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Revision 1.317 by root, Wed Mar 24 21:22:57 2010 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent - provide framework for multiple event loops	3	AnyEvent - the DBI of event loop programming
4		4
5	EV, Event, Coro::EV, Coro::Event, Glib, Tk, Perl - various supported event loops	5	EV, Event, Glib, Tk, Perl, Event::Lib, Irssi, rxvt-unicode, IO::Async, Qt
		6	and POE are various supported event loops/environments.
6		7
7	=head1 SYNOPSIS	8	=head1 SYNOPSIS
8		9
9	use AnyEvent;	10	use AnyEvent;
10		11
		12	# file descriptor readable
11	my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub {	13	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
		14
		15	# one-shot or repeating timers
		16	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
		17	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...
		18
		19	print AnyEvent->now; # prints current event loop time
		20	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
		21
		22	# POSIX signal
		23	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
		24
		25	# child process exit
		26	my $w = AnyEvent->child (pid => $pid, cb => sub {
		27	my ($pid, $status) = @_;
12	...	28	...
13	});	29	});
14		30
15	my $w = AnyEvent->timer (after => $seconds, cb => sub {	31	# called when event loop idle (if applicable)
16	...	32	my $w = AnyEvent->idle (cb => sub { ... });
17	});
18		33
19	my $w = AnyEvent->condvar; # stores whether a condition was flagged	34	my $w = AnyEvent->condvar; # stores whether a condition was flagged
		35	$w->send; # wake up current and all future recv's
20	$w->wait; # enters "main loop" till $condvar gets ->broadcast	36	$w->recv; # enters "main loop" till $condvar gets ->send
21	$w->broadcast; # wake up current and all future wait's	37	# use a condvar in callback mode:
		38	$w->cb (sub { $_[0]->recv });
		39
		40	=head1 INTRODUCTION/TUTORIAL
		41
		42	This manpage is mainly a reference manual. If you are interested
		43	in a tutorial or some gentle introduction, have a look at the
		44	L<AnyEvent::Intro> manpage.
		45
		46	=head1 SUPPORT
		47
		48	There is a mailinglist for discussing all things AnyEvent, and an IRC
		49	channel, too.
		50
		51	See the AnyEvent project page at the B<Schmorpforge Ta-Sa Software
		52	Repository>, at L<http://anyevent.schmorp.de>, for more info.
22		53
23	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)	54	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
24		55
25	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	56	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
26	nowadays. So what is different about AnyEvent?	57	nowadays. So what is different about AnyEvent?
27		58
28	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of	59	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
29	policy> and AnyEvent is I<small and efficient>.	60	policy> and AnyEvent is I<small and efficient>.
30		61
31	First and foremost, I<AnyEvent is not an event model> itself, it only	62	First and foremost, I<AnyEvent is not an event model> itself, it only
32	interfaces to whatever event model the main program happens to use in a	63	interfaces to whatever event model the main program happens to use, in a
33	pragmatic way. For event models and certain classes of immortals alike,	64	pragmatic way. For event models and certain classes of immortals alike,
34	the statement "there can only be one" is a bitter reality: In general,	65	the statement "there can only be one" is a bitter reality: In general,
35	only one event loop can be active at the same time in a process. AnyEvent	66	only one event loop can be active at the same time in a process. AnyEvent
36	helps hiding the differences between those event loops.	67	cannot change this, but it can hide the differences between those event
		68	loops.
37		69
38	The goal of AnyEvent is to offer module authors the ability to do event	70	The goal of AnyEvent is to offer module authors the ability to do event
39	programming (waiting for I/O or timer events) without subscribing to a	71	programming (waiting for I/O or timer events) without subscribing to a
40	religion, a way of living, and most importantly: without forcing your	72	religion, a way of living, and most importantly: without forcing your
41	module users into the same thing by forcing them to use the same event	73	module users into the same thing by forcing them to use the same event
42	model you use.	74	model you use.
43		75
44	For modules like POE or IO::Async (which is a total misnomer as it is	76	For modules like POE or IO::Async (which is a total misnomer as it is
45	actually doing all I/O I<synchronously>...), using them in your module is	77	actually doing all I/O I<synchronously>...), using them in your module is
46	like joining a cult: After you joined, you are dependent on them and you	78	like joining a cult: After you joined, you are dependent on them and you
47	cannot use anything else, as it is simply incompatible to everything that	79	cannot use anything else, as they are simply incompatible to everything
48	isn't itself. What's worse, all the potential users of your module are	80	that isn't them. What's worse, all the potential users of your
49	I<also> forced to use the same event loop you use.	81	module are I<also> forced to use the same event loop you use.
50		82
51	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	83	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
52	fine. AnyEvent + Tk works fine etc. etc. but none of these work together	84	fine. AnyEvent + Tk works fine etc. etc. but none of these work together
53	with the rest: POE + IO::Async? no go. Tk + Event? no go. Again: if	85	with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if
54	your module uses one of those, every user of your module has to use it,	86	your module uses one of those, every user of your module has to use it,
55	too. But if your module uses AnyEvent, it works transparently with all	87	too. But if your module uses AnyEvent, it works transparently with all
56	event models it supports (including stuff like POE and IO::Async, as long	88	event models it supports (including stuff like IO::Async, as long as those
57	as those use one of the supported event loops. It is trivial to add new	89	use one of the supported event loops. It is trivial to add new event loops
58	event loops to AnyEvent, too, so it is future-proof).	90	to AnyEvent, too, so it is future-proof).
59		91
60	In addition to being free of having to use I<the one and only true event	92	In addition to being free of having to use I<the one and only true event
61	model>, AnyEvent also is free of bloat and policy: with POE or similar	93	model>, AnyEvent also is free of bloat and policy: with POE or similar
62	modules, you get an enourmous amount of code and strict rules you have to	94	modules, you get an enormous amount of code and strict rules you have to
63	follow. AnyEvent, on the other hand, is lean and up to the point, by only	95	follow. AnyEvent, on the other hand, is lean and up to the point, by only
64	offering the functionality that is necessary, in as thin as a wrapper as	96	offering the functionality that is necessary, in as thin as a wrapper as
65	technically possible.	97	technically possible.
66		98
		99	Of course, AnyEvent comes with a big (and fully optional!) toolbox
		100	of useful functionality, such as an asynchronous DNS resolver, 100%
		101	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
		102	such as Windows) and lots of real-world knowledge and workarounds for
		103	platform bugs and differences.
		104
67	Of course, if you want lots of policy (this can arguably be somewhat	105	Now, if you I<do want> lots of policy (this can arguably be somewhat
68	useful) and you want to force your users to use the one and only event	106	useful) and you want to force your users to use the one and only event
69	model, you should I<not> use this module.	107	model, you should I<not> use this module.
70
71		108
72	=head1 DESCRIPTION	109	=head1 DESCRIPTION
73		110
74	L<AnyEvent> provides an identical interface to multiple event loops. This	111	L<AnyEvent> provides an identical interface to multiple event loops. This
75	allows module authors to utilise an event loop without forcing module	112	allows module authors to utilise an event loop without forcing module
…		…
79	The interface itself is vaguely similar, but not identical to the L<Event>	116	The interface itself is vaguely similar, but not identical to the L<Event>
80	module.	117	module.
81		118
82	During the first call of any watcher-creation method, the module tries	119	During the first call of any watcher-creation method, the module tries
83	to detect the currently loaded event loop by probing whether one of the	120	to detect the currently loaded event loop by probing whether one of the
84	following modules is already loaded: L<Coro::EV>, L<Coro::Event>, L<EV>,	121	following modules is already loaded: L<EV>,
85	L<Event>, L<Glib>, L<Tk>. The first one found is used. If none are found,	122	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,
86	the module tries to load these modules in the stated order. The first one	123	L<POE>. The first one found is used. If none are found, the module tries
		124	to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl
		125	adaptor should always succeed) in the order given. The first one that can
87	that can be successfully loaded will be used. If, after this, still none	126	be successfully loaded will be used. If, after this, still none could be
88	could be found, AnyEvent will fall back to a pure-perl event loop, which	127	found, AnyEvent will fall back to a pure-perl event loop, which is not
89	is not very efficient, but should work everywhere.	128	very efficient, but should work everywhere.
90		129
91	Because AnyEvent first checks for modules that are already loaded, loading	130	Because AnyEvent first checks for modules that are already loaded, loading
92	an event model explicitly before first using AnyEvent will likely make	131	an event model explicitly before first using AnyEvent will likely make
93	that model the default. For example:	132	that model the default. For example:
94		133
…		…
101	starts using it, all bets are off. Maybe you should tell their authors to	140	starts using it, all bets are off. Maybe you should tell their authors to
102	use AnyEvent so their modules work together with others seamlessly...	141	use AnyEvent so their modules work together with others seamlessly...
103		142
104	The pure-perl implementation of AnyEvent is called	143	The pure-perl implementation of AnyEvent is called
105	C<AnyEvent::Impl::Perl>. Like other event modules you can load it	144	C<AnyEvent::Impl::Perl>. Like other event modules you can load it
106	explicitly.	145	explicitly and enjoy the high availability of that event loop :)
107		146
108	=head1 WATCHERS	147	=head1 WATCHERS
109		148
110	AnyEvent has the central concept of a I<watcher>, which is an object that	149	AnyEvent has the central concept of a I<watcher>, which is an object that
111	stores relevant data for each kind of event you are waiting for, such as	150	stores relevant data for each kind of event you are waiting for, such as
112	the callback to call, the filehandle to watch, etc.	151	the callback to call, the file handle to watch, etc.
113		152
114	These watchers are normal Perl objects with normal Perl lifetime. After	153	These watchers are normal Perl objects with normal Perl lifetime. After
115	creating a watcher it will immediately "watch" for events and invoke the	154	creating a watcher it will immediately "watch" for events and invoke the
116	callback when the event occurs (of course, only when the event model	155	callback when the event occurs (of course, only when the event model
117	is in control).	156	is in control).
118		157
		158	Note that B<callbacks must not permanently change global variables>
		159	potentially in use by the event loop (such as C<$_> or C<$[>) and that B<<
		160	callbacks must not C<die> >>. The former is good programming practise in
		161	Perl and the latter stems from the fact that exception handling differs
		162	widely between event loops.
		163
119	To disable the watcher you have to destroy it (e.g. by setting the	164	To disable the watcher you have to destroy it (e.g. by setting the
120	variable you store it in to C<undef> or otherwise deleting all references	165	variable you store it in to C<undef> or otherwise deleting all references
121	to it).	166	to it).
122		167
123	All watchers are created by calling a method on the C<AnyEvent> class.	168	All watchers are created by calling a method on the C<AnyEvent> class.
…		…
125	Many watchers either are used with "recursion" (repeating timers for	170	Many watchers either are used with "recursion" (repeating timers for
126	example), or need to refer to their watcher object in other ways.	171	example), or need to refer to their watcher object in other ways.
127		172
128	An any way to achieve that is this pattern:	173	An any way to achieve that is this pattern:
129		174
130	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	175	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
131	# you can use $w here, for example to undef it	176	# you can use $w here, for example to undef it
132	undef $w;	177	undef $w;
133	});	178	});
134		179
135	Note that C<my $w; $w => combination. This is necessary because in Perl,	180	Note that C<my $w; $w => combination. This is necessary because in Perl,
136	my variables are only visible after the statement in which they are	181	my variables are only visible after the statement in which they are
137	declared.	182	declared.
138		183
139	=head2 IO WATCHERS	184	=head2 I/O WATCHERS
		185
		186	$w = AnyEvent->io (
		187	fh => <filehandle_or_fileno>,
		188	poll => <"r" or "w">,
		189	cb => <callback>,
		190	);
140		191
141	You can create an I/O watcher by calling the C<< AnyEvent->io >> method	192	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
142	with the following mandatory key-value pairs as arguments:	193	with the following mandatory key-value pairs as arguments:
143		194
144	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch for	195	C<fh> is the Perl I<file handle> (or a naked file descriptor) to watch
		196	for events (AnyEvent might or might not keep a reference to this file
		197	handle). Note that only file handles pointing to things for which
		198	non-blocking operation makes sense are allowed. This includes sockets,
		199	most character devices, pipes, fifos and so on, but not for example files
		200	or block devices.
		201
145	events. C<poll> must be a string that is either C<r> or C<w>, which	202	C<poll> must be a string that is either C<r> or C<w>, which creates a
146	creates a watcher waiting for "r"eadable or "w"ritable events,	203	watcher waiting for "r"eadable or "w"ritable events, respectively.
		204
147	respectively. C<cb> is the callback to invoke each time the file handle	205	C<cb> is the callback to invoke each time the file handle becomes ready.
148	becomes ready.
149		206
150	File handles will be kept alive, so as long as the watcher exists, the	207	Although the callback might get passed parameters, their value and
151	file handle exists, too.	208	presence is undefined and you cannot rely on them. Portable AnyEvent
		209	callbacks cannot use arguments passed to I/O watcher callbacks.
152		210
		211	The I/O watcher might use the underlying file descriptor or a copy of it.
153	It is not allowed to close a file handle as long as any watcher is active	212	You must not close a file handle as long as any watcher is active on the
154	on the underlying file descriptor.	213	underlying file descriptor.
155		214
156	Some event loops issue spurious readyness notifications, so you should	215	Some event loops issue spurious readyness notifications, so you should
157	always use non-blocking calls when reading/writing from/to your file	216	always use non-blocking calls when reading/writing from/to your file
158	handles.	217	handles.
159		218
160	Example:
161
162	# wait for readability of STDIN, then read a line and disable the watcher	219	Example: wait for readability of STDIN, then read a line and disable the
		220	watcher.
		221
163	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	222	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
164	chomp (my $input = <STDIN>);	223	chomp (my $input = <STDIN>);
165	warn "read: $input\n";	224	warn "read: $input\n";
166	undef $w;	225	undef $w;
167	});	226	});
168		227
169	=head2 TIME WATCHERS	228	=head2 TIME WATCHERS
170		229
		230	$w = AnyEvent->timer (after => <seconds>, cb => <callback>);
		231
		232	$w = AnyEvent->timer (
		233	after => <fractional_seconds>,
		234	interval => <fractional_seconds>,
		235	cb => <callback>,
		236	);
		237
171	You can create a time watcher by calling the C<< AnyEvent->timer >>	238	You can create a time watcher by calling the C<< AnyEvent->timer >>
172	method with the following mandatory arguments:	239	method with the following mandatory arguments:
173		240
174	C<after> specifies after how many seconds (fractional values are	241	C<after> specifies after how many seconds (fractional values are
175	supported) should the timer activate. C<cb> the callback to invoke in that	242	supported) the callback should be invoked. C<cb> is the callback to invoke
176	case.	243	in that case.
177		244
178	The timer callback will be invoked at most once: if you want a repeating	245	Although the callback might get passed parameters, their value and
179	timer you have to create a new watcher (this is a limitation by both Tk	246	presence is undefined and you cannot rely on them. Portable AnyEvent
180	and Glib).	247	callbacks cannot use arguments passed to time watcher callbacks.
181		248
182	Example:	249	The callback will normally be invoked once only. If you specify another
		250	parameter, C<interval>, as a strictly positive number (> 0), then the
		251	callback will be invoked regularly at that interval (in fractional
		252	seconds) after the first invocation. If C<interval> is specified with a
		253	false value, then it is treated as if it were missing.
183		254
		255	The callback will be rescheduled before invoking the callback, but no
		256	attempt is done to avoid timer drift in most backends, so the interval is
		257	only approximate.
		258
184	# fire an event after 7.7 seconds	259	Example: fire an event after 7.7 seconds.
		260
185	my $w = AnyEvent->timer (after => 7.7, cb => sub {	261	my $w = AnyEvent->timer (after => 7.7, cb => sub {
186	warn "timeout\n";	262	warn "timeout\n";
187	});	263	});
188		264
189	# to cancel the timer:	265	# to cancel the timer:
190	undef $w;	266	undef $w;
191		267
192	Example 2:
193
194	# fire an event after 0.5 seconds, then roughly every second	268	Example 2: fire an event after 0.5 seconds, then roughly every second.
195	my $w;
196		269
197	my $cb = sub {
198	# cancel the old timer while creating a new one
199	$w = AnyEvent->timer (after => 1, cb => $cb);	270	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		271	warn "timeout\n";
200	};	272	};
201
202	# start the "loop" by creating the first watcher
203	$w = AnyEvent->timer (after => 0.5, cb => $cb);
204		273
205	=head3 TIMING ISSUES	274	=head3 TIMING ISSUES
206		275
207	There are two ways to handle timers: based on real time (relative, "fire	276	There are two ways to handle timers: based on real time (relative, "fire
208	in 10 seconds") and based on wallclock time (absolute, "fire at 12	277	in 10 seconds") and based on wallclock time (absolute, "fire at 12
209	o'clock").	278	o'clock").
210		279
211	While most event loops expect timers to specified in a relative way, they use	280	While most event loops expect timers to specified in a relative way, they
212	absolute time internally. This makes a difference when your clock "jumps",	281	use absolute time internally. This makes a difference when your clock
213	for example, when ntp decides to set your clock backwards from the wrong 2014-01-01 to	282	"jumps", for example, when ntp decides to set your clock backwards from
214	2008-01-01, a watcher that you created to fire "after" a second might actually take	283	the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to
215	six years to finally fire.	284	fire "after" a second might actually take six years to finally fire.
216		285
217	AnyEvent cannot compensate for this. The only event loop that is conscious	286	AnyEvent cannot compensate for this. The only event loop that is conscious
218	about these issues is L<EV>, which offers both relative (ev_timer) and	287	about these issues is L<EV>, which offers both relative (ev_timer, based
219	absolute (ev_periodic) timers.	288	on true relative time) and absolute (ev_periodic, based on wallclock time)
		289	timers.
220		290
221	AnyEvent always prefers relative timers, if available, matching the	291	AnyEvent always prefers relative timers, if available, matching the
222	AnyEvent API.	292	AnyEvent API.
223		293
		294	AnyEvent has two additional methods that return the "current time":
		295
		296	=over 4
		297
		298	=item AnyEvent->time
		299
		300	This returns the "current wallclock time" as a fractional number of
		301	seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
		302	return, and the result is guaranteed to be compatible with those).
		303
		304	It progresses independently of any event loop processing, i.e. each call
		305	will check the system clock, which usually gets updated frequently.
		306
		307	=item AnyEvent->now
		308
		309	This also returns the "current wallclock time", but unlike C<time>, above,
		310	this value might change only once per event loop iteration, depending on
		311	the event loop (most return the same time as C<time>, above). This is the
		312	time that AnyEvent's timers get scheduled against.
		313
		314	I<In almost all cases (in all cases if you don't care), this is the
		315	function to call when you want to know the current time.>
		316
		317	This function is also often faster then C<< AnyEvent->time >>, and
		318	thus the preferred method if you want some timestamp (for example,
		319	L<AnyEvent::Handle> uses this to update it's activity timeouts).
		320
		321	The rest of this section is only of relevance if you try to be very exact
		322	with your timing, you can skip it without bad conscience.
		323
		324	For a practical example of when these times differ, consider L<Event::Lib>
		325	and L<EV> and the following set-up:
		326
		327	The event loop is running and has just invoked one of your callback at
		328	time=500 (assume no other callbacks delay processing). In your callback,
		329	you wait a second by executing C<sleep 1> (blocking the process for a
		330	second) and then (at time=501) you create a relative timer that fires
		331	after three seconds.
		332
		333	With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
		334	both return C<501>, because that is the current time, and the timer will
		335	be scheduled to fire at time=504 (C<501> + C<3>).
		336
		337	With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
		338	time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
		339	last event processing phase started. With L<EV>, your timer gets scheduled
		340	to run at time=503 (C<500> + C<3>).
		341
		342	In one sense, L<Event::Lib> is more exact, as it uses the current time
		343	regardless of any delays introduced by event processing. However, most
		344	callbacks do not expect large delays in processing, so this causes a
		345	higher drift (and a lot more system calls to get the current time).
		346
		347	In another sense, L<EV> is more exact, as your timer will be scheduled at
		348	the same time, regardless of how long event processing actually took.
		349
		350	In either case, if you care (and in most cases, you don't), then you
		351	can get whatever behaviour you want with any event loop, by taking the
		352	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
		353	account.
		354
		355	=item AnyEvent->now_update
		356
		357	Some event loops (such as L<EV> or L<AnyEvent::Impl::Perl>) cache
		358	the current time for each loop iteration (see the discussion of L<<
		359	AnyEvent->now >>, above).
		360
		361	When a callback runs for a long time (or when the process sleeps), then
		362	this "current" time will differ substantially from the real time, which
		363	might affect timers and time-outs.
		364
		365	When this is the case, you can call this method, which will update the
		366	event loop's idea of "current time".
		367
		368	A typical example would be a script in a web server (e.g. C<mod_perl>) -
		369	when mod_perl executes the script, then the event loop will have the wrong
		370	idea about the "current time" (being potentially far in the past, when the
		371	script ran the last time). In that case you should arrange a call to C<<
		372	AnyEvent->now_update >> each time the web server process wakes up again
		373	(e.g. at the start of your script, or in a handler).
		374
		375	Note that updating the time I<might> cause some events to be handled.
		376
		377	=back
		378
224	=head2 SIGNAL WATCHERS	379	=head2 SIGNAL WATCHERS
225		380
		381	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		382
226	You can watch for signals using a signal watcher, C<signal> is the signal	383	You can watch for signals using a signal watcher, C<signal> is the signal
227	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to	384	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
228	be invoked whenever a signal occurs.	385	callback to be invoked whenever a signal occurs.
229		386
		387	Although the callback might get passed parameters, their value and
		388	presence is undefined and you cannot rely on them. Portable AnyEvent
		389	callbacks cannot use arguments passed to signal watcher callbacks.
		390
230	Multiple signals occurances can be clumped together into one callback	391	Multiple signal occurrences can be clumped together into one callback
231	invocation, and callback invocation will be synchronous. synchronous means	392	invocation, and callback invocation will be synchronous. Synchronous means
232	that it might take a while until the signal gets handled by the process,	393	that it might take a while until the signal gets handled by the process,
233	but it is guarenteed not to interrupt any other callbacks.	394	but it is guaranteed not to interrupt any other callbacks.
234		395
235	The main advantage of using these watchers is that you can share a signal	396	The main advantage of using these watchers is that you can share a signal
236	between multiple watchers.	397	between multiple watchers, and AnyEvent will ensure that signals will not
		398	interrupt your program at bad times.
237		399
238	This watcher might use C<%SIG>, so programs overwriting those signals	400	This watcher might use C<%SIG> (depending on the event loop used),
239	directly will likely not work correctly.	401	so programs overwriting those signals directly will likely not work
		402	correctly.
240		403
241	Example: exit on SIGINT	404	Example: exit on SIGINT
242		405
243	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	406	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
244		407
		408	=head3 Restart Behaviour
		409
		410	While restart behaviour is up to the event loop implementation, most will
		411	not restart syscalls (that includes L<Async::Interrupt> and AnyEvent's
		412	pure perl implementation).
		413
		414	=head3 Safe/Unsafe Signals
		415
		416	Perl signals can be either "safe" (synchronous to opcode handling) or
		417	"unsafe" (asynchronous) - the former might get delayed indefinitely, the
		418	latter might corrupt your memory.
		419
		420	AnyEvent signal handlers are, in addition, synchronous to the event loop,
		421	i.e. they will not interrupt your running perl program but will only be
		422	called as part of the normal event handling (just like timer, I/O etc.
		423	callbacks, too).
		424
		425	=head3 Signal Races, Delays and Workarounds
		426
		427	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		428	callbacks to signals in a generic way, which is a pity, as you cannot
		429	do race-free signal handling in perl, requiring C libraries for
		430	this. AnyEvent will try to do it's best, which means in some cases,
		431	signals will be delayed. The maximum time a signal might be delayed is
		432	specified in C<$AnyEvent::MAX_SIGNAL_LATENCY> (default: 10 seconds). This
		433	variable can be changed only before the first signal watcher is created,
		434	and should be left alone otherwise. This variable determines how often
		435	AnyEvent polls for signals (in case a wake-up was missed). Higher values
		436	will cause fewer spurious wake-ups, which is better for power and CPU
		437	saving.
		438
		439	All these problems can be avoided by installing the optional
		440	L<Async::Interrupt> module, which works with most event loops. It will not
		441	work with inherently broken event loops such as L<Event> or L<Event::Lib>
		442	(and not with L<POE> currently, as POE does it's own workaround with
		443	one-second latency). For those, you just have to suffer the delays.
		444
245	=head2 CHILD PROCESS WATCHERS	445	=head2 CHILD PROCESS WATCHERS
246		446
		447	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		448
247	You can also watch on a child process exit and catch its exit status.	449	You can also watch on a child process exit and catch its exit status.
248		450
249	The child process is specified by the C<pid> argument (if set to C<0>, it	451	The child process is specified by the C<pid> argument (one some backends,
250	watches for any child process exit). The watcher will trigger as often	452	using C<0> watches for any child process exit, on others this will
251	as status change for the child are received. This works by installing a	453	croak). The watcher will be triggered only when the child process has
252	signal handler for C<SIGCHLD>. The callback will be called with the pid	454	finished and an exit status is available, not on any trace events
253	and exit status (as returned by waitpid).	455	(stopped/continued).
254		456
255	Example: wait for pid 1333	457	The callback will be called with the pid and exit status (as returned by
		458	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		459	callback arguments.
256		460
		461	This watcher type works by installing a signal handler for C<SIGCHLD>,
		462	and since it cannot be shared, nothing else should use SIGCHLD or reap
		463	random child processes (waiting for specific child processes, e.g. inside
		464	C<system>, is just fine).
		465
		466	There is a slight catch to child watchers, however: you usually start them
		467	I<after> the child process was created, and this means the process could
		468	have exited already (and no SIGCHLD will be sent anymore).
		469
		470	Not all event models handle this correctly (neither POE nor IO::Async do,
		471	see their AnyEvent::Impl manpages for details), but even for event models
		472	that I<do> handle this correctly, they usually need to be loaded before
		473	the process exits (i.e. before you fork in the first place). AnyEvent's
		474	pure perl event loop handles all cases correctly regardless of when you
		475	start the watcher.
		476
		477	This means you cannot create a child watcher as the very first
		478	thing in an AnyEvent program, you I<have> to create at least one
		479	watcher before you C<fork> the child (alternatively, you can call
		480	C<AnyEvent::detect>).
		481
		482	As most event loops do not support waiting for child events, they will be
		483	emulated by AnyEvent in most cases, in which the latency and race problems
		484	mentioned in the description of signal watchers apply.
		485
		486	Example: fork a process and wait for it
		487
		488	my $done = AnyEvent->condvar;
		489
		490	my $pid = fork or exit 5;
		491
257	my $w = AnyEvent->child (	492	my $w = AnyEvent->child (
258	pid => 1333,	493	pid => $pid,
259	cb => sub {	494	cb => sub {
260	my ($pid, $status) = @_;	495	my ($pid, $status) = @_;
261	warn "pid $pid exited with status $status";	496	warn "pid $pid exited with status $status";
		497	$done->send;
262	},	498	},
263	);	499	);
		500
		501	# do something else, then wait for process exit
		502	$done->recv;
		503
		504	=head2 IDLE WATCHERS
		505
		506	$w = AnyEvent->idle (cb => <callback>);
		507
		508	Repeatedly invoke the callback after the process becomes idle, until
		509	either the watcher is destroyed or new events have been detected.
		510
		511	Idle watchers are useful when there is a need to do something, but it
		512	is not so important (or wise) to do it instantly. The callback will be
		513	invoked only when there is "nothing better to do", which is usually
		514	defined as "all outstanding events have been handled and no new events
		515	have been detected". That means that idle watchers ideally get invoked
		516	when the event loop has just polled for new events but none have been
		517	detected. Instead of blocking to wait for more events, the idle watchers
		518	will be invoked.
		519
		520	Unfortunately, most event loops do not really support idle watchers (only
		521	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		522	will simply call the callback "from time to time".
		523
		524	Example: read lines from STDIN, but only process them when the
		525	program is otherwise idle:
		526
		527	my @lines; # read data
		528	my $idle_w;
		529	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		530	push @lines, scalar <STDIN>;
		531
		532	# start an idle watcher, if not already done
		533	$idle_w ||= AnyEvent->idle (cb => sub {
		534	# handle only one line, when there are lines left
		535	if (my $line = shift @lines) {
		536	print "handled when idle: $line";
		537	} else {
		538	# otherwise disable the idle watcher again
		539	undef $idle_w;
		540	}
		541	});
		542	});
264		543
265	=head2 CONDITION VARIABLES	544	=head2 CONDITION VARIABLES
266		545
		546	$cv = AnyEvent->condvar;
		547
		548	$cv->send (<list>);
		549	my @res = $cv->recv;
		550
		551	If you are familiar with some event loops you will know that all of them
		552	require you to run some blocking "loop", "run" or similar function that
		553	will actively watch for new events and call your callbacks.
		554
		555	AnyEvent is slightly different: it expects somebody else to run the event
		556	loop and will only block when necessary (usually when told by the user).
		557
		558	The instrument to do that is called a "condition variable", so called
		559	because they represent a condition that must become true.
		560
		561	Now is probably a good time to look at the examples further below.
		562
267	Condition variables can be created by calling the C<< AnyEvent->condvar >>	563	Condition variables can be created by calling the C<< AnyEvent->condvar
268	method without any arguments.	564	>> method, usually without arguments. The only argument pair allowed is
		565	C<cb>, which specifies a callback to be called when the condition variable
		566	becomes true, with the condition variable as the first argument (but not
		567	the results).
269		568
270	A condition variable waits for a condition - precisely that the C<<	569	After creation, the condition variable is "false" until it becomes "true"
271	->broadcast >> method has been called.	570	by calling the C<send> method (or calling the condition variable as if it
		571	were a callback, read about the caveats in the description for the C<<
		572	->send >> method).
272		573
273	They are very useful to signal that a condition has been fulfilled, for	574	Condition variables are similar to callbacks, except that you can
		575	optionally wait for them. They can also be called merge points - points
		576	in time where multiple outstanding events have been processed. And yet
		577	another way to call them is transactions - each condition variable can be
		578	used to represent a transaction, which finishes at some point and delivers
		579	a result. And yet some people know them as "futures" - a promise to
		580	compute/deliver something that you can wait for.
		581
		582	Condition variables are very useful to signal that something has finished,
274	example, if you write a module that does asynchronous http requests,	583	for example, if you write a module that does asynchronous http requests,
275	then a condition variable would be the ideal candidate to signal the	584	then a condition variable would be the ideal candidate to signal the
276	availability of results.	585	availability of results. The user can either act when the callback is
		586	called or can synchronously C<< ->recv >> for the results.
277		587
278	You can also use condition variables to block your main program until	588	You can also use them to simulate traditional event loops - for example,
279	an event occurs - for example, you could C<< ->wait >> in your main	589	you can block your main program until an event occurs - for example, you
280	program until the user clicks the Quit button in your app, which would C<<	590	could C<< ->recv >> in your main program until the user clicks the Quit
281	->broadcast >> the "quit" event.	591	button of your app, which would C<< ->send >> the "quit" event.
282		592
283	Note that condition variables recurse into the event loop - if you have	593	Note that condition variables recurse into the event loop - if you have
284	two pirces of code that call C<< ->wait >> in a round-robbin fashion, you	594	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
285	lose. Therefore, condition variables are good to export to your caller, but	595	lose. Therefore, condition variables are good to export to your caller, but
286	you should avoid making a blocking wait yourself, at least in callbacks,	596	you should avoid making a blocking wait yourself, at least in callbacks,
287	as this asks for trouble.	597	as this asks for trouble.
288		598
289	This object has two methods:	599	Condition variables are represented by hash refs in perl, and the keys
		600	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
		601	easy (it is often useful to build your own transaction class on top of
		602	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
		603	it's C<new> method in your own C<new> method.
290		604
291	=over 4	605	There are two "sides" to a condition variable - the "producer side" which
		606	eventually calls C<< -> send >>, and the "consumer side", which waits
		607	for the send to occur.
292		608
293	=item $cv->wait	609	Example: wait for a timer.
294
295	Wait (blocking if necessary) until the C<< ->broadcast >> method has been
296	called on c<$cv>, while servicing other watchers normally.
297
298	You can only wait once on a condition - additional calls will return
299	immediately.
300
301	Not all event models support a blocking wait - some die in that case
302	(programs might want to do that to stay interactive), so I<if you are
303	using this from a module, never require a blocking wait>, but let the
304	caller decide whether the call will block or not (for example, by coupling
305	condition variables with some kind of request results and supporting
306	callbacks so the caller knows that getting the result will not block,
307	while still suppporting blocking waits if the caller so desires).
308
309	Another reason I<never> to C<< ->wait >> in a module is that you cannot
310	sensibly have two C<< ->wait >>'s in parallel, as that would require
311	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
312	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and
313	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
314	from different coroutines, however).
315
316	=item $cv->broadcast
317
318	Flag the condition as ready - a running C<< ->wait >> and all further
319	calls to C<wait> will (eventually) return after this method has been
320	called. If nobody is waiting the broadcast will be remembered..
321
322	=back
323
324	Example:
325		610
326	# wait till the result is ready	611	# wait till the result is ready
327	my $result_ready = AnyEvent->condvar;	612	my $result_ready = AnyEvent->condvar;
328		613
329	# do something such as adding a timer	614	# do something such as adding a timer
330	# or socket watcher the calls $result_ready->broadcast	615	# or socket watcher the calls $result_ready->send
331	# when the "result" is ready.	616	# when the "result" is ready.
332	# in this case, we simply use a timer:	617	# in this case, we simply use a timer:
333	my $w = AnyEvent->timer (	618	my $w = AnyEvent->timer (
334	after => 1,	619	after => 1,
335	cb => sub { $result_ready->broadcast },	620	cb => sub { $result_ready->send },
336	);	621	);
337		622
338	# this "blocks" (while handling events) till the watcher	623	# this "blocks" (while handling events) till the callback
339	# calls broadcast	624	# calls ->send
340	$result_ready->wait;	625	$result_ready->recv;
		626
		627	Example: wait for a timer, but take advantage of the fact that condition
		628	variables are also callable directly.
		629
		630	my $done = AnyEvent->condvar;
		631	my $delay = AnyEvent->timer (after => 5, cb => $done);
		632	$done->recv;
		633
		634	Example: Imagine an API that returns a condvar and doesn't support
		635	callbacks. This is how you make a synchronous call, for example from
		636	the main program:
		637
		638	use AnyEvent::CouchDB;
		639
		640	...
		641
		642	my @info = $couchdb->info->recv;
		643
		644	And this is how you would just set a callback to be called whenever the
		645	results are available:
		646
		647	$couchdb->info->cb (sub {
		648	my @info = $_[0]->recv;
		649	});
		650
		651	=head3 METHODS FOR PRODUCERS
		652
		653	These methods should only be used by the producing side, i.e. the
		654	code/module that eventually sends the signal. Note that it is also
		655	the producer side which creates the condvar in most cases, but it isn't
		656	uncommon for the consumer to create it as well.
		657
		658	=over 4
		659
		660	=item $cv->send (...)
		661
		662	Flag the condition as ready - a running C<< ->recv >> and all further
		663	calls to C<recv> will (eventually) return after this method has been
		664	called. If nobody is waiting the send will be remembered.
		665
		666	If a callback has been set on the condition variable, it is called
		667	immediately from within send.
		668
		669	Any arguments passed to the C<send> call will be returned by all
		670	future C<< ->recv >> calls.
		671
		672	Condition variables are overloaded so one can call them directly (as if
		673	they were a code reference). Calling them directly is the same as calling
		674	C<send>.
		675
		676	=item $cv->croak ($error)
		677
		678	Similar to send, but causes all call's to C<< ->recv >> to invoke
		679	C<Carp::croak> with the given error message/object/scalar.
		680
		681	This can be used to signal any errors to the condition variable
		682	user/consumer. Doing it this way instead of calling C<croak> directly
		683	delays the error detetcion, but has the overwhelmign advantage that it
		684	diagnoses the error at the place where the result is expected, and not
		685	deep in some event clalback without connection to the actual code causing
		686	the problem.
		687
		688	=item $cv->begin ([group callback])
		689
		690	=item $cv->end
		691
		692	These two methods can be used to combine many transactions/events into
		693	one. For example, a function that pings many hosts in parallel might want
		694	to use a condition variable for the whole process.
		695
		696	Every call to C<< ->begin >> will increment a counter, and every call to
		697	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
		698	>>, the (last) callback passed to C<begin> will be executed, passing the
		699	condvar as first argument. That callback is I<supposed> to call C<< ->send
		700	>>, but that is not required. If no group callback was set, C<send> will
		701	be called without any arguments.
		702
		703	You can think of C<< $cv->send >> giving you an OR condition (one call
		704	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		705	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		706
		707	Let's start with a simple example: you have two I/O watchers (for example,
		708	STDOUT and STDERR for a program), and you want to wait for both streams to
		709	close before activating a condvar:
		710
		711	my $cv = AnyEvent->condvar;
		712
		713	$cv->begin; # first watcher
		714	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		715	defined sysread $fh1, my $buf, 4096
		716	or $cv->end;
		717	});
		718
		719	$cv->begin; # second watcher
		720	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		721	defined sysread $fh2, my $buf, 4096
		722	or $cv->end;
		723	});
		724
		725	$cv->recv;
		726
		727	This works because for every event source (EOF on file handle), there is
		728	one call to C<begin>, so the condvar waits for all calls to C<end> before
		729	sending.
		730
		731	The ping example mentioned above is slightly more complicated, as the
		732	there are results to be passwd back, and the number of tasks that are
		733	begung can potentially be zero:
		734
		735	my $cv = AnyEvent->condvar;
		736
		737	my %result;
		738	$cv->begin (sub { shift->send (\%result) });
		739
		740	for my $host (@list_of_hosts) {
		741	$cv->begin;
		742	ping_host_then_call_callback $host, sub {
		743	$result{$host} = ...;
		744	$cv->end;
		745	};
		746	}
		747
		748	$cv->end;
		749
		750	This code fragment supposedly pings a number of hosts and calls
		751	C<send> after results for all then have have been gathered - in any
		752	order. To achieve this, the code issues a call to C<begin> when it starts
		753	each ping request and calls C<end> when it has received some result for
		754	it. Since C<begin> and C<end> only maintain a counter, the order in which
		755	results arrive is not relevant.
		756
		757	There is an additional bracketing call to C<begin> and C<end> outside the
		758	loop, which serves two important purposes: first, it sets the callback
		759	to be called once the counter reaches C<0>, and second, it ensures that
		760	C<send> is called even when C<no> hosts are being pinged (the loop
		761	doesn't execute once).
		762
		763	This is the general pattern when you "fan out" into multiple (but
		764	potentially none) subrequests: use an outer C<begin>/C<end> pair to set
		765	the callback and ensure C<end> is called at least once, and then, for each
		766	subrequest you start, call C<begin> and for each subrequest you finish,
		767	call C<end>.
		768
		769	=back
		770
		771	=head3 METHODS FOR CONSUMERS
		772
		773	These methods should only be used by the consuming side, i.e. the
		774	code awaits the condition.
		775
		776	=over 4
		777
		778	=item $cv->recv
		779
		780	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
		781	>> methods have been called on c<$cv>, while servicing other watchers
		782	normally.
		783
		784	You can only wait once on a condition - additional calls are valid but
		785	will return immediately.
		786
		787	If an error condition has been set by calling C<< ->croak >>, then this
		788	function will call C<croak>.
		789
		790	In list context, all parameters passed to C<send> will be returned,
		791	in scalar context only the first one will be returned.
		792
		793	Note that doing a blocking wait in a callback is not supported by any
		794	event loop, that is, recursive invocation of a blocking C<< ->recv
		795	>> is not allowed, and the C<recv> call will C<croak> if such a
		796	condition is detected. This condition can be slightly loosened by using
		797	L<Coro::AnyEvent>, which allows you to do a blocking C<< ->recv >> from
		798	any thread that doesn't run the event loop itself.
		799
		800	Not all event models support a blocking wait - some die in that case
		801	(programs might want to do that to stay interactive), so I<if you are
		802	using this from a module, never require a blocking wait>. Instead, let the
		803	caller decide whether the call will block or not (for example, by coupling
		804	condition variables with some kind of request results and supporting
		805	callbacks so the caller knows that getting the result will not block,
		806	while still supporting blocking waits if the caller so desires).
		807
		808	You can ensure that C<< -recv >> never blocks by setting a callback and
		809	only calling C<< ->recv >> from within that callback (or at a later
		810	time). This will work even when the event loop does not support blocking
		811	waits otherwise.
		812
		813	=item $bool = $cv->ready
		814
		815	Returns true when the condition is "true", i.e. whether C<send> or
		816	C<croak> have been called.
		817
		818	=item $cb = $cv->cb ($cb->($cv))
		819
		820	This is a mutator function that returns the callback set and optionally
		821	replaces it before doing so.
		822
		823	The callback will be called when the condition becomes (or already was)
		824	"true", i.e. when C<send> or C<croak> are called (or were called), with
		825	the only argument being the condition variable itself. Calling C<recv>
		826	inside the callback or at any later time is guaranteed not to block.
		827
		828	=back
		829
		830	=head1 SUPPORTED EVENT LOOPS/BACKENDS
		831
		832	The available backend classes are (every class has its own manpage):
		833
		834	=over 4
		835
		836	=item Backends that are autoprobed when no other event loop can be found.
		837
		838	EV is the preferred backend when no other event loop seems to be in
		839	use. If EV is not installed, then AnyEvent will fall back to its own
		840	pure-perl implementation, which is available everywhere as it comes with
		841	AnyEvent itself.
		842
		843	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		844	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
		845
		846	=item Backends that are transparently being picked up when they are used.
		847
		848	These will be used when they are currently loaded when the first watcher
		849	is created, in which case it is assumed that the application is using
		850	them. This means that AnyEvent will automatically pick the right backend
		851	when the main program loads an event module before anything starts to
		852	create watchers. Nothing special needs to be done by the main program.
		853
		854	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		855	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		856	AnyEvent::Impl::Tk based on Tk, very broken.
		857	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		858	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		859	AnyEvent::Impl::Irssi used when running within irssi.
		860
		861	=item Backends with special needs.
		862
		863	Qt requires the Qt::Application to be instantiated first, but will
		864	otherwise be picked up automatically. As long as the main program
		865	instantiates the application before any AnyEvent watchers are created,
		866	everything should just work.
		867
		868	AnyEvent::Impl::Qt based on Qt.
		869
		870	Support for IO::Async can only be partial, as it is too broken and
		871	architecturally limited to even support the AnyEvent API. It also
		872	is the only event loop that needs the loop to be set explicitly, so
		873	it can only be used by a main program knowing about AnyEvent. See
		874	L<AnyEvent::Impl::Async> for the gory details.
		875
		876	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
		877
		878	=item Event loops that are indirectly supported via other backends.
		879
		880	Some event loops can be supported via other modules:
		881
		882	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		883
		884	B<WxWidgets> has no support for watching file handles. However, you can
		885	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		886	polls 20 times per second, which was considered to be too horrible to even
		887	consider for AnyEvent.
		888
		889	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		890	backend, so it can be supported through POE.
		891
		892	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		893	load L<POE> when detecting them, in the hope that POE will pick them up,
		894	in which case everything will be automatic.
		895
		896	=back
341		897
342	=head1 GLOBAL VARIABLES AND FUNCTIONS	898	=head1 GLOBAL VARIABLES AND FUNCTIONS
343		899
		900	These are not normally required to use AnyEvent, but can be useful to
		901	write AnyEvent extension modules.
		902
344	=over 4	903	=over 4
345		904
346	=item $AnyEvent::MODEL	905	=item $AnyEvent::MODEL
347		906
348	Contains C<undef> until the first watcher is being created. Then it	907	Contains C<undef> until the first watcher is being created, before the
		908	backend has been autodetected.
		909
349	contains the event model that is being used, which is the name of the	910	Afterwards it contains the event model that is being used, which is the
350	Perl class implementing the model. This class is usually one of the	911	name of the Perl class implementing the model. This class is usually one
351	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	912	of the C<AnyEvent::Impl:xxx> modules, but can be any other class in the
352	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	913	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
353		914	will be C<urxvt::anyevent>).
354	The known classes so far are:
355
356	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
357	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
358	AnyEvent::Impl::EV based on EV (an interface to libev, also best choice).
359	AnyEvent::Impl::Event based on Event, also second best choice :)
360	AnyEvent::Impl::Glib based on Glib, third-best choice.
361	AnyEvent::Impl::Tk based on Tk, very bad choice.
362	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
363		915
364	=item AnyEvent::detect	916	=item AnyEvent::detect
365		917
366	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	918	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
367	if necessary. You should only call this function right before you would	919	if necessary. You should only call this function right before you would
368	have created an AnyEvent watcher anyway, that is, as late as possible at	920	have created an AnyEvent watcher anyway, that is, as late as possible at
369	runtime.	921	runtime, and not e.g. while initialising of your module.
		922
		923	If you need to do some initialisation before AnyEvent watchers are
		924	created, use C<post_detect>.
		925
		926	=item $guard = AnyEvent::post_detect { BLOCK }
		927
		928	Arranges for the code block to be executed as soon as the event model is
		929	autodetected (or immediately if this has already happened).
		930
		931	The block will be executed I<after> the actual backend has been detected
		932	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		933	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		934	other initialisations - see the sources of L<AnyEvent::Strict> or
		935	L<AnyEvent::AIO> to see how this is used.
		936
		937	The most common usage is to create some global watchers, without forcing
		938	event module detection too early, for example, L<AnyEvent::AIO> creates
		939	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		940	avoid autodetecting the event module at load time.
		941
		942	If called in scalar or list context, then it creates and returns an object
		943	that automatically removes the callback again when it is destroyed (or
		944	C<undef> when the hook was immediately executed). See L<AnyEvent::AIO> for
		945	a case where this is useful.
		946
		947	Example: Create a watcher for the IO::AIO module and store it in
		948	C<$WATCHER>. Only do so after the event loop is initialised, though.
		949
		950	our WATCHER;
		951
		952	my $guard = AnyEvent::post_detect {
		953	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		954	};
		955
		956	# the ||= is important in case post_detect immediately runs the block,
		957	# as to not clobber the newly-created watcher. assigning both watcher and
		958	# post_detect guard to the same variable has the advantage of users being
		959	# able to just C<undef $WATCHER> if the watcher causes them grief.
		960
		961	$WATCHER ||= $guard;
		962
		963	=item @AnyEvent::post_detect
		964
		965	If there are any code references in this array (you can C<push> to it
		966	before or after loading AnyEvent), then they will called directly after
		967	the event loop has been chosen.
		968
		969	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		970	if it is defined then the event loop has already been detected, and the
		971	array will be ignored.
		972
		973	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		974	it, as it takes care of these details.
		975
		976	This variable is mainly useful for modules that can do something useful
		977	when AnyEvent is used and thus want to know when it is initialised, but do
		978	not need to even load it by default. This array provides the means to hook
		979	into AnyEvent passively, without loading it.
		980
		981	Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used
		982	together, you could put this into Coro (this is the actual code used by
		983	Coro to accomplish this):
		984
		985	if (defined $AnyEvent::MODEL) {
		986	# AnyEvent already initialised, so load Coro::AnyEvent
		987	require Coro::AnyEvent;
		988	} else {
		989	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent
		990	# as soon as it is
		991	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };
		992	}
370		993
371	=back	994	=back
372		995
373	=head1 WHAT TO DO IN A MODULE	996	=head1 WHAT TO DO IN A MODULE
374		997
…		…
378	Be careful when you create watchers in the module body - AnyEvent will	1001	Be careful when you create watchers in the module body - AnyEvent will
379	decide which event module to use as soon as the first method is called, so	1002	decide which event module to use as soon as the first method is called, so
380	by calling AnyEvent in your module body you force the user of your module	1003	by calling AnyEvent in your module body you force the user of your module
381	to load the event module first.	1004	to load the event module first.
382		1005
383	Never call C<< ->wait >> on a condition variable unless you I<know> that	1006	Never call C<< ->recv >> on a condition variable unless you I<know> that
384	the C<< ->broadcast >> method has been called on it already. This is	1007	the C<< ->send >> method has been called on it already. This is
385	because it will stall the whole program, and the whole point of using	1008	because it will stall the whole program, and the whole point of using
386	events is to stay interactive.	1009	events is to stay interactive.
387		1010
388	It is fine, however, to call C<< ->wait >> when the user of your module	1011	It is fine, however, to call C<< ->recv >> when the user of your module
389	requests it (i.e. if you create a http request object ad have a method	1012	requests it (i.e. if you create a http request object ad have a method
390	called C<results> that returns the results, it should call C<< ->wait >>	1013	called C<results> that returns the results, it should call C<< ->recv >>
391	freely, as the user of your module knows what she is doing. always).	1014	freely, as the user of your module knows what she is doing. always).
392		1015
393	=head1 WHAT TO DO IN THE MAIN PROGRAM	1016	=head1 WHAT TO DO IN THE MAIN PROGRAM
394		1017
395	There will always be a single main program - the only place that should	1018	There will always be a single main program - the only place that should
…		…
397		1020
398	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	1021	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
399	do anything special (it does not need to be event-based) and let AnyEvent	1022	do anything special (it does not need to be event-based) and let AnyEvent
400	decide which implementation to chose if some module relies on it.	1023	decide which implementation to chose if some module relies on it.
401		1024
402	If the main program relies on a specific event model. For example, in	1025	If the main program relies on a specific event model - for example, in
403	Gtk2 programs you have to rely on the Glib module. You should load the	1026	Gtk2 programs you have to rely on the Glib module - you should load the
404	event module before loading AnyEvent or any module that uses it: generally	1027	event module before loading AnyEvent or any module that uses it: generally
405	speaking, you should load it as early as possible. The reason is that	1028	speaking, you should load it as early as possible. The reason is that
406	modules might create watchers when they are loaded, and AnyEvent will	1029	modules might create watchers when they are loaded, and AnyEvent will
407	decide on the event model to use as soon as it creates watchers, and it	1030	decide on the event model to use as soon as it creates watchers, and it
408	might chose the wrong one unless you load the correct one yourself.	1031	might chose the wrong one unless you load the correct one yourself.
409		1032
410	You can chose to use a rather inefficient pure-perl implementation by	1033	You can chose to use a pure-perl implementation by loading the
411	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	1034	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
412	behaviour everywhere, but letting AnyEvent chose is generally better.	1035	everywhere, but letting AnyEvent chose the model is generally better.
		1036
		1037	=head2 MAINLOOP EMULATION
		1038
		1039	Sometimes (often for short test scripts, or even standalone programs who
		1040	only want to use AnyEvent), you do not want to run a specific event loop.
		1041
		1042	In that case, you can use a condition variable like this:
		1043
		1044	AnyEvent->condvar->recv;
		1045
		1046	This has the effect of entering the event loop and looping forever.
		1047
		1048	Note that usually your program has some exit condition, in which case
		1049	it is better to use the "traditional" approach of storing a condition
		1050	variable somewhere, waiting for it, and sending it when the program should
		1051	exit cleanly.
		1052
		1053
		1054	=head1 OTHER MODULES
		1055
		1056	The following is a non-exhaustive list of additional modules that use
		1057	AnyEvent as a client and can therefore be mixed easily with other AnyEvent
		1058	modules and other event loops in the same program. Some of the modules
		1059	come with AnyEvent, most are available via CPAN.
		1060
		1061	=over 4
		1062
		1063	=item L<AnyEvent::Util>
		1064
		1065	Contains various utility functions that replace often-used but blocking
		1066	functions such as C<inet_aton> by event-/callback-based versions.
		1067
		1068	=item L<AnyEvent::Socket>
		1069
		1070	Provides various utility functions for (internet protocol) sockets,
		1071	addresses and name resolution. Also functions to create non-blocking tcp
		1072	connections or tcp servers, with IPv6 and SRV record support and more.
		1073
		1074	=item L<AnyEvent::Handle>
		1075
		1076	Provide read and write buffers, manages watchers for reads and writes,
		1077	supports raw and formatted I/O, I/O queued and fully transparent and
		1078	non-blocking SSL/TLS (via L<AnyEvent::TLS>.
		1079
		1080	=item L<AnyEvent::DNS>
		1081
		1082	Provides rich asynchronous DNS resolver capabilities.
		1083
		1084	=item L<AnyEvent::HTTP>
		1085
		1086	A simple-to-use HTTP library that is capable of making a lot of concurrent
		1087	HTTP requests.
		1088
		1089	=item L<AnyEvent::HTTPD>
		1090
		1091	Provides a simple web application server framework.
		1092
		1093	=item L<AnyEvent::FastPing>
		1094
		1095	The fastest ping in the west.
		1096
		1097	=item L<AnyEvent::DBI>
		1098
		1099	Executes L<DBI> requests asynchronously in a proxy process.
		1100
		1101	=item L<AnyEvent::AIO>
		1102
		1103	Truly asynchronous I/O, should be in the toolbox of every event
		1104	programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
		1105	together.
		1106
		1107	=item L<AnyEvent::BDB>
		1108
		1109	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
		1110	L<BDB> and AnyEvent together.
		1111
		1112	=item L<AnyEvent::GPSD>
		1113
		1114	A non-blocking interface to gpsd, a daemon delivering GPS information.
		1115
		1116	=item L<AnyEvent::IRC>
		1117
		1118	AnyEvent based IRC client module family (replacing the older Net::IRC3).
		1119
		1120	=item L<AnyEvent::XMPP>
		1121
		1122	AnyEvent based XMPP (Jabber protocol) module family (replacing the older
		1123	Net::XMPP2>.
		1124
		1125	=item L<AnyEvent::IGS>
		1126
		1127	A non-blocking interface to the Internet Go Server protocol (used by
		1128	L<App::IGS>).
		1129
		1130	=item L<Net::FCP>
		1131
		1132	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
		1133	of AnyEvent.
		1134
		1135	=item L<Event::ExecFlow>
		1136
		1137	High level API for event-based execution flow control.
		1138
		1139	=item L<Coro>
		1140
		1141	Has special support for AnyEvent via L<Coro::AnyEvent>.
		1142
		1143	=back
413		1144
414	=cut	1145	=cut
415		1146
416	package AnyEvent;	1147	package AnyEvent;
417		1148
418	no warnings;	1149	# basically a tuned-down version of common::sense
419	use strict;	1150	sub common_sense {
		1151	# from common:.sense 1.0
		1152	${^WARNING_BITS} = "\xfc\x3f\x33\x00\x0f\xf3\xcf\xc0\xf3\xfc\x33\x00";
		1153	# use strict vars subs - NO UTF-8, as Util.pm doesn't like this atm. (uts46data.pl)
		1154	$^H |= 0x00000600;
		1155	}
420		1156
		1157	BEGIN { AnyEvent::common_sense }
		1158
421	use Carp;	1159	use Carp ();
422		1160
423	our $VERSION = '3.11';	1161	our $VERSION = '5.251';
424	our $MODEL;	1162	our $MODEL;
425		1163
426	our $AUTOLOAD;	1164	our $AUTOLOAD;
427	our @ISA;	1165	our @ISA;
428		1166
429	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
430
431	our @REGISTRY;	1167	our @REGISTRY;
432		1168
		1169	our $VERBOSE;
		1170
		1171	BEGIN {
		1172	require "AnyEvent/constants.pl";
		1173
		1174	eval "sub TAINT (){" . (${^TAINT}*1) . "}";
		1175
		1176	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1177	if ${^TAINT};
		1178
		1179	$VERBOSE = $ENV{PERL_ANYEVENT_VERBOSE}*1;
		1180
		1181	}
		1182
		1183	our $MAX_SIGNAL_LATENCY = 10;
		1184
		1185	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		1186
		1187	{
		1188	my $idx;
		1189	$PROTOCOL{$_} = ++$idx
		1190	for reverse split /\s*,\s*/,
		1191	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		1192	}
		1193
433	my @models = (	1194	my @models = (
434	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
435	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
436	[EV:: => AnyEvent::Impl::EV::],	1195	[EV:: => AnyEvent::Impl::EV:: , 1],
		1196	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl:: , 1],
		1197	# everything below here will not (normally) be autoprobed
		1198	# as the pureperl backend should work everywhere
		1199	# and is usually faster
437	[Event:: => AnyEvent::Impl::Event::],	1200	[Event:: => AnyEvent::Impl::Event::, 1],
438	[Glib:: => AnyEvent::Impl::Glib::],	1201	[Glib:: => AnyEvent::Impl::Glib:: , 1], # becomes extremely slow with many watchers
		1202	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		1203	[Irssi:: => AnyEvent::Impl::Irssi::], # Irssi has a bogus "Event" package
		1204	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		1205	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		1206	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
439	[Tk:: => AnyEvent::Impl::Tk::],	1207	[Wx:: => AnyEvent::Impl::POE::],
440	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1208	[Prima:: => AnyEvent::Impl::POE::],
		1209	# IO::Async is just too broken - we would need workarounds for its
		1210	# byzantine signal and broken child handling, among others.
		1211	# IO::Async is rather hard to detect, as it doesn't have any
		1212	# obvious default class.
		1213	[IO::Async:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1214	[IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1215	[IO::Async::Notifier:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1216	[AnyEvent::Impl::IOAsync:: => AnyEvent::Impl::IOAsync::], # requires special main program
441	);	1217	);
442		1218
443	our %method = map +($_ => 1), qw(io timer condvar broadcast wait signal one_event DESTROY);	1219	our %method = map +($_ => 1),
		1220	qw(io timer time now now_update signal child idle condvar one_event DESTROY);
		1221
		1222	our @post_detect;
		1223
		1224	sub post_detect(&) {
		1225	my ($cb) = @_;
		1226
		1227	push @post_detect, $cb;
		1228
		1229	defined wantarray
		1230	? bless \$cb, "AnyEvent::Util::postdetect"
		1231	: ()
		1232	}
		1233
		1234	sub AnyEvent::Util::postdetect::DESTROY {
		1235	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		1236	}
444		1237
445	sub detect() {	1238	sub detect() {
		1239	# free some memory
		1240	*detect = sub () { $MODEL };
		1241
		1242	local $!; # for good measure
		1243	local $SIG{__DIE__};
		1244
		1245	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
		1246	my $model = "AnyEvent::Impl::$1";
		1247	if (eval "require $model") {
		1248	$MODEL = $model;
		1249	warn "AnyEvent: loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.\n" if $VERBOSE >= 2;
		1250	} else {
		1251	warn "AnyEvent: unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@" if $VERBOSE;
		1252	}
		1253	}
		1254
		1255	# check for already loaded models
446	unless ($MODEL) {	1256	unless ($MODEL) {
447	no strict 'refs';
448
449	# check for already loaded models
450	for (@REGISTRY, @models) {	1257	for (@REGISTRY, @models) {
451	my ($package, $model) = @$_;	1258	my ($package, $model) = @$_;
452	if (${"$package\::VERSION"} > 0) {	1259	if (${"$package\::VERSION"} > 0) {
453	if (eval "require $model") {	1260	if (eval "require $model") {
454	$MODEL = $model;	1261	$MODEL = $model;
455	warn "AnyEvent: found model '$model', using it.\n" if $verbose > 1;	1262	warn "AnyEvent: autodetected model '$model', using it.\n" if $VERBOSE >= 2;
456	last;	1263	last;
457	}	1264	}
458	}	1265	}
459	}	1266	}
460		1267
461	unless ($MODEL) {	1268	unless ($MODEL) {
462	# try to load a model	1269	# try to autoload a model
463
464	for (@REGISTRY, @models) {	1270	for (@REGISTRY, @models) {
465	my ($package, $model) = @$_;	1271	my ($package, $model, $autoload) = @$_;
		1272	if (
		1273	$autoload
466	if (eval "require $package"	1274	and eval "require $package"
467	and ${"$package\::VERSION"} > 0	1275	and ${"$package\::VERSION"} > 0
468	and eval "require $model") {	1276	and eval "require $model"
		1277	) {
469	$MODEL = $model;	1278	$MODEL = $model;
470	warn "AnyEvent: autoprobed and loaded model '$model', using it.\n" if $verbose > 1;	1279	warn "AnyEvent: autoloaded model '$model', using it.\n" if $VERBOSE >= 2;
471	last;	1280	last;
472	}	1281	}
473	}	1282	}
474		1283
475	$MODEL	1284	$MODEL
476	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), Glib or Tk.";	1285	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.\n";
477	}	1286	}
478
479	unshift @ISA, $MODEL;
480	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
481	}	1287	}
		1288
		1289	@models = (); # free probe data
		1290
		1291	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		1292	unshift @ISA, $MODEL;
		1293
		1294	# now nuke some methods that are overriden by the backend.
		1295	# SUPER is not allowed.
		1296	for (qw(time signal child idle)) {
		1297	undef &{"AnyEvent::Base::$_"}
		1298	if defined &{"$MODEL\::$_"};
		1299	}
		1300
		1301	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
		1302
		1303	(shift @post_detect)->() while @post_detect;
		1304
		1305	*post_detect = sub(&) {
		1306	shift->();
		1307
		1308	undef
		1309	};
482		1310
483	$MODEL	1311	$MODEL
484	}	1312	}
485		1313
486	sub AUTOLOAD {	1314	sub AUTOLOAD {
487	(my $func = $AUTOLOAD) =~ s/.*://;	1315	(my $func = $AUTOLOAD) =~ s/.*://;
488		1316
489	$method{$func}	1317	$method{$func}
490	or croak "$func: not a valid method for AnyEvent objects";	1318	or Carp::croak "$func: not a valid AnyEvent class method";
491		1319
492	detect unless $MODEL;	1320	detect;
493		1321
494	my $class = shift;	1322	my $class = shift;
495	$class->$func (@_);	1323	$class->$func (@_);
496	}	1324	}
497		1325
		1326	# utility function to dup a filehandle. this is used by many backends
		1327	# to support binding more than one watcher per filehandle (they usually
		1328	# allow only one watcher per fd, so we dup it to get a different one).
		1329	sub _dupfh($$;$$) {
		1330	my ($poll, $fh, $r, $w) = @_;
		1331
		1332	# cygwin requires the fh mode to be matching, unix doesn't
		1333	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1334
		1335	open my $fh2, $mode, $fh
		1336	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1337
		1338	# we assume CLOEXEC is already set by perl in all important cases
		1339
		1340	($fh2, $rw)
		1341	}
		1342
		1343	=head1 SIMPLIFIED AE API
		1344
		1345	Starting with version 5.0, AnyEvent officially supports a second, much
		1346	simpler, API that is designed to reduce the calling, typing and memory
		1347	overhead.
		1348
		1349	See the L<AE> manpage for details.
		1350
		1351	=cut
		1352
		1353	package AE;
		1354
		1355	our $VERSION = $AnyEvent::VERSION;
		1356
		1357	sub io($$$) {
		1358	AnyEvent->io (fh => $_[0], poll => $_[1] ? "w" : "r", cb => $_[2])
		1359	}
		1360
		1361	sub timer($$$) {
		1362	AnyEvent->timer (after => $_[0], interval => $_[1], cb => $_[2])
		1363	}
		1364
		1365	sub signal($$) {
		1366	AnyEvent->signal (signal => $_[0], cb => $_[1])
		1367	}
		1368
		1369	sub child($$) {
		1370	AnyEvent->child (pid => $_[0], cb => $_[1])
		1371	}
		1372
		1373	sub idle($) {
		1374	AnyEvent->idle (cb => $_[0])
		1375	}
		1376
		1377	sub cv(;&) {
		1378	AnyEvent->condvar (@_ ? (cb => $_[0]) : ())
		1379	}
		1380
		1381	sub now() {
		1382	AnyEvent->now
		1383	}
		1384
		1385	sub now_update() {
		1386	AnyEvent->now_update
		1387	}
		1388
		1389	sub time() {
		1390	AnyEvent->time
		1391	}
		1392
498	package AnyEvent::Base;	1393	package AnyEvent::Base;
499		1394
		1395	# default implementations for many methods
		1396
		1397	sub time {
		1398	eval q{ # poor man's autoloading {}
		1399	# probe for availability of Time::HiRes
		1400	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1401	warn "AnyEvent: using Time::HiRes for sub-second timing accuracy.\n" if $VERBOSE >= 8;
		1402	*AE::time = \&Time::HiRes::time;
		1403	# if (eval "use POSIX (); (POSIX::times())...
		1404	} else {
		1405	warn "AnyEvent: using built-in time(), WARNING, no sub-second resolution!\n" if $VERBOSE;
		1406	*AE::time = sub (){ time }; # epic fail
		1407	}
		1408
		1409	*time = sub { AE::time }; # different prototypes
		1410	};
		1411	die if $@;
		1412
		1413	&time
		1414	}
		1415
		1416	*now = \&time;
		1417
		1418	sub now_update { }
		1419
500	# default implementation for ->condvar, ->wait, ->broadcast	1420	# default implementation for ->condvar
501		1421
502	sub condvar {	1422	sub condvar {
503	bless \my $flag, "AnyEvent::Base::CondVar"	1423	eval q{ # poor man's autoloading {}
504	}	1424	*condvar = sub {
		1425	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
		1426	};
505		1427
506	sub AnyEvent::Base::CondVar::broadcast {	1428	*AE::cv = sub (;&) {
507	${$_[0]}++;	1429	bless { @_ ? (_ae_cb => shift) : () }, "AnyEvent::CondVar"
508	}	1430	};
		1431	};
		1432	die if $@;
509		1433
510	sub AnyEvent::Base::CondVar::wait {	1434	&condvar
511	AnyEvent->one_event while !${$_[0]};
512	}	1435	}
513		1436
514	# default implementation for ->signal	1437	# default implementation for ->signal
515		1438
516	our %SIG_CB;	1439	our $HAVE_ASYNC_INTERRUPT;
		1440
		1441	sub _have_async_interrupt() {
		1442	$HAVE_ASYNC_INTERRUPT = 1*(!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT}
		1443	&& eval "use Async::Interrupt 1.02 (); 1")
		1444	unless defined $HAVE_ASYNC_INTERRUPT;
		1445
		1446	$HAVE_ASYNC_INTERRUPT
		1447	}
		1448
		1449	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1450	our (%SIG_ASY, %SIG_ASY_W);
		1451	our ($SIG_COUNT, $SIG_TW);
		1452
		1453	# install a dummy wakeup watcher to reduce signal catching latency
		1454	# used by Impls
		1455	sub _sig_add() {
		1456	unless ($SIG_COUNT++) {
		1457	# try to align timer on a full-second boundary, if possible
		1458	my $NOW = AE::now;
		1459
		1460	$SIG_TW = AE::timer
		1461	$MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1462	$MAX_SIGNAL_LATENCY,
		1463	sub { } # just for the PERL_ASYNC_CHECK
		1464	;
		1465	}
		1466	}
		1467
		1468	sub _sig_del {
		1469	undef $SIG_TW
		1470	unless --$SIG_COUNT;
		1471	}
		1472
		1473	our $_sig_name_init; $_sig_name_init = sub {
		1474	eval q{ # poor man's autoloading {}
		1475	undef $_sig_name_init;
		1476
		1477	if (_have_async_interrupt) {
		1478	*sig2num = \&Async::Interrupt::sig2num;
		1479	*sig2name = \&Async::Interrupt::sig2name;
		1480	} else {
		1481	require Config;
		1482
		1483	my %signame2num;
		1484	@signame2num{ split ' ', $Config::Config{sig_name} }
		1485	= split ' ', $Config::Config{sig_num};
		1486
		1487	my @signum2name;
		1488	@signum2name[values %signame2num] = keys %signame2num;
		1489
		1490	*sig2num = sub($) {
		1491	$_[0] > 0 ? shift : $signame2num{+shift}
		1492	};
		1493	*sig2name = sub ($) {
		1494	$_[0] > 0 ? $signum2name[+shift] : shift
		1495	};
		1496	}
		1497	};
		1498	die if $@;
		1499	};
		1500
		1501	sub sig2num ($) { &$_sig_name_init; &sig2num }
		1502	sub sig2name($) { &$_sig_name_init; &sig2name }
517		1503
518	sub signal {	1504	sub signal {
		1505	eval q{ # poor man's autoloading {}
		1506	# probe for availability of Async::Interrupt
		1507	if (_have_async_interrupt) {
		1508	warn "AnyEvent: using Async::Interrupt for race-free signal handling.\n" if $VERBOSE >= 8;
		1509
		1510	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1511	$SIG_IO = AE::io $SIGPIPE_R->fileno, 0, \&_signal_exec;
		1512
		1513	} else {
		1514	warn "AnyEvent: using emulated perl signal handling with latency timer.\n" if $VERBOSE >= 8;
		1515
		1516	if (AnyEvent::WIN32) {
		1517	require AnyEvent::Util;
		1518
		1519	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1520	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R, 1) if $SIGPIPE_R;
		1521	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W, 1) if $SIGPIPE_W; # just in case
		1522	} else {
		1523	pipe $SIGPIPE_R, $SIGPIPE_W;
		1524	fcntl $SIGPIPE_R, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_R;
		1525	fcntl $SIGPIPE_W, AnyEvent::F_SETFL, AnyEvent::O_NONBLOCK if $SIGPIPE_W; # just in case
		1526
		1527	# not strictly required, as $^F is normally 2, but let's make sure...
		1528	fcntl $SIGPIPE_R, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1529	fcntl $SIGPIPE_W, AnyEvent::F_SETFD, AnyEvent::FD_CLOEXEC;
		1530	}
		1531
		1532	$SIGPIPE_R
		1533	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1534
		1535	$SIG_IO = AE::io $SIGPIPE_R, 0, \&_signal_exec;
		1536	}
		1537
		1538	*signal = $HAVE_ASYNC_INTERRUPT
		1539	? sub {
519	my (undef, %arg) = @_;	1540	my (undef, %arg) = @_;
520		1541
		1542	# async::interrupt
521	my $signal = uc $arg{signal}	1543	my $signal = sig2num $arg{signal};
522	or Carp::croak "required option 'signal' is missing";
523
524	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1544	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1545
		1546	$SIG_ASY{$signal} ||= new Async::Interrupt
		1547	cb => sub { undef $SIG_EV{$signal} },
		1548	signal => $signal,
		1549	pipe => [$SIGPIPE_R->filenos],
		1550	pipe_autodrain => 0,
		1551	;
		1552
		1553	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1554	}
		1555	: sub {
		1556	my (undef, %arg) = @_;
		1557
		1558	# pure perl
		1559	my $signal = sig2name $arg{signal};
		1560	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1561
525	$SIG{$signal} ||= sub {	1562	$SIG{$signal} ||= sub {
		1563	local $!;
		1564	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1565	undef $SIG_EV{$signal};
		1566	};
		1567
		1568	# can't do signal processing without introducing races in pure perl,
		1569	# so limit the signal latency.
		1570	_sig_add;
		1571
		1572	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1573	}
		1574	;
		1575
		1576	*AnyEvent::Base::signal::DESTROY = sub {
		1577	my ($signal, $cb) = @{$_[0]};
		1578
		1579	_sig_del;
		1580
		1581	delete $SIG_CB{$signal}{$cb};
		1582
		1583	$HAVE_ASYNC_INTERRUPT
		1584	? delete $SIG_ASY{$signal}
		1585	: # delete doesn't work with older perls - they then
		1586	# print weird messages, or just unconditionally exit
		1587	# instead of getting the default action.
		1588	undef $SIG{$signal}
		1589	unless keys %{ $SIG_CB{$signal} };
		1590	};
		1591
		1592	*_signal_exec = sub {
		1593	$HAVE_ASYNC_INTERRUPT
		1594	? $SIGPIPE_R->drain
		1595	: sysread $SIGPIPE_R, (my $dummy), 9;
		1596
		1597	while (%SIG_EV) {
		1598	for (keys %SIG_EV) {
		1599	delete $SIG_EV{$_};
526	$_->() for values %{ $SIG_CB{$signal} || {} };	1600	$_->() for values %{ $SIG_CB{$_} || {} };
		1601	}
		1602	}
		1603	};
527	};	1604	};
		1605	die if $@;
528		1606
529	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1607	&signal
530	}
531
532	sub AnyEvent::Base::Signal::DESTROY {
533	my ($signal, $cb) = @{$_[0]};
534
535	delete $SIG_CB{$signal}{$cb};
536
537	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };
538	}	1608	}
539		1609
540	# default implementation for ->child	1610	# default implementation for ->child
541		1611
542	our %PID_CB;	1612	our %PID_CB;
543	our $CHLD_W;	1613	our $CHLD_W;
544	our $CHLD_DELAY_W;	1614	our $CHLD_DELAY_W;
545	our $PID_IDLE;
546	our $WNOHANG;	1615	our $WNOHANG;
547		1616
548	sub _child_wait {	1617	# used by many Impl's
549	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1618	sub _emit_childstatus($$) {
		1619	my (undef, $rpid, $rstatus) = @_;
		1620
		1621	$_->($rpid, $rstatus)
550	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1622	for values %{ $PID_CB{$rpid} || {} },
551	(values %{ $PID_CB{0} || {} });	1623	values %{ $PID_CB{0} || {} };
552	}
553
554	undef $PID_IDLE;
555	}
556
557	sub _sigchld {
558	# make sure we deliver these changes "synchronous" with the event loop.
559	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {
560	undef $CHLD_DELAY_W;
561	&_child_wait;
562	});
563	}	1624	}
564		1625
565	sub child {	1626	sub child {
		1627	eval q{ # poor man's autoloading {}
		1628	*_sigchld = sub {
		1629	my $pid;
		1630
		1631	AnyEvent->_emit_childstatus ($pid, $?)
		1632	while ($pid = waitpid -1, $WNOHANG) > 0;
		1633	};
		1634
		1635	*child = sub {
566	my (undef, %arg) = @_;	1636	my (undef, %arg) = @_;
567		1637
568	defined (my $pid = $arg{pid} + 0)	1638	defined (my $pid = $arg{pid} + 0)
569	or Carp::croak "required option 'pid' is missing";	1639	or Carp::croak "required option 'pid' is missing";
570		1640
571	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1641	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
572		1642
573	unless ($WNOHANG) {	1643	# WNOHANG is almost cetrainly 1 everywhere
574	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;	1644	$WNOHANG ||= $^O =~ /^(?:openbsd|netbsd|linux|freebsd|cygwin|MSWin32)$/
575	}	1645	? 1
		1646	: eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
576		1647
577	unless ($CHLD_W) {	1648	unless ($CHLD_W) {
578	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1649	$CHLD_W = AE::signal CHLD => \&_sigchld;
579	# child could be a zombie already, so make at least one round	1650	# child could be a zombie already, so make at least one round
580	&_sigchld;	1651	&_sigchld;
581	}	1652	}
582		1653
583	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	1654	bless [$pid, $arg{cb}], "AnyEvent::Base::child"
584	}	1655	};
585		1656
586	sub AnyEvent::Base::Child::DESTROY {	1657	*AnyEvent::Base::child::DESTROY = sub {
587	my ($pid, $cb) = @{$_[0]};	1658	my ($pid, $cb) = @{$_[0]};
588		1659
589	delete $PID_CB{$pid}{$cb};	1660	delete $PID_CB{$pid}{$cb};
590	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1661	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
591		1662
592	undef $CHLD_W unless keys %PID_CB;	1663	undef $CHLD_W unless keys %PID_CB;
		1664	};
		1665	};
		1666	die if $@;
		1667
		1668	&child
593	}	1669	}
		1670
		1671	# idle emulation is done by simply using a timer, regardless
		1672	# of whether the process is idle or not, and not letting
		1673	# the callback use more than 50% of the time.
		1674	sub idle {
		1675	eval q{ # poor man's autoloading {}
		1676	*idle = sub {
		1677	my (undef, %arg) = @_;
		1678
		1679	my ($cb, $w, $rcb) = $arg{cb};
		1680
		1681	$rcb = sub {
		1682	if ($cb) {
		1683	$w = _time;
		1684	&$cb;
		1685	$w = _time - $w;
		1686
		1687	# never use more then 50% of the time for the idle watcher,
		1688	# within some limits
		1689	$w = 0.0001 if $w < 0.0001;
		1690	$w = 5 if $w > 5;
		1691
		1692	$w = AE::timer $w, 0, $rcb;
		1693	} else {
		1694	# clean up...
		1695	undef $w;
		1696	undef $rcb;
		1697	}
		1698	};
		1699
		1700	$w = AE::timer 0.05, 0, $rcb;
		1701
		1702	bless \\$cb, "AnyEvent::Base::idle"
		1703	};
		1704
		1705	*AnyEvent::Base::idle::DESTROY = sub {
		1706	undef $${$_[0]};
		1707	};
		1708	};
		1709	die if $@;
		1710
		1711	&idle
		1712	}
		1713
		1714	package AnyEvent::CondVar;
		1715
		1716	our @ISA = AnyEvent::CondVar::Base::;
		1717
		1718	package AnyEvent::CondVar::Base;
		1719
		1720	#use overload
		1721	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1722	# fallback => 1;
		1723
		1724	# save 300+ kilobytes by dirtily hardcoding overloading
		1725	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1726	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1727	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1728	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1729
		1730	our $WAITING;
		1731
		1732	sub _send {
		1733	# nop
		1734	}
		1735
		1736	sub send {
		1737	my $cv = shift;
		1738	$cv->{_ae_sent} = [@_];
		1739	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1740	$cv->_send;
		1741	}
		1742
		1743	sub croak {
		1744	$_[0]{_ae_croak} = $_[1];
		1745	$_[0]->send;
		1746	}
		1747
		1748	sub ready {
		1749	$_[0]{_ae_sent}
		1750	}
		1751
		1752	sub _wait {
		1753	$WAITING
		1754	and !$_[0]{_ae_sent}
		1755	and Carp::croak "AnyEvent::CondVar: recursive blocking wait detected";
		1756
		1757	local $WAITING = 1;
		1758	AnyEvent->one_event while !$_[0]{_ae_sent};
		1759	}
		1760
		1761	sub recv {
		1762	$_[0]->_wait;
		1763
		1764	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
		1765	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
		1766	}
		1767
		1768	sub cb {
		1769	my $cv = shift;
		1770
		1771	@_
		1772	and $cv->{_ae_cb} = shift
		1773	and $cv->{_ae_sent}
		1774	and (delete $cv->{_ae_cb})->($cv);
		1775
		1776	$cv->{_ae_cb}
		1777	}
		1778
		1779	sub begin {
		1780	++$_[0]{_ae_counter};
		1781	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
		1782	}
		1783
		1784	sub end {
		1785	return if --$_[0]{_ae_counter};
		1786	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		1787	}
		1788
		1789	# undocumented/compatibility with pre-3.4
		1790	*broadcast = \&send;
		1791	*wait = \&_wait;
		1792
		1793	=head1 ERROR AND EXCEPTION HANDLING
		1794
		1795	In general, AnyEvent does not do any error handling - it relies on the
		1796	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1797	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1798	checking of all AnyEvent methods, however, which is highly useful during
		1799	development.
		1800
		1801	As for exception handling (i.e. runtime errors and exceptions thrown while
		1802	executing a callback), this is not only highly event-loop specific, but
		1803	also not in any way wrapped by this module, as this is the job of the main
		1804	program.
		1805
		1806	The pure perl event loop simply re-throws the exception (usually
		1807	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1808	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1809	so on.
		1810
		1811	=head1 ENVIRONMENT VARIABLES
		1812
		1813	The following environment variables are used by this module or its
		1814	submodules.
		1815
		1816	Note that AnyEvent will remove I<all> environment variables starting with
		1817	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		1818	enabled.
		1819
		1820	=over 4
		1821
		1822	=item C<PERL_ANYEVENT_VERBOSE>
		1823
		1824	By default, AnyEvent will be completely silent except in fatal
		1825	conditions. You can set this environment variable to make AnyEvent more
		1826	talkative.
		1827
		1828	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1829	conditions, such as not being able to load the event model specified by
		1830	C<PERL_ANYEVENT_MODEL>.
		1831
		1832	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1833	model it chooses.
		1834
		1835	When set to C<8> or higher, then AnyEvent will report extra information on
		1836	which optional modules it loads and how it implements certain features.
		1837
		1838	=item C<PERL_ANYEVENT_STRICT>
		1839
		1840	AnyEvent does not do much argument checking by default, as thorough
		1841	argument checking is very costly. Setting this variable to a true value
		1842	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1843	check the arguments passed to most method calls. If it finds any problems,
		1844	it will croak.
		1845
		1846	In other words, enables "strict" mode.
		1847
		1848	Unlike C<use strict> (or it's modern cousin, C<< use L<common::sense>
		1849	>>, it is definitely recommended to keep it off in production. Keeping
		1850	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		1851	can be very useful, however.
		1852
		1853	=item C<PERL_ANYEVENT_MODEL>
		1854
		1855	This can be used to specify the event model to be used by AnyEvent, before
		1856	auto detection and -probing kicks in. It must be a string consisting
		1857	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1858	and the resulting module name is loaded and if the load was successful,
		1859	used as event model. If it fails to load AnyEvent will proceed with
		1860	auto detection and -probing.
		1861
		1862	This functionality might change in future versions.
		1863
		1864	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1865	could start your program like this:
		1866
		1867	PERL_ANYEVENT_MODEL=Perl perl ...
		1868
		1869	=item C<PERL_ANYEVENT_PROTOCOLS>
		1870
		1871	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1872	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1873	of auto probing).
		1874
		1875	Must be set to a comma-separated list of protocols or address families,
		1876	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1877	used, and preference will be given to protocols mentioned earlier in the
		1878	list.
		1879
		1880	This variable can effectively be used for denial-of-service attacks
		1881	against local programs (e.g. when setuid), although the impact is likely
		1882	small, as the program has to handle conenction and other failures anyways.
		1883
		1884	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1885	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1886	- only support IPv4, never try to resolve or contact IPv6
		1887	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1888	IPv6, but prefer IPv6 over IPv4.
		1889
		1890	=item C<PERL_ANYEVENT_EDNS0>
		1891
		1892	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1893	for DNS. This extension is generally useful to reduce DNS traffic, but
		1894	some (broken) firewalls drop such DNS packets, which is why it is off by
		1895	default.
		1896
		1897	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1898	EDNS0 in its DNS requests.
		1899
		1900	=item C<PERL_ANYEVENT_MAX_FORKS>
		1901
		1902	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1903	will create in parallel.
		1904
		1905	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		1906
		1907	The default value for the C<max_outstanding> parameter for the default DNS
		1908	resolver - this is the maximum number of parallel DNS requests that are
		1909	sent to the DNS server.
		1910
		1911	=item C<PERL_ANYEVENT_RESOLV_CONF>
		1912
		1913	The file to use instead of F</etc/resolv.conf> (or OS-specific
		1914	configuration) in the default resolver. When set to the empty string, no
		1915	default config will be used.
		1916
		1917	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		1918
		1919	When neither C<ca_file> nor C<ca_path> was specified during
		1920	L<AnyEvent::TLS> context creation, and either of these environment
		1921	variables exist, they will be used to specify CA certificate locations
		1922	instead of a system-dependent default.
		1923
		1924	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		1925
		1926	When these are set to C<1>, then the respective modules are not
		1927	loaded. Mostly good for testing AnyEvent itself.
		1928
		1929	=back
594		1930
595	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1931	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
596		1932
597	This is an advanced topic that you do not normally need to use AnyEvent in	1933	This is an advanced topic that you do not normally need to use AnyEvent in
598	a module. This section is only of use to event loop authors who want to	1934	a module. This section is only of use to event loop authors who want to
…		…
633	I<rxvt-unicode> also cheats a bit by not providing blocking access to	1969	I<rxvt-unicode> also cheats a bit by not providing blocking access to
634	condition variables: code blocking while waiting for a condition will	1970	condition variables: code blocking while waiting for a condition will
635	C<die>. This still works with most modules/usages, and blocking calls must	1971	C<die>. This still works with most modules/usages, and blocking calls must
636	not be done in an interactive application, so it makes sense.	1972	not be done in an interactive application, so it makes sense.
637		1973
638	=head1 ENVIRONMENT VARIABLES
639
640	The following environment variables are used by this module:
641
642	C<PERL_ANYEVENT_VERBOSE> when set to C<2> or higher, cause AnyEvent to
643	report to STDERR which event model it chooses.
644
645	=head1 EXAMPLE PROGRAM	1974	=head1 EXAMPLE PROGRAM
646		1975
647	The following program uses an IO watcher to read data from STDIN, a timer	1976	The following program uses an I/O watcher to read data from STDIN, a timer
648	to display a message once per second, and a condition variable to quit the	1977	to display a message once per second, and a condition variable to quit the
649	program when the user enters quit:	1978	program when the user enters quit:
650		1979
651	use AnyEvent;	1980	use AnyEvent;
652		1981
…		…
657	poll => 'r',	1986	poll => 'r',
658	cb => sub {	1987	cb => sub {
659	warn "io event <$_[0]>\n"; # will always output <r>	1988	warn "io event <$_[0]>\n"; # will always output <r>
660	chomp (my $input = <STDIN>); # read a line	1989	chomp (my $input = <STDIN>); # read a line
661	warn "read: $input\n"; # output what has been read	1990	warn "read: $input\n"; # output what has been read
662	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	1991	$cv->send if $input =~ /^q/i; # quit program if /^q/i
663	},	1992	},
664	);	1993	);
665		1994
666	my $time_watcher; # can only be used once
667
668	sub new_timer {
669	$timer = AnyEvent->timer (after => 1, cb => sub {	1995	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
670	warn "timeout\n"; # print 'timeout' about every second	1996	warn "timeout\n"; # print 'timeout' at most every second
671	&new_timer; # and restart the time
672	});	1997	});
673	}
674		1998
675	new_timer; # create first timer
676
677	$cv->wait; # wait until user enters /^q/i	1999	$cv->recv; # wait until user enters /^q/i
678		2000
679	=head1 REAL-WORLD EXAMPLE	2001	=head1 REAL-WORLD EXAMPLE
680		2002
681	Consider the L<Net::FCP> module. It features (among others) the following	2003	Consider the L<Net::FCP> module. It features (among others) the following
682	API calls, which are to freenet what HTTP GET requests are to http:	2004	API calls, which are to freenet what HTTP GET requests are to http:
…		…
732	syswrite $txn->{fh}, $txn->{request}	2054	syswrite $txn->{fh}, $txn->{request}
733	or die "connection or write error";	2055	or die "connection or write error";
734	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	2056	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
735		2057
736	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	2058	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
737	result and signals any possible waiters that the request ahs finished:	2059	result and signals any possible waiters that the request has finished:
738		2060
739	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	2061	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
740		2062
741	if (end-of-file or data complete) {	2063	if (end-of-file or data complete) {
742	$txn->{result} = $txn->{buf};	2064	$txn->{result} = $txn->{buf};
743	$txn->{finished}->broadcast;	2065	$txn->{finished}->send;
744	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	2066	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
745	}	2067	}
746		2068
747	The C<result> method, finally, just waits for the finished signal (if the	2069	The C<result> method, finally, just waits for the finished signal (if the
748	request was already finished, it doesn't wait, of course, and returns the	2070	request was already finished, it doesn't wait, of course, and returns the
749	data:	2071	data:
750		2072
751	$txn->{finished}->wait;	2073	$txn->{finished}->recv;
752	return $txn->{result};	2074	return $txn->{result};
753		2075
754	The actual code goes further and collects all errors (C<die>s, exceptions)	2076	The actual code goes further and collects all errors (C<die>s, exceptions)
755	that occured during request processing. The C<result> method detects	2077	that occurred during request processing. The C<result> method detects
756	whether an exception as thrown (it is stored inside the $txn object)	2078	whether an exception as thrown (it is stored inside the $txn object)
757	and just throws the exception, which means connection errors and other	2079	and just throws the exception, which means connection errors and other
758	problems get reported tot he code that tries to use the result, not in a	2080	problems get reported tot he code that tries to use the result, not in a
759	random callback.	2081	random callback.
760		2082
…		…
791		2113
792	my $quit = AnyEvent->condvar;	2114	my $quit = AnyEvent->condvar;
793		2115
794	$fcp->txn_client_get ($url)->cb (sub {	2116	$fcp->txn_client_get ($url)->cb (sub {
795	...	2117	...
796	$quit->broadcast;	2118	$quit->send;
797	});	2119	});
798		2120
799	$quit->wait;	2121	$quit->recv;
		2122
		2123
		2124	=head1 BENCHMARKS
		2125
		2126	To give you an idea of the performance and overheads that AnyEvent adds
		2127	over the event loops themselves and to give you an impression of the speed
		2128	of various event loops I prepared some benchmarks.
		2129
		2130	=head2 BENCHMARKING ANYEVENT OVERHEAD
		2131
		2132	Here is a benchmark of various supported event models used natively and
		2133	through AnyEvent. The benchmark creates a lot of timers (with a zero
		2134	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
		2135	which it is), lets them fire exactly once and destroys them again.
		2136
		2137	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
		2138	distribution. It uses the L<AE> interface, which makes a real difference
		2139	for the EV and Perl backends only.
		2140
		2141	=head3 Explanation of the columns
		2142
		2143	I<watcher> is the number of event watchers created/destroyed. Since
		2144	different event models feature vastly different performances, each event
		2145	loop was given a number of watchers so that overall runtime is acceptable
		2146	and similar between tested event loop (and keep them from crashing): Glib
		2147	would probably take thousands of years if asked to process the same number
		2148	of watchers as EV in this benchmark.
		2149
		2150	I<bytes> is the number of bytes (as measured by the resident set size,
		2151	RSS) consumed by each watcher. This method of measuring captures both C
		2152	and Perl-based overheads.
		2153
		2154	I<create> is the time, in microseconds (millionths of seconds), that it
		2155	takes to create a single watcher. The callback is a closure shared between
		2156	all watchers, to avoid adding memory overhead. That means closure creation
		2157	and memory usage is not included in the figures.
		2158
		2159	I<invoke> is the time, in microseconds, used to invoke a simple
		2160	callback. The callback simply counts down a Perl variable and after it was
		2161	invoked "watcher" times, it would C<< ->send >> a condvar once to
		2162	signal the end of this phase.
		2163
		2164	I<destroy> is the time, in microseconds, that it takes to destroy a single
		2165	watcher.
		2166
		2167	=head3 Results
		2168
		2169	name watchers bytes create invoke destroy comment
		2170	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
		2171	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
		2172	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
		2173	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
		2174	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
		2175	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
		2176	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
		2177	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
		2178	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
		2179	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
		2180	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
		2181	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
		2182
		2183	=head3 Discussion
		2184
		2185	The benchmark does I<not> measure scalability of the event loop very
		2186	well. For example, a select-based event loop (such as the pure perl one)
		2187	can never compete with an event loop that uses epoll when the number of
		2188	file descriptors grows high. In this benchmark, all events become ready at
		2189	the same time, so select/poll-based implementations get an unnatural speed
		2190	boost.
		2191
		2192	Also, note that the number of watchers usually has a nonlinear effect on
		2193	overall speed, that is, creating twice as many watchers doesn't take twice
		2194	the time - usually it takes longer. This puts event loops tested with a
		2195	higher number of watchers at a disadvantage.
		2196
		2197	To put the range of results into perspective, consider that on the
		2198	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		2199	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		2200	cycles with POE.
		2201
		2202	C<EV> is the sole leader regarding speed and memory use, which are both
		2203	maximal/minimal, respectively. When using the L<AE> API there is zero
		2204	overhead (when going through the AnyEvent API create is about 5-6 times
		2205	slower, with other times being equal, so still uses far less memory than
		2206	any other event loop and is still faster than Event natively).
		2207
		2208	The pure perl implementation is hit in a few sweet spots (both the
		2209	constant timeout and the use of a single fd hit optimisations in the perl
		2210	interpreter and the backend itself). Nevertheless this shows that it
		2211	adds very little overhead in itself. Like any select-based backend its
		2212	performance becomes really bad with lots of file descriptors (and few of
		2213	them active), of course, but this was not subject of this benchmark.
		2214
		2215	The C<Event> module has a relatively high setup and callback invocation
		2216	cost, but overall scores in on the third place.
		2217
		2218	C<IO::Async> performs admirably well, about on par with C<Event>, even
		2219	when using its pure perl backend.
		2220
		2221	C<Glib>'s memory usage is quite a bit higher, but it features a
		2222	faster callback invocation and overall ends up in the same class as
		2223	C<Event>. However, Glib scales extremely badly, doubling the number of
		2224	watchers increases the processing time by more than a factor of four,
		2225	making it completely unusable when using larger numbers of watchers
		2226	(note that only a single file descriptor was used in the benchmark, so
		2227	inefficiencies of C<poll> do not account for this).
		2228
		2229	The C<Tk> adaptor works relatively well. The fact that it crashes with
		2230	more than 2000 watchers is a big setback, however, as correctness takes
		2231	precedence over speed. Nevertheless, its performance is surprising, as the
		2232	file descriptor is dup()ed for each watcher. This shows that the dup()
		2233	employed by some adaptors is not a big performance issue (it does incur a
		2234	hidden memory cost inside the kernel which is not reflected in the figures
		2235	above).
		2236
		2237	C<POE>, regardless of underlying event loop (whether using its pure perl
		2238	select-based backend or the Event module, the POE-EV backend couldn't
		2239	be tested because it wasn't working) shows abysmal performance and
		2240	memory usage with AnyEvent: Watchers use almost 30 times as much memory
		2241	as EV watchers, and 10 times as much memory as Event (the high memory
		2242	requirements are caused by requiring a session for each watcher). Watcher
		2243	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		2244	implementation.
		2245
		2246	The design of the POE adaptor class in AnyEvent can not really account
		2247	for the performance issues, though, as session creation overhead is
		2248	small compared to execution of the state machine, which is coded pretty
		2249	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		2250	using multiple sessions is not a good approach, especially regarding
		2251	memory usage, even the author of POE could not come up with a faster
		2252	design).
		2253
		2254	=head3 Summary
		2255
		2256	=over 4
		2257
		2258	=item * Using EV through AnyEvent is faster than any other event loop
		2259	(even when used without AnyEvent), but most event loops have acceptable
		2260	performance with or without AnyEvent.
		2261
		2262	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
		2263	the actual event loop, only with extremely fast event loops such as EV
		2264	adds AnyEvent significant overhead.
		2265
		2266	=item * You should avoid POE like the plague if you want performance or
		2267	reasonable memory usage.
		2268
		2269	=back
		2270
		2271	=head2 BENCHMARKING THE LARGE SERVER CASE
		2272
		2273	This benchmark actually benchmarks the event loop itself. It works by
		2274	creating a number of "servers": each server consists of a socket pair, a
		2275	timeout watcher that gets reset on activity (but never fires), and an I/O
		2276	watcher waiting for input on one side of the socket. Each time the socket
		2277	watcher reads a byte it will write that byte to a random other "server".
		2278
		2279	The effect is that there will be a lot of I/O watchers, only part of which
		2280	are active at any one point (so there is a constant number of active
		2281	fds for each loop iteration, but which fds these are is random). The
		2282	timeout is reset each time something is read because that reflects how
		2283	most timeouts work (and puts extra pressure on the event loops).
		2284
		2285	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
		2286	(1%) are active. This mirrors the activity of large servers with many
		2287	connections, most of which are idle at any one point in time.
		2288
		2289	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		2290	distribution. It uses the L<AE> interface, which makes a real difference
		2291	for the EV and Perl backends only.
		2292
		2293	=head3 Explanation of the columns
		2294
		2295	I<sockets> is the number of sockets, and twice the number of "servers" (as
		2296	each server has a read and write socket end).
		2297
		2298	I<create> is the time it takes to create a socket pair (which is
		2299	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		2300
		2301	I<request>, the most important value, is the time it takes to handle a
		2302	single "request", that is, reading the token from the pipe and forwarding
		2303	it to another server. This includes deleting the old timeout and creating
		2304	a new one that moves the timeout into the future.
		2305
		2306	=head3 Results
		2307
		2308	name sockets create request
		2309	EV 20000 62.66 7.99
		2310	Perl 20000 68.32 32.64
		2311	IOAsync 20000 174.06 101.15 epoll
		2312	IOAsync 20000 174.67 610.84 poll
		2313	Event 20000 202.69 242.91
		2314	Glib 20000 557.01 1689.52
		2315	POE 20000 341.54 12086.32 uses POE::Loop::Event
		2316
		2317	=head3 Discussion
		2318
		2319	This benchmark I<does> measure scalability and overall performance of the
		2320	particular event loop.
		2321
		2322	EV is again fastest. Since it is using epoll on my system, the setup time
		2323	is relatively high, though.
		2324
		2325	Perl surprisingly comes second. It is much faster than the C-based event
		2326	loops Event and Glib.
		2327
		2328	IO::Async performs very well when using its epoll backend, and still quite
		2329	good compared to Glib when using its pure perl backend.
		2330
		2331	Event suffers from high setup time as well (look at its code and you will
		2332	understand why). Callback invocation also has a high overhead compared to
		2333	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		2334	uses select or poll in basically all documented configurations.
		2335
		2336	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		2337	clearly fails to perform with many filehandles or in busy servers.
		2338
		2339	POE is still completely out of the picture, taking over 1000 times as long
		2340	as EV, and over 100 times as long as the Perl implementation, even though
		2341	it uses a C-based event loop in this case.
		2342
		2343	=head3 Summary
		2344
		2345	=over 4
		2346
		2347	=item * The pure perl implementation performs extremely well.
		2348
		2349	=item * Avoid Glib or POE in large projects where performance matters.
		2350
		2351	=back
		2352
		2353	=head2 BENCHMARKING SMALL SERVERS
		2354
		2355	While event loops should scale (and select-based ones do not...) even to
		2356	large servers, most programs we (or I :) actually write have only a few
		2357	I/O watchers.
		2358
		2359	In this benchmark, I use the same benchmark program as in the large server
		2360	case, but it uses only eight "servers", of which three are active at any
		2361	one time. This should reflect performance for a small server relatively
		2362	well.
		2363
		2364	The columns are identical to the previous table.
		2365
		2366	=head3 Results
		2367
		2368	name sockets create request
		2369	EV 16 20.00 6.54
		2370	Perl 16 25.75 12.62
		2371	Event 16 81.27 35.86
		2372	Glib 16 32.63 15.48
		2373	POE 16 261.87 276.28 uses POE::Loop::Event
		2374
		2375	=head3 Discussion
		2376
		2377	The benchmark tries to test the performance of a typical small
		2378	server. While knowing how various event loops perform is interesting, keep
		2379	in mind that their overhead in this case is usually not as important, due
		2380	to the small absolute number of watchers (that is, you need efficiency and
		2381	speed most when you have lots of watchers, not when you only have a few of
		2382	them).
		2383
		2384	EV is again fastest.
		2385
		2386	Perl again comes second. It is noticeably faster than the C-based event
		2387	loops Event and Glib, although the difference is too small to really
		2388	matter.
		2389
		2390	POE also performs much better in this case, but is is still far behind the
		2391	others.
		2392
		2393	=head3 Summary
		2394
		2395	=over 4
		2396
		2397	=item * C-based event loops perform very well with small number of
		2398	watchers, as the management overhead dominates.
		2399
		2400	=back
		2401
		2402	=head2 THE IO::Lambda BENCHMARK
		2403
		2404	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2405	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2406	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2407	shouldn't come as a surprise to anybody). As such, the benchmark is
		2408	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2409	very optimal. But how would AnyEvent compare when used without the extra
		2410	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2411
		2412	The benchmark itself creates an echo-server, and then, for 500 times,
		2413	connects to the echo server, sends a line, waits for the reply, and then
		2414	creates the next connection. This is a rather bad benchmark, as it doesn't
		2415	test the efficiency of the framework or much non-blocking I/O, but it is a
		2416	benchmark nevertheless.
		2417
		2418	name runtime
		2419	Lambda/select 0.330 sec
		2420	+ optimized 0.122 sec
		2421	Lambda/AnyEvent 0.327 sec
		2422	+ optimized 0.138 sec
		2423	Raw sockets/select 0.077 sec
		2424	POE/select, components 0.662 sec
		2425	POE/select, raw sockets 0.226 sec
		2426	POE/select, optimized 0.404 sec
		2427
		2428	AnyEvent/select/nb 0.085 sec
		2429	AnyEvent/EV/nb 0.068 sec
		2430	+state machine 0.134 sec
		2431
		2432	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2433	benchmarks actually make blocking connects and use 100% blocking I/O,
		2434	defeating the purpose of an event-based solution. All of the newly
		2435	written AnyEvent benchmarks use 100% non-blocking connects (using
		2436	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2437	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2438	generally require a lot more bookkeeping and event handling than blocking
		2439	connects (which involve a single syscall only).
		2440
		2441	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2442	offers similar expressive power as POE and IO::Lambda, using conventional
		2443	Perl syntax. This means that both the echo server and the client are 100%
		2444	non-blocking, further placing it at a disadvantage.
		2445
		2446	As you can see, the AnyEvent + EV combination even beats the
		2447	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2448	backend easily beats IO::Lambda and POE.
		2449
		2450	And even the 100% non-blocking version written using the high-level (and
		2451	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda
		2452	higher level ("unoptimised") abstractions by a large margin, even though
		2453	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
		2454
		2455	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2456	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2457	part of the IO::Lambda distribution and were used without any changes.
		2458
		2459
		2460	=head1 SIGNALS
		2461
		2462	AnyEvent currently installs handlers for these signals:
		2463
		2464	=over 4
		2465
		2466	=item SIGCHLD
		2467
		2468	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2469	emulation for event loops that do not support them natively. Also, some
		2470	event loops install a similar handler.
		2471
		2472	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2473	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2474
		2475	=item SIGPIPE
		2476
		2477	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2478	when AnyEvent gets loaded.
		2479
		2480	The rationale for this is that AnyEvent users usually do not really depend
		2481	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2482	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2483	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2484	some random socket.
		2485
		2486	The rationale for installing a no-op handler as opposed to ignoring it is
		2487	that this way, the handler will be restored to defaults on exec.
		2488
		2489	Feel free to install your own handler, or reset it to defaults.
		2490
		2491	=back
		2492
		2493	=cut
		2494
		2495	undef $SIG{CHLD}
		2496	if $SIG{CHLD} eq 'IGNORE';
		2497
		2498	$SIG{PIPE} = sub { }
		2499	unless defined $SIG{PIPE};
		2500
		2501	=head1 RECOMMENDED/OPTIONAL MODULES
		2502
		2503	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2504	it's built-in modules) are required to use it.
		2505
		2506	That does not mean that AnyEvent won't take advantage of some additional
		2507	modules if they are installed.
		2508
		2509	This section explains which additional modules will be used, and how they
		2510	affect AnyEvent's operation.
		2511
		2512	=over 4
		2513
		2514	=item L<Async::Interrupt>
		2515
		2516	This slightly arcane module is used to implement fast signal handling: To
		2517	my knowledge, there is no way to do completely race-free and quick
		2518	signal handling in pure perl. To ensure that signals still get
		2519	delivered, AnyEvent will start an interval timer to wake up perl (and
		2520	catch the signals) with some delay (default is 10 seconds, look for
		2521	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2522
		2523	If this module is available, then it will be used to implement signal
		2524	catching, which means that signals will not be delayed, and the event loop
		2525	will not be interrupted regularly, which is more efficient (and good for
		2526	battery life on laptops).
		2527
		2528	This affects not just the pure-perl event loop, but also other event loops
		2529	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2530
		2531	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2532	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2533	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2534	does nothing for those backends.
		2535
		2536	=item L<EV>
		2537
		2538	This module isn't really "optional", as it is simply one of the backend
		2539	event loops that AnyEvent can use. However, it is simply the best event
		2540	loop available in terms of features, speed and stability: It supports
		2541	the AnyEvent API optimally, implements all the watcher types in XS, does
		2542	automatic timer adjustments even when no monotonic clock is available,
		2543	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2544	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2545	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2546
		2547	If you only use backends that rely on another event loop (e.g. C<Tk>),
		2548	then this module will do nothing for you.
		2549
		2550	=item L<Guard>
		2551
		2552	The guard module, when used, will be used to implement
		2553	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2554	lot less memory), but otherwise doesn't affect guard operation much. It is
		2555	purely used for performance.
		2556
		2557	=item L<JSON> and L<JSON::XS>
		2558
		2559	One of these modules is required when you want to read or write JSON data
		2560	via L<AnyEvent::Handle>. L<JSON> is also written in pure-perl, but can take
		2561	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2562
		2563	=item L<Net::SSLeay>
		2564
		2565	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2566	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2567	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2568
		2569	=item L<Time::HiRes>
		2570
		2571	This module is part of perl since release 5.008. It will be used when the
		2572	chosen event library does not come with a timing source on it's own. The
		2573	pure-perl event loop (L<AnyEvent::Impl::Perl>) will additionally use it to
		2574	try to use a monotonic clock for timing stability.
		2575
		2576	=back
		2577
		2578
		2579	=head1 FORK
		2580
		2581	Most event libraries are not fork-safe. The ones who are usually are
		2582	because they rely on inefficient but fork-safe C<select> or C<poll> calls
		2583	- higher performance APIs such as BSD's kqueue or the dreaded Linux epoll
		2584	are usually badly thought-out hacks that are incompatible with fork in
		2585	one way or another. Only L<EV> is fully fork-aware and ensures that you
		2586	continue event-processing in both parent and child (or both, if you know
		2587	what you are doing).
		2588
		2589	This means that, in general, you cannot fork and do event processing in
		2590	the child if the event library was initialised before the fork (which
		2591	usually happens when the first AnyEvent watcher is created, or the library
		2592	is loaded).
		2593
		2594	If you have to fork, you must either do so I<before> creating your first
		2595	watcher OR you must not use AnyEvent at all in the child OR you must do
		2596	something completely out of the scope of AnyEvent.
		2597
		2598	The problem of doing event processing in the parent I<and> the child
		2599	is much more complicated: even for backends that I<are> fork-aware or
		2600	fork-safe, their behaviour is not usually what you want: fork clones all
		2601	watchers, that means all timers, I/O watchers etc. are active in both
		2602	parent and child, which is almost never what you want. USing C<exec>
		2603	to start worker children from some kind of manage rprocess is usually
		2604	preferred, because it is much easier and cleaner, at the expense of having
		2605	to have another binary.
		2606
		2607
		2608	=head1 SECURITY CONSIDERATIONS
		2609
		2610	AnyEvent can be forced to load any event model via
		2611	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
		2612	execute arbitrary code or directly gain access, it can easily be used to
		2613	make the program hang or malfunction in subtle ways, as AnyEvent watchers
		2614	will not be active when the program uses a different event model than
		2615	specified in the variable.
		2616
		2617	You can make AnyEvent completely ignore this variable by deleting it
		2618	before the first watcher gets created, e.g. with a C<BEGIN> block:
		2619
		2620	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
		2621
		2622	use AnyEvent;
		2623
		2624	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		2625	be used to probe what backend is used and gain other information (which is
		2626	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2627	$ENV{PERL_ANYEVENT_STRICT}.
		2628
		2629	Note that AnyEvent will remove I<all> environment variables starting with
		2630	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2631	enabled.
		2632
		2633
		2634	=head1 BUGS
		2635
		2636	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2637	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2638	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2639	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2640	pronounced).
		2641
800		2642
801	=head1 SEE ALSO	2643	=head1 SEE ALSO
802		2644
803	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	2645	Utility functions: L<AnyEvent::Util>.
804	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>.
805		2646
806	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	2647	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
		2648	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
		2649
807	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>,	2650	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
808	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>.	2651	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
		2652	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
		2653	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>, L<Anyevent::Impl::Irssi>.
809		2654
		2655	Non-blocking file handles, sockets, TCP clients and
		2656	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
		2657
		2658	Asynchronous DNS: L<AnyEvent::DNS>.
		2659
		2660	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>,
		2661	L<Coro::Event>,
		2662
810	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	2663	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::XMPP>,
		2664	L<AnyEvent::HTTP>.
811		2665
812	=head1	2666
		2667	=head1 AUTHOR
		2668
		2669	Marc Lehmann <schmorp@schmorp.de>
		2670	http://home.schmorp.de/
813		2671
814	=cut	2672	=cut
815		2673
816	1	2674	1
817		2675

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