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Revision 1.126 by root, Fri May 23 23:44:55 2008 UTC vs.
Revision 1.304 by root, Fri Dec 11 18:09:24 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, 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
20	$w->send; # wake up current and all future recv's	35	$w->send; # wake up current and all future recv's
21	$w->recv; # enters "main loop" till $condvar gets ->send	36	$w->recv; # enters "main loop" till $condvar gets ->send
		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		108
71	=head1 DESCRIPTION	109	=head1 DESCRIPTION
72		110
…		…
102	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
103	use AnyEvent so their modules work together with others seamlessly...	141	use AnyEvent so their modules work together with others seamlessly...
104		142
105	The pure-perl implementation of AnyEvent is called	143	The pure-perl implementation of AnyEvent is called
106	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
107	explicitly.	145	explicitly and enjoy the high availability of that event loop :)
108		146
109	=head1 WATCHERS	147	=head1 WATCHERS
110		148
111	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
112	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
113	the callback to call, the filehandle to watch, etc.	151	the callback to call, the file handle to watch, etc.
114		152
115	These watchers are normal Perl objects with normal Perl lifetime. After	153	These watchers are normal Perl objects with normal Perl lifetime. After
116	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
117	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
118	is in control).	156	is in control).
119		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
120	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
121	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
122	to it).	166	to it).
123		167
124	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.
…		…
126	Many watchers either are used with "recursion" (repeating timers for	170	Many watchers either are used with "recursion" (repeating timers for
127	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.
128		172
129	An any way to achieve that is this pattern:	173	An any way to achieve that is this pattern:
130		174
131	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	175	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
132	# you can use $w here, for example to undef it	176	# you can use $w here, for example to undef it
133	undef $w;	177	undef $w;
134	});	178	});
135		179
136	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,
137	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
138	declared.	182	declared.
139		183
140	=head2 I/O WATCHERS	184	=head2 I/O WATCHERS
141		185
		186	$w = AnyEvent->io (
		187	fh => <filehandle_or_fileno>,
		188	poll => <"r" or "w">,
		189	cb => <callback>,
		190	);
		191
142	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
143	with the following mandatory key-value pairs as arguments:	193	with the following mandatory key-value pairs as arguments:
144		194
145	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
146	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
147	which creates a watcher waiting for "r"eadable or "w"ritable events,	203	watcher waiting for "r"eadable or "w"ritable events, respectively.
		204
148	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.
149	becomes ready.
150		206
151	Although the callback might get passed parameters, their value and	207	Although the callback might get passed parameters, their value and
152	presence is undefined and you cannot rely on them. Portable AnyEvent	208	presence is undefined and you cannot rely on them. Portable AnyEvent
153	callbacks cannot use arguments passed to I/O watcher callbacks.	209	callbacks cannot use arguments passed to I/O watcher callbacks.
154		210
…		…
158		214
159	Some event loops issue spurious readyness notifications, so you should	215	Some event loops issue spurious readyness notifications, so you should
160	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
161	handles.	217	handles.
162		218
163	Example:
164
165	# 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
166	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	222	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
167	chomp (my $input = <STDIN>);	223	chomp (my $input = <STDIN>);
168	warn "read: $input\n";	224	warn "read: $input\n";
169	undef $w;	225	undef $w;
170	});	226	});
171		227
172	=head2 TIME WATCHERS	228	=head2 TIME WATCHERS
173		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
174	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 >>
175	method with the following mandatory arguments:	239	method with the following mandatory arguments:
176		240
177	C<after> specifies after how many seconds (fractional values are	241	C<after> specifies after how many seconds (fractional values are
178	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
…		…
180		244
181	Although the callback might get passed parameters, their value and	245	Although the callback might get passed parameters, their value and
182	presence is undefined and you cannot rely on them. Portable AnyEvent	246	presence is undefined and you cannot rely on them. Portable AnyEvent
183	callbacks cannot use arguments passed to time watcher callbacks.	247	callbacks cannot use arguments passed to time watcher callbacks.
184		248
185	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
186	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
187	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.
188		254
189	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.
190		258
191	# fire an event after 7.7 seconds	259	Example: fire an event after 7.7 seconds.
		260
192	my $w = AnyEvent->timer (after => 7.7, cb => sub {	261	my $w = AnyEvent->timer (after => 7.7, cb => sub {
193	warn "timeout\n";	262	warn "timeout\n";
194	});	263	});
195		264
196	# to cancel the timer:	265	# to cancel the timer:
197	undef $w;	266	undef $w;
198		267
199	Example 2:
200
201	# 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.
202	my $w;
203		269
204	my $cb = sub {
205	# cancel the old timer while creating a new one
206	$w = AnyEvent->timer (after => 1, cb => $cb);	270	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		271	warn "timeout\n";
207	};	272	};
208
209	# start the "loop" by creating the first watcher
210	$w = AnyEvent->timer (after => 0.5, cb => $cb);
211		273
212	=head3 TIMING ISSUES	274	=head3 TIMING ISSUES
213		275
214	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
215	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
…		…
227	timers.	289	timers.
228		290
229	AnyEvent always prefers relative timers, if available, matching the	291	AnyEvent always prefers relative timers, if available, matching the
230	AnyEvent API.	292	AnyEvent API.
231		293
		294	AnyEvent has two additional methods that return the "current time":
		295
		296	=over 4
		297
		298	=item AnyEvent->time
		299
		300	This returns the "current wallclock time" as a fractional number of
		301	seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
		302	return, and the result is guaranteed to be compatible with those).
		303
		304	It progresses independently of any event loop processing, i.e. each call
		305	will check the system clock, which usually gets updated frequently.
		306
		307	=item AnyEvent->now
		308
		309	This also returns the "current wallclock time", but unlike C<time>, above,
		310	this value might change only once per event loop iteration, depending on
		311	the event loop (most return the same time as C<time>, above). This is the
		312	time that AnyEvent's timers get scheduled against.
		313
		314	I<In almost all cases (in all cases if you don't care), this is the
		315	function to call when you want to know the current time.>
		316
		317	This function is also often faster then C<< AnyEvent->time >>, and
		318	thus the preferred method if you want some timestamp (for example,
		319	L<AnyEvent::Handle> uses this to update it's activity timeouts).
		320
		321	The rest of this section is only of relevance if you try to be very exact
		322	with your timing, you can skip it without bad conscience.
		323
		324	For a practical example of when these times differ, consider L<Event::Lib>
		325	and L<EV> and the following set-up:
		326
		327	The event loop is running and has just invoked one of your callback at
		328	time=500 (assume no other callbacks delay processing). In your callback,
		329	you wait a second by executing C<sleep 1> (blocking the process for a
		330	second) and then (at time=501) you create a relative timer that fires
		331	after three seconds.
		332
		333	With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
		334	both return C<501>, because that is the current time, and the timer will
		335	be scheduled to fire at time=504 (C<501> + C<3>).
		336
		337	With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
		338	time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
		339	last event processing phase started. With L<EV>, your timer gets scheduled
		340	to run at time=503 (C<500> + C<3>).
		341
		342	In one sense, L<Event::Lib> is more exact, as it uses the current time
		343	regardless of any delays introduced by event processing. However, most
		344	callbacks do not expect large delays in processing, so this causes a
		345	higher drift (and a lot more system calls to get the current time).
		346
		347	In another sense, L<EV> is more exact, as your timer will be scheduled at
		348	the same time, regardless of how long event processing actually took.
		349
		350	In either case, if you care (and in most cases, you don't), then you
		351	can get whatever behaviour you want with any event loop, by taking the
		352	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
		353	account.
		354
		355	=item AnyEvent->now_update
		356
		357	Some event loops (such as L<EV> or L<AnyEvent::Impl::Perl>) cache
		358	the current time for each loop iteration (see the discussion of L<<
		359	AnyEvent->now >>, above).
		360
		361	When a callback runs for a long time (or when the process sleeps), then
		362	this "current" time will differ substantially from the real time, which
		363	might affect timers and time-outs.
		364
		365	When this is the case, you can call this method, which will update the
		366	event loop's idea of "current time".
		367
		368	A typical example would be a script in a web server (e.g. C<mod_perl>) -
		369	when mod_perl executes the script, then the event loop will have the wrong
		370	idea about the "current time" (being potentially far in the past, when the
		371	script ran the last time). In that case you should arrange a call to C<<
		372	AnyEvent->now_update >> each time the web server process wakes up again
		373	(e.g. at the start of your script, or in a handler).
		374
		375	Note that updating the time I<might> cause some events to be handled.
		376
		377	=back
		378
232	=head2 SIGNAL WATCHERS	379	=head2 SIGNAL WATCHERS
233		380
		381	$w = AnyEvent->signal (signal => <uppercase_signal_name>, cb => <callback>);
		382
234	You can watch for signals using a signal watcher, C<signal> is the signal	383	You can watch for signals using a signal watcher, C<signal> is the signal
235	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to	384	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
236	be invoked whenever a signal occurs.	385	callback to be invoked whenever a signal occurs.
237		386
238	Although the callback might get passed parameters, their value and	387	Although the callback might get passed parameters, their value and
239	presence is undefined and you cannot rely on them. Portable AnyEvent	388	presence is undefined and you cannot rely on them. Portable AnyEvent
240	callbacks cannot use arguments passed to signal watcher callbacks.	389	callbacks cannot use arguments passed to signal watcher callbacks.
241		390
242	Multiple signal occurances can be clumped together into one callback	391	Multiple signal occurrences can be clumped together into one callback
243	invocation, and callback invocation will be synchronous. synchronous means	392	invocation, and callback invocation will be synchronous. Synchronous means
244	that it might take a while until the signal gets handled by the process,	393	that it might take a while until the signal gets handled by the process,
245	but it is guarenteed not to interrupt any other callbacks.	394	but it is guaranteed not to interrupt any other callbacks.
246		395
247	The main advantage of using these watchers is that you can share a signal	396	The main advantage of using these watchers is that you can share a signal
248	between multiple watchers.	397	between multiple watchers, and AnyEvent will ensure that signals will not
		398	interrupt your program at bad times.
249		399
250	This watcher might use C<%SIG>, so programs overwriting those signals	400	This watcher might use C<%SIG> (depending on the event loop used),
251	directly will likely not work correctly.	401	so programs overwriting those signals directly will likely not work
		402	correctly.
252		403
253	Example: exit on SIGINT	404	Example: exit on SIGINT
254		405
255	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	406	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
256		407
		408	=head3 Restart Behaviour
		409
		410	While restart behaviour is up to the event loop implementation, most will
		411	not restart syscalls (that includes L<Async::Interrupt> and AnyEvent's
		412	pure perl implementation).
		413
		414	=head3 Safe/Unsafe Signals
		415
		416	Perl signals can be either "safe" (synchronous to opcode handling) or
		417	"unsafe" (asynchronous) - the former might get delayed indefinitely, the
		418	latter might corrupt your memory.
		419
		420	AnyEvent signal handlers are, in addition, synchronous to the event loop,
		421	i.e. they will not interrupt your running perl program but will only be
		422	called as part of the normal event handling (just like timer, I/O etc.
		423	callbacks, too).
		424
		425	=head3 Signal Races, Delays and Workarounds
		426
		427	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		428	callbacks to signals in a generic way, which is a pity, as you cannot
		429	do race-free signal handling in perl, requiring C libraries for
		430	this. AnyEvent will try to do it's best, which means in some cases,
		431	signals will be delayed. The maximum time a signal might be delayed is
		432	specified in C<$AnyEvent::MAX_SIGNAL_LATENCY> (default: 10 seconds). This
		433	variable can be changed only before the first signal watcher is created,
		434	and should be left alone otherwise. This variable determines how often
		435	AnyEvent polls for signals (in case a wake-up was missed). Higher values
		436	will cause fewer spurious wake-ups, which is better for power and CPU
		437	saving.
		438
		439	All these problems can be avoided by installing the optional
		440	L<Async::Interrupt> module, which works with most event loops. It will not
		441	work with inherently broken event loops such as L<Event> or L<Event::Lib>
		442	(and not with L<POE> currently, as POE does it's own workaround with
		443	one-second latency). For those, you just have to suffer the delays.
		444
257	=head2 CHILD PROCESS WATCHERS	445	=head2 CHILD PROCESS WATCHERS
258		446
		447	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		448
259	You can also watch on a child process exit and catch its exit status.	449	You can also watch on a child process exit and catch its exit status.
260		450
261	The child process is specified by the C<pid> argument (if set to C<0>, it	451	The child process is specified by the C<pid> argument (one some backends,
262	watches for any child process exit). The watcher will trigger as often	452	using C<0> watches for any child process exit, on others this will
263	as status change for the child are received. This works by installing a	453	croak). The watcher will be triggered only when the child process has
264	signal handler for C<SIGCHLD>. The callback will be called with the pid	454	finished and an exit status is available, not on any trace events
265	and exit status (as returned by waitpid), so unlike other watcher types,	455	(stopped/continued).
266	you I<can> rely on child watcher callback arguments.	456
		457	The callback will be called with the pid and exit status (as returned by
		458	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		459	callback arguments.
		460
		461	This watcher type works by installing a signal handler for C<SIGCHLD>,
		462	and since it cannot be shared, nothing else should use SIGCHLD or reap
		463	random child processes (waiting for specific child processes, e.g. inside
		464	C<system>, is just fine).
267		465
268	There is a slight catch to child watchers, however: you usually start them	466	There is a slight catch to child watchers, however: you usually start them
269	I<after> the child process was created, and this means the process could	467	I<after> the child process was created, and this means the process could
270	have exited already (and no SIGCHLD will be sent anymore).	468	have exited already (and no SIGCHLD will be sent anymore).
271		469
272	Not all event models handle this correctly (POE doesn't), but even for	470	Not all event models handle this correctly (neither POE nor IO::Async do,
		471	see their AnyEvent::Impl manpages for details), but even for event models
273	event models that I<do> handle this correctly, they usually need to be	472	that I<do> handle this correctly, they usually need to be loaded before
274	loaded before the process exits (i.e. before you fork in the first place).	473	the process exits (i.e. before you fork in the first place). AnyEvent's
		474	pure perl event loop handles all cases correctly regardless of when you
		475	start the watcher.
275		476
276	This means you cannot create a child watcher as the very first thing in an	477	This means you cannot create a child watcher as the very first
277	AnyEvent program, you I<have> to create at least one watcher before you	478	thing in an AnyEvent program, you I<have> to create at least one
278	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).	479	watcher before you C<fork> the child (alternatively, you can call
		480	C<AnyEvent::detect>).
		481
		482	As most event loops do not support waiting for child events, they will be
		483	emulated by AnyEvent in most cases, in which the latency and race problems
		484	mentioned in the description of signal watchers apply.
279		485
280	Example: fork a process and wait for it	486	Example: fork a process and wait for it
281		487
282	my $done = AnyEvent->condvar;	488	my $done = AnyEvent->condvar;
283		489
284	my $pid = fork or exit 5;	490	my $pid = fork or exit 5;
285		491
286	my $w = AnyEvent->child (	492	my $w = AnyEvent->child (
287	pid => $pid,	493	pid => $pid,
288	cb => sub {	494	cb => sub {
289	my ($pid, $status) = @_;	495	my ($pid, $status) = @_;
290	warn "pid $pid exited with status $status";	496	warn "pid $pid exited with status $status";
291	$done->send;	497	$done->send;
292	},	498	},
293	);	499	);
294		500
295	# do something else, then wait for process exit	501	# do something else, then wait for process exit
296	$done->recv;	502	$done->recv;
		503
		504	=head2 IDLE WATCHERS
		505
		506	$w = AnyEvent->idle (cb => <callback>);
		507
		508	Sometimes there is a need to do something, but it is not so important
		509	to do it instantly, but only when there is nothing better to do. This
		510	"nothing better to do" is usually defined to be "no other events need
		511	attention by the event loop".
		512
		513	Idle watchers ideally get invoked when the event loop has nothing
		514	better to do, just before it would block the process to wait for new
		515	events. Instead of blocking, the idle watcher is invoked.
		516
		517	Most event loops unfortunately do not really support idle watchers (only
		518	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		519	will simply call the callback "from time to time".
		520
		521	Example: read lines from STDIN, but only process them when the
		522	program is otherwise idle:
		523
		524	my @lines; # read data
		525	my $idle_w;
		526	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		527	push @lines, scalar <STDIN>;
		528
		529	# start an idle watcher, if not already done
		530	$idle_w ||= AnyEvent->idle (cb => sub {
		531	# handle only one line, when there are lines left
		532	if (my $line = shift @lines) {
		533	print "handled when idle: $line";
		534	} else {
		535	# otherwise disable the idle watcher again
		536	undef $idle_w;
		537	}
		538	});
		539	});
297		540
298	=head2 CONDITION VARIABLES	541	=head2 CONDITION VARIABLES
		542
		543	$cv = AnyEvent->condvar;
		544
		545	$cv->send (<list>);
		546	my @res = $cv->recv;
299		547
300	If you are familiar with some event loops you will know that all of them	548	If you are familiar with some event loops you will know that all of them
301	require you to run some blocking "loop", "run" or similar function that	549	require you to run some blocking "loop", "run" or similar function that
302	will actively watch for new events and call your callbacks.	550	will actively watch for new events and call your callbacks.
303		551
304	AnyEvent is different, it expects somebody else to run the event loop and	552	AnyEvent is slightly different: it expects somebody else to run the event
305	will only block when necessary (usually when told by the user).	553	loop and will only block when necessary (usually when told by the user).
306		554
307	The instrument to do that is called a "condition variable", so called	555	The instrument to do that is called a "condition variable", so called
308	because they represent a condition that must become true.	556	because they represent a condition that must become true.
		557
		558	Now is probably a good time to look at the examples further below.
309		559
310	Condition variables can be created by calling the C<< AnyEvent->condvar	560	Condition variables can be created by calling the C<< AnyEvent->condvar
311	>> method, usually without arguments. The only argument pair allowed is	561	>> method, usually without arguments. The only argument pair allowed is
312	C<cb>, which specifies a callback to be called when the condition variable	562	C<cb>, which specifies a callback to be called when the condition variable
313	becomes true.	563	becomes true, with the condition variable as the first argument (but not
		564	the results).
314		565
315	After creation, the conditon variable is "false" until it becomes "true"	566	After creation, the condition variable is "false" until it becomes "true"
316	by calling the C<send> method.	567	by calling the C<send> method (or calling the condition variable as if it
		568	were a callback, read about the caveats in the description for the C<<
		569	->send >> method).
317		570
318	Condition variables are similar to callbacks, except that you can	571	Condition variables are similar to callbacks, except that you can
319	optionally wait for them. They can also be called merge points - points	572	optionally wait for them. They can also be called merge points - points
320	in time where multiple outstandign events have been processed. And yet	573	in time where multiple outstanding events have been processed. And yet
321	another way to call them is transations - each condition variable can be	574	another way to call them is transactions - each condition variable can be
322	used to represent a transaction, which finishes at some point and delivers	575	used to represent a transaction, which finishes at some point and delivers
323	a result.	576	a result. And yet some people know them as "futures" - a promise to
		577	compute/deliver something that you can wait for.
324		578
325	Condition variables are very useful to signal that something has finished,	579	Condition variables are very useful to signal that something has finished,
326	for example, if you write a module that does asynchronous http requests,	580	for example, if you write a module that does asynchronous http requests,
327	then a condition variable would be the ideal candidate to signal the	581	then a condition variable would be the ideal candidate to signal the
328	availability of results. The user can either act when the callback is	582	availability of results. The user can either act when the callback is
…		…
332	you can block your main program until an event occurs - for example, you	586	you can block your main program until an event occurs - for example, you
333	could C<< ->recv >> in your main program until the user clicks the Quit	587	could C<< ->recv >> in your main program until the user clicks the Quit
334	button of your app, which would C<< ->send >> the "quit" event.	588	button of your app, which would C<< ->send >> the "quit" event.
335		589
336	Note that condition variables recurse into the event loop - if you have	590	Note that condition variables recurse into the event loop - if you have
337	two pieces of code that call C<< ->recv >> in a round-robbin fashion, you	591	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
338	lose. Therefore, condition variables are good to export to your caller, but	592	lose. Therefore, condition variables are good to export to your caller, but
339	you should avoid making a blocking wait yourself, at least in callbacks,	593	you should avoid making a blocking wait yourself, at least in callbacks,
340	as this asks for trouble.	594	as this asks for trouble.
341		595
342	Condition variables are represented by hash refs in perl, and the keys	596	Condition variables are represented by hash refs in perl, and the keys
…		…
347		601
348	There are two "sides" to a condition variable - the "producer side" which	602	There are two "sides" to a condition variable - the "producer side" which
349	eventually calls C<< -> send >>, and the "consumer side", which waits	603	eventually calls C<< -> send >>, and the "consumer side", which waits
350	for the send to occur.	604	for the send to occur.
351		605
352	Example:	606	Example: wait for a timer.
353		607
354	# wait till the result is ready	608	# wait till the result is ready
355	my $result_ready = AnyEvent->condvar;	609	my $result_ready = AnyEvent->condvar;
356		610
357	# do something such as adding a timer	611	# do something such as adding a timer
…		…
362	after => 1,	616	after => 1,
363	cb => sub { $result_ready->send },	617	cb => sub { $result_ready->send },
364	);	618	);
365		619
366	# this "blocks" (while handling events) till the callback	620	# this "blocks" (while handling events) till the callback
367	# calls send	621	# calls ->send
368	$result_ready->recv;	622	$result_ready->recv;
		623
		624	Example: wait for a timer, but take advantage of the fact that condition
		625	variables are also callable directly.
		626
		627	my $done = AnyEvent->condvar;
		628	my $delay = AnyEvent->timer (after => 5, cb => $done);
		629	$done->recv;
		630
		631	Example: Imagine an API that returns a condvar and doesn't support
		632	callbacks. This is how you make a synchronous call, for example from
		633	the main program:
		634
		635	use AnyEvent::CouchDB;
		636
		637	...
		638
		639	my @info = $couchdb->info->recv;
		640
		641	And this is how you would just set a callback to be called whenever the
		642	results are available:
		643
		644	$couchdb->info->cb (sub {
		645	my @info = $_[0]->recv;
		646	});
369		647
370	=head3 METHODS FOR PRODUCERS	648	=head3 METHODS FOR PRODUCERS
371		649
372	These methods should only be used by the producing side, i.e. the	650	These methods should only be used by the producing side, i.e. the
373	code/module that eventually sends the signal. Note that it is also	651	code/module that eventually sends the signal. Note that it is also
…		…
386	immediately from within send.	664	immediately from within send.
387		665
388	Any arguments passed to the C<send> call will be returned by all	666	Any arguments passed to the C<send> call will be returned by all
389	future C<< ->recv >> calls.	667	future C<< ->recv >> calls.
390		668
		669	Condition variables are overloaded so one can call them directly (as if
		670	they were a code reference). Calling them directly is the same as calling
		671	C<send>.
		672
391	=item $cv->croak ($error)	673	=item $cv->croak ($error)
392		674
393	Similar to send, but causes all call's to C<< ->recv >> to invoke	675	Similar to send, but causes all call's to C<< ->recv >> to invoke
394	C<Carp::croak> with the given error message/object/scalar.	676	C<Carp::croak> with the given error message/object/scalar.
395		677
396	This can be used to signal any errors to the condition variable	678	This can be used to signal any errors to the condition variable
397	user/consumer.	679	user/consumer. Doing it this way instead of calling C<croak> directly
		680	delays the error detetcion, but has the overwhelmign advantage that it
		681	diagnoses the error at the place where the result is expected, and not
		682	deep in some event clalback without connection to the actual code causing
		683	the problem.
398		684
399	=item $cv->begin ([group callback])	685	=item $cv->begin ([group callback])
400		686
401	=item $cv->end	687	=item $cv->end
402
403	These two methods are EXPERIMENTAL and MIGHT CHANGE.
404		688
405	These two methods can be used to combine many transactions/events into	689	These two methods can be used to combine many transactions/events into
406	one. For example, a function that pings many hosts in parallel might want	690	one. For example, a function that pings many hosts in parallel might want
407	to use a condition variable for the whole process.	691	to use a condition variable for the whole process.
408		692
409	Every call to C<< ->begin >> will increment a counter, and every call to	693	Every call to C<< ->begin >> will increment a counter, and every call to
410	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end	694	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
411	>>, the (last) callback passed to C<begin> will be executed. That callback	695	>>, the (last) callback passed to C<begin> will be executed, passing the
412	is I<supposed> to call C<< ->send >>, but that is not required. If no	696	condvar as first argument. That callback is I<supposed> to call C<< ->send
413	callback was set, C<send> will be called without any arguments.	697	>>, but that is not required. If no group callback was set, C<send> will
		698	be called without any arguments.
414		699
415	Let's clarify this with the ping example:	700	You can think of C<< $cv->send >> giving you an OR condition (one call
		701	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		702	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		703
		704	Let's start with a simple example: you have two I/O watchers (for example,
		705	STDOUT and STDERR for a program), and you want to wait for both streams to
		706	close before activating a condvar:
416		707
417	my $cv = AnyEvent->condvar;	708	my $cv = AnyEvent->condvar;
418		709
		710	$cv->begin; # first watcher
		711	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		712	defined sysread $fh1, my $buf, 4096
		713	or $cv->end;
		714	});
		715
		716	$cv->begin; # second watcher
		717	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		718	defined sysread $fh2, my $buf, 4096
		719	or $cv->end;
		720	});
		721
		722	$cv->recv;
		723
		724	This works because for every event source (EOF on file handle), there is
		725	one call to C<begin>, so the condvar waits for all calls to C<end> before
		726	sending.
		727
		728	The ping example mentioned above is slightly more complicated, as the
		729	there are results to be passwd back, and the number of tasks that are
		730	begung can potentially be zero:
		731
		732	my $cv = AnyEvent->condvar;
		733
419	my %result;	734	my %result;
420	$cv->begin (sub { $cv->send (\%result) });	735	$cv->begin (sub { shift->send (\%result) });
421		736
422	for my $host (@list_of_hosts) {	737	for my $host (@list_of_hosts) {
423	$cv->begin;	738	$cv->begin;
424	ping_host_then_call_callback $host, sub {	739	ping_host_then_call_callback $host, sub {
425	$result{$host} = ...;	740	$result{$host} = ...;
…		…
440	loop, which serves two important purposes: first, it sets the callback	755	loop, which serves two important purposes: first, it sets the callback
441	to be called once the counter reaches C<0>, and second, it ensures that	756	to be called once the counter reaches C<0>, and second, it ensures that
442	C<send> is called even when C<no> hosts are being pinged (the loop	757	C<send> is called even when C<no> hosts are being pinged (the loop
443	doesn't execute once).	758	doesn't execute once).
444		759
445	This is the general pattern when you "fan out" into multiple subrequests:	760	This is the general pattern when you "fan out" into multiple (but
446	use an outer C<begin>/C<end> pair to set the callback and ensure C<end>	761	potentially none) subrequests: use an outer C<begin>/C<end> pair to set
447	is called at least once, and then, for each subrequest you start, call	762	the callback and ensure C<end> is called at least once, and then, for each
448	C<begin> and for eahc subrequest you finish, call C<end>.	763	subrequest you start, call C<begin> and for each subrequest you finish,
		764	call C<end>.
449		765
450	=back	766	=back
451		767
452	=head3 METHODS FOR CONSUMERS	768	=head3 METHODS FOR CONSUMERS
453		769
…		…
469	function will call C<croak>.	785	function will call C<croak>.
470		786
471	In list context, all parameters passed to C<send> will be returned,	787	In list context, all parameters passed to C<send> will be returned,
472	in scalar context only the first one will be returned.	788	in scalar context only the first one will be returned.
473		789
		790	Note that doing a blocking wait in a callback is not supported by any
		791	event loop, that is, recursive invocation of a blocking C<< ->recv
		792	>> is not allowed, and the C<recv> call will C<croak> if such a
		793	condition is detected. This condition can be slightly loosened by using
		794	L<Coro::AnyEvent>, which allows you to do a blocking C<< ->recv >> from
		795	any thread that doesn't run the event loop itself.
		796
474	Not all event models support a blocking wait - some die in that case	797	Not all event models support a blocking wait - some die in that case
475	(programs might want to do that to stay interactive), so I<if you are	798	(programs might want to do that to stay interactive), so I<if you are
476	using this from a module, never require a blocking wait>, but let the	799	using this from a module, never require a blocking wait>. Instead, let the
477	caller decide whether the call will block or not (for example, by coupling	800	caller decide whether the call will block or not (for example, by coupling
478	condition variables with some kind of request results and supporting	801	condition variables with some kind of request results and supporting
479	callbacks so the caller knows that getting the result will not block,	802	callbacks so the caller knows that getting the result will not block,
480	while still suppporting blocking waits if the caller so desires).	803	while still supporting blocking waits if the caller so desires).
481
482	Another reason I<never> to C<< ->recv >> in a module is that you cannot
483	sensibly have two C<< ->recv >>'s in parallel, as that would require
484	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
485	can supply.
486
487	The L<Coro> module, however, I<can> and I<does> supply coroutines and, in
488	fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe
489	versions and also integrates coroutines into AnyEvent, making blocking
490	C<< ->recv >> calls perfectly safe as long as they are done from another
491	coroutine (one that doesn't run the event loop).
492		804
493	You can ensure that C<< -recv >> never blocks by setting a callback and	805	You can ensure that C<< -recv >> never blocks by setting a callback and
494	only calling C<< ->recv >> from within that callback (or at a later	806	only calling C<< ->recv >> from within that callback (or at a later
495	time). This will work even when the event loop does not support blocking	807	time). This will work even when the event loop does not support blocking
496	waits otherwise.	808	waits otherwise.
…		…
498	=item $bool = $cv->ready	810	=item $bool = $cv->ready
499		811
500	Returns true when the condition is "true", i.e. whether C<send> or	812	Returns true when the condition is "true", i.e. whether C<send> or
501	C<croak> have been called.	813	C<croak> have been called.
502		814
503	=item $cb = $cv->cb ([new callback])	815	=item $cb = $cv->cb ($cb->($cv))
504		816
505	This is a mutator function that returns the callback set and optionally	817	This is a mutator function that returns the callback set and optionally
506	replaces it before doing so.	818	replaces it before doing so.
507		819
508	The callback will be called when the condition becomes "true", i.e. when	820	The callback will be called when the condition becomes (or already was)
509	C<send> or C<croak> are called. Calling C<recv> inside the callback	821	"true", i.e. when C<send> or C<croak> are called (or were called), with
		822	the only argument being the condition variable itself. Calling C<recv>
510	or at any later time is guaranteed not to block.	823	inside the callback or at any later time is guaranteed not to block.
511		824
512	=back	825	=back
513		826
		827	=head1 SUPPORTED EVENT LOOPS/BACKENDS
		828
		829	The available backend classes are (every class has its own manpage):
		830
		831	=over 4
		832
		833	=item Backends that are autoprobed when no other event loop can be found.
		834
		835	EV is the preferred backend when no other event loop seems to be in
		836	use. If EV is not installed, then AnyEvent will fall back to its own
		837	pure-perl implementation, which is available everywhere as it comes with
		838	AnyEvent itself.
		839
		840	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		841	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
		842
		843	=item Backends that are transparently being picked up when they are used.
		844
		845	These will be used when they are currently loaded when the first watcher
		846	is created, in which case it is assumed that the application is using
		847	them. This means that AnyEvent will automatically pick the right backend
		848	when the main program loads an event module before anything starts to
		849	create watchers. Nothing special needs to be done by the main program.
		850
		851	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		852	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		853	AnyEvent::Impl::Tk based on Tk, very broken.
		854	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		855	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		856	AnyEvent::Impl::Irssi used when running within irssi.
		857
		858	=item Backends with special needs.
		859
		860	Qt requires the Qt::Application to be instantiated first, but will
		861	otherwise be picked up automatically. As long as the main program
		862	instantiates the application before any AnyEvent watchers are created,
		863	everything should just work.
		864
		865	AnyEvent::Impl::Qt based on Qt.
		866
		867	Support for IO::Async can only be partial, as it is too broken and
		868	architecturally limited to even support the AnyEvent API. It also
		869	is the only event loop that needs the loop to be set explicitly, so
		870	it can only be used by a main program knowing about AnyEvent. See
		871	L<AnyEvent::Impl::Async> for the gory details.
		872
		873	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
		874
		875	=item Event loops that are indirectly supported via other backends.
		876
		877	Some event loops can be supported via other modules:
		878
		879	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		880
		881	B<WxWidgets> has no support for watching file handles. However, you can
		882	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		883	polls 20 times per second, which was considered to be too horrible to even
		884	consider for AnyEvent.
		885
		886	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		887	backend, so it can be supported through POE.
		888
		889	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		890	load L<POE> when detecting them, in the hope that POE will pick them up,
		891	in which case everything will be automatic.
		892
		893	=back
		894
514	=head1 GLOBAL VARIABLES AND FUNCTIONS	895	=head1 GLOBAL VARIABLES AND FUNCTIONS
515		896
		897	These are not normally required to use AnyEvent, but can be useful to
		898	write AnyEvent extension modules.
		899
516	=over 4	900	=over 4
517		901
518	=item $AnyEvent::MODEL	902	=item $AnyEvent::MODEL
519		903
520	Contains C<undef> until the first watcher is being created. Then it	904	Contains C<undef> until the first watcher is being created, before the
		905	backend has been autodetected.
		906
521	contains the event model that is being used, which is the name of the	907	Afterwards it contains the event model that is being used, which is the
522	Perl class implementing the model. This class is usually one of the	908	name of the Perl class implementing the model. This class is usually one
523	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	909	of the C<AnyEvent::Impl:xxx> modules, but can be any other class in the
524	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	910	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
525		911	will be C<urxvt::anyevent>).
526	The known classes so far are:
527
528	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
529	AnyEvent::Impl::Event based on Event, second best choice.
530	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
531	AnyEvent::Impl::Glib based on Glib, third-best choice.
532	AnyEvent::Impl::Tk based on Tk, very bad choice.
533	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
534	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
535	AnyEvent::Impl::POE based on POE, not generic enough for full support.
536
537	There is no support for WxWidgets, as WxWidgets has no support for
538	watching file handles. However, you can use WxWidgets through the
539	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
540	second, which was considered to be too horrible to even consider for
541	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
542	it's adaptor.
543
544	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
545	autodetecting them.
546		912
547	=item AnyEvent::detect	913	=item AnyEvent::detect
548		914
549	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	915	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
550	if necessary. You should only call this function right before you would	916	if necessary. You should only call this function right before you would
551	have created an AnyEvent watcher anyway, that is, as late as possible at	917	have created an AnyEvent watcher anyway, that is, as late as possible at
552	runtime.	918	runtime, and not e.g. while initialising of your module.
		919
		920	If you need to do some initialisation before AnyEvent watchers are
		921	created, use C<post_detect>.
553		922
554	=item $guard = AnyEvent::post_detect { BLOCK }	923	=item $guard = AnyEvent::post_detect { BLOCK }
555		924
556	Arranges for the code block to be executed as soon as the event model is	925	Arranges for the code block to be executed as soon as the event model is
557	autodetected (or immediately if this has already happened).	926	autodetected (or immediately if this has already happened).
558		927
		928	The block will be executed I<after> the actual backend has been detected
		929	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		930	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		931	other initialisations - see the sources of L<AnyEvent::Strict> or
		932	L<AnyEvent::AIO> to see how this is used.
		933
		934	The most common usage is to create some global watchers, without forcing
		935	event module detection too early, for example, L<AnyEvent::AIO> creates
		936	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		937	avoid autodetecting the event module at load time.
		938
559	If called in scalar or list context, then it creates and returns an object	939	If called in scalar or list context, then it creates and returns an object
560	that automatically removes the callback again when it is destroyed. See	940	that automatically removes the callback again when it is destroyed (or
		941	C<undef> when the hook was immediately executed). See L<AnyEvent::AIO> for
561	L<Coro::BDB> for a case where this is useful.	942	a case where this is useful.
		943
		944	Example: Create a watcher for the IO::AIO module and store it in
		945	C<$WATCHER>. Only do so after the event loop is initialised, though.
		946
		947	our WATCHER;
		948
		949	my $guard = AnyEvent::post_detect {
		950	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		951	};
		952
		953	# the ||= is important in case post_detect immediately runs the block,
		954	# as to not clobber the newly-created watcher. assigning both watcher and
		955	# post_detect guard to the same variable has the advantage of users being
		956	# able to just C<undef $WATCHER> if the watcher causes them grief.
		957
		958	$WATCHER ||= $guard;
562		959
563	=item @AnyEvent::post_detect	960	=item @AnyEvent::post_detect
564		961
565	If there are any code references in this array (you can C<push> to it	962	If there are any code references in this array (you can C<push> to it
566	before or after loading AnyEvent), then they will called directly after	963	before or after loading AnyEvent), then they will called directly after
567	the event loop has been chosen.	964	the event loop has been chosen.
568		965
569	You should check C<$AnyEvent::MODEL> before adding to this array, though:	966	You should check C<$AnyEvent::MODEL> before adding to this array, though:
570	if it contains a true value then the event loop has already been detected,	967	if it is defined then the event loop has already been detected, and the
571	and the array will be ignored.	968	array will be ignored.
572		969
573	Best use C<AnyEvent::post_detect { BLOCK }> instead.	970	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		971	it, as it takes care of these details.
		972
		973	This variable is mainly useful for modules that can do something useful
		974	when AnyEvent is used and thus want to know when it is initialised, but do
		975	not need to even load it by default. This array provides the means to hook
		976	into AnyEvent passively, without loading it.
		977
		978	Example: To load Coro::AnyEvent whenever Coro and AnyEvent are used
		979	together, you could put this into Coro (this is the actual code used by
		980	Coro to accomplish this):
		981
		982	if (defined $AnyEvent::MODEL) {
		983	# AnyEvent already initialised, so load Coro::AnyEvent
		984	require Coro::AnyEvent;
		985	} else {
		986	# AnyEvent not yet initialised, so make sure to load Coro::AnyEvent
		987	# as soon as it is
		988	push @AnyEvent::post_detect, sub { require Coro::AnyEvent };
		989	}
574		990
575	=back	991	=back
576		992
577	=head1 WHAT TO DO IN A MODULE	993	=head1 WHAT TO DO IN A MODULE
578		994
…		…
601		1017
602	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	1018	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
603	do anything special (it does not need to be event-based) and let AnyEvent	1019	do anything special (it does not need to be event-based) and let AnyEvent
604	decide which implementation to chose if some module relies on it.	1020	decide which implementation to chose if some module relies on it.
605		1021
606	If the main program relies on a specific event model. For example, in	1022	If the main program relies on a specific event model - for example, in
607	Gtk2 programs you have to rely on the Glib module. You should load the	1023	Gtk2 programs you have to rely on the Glib module - you should load the
608	event module before loading AnyEvent or any module that uses it: generally	1024	event module before loading AnyEvent or any module that uses it: generally
609	speaking, you should load it as early as possible. The reason is that	1025	speaking, you should load it as early as possible. The reason is that
610	modules might create watchers when they are loaded, and AnyEvent will	1026	modules might create watchers when they are loaded, and AnyEvent will
611	decide on the event model to use as soon as it creates watchers, and it	1027	decide on the event model to use as soon as it creates watchers, and it
612	might chose the wrong one unless you load the correct one yourself.	1028	might chose the wrong one unless you load the correct one yourself.
613		1029
614	You can chose to use a rather inefficient pure-perl implementation by	1030	You can chose to use a pure-perl implementation by loading the
615	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	1031	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
616	behaviour everywhere, but letting AnyEvent chose is generally better.	1032	everywhere, but letting AnyEvent chose the model is generally better.
		1033
		1034	=head2 MAINLOOP EMULATION
		1035
		1036	Sometimes (often for short test scripts, or even standalone programs who
		1037	only want to use AnyEvent), you do not want to run a specific event loop.
		1038
		1039	In that case, you can use a condition variable like this:
		1040
		1041	AnyEvent->condvar->recv;
		1042
		1043	This has the effect of entering the event loop and looping forever.
		1044
		1045	Note that usually your program has some exit condition, in which case
		1046	it is better to use the "traditional" approach of storing a condition
		1047	variable somewhere, waiting for it, and sending it when the program should
		1048	exit cleanly.
		1049
617		1050
618	=head1 OTHER MODULES	1051	=head1 OTHER MODULES
619		1052
620	The following is a non-exhaustive list of additional modules that use	1053	The following is a non-exhaustive list of additional modules that use
621	AnyEvent and can therefore be mixed easily with other AnyEvent modules	1054	AnyEvent as a client and can therefore be mixed easily with other AnyEvent
622	in the same program. Some of the modules come with AnyEvent, some are	1055	modules and other event loops in the same program. Some of the modules
623	available via CPAN.	1056	come with AnyEvent, most are available via CPAN.
624		1057
625	=over 4	1058	=over 4
626		1059
627	=item L<AnyEvent::Util>	1060	=item L<AnyEvent::Util>
628		1061
629	Contains various utility functions that replace often-used but blocking	1062	Contains various utility functions that replace often-used but blocking
630	functions such as C<inet_aton> by event-/callback-based versions.	1063	functions such as C<inet_aton> by event-/callback-based versions.
631
632	=item L<AnyEvent::Handle>
633
634	Provide read and write buffers and manages watchers for reads and writes.
635		1064
636	=item L<AnyEvent::Socket>	1065	=item L<AnyEvent::Socket>
637		1066
638	Provides various utility functions for (internet protocol) sockets,	1067	Provides various utility functions for (internet protocol) sockets,
639	addresses and name resolution. Also functions to create non-blocking tcp	1068	addresses and name resolution. Also functions to create non-blocking tcp
640	connections or tcp servers, with IPv6 and SRV record support and more.	1069	connections or tcp servers, with IPv6 and SRV record support and more.
641		1070
		1071	=item L<AnyEvent::Handle>
		1072
		1073	Provide read and write buffers, manages watchers for reads and writes,
		1074	supports raw and formatted I/O, I/O queued and fully transparent and
		1075	non-blocking SSL/TLS (via L<AnyEvent::TLS>.
		1076
		1077	=item L<AnyEvent::DNS>
		1078
		1079	Provides rich asynchronous DNS resolver capabilities.
		1080
		1081	=item L<AnyEvent::HTTP>
		1082
		1083	A simple-to-use HTTP library that is capable of making a lot of concurrent
		1084	HTTP requests.
		1085
642	=item L<AnyEvent::HTTPD>	1086	=item L<AnyEvent::HTTPD>
643		1087
644	Provides a simple web application server framework.	1088	Provides a simple web application server framework.
645		1089
646	=item L<AnyEvent::DNS>
647
648	Provides rich asynchronous DNS resolver capabilities.
649
650	=item L<AnyEvent::FastPing>	1090	=item L<AnyEvent::FastPing>
651		1091
652	The fastest ping in the west.	1092	The fastest ping in the west.
653		1093
		1094	=item L<AnyEvent::DBI>
		1095
		1096	Executes L<DBI> requests asynchronously in a proxy process.
		1097
		1098	=item L<AnyEvent::AIO>
		1099
		1100	Truly asynchronous I/O, should be in the toolbox of every event
		1101	programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
		1102	together.
		1103
		1104	=item L<AnyEvent::BDB>
		1105
		1106	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
		1107	L<BDB> and AnyEvent together.
		1108
		1109	=item L<AnyEvent::GPSD>
		1110
		1111	A non-blocking interface to gpsd, a daemon delivering GPS information.
		1112
654	=item L<Net::IRC3>	1113	=item L<AnyEvent::IRC>
655		1114
656	AnyEvent based IRC client module family.	1115	AnyEvent based IRC client module family (replacing the older Net::IRC3).
657		1116
658	=item L<Net::XMPP2>	1117	=item L<AnyEvent::XMPP>
659		1118
660	AnyEvent based XMPP (Jabber protocol) module family.	1119	AnyEvent based XMPP (Jabber protocol) module family (replacing the older
		1120	Net::XMPP2>.
		1121
		1122	=item L<AnyEvent::IGS>
		1123
		1124	A non-blocking interface to the Internet Go Server protocol (used by
		1125	L<App::IGS>).
661		1126
662	=item L<Net::FCP>	1127	=item L<Net::FCP>
663		1128
664	AnyEvent-based implementation of the Freenet Client Protocol, birthplace	1129	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
665	of AnyEvent.	1130	of AnyEvent.
…		…
670		1135
671	=item L<Coro>	1136	=item L<Coro>
672		1137
673	Has special support for AnyEvent via L<Coro::AnyEvent>.	1138	Has special support for AnyEvent via L<Coro::AnyEvent>.
674		1139
675	=item L<AnyEvent::AIO>, L<IO::AIO>
676
677	Truly asynchronous I/O, should be in the toolbox of every event
678	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
679	together.
680
681	=item L<AnyEvent::BDB>, L<BDB>
682
683	Truly asynchronous Berkeley DB access. AnyEvent::AIO transparently fuses
684	IO::AIO and AnyEvent together.
685
686	=item L<IO::Lambda>
687
688	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
689
690	=back	1140	=back
691		1141
692	=cut	1142	=cut
693		1143
694	package AnyEvent;	1144	package AnyEvent;
695		1145
696	no warnings;	1146	# basically a tuned-down version of common::sense
697	use strict;	1147	sub common_sense {
		1148	# from common:.sense 1.0
		1149	${^WARNING_BITS} = "\xfc\x3f\x33\x00\x0f\xf3\xcf\xc0\xf3\xfc\x33\x03";
		1150	# use strict vars subs
		1151	$^H |= 0x00000600;
		1152	}
698		1153
		1154	BEGIN { AnyEvent::common_sense }
		1155
699	use Carp;	1156	use Carp ();
700		1157
701	our $VERSION = '3.6';	1158	our $VERSION = '5.22';
702	our $MODEL;	1159	our $MODEL;
703		1160
704	our $AUTOLOAD;	1161	our $AUTOLOAD;
705	our @ISA;	1162	our @ISA;
706		1163
707	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
708
709	our @REGISTRY;	1164	our @REGISTRY;
710		1165
711	our %PROTOCOL; # (ipv4|ipv6) => (1|2)	1166	our $VERBOSE;
		1167
		1168	BEGIN {
		1169	eval "sub WIN32(){ " . (($^O =~ /mswin32/i)*1) ." }";
		1170	eval "sub TAINT(){ " . (${^TAINT}*1) . " }";
		1171
		1172	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1173	if ${^TAINT};
		1174
		1175	$VERBOSE = $ENV{PERL_ANYEVENT_VERBOSE}*1;
		1176
		1177	}
		1178
		1179	our $MAX_SIGNAL_LATENCY = 10;
		1180
		1181	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
712		1182
713	{	1183	{
714	my $idx;	1184	my $idx;
715	$PROTOCOL{$_} = ++$idx	1185	$PROTOCOL{$_} = ++$idx
		1186	for reverse split /\s*,\s*/,
716	for split /\s*,\s*/, $ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";	1187	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
717	}	1188	}
718		1189
719	my @models = (	1190	my @models = (
720	[EV:: => AnyEvent::Impl::EV::],	1191	[EV:: => AnyEvent::Impl::EV:: , 1],
		1192	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl:: , 1],
		1193	# everything below here will not (normally) be autoprobed
		1194	# as the pureperl backend should work everywhere
		1195	# and is usually faster
721	[Event:: => AnyEvent::Impl::Event::],	1196	[Event:: => AnyEvent::Impl::Event::, 1],
		1197	[Glib:: => AnyEvent::Impl::Glib:: , 1], # becomes extremely slow with many watchers
		1198	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		1199	[Irssi:: => AnyEvent::Impl::Irssi::], # Irssi has a bogus "Event" package
722	[Tk:: => AnyEvent::Impl::Tk::],	1200	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		1201	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		1202	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
723	[Wx:: => AnyEvent::Impl::POE::],	1203	[Wx:: => AnyEvent::Impl::POE::],
724	[Prima:: => AnyEvent::Impl::POE::],	1204	[Prima:: => AnyEvent::Impl::POE::],
725	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1205	# IO::Async is just too broken - we would need workarounds for its
726	# everything below here will not be autoprobed as the pureperl backend should work everywhere	1206	# byzantine signal and broken child handling, among others.
727	[Glib:: => AnyEvent::Impl::Glib::],	1207	# IO::Async is rather hard to detect, as it doesn't have any
728	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy	1208	# obvious default class.
729	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program	1209	[IO::Async:: => AnyEvent::Impl::IOAsync::], # requires special main program
730	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza	1210	[IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1211	[IO::Async::Notifier:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1212	[AnyEvent::Impl::IOAsync:: => AnyEvent::Impl::IOAsync::], # requires special main program
731	);	1213	);
732		1214
733	our %method = map +($_ => 1), qw(io timer signal child condvar one_event DESTROY);	1215	our %method = map +($_ => 1),
		1216	qw(io timer time now now_update signal child idle condvar one_event DESTROY);
734		1217
735	our @post_detect;	1218	our @post_detect;
736		1219
737	sub post_detect(&) {	1220	sub post_detect(&) {
738	my ($cb) = @_;	1221	my ($cb) = @_;
739		1222
740	if ($MODEL) {	1223	if ($MODEL) {
741	$cb->();	1224	$cb->();
742		1225
743	1	1226	undef
744	} else {	1227	} else {
745	push @post_detect, $cb;	1228	push @post_detect, $cb;
746		1229
747	defined wantarray	1230	defined wantarray
748	? bless \$cb, "AnyEvent::Util::PostDetect"	1231	? bless \$cb, "AnyEvent::Util::postdetect"
749	: ()	1232	: ()
750	}	1233	}
751	}	1234	}
752		1235
753	sub AnyEvent::Util::PostDetect::DESTROY {	1236	sub AnyEvent::Util::postdetect::DESTROY {
754	@post_detect = grep $_ != ${$_[0]}, @post_detect;	1237	@post_detect = grep $_ != ${$_[0]}, @post_detect;
755	}	1238	}
756		1239
757	sub detect() {	1240	sub detect() {
758	unless ($MODEL) {	1241	unless ($MODEL) {
759	no strict 'refs';	1242	local $SIG{__DIE__};
760		1243
761	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	1244	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
762	my $model = "AnyEvent::Impl::$1";	1245	my $model = "AnyEvent::Impl::$1";
763	if (eval "require $model") {	1246	if (eval "require $model") {
764	$MODEL = $model;	1247	$MODEL = $model;
765	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	1248	warn "AnyEvent: loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.\n" if $VERBOSE >= 2;
766	} else {	1249	} else {
767	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;	1250	warn "AnyEvent: unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@" if $VERBOSE;
768	}	1251	}
769	}	1252	}
770		1253
771	# check for already loaded models	1254	# check for already loaded models
772	unless ($MODEL) {	1255	unless ($MODEL) {
773	for (@REGISTRY, @models) {	1256	for (@REGISTRY, @models) {
774	my ($package, $model) = @$_;	1257	my ($package, $model) = @$_;
775	if (${"$package\::VERSION"} > 0) {	1258	if (${"$package\::VERSION"} > 0) {
776	if (eval "require $model") {	1259	if (eval "require $model") {
777	$MODEL = $model;	1260	$MODEL = $model;
778	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;	1261	warn "AnyEvent: autodetected model '$model', using it.\n" if $VERBOSE >= 2;
779	last;	1262	last;
780	}	1263	}
781	}	1264	}
782	}	1265	}
783		1266
784	unless ($MODEL) {	1267	unless ($MODEL) {
785	# try to load a model	1268	# try to autoload a model
786
787	for (@REGISTRY, @models) {	1269	for (@REGISTRY, @models) {
788	my ($package, $model) = @$_;	1270	my ($package, $model, $autoload) = @$_;
		1271	if (
		1272	$autoload
789	if (eval "require $package"	1273	and eval "require $package"
790	and ${"$package\::VERSION"} > 0	1274	and ${"$package\::VERSION"} > 0
791	and eval "require $model") {	1275	and eval "require $model"
		1276	) {
792	$MODEL = $model;	1277	$MODEL = $model;
793	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;	1278	warn "AnyEvent: autoloaded model '$model', using it.\n" if $VERBOSE >= 2;
794	last;	1279	last;
795	}	1280	}
796	}	1281	}
797		1282
798	$MODEL	1283	$MODEL
799	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.";	1284	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.\n";
800	}	1285	}
801	}	1286	}
802		1287
		1288	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		1289
803	unshift @ISA, $MODEL;	1290	unshift @ISA, $MODEL;
804	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	1291
		1292	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
805		1293
806	(shift @post_detect)->() while @post_detect;	1294	(shift @post_detect)->() while @post_detect;
807	}	1295	}
808		1296
809	$MODEL	1297	$MODEL
…		…
811		1299
812	sub AUTOLOAD {	1300	sub AUTOLOAD {
813	(my $func = $AUTOLOAD) =~ s/.*://;	1301	(my $func = $AUTOLOAD) =~ s/.*://;
814		1302
815	$method{$func}	1303	$method{$func}
816	or croak "$func: not a valid method for AnyEvent objects";	1304	or Carp::croak "$func: not a valid method for AnyEvent objects";
817		1305
818	detect unless $MODEL;	1306	detect unless $MODEL;
819		1307
820	my $class = shift;	1308	my $class = shift;
821	$class->$func (@_);	1309	$class->$func (@_);
822	}	1310	}
823		1311
		1312	# utility function to dup a filehandle. this is used by many backends
		1313	# to support binding more than one watcher per filehandle (they usually
		1314	# allow only one watcher per fd, so we dup it to get a different one).
		1315	sub _dupfh($$;$$) {
		1316	my ($poll, $fh, $r, $w) = @_;
		1317
		1318	# cygwin requires the fh mode to be matching, unix doesn't
		1319	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1320
		1321	open my $fh2, $mode, $fh
		1322	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1323
		1324	# we assume CLOEXEC is already set by perl in all important cases
		1325
		1326	($fh2, $rw)
		1327	}
		1328
		1329	=head1 SIMPLIFIED AE API
		1330
		1331	Starting with version 5.0, AnyEvent officially supports a second, much
		1332	simpler, API that is designed to reduce the calling, typing and memory
		1333	overhead.
		1334
		1335	See the L<AE> manpage for details.
		1336
		1337	=cut
		1338
		1339	package AE;
		1340
		1341	our $VERSION = $AnyEvent::VERSION;
		1342
		1343	sub io($$$) {
		1344	AnyEvent->io (fh => $_[0], poll => $_[1] ? "w" : "r", cb => $_[2])
		1345	}
		1346
		1347	sub timer($$$) {
		1348	AnyEvent->timer (after => $_[0], interval => $_[1], cb => $_[2])
		1349	}
		1350
		1351	sub signal($$) {
		1352	AnyEvent->signal (signal => $_[0], cb => $_[1])
		1353	}
		1354
		1355	sub child($$) {
		1356	AnyEvent->child (pid => $_[0], cb => $_[1])
		1357	}
		1358
		1359	sub idle($) {
		1360	AnyEvent->idle (cb => $_[0])
		1361	}
		1362
		1363	sub cv(;&) {
		1364	AnyEvent->condvar (@_ ? (cb => $_[0]) : ())
		1365	}
		1366
		1367	sub now() {
		1368	AnyEvent->now
		1369	}
		1370
		1371	sub now_update() {
		1372	AnyEvent->now_update
		1373	}
		1374
		1375	sub time() {
		1376	AnyEvent->time
		1377	}
		1378
824	package AnyEvent::Base;	1379	package AnyEvent::Base;
825		1380
		1381	# default implementations for many methods
		1382
		1383	sub _time() {
		1384	# probe for availability of Time::HiRes
		1385	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1386	warn "AnyEvent: using Time::HiRes for sub-second timing accuracy.\n" if $VERBOSE >= 8;
		1387	*_time = \&Time::HiRes::time;
		1388	# if (eval "use POSIX (); (POSIX::times())...
		1389	} else {
		1390	warn "AnyEvent: using built-in time(), WARNING, no sub-second resolution!\n" if $VERBOSE;
		1391	*_time = sub { time }; # epic fail
		1392	}
		1393
		1394	&_time
		1395	}
		1396
		1397	sub time { _time }
		1398	sub now { _time }
		1399	sub now_update { }
		1400
826	# default implementation for ->condvar	1401	# default implementation for ->condvar
827		1402
828	sub condvar {	1403	sub condvar {
829	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, AnyEvent::CondVar::	1404	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
830	}	1405	}
831		1406
832	# default implementation for ->signal	1407	# default implementation for ->signal
833		1408
834	our %SIG_CB;	1409	our $HAVE_ASYNC_INTERRUPT;
		1410
		1411	sub _have_async_interrupt() {
		1412	$HAVE_ASYNC_INTERRUPT = 1*(!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT}
		1413	&& eval "use Async::Interrupt 1.02 (); 1")
		1414	unless defined $HAVE_ASYNC_INTERRUPT;
		1415
		1416	$HAVE_ASYNC_INTERRUPT
		1417	}
		1418
		1419	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1420	our (%SIG_ASY, %SIG_ASY_W);
		1421	our ($SIG_COUNT, $SIG_TW);
		1422
		1423	sub _signal_exec {
		1424	$HAVE_ASYNC_INTERRUPT
		1425	? $SIGPIPE_R->drain
		1426	: sysread $SIGPIPE_R, (my $dummy), 9;
		1427
		1428	while (%SIG_EV) {
		1429	for (keys %SIG_EV) {
		1430	delete $SIG_EV{$_};
		1431	$_->() for values %{ $SIG_CB{$_} || {} };
		1432	}
		1433	}
		1434	}
		1435
		1436	# install a dummy wakeup watcher to reduce signal catching latency
		1437	sub _sig_add() {
		1438	unless ($SIG_COUNT++) {
		1439	# try to align timer on a full-second boundary, if possible
		1440	my $NOW = AE::now;
		1441
		1442	$SIG_TW = AE::timer
		1443	$MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1444	$MAX_SIGNAL_LATENCY,
		1445	sub { } # just for the PERL_ASYNC_CHECK
		1446	;
		1447	}
		1448	}
		1449
		1450	sub _sig_del {
		1451	undef $SIG_TW
		1452	unless --$SIG_COUNT;
		1453	}
		1454
		1455	our $_sig_name_init; $_sig_name_init = sub {
		1456	eval q{ # poor man's autoloading
		1457	undef $_sig_name_init;
		1458
		1459	if (_have_async_interrupt) {
		1460	*sig2num = \&Async::Interrupt::sig2num;
		1461	*sig2name = \&Async::Interrupt::sig2name;
		1462	} else {
		1463	require Config;
		1464
		1465	my %signame2num;
		1466	@signame2num{ split ' ', $Config::Config{sig_name} }
		1467	= split ' ', $Config::Config{sig_num};
		1468
		1469	my @signum2name;
		1470	@signum2name[values %signame2num] = keys %signame2num;
		1471
		1472	*sig2num = sub($) {
		1473	$_[0] > 0 ? shift : $signame2num{+shift}
		1474	};
		1475	*sig2name = sub ($) {
		1476	$_[0] > 0 ? $signum2name[+shift] : shift
		1477	};
		1478	}
		1479	};
		1480	die if $@;
		1481	};
		1482
		1483	sub sig2num ($) { &$_sig_name_init; &sig2num }
		1484	sub sig2name($) { &$_sig_name_init; &sig2name }
835		1485
836	sub signal {	1486	sub signal {
		1487	eval q{ # poor man's autoloading {}
		1488	# probe for availability of Async::Interrupt
		1489	if (_have_async_interrupt) {
		1490	warn "AnyEvent: using Async::Interrupt for race-free signal handling.\n" if $VERBOSE >= 8;
		1491
		1492	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1493	$SIG_IO = AE::io $SIGPIPE_R->fileno, 0, \&_signal_exec;
		1494
		1495	} else {
		1496	warn "AnyEvent: using emulated perl signal handling with latency timer.\n" if $VERBOSE >= 8;
		1497
		1498	require Fcntl;
		1499
		1500	if (AnyEvent::WIN32) {
		1501	require AnyEvent::Util;
		1502
		1503	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1504	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R, 1) if $SIGPIPE_R;
		1505	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W, 1) if $SIGPIPE_W; # just in case
		1506	} else {
		1507	pipe $SIGPIPE_R, $SIGPIPE_W;
		1508	fcntl $SIGPIPE_R, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_R;
		1509	fcntl $SIGPIPE_W, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_W; # just in case
		1510
		1511	# not strictly required, as $^F is normally 2, but let's make sure...
		1512	fcntl $SIGPIPE_R, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1513	fcntl $SIGPIPE_W, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1514	}
		1515
		1516	$SIGPIPE_R
		1517	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1518
		1519	$SIG_IO = AE::io $SIGPIPE_R, 0, \&_signal_exec;
		1520	}
		1521
		1522	*signal = sub {
837	my (undef, %arg) = @_;	1523	my (undef, %arg) = @_;
838		1524
839	my $signal = uc $arg{signal}	1525	my $signal = uc $arg{signal}
840	or Carp::croak "required option 'signal' is missing";	1526	or Carp::croak "required option 'signal' is missing";
841		1527
		1528	if ($HAVE_ASYNC_INTERRUPT) {
		1529	# async::interrupt
		1530
		1531	$signal = sig2num $signal;
842	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1532	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1533
		1534	$SIG_ASY{$signal} ||= new Async::Interrupt
		1535	cb => sub { undef $SIG_EV{$signal} },
		1536	signal => $signal,
		1537	pipe => [$SIGPIPE_R->filenos],
		1538	pipe_autodrain => 0,
		1539	;
		1540
		1541	} else {
		1542	# pure perl
		1543
		1544	# AE::Util has been loaded in signal
		1545	$signal = sig2name $signal;
		1546	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1547
843	$SIG{$signal} ||= sub {	1548	$SIG{$signal} ||= sub {
844	$_->() for values %{ $SIG_CB{$signal} || {} };	1549	local $!;
		1550	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1551	undef $SIG_EV{$signal};
		1552	};
		1553
		1554	# can't do signal processing without introducing races in pure perl,
		1555	# so limit the signal latency.
		1556	_sig_add;
		1557	}
		1558
		1559	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1560	};
		1561
		1562	*AnyEvent::Base::signal::DESTROY = sub {
		1563	my ($signal, $cb) = @{$_[0]};
		1564
		1565	_sig_del;
		1566
		1567	delete $SIG_CB{$signal}{$cb};
		1568
		1569	$HAVE_ASYNC_INTERRUPT
		1570	? delete $SIG_ASY{$signal}
		1571	: # delete doesn't work with older perls - they then
		1572	# print weird messages, or just unconditionally exit
		1573	# instead of getting the default action.
		1574	undef $SIG{$signal}
		1575	unless keys %{ $SIG_CB{$signal} };
		1576	};
845	};	1577	};
846		1578	die if $@;
847	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1579	&signal
848	}
849
850	sub AnyEvent::Base::Signal::DESTROY {
851	my ($signal, $cb) = @{$_[0]};
852
853	delete $SIG_CB{$signal}{$cb};
854
855	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };
856	}	1580	}
857		1581
858	# default implementation for ->child	1582	# default implementation for ->child
859		1583
860	our %PID_CB;	1584	our %PID_CB;
861	our $CHLD_W;	1585	our $CHLD_W;
862	our $CHLD_DELAY_W;	1586	our $CHLD_DELAY_W;
863	our $PID_IDLE;
864	our $WNOHANG;	1587	our $WNOHANG;
865		1588
866	sub _child_wait {	1589	sub _emit_childstatus($$) {
867	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1590	my (undef, $rpid, $rstatus) = @_;
		1591
		1592	$_->($rpid, $rstatus)
868	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1593	for values %{ $PID_CB{$rpid} || {} },
869	(values %{ $PID_CB{0} || {} });	1594	values %{ $PID_CB{0} || {} };
870	}
871
872	undef $PID_IDLE;
873	}	1595	}
874		1596
875	sub _sigchld {	1597	sub _sigchld {
876	# make sure we deliver these changes "synchronous" with the event loop.	1598	my $pid;
877	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {	1599
878	undef $CHLD_DELAY_W;	1600	AnyEvent->_emit_childstatus ($pid, $?)
879	&_child_wait;	1601	while ($pid = waitpid -1, $WNOHANG) > 0;
880	});
881	}	1602	}
882		1603
883	sub child {	1604	sub child {
884	my (undef, %arg) = @_;	1605	my (undef, %arg) = @_;
885		1606
886	defined (my $pid = $arg{pid} + 0)	1607	defined (my $pid = $arg{pid} + 0)
887	or Carp::croak "required option 'pid' is missing";	1608	or Carp::croak "required option 'pid' is missing";
888		1609
889	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1610	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
890		1611
891	unless ($WNOHANG) {	1612	# WNOHANG is almost cetrainly 1 everywhere
892	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;	1613	$WNOHANG ||= $^O =~ /^(?:openbsd|netbsd|linux|freebsd|cygwin|MSWin32)$/
893	}	1614	? 1
		1615	: eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
894		1616
895	unless ($CHLD_W) {	1617	unless ($CHLD_W) {
896	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1618	$CHLD_W = AE::signal CHLD => \&_sigchld;
897	# child could be a zombie already, so make at least one round	1619	# child could be a zombie already, so make at least one round
898	&_sigchld;	1620	&_sigchld;
899	}	1621	}
900		1622
901	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	1623	bless [$pid, $arg{cb}], "AnyEvent::Base::child"
902	}	1624	}
903		1625
904	sub AnyEvent::Base::Child::DESTROY {	1626	sub AnyEvent::Base::child::DESTROY {
905	my ($pid, $cb) = @{$_[0]};	1627	my ($pid, $cb) = @{$_[0]};
906		1628
907	delete $PID_CB{$pid}{$cb};	1629	delete $PID_CB{$pid}{$cb};
908	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1630	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
909		1631
910	undef $CHLD_W unless keys %PID_CB;	1632	undef $CHLD_W unless keys %PID_CB;
911	}	1633	}
912		1634
		1635	# idle emulation is done by simply using a timer, regardless
		1636	# of whether the process is idle or not, and not letting
		1637	# the callback use more than 50% of the time.
		1638	sub idle {
		1639	my (undef, %arg) = @_;
		1640
		1641	my ($cb, $w, $rcb) = $arg{cb};
		1642
		1643	$rcb = sub {
		1644	if ($cb) {
		1645	$w = _time;
		1646	&$cb;
		1647	$w = _time - $w;
		1648
		1649	# never use more then 50% of the time for the idle watcher,
		1650	# within some limits
		1651	$w = 0.0001 if $w < 0.0001;
		1652	$w = 5 if $w > 5;
		1653
		1654	$w = AE::timer $w, 0, $rcb;
		1655	} else {
		1656	# clean up...
		1657	undef $w;
		1658	undef $rcb;
		1659	}
		1660	};
		1661
		1662	$w = AE::timer 0.05, 0, $rcb;
		1663
		1664	bless \\$cb, "AnyEvent::Base::idle"
		1665	}
		1666
		1667	sub AnyEvent::Base::idle::DESTROY {
		1668	undef $${$_[0]};
		1669	}
		1670
913	package AnyEvent::CondVar;	1671	package AnyEvent::CondVar;
914		1672
915	our @ISA = AnyEvent::CondVar::Base::;	1673	our @ISA = AnyEvent::CondVar::Base::;
916		1674
917	package AnyEvent::CondVar::Base;	1675	package AnyEvent::CondVar::Base;
		1676
		1677	#use overload
		1678	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1679	# fallback => 1;
		1680
		1681	# save 300+ kilobytes by dirtily hardcoding overloading
		1682	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1683	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1684	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1685	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1686
		1687	our $WAITING;
918		1688
919	sub _send {	1689	sub _send {
920	# nop	1690	# nop
921	}	1691	}
922		1692
…		…
935	sub ready {	1705	sub ready {
936	$_[0]{_ae_sent}	1706	$_[0]{_ae_sent}
937	}	1707	}
938		1708
939	sub _wait {	1709	sub _wait {
		1710	$WAITING
		1711	and !$_[0]{_ae_sent}
		1712	and Carp::croak "AnyEvent::CondVar: recursive blocking wait detected";
		1713
		1714	local $WAITING = 1;
940	AnyEvent->one_event while !$_[0]{_ae_sent};	1715	AnyEvent->one_event while !$_[0]{_ae_sent};
941	}	1716	}
942		1717
943	sub recv {	1718	sub recv {
944	$_[0]->_wait;	1719	$_[0]->_wait;
…		…
946	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};	1721	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
947	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]	1722	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
948	}	1723	}
949		1724
950	sub cb {	1725	sub cb {
951	$_[0]{_ae_cb} = $_[1] if @_ > 1;	1726	my $cv = shift;
		1727
		1728	@_
		1729	and $cv->{_ae_cb} = shift
		1730	and $cv->{_ae_sent}
		1731	and (delete $cv->{_ae_cb})->($cv);
		1732
952	$_[0]{_ae_cb}	1733	$cv->{_ae_cb}
953	}	1734	}
954		1735
955	sub begin {	1736	sub begin {
956	++$_[0]{_ae_counter};	1737	++$_[0]{_ae_counter};
957	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;	1738	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
…		…
963	}	1744	}
964		1745
965	# undocumented/compatibility with pre-3.4	1746	# undocumented/compatibility with pre-3.4
966	*broadcast = \&send;	1747	*broadcast = \&send;
967	*wait = \&_wait;	1748	*wait = \&_wait;
		1749
		1750	=head1 ERROR AND EXCEPTION HANDLING
		1751
		1752	In general, AnyEvent does not do any error handling - it relies on the
		1753	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1754	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1755	checking of all AnyEvent methods, however, which is highly useful during
		1756	development.
		1757
		1758	As for exception handling (i.e. runtime errors and exceptions thrown while
		1759	executing a callback), this is not only highly event-loop specific, but
		1760	also not in any way wrapped by this module, as this is the job of the main
		1761	program.
		1762
		1763	The pure perl event loop simply re-throws the exception (usually
		1764	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1765	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1766	so on.
		1767
		1768	=head1 ENVIRONMENT VARIABLES
		1769
		1770	The following environment variables are used by this module or its
		1771	submodules.
		1772
		1773	Note that AnyEvent will remove I<all> environment variables starting with
		1774	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		1775	enabled.
		1776
		1777	=over 4
		1778
		1779	=item C<PERL_ANYEVENT_VERBOSE>
		1780
		1781	By default, AnyEvent will be completely silent except in fatal
		1782	conditions. You can set this environment variable to make AnyEvent more
		1783	talkative.
		1784
		1785	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1786	conditions, such as not being able to load the event model specified by
		1787	C<PERL_ANYEVENT_MODEL>.
		1788
		1789	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1790	model it chooses.
		1791
		1792	When set to C<8> or higher, then AnyEvent will report extra information on
		1793	which optional modules it loads and how it implements certain features.
		1794
		1795	=item C<PERL_ANYEVENT_STRICT>
		1796
		1797	AnyEvent does not do much argument checking by default, as thorough
		1798	argument checking is very costly. Setting this variable to a true value
		1799	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1800	check the arguments passed to most method calls. If it finds any problems,
		1801	it will croak.
		1802
		1803	In other words, enables "strict" mode.
		1804
		1805	Unlike C<use strict> (or it's modern cousin, C<< use L<common::sense>
		1806	>>, it is definitely recommended to keep it off in production. Keeping
		1807	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		1808	can be very useful, however.
		1809
		1810	=item C<PERL_ANYEVENT_MODEL>
		1811
		1812	This can be used to specify the event model to be used by AnyEvent, before
		1813	auto detection and -probing kicks in. It must be a string consisting
		1814	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1815	and the resulting module name is loaded and if the load was successful,
		1816	used as event model. If it fails to load AnyEvent will proceed with
		1817	auto detection and -probing.
		1818
		1819	This functionality might change in future versions.
		1820
		1821	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1822	could start your program like this:
		1823
		1824	PERL_ANYEVENT_MODEL=Perl perl ...
		1825
		1826	=item C<PERL_ANYEVENT_PROTOCOLS>
		1827
		1828	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1829	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1830	of auto probing).
		1831
		1832	Must be set to a comma-separated list of protocols or address families,
		1833	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1834	used, and preference will be given to protocols mentioned earlier in the
		1835	list.
		1836
		1837	This variable can effectively be used for denial-of-service attacks
		1838	against local programs (e.g. when setuid), although the impact is likely
		1839	small, as the program has to handle conenction and other failures anyways.
		1840
		1841	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1842	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1843	- only support IPv4, never try to resolve or contact IPv6
		1844	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1845	IPv6, but prefer IPv6 over IPv4.
		1846
		1847	=item C<PERL_ANYEVENT_EDNS0>
		1848
		1849	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1850	for DNS. This extension is generally useful to reduce DNS traffic, but
		1851	some (broken) firewalls drop such DNS packets, which is why it is off by
		1852	default.
		1853
		1854	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1855	EDNS0 in its DNS requests.
		1856
		1857	=item C<PERL_ANYEVENT_MAX_FORKS>
		1858
		1859	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1860	will create in parallel.
		1861
		1862	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		1863
		1864	The default value for the C<max_outstanding> parameter for the default DNS
		1865	resolver - this is the maximum number of parallel DNS requests that are
		1866	sent to the DNS server.
		1867
		1868	=item C<PERL_ANYEVENT_RESOLV_CONF>
		1869
		1870	The file to use instead of F</etc/resolv.conf> (or OS-specific
		1871	configuration) in the default resolver. When set to the empty string, no
		1872	default config will be used.
		1873
		1874	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		1875
		1876	When neither C<ca_file> nor C<ca_path> was specified during
		1877	L<AnyEvent::TLS> context creation, and either of these environment
		1878	variables exist, they will be used to specify CA certificate locations
		1879	instead of a system-dependent default.
		1880
		1881	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		1882
		1883	When these are set to C<1>, then the respective modules are not
		1884	loaded. Mostly good for testing AnyEvent itself.
		1885
		1886	=back
968		1887
969	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1888	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
970		1889
971	This is an advanced topic that you do not normally need to use AnyEvent in	1890	This is an advanced topic that you do not normally need to use AnyEvent in
972	a module. This section is only of use to event loop authors who want to	1891	a module. This section is only of use to event loop authors who want to
…		…
1006		1925
1007	I<rxvt-unicode> also cheats a bit by not providing blocking access to	1926	I<rxvt-unicode> also cheats a bit by not providing blocking access to
1008	condition variables: code blocking while waiting for a condition will	1927	condition variables: code blocking while waiting for a condition will
1009	C<die>. This still works with most modules/usages, and blocking calls must	1928	C<die>. This still works with most modules/usages, and blocking calls must
1010	not be done in an interactive application, so it makes sense.	1929	not be done in an interactive application, so it makes sense.
1011
1012	=head1 ENVIRONMENT VARIABLES
1013
1014	The following environment variables are used by this module:
1015
1016	=over 4
1017
1018	=item C<PERL_ANYEVENT_VERBOSE>
1019
1020	By default, AnyEvent will be completely silent except in fatal
1021	conditions. You can set this environment variable to make AnyEvent more
1022	talkative.
1023
1024	When set to C<1> or higher, causes AnyEvent to warn about unexpected
1025	conditions, such as not being able to load the event model specified by
1026	C<PERL_ANYEVENT_MODEL>.
1027
1028	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
1029	model it chooses.
1030
1031	=item C<PERL_ANYEVENT_MODEL>
1032
1033	This can be used to specify the event model to be used by AnyEvent, before
1034	autodetection and -probing kicks in. It must be a string consisting
1035	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
1036	and the resulting module name is loaded and if the load was successful,
1037	used as event model. If it fails to load AnyEvent will proceed with
1038	autodetection and -probing.
1039
1040	This functionality might change in future versions.
1041
1042	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
1043	could start your program like this:
1044
1045	PERL_ANYEVENT_MODEL=Perl perl ...
1046
1047	=item C<PERL_ANYEVENT_PROTOCOLS>
1048
1049	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
1050	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
1051	of autoprobing).
1052
1053	Must be set to a comma-separated list of protocols or address families,
1054	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
1055	used, and preference will be given to protocols mentioned earlier in the
1056	list.
1057
1058	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
1059	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
1060	- only support IPv4, never try to resolve or contact IPv6
1061	addressses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
1062	IPv6, but prefer IPv6 over IPv4.
1063
1064	=back
1065		1930
1066	=head1 EXAMPLE PROGRAM	1931	=head1 EXAMPLE PROGRAM
1067		1932
1068	The following program uses an I/O watcher to read data from STDIN, a timer	1933	The following program uses an I/O watcher to read data from STDIN, a timer
1069	to display a message once per second, and a condition variable to quit the	1934	to display a message once per second, and a condition variable to quit the
…		…
1082	warn "read: $input\n"; # output what has been read	1947	warn "read: $input\n"; # output what has been read
1083	$cv->send if $input =~ /^q/i; # quit program if /^q/i	1948	$cv->send if $input =~ /^q/i; # quit program if /^q/i
1084	},	1949	},
1085	);	1950	);
1086		1951
1087	my $time_watcher; # can only be used once
1088
1089	sub new_timer {
1090	$timer = AnyEvent->timer (after => 1, cb => sub {	1952	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
1091	warn "timeout\n"; # print 'timeout' about every second	1953	warn "timeout\n"; # print 'timeout' at most every second
1092	&new_timer; # and restart the time
1093	});	1954	});
1094	}
1095
1096	new_timer; # create first timer
1097		1955
1098	$cv->recv; # wait until user enters /^q/i	1956	$cv->recv; # wait until user enters /^q/i
1099		1957
1100	=head1 REAL-WORLD EXAMPLE	1958	=head1 REAL-WORLD EXAMPLE
1101		1959
…		…
1153	syswrite $txn->{fh}, $txn->{request}	2011	syswrite $txn->{fh}, $txn->{request}
1154	or die "connection or write error";	2012	or die "connection or write error";
1155	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	2013	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
1156		2014
1157	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	2015	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
1158	result and signals any possible waiters that the request ahs finished:	2016	result and signals any possible waiters that the request has finished:
1159		2017
1160	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	2018	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
1161		2019
1162	if (end-of-file or data complete) {	2020	if (end-of-file or data complete) {
1163	$txn->{result} = $txn->{buf};	2021	$txn->{result} = $txn->{buf};
…		…
1171		2029
1172	$txn->{finished}->recv;	2030	$txn->{finished}->recv;
1173	return $txn->{result};	2031	return $txn->{result};
1174		2032
1175	The actual code goes further and collects all errors (C<die>s, exceptions)	2033	The actual code goes further and collects all errors (C<die>s, exceptions)
1176	that occured during request processing. The C<result> method detects	2034	that occurred during request processing. The C<result> method detects
1177	whether an exception as thrown (it is stored inside the $txn object)	2035	whether an exception as thrown (it is stored inside the $txn object)
1178	and just throws the exception, which means connection errors and other	2036	and just throws the exception, which means connection errors and other
1179	problems get reported tot he code that tries to use the result, not in a	2037	problems get reported tot he code that tries to use the result, not in a
1180	random callback.	2038	random callback.
1181		2039
…		…
1227	of various event loops I prepared some benchmarks.	2085	of various event loops I prepared some benchmarks.
1228		2086
1229	=head2 BENCHMARKING ANYEVENT OVERHEAD	2087	=head2 BENCHMARKING ANYEVENT OVERHEAD
1230		2088
1231	Here is a benchmark of various supported event models used natively and	2089	Here is a benchmark of various supported event models used natively and
1232	through anyevent. The benchmark creates a lot of timers (with a zero	2090	through AnyEvent. The benchmark creates a lot of timers (with a zero
1233	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,	2091	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
1234	which it is), lets them fire exactly once and destroys them again.	2092	which it is), lets them fire exactly once and destroys them again.
1235		2093
1236	Source code for this benchmark is found as F<eg/bench> in the AnyEvent	2094	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
1237	distribution.	2095	distribution. It uses the L<AE> interface, which makes a real difference
		2096	for the EV and Perl backends only.
1238		2097
1239	=head3 Explanation of the columns	2098	=head3 Explanation of the columns
1240		2099
1241	I<watcher> is the number of event watchers created/destroyed. Since	2100	I<watcher> is the number of event watchers created/destroyed. Since
1242	different event models feature vastly different performances, each event	2101	different event models feature vastly different performances, each event
…		…
1263	watcher.	2122	watcher.
1264		2123
1265	=head3 Results	2124	=head3 Results
1266		2125
1267	name watchers bytes create invoke destroy comment	2126	name watchers bytes create invoke destroy comment
1268	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	2127	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
1269	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	2128	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
1270	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	2129	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
1271	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	2130	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
1272	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	2131	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
1273	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers	2132	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
		2133	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
		2134	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
1274	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	2135	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
1275	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	2136	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
1276	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	2137	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
1277	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	2138	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
1278		2139
1279	=head3 Discussion	2140	=head3 Discussion
1280		2141
1281	The benchmark does I<not> measure scalability of the event loop very	2142	The benchmark does I<not> measure scalability of the event loop very
1282	well. For example, a select-based event loop (such as the pure perl one)	2143	well. For example, a select-based event loop (such as the pure perl one)
…		…
1294	benchmark machine, handling an event takes roughly 1600 CPU cycles with	2155	benchmark machine, handling an event takes roughly 1600 CPU cycles with
1295	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU	2156	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
1296	cycles with POE.	2157	cycles with POE.
1297		2158
1298	C<EV> is the sole leader regarding speed and memory use, which are both	2159	C<EV> is the sole leader regarding speed and memory use, which are both
1299	maximal/minimal, respectively. Even when going through AnyEvent, it uses	2160	maximal/minimal, respectively. When using the L<AE> API there is zero
		2161	overhead (when going through the AnyEvent API create is about 5-6 times
		2162	slower, with other times being equal, so still uses far less memory than
1300	far less memory than any other event loop and is still faster than Event	2163	any other event loop and is still faster than Event natively).
1301	natively.
1302		2164
1303	The pure perl implementation is hit in a few sweet spots (both the	2165	The pure perl implementation is hit in a few sweet spots (both the
1304	constant timeout and the use of a single fd hit optimisations in the perl	2166	constant timeout and the use of a single fd hit optimisations in the perl
1305	interpreter and the backend itself). Nevertheless this shows that it	2167	interpreter and the backend itself). Nevertheless this shows that it
1306	adds very little overhead in itself. Like any select-based backend its	2168	adds very little overhead in itself. Like any select-based backend its
1307	performance becomes really bad with lots of file descriptors (and few of	2169	performance becomes really bad with lots of file descriptors (and few of
1308	them active), of course, but this was not subject of this benchmark.	2170	them active), of course, but this was not subject of this benchmark.
1309		2171
1310	The C<Event> module has a relatively high setup and callback invocation	2172	The C<Event> module has a relatively high setup and callback invocation
1311	cost, but overall scores in on the third place.	2173	cost, but overall scores in on the third place.
		2174
		2175	C<IO::Async> performs admirably well, about on par with C<Event>, even
		2176	when using its pure perl backend.
1312		2177
1313	C<Glib>'s memory usage is quite a bit higher, but it features a	2178	C<Glib>'s memory usage is quite a bit higher, but it features a
1314	faster callback invocation and overall ends up in the same class as	2179	faster callback invocation and overall ends up in the same class as
1315	C<Event>. However, Glib scales extremely badly, doubling the number of	2180	C<Event>. However, Glib scales extremely badly, doubling the number of
1316	watchers increases the processing time by more than a factor of four,	2181	watchers increases the processing time by more than a factor of four,
…		…
1360		2225
1361	=back	2226	=back
1362		2227
1363	=head2 BENCHMARKING THE LARGE SERVER CASE	2228	=head2 BENCHMARKING THE LARGE SERVER CASE
1364		2229
1365	This benchmark atcually benchmarks the event loop itself. It works by	2230	This benchmark actually benchmarks the event loop itself. It works by
1366	creating a number of "servers": each server consists of a socketpair, a	2231	creating a number of "servers": each server consists of a socket pair, a
1367	timeout watcher that gets reset on activity (but never fires), and an I/O	2232	timeout watcher that gets reset on activity (but never fires), and an I/O
1368	watcher waiting for input on one side of the socket. Each time the socket	2233	watcher waiting for input on one side of the socket. Each time the socket
1369	watcher reads a byte it will write that byte to a random other "server".	2234	watcher reads a byte it will write that byte to a random other "server".
1370		2235
1371	The effect is that there will be a lot of I/O watchers, only part of which	2236	The effect is that there will be a lot of I/O watchers, only part of which
1372	are active at any one point (so there is a constant number of active	2237	are active at any one point (so there is a constant number of active
1373	fds for each loop iterstaion, but which fds these are is random). The	2238	fds for each loop iteration, but which fds these are is random). The
1374	timeout is reset each time something is read because that reflects how	2239	timeout is reset each time something is read because that reflects how
1375	most timeouts work (and puts extra pressure on the event loops).	2240	most timeouts work (and puts extra pressure on the event loops).
1376		2241
1377	In this benchmark, we use 10000 socketpairs (20000 sockets), of which 100	2242	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
1378	(1%) are active. This mirrors the activity of large servers with many	2243	(1%) are active. This mirrors the activity of large servers with many
1379	connections, most of which are idle at any one point in time.	2244	connections, most of which are idle at any one point in time.
1380		2245
1381	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent	2246	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
1382	distribution.	2247	distribution. It uses the L<AE> interface, which makes a real difference
		2248	for the EV and Perl backends only.
1383		2249
1384	=head3 Explanation of the columns	2250	=head3 Explanation of the columns
1385		2251
1386	I<sockets> is the number of sockets, and twice the number of "servers" (as	2252	I<sockets> is the number of sockets, and twice the number of "servers" (as
1387	each server has a read and write socket end).	2253	each server has a read and write socket end).
1388		2254
1389	I<create> is the time it takes to create a socketpair (which is	2255	I<create> is the time it takes to create a socket pair (which is
1390	nontrivial) and two watchers: an I/O watcher and a timeout watcher.	2256	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
1391		2257
1392	I<request>, the most important value, is the time it takes to handle a	2258	I<request>, the most important value, is the time it takes to handle a
1393	single "request", that is, reading the token from the pipe and forwarding	2259	single "request", that is, reading the token from the pipe and forwarding
1394	it to another server. This includes deleting the old timeout and creating	2260	it to another server. This includes deleting the old timeout and creating
1395	a new one that moves the timeout into the future.	2261	a new one that moves the timeout into the future.
1396		2262
1397	=head3 Results	2263	=head3 Results
1398		2264
1399	name sockets create request	2265	name sockets create request
1400	EV 20000 69.01 11.16	2266	EV 20000 62.66 7.99
1401	Perl 20000 73.32 35.87	2267	Perl 20000 68.32 32.64
1402	Event 20000 212.62 257.32	2268	IOAsync 20000 174.06 101.15 epoll
1403	Glib 20000 651.16 1896.30	2269	IOAsync 20000 174.67 610.84 poll
		2270	Event 20000 202.69 242.91
		2271	Glib 20000 557.01 1689.52
1404	POE 20000 349.67 12317.24 uses POE::Loop::Event	2272	POE 20000 341.54 12086.32 uses POE::Loop::Event
1405		2273
1406	=head3 Discussion	2274	=head3 Discussion
1407		2275
1408	This benchmark I<does> measure scalability and overall performance of the	2276	This benchmark I<does> measure scalability and overall performance of the
1409	particular event loop.	2277	particular event loop.
…		…
1411	EV is again fastest. Since it is using epoll on my system, the setup time	2279	EV is again fastest. Since it is using epoll on my system, the setup time
1412	is relatively high, though.	2280	is relatively high, though.
1413		2281
1414	Perl surprisingly comes second. It is much faster than the C-based event	2282	Perl surprisingly comes second. It is much faster than the C-based event
1415	loops Event and Glib.	2283	loops Event and Glib.
		2284
		2285	IO::Async performs very well when using its epoll backend, and still quite
		2286	good compared to Glib when using its pure perl backend.
1416		2287
1417	Event suffers from high setup time as well (look at its code and you will	2288	Event suffers from high setup time as well (look at its code and you will
1418	understand why). Callback invocation also has a high overhead compared to	2289	understand why). Callback invocation also has a high overhead compared to
1419	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event	2290	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
1420	uses select or poll in basically all documented configurations.	2291	uses select or poll in basically all documented configurations.
…		…
1467	speed most when you have lots of watchers, not when you only have a few of	2338	speed most when you have lots of watchers, not when you only have a few of
1468	them).	2339	them).
1469		2340
1470	EV is again fastest.	2341	EV is again fastest.
1471		2342
1472	Perl again comes second. It is noticably faster than the C-based event	2343	Perl again comes second. It is noticeably faster than the C-based event
1473	loops Event and Glib, although the difference is too small to really	2344	loops Event and Glib, although the difference is too small to really
1474	matter.	2345	matter.
1475		2346
1476	POE also performs much better in this case, but is is still far behind the	2347	POE also performs much better in this case, but is is still far behind the
1477	others.	2348	others.
…		…
1480		2351
1481	=over 4	2352	=over 4
1482		2353
1483	=item * C-based event loops perform very well with small number of	2354	=item * C-based event loops perform very well with small number of
1484	watchers, as the management overhead dominates.	2355	watchers, as the management overhead dominates.
		2356
		2357	=back
		2358
		2359	=head2 THE IO::Lambda BENCHMARK
		2360
		2361	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2362	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2363	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2364	shouldn't come as a surprise to anybody). As such, the benchmark is
		2365	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2366	very optimal. But how would AnyEvent compare when used without the extra
		2367	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2368
		2369	The benchmark itself creates an echo-server, and then, for 500 times,
		2370	connects to the echo server, sends a line, waits for the reply, and then
		2371	creates the next connection. This is a rather bad benchmark, as it doesn't
		2372	test the efficiency of the framework or much non-blocking I/O, but it is a
		2373	benchmark nevertheless.
		2374
		2375	name runtime
		2376	Lambda/select 0.330 sec
		2377	+ optimized 0.122 sec
		2378	Lambda/AnyEvent 0.327 sec
		2379	+ optimized 0.138 sec
		2380	Raw sockets/select 0.077 sec
		2381	POE/select, components 0.662 sec
		2382	POE/select, raw sockets 0.226 sec
		2383	POE/select, optimized 0.404 sec
		2384
		2385	AnyEvent/select/nb 0.085 sec
		2386	AnyEvent/EV/nb 0.068 sec
		2387	+state machine 0.134 sec
		2388
		2389	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2390	benchmarks actually make blocking connects and use 100% blocking I/O,
		2391	defeating the purpose of an event-based solution. All of the newly
		2392	written AnyEvent benchmarks use 100% non-blocking connects (using
		2393	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2394	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2395	generally require a lot more bookkeeping and event handling than blocking
		2396	connects (which involve a single syscall only).
		2397
		2398	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2399	offers similar expressive power as POE and IO::Lambda, using conventional
		2400	Perl syntax. This means that both the echo server and the client are 100%
		2401	non-blocking, further placing it at a disadvantage.
		2402
		2403	As you can see, the AnyEvent + EV combination even beats the
		2404	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2405	backend easily beats IO::Lambda and POE.
		2406
		2407	And even the 100% non-blocking version written using the high-level (and
		2408	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda
		2409	higher level ("unoptimised") abstractions by a large margin, even though
		2410	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
		2411
		2412	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2413	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2414	part of the IO::Lambda distribution and were used without any changes.
		2415
		2416
		2417	=head1 SIGNALS
		2418
		2419	AnyEvent currently installs handlers for these signals:
		2420
		2421	=over 4
		2422
		2423	=item SIGCHLD
		2424
		2425	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2426	emulation for event loops that do not support them natively. Also, some
		2427	event loops install a similar handler.
		2428
		2429	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2430	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2431
		2432	=item SIGPIPE
		2433
		2434	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2435	when AnyEvent gets loaded.
		2436
		2437	The rationale for this is that AnyEvent users usually do not really depend
		2438	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2439	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2440	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2441	some random socket.
		2442
		2443	The rationale for installing a no-op handler as opposed to ignoring it is
		2444	that this way, the handler will be restored to defaults on exec.
		2445
		2446	Feel free to install your own handler, or reset it to defaults.
		2447
		2448	=back
		2449
		2450	=cut
		2451
		2452	undef $SIG{CHLD}
		2453	if $SIG{CHLD} eq 'IGNORE';
		2454
		2455	$SIG{PIPE} = sub { }
		2456	unless defined $SIG{PIPE};
		2457
		2458	=head1 RECOMMENDED/OPTIONAL MODULES
		2459
		2460	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2461	it's built-in modules) are required to use it.
		2462
		2463	That does not mean that AnyEvent won't take advantage of some additional
		2464	modules if they are installed.
		2465
		2466	This section explains which additional modules will be used, and how they
		2467	affect AnyEvent's operation.
		2468
		2469	=over 4
		2470
		2471	=item L<Async::Interrupt>
		2472
		2473	This slightly arcane module is used to implement fast signal handling: To
		2474	my knowledge, there is no way to do completely race-free and quick
		2475	signal handling in pure perl. To ensure that signals still get
		2476	delivered, AnyEvent will start an interval timer to wake up perl (and
		2477	catch the signals) with some delay (default is 10 seconds, look for
		2478	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2479
		2480	If this module is available, then it will be used to implement signal
		2481	catching, which means that signals will not be delayed, and the event loop
		2482	will not be interrupted regularly, which is more efficient (and good for
		2483	battery life on laptops).
		2484
		2485	This affects not just the pure-perl event loop, but also other event loops
		2486	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2487
		2488	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2489	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2490	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2491	does nothing for those backends.
		2492
		2493	=item L<EV>
		2494
		2495	This module isn't really "optional", as it is simply one of the backend
		2496	event loops that AnyEvent can use. However, it is simply the best event
		2497	loop available in terms of features, speed and stability: It supports
		2498	the AnyEvent API optimally, implements all the watcher types in XS, does
		2499	automatic timer adjustments even when no monotonic clock is available,
		2500	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2501	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2502	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2503
		2504	=item L<Guard>
		2505
		2506	The guard module, when used, will be used to implement
		2507	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2508	lot less memory), but otherwise doesn't affect guard operation much. It is
		2509	purely used for performance.
		2510
		2511	=item L<JSON> and L<JSON::XS>
		2512
		2513	One of these modules is required when you want to read or write JSON data
		2514	via L<AnyEvent::Handle>. It is also written in pure-perl, but can take
		2515	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2516
		2517	In fact, L<AnyEvent::Handle> will use L<JSON::XS> by default if it is
		2518	installed.
		2519
		2520	=item L<Net::SSLeay>
		2521
		2522	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2523	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2524	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2525
		2526	=item L<Time::HiRes>
		2527
		2528	This module is part of perl since release 5.008. It will be used when the
		2529	chosen event library does not come with a timing source on it's own. The
		2530	pure-perl event loop (L<AnyEvent::Impl::Perl>) will additionally use it to
		2531	try to use a monotonic clock for timing stability.
1485		2532
1486	=back	2533	=back
1487		2534
1488		2535
1489	=head1 FORK	2536	=head1 FORK
1490		2537
1491	Most event libraries are not fork-safe. The ones who are usually are	2538	Most event libraries are not fork-safe. The ones who are usually are
1492	because they rely on inefficient but fork-safe C<select> or C<poll>	2539	because they rely on inefficient but fork-safe C<select> or C<poll>
1493	calls. Only L<EV> is fully fork-aware.	2540	calls. Only L<EV> is fully fork-aware.
1494		2541
		2542	This means that, in general, you cannot fork and do event processing
		2543	in the child if a watcher was created before the fork (which in turn
		2544	initialises the event library).
		2545
1495	If you have to fork, you must either do so I<before> creating your first	2546	If you have to fork, you must either do so I<before> creating your first
1496	watcher OR you must not use AnyEvent at all in the child.	2547	watcher OR you must not use AnyEvent at all in the child OR you must do
		2548	something completely out of the scope of AnyEvent.
		2549
		2550	The problem of doing event processing in the parent I<and> the child
		2551	is much more complicated: even for backends that I<are> fork-aware or
		2552	fork-safe, their behaviour is not usually what you want: fork clones all
		2553	watchers, that means all timers, I/O watchers etc. are active in both
		2554	parent and child, which is almost never what you want.
1497		2555
1498		2556
1499	=head1 SECURITY CONSIDERATIONS	2557	=head1 SECURITY CONSIDERATIONS
1500		2558
1501	AnyEvent can be forced to load any event model via	2559	AnyEvent can be forced to load any event model via
…		…
1506	specified in the variable.	2564	specified in the variable.
1507		2565
1508	You can make AnyEvent completely ignore this variable by deleting it	2566	You can make AnyEvent completely ignore this variable by deleting it
1509	before the first watcher gets created, e.g. with a C<BEGIN> block:	2567	before the first watcher gets created, e.g. with a C<BEGIN> block:
1510		2568
1511	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	2569	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1512		2570
1513	use AnyEvent;	2571	use AnyEvent;
1514		2572
1515	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can	2573	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1516	be used to probe what backend is used and gain other information (which is	2574	be used to probe what backend is used and gain other information (which is
1517	probably even less useful to an attacker than PERL_ANYEVENT_MODEL).	2575	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2576	$ENV{PERL_ANYEVENT_STRICT}.
		2577
		2578	Note that AnyEvent will remove I<all> environment variables starting with
		2579	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2580	enabled.
		2581
		2582
		2583	=head1 BUGS
		2584
		2585	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2586	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2587	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2588	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2589	pronounced).
1518		2590
1519		2591
1520	=head1 SEE ALSO	2592	=head1 SEE ALSO
1521		2593
1522	Utility functions: L<AnyEvent::Util>.	2594	Utility functions: L<AnyEvent::Util>.
…		…
1525	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.	2597	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
1526		2598
1527	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,	2599	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
1528	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,	2600	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
1529	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,	2601	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1530	L<AnyEvent::Impl::POE>.	2602	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>, L<Anyevent::Impl::Irssi>.
1531		2603
1532	Non-blocking file handles, sockets, TCP clients and	2604	Non-blocking file handles, sockets, TCP clients and
1533	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>.	2605	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
1534		2606
1535	Asynchronous DNS: L<AnyEvent::DNS>.	2607	Asynchronous DNS: L<AnyEvent::DNS>.
1536		2608
1537	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,	2609	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>,
		2610	L<Coro::Event>,
1538		2611
1539	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>, L<AnyEvent::DNS>.	2612	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::XMPP>,
		2613	L<AnyEvent::HTTP>.
1540		2614
1541		2615
1542	=head1 AUTHOR	2616	=head1 AUTHOR
1543		2617
1544	Marc Lehmann <schmorp@schmorp.de>	2618	Marc Lehmann <schmorp@schmorp.de>
1545	http://home.schmorp.de/	2619	http://home.schmorp.de/
1546		2620
1547	=cut	2621	=cut
1548		2622
1549	1	2623	1
1550		2624

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