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Revision 1.113 by root, Sat May 10 20:30:35 2008 UTC vs.
Revision 1.296 by root, Tue Nov 17 01:19:49 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
		35	$w->send; # wake up current and all future recv's
20	$w->wait; # enters "main loop" till $condvar gets ->send	36	$w->recv; # enters "main loop" till $condvar gets ->send
21	$w->send; # wake up current and all future wait's	37	# use a condvar in callback mode:
		38	$w->cb (sub { $_[0]->recv });
		39
		40	=head1 INTRODUCTION/TUTORIAL
		41
		42	This manpage is mainly a reference manual. If you are interested
		43	in a tutorial or some gentle introduction, have a look at the
		44	L<AnyEvent::Intro> manpage.
		45
		46	=head1 SUPPORT
		47
		48	There is a mailinglist for discussing all things AnyEvent, and an IRC
		49	channel, too.
		50
		51	See the AnyEvent project page at the B<Schmorpforge Ta-Sa Software
		52	Repository>, at L<http://anyevent.schmorp.de>, for more info.
22		53
23	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)	54	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
24		55
25	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	56	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
26	nowadays. So what is different about AnyEvent?	57	nowadays. So what is different about AnyEvent?
27		58
28	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of	59	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
29	policy> and AnyEvent is I<small and efficient>.	60	policy> and AnyEvent is I<small and efficient>.
30		61
31	First and foremost, I<AnyEvent is not an event model> itself, it only	62	First and foremost, I<AnyEvent is not an event model> itself, it only
32	interfaces to whatever event model the main program happens to use in a	63	interfaces to whatever event model the main program happens to use, in a
33	pragmatic way. For event models and certain classes of immortals alike,	64	pragmatic way. For event models and certain classes of immortals alike,
34	the statement "there can only be one" is a bitter reality: In general,	65	the statement "there can only be one" is a bitter reality: In general,
35	only one event loop can be active at the same time in a process. AnyEvent	66	only one event loop can be active at the same time in a process. AnyEvent
36	helps hiding the differences between those event loops.	67	cannot change this, but it can hide the differences between those event
		68	loops.
37		69
38	The goal of AnyEvent is to offer module authors the ability to do event	70	The goal of AnyEvent is to offer module authors the ability to do event
39	programming (waiting for I/O or timer events) without subscribing to a	71	programming (waiting for I/O or timer events) without subscribing to a
40	religion, a way of living, and most importantly: without forcing your	72	religion, a way of living, and most importantly: without forcing your
41	module users into the same thing by forcing them to use the same event	73	module users into the same thing by forcing them to use the same event
42	model you use.	74	model you use.
43		75
44	For modules like POE or IO::Async (which is a total misnomer as it is	76	For modules like POE or IO::Async (which is a total misnomer as it is
45	actually doing all I/O I<synchronously>...), using them in your module is	77	actually doing all I/O I<synchronously>...), using them in your module is
46	like joining a cult: After you joined, you are dependent on them and you	78	like joining a cult: After you joined, you are dependent on them and you
47	cannot use anything else, as it is simply incompatible to everything that	79	cannot use anything else, as they are simply incompatible to everything
48	isn't itself. What's worse, all the potential users of your module are	80	that isn't them. What's worse, all the potential users of your
49	I<also> forced to use the same event loop you use.	81	module are I<also> forced to use the same event loop you use.
50		82
51	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	83	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
52	fine. AnyEvent + Tk works fine etc. etc. but none of these work together	84	fine. AnyEvent + Tk works fine etc. etc. but none of these work together
53	with the rest: POE + IO::Async? no go. Tk + Event? no go. Again: if	85	with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if
54	your module uses one of those, every user of your module has to use it,	86	your module uses one of those, every user of your module has to use it,
55	too. But if your module uses AnyEvent, it works transparently with all	87	too. But if your module uses AnyEvent, it works transparently with all
56	event models it supports (including stuff like POE and IO::Async, as long	88	event models it supports (including stuff like IO::Async, as long as those
57	as those use one of the supported event loops. It is trivial to add new	89	use one of the supported event loops. It is trivial to add new event loops
58	event loops to AnyEvent, too, so it is future-proof).	90	to AnyEvent, too, so it is future-proof).
59		91
60	In addition to being free of having to use I<the one and only true event	92	In addition to being free of having to use I<the one and only true event
61	model>, AnyEvent also is free of bloat and policy: with POE or similar	93	model>, AnyEvent also is free of bloat and policy: with POE or similar
62	modules, you get an enourmous amount of code and strict rules you have to	94	modules, you get an enormous amount of code and strict rules you have to
63	follow. AnyEvent, on the other hand, is lean and up to the point, by only	95	follow. AnyEvent, on the other hand, is lean and up to the point, by only
64	offering the functionality that is necessary, in as thin as a wrapper as	96	offering the functionality that is necessary, in as thin as a wrapper as
65	technically possible.	97	technically possible.
66		98
		99	Of course, AnyEvent comes with a big (and fully optional!) toolbox
		100	of useful functionality, such as an asynchronous DNS resolver, 100%
		101	non-blocking connects (even with TLS/SSL, IPv6 and on broken platforms
		102	such as Windows) and lots of real-world knowledge and workarounds for
		103	platform bugs and differences.
		104
67	Of course, if you want lots of policy (this can arguably be somewhat	105	Now, if you I<do want> lots of policy (this can arguably be somewhat
68	useful) and you want to force your users to use the one and only event	106	useful) and you want to force your users to use the one and only event
69	model, you should I<not> use this module.	107	model, you should I<not> use this module.
70		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 $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
256		407
		408	=head3 Signal Races, Delays and Workarounds
		409
		410	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		411	callbacks to signals in a generic way, which is a pity, as you cannot
		412	do race-free signal handling in perl, requiring C libraries for
		413	this. AnyEvent will try to do it's best, which means in some cases,
		414	signals will be delayed. The maximum time a signal might be delayed is
		415	specified in C<$AnyEvent::MAX_SIGNAL_LATENCY> (default: 10 seconds). This
		416	variable can be changed only before the first signal watcher is created,
		417	and should be left alone otherwise. This variable determines how often
		418	AnyEvent polls for signals (in case a wake-up was missed). Higher values
		419	will cause fewer spurious wake-ups, which is better for power and CPU
		420	saving.
		421
		422	All these problems can be avoided by installing the optional
		423	L<Async::Interrupt> module, which works with most event loops. It will not
		424	work with inherently broken event loops such as L<Event> or L<Event::Lib>
		425	(and not with L<POE> currently, as POE does it's own workaround with
		426	one-second latency). For those, you just have to suffer the delays.
		427
257	=head2 CHILD PROCESS WATCHERS	428	=head2 CHILD PROCESS WATCHERS
258		429
		430	$w = AnyEvent->child (pid => <process id>, cb => <callback>);
		431
259	You can also watch on a child process exit and catch its exit status.	432	You can also watch on a child process exit and catch its exit status.
260		433
261	The child process is specified by the C<pid> argument (if set to C<0>, it	434	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	435	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	436	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	437	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,	438	(stopped/continued).
266	you I<can> rely on child watcher callback arguments.	439
		440	The callback will be called with the pid and exit status (as returned by
		441	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		442	callback arguments.
		443
		444	This watcher type works by installing a signal handler for C<SIGCHLD>,
		445	and since it cannot be shared, nothing else should use SIGCHLD or reap
		446	random child processes (waiting for specific child processes, e.g. inside
		447	C<system>, is just fine).
267		448
268	There is a slight catch to child watchers, however: you usually start them	449	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	450	I<after> the child process was created, and this means the process could
270	have exited already (and no SIGCHLD will be sent anymore).	451	have exited already (and no SIGCHLD will be sent anymore).
271		452
272	Not all event models handle this correctly (POE doesn't), but even for	453	Not all event models handle this correctly (neither POE nor IO::Async do,
		454	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	455	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).	456	the process exits (i.e. before you fork in the first place). AnyEvent's
		457	pure perl event loop handles all cases correctly regardless of when you
		458	start the watcher.
275		459
276	This means you cannot create a child watcher as the very first thing in an	460	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	461	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>).	462	watcher before you C<fork> the child (alternatively, you can call
		463	C<AnyEvent::detect>).
		464
		465	As most event loops do not support waiting for child events, they will be
		466	emulated by AnyEvent in most cases, in which the latency and race problems
		467	mentioned in the description of signal watchers apply.
279		468
280	Example: fork a process and wait for it	469	Example: fork a process and wait for it
281		470
282	my $done = AnyEvent->condvar;	471	my $done = AnyEvent->condvar;
283		472
284	AnyEvent::detect; # force event module to be initialised
285
286	my $pid = fork or exit 5;	473	my $pid = fork or exit 5;
287		474
288	my $w = AnyEvent->child (	475	my $w = AnyEvent->child (
289	pid => $pid,	476	pid => $pid,
290	cb => sub {	477	cb => sub {
291	my ($pid, $status) = @_;	478	my ($pid, $status) = @_;
292	warn "pid $pid exited with status $status";	479	warn "pid $pid exited with status $status";
293	$done->send;	480	$done->send;
294	},	481	},
295	);	482	);
296		483
297	# do something else, then wait for process exit	484	# do something else, then wait for process exit
298	$done->wait;	485	$done->recv;
		486
		487	=head2 IDLE WATCHERS
		488
		489	$w = AnyEvent->idle (cb => <callback>);
		490
		491	Sometimes there is a need to do something, but it is not so important
		492	to do it instantly, but only when there is nothing better to do. This
		493	"nothing better to do" is usually defined to be "no other events need
		494	attention by the event loop".
		495
		496	Idle watchers ideally get invoked when the event loop has nothing
		497	better to do, just before it would block the process to wait for new
		498	events. Instead of blocking, the idle watcher is invoked.
		499
		500	Most event loops unfortunately do not really support idle watchers (only
		501	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		502	will simply call the callback "from time to time".
		503
		504	Example: read lines from STDIN, but only process them when the
		505	program is otherwise idle:
		506
		507	my @lines; # read data
		508	my $idle_w;
		509	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		510	push @lines, scalar <STDIN>;
		511
		512	# start an idle watcher, if not already done
		513	$idle_w ||= AnyEvent->idle (cb => sub {
		514	# handle only one line, when there are lines left
		515	if (my $line = shift @lines) {
		516	print "handled when idle: $line";
		517	} else {
		518	# otherwise disable the idle watcher again
		519	undef $idle_w;
		520	}
		521	});
		522	});
299		523
300	=head2 CONDITION VARIABLES	524	=head2 CONDITION VARIABLES
		525
		526	$cv = AnyEvent->condvar;
		527
		528	$cv->send (<list>);
		529	my @res = $cv->recv;
301		530
302	If you are familiar with some event loops you will know that all of them	531	If you are familiar with some event loops you will know that all of them
303	require you to run some blocking "loop", "run" or similar function that	532	require you to run some blocking "loop", "run" or similar function that
304	will actively watch for new events and call your callbacks.	533	will actively watch for new events and call your callbacks.
305		534
306	AnyEvent is different, it expects somebody else to run the event loop and	535	AnyEvent is slightly different: it expects somebody else to run the event
307	will only block when necessary (usually when told by the user).	536	loop and will only block when necessary (usually when told by the user).
308		537
309	The instrument to do that is called a "condition variable", so called	538	The instrument to do that is called a "condition variable", so called
310	because they represent a condition that must become true.	539	because they represent a condition that must become true.
		540
		541	Now is probably a good time to look at the examples further below.
311		542
312	Condition variables can be created by calling the C<< AnyEvent->condvar	543	Condition variables can be created by calling the C<< AnyEvent->condvar
313	>> method, usually without arguments. The only argument pair allowed is	544	>> method, usually without arguments. The only argument pair allowed is
314	C<cb>, which specifies a callback to be called when the condition variable	545	C<cb>, which specifies a callback to be called when the condition variable
315	becomes true.	546	becomes true, with the condition variable as the first argument (but not
		547	the results).
316		548
317	After creation, the conditon variable is "false" until it becomes "true"	549	After creation, the condition variable is "false" until it becomes "true"
318	by calling the C<send> method.	550	by calling the C<send> method (or calling the condition variable as if it
		551	were a callback, read about the caveats in the description for the C<<
		552	->send >> method).
319		553
320	Condition variables are similar to callbacks, except that you can	554	Condition variables are similar to callbacks, except that you can
321	optionally wait for them. They can also be called merge points - points	555	optionally wait for them. They can also be called merge points - points
322	in time where multiple outstandign events have been processed. And yet	556	in time where multiple outstanding events have been processed. And yet
323	another way to call them is transations - each condition variable can be	557	another way to call them is transactions - each condition variable can be
324	used to represent a transaction, which finishes at some point and delivers	558	used to represent a transaction, which finishes at some point and delivers
325	a result.	559	a result. And yet some people know them as "futures" - a promise to
		560	compute/deliver something that you can wait for.
326		561
327	Condition variables are very useful to signal that something has finished,	562	Condition variables are very useful to signal that something has finished,
328	for example, if you write a module that does asynchronous http requests,	563	for example, if you write a module that does asynchronous http requests,
329	then a condition variable would be the ideal candidate to signal the	564	then a condition variable would be the ideal candidate to signal the
330	availability of results. The user can either act when the callback is	565	availability of results. The user can either act when the callback is
331	called or can synchronously C<< ->wait >> for the results.	566	called or can synchronously C<< ->recv >> for the results.
332		567
333	You can also use them to simulate traditional event loops - for example,	568	You can also use them to simulate traditional event loops - for example,
334	you can block your main program until an event occurs - for example, you	569	you can block your main program until an event occurs - for example, you
335	could C<< ->wait >> in your main program until the user clicks the Quit	570	could C<< ->recv >> in your main program until the user clicks the Quit
336	button of your app, which would C<< ->send >> the "quit" event.	571	button of your app, which would C<< ->send >> the "quit" event.
337		572
338	Note that condition variables recurse into the event loop - if you have	573	Note that condition variables recurse into the event loop - if you have
339	two pieces of code that call C<< ->wait >> in a round-robbin fashion, you	574	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
340	lose. Therefore, condition variables are good to export to your caller, but	575	lose. Therefore, condition variables are good to export to your caller, but
341	you should avoid making a blocking wait yourself, at least in callbacks,	576	you should avoid making a blocking wait yourself, at least in callbacks,
342	as this asks for trouble.	577	as this asks for trouble.
343		578
344	Condition variables are represented by hash refs in perl, and the keys	579	Condition variables are represented by hash refs in perl, and the keys
…		…
349		584
350	There are two "sides" to a condition variable - the "producer side" which	585	There are two "sides" to a condition variable - the "producer side" which
351	eventually calls C<< -> send >>, and the "consumer side", which waits	586	eventually calls C<< -> send >>, and the "consumer side", which waits
352	for the send to occur.	587	for the send to occur.
353		588
354	Example:	589	Example: wait for a timer.
355		590
356	# wait till the result is ready	591	# wait till the result is ready
357	my $result_ready = AnyEvent->condvar;	592	my $result_ready = AnyEvent->condvar;
358		593
359	# do something such as adding a timer	594	# do something such as adding a timer
…		…
364	after => 1,	599	after => 1,
365	cb => sub { $result_ready->send },	600	cb => sub { $result_ready->send },
366	);	601	);
367		602
368	# this "blocks" (while handling events) till the callback	603	# this "blocks" (while handling events) till the callback
369	# calls send	604	# calls ->send
370	$result_ready->wait;	605	$result_ready->recv;
		606
		607	Example: wait for a timer, but take advantage of the fact that condition
		608	variables are also callable directly.
		609
		610	my $done = AnyEvent->condvar;
		611	my $delay = AnyEvent->timer (after => 5, cb => $done);
		612	$done->recv;
		613
		614	Example: Imagine an API that returns a condvar and doesn't support
		615	callbacks. This is how you make a synchronous call, for example from
		616	the main program:
		617
		618	use AnyEvent::CouchDB;
		619
		620	...
		621
		622	my @info = $couchdb->info->recv;
		623
		624	And this is how you would just set a callback to be called whenever the
		625	results are available:
		626
		627	$couchdb->info->cb (sub {
		628	my @info = $_[0]->recv;
		629	});
371		630
372	=head3 METHODS FOR PRODUCERS	631	=head3 METHODS FOR PRODUCERS
373		632
374	These methods should only be used by the producing side, i.e. the	633	These methods should only be used by the producing side, i.e. the
375	code/module that eventually sends the signal. Note that it is also	634	code/module that eventually sends the signal. Note that it is also
…		…
378		637
379	=over 4	638	=over 4
380		639
381	=item $cv->send (...)	640	=item $cv->send (...)
382		641
383	Flag the condition as ready - a running C<< ->wait >> and all further	642	Flag the condition as ready - a running C<< ->recv >> and all further
384	calls to C<wait> will (eventually) return after this method has been	643	calls to C<recv> will (eventually) return after this method has been
385	called. If nobody is waiting the send will be remembered.	644	called. If nobody is waiting the send will be remembered.
386		645
387	If a callback has been set on the condition variable, it is called	646	If a callback has been set on the condition variable, it is called
388	immediately from within send.	647	immediately from within send.
389		648
390	Any arguments passed to the C<send> call will be returned by all	649	Any arguments passed to the C<send> call will be returned by all
391	future C<< ->wait >> calls.	650	future C<< ->recv >> calls.
		651
		652	Condition variables are overloaded so one can call them directly (as if
		653	they were a code reference). Calling them directly is the same as calling
		654	C<send>.
392		655
393	=item $cv->croak ($error)	656	=item $cv->croak ($error)
394		657
395	Similar to send, but causes all call's wait C<< ->wait >> to invoke	658	Similar to send, but causes all call's to C<< ->recv >> to invoke
396	C<Carp::croak> with the given error message/object/scalar.	659	C<Carp::croak> with the given error message/object/scalar.
397		660
398	This can be used to signal any errors to the condition variable	661	This can be used to signal any errors to the condition variable
399	user/consumer.	662	user/consumer. Doing it this way instead of calling C<croak> directly
		663	delays the error detetcion, but has the overwhelmign advantage that it
		664	diagnoses the error at the place where the result is expected, and not
		665	deep in some event clalback without connection to the actual code causing
		666	the problem.
400		667
401	=item $cv->begin ([group callback])	668	=item $cv->begin ([group callback])
402		669
403	=item $cv->end	670	=item $cv->end
404		671
…		…
406	one. For example, a function that pings many hosts in parallel might want	673	one. For example, a function that pings many hosts in parallel might want
407	to use a condition variable for the whole process.	674	to use a condition variable for the whole process.
408		675
409	Every call to C<< ->begin >> will increment a counter, and every call to	676	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	677	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	678	>>, 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	679	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.	680	>>, but that is not required. If no group callback was set, C<send> will
		681	be called without any arguments.
414		682
415	Let's clarify this with the ping example:	683	You can think of C<< $cv->send >> giving you an OR condition (one call
		684	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		685	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		686
		687	Let's start with a simple example: you have two I/O watchers (for example,
		688	STDOUT and STDERR for a program), and you want to wait for both streams to
		689	close before activating a condvar:
416		690
417	my $cv = AnyEvent->condvar;	691	my $cv = AnyEvent->condvar;
418		692
		693	$cv->begin; # first watcher
		694	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		695	defined sysread $fh1, my $buf, 4096
		696	or $cv->end;
		697	});
		698
		699	$cv->begin; # second watcher
		700	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		701	defined sysread $fh2, my $buf, 4096
		702	or $cv->end;
		703	});
		704
		705	$cv->recv;
		706
		707	This works because for every event source (EOF on file handle), there is
		708	one call to C<begin>, so the condvar waits for all calls to C<end> before
		709	sending.
		710
		711	The ping example mentioned above is slightly more complicated, as the
		712	there are results to be passwd back, and the number of tasks that are
		713	begung can potentially be zero:
		714
		715	my $cv = AnyEvent->condvar;
		716
419	my %result;	717	my %result;
420	$cv->begin (sub { $cv->send (\%result) });	718	$cv->begin (sub { shift->send (\%result) });
421		719
422	for my $host (@list_of_hosts) {	720	for my $host (@list_of_hosts) {
423	$cv->begin;	721	$cv->begin;
424	ping_host_then_call_callback $host, sub {	722	ping_host_then_call_callback $host, sub {
425	$result{$host} = ...;	723	$result{$host} = ...;
…		…
440	loop, which serves two important purposes: first, it sets the callback	738	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	739	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	740	C<send> is called even when C<no> hosts are being pinged (the loop
443	doesn't execute once).	741	doesn't execute once).
444		742
445	This is the general pattern when you "fan out" into multiple subrequests:	743	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>	744	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	745	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>.	746	subrequest you start, call C<begin> and for each subrequest you finish,
		747	call C<end>.
449		748
450	=back	749	=back
451		750
452	=head3 METHODS FOR CONSUMERS	751	=head3 METHODS FOR CONSUMERS
453		752
454	These methods should only be used by the consuming side, i.e. the	753	These methods should only be used by the consuming side, i.e. the
455	code awaits the condition.	754	code awaits the condition.
456		755
457	=over 4	756	=over 4
458		757
459	=item $cv->wait	758	=item $cv->recv
460		759
461	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak	760	Wait (blocking if necessary) until the C<< ->send >> or C<< ->croak
462	>> methods have been called on c<$cv>, while servicing other watchers	761	>> methods have been called on c<$cv>, while servicing other watchers
463	normally.	762	normally.
464		763
…		…
469	function will call C<croak>.	768	function will call C<croak>.
470		769
471	In list context, all parameters passed to C<send> will be returned,	770	In list context, all parameters passed to C<send> will be returned,
472	in scalar context only the first one will be returned.	771	in scalar context only the first one will be returned.
473		772
		773	Note that doing a blocking wait in a callback is not supported by any
		774	event loop, that is, recursive invocation of a blocking C<< ->recv
		775	>> is not allowed, and the C<recv> call will C<croak> if such a
		776	condition is detected. This condition can be slightly loosened by using
		777	L<Coro::AnyEvent>, which allows you to do a blocking C<< ->recv >> from
		778	any thread that doesn't run the event loop itself.
		779
474	Not all event models support a blocking wait - some die in that case	780	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	781	(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	782	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	783	caller decide whether the call will block or not (for example, by coupling
478	condition variables with some kind of request results and supporting	784	condition variables with some kind of request results and supporting
479	callbacks so the caller knows that getting the result will not block,	785	callbacks so the caller knows that getting the result will not block,
480	while still suppporting blocking waits if the caller so desires).	786	while still supporting blocking waits if the caller so desires).
481		787
482	Another reason I<never> to C<< ->wait >> in a module is that you cannot
483	sensibly have two C<< ->wait >>'s in parallel, as that would require
484	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
485	can supply.
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<< ->wait >> calls perfectly safe as long as they are done from another
491	coroutine (one that doesn't run the event loop).
492
493	You can ensure that C<< -wait >> never blocks by setting a callback and	788	You can ensure that C<< -recv >> never blocks by setting a callback and
494	only calling C<< ->wait >> from within that callback (or at a later	789	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	790	time). This will work even when the event loop does not support blocking
496	waits otherwise.	791	waits otherwise.
497		792
498	=item $bool = $cv->ready	793	=item $bool = $cv->ready
499		794
500	Returns true when the condition is "true", i.e. whether C<send> or	795	Returns true when the condition is "true", i.e. whether C<send> or
501	C<croak> have been called.	796	C<croak> have been called.
502		797
503	=item $cb = $cv->cb ([new callback])	798	=item $cb = $cv->cb ($cb->($cv))
504		799
505	This is a mutator function that returns the callback set and optionally	800	This is a mutator function that returns the callback set and optionally
506	replaces it before doing so.	801	replaces it before doing so.
507		802
508	The callback will be called when the condition becomes "true", i.e. when	803	The callback will be called when the condition becomes (or already was)
509	C<send> or C<croak> are called. Calling C<wait> inside the callback	804	"true", i.e. when C<send> or C<croak> are called (or were called), with
		805	the only argument being the condition variable itself. Calling C<recv>
510	or at any later time is guaranteed not to block.	806	inside the callback or at any later time is guaranteed not to block.
511		807
512	=back	808	=back
513		809
		810	=head1 SUPPORTED EVENT LOOPS/BACKENDS
		811
		812	The available backend classes are (every class has its own manpage):
		813
		814	=over 4
		815
		816	=item Backends that are autoprobed when no other event loop can be found.
		817
		818	EV is the preferred backend when no other event loop seems to be in
		819	use. If EV is not installed, then AnyEvent will fall back to its own
		820	pure-perl implementation, which is available everywhere as it comes with
		821	AnyEvent itself.
		822
		823	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		824	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
		825
		826	=item Backends that are transparently being picked up when they are used.
		827
		828	These will be used when they are currently loaded when the first watcher
		829	is created, in which case it is assumed that the application is using
		830	them. This means that AnyEvent will automatically pick the right backend
		831	when the main program loads an event module before anything starts to
		832	create watchers. Nothing special needs to be done by the main program.
		833
		834	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		835	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		836	AnyEvent::Impl::Tk based on Tk, very broken.
		837	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		838	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		839	AnyEvent::Impl::Irssi used when running within irssi.
		840
		841	=item Backends with special needs.
		842
		843	Qt requires the Qt::Application to be instantiated first, but will
		844	otherwise be picked up automatically. As long as the main program
		845	instantiates the application before any AnyEvent watchers are created,
		846	everything should just work.
		847
		848	AnyEvent::Impl::Qt based on Qt.
		849
		850	Support for IO::Async can only be partial, as it is too broken and
		851	architecturally limited to even support the AnyEvent API. It also
		852	is the only event loop that needs the loop to be set explicitly, so
		853	it can only be used by a main program knowing about AnyEvent. See
		854	L<AnyEvent::Impl::Async> for the gory details.
		855
		856	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
		857
		858	=item Event loops that are indirectly supported via other backends.
		859
		860	Some event loops can be supported via other modules:
		861
		862	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		863
		864	B<WxWidgets> has no support for watching file handles. However, you can
		865	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		866	polls 20 times per second, which was considered to be too horrible to even
		867	consider for AnyEvent.
		868
		869	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		870	backend, so it can be supported through POE.
		871
		872	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		873	load L<POE> when detecting them, in the hope that POE will pick them up,
		874	in which case everything will be automatic.
		875
		876	=back
		877
514	=head1 GLOBAL VARIABLES AND FUNCTIONS	878	=head1 GLOBAL VARIABLES AND FUNCTIONS
515		879
		880	These are not normally required to use AnyEvent, but can be useful to
		881	write AnyEvent extension modules.
		882
516	=over 4	883	=over 4
517		884
518	=item $AnyEvent::MODEL	885	=item $AnyEvent::MODEL
519		886
520	Contains C<undef> until the first watcher is being created. Then it	887	Contains C<undef> until the first watcher is being created, before the
		888	backend has been autodetected.
		889
521	contains the event model that is being used, which is the name of the	890	Afterwards it contains the event model that is being used, which is the
522	Perl class implementing the model. This class is usually one of the	891	name of the Perl class implementing the model. This class is usually one
523	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	892	of the C<AnyEvent::Impl:xxx> modules, but can be any other class in the
524	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	893	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
525		894	will be C<urxvt::anyevent>).
526	The known classes so far are:
527
528	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
529	AnyEvent::Impl::Event based on Event, second best choice.
530	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
531	AnyEvent::Impl::Glib based on Glib, third-best choice.
532	AnyEvent::Impl::Tk based on Tk, very bad choice.
533	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
534	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
535	AnyEvent::Impl::POE based on POE, not generic enough for full support.
536
537	There is no support for WxWidgets, as WxWidgets has no support for
538	watching file handles. However, you can use WxWidgets through the
539	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
540	second, which was considered to be too horrible to even consider for
541	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
542	it's adaptor.
543
544	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
545	autodetecting them.
546		895
547	=item AnyEvent::detect	896	=item AnyEvent::detect
548		897
549	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	898	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
550	if necessary. You should only call this function right before you would	899	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	900	have created an AnyEvent watcher anyway, that is, as late as possible at
552	runtime.	901	runtime, and not e.g. while initialising of your module.
		902
		903	If you need to do some initialisation before AnyEvent watchers are
		904	created, use C<post_detect>.
553		905
554	=item $guard = AnyEvent::post_detect { BLOCK }	906	=item $guard = AnyEvent::post_detect { BLOCK }
555		907
556	Arranges for the code block to be executed as soon as the event model is	908	Arranges for the code block to be executed as soon as the event model is
557	autodetected (or immediately if this has already happened).	909	autodetected (or immediately if this has already happened).
558		910
		911	The block will be executed I<after> the actual backend has been detected
		912	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		913	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		914	other initialisations - see the sources of L<AnyEvent::Strict> or
		915	L<AnyEvent::AIO> to see how this is used.
		916
		917	The most common usage is to create some global watchers, without forcing
		918	event module detection too early, for example, L<AnyEvent::AIO> creates
		919	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		920	avoid autodetecting the event module at load time.
		921
559	If called in scalar or list context, then it creates and returns an object	922	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	923	that automatically removes the callback again when it is destroyed (or
		924	C<undef> when the hook was immediately executed). See L<AnyEvent::AIO> for
561	L<Coro::BDB> for a case where this is useful.	925	a case where this is useful.
		926
		927	Example: Create a watcher for the IO::AIO module and store it in
		928	C<$WATCHER>. Only do so after the event loop is initialised, though.
		929
		930	our WATCHER;
		931
		932	my $guard = AnyEvent::post_detect {
		933	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		934	};
		935
		936	# the ||= is important in case post_detect immediately runs the block,
		937	# as to not clobber the newly-created watcher. assigning both watcher and
		938	# post_detect guard to the same variable has the advantage of users being
		939	# able to just C<undef $WATCHER> if the watcher causes them grief.
		940
		941	$WATCHER ||= $guard;
562		942
563	=item @AnyEvent::post_detect	943	=item @AnyEvent::post_detect
564		944
565	If there are any code references in this array (you can C<push> to it	945	If there are any code references in this array (you can C<push> to it
566	before or after loading AnyEvent), then they will called directly after	946	before or after loading AnyEvent), then they will called directly after
567	the event loop has been chosen.	947	the event loop has been chosen.
568		948
569	You should check C<$AnyEvent::MODEL> before adding to this array, though:	949	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,	950	if it is defined then the event loop has already been detected, and the
571	and the array will be ignored.	951	array will be ignored.
572		952
573	Best use C<AnyEvent::post_detect { BLOCK }> instead.	953	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		954	it,as it takes care of these details.
		955
		956	This variable is mainly useful for modules that can do something useful
		957	when AnyEvent is used and thus want to know when it is initialised, but do
		958	not need to even load it by default. This array provides the means to hook
		959	into AnyEvent passively, without loading it.
574		960
575	=back	961	=back
576		962
577	=head1 WHAT TO DO IN A MODULE	963	=head1 WHAT TO DO IN A MODULE
578		964
…		…
582	Be careful when you create watchers in the module body - AnyEvent will	968	Be careful when you create watchers in the module body - AnyEvent will
583	decide which event module to use as soon as the first method is called, so	969	decide which event module to use as soon as the first method is called, so
584	by calling AnyEvent in your module body you force the user of your module	970	by calling AnyEvent in your module body you force the user of your module
585	to load the event module first.	971	to load the event module first.
586		972
587	Never call C<< ->wait >> on a condition variable unless you I<know> that	973	Never call C<< ->recv >> on a condition variable unless you I<know> that
588	the C<< ->send >> method has been called on it already. This is	974	the C<< ->send >> method has been called on it already. This is
589	because it will stall the whole program, and the whole point of using	975	because it will stall the whole program, and the whole point of using
590	events is to stay interactive.	976	events is to stay interactive.
591		977
592	It is fine, however, to call C<< ->wait >> when the user of your module	978	It is fine, however, to call C<< ->recv >> when the user of your module
593	requests it (i.e. if you create a http request object ad have a method	979	requests it (i.e. if you create a http request object ad have a method
594	called C<results> that returns the results, it should call C<< ->wait >>	980	called C<results> that returns the results, it should call C<< ->recv >>
595	freely, as the user of your module knows what she is doing. always).	981	freely, as the user of your module knows what she is doing. always).
596		982
597	=head1 WHAT TO DO IN THE MAIN PROGRAM	983	=head1 WHAT TO DO IN THE MAIN PROGRAM
598		984
599	There will always be a single main program - the only place that should	985	There will always be a single main program - the only place that should
…		…
601		987
602	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	988	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	989	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.	990	decide which implementation to chose if some module relies on it.
605		991
606	If the main program relies on a specific event model. For example, in	992	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	993	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	994	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	995	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	996	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	997	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.	998	might chose the wrong one unless you load the correct one yourself.
613		999
614	You can chose to use a rather inefficient pure-perl implementation by	1000	You can chose to use a pure-perl implementation by loading the
615	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	1001	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
616	behaviour everywhere, but letting AnyEvent chose is generally better.	1002	everywhere, but letting AnyEvent chose the model is generally better.
		1003
		1004	=head2 MAINLOOP EMULATION
		1005
		1006	Sometimes (often for short test scripts, or even standalone programs who
		1007	only want to use AnyEvent), you do not want to run a specific event loop.
		1008
		1009	In that case, you can use a condition variable like this:
		1010
		1011	AnyEvent->condvar->recv;
		1012
		1013	This has the effect of entering the event loop and looping forever.
		1014
		1015	Note that usually your program has some exit condition, in which case
		1016	it is better to use the "traditional" approach of storing a condition
		1017	variable somewhere, waiting for it, and sending it when the program should
		1018	exit cleanly.
		1019
617		1020
618	=head1 OTHER MODULES	1021	=head1 OTHER MODULES
619		1022
620	The following is a non-exhaustive list of additional modules that use	1023	The following is a non-exhaustive list of additional modules that use
621	AnyEvent and can therefore be mixed easily with other AnyEvent modules	1024	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	1025	modules and other event loops in the same program. Some of the modules
623	available via CPAN.	1026	come with AnyEvent, most are available via CPAN.
624		1027
625	=over 4	1028	=over 4
626		1029
627	=item L<AnyEvent::Util>	1030	=item L<AnyEvent::Util>
628		1031
629	Contains various utility functions that replace often-used but blocking	1032	Contains various utility functions that replace often-used but blocking
630	functions such as C<inet_aton> by event-/callback-based versions.	1033	functions such as C<inet_aton> by event-/callback-based versions.
631		1034
		1035	=item L<AnyEvent::Socket>
		1036
		1037	Provides various utility functions for (internet protocol) sockets,
		1038	addresses and name resolution. Also functions to create non-blocking tcp
		1039	connections or tcp servers, with IPv6 and SRV record support and more.
		1040
632	=item L<AnyEvent::Handle>	1041	=item L<AnyEvent::Handle>
633		1042
634	Provide read and write buffers and manages watchers for reads and writes.	1043	Provide read and write buffers, manages watchers for reads and writes,
		1044	supports raw and formatted I/O, I/O queued and fully transparent and
		1045	non-blocking SSL/TLS (via L<AnyEvent::TLS>.
		1046
		1047	=item L<AnyEvent::DNS>
		1048
		1049	Provides rich asynchronous DNS resolver capabilities.
		1050
		1051	=item L<AnyEvent::HTTP>
		1052
		1053	A simple-to-use HTTP library that is capable of making a lot of concurrent
		1054	HTTP requests.
635		1055
636	=item L<AnyEvent::HTTPD>	1056	=item L<AnyEvent::HTTPD>
637		1057
638	Provides a simple web application server framework.	1058	Provides a simple web application server framework.
639		1059
640	=item L<AnyEvent::DNS>
641
642	Provides asynchronous DNS resolver capabilities, beyond what
643	L<AnyEvent::Util> offers.
644
645	=item L<AnyEvent::FastPing>	1060	=item L<AnyEvent::FastPing>
646		1061
647	The fastest ping in the west.	1062	The fastest ping in the west.
648		1063
		1064	=item L<AnyEvent::DBI>
		1065
		1066	Executes L<DBI> requests asynchronously in a proxy process.
		1067
		1068	=item L<AnyEvent::AIO>
		1069
		1070	Truly asynchronous I/O, should be in the toolbox of every event
		1071	programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
		1072	together.
		1073
		1074	=item L<AnyEvent::BDB>
		1075
		1076	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
		1077	L<BDB> and AnyEvent together.
		1078
		1079	=item L<AnyEvent::GPSD>
		1080
		1081	A non-blocking interface to gpsd, a daemon delivering GPS information.
		1082
649	=item L<Net::IRC3>	1083	=item L<AnyEvent::IRC>
650		1084
651	AnyEvent based IRC client module family.	1085	AnyEvent based IRC client module family (replacing the older Net::IRC3).
652		1086
653	=item L<Net::XMPP2>	1087	=item L<AnyEvent::XMPP>
654		1088
655	AnyEvent based XMPP (Jabber protocol) module family.	1089	AnyEvent based XMPP (Jabber protocol) module family (replacing the older
		1090	Net::XMPP2>.
		1091
		1092	=item L<AnyEvent::IGS>
		1093
		1094	A non-blocking interface to the Internet Go Server protocol (used by
		1095	L<App::IGS>).
656		1096
657	=item L<Net::FCP>	1097	=item L<Net::FCP>
658		1098
659	AnyEvent-based implementation of the Freenet Client Protocol, birthplace	1099	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
660	of AnyEvent.	1100	of AnyEvent.
…		…
665		1105
666	=item L<Coro>	1106	=item L<Coro>
667		1107
668	Has special support for AnyEvent via L<Coro::AnyEvent>.	1108	Has special support for AnyEvent via L<Coro::AnyEvent>.
669		1109
670	=item L<AnyEvent::AIO>, L<IO::AIO>
671
672	Truly asynchronous I/O, should be in the toolbox of every event
673	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
674	together.
675
676	=item L<AnyEvent::BDB>, L<BDB>
677
678	Truly asynchronous Berkeley DB access. AnyEvent::AIO transparently fuses
679	IO::AIO and AnyEvent together.
680
681	=item L<IO::Lambda>
682
683	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
684
685	=back	1110	=back
686		1111
687	=cut	1112	=cut
688		1113
689	package AnyEvent;	1114	package AnyEvent;
690		1115
691	no warnings;	1116	# basically a tuned-down version of common::sense
692	use strict;	1117	sub common_sense {
		1118	# from common:.sense 1.0
		1119	${^WARNING_BITS} = "\xfc\x3f\xf3\x00\x0f\xf3\xcf\xc0\xf3\xfc\x33\x03";
		1120	# use strict vars subs
		1121	$^H |= 0x00000600;
		1122	}
693		1123
		1124	BEGIN { AnyEvent::common_sense }
		1125
694	use Carp;	1126	use Carp ();
695		1127
696	our $VERSION = '3.4';	1128	our $VERSION = '5.202';
697	our $MODEL;	1129	our $MODEL;
698		1130
699	our $AUTOLOAD;	1131	our $AUTOLOAD;
700	our @ISA;	1132	our @ISA;
701		1133
702	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
703
704	our @REGISTRY;	1134	our @REGISTRY;
705		1135
		1136	our $WIN32;
		1137
		1138	our $VERBOSE;
		1139
		1140	BEGIN {
		1141	eval "sub WIN32(){ " . (($^O =~ /mswin32/i)*1) ." }";
		1142	eval "sub TAINT(){ " . (${^TAINT}*1) . " }";
		1143
		1144	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1145	if ${^TAINT};
		1146
		1147	$VERBOSE = $ENV{PERL_ANYEVENT_VERBOSE}*1;
		1148
		1149	}
		1150
		1151	our $MAX_SIGNAL_LATENCY = 10;
		1152
		1153	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		1154
		1155	{
		1156	my $idx;
		1157	$PROTOCOL{$_} = ++$idx
		1158	for reverse split /\s*,\s*/,
		1159	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		1160	}
		1161
706	my @models = (	1162	my @models = (
707	[EV:: => AnyEvent::Impl::EV::],	1163	[EV:: => AnyEvent::Impl::EV:: , 1],
		1164	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl:: , 1],
		1165	# everything below here will not (normally) be autoprobed
		1166	# as the pureperl backend should work everywhere
		1167	# and is usually faster
708	[Event:: => AnyEvent::Impl::Event::],	1168	[Event:: => AnyEvent::Impl::Event::, 1],
		1169	[Glib:: => AnyEvent::Impl::Glib:: , 1], # becomes extremely slow with many watchers
		1170	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		1171	[Irssi:: => AnyEvent::Impl::Irssi::], # Irssi has a bogus "Event" package
709	[Tk:: => AnyEvent::Impl::Tk::],	1172	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		1173	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		1174	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
710	[Wx:: => AnyEvent::Impl::POE::],	1175	[Wx:: => AnyEvent::Impl::POE::],
711	[Prima:: => AnyEvent::Impl::POE::],	1176	[Prima:: => AnyEvent::Impl::POE::],
712	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1177	# IO::Async is just too broken - we would need workarounds for its
713	# everything below here will not be autoprobed as the pureperl backend should work everywhere	1178	# byzantine signal and broken child handling, among others.
714	[Glib:: => AnyEvent::Impl::Glib::],	1179	# IO::Async is rather hard to detect, as it doesn't have any
715	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy	1180	# obvious default class.
716	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program	1181	[IO::Async:: => AnyEvent::Impl::IOAsync::], # requires special main program
717	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza	1182	[IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1183	[IO::Async::Notifier:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1184	[AnyEvent::Impl::IOAsync:: => AnyEvent::Impl::IOAsync::], # requires special main program
718	);	1185	);
719		1186
720	our %method = map +($_ => 1), qw(io timer signal child condvar one_event DESTROY);	1187	our %method = map +($_ => 1),
		1188	qw(io timer time now now_update signal child idle condvar one_event DESTROY);
721		1189
722	our @post_detect;	1190	our @post_detect;
723		1191
724	sub post_detect(&) {	1192	sub post_detect(&) {
725	my ($cb) = @_;	1193	my ($cb) = @_;
726		1194
727	if ($MODEL) {	1195	if ($MODEL) {
728	$cb->();	1196	$cb->();
729		1197
730	1	1198	undef
731	} else {	1199	} else {
732	push @post_detect, $cb;	1200	push @post_detect, $cb;
733		1201
734	defined wantarray	1202	defined wantarray
735	? bless \$cb, "AnyEvent::Util::Guard"	1203	? bless \$cb, "AnyEvent::Util::postdetect"
736	: ()	1204	: ()
737	}	1205	}
738	}	1206	}
739		1207
740	sub AnyEvent::Util::Guard::DESTROY {	1208	sub AnyEvent::Util::postdetect::DESTROY {
741	@post_detect = grep $_ != ${$_[0]}, @post_detect;	1209	@post_detect = grep $_ != ${$_[0]}, @post_detect;
742	}	1210	}
743		1211
744	sub detect() {	1212	sub detect() {
745	unless ($MODEL) {	1213	unless ($MODEL) {
746	no strict 'refs';	1214	local $SIG{__DIE__};
747		1215
748	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	1216	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
749	my $model = "AnyEvent::Impl::$1";	1217	my $model = "AnyEvent::Impl::$1";
750	if (eval "require $model") {	1218	if (eval "require $model") {
751	$MODEL = $model;	1219	$MODEL = $model;
752	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	1220	warn "AnyEvent: loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.\n" if $VERBOSE >= 2;
753	} else {	1221	} else {
754	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;	1222	warn "AnyEvent: unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@" if $VERBOSE;
755	}	1223	}
756	}	1224	}
757		1225
758	# check for already loaded models	1226	# check for already loaded models
759	unless ($MODEL) {	1227	unless ($MODEL) {
760	for (@REGISTRY, @models) {	1228	for (@REGISTRY, @models) {
761	my ($package, $model) = @$_;	1229	my ($package, $model) = @$_;
762	if (${"$package\::VERSION"} > 0) {	1230	if (${"$package\::VERSION"} > 0) {
763	if (eval "require $model") {	1231	if (eval "require $model") {
764	$MODEL = $model;	1232	$MODEL = $model;
765	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;	1233	warn "AnyEvent: autodetected model '$model', using it.\n" if $VERBOSE >= 2;
766	last;	1234	last;
767	}	1235	}
768	}	1236	}
769	}	1237	}
770		1238
771	unless ($MODEL) {	1239	unless ($MODEL) {
772	# try to load a model	1240	# try to autoload a model
773
774	for (@REGISTRY, @models) {	1241	for (@REGISTRY, @models) {
775	my ($package, $model) = @$_;	1242	my ($package, $model, $autoload) = @$_;
		1243	if (
		1244	$autoload
776	if (eval "require $package"	1245	and eval "require $package"
777	and ${"$package\::VERSION"} > 0	1246	and ${"$package\::VERSION"} > 0
778	and eval "require $model") {	1247	and eval "require $model"
		1248	) {
779	$MODEL = $model;	1249	$MODEL = $model;
780	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;	1250	warn "AnyEvent: autoloaded model '$model', using it.\n" if $VERBOSE >= 2;
781	last;	1251	last;
782	}	1252	}
783	}	1253	}
784		1254
785	$MODEL	1255	$MODEL
786	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.";	1256	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.\n";
787	}	1257	}
788	}	1258	}
789		1259
		1260	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		1261
790	unshift @ISA, $MODEL;	1262	unshift @ISA, $MODEL;
791	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	1263
		1264	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
792		1265
793	(shift @post_detect)->() while @post_detect;	1266	(shift @post_detect)->() while @post_detect;
794	}	1267	}
795		1268
796	$MODEL	1269	$MODEL
…		…
798		1271
799	sub AUTOLOAD {	1272	sub AUTOLOAD {
800	(my $func = $AUTOLOAD) =~ s/.*://;	1273	(my $func = $AUTOLOAD) =~ s/.*://;
801		1274
802	$method{$func}	1275	$method{$func}
803	or croak "$func: not a valid method for AnyEvent objects";	1276	or Carp::croak "$func: not a valid method for AnyEvent objects";
804		1277
805	detect unless $MODEL;	1278	detect unless $MODEL;
806		1279
807	my $class = shift;	1280	my $class = shift;
808	$class->$func (@_);	1281	$class->$func (@_);
809	}	1282	}
810		1283
		1284	# utility function to dup a filehandle. this is used by many backends
		1285	# to support binding more than one watcher per filehandle (they usually
		1286	# allow only one watcher per fd, so we dup it to get a different one).
		1287	sub _dupfh($$;$$) {
		1288	my ($poll, $fh, $r, $w) = @_;
		1289
		1290	# cygwin requires the fh mode to be matching, unix doesn't
		1291	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1292
		1293	open my $fh2, $mode, $fh
		1294	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1295
		1296	# we assume CLOEXEC is already set by perl in all important cases
		1297
		1298	($fh2, $rw)
		1299	}
		1300
		1301	=head1 SIMPLIFIED AE API
		1302
		1303	Starting with version 5.0, AnyEvent officially supports a second, much
		1304	simpler, API that is designed to reduce the calling, typing and memory
		1305	overhead.
		1306
		1307	See the L<AE> manpage for details.
		1308
		1309	=cut
		1310
		1311	package AE;
		1312
		1313	our $VERSION = $AnyEvent::VERSION;
		1314
		1315	sub io($$$) {
		1316	AnyEvent->io (fh => $_[0], poll => $_[1] ? "w" : "r", cb => $_[2])
		1317	}
		1318
		1319	sub timer($$$) {
		1320	AnyEvent->timer (after => $_[0], interval => $_[1], cb => $_[2])
		1321	}
		1322
		1323	sub signal($$) {
		1324	AnyEvent->signal (signal => $_[0], cb => $_[1])
		1325	}
		1326
		1327	sub child($$) {
		1328	AnyEvent->child (pid => $_[0], cb => $_[1])
		1329	}
		1330
		1331	sub idle($) {
		1332	AnyEvent->idle (cb => $_[0])
		1333	}
		1334
		1335	sub cv(;&) {
		1336	AnyEvent->condvar (@_ ? (cb => $_[0]) : ())
		1337	}
		1338
		1339	sub now() {
		1340	AnyEvent->now
		1341	}
		1342
		1343	sub now_update() {
		1344	AnyEvent->now_update
		1345	}
		1346
		1347	sub time() {
		1348	AnyEvent->time
		1349	}
		1350
811	package AnyEvent::Base;	1351	package AnyEvent::Base;
812		1352
		1353	# default implementations for many methods
		1354
		1355	sub _time() {
		1356	# probe for availability of Time::HiRes
		1357	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1358	warn "AnyEvent: using Time::HiRes for sub-second timing accuracy.\n" if $VERBOSE >= 8;
		1359	*_time = \&Time::HiRes::time;
		1360	# if (eval "use POSIX (); (POSIX::times())...
		1361	} else {
		1362	warn "AnyEvent: using built-in time(), WARNING, no sub-second resolution!\n" if $VERBOSE;
		1363	*_time = sub { time }; # epic fail
		1364	}
		1365
		1366	&_time
		1367	}
		1368
		1369	sub time { _time }
		1370	sub now { _time }
		1371	sub now_update { }
		1372
813	# default implementation for ->condvar, ->wait, ->broadcast	1373	# default implementation for ->condvar
814		1374
815	sub condvar {	1375	sub condvar {
816	bless \my $flag, "AnyEvent::Base::CondVar"	1376	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
817	}
818
819	sub AnyEvent::Base::CondVar::broadcast {
820	${$_[0]}++;
821	}
822
823	sub AnyEvent::Base::CondVar::wait {
824	AnyEvent->one_event while !${$_[0]};
825	}	1377	}
826		1378
827	# default implementation for ->signal	1379	# default implementation for ->signal
828		1380
829	our %SIG_CB;	1381	our $HAVE_ASYNC_INTERRUPT;
		1382
		1383	sub _have_async_interrupt() {
		1384	$HAVE_ASYNC_INTERRUPT = 1*(!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT}
		1385	&& eval "use Async::Interrupt 1.02 (); 1")
		1386	unless defined $HAVE_ASYNC_INTERRUPT;
		1387
		1388	$HAVE_ASYNC_INTERRUPT
		1389	}
		1390
		1391	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1392	our (%SIG_ASY, %SIG_ASY_W);
		1393	our ($SIG_COUNT, $SIG_TW);
		1394
		1395	sub _signal_exec {
		1396	$HAVE_ASYNC_INTERRUPT
		1397	? $SIGPIPE_R->drain
		1398	: sysread $SIGPIPE_R, (my $dummy), 9;
		1399
		1400	while (%SIG_EV) {
		1401	for (keys %SIG_EV) {
		1402	delete $SIG_EV{$_};
		1403	$_->() for values %{ $SIG_CB{$_} || {} };
		1404	}
		1405	}
		1406	}
		1407
		1408	# install a dummy wakeup watcher to reduce signal catching latency
		1409	sub _sig_add() {
		1410	unless ($SIG_COUNT++) {
		1411	# try to align timer on a full-second boundary, if possible
		1412	my $NOW = AE::now;
		1413
		1414	$SIG_TW = AE::timer
		1415	$MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1416	$MAX_SIGNAL_LATENCY,
		1417	sub { } # just for the PERL_ASYNC_CHECK
		1418	;
		1419	}
		1420	}
		1421
		1422	sub _sig_del {
		1423	undef $SIG_TW
		1424	unless --$SIG_COUNT;
		1425	}
		1426
		1427	our $_sig_name_init; $_sig_name_init = sub {
		1428	eval q{ # poor man's autoloading
		1429	undef $_sig_name_init;
		1430
		1431	if (_have_async_interrupt) {
		1432	*sig2num = \&Async::Interrupt::sig2num;
		1433	*sig2name = \&Async::Interrupt::sig2name;
		1434	} else {
		1435	require Config;
		1436
		1437	my %signame2num;
		1438	@signame2num{ split ' ', $Config::Config{sig_name} }
		1439	= split ' ', $Config::Config{sig_num};
		1440
		1441	my @signum2name;
		1442	@signum2name[values %signame2num] = keys %signame2num;
		1443
		1444	*sig2num = sub($) {
		1445	$_[0] > 0 ? shift : $signame2num{+shift}
		1446	};
		1447	*sig2name = sub ($) {
		1448	$_[0] > 0 ? $signum2name[+shift] : shift
		1449	};
		1450	}
		1451	};
		1452	die if $@;
		1453	};
		1454
		1455	sub sig2num ($) { &$_sig_name_init; &sig2num }
		1456	sub sig2name($) { &$_sig_name_init; &sig2name }
830		1457
831	sub signal {	1458	sub signal {
		1459	eval q{ # poor man's autoloading {}
		1460	# probe for availability of Async::Interrupt
		1461	if (_have_async_interrupt) {
		1462	warn "AnyEvent: using Async::Interrupt for race-free signal handling.\n" if $VERBOSE >= 8;
		1463
		1464	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1465	$SIG_IO = AE::io $SIGPIPE_R->fileno, 0, \&_signal_exec;
		1466
		1467	} else {
		1468	warn "AnyEvent: using emulated perl signal handling with latency timer.\n" if $VERBOSE >= 8;
		1469
		1470	require Fcntl;
		1471
		1472	if (AnyEvent::WIN32) {
		1473	require AnyEvent::Util;
		1474
		1475	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1476	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R, 1) if $SIGPIPE_R;
		1477	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W, 1) if $SIGPIPE_W; # just in case
		1478	} else {
		1479	pipe $SIGPIPE_R, $SIGPIPE_W;
		1480	fcntl $SIGPIPE_R, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_R;
		1481	fcntl $SIGPIPE_W, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_W; # just in case
		1482
		1483	# not strictly required, as $^F is normally 2, but let's make sure...
		1484	fcntl $SIGPIPE_R, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1485	fcntl $SIGPIPE_W, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1486	}
		1487
		1488	$SIGPIPE_R
		1489	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1490
		1491	$SIG_IO = AE::io $SIGPIPE_R, 0, \&_signal_exec;
		1492	}
		1493
		1494	*signal = sub {
832	my (undef, %arg) = @_;	1495	my (undef, %arg) = @_;
833		1496
834	my $signal = uc $arg{signal}	1497	my $signal = uc $arg{signal}
835	or Carp::croak "required option 'signal' is missing";	1498	or Carp::croak "required option 'signal' is missing";
836		1499
		1500	if ($HAVE_ASYNC_INTERRUPT) {
		1501	# async::interrupt
		1502
		1503	$signal = sig2num $signal;
837	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1504	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1505
		1506	$SIG_ASY{$signal} ||= new Async::Interrupt
		1507	cb => sub { undef $SIG_EV{$signal} },
		1508	signal => $signal,
		1509	pipe => [$SIGPIPE_R->filenos],
		1510	pipe_autodrain => 0,
		1511	;
		1512
		1513	} else {
		1514	# pure perl
		1515
		1516	# AE::Util has been loaded in signal
		1517	$signal = sig2name $signal;
		1518	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1519
838	$SIG{$signal} ||= sub {	1520	$SIG{$signal} ||= sub {
839	$_->() for values %{ $SIG_CB{$signal} || {} };	1521	local $!;
		1522	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1523	undef $SIG_EV{$signal};
		1524	};
		1525
		1526	# can't do signal processing without introducing races in pure perl,
		1527	# so limit the signal latency.
		1528	_sig_add;
		1529	}
		1530
		1531	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
		1532	};
		1533
		1534	*AnyEvent::Base::signal::DESTROY = sub {
		1535	my ($signal, $cb) = @{$_[0]};
		1536
		1537	_sig_del;
		1538
		1539	delete $SIG_CB{$signal}{$cb};
		1540
		1541	$HAVE_ASYNC_INTERRUPT
		1542	? delete $SIG_ASY{$signal}
		1543	: # delete doesn't work with older perls - they then
		1544	# print weird messages, or just unconditionally exit
		1545	# instead of getting the default action.
		1546	undef $SIG{$signal}
		1547	unless keys %{ $SIG_CB{$signal} };
		1548	};
840	};	1549	};
841		1550	die if $@;
842	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1551	&signal
843	}
844
845	sub AnyEvent::Base::Signal::DESTROY {
846	my ($signal, $cb) = @{$_[0]};
847
848	delete $SIG_CB{$signal}{$cb};
849
850	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };
851	}	1552	}
852		1553
853	# default implementation for ->child	1554	# default implementation for ->child
854		1555
855	our %PID_CB;	1556	our %PID_CB;
856	our $CHLD_W;	1557	our $CHLD_W;
857	our $CHLD_DELAY_W;	1558	our $CHLD_DELAY_W;
858	our $PID_IDLE;
859	our $WNOHANG;	1559	our $WNOHANG;
860		1560
861	sub _child_wait {	1561	sub _emit_childstatus($$) {
862	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1562	my (undef, $rpid, $rstatus) = @_;
		1563
		1564	$_->($rpid, $rstatus)
863	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1565	for values %{ $PID_CB{$rpid} || {} },
864	(values %{ $PID_CB{0} || {} });	1566	values %{ $PID_CB{0} || {} };
865	}
866
867	undef $PID_IDLE;
868	}	1567	}
869		1568
870	sub _sigchld {	1569	sub _sigchld {
871	# make sure we deliver these changes "synchronous" with the event loop.	1570	my $pid;
872	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {	1571
873	undef $CHLD_DELAY_W;	1572	AnyEvent->_emit_childstatus ($pid, $?)
874	&_child_wait;	1573	while ($pid = waitpid -1, $WNOHANG) > 0;
875	});
876	}	1574	}
877		1575
878	sub child {	1576	sub child {
879	my (undef, %arg) = @_;	1577	my (undef, %arg) = @_;
880		1578
881	defined (my $pid = $arg{pid} + 0)	1579	defined (my $pid = $arg{pid} + 0)
882	or Carp::croak "required option 'pid' is missing";	1580	or Carp::croak "required option 'pid' is missing";
883		1581
884	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1582	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
885		1583
886	unless ($WNOHANG) {	1584	# WNOHANG is almost cetrainly 1 everywhere
887	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;	1585	$WNOHANG ||= $^O =~ /^(?:openbsd|netbsd|linux|freebsd|cygwin|MSWin32)$/
888	}	1586	? 1
		1587	: eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
889		1588
890	unless ($CHLD_W) {	1589	unless ($CHLD_W) {
891	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1590	$CHLD_W = AE::signal CHLD => \&_sigchld;
892	# child could be a zombie already, so make at least one round	1591	# child could be a zombie already, so make at least one round
893	&_sigchld;	1592	&_sigchld;
894	}	1593	}
895		1594
896	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	1595	bless [$pid, $arg{cb}], "AnyEvent::Base::child"
897	}	1596	}
898		1597
899	sub AnyEvent::Base::Child::DESTROY {	1598	sub AnyEvent::Base::child::DESTROY {
900	my ($pid, $cb) = @{$_[0]};	1599	my ($pid, $cb) = @{$_[0]};
901		1600
902	delete $PID_CB{$pid}{$cb};	1601	delete $PID_CB{$pid}{$cb};
903	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1602	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
904		1603
905	undef $CHLD_W unless keys %PID_CB;	1604	undef $CHLD_W unless keys %PID_CB;
906	}	1605	}
		1606
		1607	# idle emulation is done by simply using a timer, regardless
		1608	# of whether the process is idle or not, and not letting
		1609	# the callback use more than 50% of the time.
		1610	sub idle {
		1611	my (undef, %arg) = @_;
		1612
		1613	my ($cb, $w, $rcb) = $arg{cb};
		1614
		1615	$rcb = sub {
		1616	if ($cb) {
		1617	$w = _time;
		1618	&$cb;
		1619	$w = _time - $w;
		1620
		1621	# never use more then 50% of the time for the idle watcher,
		1622	# within some limits
		1623	$w = 0.0001 if $w < 0.0001;
		1624	$w = 5 if $w > 5;
		1625
		1626	$w = AE::timer $w, 0, $rcb;
		1627	} else {
		1628	# clean up...
		1629	undef $w;
		1630	undef $rcb;
		1631	}
		1632	};
		1633
		1634	$w = AE::timer 0.05, 0, $rcb;
		1635
		1636	bless \\$cb, "AnyEvent::Base::idle"
		1637	}
		1638
		1639	sub AnyEvent::Base::idle::DESTROY {
		1640	undef $${$_[0]};
		1641	}
		1642
		1643	package AnyEvent::CondVar;
		1644
		1645	our @ISA = AnyEvent::CondVar::Base::;
		1646
		1647	package AnyEvent::CondVar::Base;
		1648
		1649	#use overload
		1650	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1651	# fallback => 1;
		1652
		1653	# save 300+ kilobytes by dirtily hardcoding overloading
		1654	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1655	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1656	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1657	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1658
		1659	our $WAITING;
		1660
		1661	sub _send {
		1662	# nop
		1663	}
		1664
		1665	sub send {
		1666	my $cv = shift;
		1667	$cv->{_ae_sent} = [@_];
		1668	(delete $cv->{_ae_cb})->($cv) if $cv->{_ae_cb};
		1669	$cv->_send;
		1670	}
		1671
		1672	sub croak {
		1673	$_[0]{_ae_croak} = $_[1];
		1674	$_[0]->send;
		1675	}
		1676
		1677	sub ready {
		1678	$_[0]{_ae_sent}
		1679	}
		1680
		1681	sub _wait {
		1682	$WAITING
		1683	and !$_[0]{_ae_sent}
		1684	and Carp::croak "AnyEvent::CondVar: recursive blocking wait detected";
		1685
		1686	local $WAITING = 1;
		1687	AnyEvent->one_event while !$_[0]{_ae_sent};
		1688	}
		1689
		1690	sub recv {
		1691	$_[0]->_wait;
		1692
		1693	Carp::croak $_[0]{_ae_croak} if $_[0]{_ae_croak};
		1694	wantarray ? @{ $_[0]{_ae_sent} } : $_[0]{_ae_sent}[0]
		1695	}
		1696
		1697	sub cb {
		1698	my $cv = shift;
		1699
		1700	@_
		1701	and $cv->{_ae_cb} = shift
		1702	and $cv->{_ae_sent}
		1703	and (delete $cv->{_ae_cb})->($cv);
		1704
		1705	$cv->{_ae_cb}
		1706	}
		1707
		1708	sub begin {
		1709	++$_[0]{_ae_counter};
		1710	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
		1711	}
		1712
		1713	sub end {
		1714	return if --$_[0]{_ae_counter};
		1715	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
		1716	}
		1717
		1718	# undocumented/compatibility with pre-3.4
		1719	*broadcast = \&send;
		1720	*wait = \&_wait;
		1721
		1722	=head1 ERROR AND EXCEPTION HANDLING
		1723
		1724	In general, AnyEvent does not do any error handling - it relies on the
		1725	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1726	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1727	checking of all AnyEvent methods, however, which is highly useful during
		1728	development.
		1729
		1730	As for exception handling (i.e. runtime errors and exceptions thrown while
		1731	executing a callback), this is not only highly event-loop specific, but
		1732	also not in any way wrapped by this module, as this is the job of the main
		1733	program.
		1734
		1735	The pure perl event loop simply re-throws the exception (usually
		1736	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1737	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1738	so on.
		1739
		1740	=head1 ENVIRONMENT VARIABLES
		1741
		1742	The following environment variables are used by this module or its
		1743	submodules.
		1744
		1745	Note that AnyEvent will remove I<all> environment variables starting with
		1746	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		1747	enabled.
		1748
		1749	=over 4
		1750
		1751	=item C<PERL_ANYEVENT_VERBOSE>
		1752
		1753	By default, AnyEvent will be completely silent except in fatal
		1754	conditions. You can set this environment variable to make AnyEvent more
		1755	talkative.
		1756
		1757	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1758	conditions, such as not being able to load the event model specified by
		1759	C<PERL_ANYEVENT_MODEL>.
		1760
		1761	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1762	model it chooses.
		1763
		1764	When set to C<8> or higher, then AnyEvent will report extra information on
		1765	which optional modules it loads and how it implements certain features.
		1766
		1767	=item C<PERL_ANYEVENT_STRICT>
		1768
		1769	AnyEvent does not do much argument checking by default, as thorough
		1770	argument checking is very costly. Setting this variable to a true value
		1771	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1772	check the arguments passed to most method calls. If it finds any problems,
		1773	it will croak.
		1774
		1775	In other words, enables "strict" mode.
		1776
		1777	Unlike C<use strict> (or it's modern cousin, C<< use L<common::sense>
		1778	>>, it is definitely recommended to keep it off in production. Keeping
		1779	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		1780	can be very useful, however.
		1781
		1782	=item C<PERL_ANYEVENT_MODEL>
		1783
		1784	This can be used to specify the event model to be used by AnyEvent, before
		1785	auto detection and -probing kicks in. It must be a string consisting
		1786	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1787	and the resulting module name is loaded and if the load was successful,
		1788	used as event model. If it fails to load AnyEvent will proceed with
		1789	auto detection and -probing.
		1790
		1791	This functionality might change in future versions.
		1792
		1793	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1794	could start your program like this:
		1795
		1796	PERL_ANYEVENT_MODEL=Perl perl ...
		1797
		1798	=item C<PERL_ANYEVENT_PROTOCOLS>
		1799
		1800	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1801	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1802	of auto probing).
		1803
		1804	Must be set to a comma-separated list of protocols or address families,
		1805	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1806	used, and preference will be given to protocols mentioned earlier in the
		1807	list.
		1808
		1809	This variable can effectively be used for denial-of-service attacks
		1810	against local programs (e.g. when setuid), although the impact is likely
		1811	small, as the program has to handle conenction and other failures anyways.
		1812
		1813	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1814	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1815	- only support IPv4, never try to resolve or contact IPv6
		1816	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1817	IPv6, but prefer IPv6 over IPv4.
		1818
		1819	=item C<PERL_ANYEVENT_EDNS0>
		1820
		1821	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1822	for DNS. This extension is generally useful to reduce DNS traffic, but
		1823	some (broken) firewalls drop such DNS packets, which is why it is off by
		1824	default.
		1825
		1826	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1827	EDNS0 in its DNS requests.
		1828
		1829	=item C<PERL_ANYEVENT_MAX_FORKS>
		1830
		1831	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1832	will create in parallel.
		1833
		1834	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		1835
		1836	The default value for the C<max_outstanding> parameter for the default DNS
		1837	resolver - this is the maximum number of parallel DNS requests that are
		1838	sent to the DNS server.
		1839
		1840	=item C<PERL_ANYEVENT_RESOLV_CONF>
		1841
		1842	The file to use instead of F</etc/resolv.conf> (or OS-specific
		1843	configuration) in the default resolver. When set to the empty string, no
		1844	default config will be used.
		1845
		1846	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		1847
		1848	When neither C<ca_file> nor C<ca_path> was specified during
		1849	L<AnyEvent::TLS> context creation, and either of these environment
		1850	variables exist, they will be used to specify CA certificate locations
		1851	instead of a system-dependent default.
		1852
		1853	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		1854
		1855	When these are set to C<1>, then the respective modules are not
		1856	loaded. Mostly good for testing AnyEvent itself.
		1857
		1858	=back
907		1859
908	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1860	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
909		1861
910	This is an advanced topic that you do not normally need to use AnyEvent in	1862	This is an advanced topic that you do not normally need to use AnyEvent in
911	a module. This section is only of use to event loop authors who want to	1863	a module. This section is only of use to event loop authors who want to
…		…
945		1897
946	I<rxvt-unicode> also cheats a bit by not providing blocking access to	1898	I<rxvt-unicode> also cheats a bit by not providing blocking access to
947	condition variables: code blocking while waiting for a condition will	1899	condition variables: code blocking while waiting for a condition will
948	C<die>. This still works with most modules/usages, and blocking calls must	1900	C<die>. This still works with most modules/usages, and blocking calls must
949	not be done in an interactive application, so it makes sense.	1901	not be done in an interactive application, so it makes sense.
950
951	=head1 ENVIRONMENT VARIABLES
952
953	The following environment variables are used by this module:
954
955	=over 4
956
957	=item C<PERL_ANYEVENT_VERBOSE>
958
959	By default, AnyEvent will be completely silent except in fatal
960	conditions. You can set this environment variable to make AnyEvent more
961	talkative.
962
963	When set to C<1> or higher, causes AnyEvent to warn about unexpected
964	conditions, such as not being able to load the event model specified by
965	C<PERL_ANYEVENT_MODEL>.
966
967	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
968	model it chooses.
969
970	=item C<PERL_ANYEVENT_MODEL>
971
972	This can be used to specify the event model to be used by AnyEvent, before
973	autodetection and -probing kicks in. It must be a string consisting
974	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
975	and the resulting module name is loaded and if the load was successful,
976	used as event model. If it fails to load AnyEvent will proceed with
977	autodetection and -probing.
978
979	This functionality might change in future versions.
980
981	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
982	could start your program like this:
983
984	PERL_ANYEVENT_MODEL=Perl perl ...
985
986	=back
987		1902
988	=head1 EXAMPLE PROGRAM	1903	=head1 EXAMPLE PROGRAM
989		1904
990	The following program uses an I/O watcher to read data from STDIN, a timer	1905	The following program uses an I/O watcher to read data from STDIN, a timer
991	to display a message once per second, and a condition variable to quit the	1906	to display a message once per second, and a condition variable to quit the
…		…
1000	poll => 'r',	1915	poll => 'r',
1001	cb => sub {	1916	cb => sub {
1002	warn "io event <$_[0]>\n"; # will always output <r>	1917	warn "io event <$_[0]>\n"; # will always output <r>
1003	chomp (my $input = <STDIN>); # read a line	1918	chomp (my $input = <STDIN>); # read a line
1004	warn "read: $input\n"; # output what has been read	1919	warn "read: $input\n"; # output what has been read
1005	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	1920	$cv->send if $input =~ /^q/i; # quit program if /^q/i
1006	},	1921	},
1007	);	1922	);
1008		1923
1009	my $time_watcher; # can only be used once
1010
1011	sub new_timer {
1012	$timer = AnyEvent->timer (after => 1, cb => sub {	1924	my $time_watcher = AnyEvent->timer (after => 1, interval => 1, cb => sub {
1013	warn "timeout\n"; # print 'timeout' about every second	1925	warn "timeout\n"; # print 'timeout' at most every second
1014	&new_timer; # and restart the time
1015	});	1926	});
1016	}
1017		1927
1018	new_timer; # create first timer
1019
1020	$cv->wait; # wait until user enters /^q/i	1928	$cv->recv; # wait until user enters /^q/i
1021		1929
1022	=head1 REAL-WORLD EXAMPLE	1930	=head1 REAL-WORLD EXAMPLE
1023		1931
1024	Consider the L<Net::FCP> module. It features (among others) the following	1932	Consider the L<Net::FCP> module. It features (among others) the following
1025	API calls, which are to freenet what HTTP GET requests are to http:	1933	API calls, which are to freenet what HTTP GET requests are to http:
…		…
1075	syswrite $txn->{fh}, $txn->{request}	1983	syswrite $txn->{fh}, $txn->{request}
1076	or die "connection or write error";	1984	or die "connection or write error";
1077	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	1985	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
1078		1986
1079	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	1987	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
1080	result and signals any possible waiters that the request ahs finished:	1988	result and signals any possible waiters that the request has finished:
1081		1989
1082	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	1990	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
1083		1991
1084	if (end-of-file or data complete) {	1992	if (end-of-file or data complete) {
1085	$txn->{result} = $txn->{buf};	1993	$txn->{result} = $txn->{buf};
1086	$txn->{finished}->broadcast;	1994	$txn->{finished}->send;
1087	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	1995	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
1088	}	1996	}
1089		1997
1090	The C<result> method, finally, just waits for the finished signal (if the	1998	The C<result> method, finally, just waits for the finished signal (if the
1091	request was already finished, it doesn't wait, of course, and returns the	1999	request was already finished, it doesn't wait, of course, and returns the
1092	data:	2000	data:
1093		2001
1094	$txn->{finished}->wait;	2002	$txn->{finished}->recv;
1095	return $txn->{result};	2003	return $txn->{result};
1096		2004
1097	The actual code goes further and collects all errors (C<die>s, exceptions)	2005	The actual code goes further and collects all errors (C<die>s, exceptions)
1098	that occured during request processing. The C<result> method detects	2006	that occurred during request processing. The C<result> method detects
1099	whether an exception as thrown (it is stored inside the $txn object)	2007	whether an exception as thrown (it is stored inside the $txn object)
1100	and just throws the exception, which means connection errors and other	2008	and just throws the exception, which means connection errors and other
1101	problems get reported tot he code that tries to use the result, not in a	2009	problems get reported tot he code that tries to use the result, not in a
1102	random callback.	2010	random callback.
1103		2011
…		…
1134		2042
1135	my $quit = AnyEvent->condvar;	2043	my $quit = AnyEvent->condvar;
1136		2044
1137	$fcp->txn_client_get ($url)->cb (sub {	2045	$fcp->txn_client_get ($url)->cb (sub {
1138	...	2046	...
1139	$quit->broadcast;	2047	$quit->send;
1140	});	2048	});
1141		2049
1142	$quit->wait;	2050	$quit->recv;
1143		2051
1144		2052
1145	=head1 BENCHMARKS	2053	=head1 BENCHMARKS
1146		2054
1147	To give you an idea of the performance and overheads that AnyEvent adds	2055	To give you an idea of the performance and overheads that AnyEvent adds
…		…
1149	of various event loops I prepared some benchmarks.	2057	of various event loops I prepared some benchmarks.
1150		2058
1151	=head2 BENCHMARKING ANYEVENT OVERHEAD	2059	=head2 BENCHMARKING ANYEVENT OVERHEAD
1152		2060
1153	Here is a benchmark of various supported event models used natively and	2061	Here is a benchmark of various supported event models used natively and
1154	through anyevent. The benchmark creates a lot of timers (with a zero	2062	through AnyEvent. The benchmark creates a lot of timers (with a zero
1155	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,	2063	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
1156	which it is), lets them fire exactly once and destroys them again.	2064	which it is), lets them fire exactly once and destroys them again.
1157		2065
1158	Source code for this benchmark is found as F<eg/bench> in the AnyEvent	2066	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
1159	distribution.	2067	distribution. It uses the L<AE> interface, which makes a real difference
		2068	for the EV and Perl backends only.
1160		2069
1161	=head3 Explanation of the columns	2070	=head3 Explanation of the columns
1162		2071
1163	I<watcher> is the number of event watchers created/destroyed. Since	2072	I<watcher> is the number of event watchers created/destroyed. Since
1164	different event models feature vastly different performances, each event	2073	different event models feature vastly different performances, each event
…		…
1176	all watchers, to avoid adding memory overhead. That means closure creation	2085	all watchers, to avoid adding memory overhead. That means closure creation
1177	and memory usage is not included in the figures.	2086	and memory usage is not included in the figures.
1178		2087
1179	I<invoke> is the time, in microseconds, used to invoke a simple	2088	I<invoke> is the time, in microseconds, used to invoke a simple
1180	callback. The callback simply counts down a Perl variable and after it was	2089	callback. The callback simply counts down a Perl variable and after it was
1181	invoked "watcher" times, it would C<< ->broadcast >> a condvar once to	2090	invoked "watcher" times, it would C<< ->send >> a condvar once to
1182	signal the end of this phase.	2091	signal the end of this phase.
1183		2092
1184	I<destroy> is the time, in microseconds, that it takes to destroy a single	2093	I<destroy> is the time, in microseconds, that it takes to destroy a single
1185	watcher.	2094	watcher.
1186		2095
1187	=head3 Results	2096	=head3 Results
1188		2097
1189	name watchers bytes create invoke destroy comment	2098	name watchers bytes create invoke destroy comment
1190	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	2099	EV/EV 100000 223 0.47 0.43 0.27 EV native interface
1191	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	2100	EV/Any 100000 223 0.48 0.42 0.26 EV + AnyEvent watchers
1192	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	2101	Coro::EV/Any 100000 223 0.47 0.42 0.26 coroutines + Coro::Signal
1193	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	2102	Perl/Any 100000 431 2.70 0.74 0.92 pure perl implementation
1194	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	2103	Event/Event 16000 516 31.16 31.84 0.82 Event native interface
1195	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers	2104	Event/Any 16000 1203 42.61 34.79 1.80 Event + AnyEvent watchers
		2105	IOAsync/Any 16000 1911 41.92 27.45 16.81 via IO::Async::Loop::IO_Poll
		2106	IOAsync/Any 16000 1726 40.69 26.37 15.25 via IO::Async::Loop::Epoll
1196	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	2107	Glib/Any 16000 1118 89.00 12.57 51.17 quadratic behaviour
1197	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	2108	Tk/Any 2000 1346 20.96 10.75 8.00 SEGV with >> 2000 watchers
1198	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	2109	POE/Any 2000 6951 108.97 795.32 14.24 via POE::Loop::Event
1199	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	2110	POE/Any 2000 6648 94.79 774.40 575.51 via POE::Loop::Select
1200		2111
1201	=head3 Discussion	2112	=head3 Discussion
1202		2113
1203	The benchmark does I<not> measure scalability of the event loop very	2114	The benchmark does I<not> measure scalability of the event loop very
1204	well. For example, a select-based event loop (such as the pure perl one)	2115	well. For example, a select-based event loop (such as the pure perl one)
…		…
1216	benchmark machine, handling an event takes roughly 1600 CPU cycles with	2127	benchmark machine, handling an event takes roughly 1600 CPU cycles with
1217	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU	2128	EV, 3100 CPU cycles with AnyEvent's pure perl loop and almost 3000000 CPU
1218	cycles with POE.	2129	cycles with POE.
1219		2130
1220	C<EV> is the sole leader regarding speed and memory use, which are both	2131	C<EV> is the sole leader regarding speed and memory use, which are both
1221	maximal/minimal, respectively. Even when going through AnyEvent, it uses	2132	maximal/minimal, respectively. When using the L<AE> API there is zero
		2133	overhead (when going through the AnyEvent API create is about 5-6 times
		2134	slower, with other times being equal, so still uses far less memory than
1222	far less memory than any other event loop and is still faster than Event	2135	any other event loop and is still faster than Event natively).
1223	natively.
1224		2136
1225	The pure perl implementation is hit in a few sweet spots (both the	2137	The pure perl implementation is hit in a few sweet spots (both the
1226	constant timeout and the use of a single fd hit optimisations in the perl	2138	constant timeout and the use of a single fd hit optimisations in the perl
1227	interpreter and the backend itself). Nevertheless this shows that it	2139	interpreter and the backend itself). Nevertheless this shows that it
1228	adds very little overhead in itself. Like any select-based backend its	2140	adds very little overhead in itself. Like any select-based backend its
1229	performance becomes really bad with lots of file descriptors (and few of	2141	performance becomes really bad with lots of file descriptors (and few of
1230	them active), of course, but this was not subject of this benchmark.	2142	them active), of course, but this was not subject of this benchmark.
1231		2143
1232	The C<Event> module has a relatively high setup and callback invocation	2144	The C<Event> module has a relatively high setup and callback invocation
1233	cost, but overall scores in on the third place.	2145	cost, but overall scores in on the third place.
		2146
		2147	C<IO::Async> performs admirably well, about on par with C<Event>, even
		2148	when using its pure perl backend.
1234		2149
1235	C<Glib>'s memory usage is quite a bit higher, but it features a	2150	C<Glib>'s memory usage is quite a bit higher, but it features a
1236	faster callback invocation and overall ends up in the same class as	2151	faster callback invocation and overall ends up in the same class as
1237	C<Event>. However, Glib scales extremely badly, doubling the number of	2152	C<Event>. However, Glib scales extremely badly, doubling the number of
1238	watchers increases the processing time by more than a factor of four,	2153	watchers increases the processing time by more than a factor of four,
…		…
1282		2197
1283	=back	2198	=back
1284		2199
1285	=head2 BENCHMARKING THE LARGE SERVER CASE	2200	=head2 BENCHMARKING THE LARGE SERVER CASE
1286		2201
1287	This benchmark atcually benchmarks the event loop itself. It works by	2202	This benchmark actually benchmarks the event loop itself. It works by
1288	creating a number of "servers": each server consists of a socketpair, a	2203	creating a number of "servers": each server consists of a socket pair, a
1289	timeout watcher that gets reset on activity (but never fires), and an I/O	2204	timeout watcher that gets reset on activity (but never fires), and an I/O
1290	watcher waiting for input on one side of the socket. Each time the socket	2205	watcher waiting for input on one side of the socket. Each time the socket
1291	watcher reads a byte it will write that byte to a random other "server".	2206	watcher reads a byte it will write that byte to a random other "server".
1292		2207
1293	The effect is that there will be a lot of I/O watchers, only part of which	2208	The effect is that there will be a lot of I/O watchers, only part of which
1294	are active at any one point (so there is a constant number of active	2209	are active at any one point (so there is a constant number of active
1295	fds for each loop iterstaion, but which fds these are is random). The	2210	fds for each loop iteration, but which fds these are is random). The
1296	timeout is reset each time something is read because that reflects how	2211	timeout is reset each time something is read because that reflects how
1297	most timeouts work (and puts extra pressure on the event loops).	2212	most timeouts work (and puts extra pressure on the event loops).
1298		2213
1299	In this benchmark, we use 10000 socketpairs (20000 sockets), of which 100	2214	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
1300	(1%) are active. This mirrors the activity of large servers with many	2215	(1%) are active. This mirrors the activity of large servers with many
1301	connections, most of which are idle at any one point in time.	2216	connections, most of which are idle at any one point in time.
1302		2217
1303	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent	2218	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
1304	distribution.	2219	distribution. It uses the L<AE> interface, which makes a real difference
		2220	for the EV and Perl backends only.
1305		2221
1306	=head3 Explanation of the columns	2222	=head3 Explanation of the columns
1307		2223
1308	I<sockets> is the number of sockets, and twice the number of "servers" (as	2224	I<sockets> is the number of sockets, and twice the number of "servers" (as
1309	each server has a read and write socket end).	2225	each server has a read and write socket end).
1310		2226
1311	I<create> is the time it takes to create a socketpair (which is	2227	I<create> is the time it takes to create a socket pair (which is
1312	nontrivial) and two watchers: an I/O watcher and a timeout watcher.	2228	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
1313		2229
1314	I<request>, the most important value, is the time it takes to handle a	2230	I<request>, the most important value, is the time it takes to handle a
1315	single "request", that is, reading the token from the pipe and forwarding	2231	single "request", that is, reading the token from the pipe and forwarding
1316	it to another server. This includes deleting the old timeout and creating	2232	it to another server. This includes deleting the old timeout and creating
1317	a new one that moves the timeout into the future.	2233	a new one that moves the timeout into the future.
1318		2234
1319	=head3 Results	2235	=head3 Results
1320		2236
1321	name sockets create request	2237	name sockets create request
1322	EV 20000 69.01 11.16	2238	EV 20000 62.66 7.99
1323	Perl 20000 73.32 35.87	2239	Perl 20000 68.32 32.64
1324	Event 20000 212.62 257.32	2240	IOAsync 20000 174.06 101.15 epoll
1325	Glib 20000 651.16 1896.30	2241	IOAsync 20000 174.67 610.84 poll
		2242	Event 20000 202.69 242.91
		2243	Glib 20000 557.01 1689.52
1326	POE 20000 349.67 12317.24 uses POE::Loop::Event	2244	POE 20000 341.54 12086.32 uses POE::Loop::Event
1327		2245
1328	=head3 Discussion	2246	=head3 Discussion
1329		2247
1330	This benchmark I<does> measure scalability and overall performance of the	2248	This benchmark I<does> measure scalability and overall performance of the
1331	particular event loop.	2249	particular event loop.
…		…
1333	EV is again fastest. Since it is using epoll on my system, the setup time	2251	EV is again fastest. Since it is using epoll on my system, the setup time
1334	is relatively high, though.	2252	is relatively high, though.
1335		2253
1336	Perl surprisingly comes second. It is much faster than the C-based event	2254	Perl surprisingly comes second. It is much faster than the C-based event
1337	loops Event and Glib.	2255	loops Event and Glib.
		2256
		2257	IO::Async performs very well when using its epoll backend, and still quite
		2258	good compared to Glib when using its pure perl backend.
1338		2259
1339	Event suffers from high setup time as well (look at its code and you will	2260	Event suffers from high setup time as well (look at its code and you will
1340	understand why). Callback invocation also has a high overhead compared to	2261	understand why). Callback invocation also has a high overhead compared to
1341	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event	2262	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
1342	uses select or poll in basically all documented configurations.	2263	uses select or poll in basically all documented configurations.
…		…
1389	speed most when you have lots of watchers, not when you only have a few of	2310	speed most when you have lots of watchers, not when you only have a few of
1390	them).	2311	them).
1391		2312
1392	EV is again fastest.	2313	EV is again fastest.
1393		2314
1394	Perl again comes second. It is noticably faster than the C-based event	2315	Perl again comes second. It is noticeably faster than the C-based event
1395	loops Event and Glib, although the difference is too small to really	2316	loops Event and Glib, although the difference is too small to really
1396	matter.	2317	matter.
1397		2318
1398	POE also performs much better in this case, but is is still far behind the	2319	POE also performs much better in this case, but is is still far behind the
1399	others.	2320	others.
…		…
1402		2323
1403	=over 4	2324	=over 4
1404		2325
1405	=item * C-based event loops perform very well with small number of	2326	=item * C-based event loops perform very well with small number of
1406	watchers, as the management overhead dominates.	2327	watchers, as the management overhead dominates.
		2328
		2329	=back
		2330
		2331	=head2 THE IO::Lambda BENCHMARK
		2332
		2333	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2334	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2335	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2336	shouldn't come as a surprise to anybody). As such, the benchmark is
		2337	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2338	very optimal. But how would AnyEvent compare when used without the extra
		2339	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2340
		2341	The benchmark itself creates an echo-server, and then, for 500 times,
		2342	connects to the echo server, sends a line, waits for the reply, and then
		2343	creates the next connection. This is a rather bad benchmark, as it doesn't
		2344	test the efficiency of the framework or much non-blocking I/O, but it is a
		2345	benchmark nevertheless.
		2346
		2347	name runtime
		2348	Lambda/select 0.330 sec
		2349	+ optimized 0.122 sec
		2350	Lambda/AnyEvent 0.327 sec
		2351	+ optimized 0.138 sec
		2352	Raw sockets/select 0.077 sec
		2353	POE/select, components 0.662 sec
		2354	POE/select, raw sockets 0.226 sec
		2355	POE/select, optimized 0.404 sec
		2356
		2357	AnyEvent/select/nb 0.085 sec
		2358	AnyEvent/EV/nb 0.068 sec
		2359	+state machine 0.134 sec
		2360
		2361	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2362	benchmarks actually make blocking connects and use 100% blocking I/O,
		2363	defeating the purpose of an event-based solution. All of the newly
		2364	written AnyEvent benchmarks use 100% non-blocking connects (using
		2365	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2366	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2367	generally require a lot more bookkeeping and event handling than blocking
		2368	connects (which involve a single syscall only).
		2369
		2370	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2371	offers similar expressive power as POE and IO::Lambda, using conventional
		2372	Perl syntax. This means that both the echo server and the client are 100%
		2373	non-blocking, further placing it at a disadvantage.
		2374
		2375	As you can see, the AnyEvent + EV combination even beats the
		2376	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2377	backend easily beats IO::Lambda and POE.
		2378
		2379	And even the 100% non-blocking version written using the high-level (and
		2380	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda
		2381	higher level ("unoptimised") abstractions by a large margin, even though
		2382	it does all of DNS, tcp-connect and socket I/O in a non-blocking way.
		2383
		2384	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2385	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2386	part of the IO::Lambda distribution and were used without any changes.
		2387
		2388
		2389	=head1 SIGNALS
		2390
		2391	AnyEvent currently installs handlers for these signals:
		2392
		2393	=over 4
		2394
		2395	=item SIGCHLD
		2396
		2397	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2398	emulation for event loops that do not support them natively. Also, some
		2399	event loops install a similar handler.
		2400
		2401	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2402	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2403
		2404	=item SIGPIPE
		2405
		2406	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2407	when AnyEvent gets loaded.
		2408
		2409	The rationale for this is that AnyEvent users usually do not really depend
		2410	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2411	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2412	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2413	some random socket.
		2414
		2415	The rationale for installing a no-op handler as opposed to ignoring it is
		2416	that this way, the handler will be restored to defaults on exec.
		2417
		2418	Feel free to install your own handler, or reset it to defaults.
		2419
		2420	=back
		2421
		2422	=cut
		2423
		2424	undef $SIG{CHLD}
		2425	if $SIG{CHLD} eq 'IGNORE';
		2426
		2427	$SIG{PIPE} = sub { }
		2428	unless defined $SIG{PIPE};
		2429
		2430	=head1 RECOMMENDED/OPTIONAL MODULES
		2431
		2432	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2433	it's built-in modules) are required to use it.
		2434
		2435	That does not mean that AnyEvent won't take advantage of some additional
		2436	modules if they are installed.
		2437
		2438	This section epxlains which additional modules will be used, and how they
		2439	affect AnyEvent's operetion.
		2440
		2441	=over 4
		2442
		2443	=item L<Async::Interrupt>
		2444
		2445	This slightly arcane module is used to implement fast signal handling: To
		2446	my knowledge, there is no way to do completely race-free and quick
		2447	signal handling in pure perl. To ensure that signals still get
		2448	delivered, AnyEvent will start an interval timer to wake up perl (and
		2449	catch the signals) with some delay (default is 10 seconds, look for
		2450	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2451
		2452	If this module is available, then it will be used to implement signal
		2453	catching, which means that signals will not be delayed, and the event loop
		2454	will not be interrupted regularly, which is more efficient (And good for
		2455	battery life on laptops).
		2456
		2457	This affects not just the pure-perl event loop, but also other event loops
		2458	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2459
		2460	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2461	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2462	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2463	does nothing for those backends.
		2464
		2465	=item L<EV>
		2466
		2467	This module isn't really "optional", as it is simply one of the backend
		2468	event loops that AnyEvent can use. However, it is simply the best event
		2469	loop available in terms of features, speed and stability: It supports
		2470	the AnyEvent API optimally, implements all the watcher types in XS, does
		2471	automatic timer adjustments even when no monotonic clock is available,
		2472	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2473	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2474	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2475
		2476	=item L<Guard>
		2477
		2478	The guard module, when used, will be used to implement
		2479	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2480	lot less memory), but otherwise doesn't affect guard operation much. It is
		2481	purely used for performance.
		2482
		2483	=item L<JSON> and L<JSON::XS>
		2484
		2485	One of these modules is required when you want to read or write JSON data
		2486	via L<AnyEvent::Handle>. It is also written in pure-perl, but can take
		2487	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2488
		2489	In fact, L<AnyEvent::Handle> will use L<JSON::XS> by default if it is
		2490	installed.
		2491
		2492	=item L<Net::SSLeay>
		2493
		2494	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2495	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2496	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2497
		2498	=item L<Time::HiRes>
		2499
		2500	This module is part of perl since release 5.008. It will be used when the
		2501	chosen event library does not come with a timing source on it's own. The
		2502	pure-perl event loop (L<AnyEvent::Impl::Perl>) will additionally use it to
		2503	try to use a monotonic clock for timing stability.
1407		2504
1408	=back	2505	=back
1409		2506
1410		2507
1411	=head1 FORK	2508	=head1 FORK
…		…
1413	Most event libraries are not fork-safe. The ones who are usually are	2510	Most event libraries are not fork-safe. The ones who are usually are
1414	because they rely on inefficient but fork-safe C<select> or C<poll>	2511	because they rely on inefficient but fork-safe C<select> or C<poll>
1415	calls. Only L<EV> is fully fork-aware.	2512	calls. Only L<EV> is fully fork-aware.
1416		2513
1417	If you have to fork, you must either do so I<before> creating your first	2514	If you have to fork, you must either do so I<before> creating your first
1418	watcher OR you must not use AnyEvent at all in the child.	2515	watcher OR you must not use AnyEvent at all in the child OR you must do
		2516	something completely out of the scope of AnyEvent.
1419		2517
1420		2518
1421	=head1 SECURITY CONSIDERATIONS	2519	=head1 SECURITY CONSIDERATIONS
1422		2520
1423	AnyEvent can be forced to load any event model via	2521	AnyEvent can be forced to load any event model via
…		…
1428	specified in the variable.	2526	specified in the variable.
1429		2527
1430	You can make AnyEvent completely ignore this variable by deleting it	2528	You can make AnyEvent completely ignore this variable by deleting it
1431	before the first watcher gets created, e.g. with a C<BEGIN> block:	2529	before the first watcher gets created, e.g. with a C<BEGIN> block:
1432		2530
1433	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	2531	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1434		2532
1435	use AnyEvent;	2533	use AnyEvent;
1436		2534
1437	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can	2535	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1438	be used to probe what backend is used and gain other information (which is	2536	be used to probe what backend is used and gain other information (which is
1439	probably even less useful to an attacker than PERL_ANYEVENT_MODEL).	2537	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2538	$ENV{PERL_ANYEVENT_STRICT}.
		2539
		2540	Note that AnyEvent will remove I<all> environment variables starting with
		2541	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2542	enabled.
		2543
		2544
		2545	=head1 BUGS
		2546
		2547	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2548	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2549	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2550	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2551	pronounced).
1440		2552
1441		2553
1442	=head1 SEE ALSO	2554	=head1 SEE ALSO
		2555
		2556	Utility functions: L<AnyEvent::Util>.
1443		2557
1444	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,	2558	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
1445	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.	2559	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
1446		2560
1447	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,	2561	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
1448	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,	2562	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
1449	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,	2563	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1450	L<AnyEvent::Impl::POE>.	2564	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>, L<Anyevent::Impl::Irssi>.
1451		2565
		2566	Non-blocking file handles, sockets, TCP clients and
		2567	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
		2568
		2569	Asynchronous DNS: L<AnyEvent::DNS>.
		2570
1452	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,	2571	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>,
		2572	L<Coro::Event>,
1453		2573
1454	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	2574	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::XMPP>,
		2575	L<AnyEvent::HTTP>.
1455		2576
1456		2577
1457	=head1 AUTHOR	2578	=head1 AUTHOR
1458		2579
1459	Marc Lehmann <schmorp@schmorp.de>	2580	Marc Lehmann <schmorp@schmorp.de>
1460	http://home.schmorp.de/	2581	http://home.schmorp.de/
1461		2582
1462	=cut	2583	=cut
1463		2584
1464	1	2585	1
1465		2586

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