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Revision 1.277 by root, Sun Aug 9 13:27:23 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		108
72	=head1 DESCRIPTION	109	=head1 DESCRIPTION
73		110
74	L<AnyEvent> provides an identical interface to multiple event loops. This	111	L<AnyEvent> provides an identical interface to multiple event loops. This
75	allows module authors to utilise an event loop without forcing module	112	allows module authors to utilise an event loop without forcing module
…		…
79	The interface itself is vaguely similar, but not identical to the L<Event>	116	The interface itself is vaguely similar, but not identical to the L<Event>
80	module.	117	module.
81		118
82	During the first call of any watcher-creation method, the module tries	119	During the first call of any watcher-creation method, the module tries
83	to detect the currently loaded event loop by probing whether one of the	120	to detect the currently loaded event loop by probing whether one of the
84	following modules is already loaded: L<Coro::EV>, L<Coro::Event>, L<EV>,	121	following modules is already loaded: L<EV>,
85	L<Event>, L<Glib>, L<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>,
86	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
87	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
88	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
89	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
…		…
103	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
104	use AnyEvent so their modules work together with others seamlessly...	141	use AnyEvent so their modules work together with others seamlessly...
105		142
106	The pure-perl implementation of AnyEvent is called	143	The pure-perl implementation of AnyEvent is called
107	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
108	explicitly.	145	explicitly and enjoy the high availability of that event loop :)
109		146
110	=head1 WATCHERS	147	=head1 WATCHERS
111		148
112	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
113	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
114	the callback to call, the filehandle to watch, etc.	151	the callback to call, the file handle to watch, etc.
115		152
116	These watchers are normal Perl objects with normal Perl lifetime. After	153	These watchers are normal Perl objects with normal Perl lifetime. After
117	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
118	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
119	is in control).	156	is in control).
120		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
121	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
122	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
123	to it).	166	to it).
124		167
125	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.
…		…
127	Many watchers either are used with "recursion" (repeating timers for	170	Many watchers either are used with "recursion" (repeating timers for
128	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.
129		172
130	An any way to achieve that is this pattern:	173	An any way to achieve that is this pattern:
131		174
132	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	175	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
133	# you can use $w here, for example to undef it	176	# you can use $w here, for example to undef it
134	undef $w;	177	undef $w;
135	});	178	});
136		179
137	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,
138	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
139	declared.	182	declared.
140		183
141	=head2 I/O WATCHERS	184	=head2 I/O WATCHERS
142		185
		186	$w = AnyEvent->io (
		187	fh => <filehandle_or_fileno>,
		188	poll => <"r" or "w">,
		189	cb => <callback>,
		190	);
		191
143	You can create an I/O watcher by calling the C<< AnyEvent->io >> method	192	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
144	with the following mandatory key-value pairs as arguments:	193	with the following mandatory key-value pairs as arguments:
145		194
146	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch	195	C<fh> is the Perl I<file handle> (or a naked file descriptor) to watch
		196	for events (AnyEvent might or might not keep a reference to this file
		197	handle). Note that only file handles pointing to things for which
		198	non-blocking operation makes sense are allowed. This includes sockets,
		199	most character devices, pipes, fifos and so on, but not for example files
		200	or block devices.
		201
147	for events. C<poll> must be a string that is either C<r> or C<w>,	202	C<poll> must be a string that is either C<r> or C<w>, which creates a
148	which creates a watcher waiting for "r"eadable or "w"ritable events,	203	watcher waiting for "r"eadable or "w"ritable events, respectively.
		204
149	respectively. C<cb> is the callback to invoke each time the file handle	205	C<cb> is the callback to invoke each time the file handle becomes ready.
150	becomes ready.
151		206
152	Although the callback might get passed parameters, their value and	207	Although the callback might get passed parameters, their value and
153	presence is undefined and you cannot rely on them. Portable AnyEvent	208	presence is undefined and you cannot rely on them. Portable AnyEvent
154	callbacks cannot use arguments passed to I/O watcher callbacks.	209	callbacks cannot use arguments passed to I/O watcher callbacks.
155		210
…		…
159		214
160	Some event loops issue spurious readyness notifications, so you should	215	Some event loops issue spurious readyness notifications, so you should
161	always use non-blocking calls when reading/writing from/to your file	216	always use non-blocking calls when reading/writing from/to your file
162	handles.	217	handles.
163		218
164	Example:
165
166	# wait for readability of STDIN, then read a line and disable the watcher	219	Example: wait for readability of STDIN, then read a line and disable the
		220	watcher.
		221
167	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	222	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
168	chomp (my $input = <STDIN>);	223	chomp (my $input = <STDIN>);
169	warn "read: $input\n";	224	warn "read: $input\n";
170	undef $w;	225	undef $w;
171	});	226	});
172		227
173	=head2 TIME WATCHERS	228	=head2 TIME WATCHERS
174		229
		230	$w = AnyEvent->timer (after => <seconds>, cb => <callback>);
		231
		232	$w = AnyEvent->timer (
		233	after => <fractional_seconds>,
		234	interval => <fractional_seconds>,
		235	cb => <callback>,
		236	);
		237
175	You can create a time watcher by calling the C<< AnyEvent->timer >>	238	You can create a time watcher by calling the C<< AnyEvent->timer >>
176	method with the following mandatory arguments:	239	method with the following mandatory arguments:
177		240
178	C<after> specifies after how many seconds (fractional values are	241	C<after> specifies after how many seconds (fractional values are
179	supported) the callback should be invoked. C<cb> is the callback to invoke	242	supported) the callback should be invoked. C<cb> is the callback to invoke
…		…
181		244
182	Although the callback might get passed parameters, their value and	245	Although the callback might get passed parameters, their value and
183	presence is undefined and you cannot rely on them. Portable AnyEvent	246	presence is undefined and you cannot rely on them. Portable AnyEvent
184	callbacks cannot use arguments passed to time watcher callbacks.	247	callbacks cannot use arguments passed to time watcher callbacks.
185		248
186	The timer callback will be invoked at most once: if you want a repeating	249	The callback will normally be invoked once only. If you specify another
187	timer you have to create a new watcher (this is a limitation by both Tk	250	parameter, C<interval>, as a strictly positive number (> 0), then the
188	and Glib).	251	callback will be invoked regularly at that interval (in fractional
		252	seconds) after the first invocation. If C<interval> is specified with a
		253	false value, then it is treated as if it were missing.
189		254
190	Example:	255	The callback will be rescheduled before invoking the callback, but no
		256	attempt is done to avoid timer drift in most backends, so the interval is
		257	only approximate.
191		258
192	# fire an event after 7.7 seconds	259	Example: fire an event after 7.7 seconds.
		260
193	my $w = AnyEvent->timer (after => 7.7, cb => sub {	261	my $w = AnyEvent->timer (after => 7.7, cb => sub {
194	warn "timeout\n";	262	warn "timeout\n";
195	});	263	});
196		264
197	# to cancel the timer:	265	# to cancel the timer:
198	undef $w;	266	undef $w;
199		267
200	Example 2:
201
202	# fire an event after 0.5 seconds, then roughly every second	268	Example 2: fire an event after 0.5 seconds, then roughly every second.
203	my $w;
204		269
205	my $cb = sub {
206	# cancel the old timer while creating a new one
207	$w = AnyEvent->timer (after => 1, cb => $cb);	270	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		271	warn "timeout\n";
208	};	272	};
209
210	# start the "loop" by creating the first watcher
211	$w = AnyEvent->timer (after => 0.5, cb => $cb);
212		273
213	=head3 TIMING ISSUES	274	=head3 TIMING ISSUES
214		275
215	There are two ways to handle timers: based on real time (relative, "fire	276	There are two ways to handle timers: based on real time (relative, "fire
216	in 10 seconds") and based on wallclock time (absolute, "fire at 12	277	in 10 seconds") and based on wallclock time (absolute, "fire at 12
…		…
228	timers.	289	timers.
229		290
230	AnyEvent always prefers relative timers, if available, matching the	291	AnyEvent always prefers relative timers, if available, matching the
231	AnyEvent API.	292	AnyEvent API.
232		293
		294	AnyEvent has two additional methods that return the "current time":
		295
		296	=over 4
		297
		298	=item AnyEvent->time
		299
		300	This returns the "current wallclock time" as a fractional number of
		301	seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
		302	return, and the result is guaranteed to be compatible with those).
		303
		304	It progresses independently of any event loop processing, i.e. each call
		305	will check the system clock, which usually gets updated frequently.
		306
		307	=item AnyEvent->now
		308
		309	This also returns the "current wallclock time", but unlike C<time>, above,
		310	this value might change only once per event loop iteration, depending on
		311	the event loop (most return the same time as C<time>, above). This is the
		312	time that AnyEvent's timers get scheduled against.
		313
		314	I<In almost all cases (in all cases if you don't care), this is the
		315	function to call when you want to know the current time.>
		316
		317	This function is also often faster then C<< AnyEvent->time >>, and
		318	thus the preferred method if you want some timestamp (for example,
		319	L<AnyEvent::Handle> uses this to update it's activity timeouts).
		320
		321	The rest of this section is only of relevance if you try to be very exact
		322	with your timing, you can skip it without bad conscience.
		323
		324	For a practical example of when these times differ, consider L<Event::Lib>
		325	and L<EV> and the following set-up:
		326
		327	The event loop is running and has just invoked one of your callback at
		328	time=500 (assume no other callbacks delay processing). In your callback,
		329	you wait a second by executing C<sleep 1> (blocking the process for a
		330	second) and then (at time=501) you create a relative timer that fires
		331	after three seconds.
		332
		333	With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
		334	both return C<501>, because that is the current time, and the timer will
		335	be scheduled to fire at time=504 (C<501> + C<3>).
		336
		337	With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
		338	time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
		339	last event processing phase started. With L<EV>, your timer gets scheduled
		340	to run at time=503 (C<500> + C<3>).
		341
		342	In one sense, L<Event::Lib> is more exact, as it uses the current time
		343	regardless of any delays introduced by event processing. However, most
		344	callbacks do not expect large delays in processing, so this causes a
		345	higher drift (and a lot more system calls to get the current time).
		346
		347	In another sense, L<EV> is more exact, as your timer will be scheduled at
		348	the same time, regardless of how long event processing actually took.
		349
		350	In either case, if you care (and in most cases, you don't), then you
		351	can get whatever behaviour you want with any event loop, by taking the
		352	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
		353	account.
		354
		355	=item AnyEvent->now_update
		356
		357	Some event loops (such as L<EV> or L<AnyEvent::Impl::Perl>) cache
		358	the current time for each loop iteration (see the discussion of L<<
		359	AnyEvent->now >>, above).
		360
		361	When a callback runs for a long time (or when the process sleeps), then
		362	this "current" time will differ substantially from the real time, which
		363	might affect timers and time-outs.
		364
		365	When this is the case, you can call this method, which will update the
		366	event loop's idea of "current time".
		367
		368	Note that updating the time I<might> cause some events to be handled.
		369
		370	=back
		371
233	=head2 SIGNAL WATCHERS	372	=head2 SIGNAL WATCHERS
234		373
		374	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		375
235	You can watch for signals using a signal watcher, C<signal> is the signal	376	You can watch for signals using a signal watcher, C<signal> is the signal
236	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to	377	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
237	be invoked whenever a signal occurs.	378	callback to be invoked whenever a signal occurs.
238		379
239	Although the callback might get passed parameters, their value and	380	Although the callback might get passed parameters, their value and
240	presence is undefined and you cannot rely on them. Portable AnyEvent	381	presence is undefined and you cannot rely on them. Portable AnyEvent
241	callbacks cannot use arguments passed to signal watcher callbacks.	382	callbacks cannot use arguments passed to signal watcher callbacks.
242		383
243	Multiple signal occurances can be clumped together into one callback	384	Multiple signal occurrences can be clumped together into one callback
244	invocation, and callback invocation will be synchronous. synchronous means	385	invocation, and callback invocation will be synchronous. Synchronous means
245	that it might take a while until the signal gets handled by the process,	386	that it might take a while until the signal gets handled by the process,
246	but it is guarenteed not to interrupt any other callbacks.	387	but it is guaranteed not to interrupt any other callbacks.
247		388
248	The main advantage of using these watchers is that you can share a signal	389	The main advantage of using these watchers is that you can share a signal
249	between multiple watchers.	390	between multiple watchers, and AnyEvent will ensure that signals will not
		391	interrupt your program at bad times.
250		392
251	This watcher might use C<%SIG>, so programs overwriting those signals	393	This watcher might use C<%SIG> (depending on the event loop used),
252	directly will likely not work correctly.	394	so programs overwriting those signals directly will likely not work
		395	correctly.
253		396
254	Example: exit on SIGINT	397	Example: exit on SIGINT
255		398
256	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	399	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
257		400
		401	=head3 Signal Races, Delays and Workarounds
		402
		403	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		404	callbacks to signals in a generic way, which is a pity, as you cannot
		405	do race-free signal handling in perl, requiring C libraries for
		406	this. AnyEvent will try to do it's best, which means in some cases,
		407	signals will be delayed. The maximum time a signal might be delayed is
		408	specified in C<$AnyEvent::MAX_SIGNAL_LATENCY> (default: 10 seconds). This
		409	variable can be changed only before the first signal watcher is created,
		410	and should be left alone otherwise. This variable determines how often
		411	AnyEvent polls for signals (in case a wake-up was missed). Higher values
		412	will cause fewer spurious wake-ups, which is better for power and CPU
		413	saving.
		414
		415	All these problems can be avoided by installing the optional
		416	L<Async::Interrupt> module, which works with most event loops. It will not
		417	work with inherently broken event loops such as L<Event> or L<Event::Lib>
		418	(and not with L<POE> currently, as POE does it's own workaround with
		419	one-second latency). For those, you just have to suffer the delays.
		420
258	=head2 CHILD PROCESS WATCHERS	421	=head2 CHILD PROCESS WATCHERS
259		422
		423	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		424
260	You can also watch on a child process exit and catch its exit status.	425	You can also watch on a child process exit and catch its exit status.
261		426
262	The child process is specified by the C<pid> argument (if set to C<0>, it	427	The child process is specified by the C<pid> argument (one some backends,
263	watches for any child process exit). The watcher will trigger as often	428	using C<0> watches for any child process exit, on others this will
264	as status change for the child are received. This works by installing a	429	croak). The watcher will be triggered only when the child process has
265	signal handler for C<SIGCHLD>. The callback will be called with the pid	430	finished and an exit status is available, not on any trace events
266	and exit status (as returned by waitpid), so unlike other watcher types,	431	(stopped/continued).
267	you I<can> rely on child watcher callback arguments.	432
		433	The callback will be called with the pid and exit status (as returned by
		434	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		435	callback arguments.
		436
		437	This watcher type works by installing a signal handler for C<SIGCHLD>,
		438	and since it cannot be shared, nothing else should use SIGCHLD or reap
		439	random child processes (waiting for specific child processes, e.g. inside
		440	C<system>, is just fine).
268		441
269	There is a slight catch to child watchers, however: you usually start them	442	There is a slight catch to child watchers, however: you usually start them
270	I<after> the child process was created, and this means the process could	443	I<after> the child process was created, and this means the process could
271	have exited already (and no SIGCHLD will be sent anymore).	444	have exited already (and no SIGCHLD will be sent anymore).
272		445
273	Not all event models handle this correctly (POE doesn't), but even for	446	Not all event models handle this correctly (neither POE nor IO::Async do,
		447	see their AnyEvent::Impl manpages for details), but even for event models
274	event models that I<do> handle this correctly, they usually need to be	448	that I<do> handle this correctly, they usually need to be loaded before
275	loaded before the process exits (i.e. before you fork in the first place).	449	the process exits (i.e. before you fork in the first place). AnyEvent's
		450	pure perl event loop handles all cases correctly regardless of when you
		451	start the watcher.
276		452
277	This means you cannot create a child watcher as the very first thing in an	453	This means you cannot create a child watcher as the very first
278	AnyEvent program, you I<have> to create at least one watcher before you	454	thing in an AnyEvent program, you I<have> to create at least one
279	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).	455	watcher before you C<fork> the child (alternatively, you can call
		456	C<AnyEvent::detect>).
		457
		458	As most event loops do not support waiting for child events, they will be
		459	emulated by AnyEvent in most cases, in which the latency and race problems
		460	mentioned in the description of signal watchers apply.
280		461
281	Example: fork a process and wait for it	462	Example: fork a process and wait for it
282		463
283	my $done = AnyEvent->condvar;	464	my $done = AnyEvent->condvar;
284		465
285	AnyEvent::detect; # force event module to be initialised
286
287	my $pid = fork or exit 5;	466	my $pid = fork or exit 5;
288		467
289	my $w = AnyEvent->child (	468	my $w = AnyEvent->child (
290	pid => $pid,	469	pid => $pid,
291	cb => sub {	470	cb => sub {
292	my ($pid, $status) = @_;	471	my ($pid, $status) = @_;
293	warn "pid $pid exited with status $status";	472	warn "pid $pid exited with status $status";
294	$done->broadcast;	473	$done->send;
295	},	474	},
296	);	475	);
297		476
298	# do something else, then wait for process exit	477	# do something else, then wait for process exit
299	$done->wait;	478	$done->recv;
		479
		480	=head2 IDLE WATCHERS
		481
		482	$w = AnyEvent->idle (cb => <callback>);
		483
		484	Sometimes there is a need to do something, but it is not so important
		485	to do it instantly, but only when there is nothing better to do. This
		486	"nothing better to do" is usually defined to be "no other events need
		487	attention by the event loop".
		488
		489	Idle watchers ideally get invoked when the event loop has nothing
		490	better to do, just before it would block the process to wait for new
		491	events. Instead of blocking, the idle watcher is invoked.
		492
		493	Most event loops unfortunately do not really support idle watchers (only
		494	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		495	will simply call the callback "from time to time".
		496
		497	Example: read lines from STDIN, but only process them when the
		498	program is otherwise idle:
		499
		500	my @lines; # read data
		501	my $idle_w;
		502	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		503	push @lines, scalar <STDIN>;
		504
		505	# start an idle watcher, if not already done
		506	$idle_w ||= AnyEvent->idle (cb => sub {
		507	# handle only one line, when there are lines left
		508	if (my $line = shift @lines) {
		509	print "handled when idle: $line";
		510	} else {
		511	# otherwise disable the idle watcher again
		512	undef $idle_w;
		513	}
		514	});
		515	});
300		516
301	=head2 CONDITION VARIABLES	517	=head2 CONDITION VARIABLES
302		518
		519	$cv = AnyEvent->condvar;
		520
		521	$cv->send (<list>);
		522	my @res = $cv->recv;
		523
		524	If you are familiar with some event loops you will know that all of them
		525	require you to run some blocking "loop", "run" or similar function that
		526	will actively watch for new events and call your callbacks.
		527
		528	AnyEvent is slightly different: it expects somebody else to run the event
		529	loop and will only block when necessary (usually when told by the user).
		530
		531	The instrument to do that is called a "condition variable", so called
		532	because they represent a condition that must become true.
		533
		534	Now is probably a good time to look at the examples further below.
		535
303	Condition variables can be created by calling the C<< AnyEvent->condvar >>	536	Condition variables can be created by calling the C<< AnyEvent->condvar
304	method without any arguments.	537	>> method, usually without arguments. The only argument pair allowed is
		538	C<cb>, which specifies a callback to be called when the condition variable
		539	becomes true, with the condition variable as the first argument (but not
		540	the results).
305		541
306	A condition variable waits for a condition - precisely that the C<<	542	After creation, the condition variable is "false" until it becomes "true"
307	->broadcast >> method has been called.	543	by calling the C<send> method (or calling the condition variable as if it
		544	were a callback, read about the caveats in the description for the C<<
		545	->send >> method).
308		546
309	They are very useful to signal that a condition has been fulfilled, for	547	Condition variables are similar to callbacks, except that you can
		548	optionally wait for them. They can also be called merge points - points
		549	in time where multiple outstanding events have been processed. And yet
		550	another way to call them is transactions - each condition variable can be
		551	used to represent a transaction, which finishes at some point and delivers
		552	a result. And yet some people know them as "futures" - a promise to
		553	compute/deliver something that you can wait for.
		554
		555	Condition variables are very useful to signal that something has finished,
310	example, if you write a module that does asynchronous http requests,	556	for example, if you write a module that does asynchronous http requests,
311	then a condition variable would be the ideal candidate to signal the	557	then a condition variable would be the ideal candidate to signal the
312	availability of results.	558	availability of results. The user can either act when the callback is
		559	called or can synchronously C<< ->recv >> for the results.
313		560
314	You can also use condition variables to block your main program until	561	You can also use them to simulate traditional event loops - for example,
315	an event occurs - for example, you could C<< ->wait >> in your main	562	you can block your main program until an event occurs - for example, you
316	program until the user clicks the Quit button in your app, which would C<<	563	could C<< ->recv >> in your main program until the user clicks the Quit
317	->broadcast >> the "quit" event.	564	button of your app, which would C<< ->send >> the "quit" event.
318		565
319	Note that condition variables recurse into the event loop - if you have	566	Note that condition variables recurse into the event loop - if you have
320	two pirces of code that call C<< ->wait >> in a round-robbin fashion, you	567	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
321	lose. Therefore, condition variables are good to export to your caller, but	568	lose. Therefore, condition variables are good to export to your caller, but
322	you should avoid making a blocking wait yourself, at least in callbacks,	569	you should avoid making a blocking wait yourself, at least in callbacks,
323	as this asks for trouble.	570	as this asks for trouble.
324		571
325	This object has two methods:	572	Condition variables are represented by hash refs in perl, and the keys
		573	used by AnyEvent itself are all named C<_ae_XXX> to make subclassing
		574	easy (it is often useful to build your own transaction class on top of
		575	AnyEvent). To subclass, use C<AnyEvent::CondVar> as base class and call
		576	it's C<new> method in your own C<new> method.
326		577
327	=over 4	578	There are two "sides" to a condition variable - the "producer side" which
		579	eventually calls C<< -> send >>, and the "consumer side", which waits
		580	for the send to occur.
328		581
329	=item $cv->wait	582	Example: wait for a timer.
330
331	Wait (blocking if necessary) until the C<< ->broadcast >> method has been
332	called on c<$cv>, while servicing other watchers normally.
333
334	You can only wait once on a condition - additional calls will return
335	immediately.
336
337	Not all event models support a blocking wait - some die in that case
338	(programs might want to do that to stay interactive), so I<if you are
339	using this from a module, never require a blocking wait>, but let the
340	caller decide whether the call will block or not (for example, by coupling
341	condition variables with some kind of request results and supporting
342	callbacks so the caller knows that getting the result will not block,
343	while still suppporting blocking waits if the caller so desires).
344
345	Another reason I<never> to C<< ->wait >> in a module is that you cannot
346	sensibly have two C<< ->wait >>'s in parallel, as that would require
347	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
348	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and
349	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
350	from different coroutines, however).
351
352	=item $cv->broadcast
353
354	Flag the condition as ready - a running C<< ->wait >> and all further
355	calls to C<wait> will (eventually) return after this method has been
356	called. If nobody is waiting the broadcast will be remembered..
357
358	=back
359
360	Example:
361		583
362	# wait till the result is ready	584	# wait till the result is ready
363	my $result_ready = AnyEvent->condvar;	585	my $result_ready = AnyEvent->condvar;
364		586
365	# do something such as adding a timer	587	# do something such as adding a timer
366	# or socket watcher the calls $result_ready->broadcast	588	# or socket watcher the calls $result_ready->send
367	# when the "result" is ready.	589	# when the "result" is ready.
368	# in this case, we simply use a timer:	590	# in this case, we simply use a timer:
369	my $w = AnyEvent->timer (	591	my $w = AnyEvent->timer (
370	after => 1,	592	after => 1,
371	cb => sub { $result_ready->broadcast },	593	cb => sub { $result_ready->send },
372	);	594	);
373		595
374	# this "blocks" (while handling events) till the watcher	596	# this "blocks" (while handling events) till the callback
375	# calls broadcast	597	# calls -<send
376	$result_ready->wait;	598	$result_ready->recv;
		599
		600	Example: wait for a timer, but take advantage of the fact that condition
		601	variables are also callable directly.
		602
		603	my $done = AnyEvent->condvar;
		604	my $delay = AnyEvent->timer (after => 5, cb => $done);
		605	$done->recv;
		606
		607	Example: Imagine an API that returns a condvar and doesn't support
		608	callbacks. This is how you make a synchronous call, for example from
		609	the main program:
		610
		611	use AnyEvent::CouchDB;
		612
		613	...
		614
		615	my @info = $couchdb->info->recv;
		616
		617	And this is how you would just set a callback to be called whenever the
		618	results are available:
		619
		620	$couchdb->info->cb (sub {
		621	my @info = $_[0]->recv;
		622	});
		623
		624	=head3 METHODS FOR PRODUCERS
		625
		626	These methods should only be used by the producing side, i.e. the
		627	code/module that eventually sends the signal. Note that it is also
		628	the producer side which creates the condvar in most cases, but it isn't
		629	uncommon for the consumer to create it as well.
		630
		631	=over 4
		632
		633	=item $cv->send (...)
		634
		635	Flag the condition as ready - a running C<< ->recv >> and all further
		636	calls to C<recv> will (eventually) return after this method has been
		637	called. If nobody is waiting the send will be remembered.
		638
		639	If a callback has been set on the condition variable, it is called
		640	immediately from within send.
		641
		642	Any arguments passed to the C<send> call will be returned by all
		643	future C<< ->recv >> calls.
		644
		645	Condition variables are overloaded so one can call them directly (as if
		646	they were a code reference). Calling them directly is the same as calling
		647	C<send>.
		648
		649	=item $cv->croak ($error)
		650
		651	Similar to send, but causes all call's to C<< ->recv >> to invoke
		652	C<Carp::croak> with the given error message/object/scalar.
		653
		654	This can be used to signal any errors to the condition variable
		655	user/consumer. Doing it this way instead of calling C<croak> directly
		656	delays the error detetcion, but has the overwhelmign advantage that it
		657	diagnoses the error at the place where the result is expected, and not
		658	deep in some event clalback without connection to the actual code causing
		659	the problem.
		660
		661	=item $cv->begin ([group callback])
		662
		663	=item $cv->end
		664
		665	These two methods can be used to combine many transactions/events into
		666	one. For example, a function that pings many hosts in parallel might want
		667	to use a condition variable for the whole process.
		668
		669	Every call to C<< ->begin >> will increment a counter, and every call to
		670	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
		671	>>, the (last) callback passed to C<begin> will be executed. That callback
		672	is I<supposed> to call C<< ->send >>, but that is not required. If no
		673	callback was set, C<send> will be called without any arguments.
		674
		675	You can think of C<< $cv->send >> giving you an OR condition (one call
		676	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		677	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		678
		679	Let's start with a simple example: you have two I/O watchers (for example,
		680	STDOUT and STDERR for a program), and you want to wait for both streams to
		681	close before activating a condvar:
		682
		683	my $cv = AnyEvent->condvar;
		684
		685	$cv->begin; # first watcher
		686	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		687	defined sysread $fh1, my $buf, 4096
		688	or $cv->end;
		689	});
		690
		691	$cv->begin; # second watcher
		692	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		693	defined sysread $fh2, my $buf, 4096
		694	or $cv->end;
		695	});
		696
		697	$cv->recv;
		698
		699	This works because for every event source (EOF on file handle), there is
		700	one call to C<begin>, so the condvar waits for all calls to C<end> before
		701	sending.
		702
		703	The ping example mentioned above is slightly more complicated, as the
		704	there are results to be passwd back, and the number of tasks that are
		705	begung can potentially be zero:
		706
		707	my $cv = AnyEvent->condvar;
		708
		709	my %result;
		710	$cv->begin (sub { $cv->send (\%result) });
		711
		712	for my $host (@list_of_hosts) {
		713	$cv->begin;
		714	ping_host_then_call_callback $host, sub {
		715	$result{$host} = ...;
		716	$cv->end;
		717	};
		718	}
		719
		720	$cv->end;
		721
		722	This code fragment supposedly pings a number of hosts and calls
		723	C<send> after results for all then have have been gathered - in any
		724	order. To achieve this, the code issues a call to C<begin> when it starts
		725	each ping request and calls C<end> when it has received some result for
		726	it. Since C<begin> and C<end> only maintain a counter, the order in which
		727	results arrive is not relevant.
		728
		729	There is an additional bracketing call to C<begin> and C<end> outside the
		730	loop, which serves two important purposes: first, it sets the callback
		731	to be called once the counter reaches C<0>, and second, it ensures that
		732	C<send> is called even when C<no> hosts are being pinged (the loop
		733	doesn't execute once).
		734
		735	This is the general pattern when you "fan out" into multiple (but
		736	potentially none) subrequests: use an outer C<begin>/C<end> pair to set
		737	the callback and ensure C<end> is called at least once, and then, for each
		738	subrequest you start, call C<begin> and for each subrequest you finish,
		739	call C<end>.
		740
		741	=back
		742
		743	=head3 METHODS FOR CONSUMERS
		744
		745	These methods should only be used by the consuming side, i.e. the
		746	code awaits the condition.
		747
		748	=over 4
		749
		750	=item $cv->recv
		751
		752	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
		753	>> methods have been called on c<$cv>, while servicing other watchers
		754	normally.
		755
		756	You can only wait once on a condition - additional calls are valid but
		757	will return immediately.
		758
		759	If an error condition has been set by calling C<< ->croak >>, then this
		760	function will call C<croak>.
		761
		762	In list context, all parameters passed to C<send> will be returned,
		763	in scalar context only the first one will be returned.
		764
		765	Note that doing a blocking wait in a callback is not supported by any
		766	event loop, that is, recursive invocation of a blocking C<< ->recv
		767	>> is not allowed, and the C<recv> call will C<croak> if such a
		768	condition is detected. This condition can be slightly loosened by using
		769	L<Coro::AnyEvent>, which allows you to do a blocking C<< ->recv >> from
		770	any thread that doesn't run the event loop itself.
		771
		772	Not all event models support a blocking wait - some die in that case
		773	(programs might want to do that to stay interactive), so I<if you are
		774	using this from a module, never require a blocking wait>. Instead, let the
		775	caller decide whether the call will block or not (for example, by coupling
		776	condition variables with some kind of request results and supporting
		777	callbacks so the caller knows that getting the result will not block,
		778	while still supporting blocking waits if the caller so desires).
		779
		780	You can ensure that C<< -recv >> never blocks by setting a callback and
		781	only calling C<< ->recv >> from within that callback (or at a later
		782	time). This will work even when the event loop does not support blocking
		783	waits otherwise.
		784
		785	=item $bool = $cv->ready
		786
		787	Returns true when the condition is "true", i.e. whether C<send> or
		788	C<croak> have been called.
		789
		790	=item $cb = $cv->cb ($cb->($cv))
		791
		792	This is a mutator function that returns the callback set and optionally
		793	replaces it before doing so.
		794
		795	The callback will be called when the condition becomes (or already was)
		796	"true", i.e. when C<send> or C<croak> are called (or were called), with
		797	the only argument being the condition variable itself. Calling C<recv>
		798	inside the callback or at any later time is guaranteed not to block.
		799
		800	=back
		801
		802	=head1 SUPPORTED EVENT LOOPS/BACKENDS
		803
		804	The available backend classes are (every class has its own manpage):
		805
		806	=over 4
		807
		808	=item Backends that are autoprobed when no other event loop can be found.
		809
		810	EV is the preferred backend when no other event loop seems to be in
		811	use. If EV is not installed, then AnyEvent will fall back to its own
		812	pure-perl implementation, which is available everywhere as it comes with
		813	AnyEvent itself.
		814
		815	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		816	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
		817
		818	=item Backends that are transparently being picked up when they are used.
		819
		820	These will be used when they are currently loaded when the first watcher
		821	is created, in which case it is assumed that the application is using
		822	them. This means that AnyEvent will automatically pick the right backend
		823	when the main program loads an event module before anything starts to
		824	create watchers. Nothing special needs to be done by the main program.
		825
		826	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		827	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		828	AnyEvent::Impl::Tk based on Tk, very broken.
		829	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		830	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		831	AnyEvent::Impl::Irssi used when running within irssi.
		832
		833	=item Backends with special needs.
		834
		835	Qt requires the Qt::Application to be instantiated first, but will
		836	otherwise be picked up automatically. As long as the main program
		837	instantiates the application before any AnyEvent watchers are created,
		838	everything should just work.
		839
		840	AnyEvent::Impl::Qt based on Qt.
		841
		842	Support for IO::Async can only be partial, as it is too broken and
		843	architecturally limited to even support the AnyEvent API. It also
		844	is the only event loop that needs the loop to be set explicitly, so
		845	it can only be used by a main program knowing about AnyEvent. See
		846	L<AnyEvent::Impl::Async> for the gory details.
		847
		848	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
		849
		850	=item Event loops that are indirectly supported via other backends.
		851
		852	Some event loops can be supported via other modules:
		853
		854	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		855
		856	B<WxWidgets> has no support for watching file handles. However, you can
		857	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		858	polls 20 times per second, which was considered to be too horrible to even
		859	consider for AnyEvent.
		860
		861	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		862	backend, so it can be supported through POE.
		863
		864	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		865	load L<POE> when detecting them, in the hope that POE will pick them up,
		866	in which case everything will be automatic.
		867
		868	=back
377		869
378	=head1 GLOBAL VARIABLES AND FUNCTIONS	870	=head1 GLOBAL VARIABLES AND FUNCTIONS
379		871
		872	These are not normally required to use AnyEvent, but can be useful to
		873	write AnyEvent extension modules.
		874
380	=over 4	875	=over 4
381		876
382	=item $AnyEvent::MODEL	877	=item $AnyEvent::MODEL
383		878
384	Contains C<undef> until the first watcher is being created. Then it	879	Contains C<undef> until the first watcher is being created, before the
		880	backend has been autodetected.
		881
385	contains the event model that is being used, which is the name of the	882	Afterwards it contains the event model that is being used, which is the
386	Perl class implementing the model. This class is usually one of the	883	name of the Perl class implementing the model. This class is usually one
387	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	884	of the C<AnyEvent::Impl:xxx> modules, but can be any other class in the
388	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	885	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
389		886	will be C<urxvt::anyevent>).
390	The known classes so far are:
391
392	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
393	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
394	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
395	AnyEvent::Impl::Event based on Event, second best choice.
396	AnyEvent::Impl::Glib based on Glib, third-best choice.
397	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
398	AnyEvent::Impl::Tk based on Tk, very bad choice.
399	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
400	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
401	AnyEvent::Impl::POE based on POE, not generic enough for full support.
402
403	There is no support for WxWidgets, as WxWidgets has no support for
404	watching file handles. However, you can use WxWidgets through the
405	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
406	second, which was considered to be too horrible to even consider for
407	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
408	it's adaptor.
409
410	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
411	autodetecting them.
412		887
413	=item AnyEvent::detect	888	=item AnyEvent::detect
414		889
415	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	890	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
416	if necessary. You should only call this function right before you would	891	if necessary. You should only call this function right before you would
417	have created an AnyEvent watcher anyway, that is, as late as possible at	892	have created an AnyEvent watcher anyway, that is, as late as possible at
418	runtime.	893	runtime, and not e.g. while initialising of your module.
		894
		895	If you need to do some initialisation before AnyEvent watchers are
		896	created, use C<post_detect>.
		897
		898	=item $guard = AnyEvent::post_detect { BLOCK }
		899
		900	Arranges for the code block to be executed as soon as the event model is
		901	autodetected (or immediately if this has already happened).
		902
		903	The block will be executed I<after> the actual backend has been detected
		904	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		905	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		906	other initialisations - see the sources of L<AnyEvent::Strict> or
		907	L<AnyEvent::AIO> to see how this is used.
		908
		909	The most common usage is to create some global watchers, without forcing
		910	event module detection too early, for example, L<AnyEvent::AIO> creates
		911	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		912	avoid autodetecting the event module at load time.
		913
		914	If called in scalar or list context, then it creates and returns an object
		915	that automatically removes the callback again when it is destroyed (or
		916	C<undef> when the hook was immediately executed). See L<AnyEvent::AIO> for
		917	a case where this is useful.
		918
		919	Example: Create a watcher for the IO::AIO module and store it in
		920	C<$WATCHER>. Only do so after the event loop is initialised, though.
		921
		922	our WATCHER;
		923
		924	my $guard = AnyEvent::post_detect {
		925	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		926	};
		927
		928	# the ||= is important in case post_detect immediately runs the block,
		929	# as to not clobber the newly-created watcher. assigning both watcher and
		930	# post_detect guard to the same variable has the advantage of users being
		931	# able to just C<undef $WATCHER> if the watcher causes them grief.
		932
		933	$WATCHER ||= $guard;
		934
		935	=item @AnyEvent::post_detect
		936
		937	If there are any code references in this array (you can C<push> to it
		938	before or after loading AnyEvent), then they will called directly after
		939	the event loop has been chosen.
		940
		941	You should check C<$AnyEvent::MODEL> before adding to this array, though:
		942	if it is defined then the event loop has already been detected, and the
		943	array will be ignored.
		944
		945	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		946	it,as it takes care of these details.
		947
		948	This variable is mainly useful for modules that can do something useful
		949	when AnyEvent is used and thus want to know when it is initialised, but do
		950	not need to even load it by default. This array provides the means to hook
		951	into AnyEvent passively, without loading it.
419		952
420	=back	953	=back
421		954
422	=head1 WHAT TO DO IN A MODULE	955	=head1 WHAT TO DO IN A MODULE
423		956
…		…
427	Be careful when you create watchers in the module body - AnyEvent will	960	Be careful when you create watchers in the module body - AnyEvent will
428	decide which event module to use as soon as the first method is called, so	961	decide which event module to use as soon as the first method is called, so
429	by calling AnyEvent in your module body you force the user of your module	962	by calling AnyEvent in your module body you force the user of your module
430	to load the event module first.	963	to load the event module first.
431		964
432	Never call C<< ->wait >> on a condition variable unless you I<know> that	965	Never call C<< ->recv >> on a condition variable unless you I<know> that
433	the C<< ->broadcast >> method has been called on it already. This is	966	the C<< ->send >> method has been called on it already. This is
434	because it will stall the whole program, and the whole point of using	967	because it will stall the whole program, and the whole point of using
435	events is to stay interactive.	968	events is to stay interactive.
436		969
437	It is fine, however, to call C<< ->wait >> when the user of your module	970	It is fine, however, to call C<< ->recv >> when the user of your module
438	requests it (i.e. if you create a http request object ad have a method	971	requests it (i.e. if you create a http request object ad have a method
439	called C<results> that returns the results, it should call C<< ->wait >>	972	called C<results> that returns the results, it should call C<< ->recv >>
440	freely, as the user of your module knows what she is doing. always).	973	freely, as the user of your module knows what she is doing. always).
441		974
442	=head1 WHAT TO DO IN THE MAIN PROGRAM	975	=head1 WHAT TO DO IN THE MAIN PROGRAM
443		976
444	There will always be a single main program - the only place that should	977	There will always be a single main program - the only place that should
…		…
446		979
447	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	980	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
448	do anything special (it does not need to be event-based) and let AnyEvent	981	do anything special (it does not need to be event-based) and let AnyEvent
449	decide which implementation to chose if some module relies on it.	982	decide which implementation to chose if some module relies on it.
450		983
451	If the main program relies on a specific event model. For example, in	984	If the main program relies on a specific event model - for example, in
452	Gtk2 programs you have to rely on the Glib module. You should load the	985	Gtk2 programs you have to rely on the Glib module - you should load the
453	event module before loading AnyEvent or any module that uses it: generally	986	event module before loading AnyEvent or any module that uses it: generally
454	speaking, you should load it as early as possible. The reason is that	987	speaking, you should load it as early as possible. The reason is that
455	modules might create watchers when they are loaded, and AnyEvent will	988	modules might create watchers when they are loaded, and AnyEvent will
456	decide on the event model to use as soon as it creates watchers, and it	989	decide on the event model to use as soon as it creates watchers, and it
457	might chose the wrong one unless you load the correct one yourself.	990	might chose the wrong one unless you load the correct one yourself.
458		991
459	You can chose to use a rather inefficient pure-perl implementation by	992	You can chose to use a pure-perl implementation by loading the
460	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	993	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
461	behaviour everywhere, but letting AnyEvent chose is generally better.	994	everywhere, but letting AnyEvent chose the model is generally better.
		995
		996	=head2 MAINLOOP EMULATION
		997
		998	Sometimes (often for short test scripts, or even standalone programs who
		999	only want to use AnyEvent), you do not want to run a specific event loop.
		1000
		1001	In that case, you can use a condition variable like this:
		1002
		1003	AnyEvent->condvar->recv;
		1004
		1005	This has the effect of entering the event loop and looping forever.
		1006
		1007	Note that usually your program has some exit condition, in which case
		1008	it is better to use the "traditional" approach of storing a condition
		1009	variable somewhere, waiting for it, and sending it when the program should
		1010	exit cleanly.
		1011
		1012
		1013	=head1 OTHER MODULES
		1014
		1015	The following is a non-exhaustive list of additional modules that use
		1016	AnyEvent as a client and can therefore be mixed easily with other AnyEvent
		1017	modules and other event loops in the same program. Some of the modules
		1018	come with AnyEvent, most are available via CPAN.
		1019
		1020	=over 4
		1021
		1022	=item L<AnyEvent::Util>
		1023
		1024	Contains various utility functions that replace often-used but blocking
		1025	functions such as C<inet_aton> by event-/callback-based versions.
		1026
		1027	=item L<AnyEvent::Socket>
		1028
		1029	Provides various utility functions for (internet protocol) sockets,
		1030	addresses and name resolution. Also functions to create non-blocking tcp
		1031	connections or tcp servers, with IPv6 and SRV record support and more.
		1032
		1033	=item L<AnyEvent::Handle>
		1034
		1035	Provide read and write buffers, manages watchers for reads and writes,
		1036	supports raw and formatted I/O, I/O queued and fully transparent and
		1037	non-blocking SSL/TLS (via L<AnyEvent::TLS>.
		1038
		1039	=item L<AnyEvent::DNS>
		1040
		1041	Provides rich asynchronous DNS resolver capabilities.
		1042
		1043	=item L<AnyEvent::HTTP>
		1044
		1045	A simple-to-use HTTP library that is capable of making a lot of concurrent
		1046	HTTP requests.
		1047
		1048	=item L<AnyEvent::HTTPD>
		1049
		1050	Provides a simple web application server framework.
		1051
		1052	=item L<AnyEvent::FastPing>
		1053
		1054	The fastest ping in the west.
		1055
		1056	=item L<AnyEvent::DBI>
		1057
		1058	Executes L<DBI> requests asynchronously in a proxy process.
		1059
		1060	=item L<AnyEvent::AIO>
		1061
		1062	Truly asynchronous I/O, should be in the toolbox of every event
		1063	programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
		1064	together.
		1065
		1066	=item L<AnyEvent::BDB>
		1067
		1068	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
		1069	L<BDB> and AnyEvent together.
		1070
		1071	=item L<AnyEvent::GPSD>
		1072
		1073	A non-blocking interface to gpsd, a daemon delivering GPS information.
		1074
		1075	=item L<AnyEvent::IRC>
		1076
		1077	AnyEvent based IRC client module family (replacing the older Net::IRC3).
		1078
		1079	=item L<AnyEvent::XMPP>
		1080
		1081	AnyEvent based XMPP (Jabber protocol) module family (replacing the older
		1082	Net::XMPP2>.
		1083
		1084	=item L<AnyEvent::IGS>
		1085
		1086	A non-blocking interface to the Internet Go Server protocol (used by
		1087	L<App::IGS>).
		1088
		1089	=item L<Net::FCP>
		1090
		1091	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
		1092	of AnyEvent.
		1093
		1094	=item L<Event::ExecFlow>
		1095
		1096	High level API for event-based execution flow control.
		1097
		1098	=item L<Coro>
		1099
		1100	Has special support for AnyEvent via L<Coro::AnyEvent>.
		1101
		1102	=back
462		1103
463	=cut	1104	=cut
464		1105
465	package AnyEvent;	1106	package AnyEvent;
466		1107
		1108	# basically a tuned-down version of common::sense
		1109	sub common_sense {
467	no warnings;	1110	# no warnings
468	use strict;	1111	${^WARNING_BITS} ^= ${^WARNING_BITS};
		1112	# use strict vars subs
		1113	$^H |= 0x00000600;
		1114	}
469		1115
		1116	BEGIN { AnyEvent::common_sense }
		1117
470	use Carp;	1118	use Carp ();
471		1119
472	our $VERSION = '3.3';	1120	our $VERSION = 4.92;
473	our $MODEL;	1121	our $MODEL;
474		1122
475	our $AUTOLOAD;	1123	our $AUTOLOAD;
476	our @ISA;	1124	our @ISA;
477		1125
478	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
479
480	our @REGISTRY;	1126	our @REGISTRY;
481		1127
		1128	our $WIN32;
		1129
		1130	our $VERBOSE;
		1131
		1132	BEGIN {
		1133	eval "sub WIN32(){ " . (($^O =~ /mswin32/i)*1) ." }";
		1134	eval "sub TAINT(){ " . (${^TAINT}*1) . " }";
		1135
		1136	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1137	if ${^TAINT};
		1138
		1139	$VERBOSE = $ENV{PERL_ANYEVENT_VERBOSE}*1;
		1140
		1141	}
		1142
		1143	our $MAX_SIGNAL_LATENCY = 10;
		1144
		1145	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		1146
		1147	{
		1148	my $idx;
		1149	$PROTOCOL{$_} = ++$idx
		1150	for reverse split /\s*,\s*/,
		1151	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		1152	}
		1153
482	my @models = (	1154	my @models = (
483	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
484	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
485	[EV:: => AnyEvent::Impl::EV::],	1155	[EV:: => AnyEvent::Impl::EV:: , 1],
		1156	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl:: , 1],
		1157	# everything below here will not (normally) be autoprobed
		1158	# as the pureperl backend should work everywhere
		1159	# and is usually faster
486	[Event:: => AnyEvent::Impl::Event::],	1160	[Event:: => AnyEvent::Impl::Event::, 1],
487	[Glib:: => AnyEvent::Impl::Glib::],	1161	[Glib:: => AnyEvent::Impl::Glib:: , 1], # becomes extremely slow with many watchers
		1162	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		1163	[Irssi:: => AnyEvent::Impl::Irssi::], # Irssi has a bogus "Event" package
488	[Tk:: => AnyEvent::Impl::Tk::],	1164	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		1165	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		1166	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
489	[Wx:: => AnyEvent::Impl::POE::],	1167	[Wx:: => AnyEvent::Impl::POE::],
490	[Prima:: => AnyEvent::Impl::POE::],	1168	[Prima:: => AnyEvent::Impl::POE::],
491	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1169	# IO::Async is just too broken - we would need workarounds for its
492	# everything below here will not be autoprobed as the pureperl backend should work everywhere	1170	# byzantine signal and broken child handling, among others.
493	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy	1171	# IO::Async is rather hard to detect, as it doesn't have any
		1172	# obvious default class.
494	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program	1173	[IO::Async:: => AnyEvent::Impl::IOAsync::], # requires special main program
495	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza	1174	[IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1175	[IO::Async::Notifier:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1176	[AnyEvent::Impl::IOAsync:: => AnyEvent::Impl::IOAsync::], # requires special main program
496	);	1177	);
497		1178
498	our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);	1179	our %method = map +($_ => 1),
		1180	qw(io timer time now now_update signal child idle condvar one_event DESTROY);
		1181
		1182	our @post_detect;
		1183
		1184	sub post_detect(&) {
		1185	my ($cb) = @_;
		1186
		1187	if ($MODEL) {
		1188	$cb->();
		1189
		1190	undef
		1191	} else {
		1192	push @post_detect, $cb;
		1193
		1194	defined wantarray
		1195	? bless \$cb, "AnyEvent::Util::postdetect"
		1196	: ()
		1197	}
		1198	}
		1199
		1200	sub AnyEvent::Util::postdetect::DESTROY {
		1201	@post_detect = grep $_ != ${$_[0]}, @post_detect;
		1202	}
499		1203
500	sub detect() {	1204	sub detect() {
501	unless ($MODEL) {	1205	unless ($MODEL) {
502	no strict 'refs';	1206	local $SIG{__DIE__};
503		1207
504	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	1208	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
505	my $model = "AnyEvent::Impl::$1";	1209	my $model = "AnyEvent::Impl::$1";
506	if (eval "require $model") {	1210	if (eval "require $model") {
507	$MODEL = $model;	1211	$MODEL = $model;
508	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	1212	warn "AnyEvent: loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.\n" if $VERBOSE >= 2;
509	} else {	1213	} else {
510	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;	1214	warn "AnyEvent: unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@" if $VERBOSE;
511	}	1215	}
512	}	1216	}
513		1217
514	# check for already loaded models	1218	# check for already loaded models
515	unless ($MODEL) {	1219	unless ($MODEL) {
516	for (@REGISTRY, @models) {	1220	for (@REGISTRY, @models) {
517	my ($package, $model) = @$_;	1221	my ($package, $model) = @$_;
518	if (${"$package\::VERSION"} > 0) {	1222	if (${"$package\::VERSION"} > 0) {
519	if (eval "require $model") {	1223	if (eval "require $model") {
520	$MODEL = $model;	1224	$MODEL = $model;
521	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;	1225	warn "AnyEvent: autodetected model '$model', using it.\n" if $VERBOSE >= 2;
522	last;	1226	last;
523	}	1227	}
524	}	1228	}
525	}	1229	}
526		1230
527	unless ($MODEL) {	1231	unless ($MODEL) {
528	# try to load a model	1232	# try to autoload a model
529
530	for (@REGISTRY, @models) {	1233	for (@REGISTRY, @models) {
531	my ($package, $model) = @$_;	1234	my ($package, $model, $autoload) = @$_;
		1235	if (
		1236	$autoload
532	if (eval "require $package"	1237	and eval "require $package"
533	and ${"$package\::VERSION"} > 0	1238	and ${"$package\::VERSION"} > 0
534	and eval "require $model") {	1239	and eval "require $model"
		1240	) {
535	$MODEL = $model;	1241	$MODEL = $model;
536	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;	1242	warn "AnyEvent: autoloaded model '$model', using it.\n" if $VERBOSE >= 2;
537	last;	1243	last;
538	}	1244	}
539	}	1245	}
540		1246
541	$MODEL	1247	$MODEL
542	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV (or Coro+EV), Event (or Coro+Event) or Glib.";	1248	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.\n";
543	}	1249	}
544	}	1250	}
545		1251
		1252	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		1253
546	unshift @ISA, $MODEL;	1254	unshift @ISA, $MODEL;
547	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	1255
		1256	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
		1257
		1258	(shift @post_detect)->() while @post_detect;
548	}	1259	}
549		1260
550	$MODEL	1261	$MODEL
551	}	1262	}
552		1263
553	sub AUTOLOAD {	1264	sub AUTOLOAD {
554	(my $func = $AUTOLOAD) =~ s/.*://;	1265	(my $func = $AUTOLOAD) =~ s/.*://;
555		1266
556	$method{$func}	1267	$method{$func}
557	or croak "$func: not a valid method for AnyEvent objects";	1268	or Carp::croak "$func: not a valid method for AnyEvent objects";
558		1269
559	detect unless $MODEL;	1270	detect unless $MODEL;
560		1271
561	my $class = shift;	1272	my $class = shift;
562	$class->$func (@_);	1273	$class->$func (@_);
563	}	1274	}
564		1275
		1276	# utility function to dup a filehandle. this is used by many backends
		1277	# to support binding more than one watcher per filehandle (they usually
		1278	# allow only one watcher per fd, so we dup it to get a different one).
		1279	sub _dupfh($$;$$) {
		1280	my ($poll, $fh, $r, $w) = @_;
		1281
		1282	# cygwin requires the fh mode to be matching, unix doesn't
		1283	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1284
		1285	open my $fh2, $mode, $fh
		1286	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1287
		1288	# we assume CLOEXEC is already set by perl in all important cases
		1289
		1290	($fh2, $rw)
		1291	}
		1292
		1293	#############################################################################
		1294	# "new" API, currently only emulation of it
		1295	#############################################################################
		1296
		1297	package AE;
		1298
		1299	our $VERSION = $AnyEvent::VERSION;
		1300
		1301	sub io($$$) {
		1302	AnyEvent->io (fh => $_[0], poll => $_[1] ? "w" : "r", cb => $_[2])
		1303	}
		1304
		1305	sub timer($$$) {
		1306	AnyEvent->timer (after => $_[0], interval => $_[1], cb => $_[2])
		1307	}
		1308
		1309	sub signal($$) {
		1310	AnyEvent->signal (signal => $_[0], cb => $_[1])
		1311	}
		1312
		1313	sub child($$) {
		1314	AnyEvent->child (pid => $_[0], cb => $_[1])
		1315	}
		1316
		1317	sub idle($) {
		1318	AnyEvent->idle (cb => $_[0])
		1319	}
		1320
		1321	sub cv(;&) {
		1322	AnyEvent->condvar (@_ ? (cb => $_[0]) : ())
		1323	}
		1324
		1325	sub now() {
		1326	AnyEvent->now
		1327	}
		1328
		1329	sub now_update() {
		1330	AnyEvent->now_update
		1331	}
		1332
		1333	sub time() {
		1334	AnyEvent->time
		1335	}
		1336
565	package AnyEvent::Base;	1337	package AnyEvent::Base;
566		1338
		1339	# default implementations for many methods
		1340
		1341	sub _time {
		1342	# probe for availability of Time::HiRes
		1343	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1344	warn "AnyEvent: using Time::HiRes for sub-second timing accuracy.\n" if $VERBOSE >= 8;
		1345	*_time = \&Time::HiRes::time;
		1346	# if (eval "use POSIX (); (POSIX::times())...
		1347	} else {
		1348	warn "AnyEvent: using built-in time(), WARNING, no sub-second resolution!\n" if $VERBOSE;
		1349	*_time = sub { time }; # epic fail
		1350	}
		1351
		1352	&_time
		1353	}
		1354
		1355	sub time { _time }
		1356	sub now { _time }
		1357	sub now_update { }
		1358
567	# default implementation for ->condvar, ->wait, ->broadcast	1359	# default implementation for ->condvar
568		1360
569	sub condvar {	1361	sub condvar {
570	bless \my $flag, "AnyEvent::Base::CondVar"	1362	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
571	}
572
573	sub AnyEvent::Base::CondVar::broadcast {
574	${$_[0]}++;
575	}
576
577	sub AnyEvent::Base::CondVar::wait {
578	AnyEvent->one_event while !${$_[0]};
579	}	1363	}
580		1364
581	# default implementation for ->signal	1365	# default implementation for ->signal
582		1366
583	our %SIG_CB;	1367	our $HAVE_ASYNC_INTERRUPT;
		1368
		1369	sub _have_async_interrupt() {
		1370	$HAVE_ASYNC_INTERRUPT = 1*(!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT}
		1371	&& eval "use Async::Interrupt 1.0 (); 1")
		1372	unless defined $HAVE_ASYNC_INTERRUPT;
		1373
		1374	$HAVE_ASYNC_INTERRUPT
		1375	}
		1376
		1377	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1378	our (%SIG_ASY, %SIG_ASY_W);
		1379	our ($SIG_COUNT, $SIG_TW);
		1380
		1381	sub _signal_exec {
		1382	$HAVE_ASYNC_INTERRUPT
		1383	? $SIGPIPE_R->drain
		1384	: sysread $SIGPIPE_R, my $dummy, 9;
		1385
		1386	while (%SIG_EV) {
		1387	for (keys %SIG_EV) {
		1388	delete $SIG_EV{$_};
		1389	$_->() for values %{ $SIG_CB{$_} || {} };
		1390	}
		1391	}
		1392	}
		1393
		1394	# install a dummy wakeup watcher to reduce signal catching latency
		1395	sub _sig_add() {
		1396	unless ($SIG_COUNT++) {
		1397	# try to align timer on a full-second boundary, if possible
		1398	my $NOW = AE::now;
		1399
		1400	$SIG_TW = AE::timer
		1401	$MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1402	$MAX_SIGNAL_LATENCY,
		1403	sub { } # just for the PERL_ASYNC_CHECK
		1404	;
		1405	}
		1406	}
		1407
		1408	sub _sig_del {
		1409	undef $SIG_TW
		1410	unless --$SIG_COUNT;
		1411	}
		1412
		1413	our $_sig_name_init; $_sig_name_init = sub {
		1414	eval q{ # poor man's autoloading
		1415	undef $_sig_name_init;
		1416
		1417	if (_have_async_interrupt) {
		1418	*sig2num = \&Async::Interrupt::sig2num;
		1419	*sig2name = \&Async::Interrupt::sig2name;
		1420	} else {
		1421	require Config;
		1422
		1423	my %signame2num;
		1424	@signame2num{ split ' ', $Config::Config{sig_name} }
		1425	= split ' ', $Config::Config{sig_num};
		1426
		1427	my @signum2name;
		1428	@signum2name[values %signame2num] = keys %signame2num;
		1429
		1430	*sig2num = sub($) {
		1431	$_[0] > 0 ? shift : $signame2num{+shift}
		1432	};
		1433	*sig2name = sub ($) {
		1434	$_[0] > 0 ? $signum2name[+shift] : shift
		1435	};
		1436	}
		1437	};
		1438	die if $@;
		1439	};
		1440
		1441	sub sig2num ($) { &$_sig_name_init; &sig2num }
		1442	sub sig2name($) { &$_sig_name_init; &sig2name }
584		1443
585	sub signal {	1444	sub signal {
		1445	eval q{ # poor man's autoloading {}
		1446	# probe for availability of Async::Interrupt
		1447	if (_have_async_interrupt) {
		1448	warn "AnyEvent: using Async::Interrupt for race-free signal handling.\n" if $VERBOSE >= 8;
		1449
		1450	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1451	$SIG_IO = AE::io $SIGPIPE_R->fileno, 0, \&_signal_exec;
		1452
		1453	} else {
		1454	warn "AnyEvent: using emulated perl signal handling with latency timer.\n" if $VERBOSE >= 8;
		1455
		1456	require Fcntl;
		1457
		1458	if (AnyEvent::WIN32) {
		1459	require AnyEvent::Util;
		1460
		1461	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1462	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R, 1) if $SIGPIPE_R;
		1463	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W, 1) if $SIGPIPE_W; # just in case
		1464	} else {
		1465	pipe $SIGPIPE_R, $SIGPIPE_W;
		1466	fcntl $SIGPIPE_R, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_R;
		1467	fcntl $SIGPIPE_W, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_W; # just in case
		1468
		1469	# not strictly required, as $^F is normally 2, but let's make sure...
		1470	fcntl $SIGPIPE_R, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1471	fcntl $SIGPIPE_W, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1472	}
		1473
		1474	$SIGPIPE_R
		1475	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1476
		1477	$SIG_IO = AE::io $SIGPIPE_R, 0, \&_signal_exec;
		1478	}
		1479
		1480	*signal = sub {
586	my (undef, %arg) = @_;	1481	my (undef, %arg) = @_;
587		1482
588	my $signal = uc $arg{signal}	1483	my $signal = uc $arg{signal}
589	or Carp::croak "required option 'signal' is missing";	1484	or Carp::croak "required option 'signal' is missing";
590		1485
		1486	if ($HAVE_ASYNC_INTERRUPT) {
		1487	# async::interrupt
		1488
		1489	$signal = sig2num $signal;
591	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1490	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1491
		1492	$SIG_ASY{$signal} ||= new Async::Interrupt
		1493	cb => sub { undef $SIG_EV{$signal} },
		1494	signal => $signal,
		1495	pipe => [$SIGPIPE_R->filenos],
		1496	pipe_autodrain => 0,
		1497	;
		1498
		1499	} else {
		1500	# pure perl
		1501
		1502	# AE::Util has been loaded in signal
		1503	$signal = sig2name $signal;
		1504	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1505
592	$SIG{$signal} ||= sub {	1506	$SIG{$signal} ||= sub {
593	$_->() for values %{ $SIG_CB{$signal} || {} };	1507	local $!;
		1508	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1509	undef $SIG_EV{$signal};
		1510	};
		1511
		1512	# can't do signal processing without introducing races in pure perl,
		1513	# so limit the signal latency.
		1514	_sig_add;
		1515	}
		1516
		1517	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1518	};
		1519
		1520	*AnyEvent::Base::signal::DESTROY = sub {
		1521	my ($signal, $cb) = @{$_[0]};
		1522
		1523	_sig_del;
		1524
		1525	delete $SIG_CB{$signal}{$cb};
		1526
		1527	$HAVE_ASYNC_INTERRUPT
		1528	? delete $SIG_ASY{$signal}
		1529	: # delete doesn't work with older perls - they then
		1530	# print weird messages, or just unconditionally exit
		1531	# instead of getting the default action.
		1532	undef $SIG{$signal}
		1533	unless keys %{ $SIG_CB{$signal} };
		1534	};
594	};	1535	};
595		1536	die if $@;
596	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1537	&signal
597	}
598
599	sub AnyEvent::Base::Signal::DESTROY {
600	my ($signal, $cb) = @{$_[0]};
601
602	delete $SIG_CB{$signal}{$cb};
603
604	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };
605	}	1538	}
606		1539
607	# default implementation for ->child	1540	# default implementation for ->child
608		1541
609	our %PID_CB;	1542	our %PID_CB;
610	our $CHLD_W;	1543	our $CHLD_W;
611	our $CHLD_DELAY_W;	1544	our $CHLD_DELAY_W;
612	our $PID_IDLE;
613	our $WNOHANG;	1545	our $WNOHANG;
614		1546
615	sub _child_wait {	1547	sub _emit_childstatus($$) {
616	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1548	my (undef, $rpid, $rstatus) = @_;
		1549
		1550	$_->($rpid, $rstatus)
617	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1551	for values %{ $PID_CB{$rpid} || {} },
618	(values %{ $PID_CB{0} || {} });	1552	values %{ $PID_CB{0} || {} };
619	}
620
621	undef $PID_IDLE;
622	}	1553	}
623		1554
624	sub _sigchld {	1555	sub _sigchld {
625	# make sure we deliver these changes "synchronous" with the event loop.	1556	my $pid;
626	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {	1557
627	undef $CHLD_DELAY_W;	1558	AnyEvent->_emit_childstatus ($pid, $?)
628	&_child_wait;	1559	while ($pid = waitpid -1, $WNOHANG) > 0;
629	});
630	}	1560	}
631		1561
632	sub child {	1562	sub child {
633	my (undef, %arg) = @_;	1563	my (undef, %arg) = @_;
634		1564
635	defined (my $pid = $arg{pid} + 0)	1565	defined (my $pid = $arg{pid} + 0)
636	or Carp::croak "required option 'pid' is missing";	1566	or Carp::croak "required option 'pid' is missing";
637		1567
638	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1568	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
639		1569
640	unless ($WNOHANG) {	1570	# WNOHANG is almost cetrainly 1 everywhere
641	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;	1571	$WNOHANG ||= $^O =~ /^(?:openbsd|netbsd|linux|freebsd|cygwin|MSWin32)$/
642	}	1572	? 1
		1573	: eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
643		1574
644	unless ($CHLD_W) {	1575	unless ($CHLD_W) {
645	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1576	$CHLD_W = AE::signal CHLD => \&_sigchld;
646	# child could be a zombie already, so make at least one round	1577	# child could be a zombie already, so make at least one round
647	&_sigchld;	1578	&_sigchld;
648	}	1579	}
649		1580
650	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	1581	bless [$pid, $arg{cb}], "AnyEvent::Base::child"
651	}	1582	}
652		1583
653	sub AnyEvent::Base::Child::DESTROY {	1584	sub AnyEvent::Base::child::DESTROY {
654	my ($pid, $cb) = @{$_[0]};	1585	my ($pid, $cb) = @{$_[0]};
655		1586
656	delete $PID_CB{$pid}{$cb};	1587	delete $PID_CB{$pid}{$cb};
657	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1588	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
658		1589
659	undef $CHLD_W unless keys %PID_CB;	1590	undef $CHLD_W unless keys %PID_CB;
660	}	1591	}
		1592
		1593	# idle emulation is done by simply using a timer, regardless
		1594	# of whether the process is idle or not, and not letting
		1595	# the callback use more than 50% of the time.
		1596	sub idle {
		1597	my (undef, %arg) = @_;
		1598
		1599	my ($cb, $w, $rcb) = $arg{cb};
		1600
		1601	$rcb = sub {
		1602	if ($cb) {
		1603	$w = _time;
		1604	&$cb;
		1605	$w = _time - $w;
		1606
		1607	# never use more then 50% of the time for the idle watcher,
		1608	# within some limits
		1609	$w = 0.0001 if $w < 0.0001;
		1610	$w = 5 if $w > 5;
		1611
		1612	$w = AE::timer $w, 0, $rcb;
		1613	} else {
		1614	# clean up...
		1615	undef $w;
		1616	undef $rcb;
		1617	}
		1618	};
		1619
		1620	$w = AE::timer 0.05, 0, $rcb;
		1621
		1622	bless \\$cb, "AnyEvent::Base::idle"
		1623	}
		1624
		1625	sub AnyEvent::Base::idle::DESTROY {
		1626	undef $${$_[0]};
		1627	}
		1628
		1629	package AnyEvent::CondVar;
		1630
		1631	our @ISA = AnyEvent::CondVar::Base::;
		1632
		1633	package AnyEvent::CondVar::Base;
		1634
		1635	#use overload
		1636	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1637	# fallback => 1;
		1638
		1639	# save 300+ kilobytes by dirtily hardcoding overloading
		1640	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1641	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1642	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1643	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1644
		1645	our $WAITING;
		1646
		1647	sub _send {
		1648	# nop
		1649	}
		1650
		1651	sub send {
		1652	my $cv = shift;
		1653	$cv->{_ae_sent} = [@_];
		1654	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1655	$cv->_send;
		1656	}
		1657
		1658	sub croak {
		1659	$_[0]{_ae_croak} = $_[1];
		1660	$_[0]->send;
		1661	}
		1662
		1663	sub ready {
		1664	$_[0]{_ae_sent}
		1665	}
		1666
		1667	sub _wait {
		1668	$WAITING
		1669	and !$_[0]{_ae_sent}
		1670	and Carp::croak "AnyEvent::CondVar: recursive blocking wait detected";
		1671
		1672	local $WAITING = 1;
		1673	AnyEvent->one_event while !$_[0]{_ae_sent};
		1674	}
		1675
		1676	sub recv {
		1677	$_[0]->_wait;
		1678
		1679	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
		1680	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
		1681	}
		1682
		1683	sub cb {
		1684	my $cv = shift;
		1685
		1686	@_
		1687	and $cv->{_ae_cb} = shift
		1688	and $cv->{_ae_sent}
		1689	and (delete $cv->{_ae_cb})->($cv);
		1690
		1691	$cv->{_ae_cb}
		1692	}
		1693
		1694	sub begin {
		1695	++$_[0]{_ae_counter};
		1696	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
		1697	}
		1698
		1699	sub end {
		1700	return if --$_[0]{_ae_counter};
		1701	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		1702	}
		1703
		1704	# undocumented/compatibility with pre-3.4
		1705	*broadcast = \&send;
		1706	*wait = \&_wait;
		1707
		1708	=head1 ERROR AND EXCEPTION HANDLING
		1709
		1710	In general, AnyEvent does not do any error handling - it relies on the
		1711	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1712	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1713	checking of all AnyEvent methods, however, which is highly useful during
		1714	development.
		1715
		1716	As for exception handling (i.e. runtime errors and exceptions thrown while
		1717	executing a callback), this is not only highly event-loop specific, but
		1718	also not in any way wrapped by this module, as this is the job of the main
		1719	program.
		1720
		1721	The pure perl event loop simply re-throws the exception (usually
		1722	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1723	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1724	so on.
		1725
		1726	=head1 ENVIRONMENT VARIABLES
		1727
		1728	The following environment variables are used by this module or its
		1729	submodules.
		1730
		1731	Note that AnyEvent will remove I<all> environment variables starting with
		1732	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		1733	enabled.
		1734
		1735	=over 4
		1736
		1737	=item C<PERL_ANYEVENT_VERBOSE>
		1738
		1739	By default, AnyEvent will be completely silent except in fatal
		1740	conditions. You can set this environment variable to make AnyEvent more
		1741	talkative.
		1742
		1743	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1744	conditions, such as not being able to load the event model specified by
		1745	C<PERL_ANYEVENT_MODEL>.
		1746
		1747	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1748	model it chooses.
		1749
		1750	When set to C<8> or higher, then AnyEvent will report extra information on
		1751	which optional modules it loads and how it implements certain features.
		1752
		1753	=item C<PERL_ANYEVENT_STRICT>
		1754
		1755	AnyEvent does not do much argument checking by default, as thorough
		1756	argument checking is very costly. Setting this variable to a true value
		1757	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1758	check the arguments passed to most method calls. If it finds any problems,
		1759	it will croak.
		1760
		1761	In other words, enables "strict" mode.
		1762
		1763	Unlike C<use strict> (or it's modern cousin, C<< use L<common::sense>
		1764	>>, it is definitely recommended to keep it off in production. Keeping
		1765	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		1766	can be very useful, however.
		1767
		1768	=item C<PERL_ANYEVENT_MODEL>
		1769
		1770	This can be used to specify the event model to be used by AnyEvent, before
		1771	auto detection and -probing kicks in. It must be a string consisting
		1772	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1773	and the resulting module name is loaded and if the load was successful,
		1774	used as event model. If it fails to load AnyEvent will proceed with
		1775	auto detection and -probing.
		1776
		1777	This functionality might change in future versions.
		1778
		1779	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1780	could start your program like this:
		1781
		1782	PERL_ANYEVENT_MODEL=Perl perl ...
		1783
		1784	=item C<PERL_ANYEVENT_PROTOCOLS>
		1785
		1786	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1787	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1788	of auto probing).
		1789
		1790	Must be set to a comma-separated list of protocols or address families,
		1791	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1792	used, and preference will be given to protocols mentioned earlier in the
		1793	list.
		1794
		1795	This variable can effectively be used for denial-of-service attacks
		1796	against local programs (e.g. when setuid), although the impact is likely
		1797	small, as the program has to handle conenction and other failures anyways.
		1798
		1799	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1800	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1801	- only support IPv4, never try to resolve or contact IPv6
		1802	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1803	IPv6, but prefer IPv6 over IPv4.
		1804
		1805	=item C<PERL_ANYEVENT_EDNS0>
		1806
		1807	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1808	for DNS. This extension is generally useful to reduce DNS traffic, but
		1809	some (broken) firewalls drop such DNS packets, which is why it is off by
		1810	default.
		1811
		1812	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1813	EDNS0 in its DNS requests.
		1814
		1815	=item C<PERL_ANYEVENT_MAX_FORKS>
		1816
		1817	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1818	will create in parallel.
		1819
		1820	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		1821
		1822	The default value for the C<max_outstanding> parameter for the default DNS
		1823	resolver - this is the maximum number of parallel DNS requests that are
		1824	sent to the DNS server.
		1825
		1826	=item C<PERL_ANYEVENT_RESOLV_CONF>
		1827
		1828	The file to use instead of F</etc/resolv.conf> (or OS-specific
		1829	configuration) in the default resolver. When set to the empty string, no
		1830	default config will be used.
		1831
		1832	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		1833
		1834	When neither C<ca_file> nor C<ca_path> was specified during
		1835	L<AnyEvent::TLS> context creation, and either of these environment
		1836	variables exist, they will be used to specify CA certificate locations
		1837	instead of a system-dependent default.
		1838
		1839	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		1840
		1841	When these are set to C<1>, then the respective modules are not
		1842	loaded. Mostly good for testing AnyEvent itself.
		1843
		1844	=back
661		1845
662	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1846	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
663		1847
664	This is an advanced topic that you do not normally need to use AnyEvent in	1848	This is an advanced topic that you do not normally need to use AnyEvent in
665	a module. This section is only of use to event loop authors who want to	1849	a module. This section is only of use to event loop authors who want to
…		…
699		1883
700	I<rxvt-unicode> also cheats a bit by not providing blocking access to	1884	I<rxvt-unicode> also cheats a bit by not providing blocking access to
701	condition variables: code blocking while waiting for a condition will	1885	condition variables: code blocking while waiting for a condition will
702	C<die>. This still works with most modules/usages, and blocking calls must	1886	C<die>. This still works with most modules/usages, and blocking calls must
703	not be done in an interactive application, so it makes sense.	1887	not be done in an interactive application, so it makes sense.
704
705	=head1 ENVIRONMENT VARIABLES
706
707	The following environment variables are used by this module:
708
709	=over 4
710
711	=item C<PERL_ANYEVENT_VERBOSE>
712
713	By default, AnyEvent will be completely silent except in fatal
714	conditions. You can set this environment variable to make AnyEvent more
715	talkative.
716
717	When set to C<1> or higher, causes AnyEvent to warn about unexpected
718	conditions, such as not being able to load the event model specified by
719	C<PERL_ANYEVENT_MODEL>.
720
721	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
722	model it chooses.
723
724	=item C<PERL_ANYEVENT_MODEL>
725
726	This can be used to specify the event model to be used by AnyEvent, before
727	autodetection and -probing kicks in. It must be a string consisting
728	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
729	and the resulting module name is loaded and if the load was successful,
730	used as event model. If it fails to load AnyEvent will proceed with
731	autodetection and -probing.
732
733	This functionality might change in future versions.
734
735	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
736	could start your program like this:
737
738	PERL_ANYEVENT_MODEL=Perl perl ...
739
740	=back
741		1888
742	=head1 EXAMPLE PROGRAM	1889	=head1 EXAMPLE PROGRAM
743		1890
744	The following program uses an I/O watcher to read data from STDIN, a timer	1891	The following program uses an I/O watcher to read data from STDIN, a timer
745	to display a message once per second, and a condition variable to quit the	1892	to display a message once per second, and a condition variable to quit the
…		…
754	poll => 'r',	1901	poll => 'r',
755	cb => sub {	1902	cb => sub {
756	warn "io event <$_[0]>\n"; # will always output <r>	1903	warn "io event <$_[0]>\n"; # will always output <r>
757	chomp (my $input = <STDIN>); # read a line	1904	chomp (my $input = <STDIN>); # read a line
758	warn "read: $input\n"; # output what has been read	1905	warn "read: $input\n"; # output what has been read
759	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	1906	$cv->send if $input =~ /^q/i; # quit program if /^q/i
760	},	1907	},
761	);	1908	);
762		1909
763	my $time_watcher; # can only be used once	1910	my $time_watcher; # can only be used once
764		1911
…		…
769	});	1916	});
770	}	1917	}
771		1918
772	new_timer; # create first timer	1919	new_timer; # create first timer
773		1920
774	$cv->wait; # wait until user enters /^q/i	1921	$cv->recv; # wait until user enters /^q/i
775		1922
776	=head1 REAL-WORLD EXAMPLE	1923	=head1 REAL-WORLD EXAMPLE
777		1924
778	Consider the L<Net::FCP> module. It features (among others) the following	1925	Consider the L<Net::FCP> module. It features (among others) the following
779	API calls, which are to freenet what HTTP GET requests are to http:	1926	API calls, which are to freenet what HTTP GET requests are to http:
…		…
829	syswrite $txn->{fh}, $txn->{request}	1976	syswrite $txn->{fh}, $txn->{request}
830	or die "connection or write error";	1977	or die "connection or write error";
831	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	1978	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
832		1979
833	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	1980	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
834	result and signals any possible waiters that the request ahs finished:	1981	result and signals any possible waiters that the request has finished:
835		1982
836	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	1983	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
837		1984
838	if (end-of-file or data complete) {	1985	if (end-of-file or data complete) {
839	$txn->{result} = $txn->{buf};	1986	$txn->{result} = $txn->{buf};
840	$txn->{finished}->broadcast;	1987	$txn->{finished}->send;
841	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	1988	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
842	}	1989	}
843		1990
844	The C<result> method, finally, just waits for the finished signal (if the	1991	The C<result> method, finally, just waits for the finished signal (if the
845	request was already finished, it doesn't wait, of course, and returns the	1992	request was already finished, it doesn't wait, of course, and returns the
846	data:	1993	data:
847		1994
848	$txn->{finished}->wait;	1995	$txn->{finished}->recv;
849	return $txn->{result};	1996	return $txn->{result};
850		1997
851	The actual code goes further and collects all errors (C<die>s, exceptions)	1998	The actual code goes further and collects all errors (C<die>s, exceptions)
852	that occured during request processing. The C<result> method detects	1999	that occurred during request processing. The C<result> method detects
853	whether an exception as thrown (it is stored inside the $txn object)	2000	whether an exception as thrown (it is stored inside the $txn object)
854	and just throws the exception, which means connection errors and other	2001	and just throws the exception, which means connection errors and other
855	problems get reported tot he code that tries to use the result, not in a	2002	problems get reported tot he code that tries to use the result, not in a
856	random callback.	2003	random callback.
857		2004
…		…
888		2035
889	my $quit = AnyEvent->condvar;	2036	my $quit = AnyEvent->condvar;
890		2037
891	$fcp->txn_client_get ($url)->cb (sub {	2038	$fcp->txn_client_get ($url)->cb (sub {
892	...	2039	...
893	$quit->broadcast;	2040	$quit->send;
894	});	2041	});
895		2042
896	$quit->wait;	2043	$quit->recv;
897		2044
898		2045
899	=head1 BENCHMARKS	2046	=head1 BENCHMARKS
900		2047
901	To give you an idea of the performance and overheads that AnyEvent adds	2048	To give you an idea of the performance and overheads that AnyEvent adds
…		…
903	of various event loops I prepared some benchmarks.	2050	of various event loops I prepared some benchmarks.
904		2051
905	=head2 BENCHMARKING ANYEVENT OVERHEAD	2052	=head2 BENCHMARKING ANYEVENT OVERHEAD
906		2053
907	Here is a benchmark of various supported event models used natively and	2054	Here is a benchmark of various supported event models used natively and
908	through anyevent. The benchmark creates a lot of timers (with a zero	2055	through AnyEvent. The benchmark creates a lot of timers (with a zero
909	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,	2056	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
910	which it is), lets them fire exactly once and destroys them again.	2057	which it is), lets them fire exactly once and destroys them again.
911		2058
912	Source code for this benchmark is found as F<eg/bench> in the AnyEvent	2059	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
913	distribution.	2060	distribution.
…		…
930	all watchers, to avoid adding memory overhead. That means closure creation	2077	all watchers, to avoid adding memory overhead. That means closure creation
931	and memory usage is not included in the figures.	2078	and memory usage is not included in the figures.
932		2079
933	I<invoke> is the time, in microseconds, used to invoke a simple	2080	I<invoke> is the time, in microseconds, used to invoke a simple
934	callback. The callback simply counts down a Perl variable and after it was	2081	callback. The callback simply counts down a Perl variable and after it was
935	invoked "watcher" times, it would C<< ->broadcast >> a condvar once to	2082	invoked "watcher" times, it would C<< ->send >> a condvar once to
936	signal the end of this phase.	2083	signal the end of this phase.
937		2084
938	I<destroy> is the time, in microseconds, that it takes to destroy a single	2085	I<destroy> is the time, in microseconds, that it takes to destroy a single
939	watcher.	2086	watcher.
940		2087
941	=head3 Results	2088	=head3 Results
942		2089
943	name watchers bytes create invoke destroy comment	2090	name watchers bytes create invoke destroy comment
944	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	2091	EV/EV 400000 224 0.47 0.35 0.27 EV native interface
945	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	2092	EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers
946	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	2093	CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal
947	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	2094	Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation
948	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	2095	Event/Event 16000 517 32.20 31.80 0.81 Event native interface
949	Event/Any 16000 936 39.17 33.63 1.43 Event + AnyEvent watchers	2096	Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers
		2097	IOAsync/Any 16000 989 38.10 32.77 11.13 via IO::Async::Loop::IO_Poll
		2098	IOAsync/Any 16000 990 37.59 29.50 10.61 via IO::Async::Loop::Epoll
950	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	2099	Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour
951	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	2100	Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers
952	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	2101	POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event
953	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	2102	POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select
954		2103
955	=head3 Discussion	2104	=head3 Discussion
956		2105
957	The benchmark does I<not> measure scalability of the event loop very	2106	The benchmark does I<not> measure scalability of the event loop very
958	well. For example, a select-based event loop (such as the pure perl one)	2107	well. For example, a select-based event loop (such as the pure perl one)
959	can never compete with an event loop that uses epoll when the number of	2108	can never compete with an event loop that uses epoll when the number of
960	file descriptors grows high. In this benchmark, all events become ready at	2109	file descriptors grows high. In this benchmark, all events become ready at
961	the same time, so select/poll-based implementations get an unnatural speed	2110	the same time, so select/poll-based implementations get an unnatural speed
962	boost.	2111	boost.
963		2112
		2113	Also, note that the number of watchers usually has a nonlinear effect on
		2114	overall speed, that is, creating twice as many watchers doesn't take twice
		2115	the time - usually it takes longer. This puts event loops tested with a
		2116	higher number of watchers at a disadvantage.
		2117
		2118	To put the range of results into perspective, consider that on the
		2119	benchmark machine, handling an event takes roughly 1600 CPU cycles with
		2120	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
		2121	cycles with POE.
		2122
964	C<EV> is the sole leader regarding speed and memory use, which are both	2123	C<EV> is the sole leader regarding speed and memory use, which are both
965	maximal/minimal, respectively. Even when going through AnyEvent, it uses	2124	maximal/minimal, respectively. Even when going through AnyEvent, it uses
966	far less memory than any other event loop and is still faster than Event	2125	far less memory than any other event loop and is still faster than Event
967	natively.	2126	natively.
968		2127
…		…
973	performance becomes really bad with lots of file descriptors (and few of	2132	performance becomes really bad with lots of file descriptors (and few of
974	them active), of course, but this was not subject of this benchmark.	2133	them active), of course, but this was not subject of this benchmark.
975		2134
976	The C<Event> module has a relatively high setup and callback invocation	2135	The C<Event> module has a relatively high setup and callback invocation
977	cost, but overall scores in on the third place.	2136	cost, but overall scores in on the third place.
		2137
		2138	C<IO::Async> performs admirably well, about on par with C<Event>, even
		2139	when using its pure perl backend.
978		2140
979	C<Glib>'s memory usage is quite a bit higher, but it features a	2141	C<Glib>'s memory usage is quite a bit higher, but it features a
980	faster callback invocation and overall ends up in the same class as	2142	faster callback invocation and overall ends up in the same class as
981	C<Event>. However, Glib scales extremely badly, doubling the number of	2143	C<Event>. However, Glib scales extremely badly, doubling the number of
982	watchers increases the processing time by more than a factor of four,	2144	watchers increases the processing time by more than a factor of four,
…		…
990	file descriptor is dup()ed for each watcher. This shows that the dup()	2152	file descriptor is dup()ed for each watcher. This shows that the dup()
991	employed by some adaptors is not a big performance issue (it does incur a	2153	employed by some adaptors is not a big performance issue (it does incur a
992	hidden memory cost inside the kernel which is not reflected in the figures	2154	hidden memory cost inside the kernel which is not reflected in the figures
993	above).	2155	above).
994		2156
995	C<POE>, regardless of underlying event loop (whether using its pure	2157	C<POE>, regardless of underlying event loop (whether using its pure perl
996	perl select-based backend or the Event module, the POE-EV backend	2158	select-based backend or the Event module, the POE-EV backend couldn't
997	couldn't be tested because it wasn't working) shows abysmal performance	2159	be tested because it wasn't working) shows abysmal performance and
998	and memory usage: Watchers use almost 30 times as much memory as	2160	memory usage with AnyEvent: Watchers use almost 30 times as much memory
999	EV watchers, and 10 times as much memory as Event (the high memory	2161	as EV watchers, and 10 times as much memory as Event (the high memory
1000	requirements are caused by requiring a session for each watcher). Watcher	2162	requirements are caused by requiring a session for each watcher). Watcher
1001	invocation speed is almost 900 times slower than with AnyEvent's pure perl	2163	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		2164	implementation.
		2165
1002	implementation. The design of the POE adaptor class in AnyEvent can not	2166	The design of the POE adaptor class in AnyEvent can not really account
1003	really account for this, as session creation overhead is small compared	2167	for the performance issues, though, as session creation overhead is
1004	to execution of the state machine, which is coded pretty optimally within	2168	small compared to execution of the state machine, which is coded pretty
1005	L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow.	2169	optimally within L<AnyEvent::Impl::POE> (and while everybody agrees that
		2170	using multiple sessions is not a good approach, especially regarding
		2171	memory usage, even the author of POE could not come up with a faster
		2172	design).
1006		2173
1007	=head3 Summary	2174	=head3 Summary
1008		2175
1009	=over 4	2176	=over 4
1010		2177
…		…
1021		2188
1022	=back	2189	=back
1023		2190
1024	=head2 BENCHMARKING THE LARGE SERVER CASE	2191	=head2 BENCHMARKING THE LARGE SERVER CASE
1025		2192
1026	This benchmark atcually benchmarks the event loop itself. It works by	2193	This benchmark actually benchmarks the event loop itself. It works by
1027	creating a number of "servers": each server consists of a socketpair, a	2194	creating a number of "servers": each server consists of a socket pair, a
1028	timeout watcher that gets reset on activity (but never fires), and an I/O	2195	timeout watcher that gets reset on activity (but never fires), and an I/O
1029	watcher waiting for input on one side of the socket. Each time the socket	2196	watcher waiting for input on one side of the socket. Each time the socket
1030	watcher reads a byte it will write that byte to a random other "server".	2197	watcher reads a byte it will write that byte to a random other "server".
1031		2198
1032	The effect is that there will be a lot of I/O watchers, only part of which	2199	The effect is that there will be a lot of I/O watchers, only part of which
1033	are active at any one point (so there is a constant number of active	2200	are active at any one point (so there is a constant number of active
1034	fds for each loop iterstaion, but which fds these are is random). The	2201	fds for each loop iteration, but which fds these are is random). The
1035	timeout is reset each time something is read because that reflects how	2202	timeout is reset each time something is read because that reflects how
1036	most timeouts work (and puts extra pressure on the event loops).	2203	most timeouts work (and puts extra pressure on the event loops).
1037		2204
1038	In this benchmark, we use 10000 socketpairs (20000 sockets), of which 100	2205	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
1039	(1%) are active. This mirrors the activity of large servers with many	2206	(1%) are active. This mirrors the activity of large servers with many
1040	connections, most of which are idle at any one point in time.	2207	connections, most of which are idle at any one point in time.
1041		2208
1042	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent	2209	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
1043	distribution.	2210	distribution.
1044		2211
1045	=head3 Explanation of the columns	2212	=head3 Explanation of the columns
1046		2213
1047	I<sockets> is the number of sockets, and twice the number of "servers" (as	2214	I<sockets> is the number of sockets, and twice the number of "servers" (as
1048	eahc server has a read and write socket end).	2215	each server has a read and write socket end).
1049		2216
1050	I<create> is the time it takes to create a socketpair (which is	2217	I<create> is the time it takes to create a socket pair (which is
1051	nontrivial) and two watchers: an I/O watcher and a timeout watcher.	2218	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
1052		2219
1053	I<request>, the most important value, is the time it takes to handle a	2220	I<request>, the most important value, is the time it takes to handle a
1054	single "request", that is, reading the token from the pipe and forwarding	2221	single "request", that is, reading the token from the pipe and forwarding
1055	it to another server. This includes deleteing the old timeout and creating	2222	it to another server. This includes deleting the old timeout and creating
1056	a new one with a later timeout.	2223	a new one that moves the timeout into the future.
1057		2224
1058	=head3 Results	2225	=head3 Results
1059		2226
1060	name sockets create request	2227	name sockets create request
1061	EV 20000 69.01 11.16	2228	EV 20000 69.01 11.16
1062	Perl 20000 75.28 112.76	2229	Perl 20000 73.32 35.87
		2230	IOAsync 20000 157.00 98.14 epoll
		2231	IOAsync 20000 159.31 616.06 poll
1063	Event 20000 212.62 257.32	2232	Event 20000 212.62 257.32
1064	Glib 20000 651.16 1896.30	2233	Glib 20000 651.16 1896.30
1065	POE 20000 349.67 12317.24 uses POE::Loop::Event	2234	POE 20000 349.67 12317.24 uses POE::Loop::Event
1066		2235
1067	=head3 Discussion	2236	=head3 Discussion
1068		2237
1069	This benchmark I<does> measure scalability and overall performance of the	2238	This benchmark I<does> measure scalability and overall performance of the
1070	particular event loop.	2239	particular event loop.
…		…
1072	EV is again fastest. Since it is using epoll on my system, the setup time	2241	EV is again fastest. Since it is using epoll on my system, the setup time
1073	is relatively high, though.	2242	is relatively high, though.
1074		2243
1075	Perl surprisingly comes second. It is much faster than the C-based event	2244	Perl surprisingly comes second. It is much faster than the C-based event
1076	loops Event and Glib.	2245	loops Event and Glib.
		2246
		2247	IO::Async performs very well when using its epoll backend, and still quite
		2248	good compared to Glib when using its pure perl backend.
1077		2249
1078	Event suffers from high setup time as well (look at its code and you will	2250	Event suffers from high setup time as well (look at its code and you will
1079	understand why). Callback invocation also has a high overhead compared to	2251	understand why). Callback invocation also has a high overhead compared to
1080	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event	2252	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
1081	uses select or poll in basically all documented configurations.	2253	uses select or poll in basically all documented configurations.
…		…
1089		2261
1090	=head3 Summary	2262	=head3 Summary
1091		2263
1092	=over 4	2264	=over 4
1093		2265
1094	=item * The pure perl implementation performs extremely well, considering	2266	=item * The pure perl implementation performs extremely well.
1095	that it uses select.
1096		2267
1097	=item * Avoid Glib or POE in large projects where performance matters.	2268	=item * Avoid Glib or POE in large projects where performance matters.
1098		2269
1099	=back	2270	=back
1100		2271
…		…
1113		2284
1114	=head3 Results	2285	=head3 Results
1115		2286
1116	name sockets create request	2287	name sockets create request
1117	EV 16 20.00 6.54	2288	EV 16 20.00 6.54
		2289	Perl 16 25.75 12.62
1118	Event 16 81.27 35.86	2290	Event 16 81.27 35.86
1119	Glib 16 32.63 15.48	2291	Glib 16 32.63 15.48
1120	Perl 16 24.62 162.37
1121	POE 16 261.87 276.28 uses POE::Loop::Event	2292	POE 16 261.87 276.28 uses POE::Loop::Event
1122		2293
1123	=head3 Discussion	2294	=head3 Discussion
1124		2295
1125	The benchmark tries to test the performance of a typical small	2296	The benchmark tries to test the performance of a typical small
1126	server. While knowing how various event loops perform is interesting, keep	2297	server. While knowing how various event loops perform is interesting, keep
1127	in mind that their overhead in this case is usually not as important, due	2298	in mind that their overhead in this case is usually not as important, due
1128	to the small absolute number of watchers.	2299	to the small absolute number of watchers (that is, you need efficiency and
		2300	speed most when you have lots of watchers, not when you only have a few of
		2301	them).
1129		2302
1130	EV is again fastest.	2303	EV is again fastest.
1131		2304
1132	The C-based event loops Event and Glib come in second this time, as the	2305	Perl again comes second. It is noticeably faster than the C-based event
1133	overhead of running an iteration is much smaller in C than in Perl (little	2306	loops Event and Glib, although the difference is too small to really
1134	code to execute in the inner loop, and perl's function calling overhead is	2307	matter.
1135	high, and updating all the data structures is costly).
1136		2308
1137	The pure perl event loop is much slower, but still competitive.
1138
1139	POE also performs much better in this case, but is is stillf ar behind the	2309	POE also performs much better in this case, but is is still far behind the
1140	others.	2310	others.
1141		2311
1142	=head3 Summary	2312	=head3 Summary
1143		2313
1144	=over 4	2314	=over 4
…		…
1146	=item * C-based event loops perform very well with small number of	2316	=item * C-based event loops perform very well with small number of
1147	watchers, as the management overhead dominates.	2317	watchers, as the management overhead dominates.
1148		2318
1149	=back	2319	=back
1150		2320
		2321	=head2 THE IO::Lambda BENCHMARK
		2322
		2323	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2324	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2325	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2326	shouldn't come as a surprise to anybody). As such, the benchmark is
		2327	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2328	very optimal. But how would AnyEvent compare when used without the extra
		2329	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2330
		2331	The benchmark itself creates an echo-server, and then, for 500 times,
		2332	connects to the echo server, sends a line, waits for the reply, and then
		2333	creates the next connection. This is a rather bad benchmark, as it doesn't
		2334	test the efficiency of the framework or much non-blocking I/O, but it is a
		2335	benchmark nevertheless.
		2336
		2337	name runtime
		2338	Lambda/select 0.330 sec
		2339	+ optimized 0.122 sec
		2340	Lambda/AnyEvent 0.327 sec
		2341	+ optimized 0.138 sec
		2342	Raw sockets/select 0.077 sec
		2343	POE/select, components 0.662 sec
		2344	POE/select, raw sockets 0.226 sec
		2345	POE/select, optimized 0.404 sec
		2346
		2347	AnyEvent/select/nb 0.085 sec
		2348	AnyEvent/EV/nb 0.068 sec
		2349	+state machine 0.134 sec
		2350
		2351	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2352	benchmarks actually make blocking connects and use 100% blocking I/O,
		2353	defeating the purpose of an event-based solution. All of the newly
		2354	written AnyEvent benchmarks use 100% non-blocking connects (using
		2355	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2356	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2357	generally require a lot more bookkeeping and event handling than blocking
		2358	connects (which involve a single syscall only).
		2359
		2360	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2361	offers similar expressive power as POE and IO::Lambda, using conventional
		2362	Perl syntax. This means that both the echo server and the client are 100%
		2363	non-blocking, further placing it at a disadvantage.
		2364
		2365	As you can see, the AnyEvent + EV combination even beats the
		2366	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2367	backend easily beats IO::Lambda and POE.
		2368
		2369	And even the 100% non-blocking version written using the high-level (and
		2370	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda by a
		2371	large margin, even though it does all of DNS, tcp-connect and socket I/O
		2372	in a non-blocking way.
		2373
		2374	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2375	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2376	part of the IO::lambda distribution and were used without any changes.
		2377
		2378
		2379	=head1 SIGNALS
		2380
		2381	AnyEvent currently installs handlers for these signals:
		2382
		2383	=over 4
		2384
		2385	=item SIGCHLD
		2386
		2387	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2388	emulation for event loops that do not support them natively. Also, some
		2389	event loops install a similar handler.
		2390
		2391	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2392	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2393
		2394	=item SIGPIPE
		2395
		2396	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2397	when AnyEvent gets loaded.
		2398
		2399	The rationale for this is that AnyEvent users usually do not really depend
		2400	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2401	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2402	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2403	some random socket.
		2404
		2405	The rationale for installing a no-op handler as opposed to ignoring it is
		2406	that this way, the handler will be restored to defaults on exec.
		2407
		2408	Feel free to install your own handler, or reset it to defaults.
		2409
		2410	=back
		2411
		2412	=cut
		2413
		2414	undef $SIG{CHLD}
		2415	if $SIG{CHLD} eq 'IGNORE';
		2416
		2417	$SIG{PIPE} = sub { }
		2418	unless defined $SIG{PIPE};
		2419
		2420	=head1 RECOMMENDED/OPTIONAL MODULES
		2421
		2422	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2423	it's built-in modules) are required to use it.
		2424
		2425	That does not mean that AnyEvent won't take advantage of some additional
		2426	modules if they are installed.
		2427
		2428	This section epxlains which additional modules will be used, and how they
		2429	affect AnyEvent's operetion.
		2430
		2431	=over 4
		2432
		2433	=item L<Async::Interrupt>
		2434
		2435	This slightly arcane module is used to implement fast signal handling: To
		2436	my knowledge, there is no way to do completely race-free and quick
		2437	signal handling in pure perl. To ensure that signals still get
		2438	delivered, AnyEvent will start an interval timer to wake up perl (and
		2439	catch the signals) with some delay (default is 10 seconds, look for
		2440	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2441
		2442	If this module is available, then it will be used to implement signal
		2443	catching, which means that signals will not be delayed, and the event loop
		2444	will not be interrupted regularly, which is more efficient (And good for
		2445	battery life on laptops).
		2446
		2447	This affects not just the pure-perl event loop, but also other event loops
		2448	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2449
		2450	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2451	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2452	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2453	does nothing for those backends.
		2454
		2455	=item L<EV>
		2456
		2457	This module isn't really "optional", as it is simply one of the backend
		2458	event loops that AnyEvent can use. However, it is simply the best event
		2459	loop available in terms of features, speed and stability: It supports
		2460	the AnyEvent API optimally, implements all the watcher types in XS, does
		2461	automatic timer adjustments even when no monotonic clock is available,
		2462	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2463	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2464	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2465
		2466	=item L<Guard>
		2467
		2468	The guard module, when used, will be used to implement
		2469	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2470	lot less memory), but otherwise doesn't affect guard operation much. It is
		2471	purely used for performance.
		2472
		2473	=item L<JSON> and L<JSON::XS>
		2474
		2475	This module is required when you want to read or write JSON data via
		2476	L<AnyEvent::Handle>. It is also written in pure-perl, but can take
		2477	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2478
		2479	In fact, L<AnyEvent::Handle> will use L<JSON::XS> by default if it is
		2480	installed.
		2481
		2482	=item L<Net::SSLeay>
		2483
		2484	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2485	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2486	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2487
		2488	=item L<Time::HiRes>
		2489
		2490	This module is part of perl since release 5.008. It will be used when the
		2491	chosen event library does not come with a timing source on it's own. The
		2492	pure-perl event loop (L<AnyEvent::Impl::Perl>) will additionally use it to
		2493	try to use a monotonic clock for timing stability.
		2494
		2495	=back
		2496
1151		2497
1152	=head1 FORK	2498	=head1 FORK
1153		2499
1154	Most event libraries are not fork-safe. The ones who are usually are	2500	Most event libraries are not fork-safe. The ones who are usually are
1155	because they are so inefficient. Only L<EV> is fully fork-aware.	2501	because they rely on inefficient but fork-safe C<select> or C<poll>
		2502	calls. Only L<EV> is fully fork-aware.
1156		2503
1157	If you have to fork, you must either do so I<before> creating your first	2504	If you have to fork, you must either do so I<before> creating your first
1158	watcher OR you must not use AnyEvent at all in the child.	2505	watcher OR you must not use AnyEvent at all in the child OR you must do
		2506	something completely out of the scope of AnyEvent.
1159		2507
1160		2508
1161	=head1 SECURITY CONSIDERATIONS	2509	=head1 SECURITY CONSIDERATIONS
1162		2510
1163	AnyEvent can be forced to load any event model via	2511	AnyEvent can be forced to load any event model via
…		…
1168	specified in the variable.	2516	specified in the variable.
1169		2517
1170	You can make AnyEvent completely ignore this variable by deleting it	2518	You can make AnyEvent completely ignore this variable by deleting it
1171	before the first watcher gets created, e.g. with a C<BEGIN> block:	2519	before the first watcher gets created, e.g. with a C<BEGIN> block:
1172		2520
1173	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	2521	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1174		2522
1175	use AnyEvent;	2523	use AnyEvent;
		2524
		2525	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
		2526	be used to probe what backend is used and gain other information (which is
		2527	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2528	$ENV{PERL_ANYEVENT_STRICT}.
		2529
		2530	Note that AnyEvent will remove I<all> environment variables starting with
		2531	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2532	enabled.
		2533
		2534
		2535	=head1 BUGS
		2536
		2537	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2538	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2539	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2540	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2541	pronounced).
1176		2542
1177		2543
1178	=head1 SEE ALSO	2544	=head1 SEE ALSO
1179		2545
1180	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,	2546	Utility functions: L<AnyEvent::Util>.
1181	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,	2547
		2548	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
1182	L<Event::Lib>, L<Qt>, L<POE>.	2549	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
1183		2550
1184	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,	2551	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
		2552	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
		2553	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1185	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,	2554	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>, L<Anyevent::Impl::Irssi>.
1186	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,
1187	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.
1188		2555
		2556	Non-blocking file handles, sockets, TCP clients and
		2557	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
		2558
		2559	Asynchronous DNS: L<AnyEvent::DNS>.
		2560
		2561	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>,
		2562	L<Coro::Event>,
		2563
1189	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	2564	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::XMPP>,
		2565	L<AnyEvent::HTTP>.
1190		2566
1191		2567
1192	=head1 AUTHOR	2568	=head1 AUTHOR
1193		2569
1194	Marc Lehmann <schmorp@schmorp.de>	2570	Marc Lehmann <schmorp@schmorp.de>
1195	http://home.schmorp.de/	2571	http://home.schmorp.de/
1196		2572
1197	=cut	2573	=cut
1198		2574
1199	1	2575	1
1200		2576

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