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Revision 1.100 by elmex, Sun Apr 27 19:15:43 2008 UTC vs.
Revision 1.263 by root, Wed Jul 29 12:39:21 2009 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent - provide framework for multiple event loops	3	AnyEvent - the DBI of event loop programming
4		4
5	EV, Event, Coro::EV, Coro::Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event loops	5	EV, Event, Glib, Tk, Perl, Event::Lib, Irssi, rxvt-unicode, IO::Async, Qt
		6	and POE are various supported event loops/environments.
6		7
7	=head1 SYNOPSIS	8	=head1 SYNOPSIS
8		9
9	use AnyEvent;	10	use AnyEvent;
10		11
		12	# file descriptor readable
11	my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub {	13	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
		14
		15	# one-shot or repeating timers
		16	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
		17	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...
		18
		19	print AnyEvent->now; # prints current event loop time
		20	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
		21
		22	# POSIX signal
		23	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
		24
		25	# child process exit
		26	my $w = AnyEvent->child (pid => $pid, cb => sub {
		27	my ($pid, $status) = @_;
12	...	28	...
13	});	29	});
14		30
15	my $w = AnyEvent->timer (after => $seconds, cb => sub {	31	# called when event loop idle (if applicable)
16	...	32	my $w = AnyEvent->idle (cb => sub { ... });
17	});
18		33
19	my $w = AnyEvent->condvar; # stores whether a condition was flagged	34	my $w = AnyEvent->condvar; # stores whether a condition was flagged
		35	$w->send; # wake up current and all future recv's
20	$w->wait; # enters "main loop" till $condvar gets ->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	#TODO#
72
73	Net::IRC3
74	AnyEvent::HTTPD
75	AnyEvent::DNS
76	IO::AnyEvent
77	Net::FPing
78	Net::XMPP2
79	Coro
80
81	AnyEvent::IRC
82	AnyEvent::HTTPD
83	AnyEvent::DNS
84	AnyEvent::Handle
85	AnyEvent::Socket
86	AnyEvent::FPing
87	AnyEvent::XMPP
88	AnyEvent::SNMP
89	Coro
90		108
91	=head1 DESCRIPTION	109	=head1 DESCRIPTION
92		110
93	L<AnyEvent> provides an identical interface to multiple event loops. This	111	L<AnyEvent> provides an identical interface to multiple event loops. This
94	allows module authors to utilise an event loop without forcing module	112	allows module authors to utilise an event loop without forcing module
…		…
98	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>
99	module.	117	module.
100		118
101	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
102	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
103	following modules is already loaded: L<Coro::EV>, L<Coro::Event>, L<EV>,	121	following modules is already loaded: L<EV>,
104	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,	122	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,
105	L<POE>. The first one found is used. If none are found, the module tries	123	L<POE>. The first one found is used. If none are found, the module tries
106	to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl	124	to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl
107	adaptor should always succeed) in the order given. The first one that can	125	adaptor should always succeed) in the order given. The first one that can
108	be successfully loaded will be used. If, after this, still none could be	126	be successfully loaded will be used. If, after this, still none could be
…		…
122	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
123	use AnyEvent so their modules work together with others seamlessly...	141	use AnyEvent so their modules work together with others seamlessly...
124		142
125	The pure-perl implementation of AnyEvent is called	143	The pure-perl implementation of AnyEvent is called
126	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
127	explicitly.	145	explicitly and enjoy the high availability of that event loop :)
128		146
129	=head1 WATCHERS	147	=head1 WATCHERS
130		148
131	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
132	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
133	the callback to call, the filehandle to watch, etc.	151	the callback to call, the file handle to watch, etc.
134		152
135	These watchers are normal Perl objects with normal Perl lifetime. After	153	These watchers are normal Perl objects with normal Perl lifetime. After
136	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
137	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
138	is in control).	156	is in control).
139		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
140	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
141	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
142	to it).	166	to it).
143		167
144	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.
…		…
146	Many watchers either are used with "recursion" (repeating timers for	170	Many watchers either are used with "recursion" (repeating timers for
147	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.
148		172
149	An any way to achieve that is this pattern:	173	An any way to achieve that is this pattern:
150		174
151	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	175	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
152	# you can use $w here, for example to undef it	176	# you can use $w here, for example to undef it
153	undef $w;	177	undef $w;
154	});	178	});
155		179
156	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,
157	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
158	declared.	182	declared.
159		183
160	=head2 I/O WATCHERS	184	=head2 I/O WATCHERS
161		185
162	You can create an I/O watcher by calling the C<< AnyEvent->io >> method	186	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
163	with the following mandatory key-value pairs as arguments:	187	with the following mandatory key-value pairs as arguments:
164		188
165	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch	189	C<fh> is the Perl I<file handle> (or a naked file descriptor) to watch
		190	for events (AnyEvent might or might not keep a reference to this file
		191	handle). Note that only file handles pointing to things for which
		192	non-blocking operation makes sense are allowed. This includes sockets,
		193	most character devices, pipes, fifos and so on, but not for example files
		194	or block devices.
		195
166	for events. C<poll> must be a string that is either C<r> or C<w>,	196	C<poll> must be a string that is either C<r> or C<w>, which creates a
167	which creates a watcher waiting for "r"eadable or "w"ritable events,	197	watcher waiting for "r"eadable or "w"ritable events, respectively.
		198
168	respectively. C<cb> is the callback to invoke each time the file handle	199	C<cb> is the callback to invoke each time the file handle becomes ready.
169	becomes ready.
170		200
171	Although the callback might get passed parameters, their value and	201	Although the callback might get passed parameters, their value and
172	presence is undefined and you cannot rely on them. Portable AnyEvent	202	presence is undefined and you cannot rely on them. Portable AnyEvent
173	callbacks cannot use arguments passed to I/O watcher callbacks.	203	callbacks cannot use arguments passed to I/O watcher callbacks.
174		204
…		…
178		208
179	Some event loops issue spurious readyness notifications, so you should	209	Some event loops issue spurious readyness notifications, so you should
180	always use non-blocking calls when reading/writing from/to your file	210	always use non-blocking calls when reading/writing from/to your file
181	handles.	211	handles.
182		212
183	Example:
184
185	# wait for readability of STDIN, then read a line and disable the watcher	213	Example: wait for readability of STDIN, then read a line and disable the
		214	watcher.
		215
186	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	216	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
187	chomp (my $input = <STDIN>);	217	chomp (my $input = <STDIN>);
188	warn "read: $input\n";	218	warn "read: $input\n";
189	undef $w;	219	undef $w;
190	});	220	});
…		…
200		230
201	Although the callback might get passed parameters, their value and	231	Although the callback might get passed parameters, their value and
202	presence is undefined and you cannot rely on them. Portable AnyEvent	232	presence is undefined and you cannot rely on them. Portable AnyEvent
203	callbacks cannot use arguments passed to time watcher callbacks.	233	callbacks cannot use arguments passed to time watcher callbacks.
204		234
205	The timer callback will be invoked at most once: if you want a repeating	235	The callback will normally be invoked once only. If you specify another
206	timer you have to create a new watcher (this is a limitation by both Tk	236	parameter, C<interval>, as a strictly positive number (> 0), then the
207	and Glib).	237	callback will be invoked regularly at that interval (in fractional
		238	seconds) after the first invocation. If C<interval> is specified with a
		239	false value, then it is treated as if it were missing.
208		240
209	Example:	241	The callback will be rescheduled before invoking the callback, but no
		242	attempt is done to avoid timer drift in most backends, so the interval is
		243	only approximate.
210		244
211	# fire an event after 7.7 seconds	245	Example: fire an event after 7.7 seconds.
		246
212	my $w = AnyEvent->timer (after => 7.7, cb => sub {	247	my $w = AnyEvent->timer (after => 7.7, cb => sub {
213	warn "timeout\n";	248	warn "timeout\n";
214	});	249	});
215		250
216	# to cancel the timer:	251	# to cancel the timer:
217	undef $w;	252	undef $w;
218		253
219	Example 2:
220
221	# fire an event after 0.5 seconds, then roughly every second	254	Example 2: fire an event after 0.5 seconds, then roughly every second.
222	my $w;
223		255
224	my $cb = sub {
225	# cancel the old timer while creating a new one
226	$w = AnyEvent->timer (after => 1, cb => $cb);	256	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		257	warn "timeout\n";
227	};	258	};
228
229	# start the "loop" by creating the first watcher
230	$w = AnyEvent->timer (after => 0.5, cb => $cb);
231		259
232	=head3 TIMING ISSUES	260	=head3 TIMING ISSUES
233		261
234	There are two ways to handle timers: based on real time (relative, "fire	262	There are two ways to handle timers: based on real time (relative, "fire
235	in 10 seconds") and based on wallclock time (absolute, "fire at 12	263	in 10 seconds") and based on wallclock time (absolute, "fire at 12
…		…
247	timers.	275	timers.
248		276
249	AnyEvent always prefers relative timers, if available, matching the	277	AnyEvent always prefers relative timers, if available, matching the
250	AnyEvent API.	278	AnyEvent API.
251		279
		280	AnyEvent has two additional methods that return the "current time":
		281
		282	=over 4
		283
		284	=item AnyEvent->time
		285
		286	This returns the "current wallclock time" as a fractional number of
		287	seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
		288	return, and the result is guaranteed to be compatible with those).
		289
		290	It progresses independently of any event loop processing, i.e. each call
		291	will check the system clock, which usually gets updated frequently.
		292
		293	=item AnyEvent->now
		294
		295	This also returns the "current wallclock time", but unlike C<time>, above,
		296	this value might change only once per event loop iteration, depending on
		297	the event loop (most return the same time as C<time>, above). This is the
		298	time that AnyEvent's timers get scheduled against.
		299
		300	I<In almost all cases (in all cases if you don't care), this is the
		301	function to call when you want to know the current time.>
		302
		303	This function is also often faster then C<< AnyEvent->time >>, and
		304	thus the preferred method if you want some timestamp (for example,
		305	L<AnyEvent::Handle> uses this to update it's activity timeouts).
		306
		307	The rest of this section is only of relevance if you try to be very exact
		308	with your timing, you can skip it without bad conscience.
		309
		310	For a practical example of when these times differ, consider L<Event::Lib>
		311	and L<EV> and the following set-up:
		312
		313	The event loop is running and has just invoked one of your callback at
		314	time=500 (assume no other callbacks delay processing). In your callback,
		315	you wait a second by executing C<sleep 1> (blocking the process for a
		316	second) and then (at time=501) you create a relative timer that fires
		317	after three seconds.
		318
		319	With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
		320	both return C<501>, because that is the current time, and the timer will
		321	be scheduled to fire at time=504 (C<501> + C<3>).
		322
		323	With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
		324	time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
		325	last event processing phase started. With L<EV>, your timer gets scheduled
		326	to run at time=503 (C<500> + C<3>).
		327
		328	In one sense, L<Event::Lib> is more exact, as it uses the current time
		329	regardless of any delays introduced by event processing. However, most
		330	callbacks do not expect large delays in processing, so this causes a
		331	higher drift (and a lot more system calls to get the current time).
		332
		333	In another sense, L<EV> is more exact, as your timer will be scheduled at
		334	the same time, regardless of how long event processing actually took.
		335
		336	In either case, if you care (and in most cases, you don't), then you
		337	can get whatever behaviour you want with any event loop, by taking the
		338	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
		339	account.
		340
		341	=item AnyEvent->now_update
		342
		343	Some event loops (such as L<EV> or L<AnyEvent::Impl::Perl>) cache
		344	the current time for each loop iteration (see the discussion of L<<
		345	AnyEvent->now >>, above).
		346
		347	When a callback runs for a long time (or when the process sleeps), then
		348	this "current" time will differ substantially from the real time, which
		349	might affect timers and time-outs.
		350
		351	When this is the case, you can call this method, which will update the
		352	event loop's idea of "current time".
		353
		354	Note that updating the time I<might> cause some events to be handled.
		355
		356	=back
		357
252	=head2 SIGNAL WATCHERS	358	=head2 SIGNAL WATCHERS
253		359
254	You can watch for signals using a signal watcher, C<signal> is the signal	360	You can watch for signals using a signal watcher, C<signal> is the signal
255	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to	361	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
256	be invoked whenever a signal occurs.	362	callback to be invoked whenever a signal occurs.
257		363
258	Although the callback might get passed parameters, their value and	364	Although the callback might get passed parameters, their value and
259	presence is undefined and you cannot rely on them. Portable AnyEvent	365	presence is undefined and you cannot rely on them. Portable AnyEvent
260	callbacks cannot use arguments passed to signal watcher callbacks.	366	callbacks cannot use arguments passed to signal watcher callbacks.
261		367
262	Multiple signal occurances can be clumped together into one callback	368	Multiple signal occurrences can be clumped together into one callback
263	invocation, and callback invocation will be synchronous. synchronous means	369	invocation, and callback invocation will be synchronous. Synchronous means
264	that it might take a while until the signal gets handled by the process,	370	that it might take a while until the signal gets handled by the process,
265	but it is guarenteed not to interrupt any other callbacks.	371	but it is guaranteed not to interrupt any other callbacks.
266		372
267	The main advantage of using these watchers is that you can share a signal	373	The main advantage of using these watchers is that you can share a signal
268	between multiple watchers.	374	between multiple watchers, and AnyEvent will ensure that signals will not
		375	interrupt your program at bad times.
269		376
270	This watcher might use C<%SIG>, so programs overwriting those signals	377	This watcher might use C<%SIG> (depending on the event loop used),
271	directly will likely not work correctly.	378	so programs overwriting those signals directly will likely not work
		379	correctly.
272		380
273	Example: exit on SIGINT	381	Example: exit on SIGINT
274		382
275	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	383	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
276		384
		385	=head3 Signal Races, Delays and Workarounds
		386
		387	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		388	callbacks to signals in a generic way, which is a pity, as you cannot do
		389	race-free signal handling in perl. AnyEvent will try to do it's best, but
		390	in some cases, signals will be delayed. The maximum time a signal might
		391	be delayed is specified in C<$AnyEvent::MAX_SIGNAL_LATENCY> (default: 10
		392	seconds). This variable can be changed only before the first signal
		393	watcher is created, and should be left alone otherwise. Higher values
		394	will cause fewer spurious wake-ups, which is better for power and CPU
		395	saving. All these problems can be avoided by installing the optional
		396	L<Async::Interrupt> module. This will not work with inherently broken
		397	event loops such as L<Event> or L<Event::Lib> (and not with L<POE>
		398	currently, as POE does it's own workaround with one-second latency). With
		399	those, you just have to suffer the delays.
		400
277	=head2 CHILD PROCESS WATCHERS	401	=head2 CHILD PROCESS WATCHERS
278		402
279	You can also watch on a child process exit and catch its exit status.	403	You can also watch on a child process exit and catch its exit status.
280		404
281	The child process is specified by the C<pid> argument (if set to C<0>, it	405	The child process is specified by the C<pid> argument (one some backends,
282	watches for any child process exit). The watcher will trigger as often	406	using C<0> watches for any child process exit, on others this will
283	as status change for the child are received. This works by installing a	407	croak). The watcher will be triggered only when the child process has
284	signal handler for C<SIGCHLD>. The callback will be called with the pid	408	finished and an exit status is available, not on any trace events
285	and exit status (as returned by waitpid), so unlike other watcher types,	409	(stopped/continued).
286	you I<can> rely on child watcher callback arguments.	410
		411	The callback will be called with the pid and exit status (as returned by
		412	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		413	callback arguments.
		414
		415	This watcher type works by installing a signal handler for C<SIGCHLD>,
		416	and since it cannot be shared, nothing else should use SIGCHLD or reap
		417	random child processes (waiting for specific child processes, e.g. inside
		418	C<system>, is just fine).
287		419
288	There is a slight catch to child watchers, however: you usually start them	420	There is a slight catch to child watchers, however: you usually start them
289	I<after> the child process was created, and this means the process could	421	I<after> the child process was created, and this means the process could
290	have exited already (and no SIGCHLD will be sent anymore).	422	have exited already (and no SIGCHLD will be sent anymore).
291		423
292	Not all event models handle this correctly (POE doesn't), but even for	424	Not all event models handle this correctly (neither POE nor IO::Async do,
		425	see their AnyEvent::Impl manpages for details), but even for event models
293	event models that I<do> handle this correctly, they usually need to be	426	that I<do> handle this correctly, they usually need to be loaded before
294	loaded before the process exits (i.e. before you fork in the first place).	427	the process exits (i.e. before you fork in the first place). AnyEvent's
		428	pure perl event loop handles all cases correctly regardless of when you
		429	start the watcher.
295		430
296	This means you cannot create a child watcher as the very first thing in an	431	This means you cannot create a child watcher as the very first
297	AnyEvent program, you I<have> to create at least one watcher before you	432	thing in an AnyEvent program, you I<have> to create at least one
298	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).	433	watcher before you C<fork> the child (alternatively, you can call
		434	C<AnyEvent::detect>).
		435
		436	As most event loops do not support waiting for child events, they will be
		437	emulated by AnyEvent in most cases, in which the latency and race problems
		438	mentioned in the description of signal watchers apply.
299		439
300	Example: fork a process and wait for it	440	Example: fork a process and wait for it
301		441
302	my $done = AnyEvent->condvar;	442	my $done = AnyEvent->condvar;
303		443
304	AnyEvent::detect; # force event module to be initialised
305
306	my $pid = fork or exit 5;	444	my $pid = fork or exit 5;
307		445
308	my $w = AnyEvent->child (	446	my $w = AnyEvent->child (
309	pid => $pid,	447	pid => $pid,
310	cb => sub {	448	cb => sub {
311	my ($pid, $status) = @_;	449	my ($pid, $status) = @_;
312	warn "pid $pid exited with status $status";	450	warn "pid $pid exited with status $status";
313	$done->broadcast;	451	$done->send;
314	},	452	},
315	);	453	);
316		454
317	# do something else, then wait for process exit	455	# do something else, then wait for process exit
318	$done->wait;	456	$done->recv;
		457
		458	=head2 IDLE WATCHERS
		459
		460	Sometimes there is a need to do something, but it is not so important
		461	to do it instantly, but only when there is nothing better to do. This
		462	"nothing better to do" is usually defined to be "no other events need
		463	attention by the event loop".
		464
		465	Idle watchers ideally get invoked when the event loop has nothing
		466	better to do, just before it would block the process to wait for new
		467	events. Instead of blocking, the idle watcher is invoked.
		468
		469	Most event loops unfortunately do not really support idle watchers (only
		470	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		471	will simply call the callback "from time to time".
		472
		473	Example: read lines from STDIN, but only process them when the
		474	program is otherwise idle:
		475
		476	my @lines; # read data
		477	my $idle_w;
		478	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		479	push @lines, scalar <STDIN>;
		480
		481	# start an idle watcher, if not already done
		482	$idle_w ||= AnyEvent->idle (cb => sub {
		483	# handle only one line, when there are lines left
		484	if (my $line = shift @lines) {
		485	print "handled when idle: $line";
		486	} else {
		487	# otherwise disable the idle watcher again
		488	undef $idle_w;
		489	}
		490	});
		491	});
319		492
320	=head2 CONDITION VARIABLES	493	=head2 CONDITION VARIABLES
321		494
		495	If you are familiar with some event loops you will know that all of them
		496	require you to run some blocking "loop", "run" or similar function that
		497	will actively watch for new events and call your callbacks.
		498
		499	AnyEvent is slightly different: it expects somebody else to run the event
		500	loop and will only block when necessary (usually when told by the user).
		501
		502	The instrument to do that is called a "condition variable", so called
		503	because they represent a condition that must become true.
		504
		505	Now is probably a good time to look at the examples further below.
		506
322	Condition variables can be created by calling the C<< AnyEvent->condvar >>	507	Condition variables can be created by calling the C<< AnyEvent->condvar
323	method without any arguments.	508	>> method, usually without arguments. The only argument pair allowed is
		509	C<cb>, which specifies a callback to be called when the condition variable
		510	becomes true, with the condition variable as the first argument (but not
		511	the results).
324		512
325	A condition variable waits for a condition - precisely that the C<<	513	After creation, the condition variable is "false" until it becomes "true"
326	->broadcast >> method has been called.	514	by calling the C<send> method (or calling the condition variable as if it
		515	were a callback, read about the caveats in the description for the C<<
		516	->send >> method).
327		517
328	They are very useful to signal that a condition has been fulfilled, for	518	Condition variables are similar to callbacks, except that you can
		519	optionally wait for them. They can also be called merge points - points
		520	in time where multiple outstanding events have been processed. And yet
		521	another way to call them is transactions - each condition variable can be
		522	used to represent a transaction, which finishes at some point and delivers
		523	a result. And yet some people know them as "futures" - a promise to
		524	compute/deliver something that you can wait for.
		525
		526	Condition variables are very useful to signal that something has finished,
329	example, if you write a module that does asynchronous http requests,	527	for example, if you write a module that does asynchronous http requests,
330	then a condition variable would be the ideal candidate to signal the	528	then a condition variable would be the ideal candidate to signal the
331	availability of results.	529	availability of results. The user can either act when the callback is
		530	called or can synchronously C<< ->recv >> for the results.
332		531
333	You can also use condition variables to block your main program until	532	You can also use them to simulate traditional event loops - for example,
334	an event occurs - for example, you could C<< ->wait >> in your main	533	you can block your main program until an event occurs - for example, you
335	program until the user clicks the Quit button in your app, which would C<<	534	could C<< ->recv >> in your main program until the user clicks the Quit
336	->broadcast >> the "quit" event.	535	button of your app, which would C<< ->send >> the "quit" event.
337		536
338	Note that condition variables recurse into the event loop - if you have	537	Note that condition variables recurse into the event loop - if you have
339	two pirces of code that call C<< ->wait >> in a round-robbin fashion, you	538	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
340	lose. Therefore, condition variables are good to export to your caller, but	539	lose. Therefore, condition variables are good to export to your caller, but
341	you should avoid making a blocking wait yourself, at least in callbacks,	540	you should avoid making a blocking wait yourself, at least in callbacks,
342	as this asks for trouble.	541	as this asks for trouble.
343		542
344	This object has two methods:	543	Condition variables are represented by hash refs in perl, and the keys
		544	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
		545	easy (it is often useful to build your own transaction class on top of
		546	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
		547	it's C<new> method in your own C<new> method.
345		548
346	=over 4	549	There are two "sides" to a condition variable - the "producer side" which
		550	eventually calls C<< -> send >>, and the "consumer side", which waits
		551	for the send to occur.
347		552
348	=item $cv->wait	553	Example: wait for a timer.
349
350	Wait (blocking if necessary) until the C<< ->broadcast >> method has been
351	called on c<$cv>, while servicing other watchers normally.
352
353	You can only wait once on a condition - additional calls will return
354	immediately.
355
356	Not all event models support a blocking wait - some die in that case
357	(programs might want to do that to stay interactive), so I<if you are
358	using this from a module, never require a blocking wait>, but let the
359	caller decide whether the call will block or not (for example, by coupling
360	condition variables with some kind of request results and supporting
361	callbacks so the caller knows that getting the result will not block,
362	while still suppporting blocking waits if the caller so desires).
363
364	Another reason I<never> to C<< ->wait >> in a module is that you cannot
365	sensibly have two C<< ->wait >>'s in parallel, as that would require
366	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
367	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and
368	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
369	from different coroutines, however).
370
371	=item $cv->broadcast
372
373	Flag the condition as ready - a running C<< ->wait >> and all further
374	calls to C<wait> will (eventually) return after this method has been
375	called. If nobody is waiting the broadcast will be remembered..
376
377	=back
378
379	Example:
380		554
381	# wait till the result is ready	555	# wait till the result is ready
382	my $result_ready = AnyEvent->condvar;	556	my $result_ready = AnyEvent->condvar;
383		557
384	# do something such as adding a timer	558	# do something such as adding a timer
385	# or socket watcher the calls $result_ready->broadcast	559	# or socket watcher the calls $result_ready->send
386	# when the "result" is ready.	560	# when the "result" is ready.
387	# in this case, we simply use a timer:	561	# in this case, we simply use a timer:
388	my $w = AnyEvent->timer (	562	my $w = AnyEvent->timer (
389	after => 1,	563	after => 1,
390	cb => sub { $result_ready->broadcast },	564	cb => sub { $result_ready->send },
391	);	565	);
392		566
393	# this "blocks" (while handling events) till the watcher	567	# this "blocks" (while handling events) till the callback
394	# calls broadcast	568	# calls -<send
395	$result_ready->wait;	569	$result_ready->recv;
		570
		571	Example: wait for a timer, but take advantage of the fact that condition
		572	variables are also callable directly.
		573
		574	my $done = AnyEvent->condvar;
		575	my $delay = AnyEvent->timer (after => 5, cb => $done);
		576	$done->recv;
		577
		578	Example: Imagine an API that returns a condvar and doesn't support
		579	callbacks. This is how you make a synchronous call, for example from
		580	the main program:
		581
		582	use AnyEvent::CouchDB;
		583
		584	...
		585
		586	my @info = $couchdb->info->recv;
		587
		588	And this is how you would just set a callback to be called whenever the
		589	results are available:
		590
		591	$couchdb->info->cb (sub {
		592	my @info = $_[0]->recv;
		593	});
		594
		595	=head3 METHODS FOR PRODUCERS
		596
		597	These methods should only be used by the producing side, i.e. the
		598	code/module that eventually sends the signal. Note that it is also
		599	the producer side which creates the condvar in most cases, but it isn't
		600	uncommon for the consumer to create it as well.
		601
		602	=over 4
		603
		604	=item $cv->send (...)
		605
		606	Flag the condition as ready - a running C<< ->recv >> and all further
		607	calls to C<recv> will (eventually) return after this method has been
		608	called. If nobody is waiting the send will be remembered.
		609
		610	If a callback has been set on the condition variable, it is called
		611	immediately from within send.
		612
		613	Any arguments passed to the C<send> call will be returned by all
		614	future C<< ->recv >> calls.
		615
		616	Condition variables are overloaded so one can call them directly (as if
		617	they were a code reference). Calling them directly is the same as calling
		618	C<send>.
		619
		620	=item $cv->croak ($error)
		621
		622	Similar to send, but causes all call's to C<< ->recv >> to invoke
		623	C<Carp::croak> with the given error message/object/scalar.
		624
		625	This can be used to signal any errors to the condition variable
		626	user/consumer. Doing it this way instead of calling C<croak> directly
		627	delays the error detetcion, but has the overwhelmign advantage that it
		628	diagnoses the error at the place where the result is expected, and not
		629	deep in some event clalback without connection to the actual code causing
		630	the problem.
		631
		632	=item $cv->begin ([group callback])
		633
		634	=item $cv->end
		635
		636	These two methods can be used to combine many transactions/events into
		637	one. For example, a function that pings many hosts in parallel might want
		638	to use a condition variable for the whole process.
		639
		640	Every call to C<< ->begin >> will increment a counter, and every call to
		641	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
		642	>>, the (last) callback passed to C<begin> will be executed. That callback
		643	is I<supposed> to call C<< ->send >>, but that is not required. If no
		644	callback was set, C<send> will be called without any arguments.
		645
		646	You can think of C<< $cv->send >> giving you an OR condition (one call
		647	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		648	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		649
		650	Let's start with a simple example: you have two I/O watchers (for example,
		651	STDOUT and STDERR for a program), and you want to wait for both streams to
		652	close before activating a condvar:
		653
		654	my $cv = AnyEvent->condvar;
		655
		656	$cv->begin; # first watcher
		657	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		658	defined sysread $fh1, my $buf, 4096
		659	or $cv->end;
		660	});
		661
		662	$cv->begin; # second watcher
		663	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		664	defined sysread $fh2, my $buf, 4096
		665	or $cv->end;
		666	});
		667
		668	$cv->recv;
		669
		670	This works because for every event source (EOF on file handle), there is
		671	one call to C<begin>, so the condvar waits for all calls to C<end> before
		672	sending.
		673
		674	The ping example mentioned above is slightly more complicated, as the
		675	there are results to be passwd back, and the number of tasks that are
		676	begung can potentially be zero:
		677
		678	my $cv = AnyEvent->condvar;
		679
		680	my %result;
		681	$cv->begin (sub { $cv->send (\%result) });
		682
		683	for my $host (@list_of_hosts) {
		684	$cv->begin;
		685	ping_host_then_call_callback $host, sub {
		686	$result{$host} = ...;
		687	$cv->end;
		688	};
		689	}
		690
		691	$cv->end;
		692
		693	This code fragment supposedly pings a number of hosts and calls
		694	C<send> after results for all then have have been gathered - in any
		695	order. To achieve this, the code issues a call to C<begin> when it starts
		696	each ping request and calls C<end> when it has received some result for
		697	it. Since C<begin> and C<end> only maintain a counter, the order in which
		698	results arrive is not relevant.
		699
		700	There is an additional bracketing call to C<begin> and C<end> outside the
		701	loop, which serves two important purposes: first, it sets the callback
		702	to be called once the counter reaches C<0>, and second, it ensures that
		703	C<send> is called even when C<no> hosts are being pinged (the loop
		704	doesn't execute once).
		705
		706	This is the general pattern when you "fan out" into multiple (but
		707	potentially none) subrequests: use an outer C<begin>/C<end> pair to set
		708	the callback and ensure C<end> is called at least once, and then, for each
		709	subrequest you start, call C<begin> and for each subrequest you finish,
		710	call C<end>.
		711
		712	=back
		713
		714	=head3 METHODS FOR CONSUMERS
		715
		716	These methods should only be used by the consuming side, i.e. the
		717	code awaits the condition.
		718
		719	=over 4
		720
		721	=item $cv->recv
		722
		723	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
		724	>> methods have been called on c<$cv>, while servicing other watchers
		725	normally.
		726
		727	You can only wait once on a condition - additional calls are valid but
		728	will return immediately.
		729
		730	If an error condition has been set by calling C<< ->croak >>, then this
		731	function will call C<croak>.
		732
		733	In list context, all parameters passed to C<send> will be returned,
		734	in scalar context only the first one will be returned.
		735
		736	Note that doing a blocking wait in a callback is not supported by any
		737	event loop, that is, recursive invocation of a blocking C<< ->recv
		738	>> is not allowed, and the C<recv> call will C<croak> if such a
		739	condition is detected. This condition can be slightly loosened by using
		740	L<Coro::AnyEvent>, which allows you to do a blocking C<< ->recv >> from
		741	any thread that doesn't run the event loop itself.
		742
		743	Not all event models support a blocking wait - some die in that case
		744	(programs might want to do that to stay interactive), so I<if you are
		745	using this from a module, never require a blocking wait>. Instead, let the
		746	caller decide whether the call will block or not (for example, by coupling
		747	condition variables with some kind of request results and supporting
		748	callbacks so the caller knows that getting the result will not block,
		749	while still supporting blocking waits if the caller so desires).
		750
		751	You can ensure that C<< -recv >> never blocks by setting a callback and
		752	only calling C<< ->recv >> from within that callback (or at a later
		753	time). This will work even when the event loop does not support blocking
		754	waits otherwise.
		755
		756	=item $bool = $cv->ready
		757
		758	Returns true when the condition is "true", i.e. whether C<send> or
		759	C<croak> have been called.
		760
		761	=item $cb = $cv->cb ($cb->($cv))
		762
		763	This is a mutator function that returns the callback set and optionally
		764	replaces it before doing so.
		765
		766	The callback will be called when the condition becomes "true", i.e. when
		767	C<send> or C<croak> are called, with the only argument being the condition
		768	variable itself. Calling C<recv> inside the callback or at any later time
		769	is guaranteed not to block.
		770
		771	=back
		772
		773	=head1 SUPPORTED EVENT LOOPS/BACKENDS
		774
		775	The available backend classes are (every class has its own manpage):
		776
		777	=over 4
		778
		779	=item Backends that are autoprobed when no other event loop can be found.
		780
		781	EV is the preferred backend when no other event loop seems to be in
		782	use. If EV is not installed, then AnyEvent will try Event, and, failing
		783	that, will fall back to its own pure-perl implementation, which is
		784	available everywhere as it comes with AnyEvent itself.
		785
		786	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		787	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		788	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
		789
		790	=item Backends that are transparently being picked up when they are used.
		791
		792	These will be used when they are currently loaded when the first watcher
		793	is created, in which case it is assumed that the application is using
		794	them. This means that AnyEvent will automatically pick the right backend
		795	when the main program loads an event module before anything starts to
		796	create watchers. Nothing special needs to be done by the main program.
		797
		798	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		799	AnyEvent::Impl::Tk based on Tk, very broken.
		800	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		801	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		802	AnyEvent::Impl::Irssi used when running within irssi.
		803
		804	=item Backends with special needs.
		805
		806	Qt requires the Qt::Application to be instantiated first, but will
		807	otherwise be picked up automatically. As long as the main program
		808	instantiates the application before any AnyEvent watchers are created,
		809	everything should just work.
		810
		811	AnyEvent::Impl::Qt based on Qt.
		812
		813	Support for IO::Async can only be partial, as it is too broken and
		814	architecturally limited to even support the AnyEvent API. It also
		815	is the only event loop that needs the loop to be set explicitly, so
		816	it can only be used by a main program knowing about AnyEvent. See
		817	L<AnyEvent::Impl::Async> for the gory details.
		818
		819	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
		820
		821	=item Event loops that are indirectly supported via other backends.
		822
		823	Some event loops can be supported via other modules:
		824
		825	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		826
		827	B<WxWidgets> has no support for watching file handles. However, you can
		828	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		829	polls 20 times per second, which was considered to be too horrible to even
		830	consider for AnyEvent.
		831
		832	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		833	backend, so it can be supported through POE.
		834
		835	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		836	load L<POE> when detecting them, in the hope that POE will pick them up,
		837	in which case everything will be automatic.
		838
		839	=back
396		840
397	=head1 GLOBAL VARIABLES AND FUNCTIONS	841	=head1 GLOBAL VARIABLES AND FUNCTIONS
398		842
		843	These are not normally required to use AnyEvent, but can be useful to
		844	write AnyEvent extension modules.
		845
399	=over 4	846	=over 4
400		847
401	=item $AnyEvent::MODEL	848	=item $AnyEvent::MODEL
402		849
403	Contains C<undef> until the first watcher is being created. Then it	850	Contains C<undef> until the first watcher is being created, before the
		851	backend has been autodetected.
		852
404	contains the event model that is being used, which is the name of the	853	Afterwards it contains the event model that is being used, which is the
405	Perl class implementing the model. This class is usually one of the	854	name of the Perl class implementing the model. This class is usually one
406	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	855	of the C<AnyEvent::Impl:xxx> modules, but can be any other class in the
407	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	856	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
408		857	will be C<urxvt::anyevent>).
409	The known classes so far are:
410
411	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
412	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
413	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
414	AnyEvent::Impl::Event based on Event, second best choice.
415	AnyEvent::Impl::Glib based on Glib, third-best choice.
416	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
417	AnyEvent::Impl::Tk based on Tk, very bad choice.
418	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
419	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
420	AnyEvent::Impl::POE based on POE, not generic enough for full support.
421
422	There is no support for WxWidgets, as WxWidgets has no support for
423	watching file handles. However, you can use WxWidgets through the
424	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
425	second, which was considered to be too horrible to even consider for
426	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
427	it's adaptor.
428
429	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
430	autodetecting them.
431		858
432	=item AnyEvent::detect	859	=item AnyEvent::detect
433		860
434	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	861	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
435	if necessary. You should only call this function right before you would	862	if necessary. You should only call this function right before you would
436	have created an AnyEvent watcher anyway, that is, as late as possible at	863	have created an AnyEvent watcher anyway, that is, as late as possible at
437	runtime.	864	runtime, and not e.g. while initialising of your module.
		865
		866	If you need to do some initialisation before AnyEvent watchers are
		867	created, use C<post_detect>.
		868
		869	=item $guard = AnyEvent::post_detect { BLOCK }
		870
		871	Arranges for the code block to be executed as soon as the event model is
		872	autodetected (or immediately if this has already happened).
		873
		874	The block will be executed I<after> the actual backend has been detected
		875	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		876	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		877	other initialisations - see the sources of L<AnyEvent::Strict> or
		878	L<AnyEvent::AIO> to see how this is used.
		879
		880	The most common usage is to create some global watchers, without forcing
		881	event module detection too early, for example, L<AnyEvent::AIO> creates
		882	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		883	avoid autodetecting the event module at load time.
		884
		885	If called in scalar or list context, then it creates and returns an object
		886	that automatically removes the callback again when it is destroyed (or
		887	C<undef> when the hook was immediately executed). See L<AnyEvent::AIO> for
		888	a case where this is useful.
		889
		890	Example: Create a watcher for the IO::AIO module and store it in
		891	C<$WATCHER>. Only do so after the event loop is initialised, though.
		892
		893	our WATCHER;
		894
		895	my $guard = AnyEvent::post_detect {
		896	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		897	};
		898
		899	# the ||= is important in case post_detect immediately runs the block,
		900	# as to not clobber the newly-created watcher. assigning both watcher and
		901	# post_detect guard to the same variable has the advantage of users being
		902	# able to just C<undef $WATCHER> if the watcher causes them grief.
		903
		904	$WATCHER ||= $guard;
		905
		906	=item @AnyEvent::post_detect
		907
		908	If there are any code references in this array (you can C<push> to it
		909	before or after loading AnyEvent), then they will called directly after
		910	the event loop has been chosen.
		911
		912	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		913	if it is defined then the event loop has already been detected, and the
		914	array will be ignored.
		915
		916	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		917	it,as it takes care of these details.
		918
		919	This variable is mainly useful for modules that can do something useful
		920	when AnyEvent is used and thus want to know when it is initialised, but do
		921	not need to even load it by default. This array provides the means to hook
		922	into AnyEvent passively, without loading it.
438		923
439	=back	924	=back
440		925
441	=head1 WHAT TO DO IN A MODULE	926	=head1 WHAT TO DO IN A MODULE
442		927
…		…
446	Be careful when you create watchers in the module body - AnyEvent will	931	Be careful when you create watchers in the module body - AnyEvent will
447	decide which event module to use as soon as the first method is called, so	932	decide which event module to use as soon as the first method is called, so
448	by calling AnyEvent in your module body you force the user of your module	933	by calling AnyEvent in your module body you force the user of your module
449	to load the event module first.	934	to load the event module first.
450		935
451	Never call C<< ->wait >> on a condition variable unless you I<know> that	936	Never call C<< ->recv >> on a condition variable unless you I<know> that
452	the C<< ->broadcast >> method has been called on it already. This is	937	the C<< ->send >> method has been called on it already. This is
453	because it will stall the whole program, and the whole point of using	938	because it will stall the whole program, and the whole point of using
454	events is to stay interactive.	939	events is to stay interactive.
455		940
456	It is fine, however, to call C<< ->wait >> when the user of your module	941	It is fine, however, to call C<< ->recv >> when the user of your module
457	requests it (i.e. if you create a http request object ad have a method	942	requests it (i.e. if you create a http request object ad have a method
458	called C<results> that returns the results, it should call C<< ->wait >>	943	called C<results> that returns the results, it should call C<< ->recv >>
459	freely, as the user of your module knows what she is doing. always).	944	freely, as the user of your module knows what she is doing. always).
460		945
461	=head1 WHAT TO DO IN THE MAIN PROGRAM	946	=head1 WHAT TO DO IN THE MAIN PROGRAM
462		947
463	There will always be a single main program - the only place that should	948	There will always be a single main program - the only place that should
…		…
465		950
466	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	951	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
467	do anything special (it does not need to be event-based) and let AnyEvent	952	do anything special (it does not need to be event-based) and let AnyEvent
468	decide which implementation to chose if some module relies on it.	953	decide which implementation to chose if some module relies on it.
469		954
470	If the main program relies on a specific event model. For example, in	955	If the main program relies on a specific event model - for example, in
471	Gtk2 programs you have to rely on the Glib module. You should load the	956	Gtk2 programs you have to rely on the Glib module - you should load the
472	event module before loading AnyEvent or any module that uses it: generally	957	event module before loading AnyEvent or any module that uses it: generally
473	speaking, you should load it as early as possible. The reason is that	958	speaking, you should load it as early as possible. The reason is that
474	modules might create watchers when they are loaded, and AnyEvent will	959	modules might create watchers when they are loaded, and AnyEvent will
475	decide on the event model to use as soon as it creates watchers, and it	960	decide on the event model to use as soon as it creates watchers, and it
476	might chose the wrong one unless you load the correct one yourself.	961	might chose the wrong one unless you load the correct one yourself.
477		962
478	You can chose to use a rather inefficient pure-perl implementation by	963	You can chose to use a pure-perl implementation by loading the
479	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	964	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
480	behaviour everywhere, but letting AnyEvent chose is generally better.	965	everywhere, but letting AnyEvent chose the model is generally better.
		966
		967	=head2 MAINLOOP EMULATION
		968
		969	Sometimes (often for short test scripts, or even standalone programs who
		970	only want to use AnyEvent), you do not want to run a specific event loop.
		971
		972	In that case, you can use a condition variable like this:
		973
		974	AnyEvent->condvar->recv;
		975
		976	This has the effect of entering the event loop and looping forever.
		977
		978	Note that usually your program has some exit condition, in which case
		979	it is better to use the "traditional" approach of storing a condition
		980	variable somewhere, waiting for it, and sending it when the program should
		981	exit cleanly.
		982
481		983
482	=head1 OTHER MODULES	984	=head1 OTHER MODULES
483		985
484	L<AnyEvent> itself comes with useful utility modules:	986	The following is a non-exhaustive list of additional modules that use
485		987	AnyEvent as a client and can therefore be mixed easily with other AnyEvent
486	To make it easier to do non-blocking IO the modules L<AnyEvent::Handle>	988	modules and other event loops in the same program. Some of the modules
487	and L<AnyEvent::Socket> are provided. L<AnyEvent::Handle> provides	989	come with AnyEvent, most are available via CPAN.
488	read and write buffers and manages watchers for reads and writes.
489	L<AnyEvent::Socket> provides means to do non-blocking connects.
490
491	Aside from those there are these modules that support AnyEvent (and use it
492	for non-blocking IO):
493		990
494	=over 4	991	=over 4
495		992
		993	=item L<AnyEvent::Util>
		994
		995	Contains various utility functions that replace often-used but blocking
		996	functions such as C<inet_aton> by event-/callback-based versions.
		997
		998	=item L<AnyEvent::Socket>
		999
		1000	Provides various utility functions for (internet protocol) sockets,
		1001	addresses and name resolution. Also functions to create non-blocking tcp
		1002	connections or tcp servers, with IPv6 and SRV record support and more.
		1003
		1004	=item L<AnyEvent::Handle>
		1005
		1006	Provide read and write buffers, manages watchers for reads and writes,
		1007	supports raw and formatted I/O, I/O queued and fully transparent and
		1008	non-blocking SSL/TLS (via L<AnyEvent::TLS>.
		1009
		1010	=item L<AnyEvent::DNS>
		1011
		1012	Provides rich asynchronous DNS resolver capabilities.
		1013
		1014	=item L<AnyEvent::HTTP>
		1015
		1016	A simple-to-use HTTP library that is capable of making a lot of concurrent
		1017	HTTP requests.
		1018
		1019	=item L<AnyEvent::HTTPD>
		1020
		1021	Provides a simple web application server framework.
		1022
496	=item L<AnyEvent::FastPing>	1023	=item L<AnyEvent::FastPing>
497		1024
		1025	The fastest ping in the west.
		1026
		1027	=item L<AnyEvent::DBI>
		1028
		1029	Executes L<DBI> requests asynchronously in a proxy process.
		1030
		1031	=item L<AnyEvent::AIO>
		1032
		1033	Truly asynchronous I/O, should be in the toolbox of every event
		1034	programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
		1035	together.
		1036
		1037	=item L<AnyEvent::BDB>
		1038
		1039	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
		1040	L<BDB> and AnyEvent together.
		1041
		1042	=item L<AnyEvent::GPSD>
		1043
		1044	A non-blocking interface to gpsd, a daemon delivering GPS information.
		1045
		1046	=item L<AnyEvent::IRC>
		1047
		1048	AnyEvent based IRC client module family (replacing the older Net::IRC3).
		1049
		1050	=item L<AnyEvent::XMPP>
		1051
		1052	AnyEvent based XMPP (Jabber protocol) module family (replacing the older
		1053	Net::XMPP2>.
		1054
		1055	=item L<AnyEvent::IGS>
		1056
		1057	A non-blocking interface to the Internet Go Server protocol (used by
		1058	L<App::IGS>).
		1059
498	=item L<Net::IRC3>	1060	=item L<Net::FCP>
499		1061
500	=item L<Net::XMPP2>	1062	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
		1063	of AnyEvent.
		1064
		1065	=item L<Event::ExecFlow>
		1066
		1067	High level API for event-based execution flow control.
		1068
		1069	=item L<Coro>
		1070
		1071	Has special support for AnyEvent via L<Coro::AnyEvent>.
501		1072
502	=back	1073	=back
503		1074
504	=cut	1075	=cut
505		1076
506	package AnyEvent;	1077	package AnyEvent;
507		1078
		1079	# basically a tuned-down version of common::sense
		1080	sub common_sense {
508	no warnings;	1081	# no warnings
509	use strict;	1082	${^WARNING_BITS} ^= ${^WARNING_BITS};
		1083	# use strict vars subs
		1084	$^H |= 0x00000600;
		1085	}
510		1086
		1087	BEGIN { AnyEvent::common_sense }
		1088
511	use Carp;	1089	use Carp ();
512		1090
513	our $VERSION = '3.3';	1091	our $VERSION = 4.881;
514	our $MODEL;	1092	our $MODEL;
515		1093
516	our $AUTOLOAD;	1094	our $AUTOLOAD;
517	our @ISA;	1095	our @ISA;
518		1096
519	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
520
521	our @REGISTRY;	1097	our @REGISTRY;
522		1098
		1099	our $WIN32;
		1100
		1101	our $VERBOSE;
		1102
		1103	BEGIN {
		1104	eval "sub WIN32(){ " . (($^O =~ /mswin32/i)*1) ." }";
		1105	eval "sub TAINT(){ " . (${^TAINT}*1) . " }";
		1106
		1107	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1108	if ${^TAINT};
		1109
		1110	$VERBOSE = $ENV{PERL_ANYEVENT_VERBOSE}*1;
		1111
		1112	}
		1113
		1114	our $MAX_SIGNAL_LATENCY = 10;
		1115
		1116	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		1117
		1118	{
		1119	my $idx;
		1120	$PROTOCOL{$_} = ++$idx
		1121	for reverse split /\s*,\s*/,
		1122	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		1123	}
		1124
523	my @models = (	1125	my @models = (
524	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
525	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
526	[EV:: => AnyEvent::Impl::EV::],	1126	[EV:: => AnyEvent::Impl::EV:: , 1],
527	[Event:: => AnyEvent::Impl::Event::],	1127	[Event:: => AnyEvent::Impl::Event::, 1],
528	[Glib:: => AnyEvent::Impl::Glib::],	1128	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl:: , 1],
		1129	# everything below here will not (normally) be autoprobed
		1130	# as the pureperl backend should work everywhere
		1131	# and is usually faster
		1132	[Glib:: => AnyEvent::Impl::Glib:: , 1], # becomes extremely slow with many watchers
		1133	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		1134	[Irssi:: => AnyEvent::Impl::Irssi::], # Irssi has a bogus "Event" package
529	[Tk:: => AnyEvent::Impl::Tk::],	1135	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		1136	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		1137	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
530	[Wx:: => AnyEvent::Impl::POE::],	1138	[Wx:: => AnyEvent::Impl::POE::],
531	[Prima:: => AnyEvent::Impl::POE::],	1139	[Prima:: => AnyEvent::Impl::POE::],
532	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1140	# IO::Async is just too broken - we would need workarounds for its
533	# everything below here will not be autoprobed as the pureperl backend should work everywhere	1141	# byzantine signal and broken child handling, among others.
534	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy	1142	# IO::Async is rather hard to detect, as it doesn't have any
		1143	# obvious default class.
535	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program	1144	# [0, IO::Async:: => AnyEvent::Impl::IOAsync::], # requires special main program
536	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza	1145	# [0, IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1146	# [0, IO::Async::Notifier:: => AnyEvent::Impl::IOAsync::], # requires special main program
537	);	1147	);
538		1148
539	our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);	1149	our %method = map +($_ => 1),
		1150	qw(io timer time now now_update signal child idle condvar one_event DESTROY);
		1151
		1152	our @post_detect;
		1153
		1154	sub post_detect(&) {
		1155	my ($cb) = @_;
		1156
		1157	if ($MODEL) {
		1158	$cb->();
		1159
		1160	undef
		1161	} else {
		1162	push @post_detect, $cb;
		1163
		1164	defined wantarray
		1165	? bless \$cb, "AnyEvent::Util::postdetect"
		1166	: ()
		1167	}
		1168	}
		1169
		1170	sub AnyEvent::Util::postdetect::DESTROY {
		1171	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		1172	}
540		1173
541	sub detect() {	1174	sub detect() {
542	unless ($MODEL) {	1175	unless ($MODEL) {
543	no strict 'refs';	1176	local $SIG{__DIE__};
544		1177
545	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	1178	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
546	my $model = "AnyEvent::Impl::$1";	1179	my $model = "AnyEvent::Impl::$1";
547	if (eval "require $model") {	1180	if (eval "require $model") {
548	$MODEL = $model;	1181	$MODEL = $model;
549	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	1182	warn "AnyEvent: loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.\n" if $VERBOSE >= 2;
550	} else {	1183	} else {
551	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;	1184	warn "AnyEvent: unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@" if $VERBOSE;
552	}	1185	}
553	}	1186	}
554		1187
555	# check for already loaded models	1188	# check for already loaded models
556	unless ($MODEL) {	1189	unless ($MODEL) {
557	for (@REGISTRY, @models) {	1190	for (@REGISTRY, @models) {
558	my ($package, $model) = @$_;	1191	my ($package, $model) = @$_;
559	if (${"$package\::VERSION"} > 0) {	1192	if (${"$package\::VERSION"} > 0) {
560	if (eval "require $model") {	1193	if (eval "require $model") {
561	$MODEL = $model;	1194	$MODEL = $model;
562	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;	1195	warn "AnyEvent: autodetected model '$model', using it.\n" if $VERBOSE >= 2;
563	last;	1196	last;
564	}	1197	}
565	}	1198	}
566	}	1199	}
567		1200
568	unless ($MODEL) {	1201	unless ($MODEL) {
569	# try to load a model	1202	# try to autoload a model
570
571	for (@REGISTRY, @models) {	1203	for (@REGISTRY, @models) {
572	my ($package, $model) = @$_;	1204	my ($package, $model, $autoload) = @$_;
		1205	if (
		1206	$autoload
573	if (eval "require $package"	1207	and eval "require $package"
574	and ${"$package\::VERSION"} > 0	1208	and ${"$package\::VERSION"} > 0
575	and eval "require $model") {	1209	and eval "require $model"
		1210	) {
576	$MODEL = $model;	1211	$MODEL = $model;
577	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;	1212	warn "AnyEvent: autoloaded model '$model', using it.\n" if $VERBOSE >= 2;
578	last;	1213	last;
579	}	1214	}
580	}	1215	}
581		1216
582	$MODEL	1217	$MODEL
583	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV (or Coro+EV), Event (or Coro+Event) or Glib.";	1218	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.\n";
584	}	1219	}
585	}	1220	}
586		1221
		1222	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		1223
587	unshift @ISA, $MODEL;	1224	unshift @ISA, $MODEL;
588	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	1225
		1226	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
		1227
		1228	(shift @post_detect)->() while @post_detect;
589	}	1229	}
590		1230
591	$MODEL	1231	$MODEL
592	}	1232	}
593		1233
594	sub AUTOLOAD {	1234	sub AUTOLOAD {
595	(my $func = $AUTOLOAD) =~ s/.*://;	1235	(my $func = $AUTOLOAD) =~ s/.*://;
596		1236
597	$method{$func}	1237	$method{$func}
598	or croak "$func: not a valid method for AnyEvent objects";	1238	or Carp::croak "$func: not a valid method for AnyEvent objects";
599		1239
600	detect unless $MODEL;	1240	detect unless $MODEL;
601		1241
602	my $class = shift;	1242	my $class = shift;
603	$class->$func (@_);	1243	$class->$func (@_);
604	}	1244	}
605		1245
		1246	# utility function to dup a filehandle. this is used by many backends
		1247	# to support binding more than one watcher per filehandle (they usually
		1248	# allow only one watcher per fd, so we dup it to get a different one).
		1249	sub _dupfh($$;$$) {
		1250	my ($poll, $fh, $r, $w) = @_;
		1251
		1252	# cygwin requires the fh mode to be matching, unix doesn't
		1253	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1254
		1255	open my $fh2, $mode, $fh
		1256	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1257
		1258	# we assume CLOEXEC is already set by perl in all important cases
		1259
		1260	($fh2, $rw)
		1261	}
		1262
606	package AnyEvent::Base;	1263	package AnyEvent::Base;
607		1264
		1265	# default implementations for many methods
		1266
		1267	sub _time {
		1268	# probe for availability of Time::HiRes
		1269	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1270	warn "AnyEvent: using Time::HiRes for sub-second timing accuracy.\n" if $VERBOSE >= 8;
		1271	*_time = \&Time::HiRes::time;
		1272	# if (eval "use POSIX (); (POSIX::times())...
		1273	} else {
		1274	warn "AnyEvent: using built-in time(), WARNING, no sub-second resolution!\n" if $VERBOSE;
		1275	*_time = sub { time }; # epic fail
		1276	}
		1277
		1278	&_time
		1279	}
		1280
		1281	sub time { _time }
		1282	sub now { _time }
		1283	sub now_update { }
		1284
608	# default implementation for ->condvar, ->wait, ->broadcast	1285	# default implementation for ->condvar
609		1286
610	sub condvar {	1287	sub condvar {
611	bless \my $flag, "AnyEvent::Base::CondVar"	1288	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
612	}
613
614	sub AnyEvent::Base::CondVar::broadcast {
615	${$_[0]}++;
616	}
617
618	sub AnyEvent::Base::CondVar::wait {
619	AnyEvent->one_event while !${$_[0]};
620	}	1289	}
621		1290
622	# default implementation for ->signal	1291	# default implementation for ->signal
623		1292
624	our %SIG_CB;	1293	our $HAVE_ASYNC_INTERRUPT;
625		1294
		1295	sub _have_async_interrupt() {
		1296	$HAVE_ASYNC_INTERRUPT = 1*(!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT}
		1297	&& eval "use Async::Interrupt 1.0 (); 1")
		1298	unless defined $HAVE_ASYNC_INTERRUPT;
		1299
		1300	$HAVE_ASYNC_INTERRUPT
		1301	}
		1302
		1303	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1304	our (%SIG_ASY, %SIG_ASY_W);
		1305	our ($SIG_COUNT, $SIG_TW);
		1306
		1307	sub _signal_exec {
		1308	$HAVE_ASYNC_INTERRUPT
		1309	? $SIGPIPE_R->drain
		1310	: sysread $SIGPIPE_R, my $dummy, 9;
		1311
		1312	while (%SIG_EV) {
		1313	for (keys %SIG_EV) {
		1314	delete $SIG_EV{$_};
		1315	$_->() for values %{ $SIG_CB{$_} || {} };
		1316	}
		1317	}
		1318	}
		1319
		1320	# install a dummy wakeup watcher to reduce signal catching latency
		1321	sub _sig_add() {
		1322	unless ($SIG_COUNT++) {
		1323	# try to align timer on a full-second boundary, if possible
		1324	my $NOW = AnyEvent->now;
		1325
		1326	$SIG_TW = AnyEvent->timer (
		1327	after => $MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1328	interval => $MAX_SIGNAL_LATENCY,
		1329	cb => sub { }, # just for the PERL_ASYNC_CHECK
		1330	);
		1331	}
		1332	}
		1333
		1334	sub _sig_del {
		1335	undef $SIG_TW
		1336	unless --$SIG_COUNT;
		1337	}
		1338
		1339	our %SIGNAME2NUM;
		1340	our @SIGNUM2NAME;
		1341	our $_sig_name_init; $_sig_name_init = sub {
		1342	undef $_sig_name_init;
		1343
		1344	if (_have_async_interrupt) {
		1345	*sig2num = \&Async::Interrupt::sig2num;
		1346	*sig2name = \&Async::Interrupt::sig2name;
		1347	} else {
		1348	require Config;
		1349
		1350	@SIGNAME2NUM{ split ' ', $Config::Config{sig_name} }
		1351	= split ' ', $Config::Config{sig_num};
		1352	@SIGNUM2NAME[values %SIGNAME2NUM] = keys %SIGNAME2NUM;
		1353
		1354	*sig2num = sub($) {
		1355	$_[0] > 0 ? shift : $SIGNAME2NUM{+shift}
		1356	};
		1357	*sig2name = sub ($) {
		1358	$_[0] > 0 ? $SIGNUM2NAME[+shift] : shift
		1359	};
		1360	}
		1361	};
		1362
		1363	sub sig2num ($) { &$_sig_name_init; &sig2num }
		1364	sub sig2name($) { &$_sig_name_init; &sig2name }
		1365
626	sub signal {	1366	sub _signal {
627	my (undef, %arg) = @_;	1367	my (undef, %arg) = @_;
628		1368
629	my $signal = uc $arg{signal}	1369	my $signal = uc $arg{signal}
630	or Carp::croak "required option 'signal' is missing";	1370	or Carp::croak "required option 'signal' is missing";
631		1371
		1372	if ($HAVE_ASYNC_INTERRUPT) {
		1373	# async::interrupt
		1374
		1375	$signal = sig2num $signal;
632	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1376	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1377
		1378	$SIG_ASY{$signal} ||= new Async::Interrupt
		1379	cb => sub { undef $SIG_EV{$signal} },
		1380	signal => $signal,
		1381	pipe => [$SIGPIPE_R->filenos],
		1382	pipe_autodrain => 0,
		1383	;
		1384
		1385	} else {
		1386	# pure perl
		1387
		1388	# AE::Util has been loaded in signal
		1389	$signal = sig2name $signal;
		1390	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1391
633	$SIG{$signal} ||= sub {	1392	$SIG{$signal} ||= sub {
634	$_->() for values %{ $SIG_CB{$signal} || {} };	1393	local $!;
		1394	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1395	undef $SIG_EV{$signal};
		1396	};
		1397
		1398	# can't do signal processing without introducing races in pure perl,
		1399	# so limit the signal latency.
		1400	_sig_add;
635	};	1401	}
636		1402
637	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1403	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
638	}	1404	}
639		1405
		1406	sub signal {
		1407	# probe for availability of Async::Interrupt
		1408	if (_have_async_interrupt) {
		1409	warn "AnyEvent: using Async::Interrupt for race-free signal handling.\n" if $VERBOSE >= 8;
		1410
		1411	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1412	$SIG_IO = AnyEvent->io (fh => $SIGPIPE_R->fileno, poll => "r", cb => \&_signal_exec);
		1413
		1414	} else {
		1415	warn "AnyEvent: using emulated perl signal handling with latency timer.\n" if $VERBOSE >= 8;
		1416
		1417	require Fcntl;
		1418
		1419	if (AnyEvent::WIN32) {
		1420	require AnyEvent::Util;
		1421
		1422	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1423	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R) if $SIGPIPE_R;
		1424	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W) if $SIGPIPE_W; # just in case
		1425	} else {
		1426	pipe $SIGPIPE_R, $SIGPIPE_W;
		1427	fcntl $SIGPIPE_R, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_R;
		1428	fcntl $SIGPIPE_W, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_W; # just in case
		1429
		1430	# not strictly required, as $^F is normally 2, but let's make sure...
		1431	fcntl $SIGPIPE_R, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1432	fcntl $SIGPIPE_W, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1433	}
		1434
		1435	$SIGPIPE_R
		1436	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1437
		1438	$SIG_IO = AnyEvent->io (fh => $SIGPIPE_R, poll => "r", cb => \&_signal_exec);
		1439	}
		1440
		1441	*signal = \&_signal;
		1442	&signal
		1443	}
		1444
640	sub AnyEvent::Base::Signal::DESTROY {	1445	sub AnyEvent::Base::signal::DESTROY {
641	my ($signal, $cb) = @{$_[0]};	1446	my ($signal, $cb) = @{$_[0]};
642		1447
		1448	_sig_del;
		1449
643	delete $SIG_CB{$signal}{$cb};	1450	delete $SIG_CB{$signal}{$cb};
644		1451
645	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };	1452	$HAVE_ASYNC_INTERRUPT
		1453	? delete $SIG_ASY{$signal}
		1454	: # delete doesn't work with older perls - they then
		1455	# print weird messages, or just unconditionally exit
		1456	# instead of getting the default action.
		1457	undef $SIG{$signal}
		1458	unless keys %{ $SIG_CB{$signal} };
646	}	1459	}
647		1460
648	# default implementation for ->child	1461	# default implementation for ->child
649		1462
650	our %PID_CB;	1463	our %PID_CB;
651	our $CHLD_W;	1464	our $CHLD_W;
652	our $CHLD_DELAY_W;	1465	our $CHLD_DELAY_W;
653	our $PID_IDLE;
654	our $WNOHANG;	1466	our $WNOHANG;
655		1467
656	sub _child_wait {	1468	sub _emit_childstatus($$) {
657	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1469	my (undef, $rpid, $rstatus) = @_;
		1470
		1471	$_->($rpid, $rstatus)
658	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1472	for values %{ $PID_CB{$rpid} || {} },
659	(values %{ $PID_CB{0} || {} });	1473	values %{ $PID_CB{0} || {} };
660	}
661
662	undef $PID_IDLE;
663	}	1474	}
664		1475
665	sub _sigchld {	1476	sub _sigchld {
666	# make sure we deliver these changes "synchronous" with the event loop.	1477	my $pid;
667	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {	1478
668	undef $CHLD_DELAY_W;	1479	AnyEvent->_emit_childstatus ($pid, $?)
669	&_child_wait;	1480	while ($pid = waitpid -1, $WNOHANG) > 0;
670	});
671	}	1481	}
672		1482
673	sub child {	1483	sub child {
674	my (undef, %arg) = @_;	1484	my (undef, %arg) = @_;
675		1485
676	defined (my $pid = $arg{pid} + 0)	1486	defined (my $pid = $arg{pid} + 0)
677	or Carp::croak "required option 'pid' is missing";	1487	or Carp::croak "required option 'pid' is missing";
678		1488
679	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1489	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
680		1490
681	unless ($WNOHANG) {	1491	# WNOHANG is almost cetrainly 1 everywhere
682	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;	1492	$WNOHANG ||= $^O =~ /^(?:openbsd|netbsd|linux|freebsd|cygwin|MSWin32)$/
683	}	1493	? 1
		1494	: eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
684		1495
685	unless ($CHLD_W) {	1496	unless ($CHLD_W) {
686	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1497	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
687	# child could be a zombie already, so make at least one round	1498	# child could be a zombie already, so make at least one round
688	&_sigchld;	1499	&_sigchld;
689	}	1500	}
690		1501
691	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	1502	bless [$pid, $arg{cb}], "AnyEvent::Base::child"
692	}	1503	}
693		1504
694	sub AnyEvent::Base::Child::DESTROY {	1505	sub AnyEvent::Base::child::DESTROY {
695	my ($pid, $cb) = @{$_[0]};	1506	my ($pid, $cb) = @{$_[0]};
696		1507
697	delete $PID_CB{$pid}{$cb};	1508	delete $PID_CB{$pid}{$cb};
698	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1509	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
699		1510
700	undef $CHLD_W unless keys %PID_CB;	1511	undef $CHLD_W unless keys %PID_CB;
701	}	1512	}
		1513
		1514	# idle emulation is done by simply using a timer, regardless
		1515	# of whether the process is idle or not, and not letting
		1516	# the callback use more than 50% of the time.
		1517	sub idle {
		1518	my (undef, %arg) = @_;
		1519
		1520	my ($cb, $w, $rcb) = $arg{cb};
		1521
		1522	$rcb = sub {
		1523	if ($cb) {
		1524	$w = _time;
		1525	&$cb;
		1526	$w = _time - $w;
		1527
		1528	# never use more then 50% of the time for the idle watcher,
		1529	# within some limits
		1530	$w = 0.0001 if $w < 0.0001;
		1531	$w = 5 if $w > 5;
		1532
		1533	$w = AnyEvent->timer (after => $w, cb => $rcb);
		1534	} else {
		1535	# clean up...
		1536	undef $w;
		1537	undef $rcb;
		1538	}
		1539	};
		1540
		1541	$w = AnyEvent->timer (after => 0.05, cb => $rcb);
		1542
		1543	bless \\$cb, "AnyEvent::Base::idle"
		1544	}
		1545
		1546	sub AnyEvent::Base::idle::DESTROY {
		1547	undef $${$_[0]};
		1548	}
		1549
		1550	package AnyEvent::CondVar;
		1551
		1552	our @ISA = AnyEvent::CondVar::Base::;
		1553
		1554	package AnyEvent::CondVar::Base;
		1555
		1556	#use overload
		1557	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1558	# fallback => 1;
		1559
		1560	# save 300+ kilobytes by dirtily hardcoding overloading
		1561	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1562	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1563	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1564	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1565
		1566	our $WAITING;
		1567
		1568	sub _send {
		1569	# nop
		1570	}
		1571
		1572	sub send {
		1573	my $cv = shift;
		1574	$cv->{_ae_sent} = [@_];
		1575	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1576	$cv->_send;
		1577	}
		1578
		1579	sub croak {
		1580	$_[0]{_ae_croak} = $_[1];
		1581	$_[0]->send;
		1582	}
		1583
		1584	sub ready {
		1585	$_[0]{_ae_sent}
		1586	}
		1587
		1588	sub _wait {
		1589	$WAITING
		1590	and !$_[0]{_ae_sent}
		1591	and Carp::croak "AnyEvent::CondVar: recursive blocking wait detected";
		1592
		1593	local $WAITING = 1;
		1594	AnyEvent->one_event while !$_[0]{_ae_sent};
		1595	}
		1596
		1597	sub recv {
		1598	$_[0]->_wait;
		1599
		1600	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
		1601	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
		1602	}
		1603
		1604	sub cb {
		1605	$_[0]{_ae_cb} = $_[1] if @_ > 1;
		1606	$_[0]{_ae_cb}
		1607	}
		1608
		1609	sub begin {
		1610	++$_[0]{_ae_counter};
		1611	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
		1612	}
		1613
		1614	sub end {
		1615	return if --$_[0]{_ae_counter};
		1616	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		1617	}
		1618
		1619	# undocumented/compatibility with pre-3.4
		1620	*broadcast = \&send;
		1621	*wait = \&_wait;
		1622
		1623	=head1 ERROR AND EXCEPTION HANDLING
		1624
		1625	In general, AnyEvent does not do any error handling - it relies on the
		1626	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1627	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1628	checking of all AnyEvent methods, however, which is highly useful during
		1629	development.
		1630
		1631	As for exception handling (i.e. runtime errors and exceptions thrown while
		1632	executing a callback), this is not only highly event-loop specific, but
		1633	also not in any way wrapped by this module, as this is the job of the main
		1634	program.
		1635
		1636	The pure perl event loop simply re-throws the exception (usually
		1637	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1638	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1639	so on.
		1640
		1641	=head1 ENVIRONMENT VARIABLES
		1642
		1643	The following environment variables are used by this module or its
		1644	submodules.
		1645
		1646	Note that AnyEvent will remove I<all> environment variables starting with
		1647	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		1648	enabled.
		1649
		1650	=over 4
		1651
		1652	=item C<PERL_ANYEVENT_VERBOSE>
		1653
		1654	By default, AnyEvent will be completely silent except in fatal
		1655	conditions. You can set this environment variable to make AnyEvent more
		1656	talkative.
		1657
		1658	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1659	conditions, such as not being able to load the event model specified by
		1660	C<PERL_ANYEVENT_MODEL>.
		1661
		1662	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1663	model it chooses.
		1664
		1665	When set to C<8> or higher, then AnyEvent will report extra information on
		1666	which optional modules it loads and how it implements certain features.
		1667
		1668	=item C<PERL_ANYEVENT_STRICT>
		1669
		1670	AnyEvent does not do much argument checking by default, as thorough
		1671	argument checking is very costly. Setting this variable to a true value
		1672	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1673	check the arguments passed to most method calls. If it finds any problems,
		1674	it will croak.
		1675
		1676	In other words, enables "strict" mode.
		1677
		1678	Unlike C<use strict> (or it's modern cousin, C<< use L<common::sense>
		1679	>>, it is definitely recommended to keep it off in production. Keeping
		1680	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		1681	can be very useful, however.
		1682
		1683	=item C<PERL_ANYEVENT_MODEL>
		1684
		1685	This can be used to specify the event model to be used by AnyEvent, before
		1686	auto detection and -probing kicks in. It must be a string consisting
		1687	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1688	and the resulting module name is loaded and if the load was successful,
		1689	used as event model. If it fails to load AnyEvent will proceed with
		1690	auto detection and -probing.
		1691
		1692	This functionality might change in future versions.
		1693
		1694	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1695	could start your program like this:
		1696
		1697	PERL_ANYEVENT_MODEL=Perl perl ...
		1698
		1699	=item C<PERL_ANYEVENT_PROTOCOLS>
		1700
		1701	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1702	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1703	of auto probing).
		1704
		1705	Must be set to a comma-separated list of protocols or address families,
		1706	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1707	used, and preference will be given to protocols mentioned earlier in the
		1708	list.
		1709
		1710	This variable can effectively be used for denial-of-service attacks
		1711	against local programs (e.g. when setuid), although the impact is likely
		1712	small, as the program has to handle conenction and other failures anyways.
		1713
		1714	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1715	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1716	- only support IPv4, never try to resolve or contact IPv6
		1717	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1718	IPv6, but prefer IPv6 over IPv4.
		1719
		1720	=item C<PERL_ANYEVENT_EDNS0>
		1721
		1722	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1723	for DNS. This extension is generally useful to reduce DNS traffic, but
		1724	some (broken) firewalls drop such DNS packets, which is why it is off by
		1725	default.
		1726
		1727	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1728	EDNS0 in its DNS requests.
		1729
		1730	=item C<PERL_ANYEVENT_MAX_FORKS>
		1731
		1732	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1733	will create in parallel.
		1734
		1735	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		1736
		1737	The default value for the C<max_outstanding> parameter for the default DNS
		1738	resolver - this is the maximum number of parallel DNS requests that are
		1739	sent to the DNS server.
		1740
		1741	=item C<PERL_ANYEVENT_RESOLV_CONF>
		1742
		1743	The file to use instead of F</etc/resolv.conf> (or OS-specific
		1744	configuration) in the default resolver. When set to the empty string, no
		1745	default config will be used.
		1746
		1747	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		1748
		1749	When neither C<ca_file> nor C<ca_path> was specified during
		1750	L<AnyEvent::TLS> context creation, and either of these environment
		1751	variables exist, they will be used to specify CA certificate locations
		1752	instead of a system-dependent default.
		1753
		1754	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		1755
		1756	When these are set to C<1>, then the respective modules are not
		1757	loaded. Mostly good for testing AnyEvent itself.
		1758
		1759	=back
702		1760
703	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1761	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
704		1762
705	This is an advanced topic that you do not normally need to use AnyEvent in	1763	This is an advanced topic that you do not normally need to use AnyEvent in
706	a module. This section is only of use to event loop authors who want to	1764	a module. This section is only of use to event loop authors who want to
…		…
740		1798
741	I<rxvt-unicode> also cheats a bit by not providing blocking access to	1799	I<rxvt-unicode> also cheats a bit by not providing blocking access to
742	condition variables: code blocking while waiting for a condition will	1800	condition variables: code blocking while waiting for a condition will
743	C<die>. This still works with most modules/usages, and blocking calls must	1801	C<die>. This still works with most modules/usages, and blocking calls must
744	not be done in an interactive application, so it makes sense.	1802	not be done in an interactive application, so it makes sense.
745
746	=head1 ENVIRONMENT VARIABLES
747
748	The following environment variables are used by this module:
749
750	=over 4
751
752	=item C<PERL_ANYEVENT_VERBOSE>
753
754	By default, AnyEvent will be completely silent except in fatal
755	conditions. You can set this environment variable to make AnyEvent more
756	talkative.
757
758	When set to C<1> or higher, causes AnyEvent to warn about unexpected
759	conditions, such as not being able to load the event model specified by
760	C<PERL_ANYEVENT_MODEL>.
761
762	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
763	model it chooses.
764
765	=item C<PERL_ANYEVENT_MODEL>
766
767	This can be used to specify the event model to be used by AnyEvent, before
768	autodetection and -probing kicks in. It must be a string consisting
769	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
770	and the resulting module name is loaded and if the load was successful,
771	used as event model. If it fails to load AnyEvent will proceed with
772	autodetection and -probing.
773
774	This functionality might change in future versions.
775
776	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
777	could start your program like this:
778
779	PERL_ANYEVENT_MODEL=Perl perl ...
780
781	=back
782		1803
783	=head1 EXAMPLE PROGRAM	1804	=head1 EXAMPLE PROGRAM
784		1805
785	The following program uses an I/O watcher to read data from STDIN, a timer	1806	The following program uses an I/O watcher to read data from STDIN, a timer
786	to display a message once per second, and a condition variable to quit the	1807	to display a message once per second, and a condition variable to quit the
…		…
795	poll => 'r',	1816	poll => 'r',
796	cb => sub {	1817	cb => sub {
797	warn "io event <$_[0]>\n"; # will always output <r>	1818	warn "io event <$_[0]>\n"; # will always output <r>
798	chomp (my $input = <STDIN>); # read a line	1819	chomp (my $input = <STDIN>); # read a line
799	warn "read: $input\n"; # output what has been read	1820	warn "read: $input\n"; # output what has been read
800	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	1821	$cv->send if $input =~ /^q/i; # quit program if /^q/i
801	},	1822	},
802	);	1823	);
803		1824
804	my $time_watcher; # can only be used once	1825	my $time_watcher; # can only be used once
805		1826
…		…
810	});	1831	});
811	}	1832	}
812		1833
813	new_timer; # create first timer	1834	new_timer; # create first timer
814		1835
815	$cv->wait; # wait until user enters /^q/i	1836	$cv->recv; # wait until user enters /^q/i
816		1837
817	=head1 REAL-WORLD EXAMPLE	1838	=head1 REAL-WORLD EXAMPLE
818		1839
819	Consider the L<Net::FCP> module. It features (among others) the following	1840	Consider the L<Net::FCP> module. It features (among others) the following
820	API calls, which are to freenet what HTTP GET requests are to http:	1841	API calls, which are to freenet what HTTP GET requests are to http:
…		…
870	syswrite $txn->{fh}, $txn->{request}	1891	syswrite $txn->{fh}, $txn->{request}
871	or die "connection or write error";	1892	or die "connection or write error";
872	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	1893	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
873		1894
874	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	1895	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
875	result and signals any possible waiters that the request ahs finished:	1896	result and signals any possible waiters that the request has finished:
876		1897
877	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	1898	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
878		1899
879	if (end-of-file or data complete) {	1900	if (end-of-file or data complete) {
880	$txn->{result} = $txn->{buf};	1901	$txn->{result} = $txn->{buf};
881	$txn->{finished}->broadcast;	1902	$txn->{finished}->send;
882	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	1903	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
883	}	1904	}
884		1905
885	The C<result> method, finally, just waits for the finished signal (if the	1906	The C<result> method, finally, just waits for the finished signal (if the
886	request was already finished, it doesn't wait, of course, and returns the	1907	request was already finished, it doesn't wait, of course, and returns the
887	data:	1908	data:
888		1909
889	$txn->{finished}->wait;	1910	$txn->{finished}->recv;
890	return $txn->{result};	1911	return $txn->{result};
891		1912
892	The actual code goes further and collects all errors (C<die>s, exceptions)	1913	The actual code goes further and collects all errors (C<die>s, exceptions)
893	that occured during request processing. The C<result> method detects	1914	that occurred during request processing. The C<result> method detects
894	whether an exception as thrown (it is stored inside the $txn object)	1915	whether an exception as thrown (it is stored inside the $txn object)
895	and just throws the exception, which means connection errors and other	1916	and just throws the exception, which means connection errors and other
896	problems get reported tot he code that tries to use the result, not in a	1917	problems get reported tot he code that tries to use the result, not in a
897	random callback.	1918	random callback.
898		1919
…		…
929		1950
930	my $quit = AnyEvent->condvar;	1951	my $quit = AnyEvent->condvar;
931		1952
932	$fcp->txn_client_get ($url)->cb (sub {	1953	$fcp->txn_client_get ($url)->cb (sub {
933	...	1954	...
934	$quit->broadcast;	1955	$quit->send;
935	});	1956	});
936		1957
937	$quit->wait;	1958	$quit->recv;
938		1959
939		1960
940	=head1 BENCHMARKS	1961	=head1 BENCHMARKS
941		1962
942	To give you an idea of the performance and overheads that AnyEvent adds	1963	To give you an idea of the performance and overheads that AnyEvent adds
…		…
944	of various event loops I prepared some benchmarks.	1965	of various event loops I prepared some benchmarks.
945		1966
946	=head2 BENCHMARKING ANYEVENT OVERHEAD	1967	=head2 BENCHMARKING ANYEVENT OVERHEAD
947		1968
948	Here is a benchmark of various supported event models used natively and	1969	Here is a benchmark of various supported event models used natively and
949	through anyevent. The benchmark creates a lot of timers (with a zero	1970	through AnyEvent. The benchmark creates a lot of timers (with a zero
950	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,	1971	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
951	which it is), lets them fire exactly once and destroys them again.	1972	which it is), lets them fire exactly once and destroys them again.
952		1973
953	Source code for this benchmark is found as F<eg/bench> in the AnyEvent	1974	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
954	distribution.	1975	distribution.
…		…
971	all watchers, to avoid adding memory overhead. That means closure creation	1992	all watchers, to avoid adding memory overhead. That means closure creation
972	and memory usage is not included in the figures.	1993	and memory usage is not included in the figures.
973		1994
974	I<invoke> is the time, in microseconds, used to invoke a simple	1995	I<invoke> is the time, in microseconds, used to invoke a simple
975	callback. The callback simply counts down a Perl variable and after it was	1996	callback. The callback simply counts down a Perl variable and after it was
976	invoked "watcher" times, it would C<< ->broadcast >> a condvar once to	1997	invoked "watcher" times, it would C<< ->send >> a condvar once to
977	signal the end of this phase.	1998	signal the end of this phase.
978		1999
979	I<destroy> is the time, in microseconds, that it takes to destroy a single	2000	I<destroy> is the time, in microseconds, that it takes to destroy a single
980	watcher.	2001	watcher.
981		2002
982	=head3 Results	2003	=head3 Results
983		2004
984	name watchers bytes create invoke destroy comment	2005	name watchers bytes create invoke destroy comment
985	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	2006	EV/EV 400000 224 0.47 0.35 0.27 EV native interface
986	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	2007	EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers
987	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	2008	CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal
988	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	2009	Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation
989	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	2010	Event/Event 16000 517 32.20 31.80 0.81 Event native interface
990	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers	2011	Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers
		2012	IOAsync/Any 16000 989 38.10 32.77 11.13 via IO::Async::Loop::IO_Poll
		2013	IOAsync/Any 16000 990 37.59 29.50 10.61 via IO::Async::Loop::Epoll
991	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	2014	Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour
992	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	2015	Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers
993	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	2016	POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event
994	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	2017	POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select
995		2018
996	=head3 Discussion	2019	=head3 Discussion
997		2020
998	The benchmark does I<not> measure scalability of the event loop very	2021	The benchmark does I<not> measure scalability of the event loop very
999	well. For example, a select-based event loop (such as the pure perl one)	2022	well. For example, a select-based event loop (such as the pure perl one)
…		…
1024	performance becomes really bad with lots of file descriptors (and few of	2047	performance becomes really bad with lots of file descriptors (and few of
1025	them active), of course, but this was not subject of this benchmark.	2048	them active), of course, but this was not subject of this benchmark.
1026		2049
1027	The C<Event> module has a relatively high setup and callback invocation	2050	The C<Event> module has a relatively high setup and callback invocation
1028	cost, but overall scores in on the third place.	2051	cost, but overall scores in on the third place.
		2052
		2053	C<IO::Async> performs admirably well, about on par with C<Event>, even
		2054	when using its pure perl backend.
1029		2055
1030	C<Glib>'s memory usage is quite a bit higher, but it features a	2056	C<Glib>'s memory usage is quite a bit higher, but it features a
1031	faster callback invocation and overall ends up in the same class as	2057	faster callback invocation and overall ends up in the same class as
1032	C<Event>. However, Glib scales extremely badly, doubling the number of	2058	C<Event>. However, Glib scales extremely badly, doubling the number of
1033	watchers increases the processing time by more than a factor of four,	2059	watchers increases the processing time by more than a factor of four,
…		…
1041	file descriptor is dup()ed for each watcher. This shows that the dup()	2067	file descriptor is dup()ed for each watcher. This shows that the dup()
1042	employed by some adaptors is not a big performance issue (it does incur a	2068	employed by some adaptors is not a big performance issue (it does incur a
1043	hidden memory cost inside the kernel which is not reflected in the figures	2069	hidden memory cost inside the kernel which is not reflected in the figures
1044	above).	2070	above).
1045		2071
1046	C<POE>, regardless of underlying event loop (whether using its pure	2072	C<POE>, regardless of underlying event loop (whether using its pure perl
1047	perl select-based backend or the Event module, the POE-EV backend	2073	select-based backend or the Event module, the POE-EV backend couldn't
1048	couldn't be tested because it wasn't working) shows abysmal performance	2074	be tested because it wasn't working) shows abysmal performance and
1049	and memory usage: Watchers use almost 30 times as much memory as	2075	memory usage with AnyEvent: Watchers use almost 30 times as much memory
1050	EV watchers, and 10 times as much memory as Event (the high memory	2076	as EV watchers, and 10 times as much memory as Event (the high memory
1051	requirements are caused by requiring a session for each watcher). Watcher	2077	requirements are caused by requiring a session for each watcher). Watcher
1052	invocation speed is almost 900 times slower than with AnyEvent's pure perl	2078	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		2079	implementation.
		2080
1053	implementation. The design of the POE adaptor class in AnyEvent can not	2081	The design of the POE adaptor class in AnyEvent can not really account
1054	really account for this, as session creation overhead is small compared	2082	for the performance issues, though, as session creation overhead is
1055	to execution of the state machine, which is coded pretty optimally within	2083	small compared to execution of the state machine, which is coded pretty
1056	L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow.	2084	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		2085	using multiple sessions is not a good approach, especially regarding
		2086	memory usage, even the author of POE could not come up with a faster
		2087	design).
1057		2088
1058	=head3 Summary	2089	=head3 Summary
1059		2090
1060	=over 4	2091	=over 4
1061		2092
…		…
1072		2103
1073	=back	2104	=back
1074		2105
1075	=head2 BENCHMARKING THE LARGE SERVER CASE	2106	=head2 BENCHMARKING THE LARGE SERVER CASE
1076		2107
1077	This benchmark atcually benchmarks the event loop itself. It works by	2108	This benchmark actually benchmarks the event loop itself. It works by
1078	creating a number of "servers": each server consists of a socketpair, a	2109	creating a number of "servers": each server consists of a socket pair, a
1079	timeout watcher that gets reset on activity (but never fires), and an I/O	2110	timeout watcher that gets reset on activity (but never fires), and an I/O
1080	watcher waiting for input on one side of the socket. Each time the socket	2111	watcher waiting for input on one side of the socket. Each time the socket
1081	watcher reads a byte it will write that byte to a random other "server".	2112	watcher reads a byte it will write that byte to a random other "server".
1082		2113
1083	The effect is that there will be a lot of I/O watchers, only part of which	2114	The effect is that there will be a lot of I/O watchers, only part of which
1084	are active at any one point (so there is a constant number of active	2115	are active at any one point (so there is a constant number of active
1085	fds for each loop iterstaion, but which fds these are is random). The	2116	fds for each loop iteration, but which fds these are is random). The
1086	timeout is reset each time something is read because that reflects how	2117	timeout is reset each time something is read because that reflects how
1087	most timeouts work (and puts extra pressure on the event loops).	2118	most timeouts work (and puts extra pressure on the event loops).
1088		2119
1089	In this benchmark, we use 10000 socketpairs (20000 sockets), of which 100	2120	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
1090	(1%) are active. This mirrors the activity of large servers with many	2121	(1%) are active. This mirrors the activity of large servers with many
1091	connections, most of which are idle at any one point in time.	2122	connections, most of which are idle at any one point in time.
1092		2123
1093	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent	2124	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
1094	distribution.	2125	distribution.
…		…
1096	=head3 Explanation of the columns	2127	=head3 Explanation of the columns
1097		2128
1098	I<sockets> is the number of sockets, and twice the number of "servers" (as	2129	I<sockets> is the number of sockets, and twice the number of "servers" (as
1099	each server has a read and write socket end).	2130	each server has a read and write socket end).
1100		2131
1101	I<create> is the time it takes to create a socketpair (which is	2132	I<create> is the time it takes to create a socket pair (which is
1102	nontrivial) and two watchers: an I/O watcher and a timeout watcher.	2133	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
1103		2134
1104	I<request>, the most important value, is the time it takes to handle a	2135	I<request>, the most important value, is the time it takes to handle a
1105	single "request", that is, reading the token from the pipe and forwarding	2136	single "request", that is, reading the token from the pipe and forwarding
1106	it to another server. This includes deleting the old timeout and creating	2137	it to another server. This includes deleting the old timeout and creating
1107	a new one that moves the timeout into the future.	2138	a new one that moves the timeout into the future.
1108		2139
1109	=head3 Results	2140	=head3 Results
1110		2141
1111	name sockets create request	2142	name sockets create request
1112	EV 20000 69.01 11.16	2143	EV 20000 69.01 11.16
1113	Perl 20000 73.32 35.87	2144	Perl 20000 73.32 35.87
		2145	IOAsync 20000 157.00 98.14 epoll
		2146	IOAsync 20000 159.31 616.06 poll
1114	Event 20000 212.62 257.32	2147	Event 20000 212.62 257.32
1115	Glib 20000 651.16 1896.30	2148	Glib 20000 651.16 1896.30
1116	POE 20000 349.67 12317.24 uses POE::Loop::Event	2149	POE 20000 349.67 12317.24 uses POE::Loop::Event
1117		2150
1118	=head3 Discussion	2151	=head3 Discussion
1119		2152
1120	This benchmark I<does> measure scalability and overall performance of the	2153	This benchmark I<does> measure scalability and overall performance of the
1121	particular event loop.	2154	particular event loop.
…		…
1123	EV is again fastest. Since it is using epoll on my system, the setup time	2156	EV is again fastest. Since it is using epoll on my system, the setup time
1124	is relatively high, though.	2157	is relatively high, though.
1125		2158
1126	Perl surprisingly comes second. It is much faster than the C-based event	2159	Perl surprisingly comes second. It is much faster than the C-based event
1127	loops Event and Glib.	2160	loops Event and Glib.
		2161
		2162	IO::Async performs very well when using its epoll backend, and still quite
		2163	good compared to Glib when using its pure perl backend.
1128		2164
1129	Event suffers from high setup time as well (look at its code and you will	2165	Event suffers from high setup time as well (look at its code and you will
1130	understand why). Callback invocation also has a high overhead compared to	2166	understand why). Callback invocation also has a high overhead compared to
1131	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event	2167	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
1132	uses select or poll in basically all documented configurations.	2168	uses select or poll in basically all documented configurations.
…		…
1140		2176
1141	=head3 Summary	2177	=head3 Summary
1142		2178
1143	=over 4	2179	=over 4
1144		2180
1145	=item * The pure perl implementation performs extremely well, considering	2181	=item * The pure perl implementation performs extremely well.
1146	that it uses select.
1147		2182
1148	=item * Avoid Glib or POE in large projects where performance matters.	2183	=item * Avoid Glib or POE in large projects where performance matters.
1149		2184
1150	=back	2185	=back
1151		2186
…		…
1180	speed most when you have lots of watchers, not when you only have a few of	2215	speed most when you have lots of watchers, not when you only have a few of
1181	them).	2216	them).
1182		2217
1183	EV is again fastest.	2218	EV is again fastest.
1184		2219
1185	The C-based event loops Event and Glib come in second this time, as the	2220	Perl again comes second. It is noticeably faster than the C-based event
1186	overhead of running an iteration is much smaller in C than in Perl (little	2221	loops Event and Glib, although the difference is too small to really
1187	code to execute in the inner loop, and perl's function calling overhead is	2222	matter.
1188	high, and updating all the data structures is costly).
1189
1190	The pure perl event loop is much slower, but still competitive.
1191		2223
1192	POE also performs much better in this case, but is is still far behind the	2224	POE also performs much better in this case, but is is still far behind the
1193	others.	2225	others.
1194		2226
1195	=head3 Summary	2227	=head3 Summary
…		…
1199	=item * C-based event loops perform very well with small number of	2231	=item * C-based event loops perform very well with small number of
1200	watchers, as the management overhead dominates.	2232	watchers, as the management overhead dominates.
1201		2233
1202	=back	2234	=back
1203		2235
		2236	=head2 THE IO::Lambda BENCHMARK
		2237
		2238	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2239	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2240	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2241	shouldn't come as a surprise to anybody). As such, the benchmark is
		2242	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2243	very optimal. But how would AnyEvent compare when used without the extra
		2244	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2245
		2246	The benchmark itself creates an echo-server, and then, for 500 times,
		2247	connects to the echo server, sends a line, waits for the reply, and then
		2248	creates the next connection. This is a rather bad benchmark, as it doesn't
		2249	test the efficiency of the framework or much non-blocking I/O, but it is a
		2250	benchmark nevertheless.
		2251
		2252	name runtime
		2253	Lambda/select 0.330 sec
		2254	+ optimized 0.122 sec
		2255	Lambda/AnyEvent 0.327 sec
		2256	+ optimized 0.138 sec
		2257	Raw sockets/select 0.077 sec
		2258	POE/select, components 0.662 sec
		2259	POE/select, raw sockets 0.226 sec
		2260	POE/select, optimized 0.404 sec
		2261
		2262	AnyEvent/select/nb 0.085 sec
		2263	AnyEvent/EV/nb 0.068 sec
		2264	+state machine 0.134 sec
		2265
		2266	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2267	benchmarks actually make blocking connects and use 100% blocking I/O,
		2268	defeating the purpose of an event-based solution. All of the newly
		2269	written AnyEvent benchmarks use 100% non-blocking connects (using
		2270	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2271	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2272	generally require a lot more bookkeeping and event handling than blocking
		2273	connects (which involve a single syscall only).
		2274
		2275	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2276	offers similar expressive power as POE and IO::Lambda, using conventional
		2277	Perl syntax. This means that both the echo server and the client are 100%
		2278	non-blocking, further placing it at a disadvantage.
		2279
		2280	As you can see, the AnyEvent + EV combination even beats the
		2281	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2282	backend easily beats IO::Lambda and POE.
		2283
		2284	And even the 100% non-blocking version written using the high-level (and
		2285	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda by a
		2286	large margin, even though it does all of DNS, tcp-connect and socket I/O
		2287	in a non-blocking way.
		2288
		2289	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2290	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2291	part of the IO::lambda distribution and were used without any changes.
		2292
		2293
		2294	=head1 SIGNALS
		2295
		2296	AnyEvent currently installs handlers for these signals:
		2297
		2298	=over 4
		2299
		2300	=item SIGCHLD
		2301
		2302	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2303	emulation for event loops that do not support them natively. Also, some
		2304	event loops install a similar handler.
		2305
		2306	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2307	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2308
		2309	=item SIGPIPE
		2310
		2311	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2312	when AnyEvent gets loaded.
		2313
		2314	The rationale for this is that AnyEvent users usually do not really depend
		2315	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2316	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2317	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2318	some random socket.
		2319
		2320	The rationale for installing a no-op handler as opposed to ignoring it is
		2321	that this way, the handler will be restored to defaults on exec.
		2322
		2323	Feel free to install your own handler, or reset it to defaults.
		2324
		2325	=back
		2326
		2327	=cut
		2328
		2329	undef $SIG{CHLD}
		2330	if $SIG{CHLD} eq 'IGNORE';
		2331
		2332	$SIG{PIPE} = sub { }
		2333	unless defined $SIG{PIPE};
		2334
		2335	=head1 RECOMMENDED/OPTIONAL MODULES
		2336
		2337	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2338	it's built-in modules) are required to use it.
		2339
		2340	That does not mean that AnyEvent won't take advantage of some additional
		2341	modules if they are installed.
		2342
		2343	This section epxlains which additional modules will be used, and how they
		2344	affect AnyEvent's operetion.
		2345
		2346	=over 4
		2347
		2348	=item L<Async::Interrupt>
		2349
		2350	This slightly arcane module is used to implement fast signal handling: To
		2351	my knowledge, there is no way to do completely race-free and quick
		2352	signal handling in pure perl. To ensure that signals still get
		2353	delivered, AnyEvent will start an interval timer to wake up perl (and
		2354	catch the signals) with some delay (default is 10 seconds, look for
		2355	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2356
		2357	If this module is available, then it will be used to implement signal
		2358	catching, which means that signals will not be delayed, and the event loop
		2359	will not be interrupted regularly, which is more efficient (And good for
		2360	battery life on laptops).
		2361
		2362	This affects not just the pure-perl event loop, but also other event loops
		2363	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2364
		2365	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2366	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2367	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2368	does nothing for those backends.
		2369
		2370	=item L<EV>
		2371
		2372	This module isn't really "optional", as it is simply one of the backend
		2373	event loops that AnyEvent can use. However, it is simply the best event
		2374	loop available in terms of features, speed and stability: It supports
		2375	the AnyEvent API optimally, implements all the watcher types in XS, does
		2376	automatic timer adjustments even when no monotonic clock is available,
		2377	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2378	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2379	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2380
		2381	=item L<Guard>
		2382
		2383	The guard module, when used, will be used to implement
		2384	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2385	lot less memory), but otherwise doesn't affect guard operation much. It is
		2386	purely used for performance.
		2387
		2388	=item L<JSON> and L<JSON::XS>
		2389
		2390	This module is required when you want to read or write JSON data via
		2391	L<AnyEvent::Handle>. It is also written in pure-perl, but can take
		2392	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2393
		2394	In fact, L<AnyEvent::Handle> will use L<JSON::XS> by default if it is
		2395	installed.
		2396
		2397	=item L<Net::SSLeay>
		2398
		2399	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2400	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2401	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2402
		2403	=item L<Time::HiRes>
		2404
		2405	This module is part of perl since release 5.008. It will be used when the
		2406	chosen event library does not come with a timing source on it's own. The
		2407	pure-perl event loop (L<AnyEvent::Impl::Perl>) will additionally use it to
		2408	try to use a monotonic clock for timing stability.
		2409
		2410	=back
		2411
1204		2412
1205	=head1 FORK	2413	=head1 FORK
1206		2414
1207	Most event libraries are not fork-safe. The ones who are usually are	2415	Most event libraries are not fork-safe. The ones who are usually are
1208	because they are so inefficient. Only L<EV> is fully fork-aware.	2416	because they rely on inefficient but fork-safe C<select> or C<poll>
		2417	calls. Only L<EV> is fully fork-aware.
1209		2418
1210	If you have to fork, you must either do so I<before> creating your first	2419	If you have to fork, you must either do so I<before> creating your first
1211	watcher OR you must not use AnyEvent at all in the child.	2420	watcher OR you must not use AnyEvent at all in the child OR you must do
		2421	something completely out of the scope of AnyEvent.
1212		2422
1213		2423
1214	=head1 SECURITY CONSIDERATIONS	2424	=head1 SECURITY CONSIDERATIONS
1215		2425
1216	AnyEvent can be forced to load any event model via	2426	AnyEvent can be forced to load any event model via
…		…
1221	specified in the variable.	2431	specified in the variable.
1222		2432
1223	You can make AnyEvent completely ignore this variable by deleting it	2433	You can make AnyEvent completely ignore this variable by deleting it
1224	before the first watcher gets created, e.g. with a C<BEGIN> block:	2434	before the first watcher gets created, e.g. with a C<BEGIN> block:
1225		2435
1226	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	2436	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1227		2437
1228	use AnyEvent;	2438	use AnyEvent;
		2439
		2440	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		2441	be used to probe what backend is used and gain other information (which is
		2442	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2443	$ENV{PERL_ANYEVENT_STRICT}.
		2444
		2445	Note that AnyEvent will remove I<all> environment variables starting with
		2446	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2447	enabled.
		2448
		2449
		2450	=head1 BUGS
		2451
		2452	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2453	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2454	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2455	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2456	pronounced).
1229		2457
1230		2458
1231	=head1 SEE ALSO	2459	=head1 SEE ALSO
1232		2460
1233	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	2461	Utility functions: L<AnyEvent::Util>.
1234	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,	2462
		2463	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
1235	L<Event::Lib>, L<Qt>, L<POE>.	2464	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
1236		2465
1237	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	2466	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
		2467	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
		2468	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1238	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,	2469	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>, L<Anyevent::Impl::Irssi>.
1239	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,
1240	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.
1241		2470
		2471	Non-blocking file handles, sockets, TCP clients and
		2472	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
		2473
		2474	Asynchronous DNS: L<AnyEvent::DNS>.
		2475
		2476	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>,
		2477	L<Coro::Event>,
		2478
1242	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	2479	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::XMPP>,
		2480	L<AnyEvent::HTTP>.
1243		2481
1244		2482
1245	=head1 AUTHOR	2483	=head1 AUTHOR
1246		2484
1247	Marc Lehmann <schmorp@schmorp.de>	2485	Marc Lehmann <schmorp@schmorp.de>
1248	http://home.schmorp.de/	2486	http://home.schmorp.de/
1249		2487
1250	=cut	2488	=cut
1251		2489
1252	1	2490	1
1253		2491

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