base
		1510	# implementations can overwrite these.
		1511
		1512	sub io($$$) {
		1513	AnyEvent->io (fh => $_[0], poll => $_[1] ? "w" : "r", cb => $_[2])
		1514	}
		1515
		1516	sub timer($$$) {
		1517	AnyEvent->timer (after => $_[0], interval => $_[1], cb => $_[2])
		1518	}
		1519
		1520	sub signal($$) {
		1521	AnyEvent->signal (signal => $_[0], cb => $_[1])
		1522	}
		1523
		1524	sub child($$) {
		1525	AnyEvent->child (pid => $_[0], cb => $_[1])
		1526	}
		1527
		1528	sub idle($) {
		1529	AnyEvent->idle (cb => $_[0]);
		1530	}
		1531
		1532	sub cv(;&) {
		1533	AnyEvent->condvar (@_ ? (cb => $_[0]) : ())
		1534	}
		1535
		1536	sub now() {
		1537	AnyEvent->now
		1538	}
		1539
		1540	sub now_update() {
		1541	AnyEvent->now_update
		1542	}
		1543
		1544	sub time() {
		1545	AnyEvent->time
		1546	}
		1547
		1548	*postpone = \&AnyEvent::postpone;
		1549	*log = \&AnyEvent::log;
		1550	};
		1551	die if $@;
		1552	}
		1553
		1554	BEGIN { _reset }
		1555
		1556	package AnyEvent::Base;
		1557
		1558	# default implementations for many methods
		1559
		1560	sub time {
		1561	eval q{ # poor man's autoloading {}
		1562	# probe for availability of Time::HiRes
		1563	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1564	AnyEvent::log 8 => "AnyEvent: using Time::HiRes for sub-second timing accuracy."
		1565	if $AnyEvent::VERBOSE >= 8;
		1566	*time = sub { Time::HiRes::time () };
		1567	*AE::time = \& Time::HiRes::time ;
		1568	# if (eval "use POSIX (); (POSIX::times())...
		1569	} else {
		1570	AnyEvent::log critical => "using built-in time(), WARNING, no sub-second resolution!";
		1571	*time = sub { CORE::time };
		1572	*AE::time = sub (){ CORE::time };
		1573	}
		1574
		1575	*now = \&time;
		1576	};
		1577	die if $@;
		1578
		1579	&time
		1580	}
		1581
		1582	*now = \&time;
		1583	sub now_update { }
		1584
		1585	sub _poll {
		1586	Carp::croak "$AnyEvent::MODEL does not support blocking waits. Caught";
		1587	}
		1588
		1589	# default implementation for ->condvar
		1590	# in fact, the default should not be overwritten
		1591
		1592	sub condvar {
		1593	eval q{ # poor man's autoloading {}
		1594	*condvar = sub {
		1595	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
		1596	};
		1597
		1598	*AE::cv = sub (;&) {
		1599	bless { @_ ? (_ae_cb => shift) : () }, "AnyEvent::CondVar"
		1600	};
		1601	};
		1602	die if $@;
		1603
		1604	&condvar
		1605	}
		1606
		1607	# default implementation for ->signal
		1608
		1609	our $HAVE_ASYNC_INTERRUPT;
		1610
		1611	sub _have_async_interrupt() {
		1612	$HAVE_ASYNC_INTERRUPT = 1*(!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT}
		1613	&& eval "use Async::Interrupt 1.02 (); 1")
		1614	unless defined $HAVE_ASYNC_INTERRUPT;
		1615
		1616	$HAVE_ASYNC_INTERRUPT
		1617	}
		1618
		1619	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1620	our (%SIG_ASY, %SIG_ASY_W);
		1621	our ($SIG_COUNT, $SIG_TW);
		1622
		1623	# install a dummy wakeup watcher to reduce signal catching latency
		1624	# used by Impls
		1625	sub _sig_add() {
		1626	unless ($SIG_COUNT++) {
		1627	# try to align timer on a full-second boundary, if possible
		1628	my $NOW = AE::now;
		1629
		1630	$SIG_TW = AE::timer
		1631	$MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1632	$MAX_SIGNAL_LATENCY,
		1633	sub { } # just for the PERL_ASYNC_CHECK
		1634	;
		1635	}
		1636	}
		1637
		1638	sub _sig_del {
		1639	undef $SIG_TW
		1640	unless --$SIG_COUNT;
		1641	}
		1642
		1643	our $_sig_name_init; $_sig_name_init = sub {
		1644	eval q{ # poor man's autoloading {}
		1645	undef $_sig_name_init;
		1646
		1647	if (_have_async_interrupt) {
		1648	*sig2num = \&Async::Interrupt::sig2num;
		1649	*sig2name = \&Async::Interrupt::sig2name;
		1650	} else {
		1651	require Config;
		1652
		1653	my %signame2num;
		1654	@signame2num{ split ' ', $Config::Config{sig_name} }
		1655	= split ' ', $Config::Config{sig_num};
		1656
		1657	my @signum2name;
		1658	@signum2name[values %signame2num] = keys %signame2num;
		1659
		1660	*sig2num = sub($) {
		1661	$_[0] > 0 ? shift : $signame2num{+shift}
		1662	};
		1663	*sig2name = sub ($) {
		1664	$_[0] > 0 ? $signum2name[+shift] : shift
		1665	};
		1666	}
		1667	};
		1668	die if $@;
		1669	};
		1670
		1671	sub sig2num ($) { &$_sig_name_init; &sig2num }
		1672	sub sig2name($) { &$_sig_name_init; &sig2name }
		1673
		1674	sub signal {
		1675	eval q{ # poor man's autoloading {}
		1676	# probe for availability of Async::Interrupt
		1677	if (_have_async_interrupt) {
		1678	AnyEvent::log 8 => "using Async::Interrupt for race-free signal handling."
		1679	if $AnyEvent::VERBOSE >= 8;
		1680
		1681	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1682	$SIG_IO = AE::io $SIGPIPE_R->fileno, 0, \&_signal_exec;
		1683
		1684	} else {
		1685	AnyEvent::log 8 => "using emulated perl signal handling with latency timer."
		1686	if $AnyEvent::VERBOSE >= 8;
		1687
		1688	if (AnyEvent::WIN32) {
		1689	require AnyEvent::Util;
		1690
		1691	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1692	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R, 1) if $SIGPIPE_R;
		1693	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W, 1) if $SIGPIPE_W; # just in case
		1694	} else {
		1695	pipe $SIGPIPE_R, $SIGPIPE_W;
		1696	fcntl $SIGPIPE_R, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_R;
		1697	fcntl $SIGPIPE_W, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_W; # just in case
		1698
		1699	# not strictly required, as $^F is normally 2, but let's make sure...
		1700	fcntl $SIGPIPE_R, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1701	fcntl $SIGPIPE_W, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1702	}
		1703
		1704	$SIGPIPE_R
		1705	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1706
		1707	$SIG_IO = AE::io $SIGPIPE_R, 0, \&_signal_exec;
		1708	}
		1709
		1710	*signal = $HAVE_ASYNC_INTERRUPT
		1711	? sub {
		1712	my (undef, %arg) = @_;
		1713
		1714	# async::interrupt
		1715	my $signal = sig2num $arg{signal};
		1716	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1717
		1718	$SIG_ASY{$signal} ||= new Async::Interrupt
		1719	cb => sub { undef $SIG_EV{$signal} },
		1720	signal => $signal,
		1721	pipe => [$SIGPIPE_R->filenos],
		1722	pipe_autodrain => 0,
		1723	;
		1724
		1725	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1726	}
		1727	: sub {
		1728	my (undef, %arg) = @_;
		1729
		1730	# pure perl
		1731	my $signal = sig2name $arg{signal};
		1732	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1733
		1734	$SIG{$signal} ||= sub {
741	last;	1735	local $!;
		1736	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1737	undef $SIG_EV{$signal};
742	}	1738	};
		1739
		1740	# can't do signal processing without introducing races in pure perl,
		1741	# so limit the signal latency.
		1742	_sig_add;
		1743
		1744	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1745	}
		1746	;
		1747
		1748	*AnyEvent::Base::signal::DESTROY = sub {
		1749	my ($signal, $cb) = @{$_[0]};
		1750
		1751	_sig_del;
		1752
		1753	delete $SIG_CB{$signal}{$cb};
		1754
		1755	$HAVE_ASYNC_INTERRUPT
		1756	? delete $SIG_ASY{$signal}
		1757	: # delete doesn't work with older perls - they then
		1758	# print weird messages, or just unconditionally exit
		1759	# instead of getting the default action.
		1760	undef $SIG{$signal}
		1761	unless keys %{ $SIG_CB{$signal} };
		1762	};
		1763
		1764	*_signal_exec = sub {
		1765	$HAVE_ASYNC_INTERRUPT
		1766	? $SIGPIPE_R->drain
		1767	: sysread $SIGPIPE_R, (my $dummy), 9;
		1768
		1769	while (%SIG_EV) {
		1770	for (keys %SIG_EV) {
		1771	delete $SIG_EV{$_};
		1772	&$_ for values %{ $SIG_CB{$_} || {} };
743	}	1773	}
744
745	$MODEL
746	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV (or Coro+EV), Event (or Coro+Event) or Glib.";
747	}	1774	}
748	}	1775	};
749
750	unshift @ISA, $MODEL;
751	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
752	}
753
754	$MODEL
755	}
756
757	sub AUTOLOAD {
758	(my $func = $AUTOLOAD) =~ s/.*://;
759
760	$method{$func}
761	or croak "$func: not a valid method for AnyEvent objects";
762
763	detect unless $MODEL;
764
765	my $class = shift;
766	$class->$func (@_);
767	}
768
769	package AnyEvent::Base;
770
771	# default implementation for ->condvar, ->wait, ->broadcast
772
773	sub condvar {
774	bless \my $flag, "AnyEvent::Base::CondVar"
775	}
776
777	sub AnyEvent::Base::CondVar::broadcast {
778	${$_[0]}++;
779	}
780
781	sub AnyEvent::Base::CondVar::wait {
782	AnyEvent->one_event while !${$_[0]};
783	}
784
785	# default implementation for ->signal
786
787	our %SIG_CB;
788
789	sub signal {
790	my (undef, %arg) = @_;
791
792	my $signal = uc $arg{signal}
793	or Carp::croak "required option 'signal' is missing";
794
795	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
796	$SIG{$signal} ||= sub {
797	$_->() for values %{ $SIG_CB{$signal} || {} };
798	};	1776	};
		1777	die if $@;
799		1778
800	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1779	&signal
801	}
802
803	sub AnyEvent::Base::Signal::DESTROY {
804	my ($signal, $cb) = @{$_[0]};
805
806	delete $SIG_CB{$signal}{$cb};
807
808	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };
809	}	1780	}
810		1781
811	# default implementation for ->child	1782	# default implementation for ->child
812		1783
813	our %PID_CB;	1784	our %PID_CB;
814	our $CHLD_W;	1785	our $CHLD_W;
815	our $CHLD_DELAY_W;	1786	our $CHLD_DELAY_W;
816	our $PID_IDLE;
817	our $WNOHANG;
818		1787
819	sub _child_wait {	1788	# used by many Impl's
820	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1789	sub _emit_childstatus($$) {
		1790	my (undef, $rpid, $rstatus) = @_;
		1791
		1792	$_->($rpid, $rstatus)
821	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1793	for values %{ $PID_CB{$rpid} || {} },
822	(values %{ $PID_CB{0} || {} });	1794	values %{ $PID_CB{0} || {} };
		1795	}
		1796
		1797	sub child {
		1798	eval q{ # poor man's autoloading {}
		1799	*_sigchld = sub {
		1800	my $pid;
		1801
		1802	AnyEvent->_emit_childstatus ($pid, $?)
		1803	while ($pid = waitpid -1, WNOHANG) > 0;
		1804	};
		1805
		1806	*child = sub {
		1807	my (undef, %arg) = @_;
		1808
		1809	my $pid = $arg{pid};
		1810	my $cb = $arg{cb};
		1811
		1812	$PID_CB{$pid}{$cb+0} = $cb;
		1813
		1814	unless ($CHLD_W) {
		1815	$CHLD_W = AE::signal CHLD => \&_sigchld;
		1816	# child could be a zombie already, so make at least one round
		1817	&_sigchld;
		1818	}
		1819
		1820	bless [$pid, $cb+0], "AnyEvent::Base::child"
		1821	};
		1822
		1823	*AnyEvent::Base::child::DESTROY = sub {
		1824	my ($pid, $icb) = @{$_[0]};
		1825
		1826	delete $PID_CB{$pid}{$icb};
		1827	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
		1828
		1829	undef $CHLD_W unless keys %PID_CB;
		1830	};
		1831	};
		1832	die if $@;
		1833
		1834	&child
		1835	}
		1836
		1837	# idle emulation is done by simply using a timer, regardless
		1838	# of whether the process is idle or not, and not letting
		1839	# the callback use more than 50% of the time.
		1840	sub idle {
		1841	eval q{ # poor man's autoloading {}
		1842	*idle = sub {
		1843	my (undef, %arg) = @_;
		1844
		1845	my ($cb, $w, $rcb) = $arg{cb};
		1846
		1847	$rcb = sub {
		1848	if ($cb) {
		1849	$w = AE::time;
		1850	&$cb;
		1851	$w = AE::time - $w;
		1852
		1853	# never use more then 50% of the time for the idle watcher,
		1854	# within some limits
		1855	$w = 0.0001 if $w < 0.0001;
		1856	$w = 5 if $w > 5;
		1857
		1858	$w = AE::timer $w, 0, $rcb;
		1859	} else {
		1860	# clean up...
		1861	undef $w;
		1862	undef $rcb;
		1863	}
		1864	};
		1865
		1866	$w = AE::timer 0.05, 0, $rcb;
		1867
		1868	bless \\$cb, "AnyEvent::Base::idle"
		1869	};
		1870
		1871	*AnyEvent::Base::idle::DESTROY = sub {
		1872	undef $${$_[0]};
		1873	};
		1874	};
		1875	die if $@;
		1876
		1877	&idle
		1878	}
		1879
		1880	package AnyEvent::CondVar;
		1881
		1882	our @ISA = AnyEvent::CondVar::Base::;
		1883
		1884	# only to be used for subclassing
		1885	sub new {
		1886	my $class = shift;
		1887	bless AnyEvent->condvar (@_), $class
		1888	}
		1889
		1890	package AnyEvent::CondVar::Base;
		1891
		1892	#use overload
		1893	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1894	# fallback => 1;
		1895
		1896	# save 300+ kilobytes by dirtily hardcoding overloading
		1897	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1898	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1899	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1900	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1901
		1902	our $WAITING;
		1903
		1904	sub _send {
		1905	# nop
		1906	}
		1907
		1908	sub _wait {
		1909	AnyEvent->_poll until $_[0]{_ae_sent};
		1910	}
		1911
		1912	sub send {
		1913	my $cv = shift;
		1914	$cv->{_ae_sent} = [@_];
		1915	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1916	$cv->_send;
		1917	}
		1918
		1919	sub croak {
		1920	$_[0]{_ae_croak} = $_[1];
		1921	$_[0]->send;
		1922	}
		1923
		1924	sub ready {
		1925	$_[0]{_ae_sent}
		1926	}
		1927
		1928	sub recv {
		1929	unless ($_[0]{_ae_sent}) {
		1930	$WAITING
		1931	and Carp::croak "AnyEvent::CondVar: recursive blocking wait attempted";
		1932
		1933	local $WAITING = 1;
		1934	$_[0]->_wait;
823	}	1935	}
824		1936
825	undef $PID_IDLE;	1937	$_[0]{_ae_croak}
826	}	1938	and Carp::croak $_[0]{_ae_croak};
827		1939
828	sub _sigchld {	1940	wantarray
829	# make sure we deliver these changes "synchronous" with the event loop.	1941	? @{ $_[0]{_ae_sent} }
830	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {	1942	: $_[0]{_ae_sent}[0]
831	undef $CHLD_DELAY_W;
832	&_child_wait;
833	});
834	}	1943	}
835		1944
836	sub child {	1945	sub cb {
837	my (undef, %arg) = @_;	1946	my $cv = shift;
838		1947
839	defined (my $pid = $arg{pid} + 0)	1948	@_
840	or Carp::croak "required option 'pid' is missing";	1949	and $cv->{_ae_cb} = shift
		1950	and $cv->{_ae_sent}
		1951	and (delete $cv->{_ae_cb})->($cv);
841		1952
842	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1953	$cv->{_ae_cb}
843
844	unless ($WNOHANG) {
845	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;
846	}
847
848	unless ($CHLD_W) {
849	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
850	# child could be a zombie already, so make at least one round
851	&_sigchld;
852	}
853
854	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"
855	}	1954	}
856		1955
857	sub AnyEvent::Base::Child::DESTROY {	1956	sub begin {
858	my ($pid, $cb) = @{$_[0]};	1957	++$_[0]{_ae_counter};
859		1958	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
860	delete $PID_CB{$pid}{$cb};
861	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
862
863	undef $CHLD_W unless keys %PID_CB;
864	}	1959	}
		1960
		1961	sub end {
		1962	return if --$_[0]{_ae_counter};
		1963	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		1964	}
		1965
		1966	# undocumented/compatibility with pre-3.4
		1967	*broadcast = \&send;
		1968	*wait = \&recv;
		1969
		1970	=head1 ERROR AND EXCEPTION HANDLING
		1971
		1972	In general, AnyEvent does not do any error handling - it relies on the
		1973	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1974	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1975	checking of all AnyEvent methods, however, which is highly useful during
		1976	development.
		1977
		1978	As for exception handling (i.e. runtime errors and exceptions thrown while
		1979	executing a callback), this is not only highly event-loop specific, but
		1980	also not in any way wrapped by this module, as this is the job of the main
		1981	program.
		1982
		1983	The pure perl event loop simply re-throws the exception (usually
		1984	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1985	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1986	so on.
		1987
		1988	=head1 ENVIRONMENT VARIABLES
		1989
		1990	AnyEvent supports a number of environment variables that tune the
		1991	runtime behaviour. They are usually evaluated when AnyEvent is
		1992	loaded, initialised, or a submodule that uses them is loaded. Many of
		1993	them also cause AnyEvent to load additional modules - for example,
		1994	C<PERL_ANYEVENT_DEBUG_WRAP> causes the L<AnyEvent::Debug> module to be
		1995	loaded.
		1996
		1997	All the environment variables documented here start with
		1998	C<PERL_ANYEVENT_>, which is what AnyEvent considers its own
		1999	namespace. Other modules are encouraged (but by no means required) to use
		2000	C<PERL_ANYEVENT_SUBMODULE> if they have registered the AnyEvent::Submodule
		2001	namespace on CPAN, for any submodule. For example, L<AnyEvent::HTTP> could
		2002	be expected to use C<PERL_ANYEVENT_HTTP_PROXY> (it should not access env
		2003	variables starting with C<AE_>, see below).
		2004
		2005	All variables can also be set via the C<AE_> prefix, that is, instead
		2006	of setting C<PERL_ANYEVENT_VERBOSE> you can also set C<AE_VERBOSE>. In
		2007	case there is a clash btween anyevent and another program that uses
		2008	C<AE_something> you can set the corresponding C<PERL_ANYEVENT_something>
		2009	variable to the empty string, as those variables take precedence.
		2010
		2011	When AnyEvent is first loaded, it copies all C<AE_xxx> env variables
		2012	to their C<PERL_ANYEVENT_xxx> counterpart unless that variable already
		2013	exists. If taint mode is on, then AnyEvent will remove I<all> environment
		2014	variables starting with C<PERL_ANYEVENT_> from C<%ENV> (or replace them
		2015	with C<undef> or the empty string, if the corresaponding C<AE_> variable
		2016	is set).
		2017
		2018	The exact algorithm is currently:
		2019
		2020	1. if taint mode enabled, delete all PERL_ANYEVENT_xyz variables from %ENV
		2021	2. copy over AE_xyz to PERL_ANYEVENT_xyz unless the latter alraedy exists
		2022	3. if taint mode enabled, set all PERL_ANYEVENT_xyz variables to undef.
		2023
		2024	This ensures that child processes will not see the C<AE_> variables.
		2025
		2026	The following environment variables are currently known to AnyEvent:
		2027
		2028	=over 4
		2029
		2030	=item C<PERL_ANYEVENT_VERBOSE>
		2031
		2032	By default, AnyEvent will be completely silent except in fatal
		2033	conditions. You can set this environment variable to make AnyEvent more
		2034	talkative. If you want to do more than just set the global logging level
		2035	you should have a look at C<PERL_ANYEVENT_LOG>, which allows much more
		2036	complex specifications.
		2037
		2038	When set to C<5> or higher, causes AnyEvent to warn about unexpected
		2039	conditions, such as not being able to load the event model specified by
		2040	C<PERL_ANYEVENT_MODEL>.
		2041
		2042	When set to C<7> or higher, cause AnyEvent to report to STDERR which event
		2043	model it chooses.
		2044
		2045	When set to C<8> or higher, then AnyEvent will report extra information on
		2046	which optional modules it loads and how it implements certain features.
		2047
		2048	=item C<PERL_ANYEVENT_LOG>
		2049
		2050	Accepts rather complex logging specifications. For example, you could log
		2051	all C<debug> messages of some module to stderr, warnings and above to
		2052	stderr, and errors and above to syslog, with:
		2053
		2054	PERL_ANYEVENT_LOG=Some::Module=debug,+log:filter=warn,+%syslog:%syslog=error,syslog
		2055
		2056	For the rather extensive details, see L<AnyEvent::Log>.
		2057
		2058	This variable is evaluated when AnyEvent (or L<AnyEvent::Log>) is loaded,
		2059	so will take effect even before AnyEvent has initialised itself.
		2060
		2061	Note that specifying this environment variable causes the L<AnyEvent::Log>
		2062	module to be loaded, while C<PERL_ANYEVENT_VERBOSE> does not, so only
		2063	using the latter saves a few hundred kB of memory until the first message
		2064	is being logged.
		2065
		2066	=item C<PERL_ANYEVENT_STRICT>
		2067
		2068	AnyEvent does not do much argument checking by default, as thorough
		2069	argument checking is very costly. Setting this variable to a true value
		2070	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		2071	check the arguments passed to most method calls. If it finds any problems,
		2072	it will croak.
		2073
		2074	In other words, enables "strict" mode.
		2075
		2076	Unlike C<use strict> (or its modern cousin, C<< use L<common::sense>
		2077	>>, it is definitely recommended to keep it off in production. Keeping
		2078	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		2079	can be very useful, however.
		2080
		2081	=item C<PERL_ANYEVENT_DEBUG_SHELL>
		2082
		2083	If this env variable is set, then its contents will be interpreted by
		2084	C<AnyEvent::Socket::parse_hostport> (after replacing every occurance of
		2085	C<$$> by the process pid) and an C<AnyEvent::Debug::shell> is bound on
		2086	that port. The shell object is saved in C<$AnyEvent::Debug::SHELL>.
		2087
		2088	This happens when the first watcher is created.
		2089
		2090	For example, to bind a debug shell on a unix domain socket in
		2091	F<< /tmp/debug<pid>.sock >>, you could use this:
		2092
		2093	PERL_ANYEVENT_DEBUG_SHELL=/tmp/debug\$\$.sock perlprog
		2094
		2095	Note that creating sockets in F</tmp> is very unsafe on multiuser
		2096	systems.
		2097
		2098	=item C<PERL_ANYEVENT_DEBUG_WRAP>
		2099
		2100	Can be set to C<0>, C<1> or C<2> and enables wrapping of all watchers for
		2101	debugging purposes. See C<AnyEvent::Debug::wrap> for details.
		2102
		2103	=item C<PERL_ANYEVENT_MODEL>
		2104
		2105	This can be used to specify the event model to be used by AnyEvent, before
		2106	auto detection and -probing kicks in.
		2107
		2108	It normally is a string consisting entirely of ASCII letters (e.g. C<EV>
		2109	or C<IOAsync>). The string C<AnyEvent::Impl::> gets prepended and the
		2110	resulting module name is loaded and - if the load was successful - used as
		2111	event model backend. If it fails to load then AnyEvent will proceed with
		2112	auto detection and -probing.
		2113
		2114	If the string ends with C<::> instead (e.g. C<AnyEvent::Impl::EV::>) then
		2115	nothing gets prepended and the module name is used as-is (hint: C<::> at
		2116	the end of a string designates a module name and quotes it appropriately).
		2117
		2118	For example, to force the pure perl model (L<AnyEvent::Loop::Perl>) you
		2119	could start your program like this:
		2120
		2121	PERL_ANYEVENT_MODEL=Perl perl ...
		2122
		2123	=item C<PERL_ANYEVENT_PROTOCOLS>
		2124
		2125	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		2126	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		2127	of auto probing).
		2128
		2129	Must be set to a comma-separated list of protocols or address families,
		2130	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		2131	used, and preference will be given to protocols mentioned earlier in the
		2132	list.
		2133
		2134	This variable can effectively be used for denial-of-service attacks
		2135	against local programs (e.g. when setuid), although the impact is likely
		2136	small, as the program has to handle conenction and other failures anyways.
		2137
		2138	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		2139	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		2140	- only support IPv4, never try to resolve or contact IPv6
		2141	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		2142	IPv6, but prefer IPv6 over IPv4.
		2143
		2144	=item C<PERL_ANYEVENT_HOSTS>
		2145
		2146	This variable, if specified, overrides the F</etc/hosts> file used by
		2147	L<AnyEvent::Socket>C<::resolve_sockaddr>, i.e. hosts aliases will be read
		2148	from that file instead.
		2149
		2150	=item C<PERL_ANYEVENT_EDNS0>
		2151
		2152	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension for
		2153	DNS. This extension is generally useful to reduce DNS traffic, especially
		2154	when DNSSEC is involved, but some (broken) firewalls drop such DNS
		2155	packets, which is why it is off by default.
		2156
		2157	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		2158	EDNS0 in its DNS requests.
		2159
		2160	=item C<PERL_ANYEVENT_MAX_FORKS>
		2161
		2162	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		2163	will create in parallel.
		2164
		2165	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		2166
		2167	The default value for the C<max_outstanding> parameter for the default DNS
		2168	resolver - this is the maximum number of parallel DNS requests that are
		2169	sent to the DNS server.
		2170
		2171	=item C<PERL_ANYEVENT_RESOLV_CONF>
		2172
		2173	The absolute path to a F<resolv.conf>-style file to use instead of
		2174	F</etc/resolv.conf> (or the OS-specific configuration) in the default
		2175	resolver, or the empty string to select the default configuration.
		2176
		2177	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		2178
		2179	When neither C<ca_file> nor C<ca_path> was specified during
		2180	L<AnyEvent::TLS> context creation, and either of these environment
		2181	variables are nonempty, they will be used to specify CA certificate
		2182	locations instead of a system-dependent default.
		2183
		2184	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		2185
		2186	When these are set to C<1>, then the respective modules are not
		2187	loaded. Mostly good for testing AnyEvent itself.
		2188
		2189	=back
865		2190
866	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	2191	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
867		2192
868	This is an advanced topic that you do not normally need to use AnyEvent in	2193	This is an advanced topic that you do not normally need to use AnyEvent in
869	a module. This section is only of use to event loop authors who want to	2194	a module. This section is only of use to event loop authors who want to
…		…
903		2228
904	I<rxvt-unicode> also cheats a bit by not providing blocking access to	2229	I<rxvt-unicode> also cheats a bit by not providing blocking access to
905	condition variables: code blocking while waiting for a condition will	2230	condition variables: code blocking while waiting for a condition will
906	C<die>. This still works with most modules/usages, and blocking calls must	2231	C<die>. This still works with most modules/usages, and blocking calls must
907	not be done in an interactive application, so it makes sense.	2232	not be done in an interactive application, so it makes sense.
908
909	=head1 ENVIRONMENT VARIABLES
910
911	The following environment variables are used by this module:
912
913	=over 4
914
915	=item C<PERL_ANYEVENT_VERBOSE>
916
917	By default, AnyEvent will be completely silent except in fatal
918	conditions. You can set this environment variable to make AnyEvent more
919	talkative.
920
921	When set to C<1> or higher, causes AnyEvent to warn about unexpected
922	conditions, such as not being able to load the event model specified by
923	C<PERL_ANYEVENT_MODEL>.
924
925	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
926	model it chooses.
927
928	=item C<PERL_ANYEVENT_MODEL>
929
930	This can be used to specify the event model to be used by AnyEvent, before
931	autodetection and -probing kicks in. It must be a string consisting
932	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
933	and the resulting module name is loaded and if the load was successful,
934	used as event model. If it fails to load AnyEvent will proceed with
935	autodetection and -probing.
936
937	This functionality might change in future versions.
938
939	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
940	could start your program like this:
941
942	PERL_ANYEVENT_MODEL=Perl perl ...
943
944	=back
945		2233
946	=head1 EXAMPLE PROGRAM	2234	=head1 EXAMPLE PROGRAM
947		2235
948	The following program uses an I/O watcher to read data from STDIN, a timer	2236	The following program uses an I/O watcher to read data from STDIN, a timer
949	to display a message once per second, and a condition variable to quit the	2237	to display a message once per second, and a condition variable to quit the
…		…
958	poll => 'r',	2246	poll => 'r',
959	cb => sub {	2247	cb => sub {
960	warn "io event <$_[0]>\n"; # will always output <r>	2248	warn "io event <$_[0]>\n"; # will always output <r>
961	chomp (my $input = <STDIN>); # read a line	2249	chomp (my $input = <STDIN>); # read a line
962	warn "read: $input\n"; # output what has been read	2250	warn "read: $input\n"; # output what has been read
963	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	2251	$cv->send if $input =~ /^q/i; # quit program if /^q/i
964	},	2252	},
965	);	2253	);
966		2254
967	my $time_watcher; # can only be used once
968
969	sub new_timer {
970	$timer = AnyEvent->timer (after => 1, cb => sub {	2255	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
971	warn "timeout\n"; # print 'timeout' about every second	2256	warn "timeout\n"; # print 'timeout' at most every second
972	&new_timer; # and restart the time
973	});	2257	});
974	}
975		2258
976	new_timer; # create first timer
977
978	$cv->wait; # wait until user enters /^q/i	2259	$cv->recv; # wait until user enters /^q/i
979		2260
980	=head1 REAL-WORLD EXAMPLE	2261	=head1 REAL-WORLD EXAMPLE
981		2262
982	Consider the L<Net::FCP> module. It features (among others) the following	2263	Consider the L<Net::FCP> module. It features (among others) the following
983	API calls, which are to freenet what HTTP GET requests are to http:	2264	API calls, which are to freenet what HTTP GET requests are to http:
…		…
1033	syswrite $txn->{fh}, $txn->{request}	2314	syswrite $txn->{fh}, $txn->{request}
1034	or die "connection or write error";	2315	or die "connection or write error";
1035	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	2316	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
1036		2317
1037	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	2318	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
1038	result and signals any possible waiters that the request ahs finished:	2319	result and signals any possible waiters that the request has finished:
1039		2320
1040	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	2321	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
1041		2322
1042	if (end-of-file or data complete) {	2323	if (end-of-file or data complete) {
1043	$txn->{result} = $txn->{buf};	2324	$txn->{result} = $txn->{buf};
1044	$txn->{finished}->broadcast;	2325	$txn->{finished}->send;
1045	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	2326	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
1046	}	2327	}
1047		2328
1048	The C<result> method, finally, just waits for the finished signal (if the	2329	The C<result> method, finally, just waits for the finished signal (if the
1049	request was already finished, it doesn't wait, of course, and returns the	2330	request was already finished, it doesn't wait, of course, and returns the
1050	data:	2331	data:
1051		2332
1052	$txn->{finished}->wait;	2333	$txn->{finished}->recv;
1053	return $txn->{result};	2334	return $txn->{result};
1054		2335
1055	The actual code goes further and collects all errors (C<die>s, exceptions)	2336	The actual code goes further and collects all errors (C<die>s, exceptions)
1056	that occured during request processing. The C<result> method detects	2337	that occurred during request processing. The C<result> method detects
1057	whether an exception as thrown (it is stored inside the $txn object)	2338	whether an exception as thrown (it is stored inside the $txn object)
1058	and just throws the exception, which means connection errors and other	2339	and just throws the exception, which means connection errors and other
1059	problems get reported tot he code that tries to use the result, not in a	2340	problems get reported to the code that tries to use the result, not in a
1060	random callback.	2341	random callback.
1061		2342
1062	All of this enables the following usage styles:	2343	All of this enables the following usage styles:
1063		2344
1064	1. Blocking:	2345	1. Blocking:
…		…
1092		2373
1093	my $quit = AnyEvent->condvar;	2374	my $quit = AnyEvent->condvar;
1094		2375
1095	$fcp->txn_client_get ($url)->cb (sub {	2376	$fcp->txn_client_get ($url)->cb (sub {
1096	...	2377	...
1097	$quit->broadcast;	2378	$quit->send;
1098	});	2379	});
1099		2380
1100	$quit->wait;	2381	$quit->recv;
1101		2382
1102		2383
1103	=head1 BENCHMARKS	2384	=head1 BENCHMARKS
1104		2385
1105	To give you an idea of the performance and overheads that AnyEvent adds	2386	To give you an idea of the performance and overheads that AnyEvent adds
…		…
1107	of various event loops I prepared some benchmarks.	2388	of various event loops I prepared some benchmarks.
1108		2389
1109	=head2 BENCHMARKING ANYEVENT OVERHEAD	2390	=head2 BENCHMARKING ANYEVENT OVERHEAD
1110		2391
1111	Here is a benchmark of various supported event models used natively and	2392	Here is a benchmark of various supported event models used natively and
1112	through anyevent. The benchmark creates a lot of timers (with a zero	2393	through AnyEvent. The benchmark creates a lot of timers (with a zero
1113	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,	2394	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
1114	which it is), lets them fire exactly once and destroys them again.	2395	which it is), lets them fire exactly once and destroys them again.
1115		2396
1116	Source code for this benchmark is found as F<eg/bench> in the AnyEvent	2397	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
1117	distribution.	2398	distribution. It uses the L<AE> interface, which makes a real difference
		2399	for the EV and Perl backends only.
1118		2400
1119	=head3 Explanation of the columns	2401	=head3 Explanation of the columns
1120		2402
1121	I<watcher> is the number of event watchers created/destroyed. Since	2403	I<watcher> is the number of event watchers created/destroyed. Since
1122	different event models feature vastly different performances, each event	2404	different event models feature vastly different performances, each event
…		…
1134	all watchers, to avoid adding memory overhead. That means closure creation	2416	all watchers, to avoid adding memory overhead. That means closure creation
1135	and memory usage is not included in the figures.	2417	and memory usage is not included in the figures.
1136		2418
1137	I<invoke> is the time, in microseconds, used to invoke a simple	2419	I<invoke> is the time, in microseconds, used to invoke a simple
1138	callback. The callback simply counts down a Perl variable and after it was	2420	callback. The callback simply counts down a Perl variable and after it was
1139	invoked "watcher" times, it would C<< ->broadcast >> a condvar once to	2421	invoked "watcher" times, it would C<< ->send >> a condvar once to
1140	signal the end of this phase.	2422	signal the end of this phase.
1141		2423
1142	I<destroy> is the time, in microseconds, that it takes to destroy a single	2424	I<destroy> is the time, in microseconds, that it takes to destroy a single
1143	watcher.	2425	watcher.
1144		2426
1145	=head3 Results	2427	=head3 Results
1146		2428
1147	name watchers bytes create invoke destroy comment	2429	name watchers bytes create invoke destroy comment
1148	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	2430	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
1149	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	2431	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
1150	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	2432	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
1151	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	2433	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
1152	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	2434	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
1153	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers	2435	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
		2436	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
		2437	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
1154	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	2438	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
1155	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	2439	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
1156	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	2440	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
1157	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	2441	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
1158		2442
1159	=head3 Discussion	2443	=head3 Discussion
1160		2444
1161	The benchmark does I<not> measure scalability of the event loop very	2445	The benchmark does I<not> measure scalability of the event loop very
1162	well. For example, a select-based event loop (such as the pure perl one)	2446	well. For example, a select-based event loop (such as the pure perl one)
…		…
1174	benchmark machine, handling an event takes roughly 1600 CPU cycles with	2458	benchmark machine, handling an event takes roughly 1600 CPU cycles with
1175	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU	2459	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
1176	cycles with POE.	2460	cycles with POE.
1177		2461
1178	C<EV> is the sole leader regarding speed and memory use, which are both	2462	C<EV> is the sole leader regarding speed and memory use, which are both
1179	maximal/minimal, respectively. Even when going through AnyEvent, it uses	2463	maximal/minimal, respectively. When using the L<AE> API there is zero
		2464	overhead (when going through the AnyEvent API create is about 5-6 times
		2465	slower, with other times being equal, so still uses far less memory than
1180	far less memory than any other event loop and is still faster than Event	2466	any other event loop and is still faster than Event natively).
1181	natively.
1182		2467
1183	The pure perl implementation is hit in a few sweet spots (both the	2468	The pure perl implementation is hit in a few sweet spots (both the
1184	constant timeout and the use of a single fd hit optimisations in the perl	2469	constant timeout and the use of a single fd hit optimisations in the perl
1185	interpreter and the backend itself). Nevertheless this shows that it	2470	interpreter and the backend itself). Nevertheless this shows that it
1186	adds very little overhead in itself. Like any select-based backend its	2471	adds very little overhead in itself. Like any select-based backend its
1187	performance becomes really bad with lots of file descriptors (and few of	2472	performance becomes really bad with lots of file descriptors (and few of
1188	them active), of course, but this was not subject of this benchmark.	2473	them active), of course, but this was not subject of this benchmark.
1189		2474
1190	The C<Event> module has a relatively high setup and callback invocation	2475	The C<Event> module has a relatively high setup and callback invocation
1191	cost, but overall scores in on the third place.	2476	cost, but overall scores in on the third place.
		2477
		2478	C<IO::Async> performs admirably well, about on par with C<Event>, even
		2479	when using its pure perl backend.
1192		2480
1193	C<Glib>'s memory usage is quite a bit higher, but it features a	2481	C<Glib>'s memory usage is quite a bit higher, but it features a
1194	faster callback invocation and overall ends up in the same class as	2482	faster callback invocation and overall ends up in the same class as
1195	C<Event>. However, Glib scales extremely badly, doubling the number of	2483	C<Event>. However, Glib scales extremely badly, doubling the number of
1196	watchers increases the processing time by more than a factor of four,	2484	watchers increases the processing time by more than a factor of four,
…		…
1231	(even when used without AnyEvent), but most event loops have acceptable	2519	(even when used without AnyEvent), but most event loops have acceptable
1232	performance with or without AnyEvent.	2520	performance with or without AnyEvent.
1233		2521
1234	=item * The overhead AnyEvent adds is usually much smaller than the overhead of	2522	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
1235	the actual event loop, only with extremely fast event loops such as EV	2523	the actual event loop, only with extremely fast event loops such as EV
1236	adds AnyEvent significant overhead.	2524	does AnyEvent add significant overhead.
1237		2525
1238	=item * You should avoid POE like the plague if you want performance or	2526	=item * You should avoid POE like the plague if you want performance or
1239	reasonable memory usage.	2527	reasonable memory usage.
1240		2528
1241	=back	2529	=back
1242		2530
1243	=head2 BENCHMARKING THE LARGE SERVER CASE	2531	=head2 BENCHMARKING THE LARGE SERVER CASE
1244		2532
1245	This benchmark atcually benchmarks the event loop itself. It works by	2533	This benchmark actually benchmarks the event loop itself. It works by
1246	creating a number of "servers": each server consists of a socketpair, a	2534	creating a number of "servers": each server consists of a socket pair, a
1247	timeout watcher that gets reset on activity (but never fires), and an I/O	2535	timeout watcher that gets reset on activity (but never fires), and an I/O
1248	watcher waiting for input on one side of the socket. Each time the socket	2536	watcher waiting for input on one side of the socket. Each time the socket
1249	watcher reads a byte it will write that byte to a random other "server".	2537	watcher reads a byte it will write that byte to a random other "server".
1250		2538
1251	The effect is that there will be a lot of I/O watchers, only part of which	2539	The effect is that there will be a lot of I/O watchers, only part of which
1252	are active at any one point (so there is a constant number of active	2540	are active at any one point (so there is a constant number of active
1253	fds for each loop iterstaion, but which fds these are is random). The	2541	fds for each loop iteration, but which fds these are is random). The
1254	timeout is reset each time something is read because that reflects how	2542	timeout is reset each time something is read because that reflects how
1255	most timeouts work (and puts extra pressure on the event loops).	2543	most timeouts work (and puts extra pressure on the event loops).
1256		2544
1257	In this benchmark, we use 10000 socketpairs (20000 sockets), of which 100	2545	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
1258	(1%) are active. This mirrors the activity of large servers with many	2546	(1%) are active. This mirrors the activity of large servers with many
1259	connections, most of which are idle at any one point in time.	2547	connections, most of which are idle at any one point in time.
1260		2548
1261	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent	2549	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
1262	distribution.	2550	distribution. It uses the L<AE> interface, which makes a real difference
		2551	for the EV and Perl backends only.
1263		2552
1264	=head3 Explanation of the columns	2553	=head3 Explanation of the columns
1265		2554
1266	I<sockets> is the number of sockets, and twice the number of "servers" (as	2555	I<sockets> is the number of sockets, and twice the number of "servers" (as
1267	each server has a read and write socket end).	2556	each server has a read and write socket end).
1268		2557
1269	I<create> is the time it takes to create a socketpair (which is	2558	I<create> is the time it takes to create a socket pair (which is
1270	nontrivial) and two watchers: an I/O watcher and a timeout watcher.	2559	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
1271		2560
1272	I<request>, the most important value, is the time it takes to handle a	2561	I<request>, the most important value, is the time it takes to handle a
1273	single "request", that is, reading the token from the pipe and forwarding	2562	single "request", that is, reading the token from the pipe and forwarding
1274	it to another server. This includes deleting the old timeout and creating	2563	it to another server. This includes deleting the old timeout and creating
1275	a new one that moves the timeout into the future.	2564	a new one that moves the timeout into the future.
1276		2565
1277	=head3 Results	2566	=head3 Results
1278		2567
1279	name sockets create request	2568	name sockets create request
1280	EV 20000 69.01 11.16	2569	EV 20000 62.66 7.99
1281	Perl 20000 73.32 35.87	2570	Perl 20000 68.32 32.64
1282	Event 20000 212.62 257.32	2571	IOAsync 20000 174.06 101.15 epoll
1283	Glib 20000 651.16 1896.30	2572	IOAsync 20000 174.67 610.84 poll
		2573	Event 20000 202.69 242.91
		2574	Glib 20000 557.01 1689.52
1284	POE 20000 349.67 12317.24 uses POE::Loop::Event	2575	POE 20000 341.54 12086.32 uses POE::Loop::Event
1285		2576
1286	=head3 Discussion	2577	=head3 Discussion
1287		2578
1288	This benchmark I<does> measure scalability and overall performance of the	2579	This benchmark I<does> measure scalability and overall performance of the
1289	particular event loop.	2580	particular event loop.
…		…
1291	EV is again fastest. Since it is using epoll on my system, the setup time	2582	EV is again fastest. Since it is using epoll on my system, the setup time
1292	is relatively high, though.	2583	is relatively high, though.
1293		2584
1294	Perl surprisingly comes second. It is much faster than the C-based event	2585	Perl surprisingly comes second. It is much faster than the C-based event
1295	loops Event and Glib.	2586	loops Event and Glib.
		2587
		2588	IO::Async performs very well when using its epoll backend, and still quite
		2589	good compared to Glib when using its pure perl backend.
1296		2590
1297	Event suffers from high setup time as well (look at its code and you will	2591	Event suffers from high setup time as well (look at its code and you will
1298	understand why). Callback invocation also has a high overhead compared to	2592	understand why). Callback invocation also has a high overhead compared to
1299	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event	2593	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
1300	uses select or poll in basically all documented configurations.	2594	uses select or poll in basically all documented configurations.
…		…
1347	speed most when you have lots of watchers, not when you only have a few of	2641	speed most when you have lots of watchers, not when you only have a few of
1348	them).	2642	them).
1349		2643
1350	EV is again fastest.	2644	EV is again fastest.
1351		2645
1352	Perl again comes second. It is noticably faster than the C-based event	2646	Perl again comes second. It is noticeably faster than the C-based event
1353	loops Event and Glib, although the difference is too small to really	2647	loops Event and Glib, although the difference is too small to really
1354	matter.	2648	matter.
1355		2649
1356	POE also performs much better in this case, but is is still far behind the	2650	POE also performs much better in this case, but is is still far behind the
1357	others.	2651	others.
…		…
1363	=item * C-based event loops perform very well with small number of	2657	=item * C-based event loops perform very well with small number of
1364	watchers, as the management overhead dominates.	2658	watchers, as the management overhead dominates.
1365		2659
1366	=back	2660	=back
1367		2661
		2662	=head2 THE IO::Lambda BENCHMARK
		2663
		2664	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2665	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2666	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2667	shouldn't come as a surprise to anybody). As such, the benchmark is
		2668	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2669	very optimal. But how would AnyEvent compare when used without the extra
		2670	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2671
		2672	The benchmark itself creates an echo-server, and then, for 500 times,
		2673	connects to the echo server, sends a line, waits for the reply, and then
		2674	creates the next connection. This is a rather bad benchmark, as it doesn't
		2675	test the efficiency of the framework or much non-blocking I/O, but it is a
		2676	benchmark nevertheless.
		2677
		2678	name runtime
		2679	Lambda/select 0.330 sec
		2680	+ optimized 0.122 sec
		2681	Lambda/AnyEvent 0.327 sec
		2682	+ optimized 0.138 sec
		2683	Raw sockets/select 0.077 sec
		2684	POE/select, components 0.662 sec
		2685	POE/select, raw sockets 0.226 sec
		2686	POE/select, optimized 0.404 sec
		2687
		2688	AnyEvent/select/nb 0.085 sec
		2689	AnyEvent/EV/nb 0.068 sec
		2690	+state machine 0.134 sec
		2691
		2692	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2693	benchmarks actually make blocking connects and use 100% blocking I/O,
		2694	defeating the purpose of an event-based solution. All of the newly
		2695	written AnyEvent benchmarks use 100% non-blocking connects (using
		2696	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2697	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2698	generally require a lot more bookkeeping and event handling than blocking
		2699	connects (which involve a single syscall only).
		2700
		2701	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2702	offers similar expressive power as POE and IO::Lambda, using conventional
		2703	Perl syntax. This means that both the echo server and the client are 100%
		2704	non-blocking, further placing it at a disadvantage.
		2705
		2706	As you can see, the AnyEvent + EV combination even beats the
		2707	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2708	backend easily beats IO::Lambda and POE.
		2709
		2710	And even the 100% non-blocking version written using the high-level (and
		2711	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda
		2712	higher level ("unoptimised") abstractions by a large margin, even though
		2713	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
		2714
		2715	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2716	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2717	part of the IO::Lambda distribution and were used without any changes.
		2718
		2719
		2720	=head1 SIGNALS
		2721
		2722	AnyEvent currently installs handlers for these signals:
		2723
		2724	=over 4
		2725
		2726	=item SIGCHLD
		2727
		2728	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2729	emulation for event loops that do not support them natively. Also, some
		2730	event loops install a similar handler.
		2731
		2732	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2733	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2734
		2735	=item SIGPIPE
		2736
		2737	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2738	when AnyEvent gets loaded.
		2739
		2740	The rationale for this is that AnyEvent users usually do not really depend
		2741	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2742	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2743	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2744	some random socket.
		2745
		2746	The rationale for installing a no-op handler as opposed to ignoring it is
		2747	that this way, the handler will be restored to defaults on exec.
		2748
		2749	Feel free to install your own handler, or reset it to defaults.
		2750
		2751	=back
		2752
		2753	=cut
		2754
		2755	undef $SIG{CHLD}
		2756	if $SIG{CHLD} eq 'IGNORE';
		2757
		2758	$SIG{PIPE} = sub { }
		2759	unless defined $SIG{PIPE};
		2760
		2761	=head1 RECOMMENDED/OPTIONAL MODULES
		2762
		2763	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2764	its built-in modules) are required to use it.
		2765
		2766	That does not mean that AnyEvent won't take advantage of some additional
		2767	modules if they are installed.
		2768
		2769	This section explains which additional modules will be used, and how they
		2770	affect AnyEvent's operation.
		2771
		2772	=over 4
		2773
		2774	=item L<Async::Interrupt>
		2775
		2776	This slightly arcane module is used to implement fast signal handling: To
		2777	my knowledge, there is no way to do completely race-free and quick
		2778	signal handling in pure perl. To ensure that signals still get
		2779	delivered, AnyEvent will start an interval timer to wake up perl (and
		2780	catch the signals) with some delay (default is 10 seconds, look for
		2781	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2782
		2783	If this module is available, then it will be used to implement signal
		2784	catching, which means that signals will not be delayed, and the event loop
		2785	will not be interrupted regularly, which is more efficient (and good for
		2786	battery life on laptops).
		2787
		2788	This affects not just the pure-perl event loop, but also other event loops
		2789	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2790
		2791	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2792	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2793	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2794	does nothing for those backends.
		2795
		2796	=item L<EV>
		2797
		2798	This module isn't really "optional", as it is simply one of the backend
		2799	event loops that AnyEvent can use. However, it is simply the best event
		2800	loop available in terms of features, speed and stability: It supports
		2801	the AnyEvent API optimally, implements all the watcher types in XS, does
		2802	automatic timer adjustments even when no monotonic clock is available,
		2803	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2804	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2805	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2806
		2807	If you only use backends that rely on another event loop (e.g. C<Tk>),
		2808	then this module will do nothing for you.
		2809
		2810	=item L<Guard>
		2811
		2812	The guard module, when used, will be used to implement
		2813	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2814	lot less memory), but otherwise doesn't affect guard operation much. It is
		2815	purely used for performance.
		2816
		2817	=item L<JSON> and L<JSON::XS>
		2818
		2819	One of these modules is required when you want to read or write JSON data
		2820	via L<AnyEvent::Handle>. L<JSON> is also written in pure-perl, but can take
		2821	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2822
		2823	=item L<Net::SSLeay>
		2824
		2825	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2826	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2827	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2828
		2829	=item L<Time::HiRes>
		2830
		2831	This module is part of perl since release 5.008. It will be used when the
		2832	chosen event library does not come with a timing source of its own. The
		2833	pure-perl event loop (L<AnyEvent::Loop>) will additionally load it to
		2834	try to use a monotonic clock for timing stability.
		2835
		2836	=back
		2837
1368		2838
1369	=head1 FORK	2839	=head1 FORK
1370		2840
1371	Most event libraries are not fork-safe. The ones who are usually are	2841	Most event libraries are not fork-safe. The ones who are usually are
1372	because they rely on inefficient but fork-safe C<select> or C<poll>	2842	because they rely on inefficient but fork-safe C<select> or C<poll> calls
1373	calls. Only L<EV> is fully fork-aware.	2843	- higher performance APIs such as BSD's kqueue or the dreaded Linux epoll
		2844	are usually badly thought-out hacks that are incompatible with fork in
		2845	one way or another. Only L<EV> is fully fork-aware and ensures that you
		2846	continue event-processing in both parent and child (or both, if you know
		2847	what you are doing).
		2848
		2849	This means that, in general, you cannot fork and do event processing in
		2850	the child if the event library was initialised before the fork (which
		2851	usually happens when the first AnyEvent watcher is created, or the library
		2852	is loaded).
1374		2853
1375	If you have to fork, you must either do so I<before> creating your first	2854	If you have to fork, you must either do so I<before> creating your first
1376	watcher OR you must not use AnyEvent at all in the child.	2855	watcher OR you must not use AnyEvent at all in the child OR you must do
		2856	something completely out of the scope of AnyEvent.
		2857
		2858	The problem of doing event processing in the parent I<and> the child
		2859	is much more complicated: even for backends that I<are> fork-aware or
		2860	fork-safe, their behaviour is not usually what you want: fork clones all
		2861	watchers, that means all timers, I/O watchers etc. are active in both
		2862	parent and child, which is almost never what you want. USing C<exec>
		2863	to start worker children from some kind of manage rprocess is usually
		2864	preferred, because it is much easier and cleaner, at the expense of having
		2865	to have another binary.
1377		2866
1378		2867
1379	=head1 SECURITY CONSIDERATIONS	2868	=head1 SECURITY CONSIDERATIONS
1380		2869
1381	AnyEvent can be forced to load any event model via	2870	AnyEvent can be forced to load any event model via
…		…
1386	specified in the variable.	2875	specified in the variable.
1387		2876
1388	You can make AnyEvent completely ignore this variable by deleting it	2877	You can make AnyEvent completely ignore this variable by deleting it
1389	before the first watcher gets created, e.g. with a C<BEGIN> block:	2878	before the first watcher gets created, e.g. with a C<BEGIN> block:
1390		2879
1391	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	2880	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1392		2881
1393	use AnyEvent;	2882	use AnyEvent;
		2883
		2884	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		2885	be used to probe what backend is used and gain other information (which is
		2886	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2887	$ENV{PERL_ANYEVENT_STRICT}.
		2888
		2889	Note that AnyEvent will remove I<all> environment variables starting with
		2890	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2891	enabled.
		2892
		2893
		2894	=head1 BUGS
		2895
		2896	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2897	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2898	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2899	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2900	pronounced).
1394		2901
1395		2902
1396	=head1 SEE ALSO	2903	=head1 SEE ALSO
1397		2904
1398	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	2905	Tutorial/Introduction: L<AnyEvent::Intro>.
1399	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,
1400	L<Event::Lib>, L<Qt>, L<POE>.
1401		2906
1402	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	2907	FAQ: L<AnyEvent::FAQ>.
		2908
		2909	Utility functions: L<AnyEvent::Util> (misc. grab-bag), L<AnyEvent::Log>
		2910	(simply logging).
		2911
		2912	Development/Debugging: L<AnyEvent::Strict> (stricter checking),
		2913	L<AnyEvent::Debug> (interactive shell, watcher tracing).
		2914
		2915	Supported event modules: L<AnyEvent::Loop>, L<EV>, L<EV::Glib>,
		2916	L<Glib::EV>, L<Event>, L<Glib::Event>, L<Glib>, L<Tk>, L<Event::Lib>,
		2917	L<Qt>, L<POE>, L<FLTK>.
		2918
		2919	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
		2920	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
		2921	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1403	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,	2922	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>, L<Anyevent::Impl::Irssi>,
1404	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,	2923	L<AnyEvent::Impl::FLTK>.
1405	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.
1406		2924
		2925	Non-blocking handles, pipes, stream sockets, TCP clients and
		2926	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
		2927
		2928	Asynchronous DNS: L<AnyEvent::DNS>.
		2929
		2930	Thread support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>.
		2931
1407	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	2932	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::IRC>,
		2933	L<AnyEvent::HTTP>.
1408		2934
1409		2935
1410	=head1 AUTHOR	2936	=head1 AUTHOR
1411		2937
1412	Marc Lehmann <schmorp@schmorp.de>	2938	Marc Lehmann <schmorp@schmorp.de>
1413	http://home.schmorp.de/	2939	http://home.schmorp.de/
1414		2940
1415	=cut	2941	=cut
1416		2942
1417	1	2943	1
1418		2944

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