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Revision 1.254 by root, Fri Jul 24 08:40:35 2009 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent - provide framework for multiple event loops	3	AnyEvent - events independent of event loop implementation
4		4
5	EV, Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event loops	5	EV, Event, Glib, Tk, Perl, Event::Lib, Qt and POE are various supported
		6	event loops.
6		7
7	=head1 SYNOPSIS	8	=head1 SYNOPSIS
8		9
9	use AnyEvent;	10	use AnyEvent;
10		11
		12	# file descriptor readable
11	my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub {	13	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
		14
		15	# one-shot or repeating timers
		16	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
		17	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...
		18
		19	print AnyEvent->now; # prints current event loop time
		20	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
		21
		22	# POSIX signal
		23	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
		24
		25	# child process exit
		26	my $w = AnyEvent->child (pid => $pid, cb => sub {
		27	my ($pid, $status) = @_;
12	...	28	...
13	});	29	});
14		30
15	my $w = AnyEvent->timer (after => $seconds, cb => sub {	31	# called when event loop idle (if applicable)
16	...	32	my $w = AnyEvent->idle (cb => sub { ... });
17	});
18		33
19	my $w = AnyEvent->condvar; # stores whether a condition was flagged	34	my $w = AnyEvent->condvar; # stores whether a condition was flagged
20	$w->send; # wake up current and all future recv's	35	$w->send; # wake up current and all future recv's
21	$w->recv; # enters "main loop" till $condvar gets ->send	36	$w->recv; # enters "main loop" till $condvar gets ->send
		37	# use a condvar in callback mode:
		38	$w->cb (sub { $_[0]->recv });
		39
		40	=head1 INTRODUCTION/TUTORIAL
		41
		42	This manpage is mainly a reference manual. If you are interested
		43	in a tutorial or some gentle introduction, have a look at the
		44	L<AnyEvent::Intro> manpage.
		45
		46	=head1 SUPPORT
		47
		48	There is a mailinglist for discussing all things AnyEvent, and an IRC
		49	channel, too.
		50
		51	See the AnyEvent project page at the B<Schmorpforge Ta-Sa Software
		52	Respository>, 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
142	You can create an I/O watcher by calling the C<< AnyEvent->io >> method	186	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
143	with the following mandatory key-value pairs as arguments:	187	with the following mandatory key-value pairs as arguments:
144		188
145	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch	189	C<fh> is the Perl I<file handle> (or a naked file descriptor) to watch
		190	for events (AnyEvent might or might not keep a reference to this file
		191	handle). Note that only file handles pointing to things for which
		192	non-blocking operation makes sense are allowed. This includes sockets,
		193	most character devices, pipes, fifos and so on, but not for example files
		194	or block devices.
		195
146	for events. C<poll> must be a string that is either C<r> or C<w>,	196	C<poll> must be a string that is either C<r> or C<w>, which creates a
147	which creates a watcher waiting for "r"eadable or "w"ritable events,	197	watcher waiting for "r"eadable or "w"ritable events, respectively.
		198
148	respectively. C<cb> is the callback to invoke each time the file handle	199	C<cb> is the callback to invoke each time the file handle becomes ready.
149	becomes ready.
150		200
151	Although the callback might get passed parameters, their value and	201	Although the callback might get passed parameters, their value and
152	presence is undefined and you cannot rely on them. Portable AnyEvent	202	presence is undefined and you cannot rely on them. Portable AnyEvent
153	callbacks cannot use arguments passed to I/O watcher callbacks.	203	callbacks cannot use arguments passed to I/O watcher callbacks.
154		204
…		…
158		208
159	Some event loops issue spurious readyness notifications, so you should	209	Some event loops issue spurious readyness notifications, so you should
160	always use non-blocking calls when reading/writing from/to your file	210	always use non-blocking calls when reading/writing from/to your file
161	handles.	211	handles.
162		212
163	Example:
164
165	# wait for readability of STDIN, then read a line and disable the watcher	213	Example: wait for readability of STDIN, then read a line and disable the
		214	watcher.
		215
166	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	216	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
167	chomp (my $input = <STDIN>);	217	chomp (my $input = <STDIN>);
168	warn "read: $input\n";	218	warn "read: $input\n";
169	undef $w;	219	undef $w;
170	});	220	});
…		…
180		230
181	Although the callback might get passed parameters, their value and	231	Although the callback might get passed parameters, their value and
182	presence is undefined and you cannot rely on them. Portable AnyEvent	232	presence is undefined and you cannot rely on them. Portable AnyEvent
183	callbacks cannot use arguments passed to time watcher callbacks.	233	callbacks cannot use arguments passed to time watcher callbacks.
184		234
185	The timer callback will be invoked at most once: if you want a repeating	235	The callback will normally be invoked once only. If you specify another
186	timer you have to create a new watcher (this is a limitation by both Tk	236	parameter, C<interval>, as a strictly positive number (> 0), then the
187	and Glib).	237	callback will be invoked regularly at that interval (in fractional
		238	seconds) after the first invocation. If C<interval> is specified with a
		239	false value, then it is treated as if it were missing.
188		240
189	Example:	241	The callback will be rescheduled before invoking the callback, but no
		242	attempt is done to avoid timer drift in most backends, so the interval is
		243	only approximate.
190		244
191	# fire an event after 7.7 seconds	245	Example: fire an event after 7.7 seconds.
		246
192	my $w = AnyEvent->timer (after => 7.7, cb => sub {	247	my $w = AnyEvent->timer (after => 7.7, cb => sub {
193	warn "timeout\n";	248	warn "timeout\n";
194	});	249	});
195		250
196	# to cancel the timer:	251	# to cancel the timer:
197	undef $w;	252	undef $w;
198		253
199	Example 2:
200
201	# fire an event after 0.5 seconds, then roughly every second	254	Example 2: fire an event after 0.5 seconds, then roughly every second.
202	my $w;
203		255
204	my $cb = sub {
205	# cancel the old timer while creating a new one
206	$w = AnyEvent->timer (after => 1, cb => $cb);	256	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		257	warn "timeout\n";
207	};	258	};
208
209	# start the "loop" by creating the first watcher
210	$w = AnyEvent->timer (after => 0.5, cb => $cb);
211		259
212	=head3 TIMING ISSUES	260	=head3 TIMING ISSUES
213		261
214	There are two ways to handle timers: based on real time (relative, "fire	262	There are two ways to handle timers: based on real time (relative, "fire
215	in 10 seconds") and based on wallclock time (absolute, "fire at 12	263	in 10 seconds") and based on wallclock time (absolute, "fire at 12
…		…
227	timers.	275	timers.
228		276
229	AnyEvent always prefers relative timers, if available, matching the	277	AnyEvent always prefers relative timers, if available, matching the
230	AnyEvent API.	278	AnyEvent API.
231		279
		280	AnyEvent has two additional methods that return the "current time":
		281
		282	=over 4
		283
		284	=item AnyEvent->time
		285
		286	This returns the "current wallclock time" as a fractional number of
		287	seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
		288	return, and the result is guaranteed to be compatible with those).
		289
		290	It progresses independently of any event loop processing, i.e. each call
		291	will check the system clock, which usually gets updated frequently.
		292
		293	=item AnyEvent->now
		294
		295	This also returns the "current wallclock time", but unlike C<time>, above,
		296	this value might change only once per event loop iteration, depending on
		297	the event loop (most return the same time as C<time>, above). This is the
		298	time that AnyEvent's timers get scheduled against.
		299
		300	I<In almost all cases (in all cases if you don't care), this is the
		301	function to call when you want to know the current time.>
		302
		303	This function is also often faster then C<< AnyEvent->time >>, and
		304	thus the preferred method if you want some timestamp (for example,
		305	L<AnyEvent::Handle> uses this to update it's activity timeouts).
		306
		307	The rest of this section is only of relevance if you try to be very exact
		308	with your timing, you can skip it without bad conscience.
		309
		310	For a practical example of when these times differ, consider L<Event::Lib>
		311	and L<EV> and the following set-up:
		312
		313	The event loop is running and has just invoked one of your callback at
		314	time=500 (assume no other callbacks delay processing). In your callback,
		315	you wait a second by executing C<sleep 1> (blocking the process for a
		316	second) and then (at time=501) you create a relative timer that fires
		317	after three seconds.
		318
		319	With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
		320	both return C<501>, because that is the current time, and the timer will
		321	be scheduled to fire at time=504 (C<501> + C<3>).
		322
		323	With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
		324	time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
		325	last event processing phase started. With L<EV>, your timer gets scheduled
		326	to run at time=503 (C<500> + C<3>).
		327
		328	In one sense, L<Event::Lib> is more exact, as it uses the current time
		329	regardless of any delays introduced by event processing. However, most
		330	callbacks do not expect large delays in processing, so this causes a
		331	higher drift (and a lot more system calls to get the current time).
		332
		333	In another sense, L<EV> is more exact, as your timer will be scheduled at
		334	the same time, regardless of how long event processing actually took.
		335
		336	In either case, if you care (and in most cases, you don't), then you
		337	can get whatever behaviour you want with any event loop, by taking the
		338	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
		339	account.
		340
		341	=item AnyEvent->now_update
		342
		343	Some event loops (such as L<EV> or L<AnyEvent::Impl::Perl>) cache
		344	the current time for each loop iteration (see the discussion of L<<
		345	AnyEvent->now >>, above).
		346
		347	When a callback runs for a long time (or when the process sleeps), then
		348	this "current" time will differ substantially from the real time, which
		349	might affect timers and time-outs.
		350
		351	When this is the case, you can call this method, which will update the
		352	event loop's idea of "current time".
		353
		354	Note that updating the time I<might> cause some events to be handled.
		355
		356	=back
		357
232	=head2 SIGNAL WATCHERS	358	=head2 SIGNAL WATCHERS
233		359
234	You can watch for signals using a signal watcher, C<signal> is the signal	360	You can watch for signals using a signal watcher, C<signal> is the signal
235	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to	361	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
236	be invoked whenever a signal occurs.	362	callback to be invoked whenever a signal occurs.
237		363
238	Although the callback might get passed parameters, their value and	364	Although the callback might get passed parameters, their value and
239	presence is undefined and you cannot rely on them. Portable AnyEvent	365	presence is undefined and you cannot rely on them. Portable AnyEvent
240	callbacks cannot use arguments passed to signal watcher callbacks.	366	callbacks cannot use arguments passed to signal watcher callbacks.
241		367
242	Multiple signal occurances can be clumped together into one callback	368	Multiple signal occurrences can be clumped together into one callback
243	invocation, and callback invocation will be synchronous. synchronous means	369	invocation, and callback invocation will be synchronous. Synchronous means
244	that it might take a while until the signal gets handled by the process,	370	that it might take a while until the signal gets handled by the process,
245	but it is guarenteed not to interrupt any other callbacks.	371	but it is guaranteed not to interrupt any other callbacks.
246		372
247	The main advantage of using these watchers is that you can share a signal	373	The main advantage of using these watchers is that you can share a signal
248	between multiple watchers.	374	between multiple watchers, and AnyEvent will ensure that signals will not
		375	interrupt your program at bad times.
249		376
250	This watcher might use C<%SIG>, so programs overwriting those signals	377	This watcher might use C<%SIG> (depending on the event loop used),
251	directly will likely not work correctly.	378	so programs overwriting those signals directly will likely not work
		379	correctly.
252		380
253	Example: exit on SIGINT	381	Example: exit on SIGINT
254		382
255	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	383	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
256		384
		385	=head3 Signal Races, Delays and Workarounds
		386
		387	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		388	callbacks to signals in a generic way, which is a pity, as you cannot do
		389	race-free signal handling in perl. AnyEvent will try to do it's best, but
		390	in some cases, signals will be delayed. The maximum time a signal might
		391	be delayed is specified in C<$AnyEvent::MAX_SIGNAL_LATENCY> (default: 10
		392	seconds). This variable can be changed only before the first signal
		393	watcher is created, and should be left alone otherwise. Higher values
		394	will cause fewer spurious wake-ups, which is better for power and CPU
		395	saving. All these problems can be avoided by installing the optional
		396	L<Async::Interrupt> module. This will not work with inherently broken
		397	event loops such as L<Event> or L<Event::Lib> (and not with L<POE>
		398	currently, as POE does it's own workaround with one-second latency). With
		399	those, you just have to suffer the delays.
		400
257	=head2 CHILD PROCESS WATCHERS	401	=head2 CHILD PROCESS WATCHERS
258		402
259	You can also watch on a child process exit and catch its exit status.	403	You can also watch on a child process exit and catch its exit status.
260		404
261	The child process is specified by the C<pid> argument (if set to C<0>, it	405	The child process is specified by the C<pid> argument (one some backends,
262	watches for any child process exit). The watcher will trigger as often	406	using C<0> watches for any child process exit, on others this will
263	as status change for the child are received. This works by installing a	407	croak). The watcher will be triggered only when the child process has
264	signal handler for C<SIGCHLD>. The callback will be called with the pid	408	finished and an exit status is available, not on any trace events
265	and exit status (as returned by waitpid), so unlike other watcher types,	409	(stopped/continued).
266	you I<can> rely on child watcher callback arguments.	410
		411	The callback will be called with the pid and exit status (as returned by
		412	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		413	callback arguments.
		414
		415	This watcher type works by installing a signal handler for C<SIGCHLD>,
		416	and since it cannot be shared, nothing else should use SIGCHLD or reap
		417	random child processes (waiting for specific child processes, e.g. inside
		418	C<system>, is just fine).
267		419
268	There is a slight catch to child watchers, however: you usually start them	420	There is a slight catch to child watchers, however: you usually start them
269	I<after> the child process was created, and this means the process could	421	I<after> the child process was created, and this means the process could
270	have exited already (and no SIGCHLD will be sent anymore).	422	have exited already (and no SIGCHLD will be sent anymore).
271		423
272	Not all event models handle this correctly (POE doesn't), but even for	424	Not all event models handle this correctly (neither POE nor IO::Async do,
		425	see their AnyEvent::Impl manpages for details), but even for event models
273	event models that I<do> handle this correctly, they usually need to be	426	that I<do> handle this correctly, they usually need to be loaded before
274	loaded before the process exits (i.e. before you fork in the first place).	427	the process exits (i.e. before you fork in the first place). AnyEvent's
		428	pure perl event loop handles all cases correctly regardless of when you
		429	start the watcher.
275		430
276	This means you cannot create a child watcher as the very first thing in an	431	This means you cannot create a child watcher as the very first
277	AnyEvent program, you I<have> to create at least one watcher before you	432	thing in an AnyEvent program, you I<have> to create at least one
278	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).	433	watcher before you C<fork> the child (alternatively, you can call
		434	C<AnyEvent::detect>).
		435
		436	As most event loops do not support waiting for child events, they will be
		437	emulated by AnyEvent in most cases, in which the latency and race problems
		438	mentioned in the description of signal watchers apply.
279		439
280	Example: fork a process and wait for it	440	Example: fork a process and wait for it
281		441
282	my $done = AnyEvent->condvar;	442	my $done = AnyEvent->condvar;
283		443
284	my $pid = fork or exit 5;	444	my $pid = fork or exit 5;
285		445
286	my $w = AnyEvent->child (	446	my $w = AnyEvent->child (
287	pid => $pid,	447	pid => $pid,
288	cb => sub {	448	cb => sub {
289	my ($pid, $status) = @_;	449	my ($pid, $status) = @_;
290	warn "pid $pid exited with status $status";	450	warn "pid $pid exited with status $status";
291	$done->send;	451	$done->send;
292	},	452	},
293	);	453	);
294		454
295	# do something else, then wait for process exit	455	# do something else, then wait for process exit
296	$done->recv;	456	$done->recv;
		457
		458	=head2 IDLE WATCHERS
		459
		460	Sometimes there is a need to do something, but it is not so important
		461	to do it instantly, but only when there is nothing better to do. This
		462	"nothing better to do" is usually defined to be "no other events need
		463	attention by the event loop".
		464
		465	Idle watchers ideally get invoked when the event loop has nothing
		466	better to do, just before it would block the process to wait for new
		467	events. Instead of blocking, the idle watcher is invoked.
		468
		469	Most event loops unfortunately do not really support idle watchers (only
		470	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		471	will simply call the callback "from time to time".
		472
		473	Example: read lines from STDIN, but only process them when the
		474	program is otherwise idle:
		475
		476	my @lines; # read data
		477	my $idle_w;
		478	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		479	push @lines, scalar <STDIN>;
		480
		481	# start an idle watcher, if not already done
		482	$idle_w ||= AnyEvent->idle (cb => sub {
		483	# handle only one line, when there are lines left
		484	if (my $line = shift @lines) {
		485	print "handled when idle: $line";
		486	} else {
		487	# otherwise disable the idle watcher again
		488	undef $idle_w;
		489	}
		490	});
		491	});
297		492
298	=head2 CONDITION VARIABLES	493	=head2 CONDITION VARIABLES
299		494
300	If you are familiar with some event loops you will know that all of them	495	If you are familiar with some event loops you will know that all of them
301	require you to run some blocking "loop", "run" or similar function that	496	require you to run some blocking "loop", "run" or similar function that
302	will actively watch for new events and call your callbacks.	497	will actively watch for new events and call your callbacks.
303		498
304	AnyEvent is different, it expects somebody else to run the event loop and	499	AnyEvent is slightly different: it expects somebody else to run the event
305	will only block when necessary (usually when told by the user).	500	loop and will only block when necessary (usually when told by the user).
306		501
307	The instrument to do that is called a "condition variable", so called	502	The instrument to do that is called a "condition variable", so called
308	because they represent a condition that must become true.	503	because they represent a condition that must become true.
		504
		505	Now is probably a good time to look at the examples further below.
309		506
310	Condition variables can be created by calling the C<< AnyEvent->condvar	507	Condition variables can be created by calling the C<< AnyEvent->condvar
311	>> method, usually without arguments. The only argument pair allowed is	508	>> method, usually without arguments. The only argument pair allowed is
312	C<cb>, which specifies a callback to be called when the condition variable	509	C<cb>, which specifies a callback to be called when the condition variable
313	becomes true.	510	becomes true, with the condition variable as the first argument (but not
		511	the results).
314		512
315	After creation, the conditon variable is "false" until it becomes "true"	513	After creation, the condition variable is "false" until it becomes "true"
316	by calling the C<send> method.	514	by calling the C<send> method (or calling the condition variable as if it
		515	were a callback, read about the caveats in the description for the C<<
		516	->send >> method).
317		517
318	Condition variables are similar to callbacks, except that you can	518	Condition variables are similar to callbacks, except that you can
319	optionally wait for them. They can also be called merge points - points	519	optionally wait for them. They can also be called merge points - points
320	in time where multiple outstandign events have been processed. And yet	520	in time where multiple outstanding events have been processed. And yet
321	another way to call them is transations - each condition variable can be	521	another way to call them is transactions - each condition variable can be
322	used to represent a transaction, which finishes at some point and delivers	522	used to represent a transaction, which finishes at some point and delivers
323	a result.	523	a result. And yet some people know them as "futures" - a promise to
		524	compute/deliver something that you can wait for.
324		525
325	Condition variables are very useful to signal that something has finished,	526	Condition variables are very useful to signal that something has finished,
326	for example, if you write a module that does asynchronous http requests,	527	for example, if you write a module that does asynchronous http requests,
327	then a condition variable would be the ideal candidate to signal the	528	then a condition variable would be the ideal candidate to signal the
328	availability of results. The user can either act when the callback is	529	availability of results. The user can either act when the callback is
…		…
332	you can block your main program until an event occurs - for example, you	533	you can block your main program until an event occurs - for example, you
333	could C<< ->recv >> in your main program until the user clicks the Quit	534	could C<< ->recv >> in your main program until the user clicks the Quit
334	button of your app, which would C<< ->send >> the "quit" event.	535	button of your app, which would C<< ->send >> the "quit" event.
335		536
336	Note that condition variables recurse into the event loop - if you have	537	Note that condition variables recurse into the event loop - if you have
337	two pieces of code that call C<< ->recv >> in a round-robbin fashion, you	538	two pieces of code that call C<< ->recv >> in a round-robin fashion, you
338	lose. Therefore, condition variables are good to export to your caller, but	539	lose. Therefore, condition variables are good to export to your caller, but
339	you should avoid making a blocking wait yourself, at least in callbacks,	540	you should avoid making a blocking wait yourself, at least in callbacks,
340	as this asks for trouble.	541	as this asks for trouble.
341		542
342	Condition variables are represented by hash refs in perl, and the keys	543	Condition variables are represented by hash refs in perl, and the keys
…		…
347		548
348	There are two "sides" to a condition variable - the "producer side" which	549	There are two "sides" to a condition variable - the "producer side" which
349	eventually calls C<< -> send >>, and the "consumer side", which waits	550	eventually calls C<< -> send >>, and the "consumer side", which waits
350	for the send to occur.	551	for the send to occur.
351		552
352	Example:	553	Example: wait for a timer.
353		554
354	# wait till the result is ready	555	# wait till the result is ready
355	my $result_ready = AnyEvent->condvar;	556	my $result_ready = AnyEvent->condvar;
356		557
357	# do something such as adding a timer	558	# do something such as adding a timer
…		…
362	after => 1,	563	after => 1,
363	cb => sub { $result_ready->send },	564	cb => sub { $result_ready->send },
364	);	565	);
365		566
366	# this "blocks" (while handling events) till the callback	567	# this "blocks" (while handling events) till the callback
367	# calls send	568	# calls -<send
368	$result_ready->recv;	569	$result_ready->recv;
		570
		571	Example: wait for a timer, but take advantage of the fact that condition
		572	variables are also callable directly.
		573
		574	my $done = AnyEvent->condvar;
		575	my $delay = AnyEvent->timer (after => 5, cb => $done);
		576	$done->recv;
		577
		578	Example: Imagine an API that returns a condvar and doesn't support
		579	callbacks. This is how you make a synchronous call, for example from
		580	the main program:
		581
		582	use AnyEvent::CouchDB;
		583
		584	...
		585
		586	my @info = $couchdb->info->recv;
		587
		588	And this is how you would just set a callback to be called whenever the
		589	results are available:
		590
		591	$couchdb->info->cb (sub {
		592	my @info = $_[0]->recv;
		593	});
369		594
370	=head3 METHODS FOR PRODUCERS	595	=head3 METHODS FOR PRODUCERS
371		596
372	These methods should only be used by the producing side, i.e. the	597	These methods should only be used by the producing side, i.e. the
373	code/module that eventually sends the signal. Note that it is also	598	code/module that eventually sends the signal. Note that it is also
…		…
386	immediately from within send.	611	immediately from within send.
387		612
388	Any arguments passed to the C<send> call will be returned by all	613	Any arguments passed to the C<send> call will be returned by all
389	future C<< ->recv >> calls.	614	future C<< ->recv >> calls.
390		615
		616	Condition variables are overloaded so one can call them directly (as if
		617	they were a code reference). Calling them directly is the same as calling
		618	C<send>.
		619
391	=item $cv->croak ($error)	620	=item $cv->croak ($error)
392		621
393	Similar to send, but causes all call's to C<< ->recv >> to invoke	622	Similar to send, but causes all call's to C<< ->recv >> to invoke
394	C<Carp::croak> with the given error message/object/scalar.	623	C<Carp::croak> with the given error message/object/scalar.
395		624
396	This can be used to signal any errors to the condition variable	625	This can be used to signal any errors to the condition variable
397	user/consumer.	626	user/consumer. Doing it this way instead of calling C<croak> directly
		627	delays the error detetcion, but has the overwhelmign advantage that it
		628	diagnoses the error at the place where the result is expected, and not
		629	deep in some event clalback without connection to the actual code causing
		630	the problem.
398		631
399	=item $cv->begin ([group callback])	632	=item $cv->begin ([group callback])
400		633
401	=item $cv->end	634	=item $cv->end
402
403	These two methods are EXPERIMENTAL and MIGHT CHANGE.
404		635
405	These two methods can be used to combine many transactions/events into	636	These two methods can be used to combine many transactions/events into
406	one. For example, a function that pings many hosts in parallel might want	637	one. For example, a function that pings many hosts in parallel might want
407	to use a condition variable for the whole process.	638	to use a condition variable for the whole process.
408		639
…		…
410	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end	641	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	642	>>, the (last) callback passed to C<begin> will be executed. That callback
412	is I<supposed> to call C<< ->send >>, but that is not required. If no	643	is I<supposed> to call C<< ->send >>, but that is not required. If no
413	callback was set, C<send> will be called without any arguments.	644	callback was set, C<send> will be called without any arguments.
414		645
415	Let's clarify this with the ping example:	646	You can think of C<< $cv->send >> giving you an OR condition (one call
		647	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		648	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		649
		650	Let's start with a simple example: you have two I/O watchers (for example,
		651	STDOUT and STDERR for a program), and you want to wait for both streams to
		652	close before activating a condvar:
		653
		654	my $cv = AnyEvent->condvar;
		655
		656	$cv->begin; # first watcher
		657	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		658	defined sysread $fh1, my $buf, 4096
		659	or $cv->end;
		660	});
		661
		662	$cv->begin; # second watcher
		663	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		664	defined sysread $fh2, my $buf, 4096
		665	or $cv->end;
		666	});
		667
		668	$cv->recv;
		669
		670	This works because for every event source (EOF on file handle), there is
		671	one call to C<begin>, so the condvar waits for all calls to C<end> before
		672	sending.
		673
		674	The ping example mentioned above is slightly more complicated, as the
		675	there are results to be passwd back, and the number of tasks that are
		676	begung can potentially be zero:
416		677
417	my $cv = AnyEvent->condvar;	678	my $cv = AnyEvent->condvar;
418		679
419	my %result;	680	my %result;
420	$cv->begin (sub { $cv->send (\%result) });	681	$cv->begin (sub { $cv->send (\%result) });
…		…
440	loop, which serves two important purposes: first, it sets the callback	701	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	702	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	703	C<send> is called even when C<no> hosts are being pinged (the loop
443	doesn't execute once).	704	doesn't execute once).
444		705
445	This is the general pattern when you "fan out" into multiple subrequests:	706	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>	707	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	708	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>.	709	subrequest you start, call C<begin> and for each subrequest you finish,
		710	call C<end>.
449		711
450	=back	712	=back
451		713
452	=head3 METHODS FOR CONSUMERS	714	=head3 METHODS FOR CONSUMERS
453		715
…		…
469	function will call C<croak>.	731	function will call C<croak>.
470		732
471	In list context, all parameters passed to C<send> will be returned,	733	In list context, all parameters passed to C<send> will be returned,
472	in scalar context only the first one will be returned.	734	in scalar context only the first one will be returned.
473		735
		736	Note that doing a blocking wait in a callback is not supported by any
		737	event loop, that is, recursive invocation of a blocking C<< ->recv
		738	>> is not allowed, and the C<recv> call will C<croak> if such a
		739	condition is detected. This condition can be slightly loosened by using
		740	L<Coro::AnyEvent>, which allows you to do a blocking C<< ->recv >> from
		741	any thread that doesn't run the event loop itself.
		742
474	Not all event models support a blocking wait - some die in that case	743	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	744	(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	745	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	746	caller decide whether the call will block or not (for example, by coupling
478	condition variables with some kind of request results and supporting	747	condition variables with some kind of request results and supporting
479	callbacks so the caller knows that getting the result will not block,	748	callbacks so the caller knows that getting the result will not block,
480	while still suppporting blocking waits if the caller so desires).	749	while still supporting blocking waits if the caller so desires).
481
482	Another reason I<never> to C<< ->recv >> in a module is that you cannot
483	sensibly have two C<< ->recv >>'s in parallel, as that would require
484	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
485	can supply.
486
487	The L<Coro> module, however, I<can> and I<does> supply coroutines and, in
488	fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe
489	versions and also integrates coroutines into AnyEvent, making blocking
490	C<< ->recv >> calls perfectly safe as long as they are done from another
491	coroutine (one that doesn't run the event loop).
492		750
493	You can ensure that C<< -recv >> never blocks by setting a callback and	751	You can ensure that C<< -recv >> never blocks by setting a callback and
494	only calling C<< ->recv >> from within that callback (or at a later	752	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	753	time). This will work even when the event loop does not support blocking
496	waits otherwise.	754	waits otherwise.
…		…
498	=item $bool = $cv->ready	756	=item $bool = $cv->ready
499		757
500	Returns true when the condition is "true", i.e. whether C<send> or	758	Returns true when the condition is "true", i.e. whether C<send> or
501	C<croak> have been called.	759	C<croak> have been called.
502		760
503	=item $cb = $cv->cb ([new callback])	761	=item $cb = $cv->cb ($cb->($cv))
504		762
505	This is a mutator function that returns the callback set and optionally	763	This is a mutator function that returns the callback set and optionally
506	replaces it before doing so.	764	replaces it before doing so.
507		765
508	The callback will be called when the condition becomes "true", i.e. when	766	The callback will be called when the condition becomes "true", i.e. when
509	C<send> or C<croak> are called. Calling C<recv> inside the callback	767	C<send> or C<croak> are called, with the only argument being the condition
510	or at any later time is guaranteed not to block.	768	variable itself. Calling C<recv> inside the callback or at any later time
		769	is guaranteed not to block.
511		770
512	=back	771	=back
513		772
		773	=head1 SUPPORTED EVENT LOOPS/BACKENDS
		774
		775	The available backend classes are (every class has its own manpage):
		776
		777	=over 4
		778
		779	=item Backends that are autoprobed when no other event loop can be found.
		780
		781	EV is the preferred backend when no other event loop seems to be in
		782	use. If EV is not installed, then AnyEvent will try Event, and, failing
		783	that, will fall back to its own pure-perl implementation, which is
		784	available everywhere as it comes with AnyEvent itself.
		785
		786	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		787	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		788	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
		789
		790	=item Backends that are transparently being picked up when they are used.
		791
		792	These will be used when they are currently loaded when the first watcher
		793	is created, in which case it is assumed that the application is using
		794	them. This means that AnyEvent will automatically pick the right backend
		795	when the main program loads an event module before anything starts to
		796	create watchers. Nothing special needs to be done by the main program.
		797
		798	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		799	AnyEvent::Impl::Tk based on Tk, very broken.
		800	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		801	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		802	AnyEvent::Impl::Irssi used when running within irssi.
		803
		804	=item Backends with special needs.
		805
		806	Qt requires the Qt::Application to be instantiated first, but will
		807	otherwise be picked up automatically. As long as the main program
		808	instantiates the application before any AnyEvent watchers are created,
		809	everything should just work.
		810
		811	AnyEvent::Impl::Qt based on Qt.
		812
		813	Support for IO::Async can only be partial, as it is too broken and
		814	architecturally limited to even support the AnyEvent API. It also
		815	is the only event loop that needs the loop to be set explicitly, so
		816	it can only be used by a main program knowing about AnyEvent. See
		817	L<AnyEvent::Impl::Async> for the gory details.
		818
		819	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
		820
		821	=item Event loops that are indirectly supported via other backends.
		822
		823	Some event loops can be supported via other modules:
		824
		825	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		826
		827	B<WxWidgets> has no support for watching file handles. However, you can
		828	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		829	polls 20 times per second, which was considered to be too horrible to even
		830	consider for AnyEvent.
		831
		832	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		833	backend, so it can be supported through POE.
		834
		835	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		836	load L<POE> when detecting them, in the hope that POE will pick them up,
		837	in which case everything will be automatic.
		838
		839	=back
		840
514	=head1 GLOBAL VARIABLES AND FUNCTIONS	841	=head1 GLOBAL VARIABLES AND FUNCTIONS
515		842
		843	These are not normally required to use AnyEvent, but can be useful to
		844	write AnyEvent extension modules.
		845
516	=over 4	846	=over 4
517		847
518	=item $AnyEvent::MODEL	848	=item $AnyEvent::MODEL
519		849
520	Contains C<undef> until the first watcher is being created. Then it	850	Contains C<undef> until the first watcher is being created, before the
		851	backend has been autodetected.
		852
521	contains the event model that is being used, which is the name of the	853	Afterwards it contains the event model that is being used, which is the
522	Perl class implementing the model. This class is usually one of the	854	name of the Perl class implementing the model. This class is usually one
523	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	855	of the C<AnyEvent::Impl:xxx> modules, but can be any other class in the
524	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	856	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
525		857	will be C<urxvt::anyevent>).
526	The known classes so far are:
527
528	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
529	AnyEvent::Impl::Event based on Event, second best choice.
530	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
531	AnyEvent::Impl::Glib based on Glib, third-best choice.
532	AnyEvent::Impl::Tk based on Tk, very bad choice.
533	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
534	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
535	AnyEvent::Impl::POE based on POE, not generic enough for full support.
536
537	There is no support for WxWidgets, as WxWidgets has no support for
538	watching file handles. However, you can use WxWidgets through the
539	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
540	second, which was considered to be too horrible to even consider for
541	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
542	it's adaptor.
543
544	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
545	autodetecting them.
546		858
547	=item AnyEvent::detect	859	=item AnyEvent::detect
548		860
549	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	861	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
550	if necessary. You should only call this function right before you would	862	if necessary. You should only call this function right before you would
551	have created an AnyEvent watcher anyway, that is, as late as possible at	863	have created an AnyEvent watcher anyway, that is, as late as possible at
552	runtime.	864	runtime, and not e.g. while initialising of your module.
		865
		866	If you need to do some initialisation before AnyEvent watchers are
		867	created, use C<post_detect>.
553		868
554	=item $guard = AnyEvent::post_detect { BLOCK }	869	=item $guard = AnyEvent::post_detect { BLOCK }
555		870
556	Arranges for the code block to be executed as soon as the event model is	871	Arranges for the code block to be executed as soon as the event model is
557	autodetected (or immediately if this has already happened).	872	autodetected (or immediately if this has already happened).
558		873
		874	The block will be executed I<after> the actual backend has been detected
		875	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		876	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		877	other initialisations - see the sources of L<AnyEvent::Strict> or
		878	L<AnyEvent::AIO> to see how this is used.
		879
		880	The most common usage is to create some global watchers, without forcing
		881	event module detection too early, for example, L<AnyEvent::AIO> creates
		882	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		883	avoid autodetecting the event module at load time.
		884
559	If called in scalar or list context, then it creates and returns an object	885	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	886	that automatically removes the callback again when it is destroyed (or
		887	C<undef> when the hook was immediately executed). See L<AnyEvent::AIO> for
561	L<Coro::BDB> for a case where this is useful.	888	a case where this is useful.
		889
		890	Example: Create a watcher for the IO::AIO module and store it in
		891	C<$WATCHER>. Only do so after the event loop is initialised, though.
		892
		893	our WATCHER;
		894
		895	my $guard = AnyEvent::post_detect {
		896	$WATCHER = AnyEvent->io (fh => IO::AIO::poll_fileno, poll => 'r', cb => \&IO::AIO::poll_cb);
		897	};
		898
		899	# the ||= is important in case post_detect immediately runs the block,
		900	# as to not clobber the newly-created watcher. assigning both watcher and
		901	# post_detect guard to the same variable has the advantage of users being
		902	# able to just C<undef $WATCHER> if the watcher causes them grief.
		903
		904	$WATCHER ||= $guard;
562		905
563	=item @AnyEvent::post_detect	906	=item @AnyEvent::post_detect
564		907
565	If there are any code references in this array (you can C<push> to it	908	If there are any code references in this array (you can C<push> to it
566	before or after loading AnyEvent), then they will called directly after	909	before or after loading AnyEvent), then they will called directly after
567	the event loop has been chosen.	910	the event loop has been chosen.
568		911
569	You should check C<$AnyEvent::MODEL> before adding to this array, though:	912	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,	913	if it is defined then the event loop has already been detected, and the
571	and the array will be ignored.	914	array will be ignored.
572		915
573	Best use C<AnyEvent::post_detect { BLOCK }> instead.	916	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		917	it,as it takes care of these details.
		918
		919	This variable is mainly useful for modules that can do something useful
		920	when AnyEvent is used and thus want to know when it is initialised, but do
		921	not need to even load it by default. This array provides the means to hook
		922	into AnyEvent passively, without loading it.
574		923
575	=back	924	=back
576		925
577	=head1 WHAT TO DO IN A MODULE	926	=head1 WHAT TO DO IN A MODULE
578		927
…		…
601		950
602	If it doesn't care, it can just "use AnyEvent" and use it itself, or not	951	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
603	do anything special (it does not need to be event-based) and let AnyEvent	952	do anything special (it does not need to be event-based) and let AnyEvent
604	decide which implementation to chose if some module relies on it.	953	decide which implementation to chose if some module relies on it.
605		954
606	If the main program relies on a specific event model. For example, in	955	If the main program relies on a specific event model - for example, in
607	Gtk2 programs you have to rely on the Glib module. You should load the	956	Gtk2 programs you have to rely on the Glib module - you should load the
608	event module before loading AnyEvent or any module that uses it: generally	957	event module before loading AnyEvent or any module that uses it: generally
609	speaking, you should load it as early as possible. The reason is that	958	speaking, you should load it as early as possible. The reason is that
610	modules might create watchers when they are loaded, and AnyEvent will	959	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	960	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.	961	might chose the wrong one unless you load the correct one yourself.
613		962
614	You can chose to use a rather inefficient pure-perl implementation by	963	You can chose to use a pure-perl implementation by loading the
615	loading the C<AnyEvent::Impl::Perl> module, which gives you similar	964	C<AnyEvent::Impl::Perl> module, which gives you similar behaviour
616	behaviour everywhere, but letting AnyEvent chose is generally better.	965	everywhere, but letting AnyEvent chose the model is generally better.
		966
		967	=head2 MAINLOOP EMULATION
		968
		969	Sometimes (often for short test scripts, or even standalone programs who
		970	only want to use AnyEvent), you do not want to run a specific event loop.
		971
		972	In that case, you can use a condition variable like this:
		973
		974	AnyEvent->condvar->recv;
		975
		976	This has the effect of entering the event loop and looping forever.
		977
		978	Note that usually your program has some exit condition, in which case
		979	it is better to use the "traditional" approach of storing a condition
		980	variable somewhere, waiting for it, and sending it when the program should
		981	exit cleanly.
		982
617		983
618	=head1 OTHER MODULES	984	=head1 OTHER MODULES
619		985
620	The following is a non-exhaustive list of additional modules that use	986	The following is a non-exhaustive list of additional modules that use
621	AnyEvent and can therefore be mixed easily with other AnyEvent modules	987	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	988	modules and other event loops in the same program. Some of the modules
623	available via CPAN.	989	come with AnyEvent, most are available via CPAN.
624		990
625	=over 4	991	=over 4
626		992
627	=item L<AnyEvent::Util>	993	=item L<AnyEvent::Util>
628		994
629	Contains various utility functions that replace often-used but blocking	995	Contains various utility functions that replace often-used but blocking
630	functions such as C<inet_aton> by event-/callback-based versions.	996	functions such as C<inet_aton> by event-/callback-based versions.
631		997
		998	=item L<AnyEvent::Socket>
		999
		1000	Provides various utility functions for (internet protocol) sockets,
		1001	addresses and name resolution. Also functions to create non-blocking tcp
		1002	connections or tcp servers, with IPv6 and SRV record support and more.
		1003
632	=item L<AnyEvent::Handle>	1004	=item L<AnyEvent::Handle>
633		1005
634	Provide read and write buffers and manages watchers for reads and writes.	1006	Provide read and write buffers, manages watchers for reads and writes,
		1007	supports raw and formatted I/O, I/O queued and fully transparent and
		1008	non-blocking SSL/TLS (via L<AnyEvent::TLS>.
		1009
		1010	=item L<AnyEvent::DNS>
		1011
		1012	Provides rich asynchronous DNS resolver capabilities.
		1013
		1014	=item L<AnyEvent::HTTP>
		1015
		1016	A simple-to-use HTTP library that is capable of making a lot of concurrent
		1017	HTTP requests.
635		1018
636	=item L<AnyEvent::HTTPD>	1019	=item L<AnyEvent::HTTPD>
637		1020
638	Provides a simple web application server framework.	1021	Provides a simple web application server framework.
639		1022
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>	1023	=item L<AnyEvent::FastPing>
646		1024
647	The fastest ping in the west.	1025	The fastest ping in the west.
648		1026
		1027	=item L<AnyEvent::DBI>
		1028
		1029	Executes L<DBI> requests asynchronously in a proxy process.
		1030
		1031	=item L<AnyEvent::AIO>
		1032
		1033	Truly asynchronous I/O, should be in the toolbox of every event
		1034	programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
		1035	together.
		1036
		1037	=item L<AnyEvent::BDB>
		1038
		1039	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
		1040	L<BDB> and AnyEvent together.
		1041
		1042	=item L<AnyEvent::GPSD>
		1043
		1044	A non-blocking interface to gpsd, a daemon delivering GPS information.
		1045
649	=item L<Net::IRC3>	1046	=item L<AnyEvent::IRC>
650		1047
651	AnyEvent based IRC client module family.	1048	AnyEvent based IRC client module family (replacing the older Net::IRC3).
652		1049
653	=item L<Net::XMPP2>	1050	=item L<AnyEvent::XMPP>
654		1051
655	AnyEvent based XMPP (Jabber protocol) module family.	1052	AnyEvent based XMPP (Jabber protocol) module family (replacing the older
		1053	Net::XMPP2>.
		1054
		1055	=item L<AnyEvent::IGS>
		1056
		1057	A non-blocking interface to the Internet Go Server protocol (used by
		1058	L<App::IGS>).
656		1059
657	=item L<Net::FCP>	1060	=item L<Net::FCP>
658		1061
659	AnyEvent-based implementation of the Freenet Client Protocol, birthplace	1062	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
660	of AnyEvent.	1063	of AnyEvent.
…		…
665		1068
666	=item L<Coro>	1069	=item L<Coro>
667		1070
668	Has special support for AnyEvent via L<Coro::AnyEvent>.	1071	Has special support for AnyEvent via L<Coro::AnyEvent>.
669		1072
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	1073	=back
686		1074
687	=cut	1075	=cut
688		1076
689	package AnyEvent;	1077	package AnyEvent;
690		1078
		1079	# basically a tuned-down version of common::sense
		1080	sub common_sense {
691	no warnings;	1081	# no warnings
692	use strict;	1082	${^WARNING_BITS} ^= ${^WARNING_BITS};
		1083	# use strict vars subs
		1084	$^H |= 0x00000600;
		1085	}
693		1086
		1087	BEGIN { AnyEvent::common_sense }
		1088
694	use Carp;	1089	use Carp ();
695		1090
696	our $VERSION = '3.41';	1091	our $VERSION = 4.86;
697	our $MODEL;	1092	our $MODEL;
698		1093
699	our $AUTOLOAD;	1094	our $AUTOLOAD;
700	our @ISA;	1095	our @ISA;
701		1096
702	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
703
704	our @REGISTRY;	1097	our @REGISTRY;
705		1098
		1099	our $WIN32;
		1100
		1101	our $VERBOSE;
		1102
		1103	BEGIN {
		1104	eval "sub WIN32(){ " . (($^O =~ /mswin32/i)*1) ." }";
		1105	eval "sub TAINT(){ " . (${^TAINT}*1) . " }";
		1106
		1107	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1108	if ${^TAINT};
		1109
		1110	$VERBOSE = $ENV{PERL_ANYEVENT_VERBOSE}*1;
		1111
		1112	}
		1113
		1114	our $MAX_SIGNAL_LATENCY = 10;
		1115
		1116	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
		1117
		1118	{
		1119	my $idx;
		1120	$PROTOCOL{$_} = ++$idx
		1121	for reverse split /\s*,\s*/,
		1122	$ENV{PERL_ANYEVENT_PROTOCOLS} || "ipv4,ipv6";
		1123	}
		1124
706	my @models = (	1125	my @models = (
707	[EV:: => AnyEvent::Impl::EV::],	1126	[EV:: => AnyEvent::Impl::EV:: , 1],
708	[Event:: => AnyEvent::Impl::Event::],	1127	[Event:: => AnyEvent::Impl::Event::, 1],
		1128	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl:: , 1],
		1129	# everything below here will not (normally) be autoprobed
		1130	# as the pureperl backend should work everywhere
		1131	# and is usually faster
		1132	[Glib:: => AnyEvent::Impl::Glib:: , 1], # becomes extremely slow with many watchers
		1133	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		1134	[Irssi:: => AnyEvent::Impl::Irssi::], # Irssi has a bogus "Event" package
709	[Tk:: => AnyEvent::Impl::Tk::],	1135	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
		1136	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		1137	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
710	[Wx:: => AnyEvent::Impl::POE::],	1138	[Wx:: => AnyEvent::Impl::POE::],
711	[Prima:: => AnyEvent::Impl::POE::],	1139	[Prima:: => AnyEvent::Impl::POE::],
712	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1140	# 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	1141	# byzantine signal and broken child handling, among others.
714	[Glib:: => AnyEvent::Impl::Glib::],	1142	# IO::Async is rather hard to detect, as it doesn't have any
715	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy	1143	# obvious default class.
716	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program	1144	# [0, IO::Async:: => AnyEvent::Impl::IOAsync::], # requires special main program
717	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza	1145	# [0, IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1146	# [0, IO::Async::Notifier:: => AnyEvent::Impl::IOAsync::], # requires special main program
718	);	1147	);
719		1148
720	our %method = map +($_ => 1), qw(io timer signal child condvar one_event DESTROY);	1149	our %method = map +($_ => 1),
		1150	qw(io timer time now now_update signal child idle condvar one_event DESTROY);
721		1151
722	our @post_detect;	1152	our @post_detect;
723		1153
724	sub post_detect(&) {	1154	sub post_detect(&) {
725	my ($cb) = @_;	1155	my ($cb) = @_;
726		1156
727	if ($MODEL) {	1157	if ($MODEL) {
728	$cb->();	1158	$cb->();
729		1159
730	1	1160	undef
731	} else {	1161	} else {
732	push @post_detect, $cb;	1162	push @post_detect, $cb;
733		1163
734	defined wantarray	1164	defined wantarray
735	? bless \$cb, "AnyEvent::Util::Guard"	1165	? bless \$cb, "AnyEvent::Util::postdetect"
736	: ()	1166	: ()
737	}	1167	}
738	}	1168	}
739		1169
740	sub AnyEvent::Util::Guard::DESTROY {	1170	sub AnyEvent::Util::postdetect::DESTROY {
741	@post_detect = grep $_ != ${$_[0]}, @post_detect;	1171	@post_detect = grep $_ != ${$_[0]}, @post_detect;
742	}	1172	}
743		1173
744	sub detect() {	1174	sub detect() {
745	unless ($MODEL) {	1175	unless ($MODEL) {
746	no strict 'refs';	1176	local $SIG{__DIE__};
747		1177
748	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	1178	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
749	my $model = "AnyEvent::Impl::$1";	1179	my $model = "AnyEvent::Impl::$1";
750	if (eval "require $model") {	1180	if (eval "require $model") {
751	$MODEL = $model;	1181	$MODEL = $model;
752	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	1182	warn "AnyEvent: loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.\n" if $VERBOSE >= 2;
753	} else {	1183	} else {
754	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;	1184	warn "AnyEvent: unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@" if $VERBOSE;
755	}	1185	}
756	}	1186	}
757		1187
758	# check for already loaded models	1188	# check for already loaded models
759	unless ($MODEL) {	1189	unless ($MODEL) {
760	for (@REGISTRY, @models) {	1190	for (@REGISTRY, @models) {
761	my ($package, $model) = @$_;	1191	my ($package, $model) = @$_;
762	if (${"$package\::VERSION"} > 0) {	1192	if (${"$package\::VERSION"} > 0) {
763	if (eval "require $model") {	1193	if (eval "require $model") {
764	$MODEL = $model;	1194	$MODEL = $model;
765	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;	1195	warn "AnyEvent: autodetected model '$model', using it.\n" if $VERBOSE >= 2;
766	last;	1196	last;
767	}	1197	}
768	}	1198	}
769	}	1199	}
770		1200
771	unless ($MODEL) {	1201	unless ($MODEL) {
772	# try to load a model	1202	# try to autoload a model
773
774	for (@REGISTRY, @models) {	1203	for (@REGISTRY, @models) {
775	my ($package, $model) = @$_;	1204	my ($package, $model, $autoload) = @$_;
		1205	if (
		1206	$autoload
776	if (eval "require $package"	1207	and eval "require $package"
777	and ${"$package\::VERSION"} > 0	1208	and ${"$package\::VERSION"} > 0
778	and eval "require $model") {	1209	and eval "require $model"
		1210	) {
779	$MODEL = $model;	1211	$MODEL = $model;
780	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;	1212	warn "AnyEvent: autoloaded model '$model', using it.\n" if $VERBOSE >= 2;
781	last;	1213	last;
782	}	1214	}
783	}	1215	}
784		1216
785	$MODEL	1217	$MODEL
786	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.";	1218	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.\n";
787	}	1219	}
788	}	1220	}
789		1221
		1222	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		1223
790	unshift @ISA, $MODEL;	1224	unshift @ISA, $MODEL;
791	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	1225
		1226	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
792		1227
793	(shift @post_detect)->() while @post_detect;	1228	(shift @post_detect)->() while @post_detect;
794	}	1229	}
795		1230
796	$MODEL	1231	$MODEL
…		…
798		1233
799	sub AUTOLOAD {	1234	sub AUTOLOAD {
800	(my $func = $AUTOLOAD) =~ s/.*://;	1235	(my $func = $AUTOLOAD) =~ s/.*://;
801		1236
802	$method{$func}	1237	$method{$func}
803	or croak "$func: not a valid method for AnyEvent objects";	1238	or Carp::croak "$func: not a valid method for AnyEvent objects";
804		1239
805	detect unless $MODEL;	1240	detect unless $MODEL;
806		1241
807	my $class = shift;	1242	my $class = shift;
808	$class->$func (@_);	1243	$class->$func (@_);
809	}	1244	}
810		1245
		1246	# utility function to dup a filehandle. this is used by many backends
		1247	# to support binding more than one watcher per filehandle (they usually
		1248	# allow only one watcher per fd, so we dup it to get a different one).
		1249	sub _dupfh($$;$$) {
		1250	my ($poll, $fh, $r, $w) = @_;
		1251
		1252	# cygwin requires the fh mode to be matching, unix doesn't
		1253	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1254
		1255	open my $fh2, $mode, $fh
		1256	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1257
		1258	# we assume CLOEXEC is already set by perl in all important cases
		1259
		1260	($fh2, $rw)
		1261	}
		1262
811	package AnyEvent::Base;	1263	package AnyEvent::Base;
812		1264
		1265	# default implementations for many methods
		1266
		1267	sub _time {
		1268	# probe for availability of Time::HiRes
		1269	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1270	warn "AnyEvent: using Time::HiRes for sub-second timing accuracy.\n" if $VERBOSE >= 8;
		1271	*_time = \&Time::HiRes::time;
		1272	# if (eval "use POSIX (); (POSIX::times())...
		1273	} else {
		1274	warn "AnyEvent: using built-in time(), WARNING, no sub-second resolution!\n" if $VERBOSE;
		1275	*_time = sub { time }; # epic fail
		1276	}
		1277
		1278	&_time
		1279	}
		1280
		1281	sub time { _time }
		1282	sub now { _time }
		1283	sub now_update { }
		1284
813	# default implementation for ->condvar	1285	# default implementation for ->condvar
814		1286
815	sub condvar {	1287	sub condvar {
816	bless {}, AnyEvent::CondVar::	1288	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
817	}	1289	}
818		1290
819	# default implementation for ->signal	1291	# default implementation for ->signal
820		1292
821	our %SIG_CB;	1293	our $HAVE_ASYNC_INTERRUPT;
		1294	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1295	our (%SIG_ASY, %SIG_ASY_W);
		1296	our ($SIG_COUNT, $SIG_TW);
822		1297
		1298	sub _signal_exec {
		1299	$HAVE_ASYNC_INTERRUPT
		1300	? $SIGPIPE_R->drain
		1301	: sysread $SIGPIPE_R, my $dummy, 9;
		1302
		1303	while (%SIG_EV) {
		1304	for (keys %SIG_EV) {
		1305	delete $SIG_EV{$_};
		1306	$_->() for values %{ $SIG_CB{$_} || {} };
		1307	}
		1308	}
		1309	}
		1310
		1311	# install a dumym wakeupw atcher to reduce signal catching latency
		1312	sub _sig_add() {
		1313	unless ($SIG_COUNT++) {
		1314	# try to align timer on a full-second boundary, if possible
		1315	my $NOW = AnyEvent->now;
		1316
		1317	$SIG_TW = AnyEvent->timer (
		1318	after => $MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1319	interval => $MAX_SIGNAL_LATENCY,
		1320	cb => sub { }, # just for the PERL_ASYNC_CHECK
		1321	);
		1322	}
		1323	}
		1324
		1325	sub _sig_del {
		1326	undef $SIG_TW
		1327	unless --$SIG_COUNT;
		1328	}
		1329
823	sub signal {	1330	sub _signal {
824	my (undef, %arg) = @_;	1331	my (undef, %arg) = @_;
825		1332
826	my $signal = uc $arg{signal}	1333	my $signal = uc $arg{signal}
827	or Carp::croak "required option 'signal' is missing";	1334	or Carp::croak "required option 'signal' is missing";
828		1335
829	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1336	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1337
		1338	if ($HAVE_ASYNC_INTERRUPT) {
		1339	# async::interrupt
		1340
		1341	$SIG_ASY{$signal} ||= do {
		1342	my $asy = new Async::Interrupt
		1343	cb => sub { undef $SIG_EV{$signal} },
		1344	signal => $signal,
		1345	pipe => [$SIGPIPE_R->filenos],
		1346	;
		1347	$asy->pipe_autodrain (0);
		1348
		1349	$asy
		1350	};
		1351
		1352	} else {
		1353	# pure perl
		1354
830	$SIG{$signal} ||= sub {	1355	$SIG{$signal} ||= sub {
831	$_->() for values %{ $SIG_CB{$signal} || {} };	1356	local $!;
		1357	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1358	undef $SIG_EV{$signal};
		1359	};
		1360
		1361	# can't do signal processing without introducing races in pure perl,
		1362	# so limit the signal latency.
		1363	_sig_add;
832	};	1364	}
833		1365
834	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1366	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
835	}	1367	}
836		1368
		1369	sub signal {
		1370	# probe for availability of Async::Interrupt
		1371	if (!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT} && eval "use Async::Interrupt 0.6 (); 1") {
		1372	warn "AnyEvent: using Async::Interrupt for race-free signal handling.\n" if $VERBOSE >= 8;
		1373
		1374	$HAVE_ASYNC_INTERRUPT = 1;
		1375	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1376	$SIG_IO = AnyEvent->io (fh => $SIGPIPE_R->fileno, poll => "r", cb => \&_signal_exec);
		1377
		1378	} else {
		1379	warn "AnyEvent: using emulated perl signal handling with latency timer.\n" if $VERBOSE >= 8;
		1380
		1381	require Fcntl;
		1382
		1383	if (AnyEvent::WIN32) {
		1384	require AnyEvent::Util;
		1385
		1386	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1387	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R) if $SIGPIPE_R;
		1388	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W) if $SIGPIPE_W; # just in case
		1389	} else {
		1390	pipe $SIGPIPE_R, $SIGPIPE_W;
		1391	fcntl $SIGPIPE_R, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_R;
		1392	fcntl $SIGPIPE_W, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_W; # just in case
		1393
		1394	# not strictly required, as $^F is normally 2, but let's make sure...
		1395	fcntl $SIGPIPE_R, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1396	fcntl $SIGPIPE_W, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1397	}
		1398
		1399	$SIGPIPE_R
		1400	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1401
		1402	$SIG_IO = AnyEvent->io (fh => $SIGPIPE_R, poll => "r", cb => \&_signal_exec);
		1403	}
		1404
		1405	*signal = \&_signal;
		1406	&signal
		1407	}
		1408
837	sub AnyEvent::Base::Signal::DESTROY {	1409	sub AnyEvent::Base::signal::DESTROY {
838	my ($signal, $cb) = @{$_[0]};	1410	my ($signal, $cb) = @{$_[0]};
839		1411
		1412	_sig_del;
		1413
840	delete $SIG_CB{$signal}{$cb};	1414	delete $SIG_CB{$signal}{$cb};
841		1415
842	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };	1416	$HAVE_ASYNC_INTERRUPT
		1417	? delete $SIG_ASY{$signal}
		1418	: # delete doesn't work with older perls - they then
		1419	# print weird messages, or just unconditionally exit
		1420	# instead of getting the default action.
		1421	undef $SIG{$signal}
		1422	unless keys %{ $SIG_CB{$signal} };
843	}	1423	}
844		1424
845	# default implementation for ->child	1425	# default implementation for ->child
846		1426
847	our %PID_CB;	1427	our %PID_CB;
848	our $CHLD_W;	1428	our $CHLD_W;
849	our $CHLD_DELAY_W;	1429	our $CHLD_DELAY_W;
850	our $PID_IDLE;
851	our $WNOHANG;	1430	our $WNOHANG;
852		1431
853	sub _child_wait {	1432	sub _emit_childstatus($$) {
854	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1433	my (undef, $rpid, $rstatus) = @_;
		1434
		1435	$_->($rpid, $rstatus)
855	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1436	for values %{ $PID_CB{$rpid} || {} },
856	(values %{ $PID_CB{0} || {} });	1437	values %{ $PID_CB{0} || {} };
857	}
858
859	undef $PID_IDLE;
860	}	1438	}
861		1439
862	sub _sigchld {	1440	sub _sigchld {
863	# make sure we deliver these changes "synchronous" with the event loop.	1441	my $pid;
864	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {	1442
865	undef $CHLD_DELAY_W;	1443	AnyEvent->_emit_childstatus ($pid, $?)
866	&_child_wait;	1444	while ($pid = waitpid -1, $WNOHANG) > 0;
867	});
868	}	1445	}
869		1446
870	sub child {	1447	sub child {
871	my (undef, %arg) = @_;	1448	my (undef, %arg) = @_;
872		1449
873	defined (my $pid = $arg{pid} + 0)	1450	defined (my $pid = $arg{pid} + 0)
874	or Carp::croak "required option 'pid' is missing";	1451	or Carp::croak "required option 'pid' is missing";
875		1452
876	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1453	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
877		1454
878	unless ($WNOHANG) {	1455	# WNOHANG is almost cetrainly 1 everywhere
879	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } || 1;	1456	$WNOHANG ||= $^O =~ /^(?:openbsd|netbsd|linux|freebsd|cygwin|MSWin32)$/
880	}	1457	? 1
		1458	: eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
881		1459
882	unless ($CHLD_W) {	1460	unless ($CHLD_W) {
883	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1461	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
884	# child could be a zombie already, so make at least one round	1462	# child could be a zombie already, so make at least one round
885	&_sigchld;	1463	&_sigchld;
886	}	1464	}
887		1465
888	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	1466	bless [$pid, $arg{cb}], "AnyEvent::Base::child"
889	}	1467	}
890		1468
891	sub AnyEvent::Base::Child::DESTROY {	1469	sub AnyEvent::Base::child::DESTROY {
892	my ($pid, $cb) = @{$_[0]};	1470	my ($pid, $cb) = @{$_[0]};
893		1471
894	delete $PID_CB{$pid}{$cb};	1472	delete $PID_CB{$pid}{$cb};
895	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1473	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
896		1474
897	undef $CHLD_W unless keys %PID_CB;	1475	undef $CHLD_W unless keys %PID_CB;
898	}	1476	}
899		1477
		1478	# idle emulation is done by simply using a timer, regardless
		1479	# of whether the process is idle or not, and not letting
		1480	# the callback use more than 50% of the time.
		1481	sub idle {
		1482	my (undef, %arg) = @_;
		1483
		1484	my ($cb, $w, $rcb) = $arg{cb};
		1485
		1486	$rcb = sub {
		1487	if ($cb) {
		1488	$w = _time;
		1489	&$cb;
		1490	$w = _time - $w;
		1491
		1492	# never use more then 50% of the time for the idle watcher,
		1493	# within some limits
		1494	$w = 0.0001 if $w < 0.0001;
		1495	$w = 5 if $w > 5;
		1496
		1497	$w = AnyEvent->timer (after => $w, cb => $rcb);
		1498	} else {
		1499	# clean up...
		1500	undef $w;
		1501	undef $rcb;
		1502	}
		1503	};
		1504
		1505	$w = AnyEvent->timer (after => 0.05, cb => $rcb);
		1506
		1507	bless \\$cb, "AnyEvent::Base::idle"
		1508	}
		1509
		1510	sub AnyEvent::Base::idle::DESTROY {
		1511	undef $${$_[0]};
		1512	}
		1513
900	package AnyEvent::CondVar;	1514	package AnyEvent::CondVar;
901		1515
902	our @ISA = AnyEvent::CondVar::Base::;	1516	our @ISA = AnyEvent::CondVar::Base::;
903		1517
904	package AnyEvent::CondVar::Base;	1518	package AnyEvent::CondVar::Base;
		1519
		1520	#use overload
		1521	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
		1522	# fallback => 1;
		1523
		1524	# save 300+ kilobytes by dirtily hardcoding overloading
		1525	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1526	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1527	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1528	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1529
		1530	our $WAITING;
905		1531
906	sub _send {	1532	sub _send {
907	# nop	1533	# nop
908	}	1534	}
909		1535
…		…
922	sub ready {	1548	sub ready {
923	$_[0]{_ae_sent}	1549	$_[0]{_ae_sent}
924	}	1550	}
925		1551
926	sub _wait {	1552	sub _wait {
		1553	$WAITING
		1554	and !$_[0]{_ae_sent}
		1555	and Carp::croak "AnyEvent::CondVar: recursive blocking wait detected";
		1556
		1557	local $WAITING = 1;
927	AnyEvent->one_event while !$_[0]{_ae_sent};	1558	AnyEvent->one_event while !$_[0]{_ae_sent};
928	}	1559	}
929		1560
930	sub recv {	1561	sub recv {
931	$_[0]->_wait;	1562	$_[0]->_wait;
…		…
944	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;	1575	$_[0]{_ae_end_cb} = $_[1] if @_ > 1;
945	}	1576	}
946		1577
947	sub end {	1578	sub end {
948	return if --$_[0]{_ae_counter};	1579	return if --$_[0]{_ae_counter};
949	&{ $_[0]{_ae_end_cb} } if $_[0]{_ae_end_cb};	1580	&{ $_[0]{_ae_end_cb} || sub { $_[0]->send } };
950	}	1581	}
951		1582
952	# undocumented/compatibility with pre-3.4	1583	# undocumented/compatibility with pre-3.4
953	*broadcast = \&send;	1584	*broadcast = \&send;
954	*wait = \&_wait;	1585	*wait = \&_wait;
		1586
		1587	=head1 ERROR AND EXCEPTION HANDLING
		1588
		1589	In general, AnyEvent does not do any error handling - it relies on the
		1590	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1591	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1592	checking of all AnyEvent methods, however, which is highly useful during
		1593	development.
		1594
		1595	As for exception handling (i.e. runtime errors and exceptions thrown while
		1596	executing a callback), this is not only highly event-loop specific, but
		1597	also not in any way wrapped by this module, as this is the job of the main
		1598	program.
		1599
		1600	The pure perl event loop simply re-throws the exception (usually
		1601	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1602	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1603	so on.
		1604
		1605	=head1 ENVIRONMENT VARIABLES
		1606
		1607	The following environment variables are used by this module or its
		1608	submodules.
		1609
		1610	Note that AnyEvent will remove I<all> environment variables starting with
		1611	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		1612	enabled.
		1613
		1614	=over 4
		1615
		1616	=item C<PERL_ANYEVENT_VERBOSE>
		1617
		1618	By default, AnyEvent will be completely silent except in fatal
		1619	conditions. You can set this environment variable to make AnyEvent more
		1620	talkative.
		1621
		1622	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1623	conditions, such as not being able to load the event model specified by
		1624	C<PERL_ANYEVENT_MODEL>.
		1625
		1626	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1627	model it chooses.
		1628
		1629	When set to C<8> or higher, then AnyEvent will report extra information on
		1630	which optional modules it loads and how it implements certain features.
		1631
		1632	=item C<PERL_ANYEVENT_STRICT>
		1633
		1634	AnyEvent does not do much argument checking by default, as thorough
		1635	argument checking is very costly. Setting this variable to a true value
		1636	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1637	check the arguments passed to most method calls. If it finds any problems,
		1638	it will croak.
		1639
		1640	In other words, enables "strict" mode.
		1641
		1642	Unlike C<use strict> (or it's modern cousin, C<< use L<common::sense>
		1643	>>, it is definitely recommended to keep it off in production. Keeping
		1644	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		1645	can be very useful, however.
		1646
		1647	=item C<PERL_ANYEVENT_MODEL>
		1648
		1649	This can be used to specify the event model to be used by AnyEvent, before
		1650	auto detection and -probing kicks in. It must be a string consisting
		1651	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1652	and the resulting module name is loaded and if the load was successful,
		1653	used as event model. If it fails to load AnyEvent will proceed with
		1654	auto detection and -probing.
		1655
		1656	This functionality might change in future versions.
		1657
		1658	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1659	could start your program like this:
		1660
		1661	PERL_ANYEVENT_MODEL=Perl perl ...
		1662
		1663	=item C<PERL_ANYEVENT_PROTOCOLS>
		1664
		1665	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1666	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1667	of auto probing).
		1668
		1669	Must be set to a comma-separated list of protocols or address families,
		1670	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1671	used, and preference will be given to protocols mentioned earlier in the
		1672	list.
		1673
		1674	This variable can effectively be used for denial-of-service attacks
		1675	against local programs (e.g. when setuid), although the impact is likely
		1676	small, as the program has to handle conenction and other failures anyways.
		1677
		1678	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1679	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1680	- only support IPv4, never try to resolve or contact IPv6
		1681	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1682	IPv6, but prefer IPv6 over IPv4.
		1683
		1684	=item C<PERL_ANYEVENT_EDNS0>
		1685
		1686	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1687	for DNS. This extension is generally useful to reduce DNS traffic, but
		1688	some (broken) firewalls drop such DNS packets, which is why it is off by
		1689	default.
		1690
		1691	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1692	EDNS0 in its DNS requests.
		1693
		1694	=item C<PERL_ANYEVENT_MAX_FORKS>
		1695
		1696	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1697	will create in parallel.
		1698
		1699	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		1700
		1701	The default value for the C<max_outstanding> parameter for the default DNS
		1702	resolver - this is the maximum number of parallel DNS requests that are
		1703	sent to the DNS server.
		1704
		1705	=item C<PERL_ANYEVENT_RESOLV_CONF>
		1706
		1707	The file to use instead of F</etc/resolv.conf> (or OS-specific
		1708	configuration) in the default resolver. When set to the empty string, no
		1709	default config will be used.
		1710
		1711	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		1712
		1713	When neither C<ca_file> nor C<ca_path> was specified during
		1714	L<AnyEvent::TLS> context creation, and either of these environment
		1715	variables exist, they will be used to specify CA certificate locations
		1716	instead of a system-dependent default.
		1717
		1718	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		1719
		1720	When these are set to C<1>, then the respective modules are not
		1721	loaded. Mostly good for testing AnyEvent itself.
		1722
		1723	=back
955		1724
956	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1725	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
957		1726
958	This is an advanced topic that you do not normally need to use AnyEvent in	1727	This is an advanced topic that you do not normally need to use AnyEvent in
959	a module. This section is only of use to event loop authors who want to	1728	a module. This section is only of use to event loop authors who want to
…		…
993		1762
994	I<rxvt-unicode> also cheats a bit by not providing blocking access to	1763	I<rxvt-unicode> also cheats a bit by not providing blocking access to
995	condition variables: code blocking while waiting for a condition will	1764	condition variables: code blocking while waiting for a condition will
996	C<die>. This still works with most modules/usages, and blocking calls must	1765	C<die>. This still works with most modules/usages, and blocking calls must
997	not be done in an interactive application, so it makes sense.	1766	not be done in an interactive application, so it makes sense.
998
999	=head1 ENVIRONMENT VARIABLES
1000
1001	The following environment variables are used by this module:
1002
1003	=over 4
1004
1005	=item C<PERL_ANYEVENT_VERBOSE>
1006
1007	By default, AnyEvent will be completely silent except in fatal
1008	conditions. You can set this environment variable to make AnyEvent more
1009	talkative.
1010
1011	When set to C<1> or higher, causes AnyEvent to warn about unexpected
1012	conditions, such as not being able to load the event model specified by
1013	C<PERL_ANYEVENT_MODEL>.
1014
1015	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
1016	model it chooses.
1017
1018	=item C<PERL_ANYEVENT_MODEL>
1019
1020	This can be used to specify the event model to be used by AnyEvent, before
1021	autodetection and -probing kicks in. It must be a string consisting
1022	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
1023	and the resulting module name is loaded and if the load was successful,
1024	used as event model. If it fails to load AnyEvent will proceed with
1025	autodetection and -probing.
1026
1027	This functionality might change in future versions.
1028
1029	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
1030	could start your program like this:
1031
1032	PERL_ANYEVENT_MODEL=Perl perl ...
1033
1034	=back
1035		1767
1036	=head1 EXAMPLE PROGRAM	1768	=head1 EXAMPLE PROGRAM
1037		1769
1038	The following program uses an I/O watcher to read data from STDIN, a timer	1770	The following program uses an I/O watcher to read data from STDIN, a timer
1039	to display a message once per second, and a condition variable to quit the	1771	to display a message once per second, and a condition variable to quit the
…		…
1048	poll => 'r',	1780	poll => 'r',
1049	cb => sub {	1781	cb => sub {
1050	warn "io event <$_[0]>\n"; # will always output <r>	1782	warn "io event <$_[0]>\n"; # will always output <r>
1051	chomp (my $input = <STDIN>); # read a line	1783	chomp (my $input = <STDIN>); # read a line
1052	warn "read: $input\n"; # output what has been read	1784	warn "read: $input\n"; # output what has been read
1053	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	1785	$cv->send if $input =~ /^q/i; # quit program if /^q/i
1054	},	1786	},
1055	);	1787	);
1056		1788
1057	my $time_watcher; # can only be used once	1789	my $time_watcher; # can only be used once
1058		1790
…		…
1063	});	1795	});
1064	}	1796	}
1065		1797
1066	new_timer; # create first timer	1798	new_timer; # create first timer
1067		1799
1068	$cv->wait; # wait until user enters /^q/i	1800	$cv->recv; # wait until user enters /^q/i
1069		1801
1070	=head1 REAL-WORLD EXAMPLE	1802	=head1 REAL-WORLD EXAMPLE
1071		1803
1072	Consider the L<Net::FCP> module. It features (among others) the following	1804	Consider the L<Net::FCP> module. It features (among others) the following
1073	API calls, which are to freenet what HTTP GET requests are to http:	1805	API calls, which are to freenet what HTTP GET requests are to http:
…		…
1123	syswrite $txn->{fh}, $txn->{request}	1855	syswrite $txn->{fh}, $txn->{request}
1124	or die "connection or write error";	1856	or die "connection or write error";
1125	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });	1857	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
1126		1858
1127	Again, C<fh_ready_r> waits till all data has arrived, and then stores the	1859	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
1128	result and signals any possible waiters that the request ahs finished:	1860	result and signals any possible waiters that the request has finished:
1129		1861
1130	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};	1862	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
1131		1863
1132	if (end-of-file or data complete) {	1864	if (end-of-file or data complete) {
1133	$txn->{result} = $txn->{buf};	1865	$txn->{result} = $txn->{buf};
1134	$txn->{finished}->broadcast;	1866	$txn->{finished}->send;
1135	$txb->{cb}->($txn) of $txn->{cb}; # also call callback	1867	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
1136	}	1868	}
1137		1869
1138	The C<result> method, finally, just waits for the finished signal (if the	1870	The C<result> method, finally, just waits for the finished signal (if the
1139	request was already finished, it doesn't wait, of course, and returns the	1871	request was already finished, it doesn't wait, of course, and returns the
1140	data:	1872	data:
1141		1873
1142	$txn->{finished}->wait;	1874	$txn->{finished}->recv;
1143	return $txn->{result};	1875	return $txn->{result};
1144		1876
1145	The actual code goes further and collects all errors (C<die>s, exceptions)	1877	The actual code goes further and collects all errors (C<die>s, exceptions)
1146	that occured during request processing. The C<result> method detects	1878	that occurred during request processing. The C<result> method detects
1147	whether an exception as thrown (it is stored inside the $txn object)	1879	whether an exception as thrown (it is stored inside the $txn object)
1148	and just throws the exception, which means connection errors and other	1880	and just throws the exception, which means connection errors and other
1149	problems get reported tot he code that tries to use the result, not in a	1881	problems get reported tot he code that tries to use the result, not in a
1150	random callback.	1882	random callback.
1151		1883
…		…
1182		1914
1183	my $quit = AnyEvent->condvar;	1915	my $quit = AnyEvent->condvar;
1184		1916
1185	$fcp->txn_client_get ($url)->cb (sub {	1917	$fcp->txn_client_get ($url)->cb (sub {
1186	...	1918	...
1187	$quit->broadcast;	1919	$quit->send;
1188	});	1920	});
1189		1921
1190	$quit->wait;	1922	$quit->recv;
1191		1923
1192		1924
1193	=head1 BENCHMARKS	1925	=head1 BENCHMARKS
1194		1926
1195	To give you an idea of the performance and overheads that AnyEvent adds	1927	To give you an idea of the performance and overheads that AnyEvent adds
…		…
1197	of various event loops I prepared some benchmarks.	1929	of various event loops I prepared some benchmarks.
1198		1930
1199	=head2 BENCHMARKING ANYEVENT OVERHEAD	1931	=head2 BENCHMARKING ANYEVENT OVERHEAD
1200		1932
1201	Here is a benchmark of various supported event models used natively and	1933	Here is a benchmark of various supported event models used natively and
1202	through anyevent. The benchmark creates a lot of timers (with a zero	1934	through AnyEvent. The benchmark creates a lot of timers (with a zero
1203	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,	1935	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
1204	which it is), lets them fire exactly once and destroys them again.	1936	which it is), lets them fire exactly once and destroys them again.
1205		1937
1206	Source code for this benchmark is found as F<eg/bench> in the AnyEvent	1938	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
1207	distribution.	1939	distribution.
…		…
1224	all watchers, to avoid adding memory overhead. That means closure creation	1956	all watchers, to avoid adding memory overhead. That means closure creation
1225	and memory usage is not included in the figures.	1957	and memory usage is not included in the figures.
1226		1958
1227	I<invoke> is the time, in microseconds, used to invoke a simple	1959	I<invoke> is the time, in microseconds, used to invoke a simple
1228	callback. The callback simply counts down a Perl variable and after it was	1960	callback. The callback simply counts down a Perl variable and after it was
1229	invoked "watcher" times, it would C<< ->broadcast >> a condvar once to	1961	invoked "watcher" times, it would C<< ->send >> a condvar once to
1230	signal the end of this phase.	1962	signal the end of this phase.
1231		1963
1232	I<destroy> is the time, in microseconds, that it takes to destroy a single	1964	I<destroy> is the time, in microseconds, that it takes to destroy a single
1233	watcher.	1965	watcher.
1234		1966
1235	=head3 Results	1967	=head3 Results
1236		1968
1237	name watchers bytes create invoke destroy comment	1969	name watchers bytes create invoke destroy comment
1238	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	1970	EV/EV 400000 224 0.47 0.35 0.27 EV native interface
1239	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	1971	EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers
1240	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	1972	CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal
1241	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	1973	Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation
1242	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	1974	Event/Event 16000 517 32.20 31.80 0.81 Event native interface
1243	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers	1975	Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers
		1976	IOAsync/Any 16000 989 38.10 32.77 11.13 via IO::Async::Loop::IO_Poll
		1977	IOAsync/Any 16000 990 37.59 29.50 10.61 via IO::Async::Loop::Epoll
1244	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	1978	Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour
1245	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	1979	Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers
1246	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	1980	POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event
1247	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	1981	POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select
1248		1982
1249	=head3 Discussion	1983	=head3 Discussion
1250		1984
1251	The benchmark does I<not> measure scalability of the event loop very	1985	The benchmark does I<not> measure scalability of the event loop very
1252	well. For example, a select-based event loop (such as the pure perl one)	1986	well. For example, a select-based event loop (such as the pure perl one)
…		…
1277	performance becomes really bad with lots of file descriptors (and few of	2011	performance becomes really bad with lots of file descriptors (and few of
1278	them active), of course, but this was not subject of this benchmark.	2012	them active), of course, but this was not subject of this benchmark.
1279		2013
1280	The C<Event> module has a relatively high setup and callback invocation	2014	The C<Event> module has a relatively high setup and callback invocation
1281	cost, but overall scores in on the third place.	2015	cost, but overall scores in on the third place.
		2016
		2017	C<IO::Async> performs admirably well, about on par with C<Event>, even
		2018	when using its pure perl backend.
1282		2019
1283	C<Glib>'s memory usage is quite a bit higher, but it features a	2020	C<Glib>'s memory usage is quite a bit higher, but it features a
1284	faster callback invocation and overall ends up in the same class as	2021	faster callback invocation and overall ends up in the same class as
1285	C<Event>. However, Glib scales extremely badly, doubling the number of	2022	C<Event>. However, Glib scales extremely badly, doubling the number of
1286	watchers increases the processing time by more than a factor of four,	2023	watchers increases the processing time by more than a factor of four,
…		…
1330		2067
1331	=back	2068	=back
1332		2069
1333	=head2 BENCHMARKING THE LARGE SERVER CASE	2070	=head2 BENCHMARKING THE LARGE SERVER CASE
1334		2071
1335	This benchmark atcually benchmarks the event loop itself. It works by	2072	This benchmark actually benchmarks the event loop itself. It works by
1336	creating a number of "servers": each server consists of a socketpair, a	2073	creating a number of "servers": each server consists of a socket pair, a
1337	timeout watcher that gets reset on activity (but never fires), and an I/O	2074	timeout watcher that gets reset on activity (but never fires), and an I/O
1338	watcher waiting for input on one side of the socket. Each time the socket	2075	watcher waiting for input on one side of the socket. Each time the socket
1339	watcher reads a byte it will write that byte to a random other "server".	2076	watcher reads a byte it will write that byte to a random other "server".
1340		2077
1341	The effect is that there will be a lot of I/O watchers, only part of which	2078	The effect is that there will be a lot of I/O watchers, only part of which
1342	are active at any one point (so there is a constant number of active	2079	are active at any one point (so there is a constant number of active
1343	fds for each loop iterstaion, but which fds these are is random). The	2080	fds for each loop iteration, but which fds these are is random). The
1344	timeout is reset each time something is read because that reflects how	2081	timeout is reset each time something is read because that reflects how
1345	most timeouts work (and puts extra pressure on the event loops).	2082	most timeouts work (and puts extra pressure on the event loops).
1346		2083
1347	In this benchmark, we use 10000 socketpairs (20000 sockets), of which 100	2084	In this benchmark, we use 10000 socket pairs (20000 sockets), of which 100
1348	(1%) are active. This mirrors the activity of large servers with many	2085	(1%) are active. This mirrors the activity of large servers with many
1349	connections, most of which are idle at any one point in time.	2086	connections, most of which are idle at any one point in time.
1350		2087
1351	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent	2088	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
1352	distribution.	2089	distribution.
…		…
1354	=head3 Explanation of the columns	2091	=head3 Explanation of the columns
1355		2092
1356	I<sockets> is the number of sockets, and twice the number of "servers" (as	2093	I<sockets> is the number of sockets, and twice the number of "servers" (as
1357	each server has a read and write socket end).	2094	each server has a read and write socket end).
1358		2095
1359	I<create> is the time it takes to create a socketpair (which is	2096	I<create> is the time it takes to create a socket pair (which is
1360	nontrivial) and two watchers: an I/O watcher and a timeout watcher.	2097	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
1361		2098
1362	I<request>, the most important value, is the time it takes to handle a	2099	I<request>, the most important value, is the time it takes to handle a
1363	single "request", that is, reading the token from the pipe and forwarding	2100	single "request", that is, reading the token from the pipe and forwarding
1364	it to another server. This includes deleting the old timeout and creating	2101	it to another server. This includes deleting the old timeout and creating
1365	a new one that moves the timeout into the future.	2102	a new one that moves the timeout into the future.
1366		2103
1367	=head3 Results	2104	=head3 Results
1368		2105
1369	name sockets create request	2106	name sockets create request
1370	EV 20000 69.01 11.16	2107	EV 20000 69.01 11.16
1371	Perl 20000 73.32 35.87	2108	Perl 20000 73.32 35.87
		2109	IOAsync 20000 157.00 98.14 epoll
		2110	IOAsync 20000 159.31 616.06 poll
1372	Event 20000 212.62 257.32	2111	Event 20000 212.62 257.32
1373	Glib 20000 651.16 1896.30	2112	Glib 20000 651.16 1896.30
1374	POE 20000 349.67 12317.24 uses POE::Loop::Event	2113	POE 20000 349.67 12317.24 uses POE::Loop::Event
1375		2114
1376	=head3 Discussion	2115	=head3 Discussion
1377		2116
1378	This benchmark I<does> measure scalability and overall performance of the	2117	This benchmark I<does> measure scalability and overall performance of the
1379	particular event loop.	2118	particular event loop.
…		…
1381	EV is again fastest. Since it is using epoll on my system, the setup time	2120	EV is again fastest. Since it is using epoll on my system, the setup time
1382	is relatively high, though.	2121	is relatively high, though.
1383		2122
1384	Perl surprisingly comes second. It is much faster than the C-based event	2123	Perl surprisingly comes second. It is much faster than the C-based event
1385	loops Event and Glib.	2124	loops Event and Glib.
		2125
		2126	IO::Async performs very well when using its epoll backend, and still quite
		2127	good compared to Glib when using its pure perl backend.
1386		2128
1387	Event suffers from high setup time as well (look at its code and you will	2129	Event suffers from high setup time as well (look at its code and you will
1388	understand why). Callback invocation also has a high overhead compared to	2130	understand why). Callback invocation also has a high overhead compared to
1389	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event	2131	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
1390	uses select or poll in basically all documented configurations.	2132	uses select or poll in basically all documented configurations.
…		…
1437	speed most when you have lots of watchers, not when you only have a few of	2179	speed most when you have lots of watchers, not when you only have a few of
1438	them).	2180	them).
1439		2181
1440	EV is again fastest.	2182	EV is again fastest.
1441		2183
1442	Perl again comes second. It is noticably faster than the C-based event	2184	Perl again comes second. It is noticeably faster than the C-based event
1443	loops Event and Glib, although the difference is too small to really	2185	loops Event and Glib, although the difference is too small to really
1444	matter.	2186	matter.
1445		2187
1446	POE also performs much better in this case, but is is still far behind the	2188	POE also performs much better in this case, but is is still far behind the
1447	others.	2189	others.
…		…
1450		2192
1451	=over 4	2193	=over 4
1452		2194
1453	=item * C-based event loops perform very well with small number of	2195	=item * C-based event loops perform very well with small number of
1454	watchers, as the management overhead dominates.	2196	watchers, as the management overhead dominates.
		2197
		2198	=back
		2199
		2200	=head2 THE IO::Lambda BENCHMARK
		2201
		2202	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2203	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2204	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2205	shouldn't come as a surprise to anybody). As such, the benchmark is
		2206	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2207	very optimal. But how would AnyEvent compare when used without the extra
		2208	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2209
		2210	The benchmark itself creates an echo-server, and then, for 500 times,
		2211	connects to the echo server, sends a line, waits for the reply, and then
		2212	creates the next connection. This is a rather bad benchmark, as it doesn't
		2213	test the efficiency of the framework or much non-blocking I/O, but it is a
		2214	benchmark nevertheless.
		2215
		2216	name runtime
		2217	Lambda/select 0.330 sec
		2218	+ optimized 0.122 sec
		2219	Lambda/AnyEvent 0.327 sec
		2220	+ optimized 0.138 sec
		2221	Raw sockets/select 0.077 sec
		2222	POE/select, components 0.662 sec
		2223	POE/select, raw sockets 0.226 sec
		2224	POE/select, optimized 0.404 sec
		2225
		2226	AnyEvent/select/nb 0.085 sec
		2227	AnyEvent/EV/nb 0.068 sec
		2228	+state machine 0.134 sec
		2229
		2230	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2231	benchmarks actually make blocking connects and use 100% blocking I/O,
		2232	defeating the purpose of an event-based solution. All of the newly
		2233	written AnyEvent benchmarks use 100% non-blocking connects (using
		2234	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2235	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2236	generally require a lot more bookkeeping and event handling than blocking
		2237	connects (which involve a single syscall only).
		2238
		2239	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2240	offers similar expressive power as POE and IO::Lambda, using conventional
		2241	Perl syntax. This means that both the echo server and the client are 100%
		2242	non-blocking, further placing it at a disadvantage.
		2243
		2244	As you can see, the AnyEvent + EV combination even beats the
		2245	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2246	backend easily beats IO::Lambda and POE.
		2247
		2248	And even the 100% non-blocking version written using the high-level (and
		2249	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda by a
		2250	large margin, even though it does all of DNS, tcp-connect and socket I/O
		2251	in a non-blocking way.
		2252
		2253	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2254	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2255	part of the IO::lambda distribution and were used without any changes.
		2256
		2257
		2258	=head1 SIGNALS
		2259
		2260	AnyEvent currently installs handlers for these signals:
		2261
		2262	=over 4
		2263
		2264	=item SIGCHLD
		2265
		2266	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2267	emulation for event loops that do not support them natively. Also, some
		2268	event loops install a similar handler.
		2269
		2270	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2271	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2272
		2273	=item SIGPIPE
		2274
		2275	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2276	when AnyEvent gets loaded.
		2277
		2278	The rationale for this is that AnyEvent users usually do not really depend
		2279	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2280	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2281	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2282	some random socket.
		2283
		2284	The rationale for installing a no-op handler as opposed to ignoring it is
		2285	that this way, the handler will be restored to defaults on exec.
		2286
		2287	Feel free to install your own handler, or reset it to defaults.
		2288
		2289	=back
		2290
		2291	=cut
		2292
		2293	undef $SIG{CHLD}
		2294	if $SIG{CHLD} eq 'IGNORE';
		2295
		2296	$SIG{PIPE} = sub { }
		2297	unless defined $SIG{PIPE};
		2298
		2299	=head1 RECOMMENDED/OPTIONAL MODULES
		2300
		2301	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2302	it's built-in modules) are required to use it.
		2303
		2304	That does not mean that AnyEvent won't take advantage of some additional
		2305	modules if they are installed.
		2306
		2307	This section epxlains which additional modules will be used, and how they
		2308	affect AnyEvent's operetion.
		2309
		2310	=over 4
		2311
		2312	=item L<Async::Interrupt>
		2313
		2314	This slightly arcane module is used to implement fast signal handling: To
		2315	my knowledge, there is no way to do completely race-free and quick
		2316	signal handling in pure perl. To ensure that signals still get
		2317	delivered, AnyEvent will start an interval timer to wake up perl (and
		2318	catch the signals) with some delay (default is 10 seconds, look for
		2319	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2320
		2321	If this module is available, then it will be used to implement signal
		2322	catching, which means that signals will not be delayed, and the event loop
		2323	will not be interrupted regularly, which is more efficient (And good for
		2324	battery life on laptops).
		2325
		2326	This affects not just the pure-perl event loop, but also other event loops
		2327	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2328
		2329	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2330	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2331	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2332	does nothing for those backends.
		2333
		2334	=item L<EV>
		2335
		2336	This module isn't really "optional", as it is simply one of the backend
		2337	event loops that AnyEvent can use. However, it is simply the best event
		2338	loop available in terms of features, speed and stability: It supports
		2339	the AnyEvent API optimally, implements all the watcher types in XS, does
		2340	automatic timer adjustments even when no monotonic clock is available,
		2341	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2342	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2343	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2344
		2345	=item L<Guard>
		2346
		2347	The guard module, when used, will be used to implement
		2348	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2349	lot less memory), but otherwise doesn't affect guard operation much. It is
		2350	purely used for performance.
		2351
		2352	=item L<JSON> and L<JSON::XS>
		2353
		2354	This module is required when you want to read or write JSON data via
		2355	L<AnyEvent::Handle>. It is also written in pure-perl, but can take
		2356	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2357
		2358	In fact, L<AnyEvent::Handle> will use L<JSON::XS> by default if it is
		2359	installed.
		2360
		2361	=item L<Net::SSLeay>
		2362
		2363	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2364	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2365	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2366
		2367	=item L<Time::HiRes>
		2368
		2369	This module is part of perl since release 5.008. It will be used when the
		2370	chosen event library does not come with a timing source on it's own. The
		2371	pure-perl event loop (L<AnyEvent::Impl::Perl>) will additionally use it to
		2372	try to use a monotonic clock for timing stability.
1455		2373
1456	=back	2374	=back
1457		2375
1458		2376
1459	=head1 FORK	2377	=head1 FORK
…		…
1461	Most event libraries are not fork-safe. The ones who are usually are	2379	Most event libraries are not fork-safe. The ones who are usually are
1462	because they rely on inefficient but fork-safe C<select> or C<poll>	2380	because they rely on inefficient but fork-safe C<select> or C<poll>
1463	calls. Only L<EV> is fully fork-aware.	2381	calls. Only L<EV> is fully fork-aware.
1464		2382
1465	If you have to fork, you must either do so I<before> creating your first	2383	If you have to fork, you must either do so I<before> creating your first
1466	watcher OR you must not use AnyEvent at all in the child.	2384	watcher OR you must not use AnyEvent at all in the child OR you must do
		2385	something completely out of the scope of AnyEvent.
1467		2386
1468		2387
1469	=head1 SECURITY CONSIDERATIONS	2388	=head1 SECURITY CONSIDERATIONS
1470		2389
1471	AnyEvent can be forced to load any event model via	2390	AnyEvent can be forced to load any event model via
…		…
1476	specified in the variable.	2395	specified in the variable.
1477		2396
1478	You can make AnyEvent completely ignore this variable by deleting it	2397	You can make AnyEvent completely ignore this variable by deleting it
1479	before the first watcher gets created, e.g. with a C<BEGIN> block:	2398	before the first watcher gets created, e.g. with a C<BEGIN> block:
1480		2399
1481	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	2400	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1482		2401
1483	use AnyEvent;	2402	use AnyEvent;
1484		2403
1485	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can	2404	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1486	be used to probe what backend is used and gain other information (which is	2405	be used to probe what backend is used and gain other information (which is
1487	probably even less useful to an attacker than PERL_ANYEVENT_MODEL).	2406	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2407	$ENV{PERL_ANYEVENT_STRICT}.
		2408
		2409	Note that AnyEvent will remove I<all> environment variables starting with
		2410	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2411	enabled.
		2412
		2413
		2414	=head1 BUGS
		2415
		2416	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2417	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2418	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2419	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2420	pronounced).
1488		2421
1489		2422
1490	=head1 SEE ALSO	2423	=head1 SEE ALSO
		2424
		2425	Utility functions: L<AnyEvent::Util>.
1491		2426
1492	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,	2427	Event modules: L<EV>, L<EV::Glib>, L<Glib::EV>, L<Event>, L<Glib::Event>,
1493	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.	2428	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
1494		2429
1495	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,	2430	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
1496	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,	2431	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
1497	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,	2432	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1498	L<AnyEvent::Impl::POE>.	2433	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>, L<Anyevent::Impl::Irssi>.
1499		2434
		2435	Non-blocking file handles, sockets, TCP clients and
		2436	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
		2437
		2438	Asynchronous DNS: L<AnyEvent::DNS>.
		2439
1500	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,	2440	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>,
		2441	L<Coro::Event>,
1501		2442
1502	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.	2443	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::XMPP>,
		2444	L<AnyEvent::HTTP>.
1503		2445
1504		2446
1505	=head1 AUTHOR	2447	=head1 AUTHOR
1506		2448
1507	Marc Lehmann <schmorp@schmorp.de>	2449	Marc Lehmann <schmorp@schmorp.de>
1508	http://home.schmorp.de/	2450	http://home.schmorp.de/
1509		2451
1510	=cut	2452	=cut
1511		2453
1512	1	2454	1
1513		2455

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