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Revision 1.143 by root, Wed May 28 23:57:38 2008 UTC vs.
Revision 1.244 by root, Fri Jul 17 23:15:57 2009 UTC

1	=head1 => NAME	1	=head1 NAME
2		2
3	AnyEvent - provide framework for multiple event loops	3	AnyEvent - provide framework for multiple event loops
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.
22		45
23	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)	46	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
24		47
25	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	48	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
26	nowadays. So what is different about AnyEvent?	49	nowadays. So what is different about AnyEvent?
27		50
28	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of	51	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
29	policy> and AnyEvent is I<small and efficient>.	52	policy> and AnyEvent is I<small and efficient>.
30		53
31	First and foremost, I<AnyEvent is not an event model> itself, it only	54	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	55	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,	56	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,	57	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	58	only one event loop can be active at the same time in a process. AnyEvent
36	helps hiding the differences between those event loops.	59	cannot change this, but it can hide the differences between those event
		60	loops.
37		61
38	The goal of AnyEvent is to offer module authors the ability to do event	62	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	63	programming (waiting for I/O or timer events) without subscribing to a
40	religion, a way of living, and most importantly: without forcing your	64	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	65	module users into the same thing by forcing them to use the same event
42	model you use.	66	model you use.
43		67
44	For modules like POE or IO::Async (which is a total misnomer as it is	68	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	69	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	70	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	71	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	72	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.	73	module are I<also> forced to use the same event loop you use.
50		74
51	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	75	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
52	fine. AnyEvent + Tk works fine etc. etc. but none of these work together	76	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	77	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,	78	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	79	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	80	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	81	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).	82	to AnyEvent, too, so it is future-proof).
59		83
60	In addition to being free of having to use I<the one and only true event	84	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	85	model>, AnyEvent also is free of bloat and policy: with POE or similar
62	modules, you get an enormous amount of code and strict rules you have to	86	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	87	follow. AnyEvent, on the other hand, is lean and up to the point, by only
…		…
121	These watchers are normal Perl objects with normal Perl lifetime. After	145	These watchers are normal Perl objects with normal Perl lifetime. After
122	creating a watcher it will immediately "watch" for events and invoke the	146	creating a watcher it will immediately "watch" for events and invoke the
123	callback when the event occurs (of course, only when the event model	147	callback when the event occurs (of course, only when the event model
124	is in control).	148	is in control).
125		149
		150	Note that B<callbacks must not permanently change global variables>
		151	potentially in use by the event loop (such as C<$_> or C<$[>) and that B<<
		152	callbacks must not C<die> >>. The former is good programming practise in
		153	Perl and the latter stems from the fact that exception handling differs
		154	widely between event loops.
		155
126	To disable the watcher you have to destroy it (e.g. by setting the	156	To disable the watcher you have to destroy it (e.g. by setting the
127	variable you store it in to C<undef> or otherwise deleting all references	157	variable you store it in to C<undef> or otherwise deleting all references
128	to it).	158	to it).
129		159
130	All watchers are created by calling a method on the C<AnyEvent> class.	160	All watchers are created by calling a method on the C<AnyEvent> class.
…		…
132	Many watchers either are used with "recursion" (repeating timers for	162	Many watchers either are used with "recursion" (repeating timers for
133	example), or need to refer to their watcher object in other ways.	163	example), or need to refer to their watcher object in other ways.
134		164
135	An any way to achieve that is this pattern:	165	An any way to achieve that is this pattern:
136		166
137	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	167	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
138	# you can use $w here, for example to undef it	168	# you can use $w here, for example to undef it
139	undef $w;	169	undef $w;
140	});	170	});
141		171
142	Note that C<my $w; $w => combination. This is necessary because in Perl,	172	Note that C<my $w; $w => combination. This is necessary because in Perl,
143	my variables are only visible after the statement in which they are	173	my variables are only visible after the statement in which they are
144	declared.	174	declared.
145		175
146	=head2 I/O WATCHERS	176	=head2 I/O WATCHERS
147		177
148	You can create an I/O watcher by calling the C<< AnyEvent->io >> method	178	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
149	with the following mandatory key-value pairs as arguments:	179	with the following mandatory key-value pairs as arguments:
150		180
151	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch	181	C<fh> is the Perl I<file handle> (or a naked file descriptor) to watch
		182	for events (AnyEvent might or might not keep a reference to this file
		183	handle). Note that only file handles pointing to things for which
		184	non-blocking operation makes sense are allowed. This includes sockets,
		185	most character devices, pipes, fifos and so on, but not for example files
		186	or block devices.
		187
152	for events. C<poll> must be a string that is either C<r> or C<w>,	188	C<poll> must be a string that is either C<r> or C<w>, which creates a
153	which creates a watcher waiting for "r"eadable or "w"ritable events,	189	watcher waiting for "r"eadable or "w"ritable events, respectively.
		190
154	respectively. C<cb> is the callback to invoke each time the file handle	191	C<cb> is the callback to invoke each time the file handle becomes ready.
155	becomes ready.
156		192
157	Although the callback might get passed parameters, their value and	193	Although the callback might get passed parameters, their value and
158	presence is undefined and you cannot rely on them. Portable AnyEvent	194	presence is undefined and you cannot rely on them. Portable AnyEvent
159	callbacks cannot use arguments passed to I/O watcher callbacks.	195	callbacks cannot use arguments passed to I/O watcher callbacks.
160		196
…		…
164		200
165	Some event loops issue spurious readyness notifications, so you should	201	Some event loops issue spurious readyness notifications, so you should
166	always use non-blocking calls when reading/writing from/to your file	202	always use non-blocking calls when reading/writing from/to your file
167	handles.	203	handles.
168		204
169	Example:
170
171	# wait for readability of STDIN, then read a line and disable the watcher	205	Example: wait for readability of STDIN, then read a line and disable the
		206	watcher.
		207
172	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	208	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
173	chomp (my $input = <STDIN>);	209	chomp (my $input = <STDIN>);
174	warn "read: $input\n";	210	warn "read: $input\n";
175	undef $w;	211	undef $w;
176	});	212	});
…		…
186		222
187	Although the callback might get passed parameters, their value and	223	Although the callback might get passed parameters, their value and
188	presence is undefined and you cannot rely on them. Portable AnyEvent	224	presence is undefined and you cannot rely on them. Portable AnyEvent
189	callbacks cannot use arguments passed to time watcher callbacks.	225	callbacks cannot use arguments passed to time watcher callbacks.
190		226
191	The timer callback will be invoked at most once: if you want a repeating	227	The callback will normally be invoked once only. If you specify another
192	timer you have to create a new watcher (this is a limitation by both Tk	228	parameter, C<interval>, as a strictly positive number (> 0), then the
193	and Glib).	229	callback will be invoked regularly at that interval (in fractional
		230	seconds) after the first invocation. If C<interval> is specified with a
		231	false value, then it is treated as if it were missing.
194		232
195	Example:	233	The callback will be rescheduled before invoking the callback, but no
		234	attempt is done to avoid timer drift in most backends, so the interval is
		235	only approximate.
196		236
197	# fire an event after 7.7 seconds	237	Example: fire an event after 7.7 seconds.
		238
198	my $w = AnyEvent->timer (after => 7.7, cb => sub {	239	my $w = AnyEvent->timer (after => 7.7, cb => sub {
199	warn "timeout\n";	240	warn "timeout\n";
200	});	241	});
201		242
202	# to cancel the timer:	243	# to cancel the timer:
203	undef $w;	244	undef $w;
204		245
205	Example 2:
206
207	# fire an event after 0.5 seconds, then roughly every second	246	Example 2: fire an event after 0.5 seconds, then roughly every second.
208	my $w;
209		247
210	my $cb = sub {
211	# cancel the old timer while creating a new one
212	$w = AnyEvent->timer (after => 1, cb => $cb);	248	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		249	warn "timeout\n";
213	};	250	};
214
215	# start the "loop" by creating the first watcher
216	$w = AnyEvent->timer (after => 0.5, cb => $cb);
217		251
218	=head3 TIMING ISSUES	252	=head3 TIMING ISSUES
219		253
220	There are two ways to handle timers: based on real time (relative, "fire	254	There are two ways to handle timers: based on real time (relative, "fire
221	in 10 seconds") and based on wallclock time (absolute, "fire at 12	255	in 10 seconds") and based on wallclock time (absolute, "fire at 12
…		…
243		277
244	This returns the "current wallclock time" as a fractional number of	278	This returns the "current wallclock time" as a fractional number of
245	seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>	279	seconds since the Epoch (the same thing as C<time> or C<Time::HiRes::time>
246	return, and the result is guaranteed to be compatible with those).	280	return, and the result is guaranteed to be compatible with those).
247		281
248	It progresses independently of any event loop processing.	282	It progresses independently of any event loop processing, i.e. each call
249		283	will check the system clock, which usually gets updated frequently.
250	In almost all cases (in all cases if you don't care), this is the function
251	to call when you want to know the current time.
252		284
253	=item AnyEvent->now	285	=item AnyEvent->now
254		286
255	This also returns the "current wallclock time", but unlike C<time>, above,	287	This also returns the "current wallclock time", but unlike C<time>, above,
256	this value might change only once per event loop iteration, depending on	288	this value might change only once per event loop iteration, depending on
257	the event loop (most return the same time as C<time>, above). This is the	289	the event loop (most return the same time as C<time>, above). This is the
258	time that AnyEvent timers get scheduled against.	290	time that AnyEvent's timers get scheduled against.
		291
		292	I<In almost all cases (in all cases if you don't care), this is the
		293	function to call when you want to know the current time.>
		294
		295	This function is also often faster then C<< AnyEvent->time >>, and
		296	thus the preferred method if you want some timestamp (for example,
		297	L<AnyEvent::Handle> uses this to update it's activity timeouts).
		298
		299	The rest of this section is only of relevance if you try to be very exact
		300	with your timing, you can skip it without bad conscience.
259		301
260	For a practical example of when these times differ, consider L<Event::Lib>	302	For a practical example of when these times differ, consider L<Event::Lib>
261	and L<EV> and the following set-up:	303	and L<EV> and the following set-up:
262		304
263	The event loop is running and has just invoked one of your callback at	305	The event loop is running and has just invoked one of your callback at
…		…
268		310
269	With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will	311	With L<Event::Lib>, C<< AnyEvent->time >> and C<< AnyEvent->now >> will
270	both return C<501>, because that is the current time, and the timer will	312	both return C<501>, because that is the current time, and the timer will
271	be scheduled to fire at time=504 (C<501> + C<3>).	313	be scheduled to fire at time=504 (C<501> + C<3>).
272		314
273	With L<EV>m C<< AnyEvent->time >> returns C<501> (as that is the current	315	With L<EV>, C<< AnyEvent->time >> returns C<501> (as that is the current
274	time), but C<< AnyEvent->now >> returns C<500>, as that is the time the	316	time), but C<< AnyEvent->now >> returns C<500>, as that is the time the
275	last event processing phase started. With L<EV>, your timer gets scheduled	317	last event processing phase started. With L<EV>, your timer gets scheduled
276	to run at time=503 (C<500> + C<3>).	318	to run at time=503 (C<500> + C<3>).
277		319
278	In one sense, L<Event::Lib> is more exact, as it uses the current time	320	In one sense, L<Event::Lib> is more exact, as it uses the current time
279	regardless of any delays introduced by event processing. However, most	321	regardless of any delays introduced by event processing. However, most
280	callbacks do not expect large delays in processing, so this causes a	322	callbacks do not expect large delays in processing, so this causes a
281	higher drift (and a lot more syscalls to get the current time).	323	higher drift (and a lot more system calls to get the current time).
282		324
283	In another sense, L<EV> is more exact, as your timer will be scheduled at	325	In another sense, L<EV> is more exact, as your timer will be scheduled at
284	the same time, regardless of how long event processing actually took.	326	the same time, regardless of how long event processing actually took.
285		327
286	In either case, if you care (and in most cases, you don't), then you	328	In either case, if you care (and in most cases, you don't), then you
287	can get whatever behaviour you want with any event loop, by taking the	329	can get whatever behaviour you want with any event loop, by taking the
288	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into	330	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
289	account.	331	account.
290		332
		333	=item AnyEvent->now_update
		334
		335	Some event loops (such as L<EV> or L<AnyEvent::Impl::Perl>) cache
		336	the current time for each loop iteration (see the discussion of L<<
		337	AnyEvent->now >>, above).
		338
		339	When a callback runs for a long time (or when the process sleeps), then
		340	this "current" time will differ substantially from the real time, which
		341	might affect timers and time-outs.
		342
		343	When this is the case, you can call this method, which will update the
		344	event loop's idea of "current time".
		345
		346	Note that updating the time I<might> cause some events to be handled.
		347
291	=back	348	=back
292		349
293	=head2 SIGNAL WATCHERS	350	=head2 SIGNAL WATCHERS
294		351
295	You can watch for signals using a signal watcher, C<signal> is the signal	352	You can watch for signals using a signal watcher, C<signal> is the signal
296	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to	353	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
297	be invoked whenever a signal occurs.	354	callback to be invoked whenever a signal occurs.
298		355
299	Although the callback might get passed parameters, their value and	356	Although the callback might get passed parameters, their value and
300	presence is undefined and you cannot rely on them. Portable AnyEvent	357	presence is undefined and you cannot rely on them. Portable AnyEvent
301	callbacks cannot use arguments passed to signal watcher callbacks.	358	callbacks cannot use arguments passed to signal watcher callbacks.
302		359
…		…
304	invocation, and callback invocation will be synchronous. Synchronous means	361	invocation, and callback invocation will be synchronous. Synchronous means
305	that it might take a while until the signal gets handled by the process,	362	that it might take a while until the signal gets handled by the process,
306	but it is guaranteed not to interrupt any other callbacks.	363	but it is guaranteed not to interrupt any other callbacks.
307		364
308	The main advantage of using these watchers is that you can share a signal	365	The main advantage of using these watchers is that you can share a signal
309	between multiple watchers.	366	between multiple watchers, and AnyEvent will ensure that signals will not
		367	interrupt your program at bad times.
310		368
311	This watcher might use C<%SIG>, so programs overwriting those signals	369	This watcher might use C<%SIG> (depending on the event loop used),
312	directly will likely not work correctly.	370	so programs overwriting those signals directly will likely not work
		371	correctly.
		372
		373	Also note that many event loops (e.g. Glib, Tk, Qt, IO::Async) do not
		374	support attaching callbacks to signals, which is a pity, as you cannot do
		375	race-free signal handling in perl. AnyEvent will try to do it's best, but
		376	in some cases, signals will be delayed. The maximum time a signal might
		377	be delayed is specified in C<$AnyEvent::MAX_SIGNAL_LATENCY> (default: 10
		378	seconds). This variable can be changed only before the first signal
		379	watcher is created, and should be left alone otherwise. Higher values
		380	will cause fewer spurious wake-ups, which is better for power and CPU
		381	saving. All these problems can be avoided by installing the optional
		382	L<Async::Interrupt> module.
313		383
314	Example: exit on SIGINT	384	Example: exit on SIGINT
315		385
316	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	386	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
317		387
318	=head2 CHILD PROCESS WATCHERS	388	=head2 CHILD PROCESS WATCHERS
319		389
320	You can also watch on a child process exit and catch its exit status.	390	You can also watch on a child process exit and catch its exit status.
321		391
322	The child process is specified by the C<pid> argument (if set to C<0>, it	392	The child process is specified by the C<pid> argument (if set to C<0>, it
323	watches for any child process exit). The watcher will trigger as often	393	watches for any child process exit). The watcher will triggered only when
324	as status change for the child are received. This works by installing a	394	the child process has finished and an exit status is available, not on
325	signal handler for C<SIGCHLD>. The callback will be called with the pid	395	any trace events (stopped/continued).
326	and exit status (as returned by waitpid), so unlike other watcher types,	396
327	you I<can> rely on child watcher callback arguments.	397	The callback will be called with the pid and exit status (as returned by
		398	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		399	callback arguments.
		400
		401	This watcher type works by installing a signal handler for C<SIGCHLD>,
		402	and since it cannot be shared, nothing else should use SIGCHLD or reap
		403	random child processes (waiting for specific child processes, e.g. inside
		404	C<system>, is just fine).
328		405
329	There is a slight catch to child watchers, however: you usually start them	406	There is a slight catch to child watchers, however: you usually start them
330	I<after> the child process was created, and this means the process could	407	I<after> the child process was created, and this means the process could
331	have exited already (and no SIGCHLD will be sent anymore).	408	have exited already (and no SIGCHLD will be sent anymore).
332		409
333	Not all event models handle this correctly (POE doesn't), but even for	410	Not all event models handle this correctly (neither POE nor IO::Async do,
		411	see their AnyEvent::Impl manpages for details), but even for event models
334	event models that I<do> handle this correctly, they usually need to be	412	that I<do> handle this correctly, they usually need to be loaded before
335	loaded before the process exits (i.e. before you fork in the first place).	413	the process exits (i.e. before you fork in the first place). AnyEvent's
		414	pure perl event loop handles all cases correctly regardless of when you
		415	start the watcher.
336		416
337	This means you cannot create a child watcher as the very first thing in an	417	This means you cannot create a child watcher as the very first
338	AnyEvent program, you I<have> to create at least one watcher before you	418	thing in an AnyEvent program, you I<have> to create at least one
339	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).	419	watcher before you C<fork> the child (alternatively, you can call
		420	C<AnyEvent::detect>).
		421
		422	As most event loops do not support waiting for child events, they will be
		423	emulated by AnyEvent in most cases, in which the latency and race problems
		424	mentioned in the description of signal watchers apply.
340		425
341	Example: fork a process and wait for it	426	Example: fork a process and wait for it
342		427
343	my $done = AnyEvent->condvar;	428	my $done = AnyEvent->condvar;
344		429
345	my $pid = fork or exit 5;	430	my $pid = fork or exit 5;
346		431
347	my $w = AnyEvent->child (	432	my $w = AnyEvent->child (
348	pid => $pid,	433	pid => $pid,
349	cb => sub {	434	cb => sub {
350	my ($pid, $status) = @_;	435	my ($pid, $status) = @_;
351	warn "pid $pid exited with status $status";	436	warn "pid $pid exited with status $status";
352	$done->send;	437	$done->send;
353	},	438	},
354	);	439	);
355		440
356	# do something else, then wait for process exit	441	# do something else, then wait for process exit
357	$done->recv;	442	$done->recv;
		443
		444	=head2 IDLE WATCHERS
		445
		446	Sometimes there is a need to do something, but it is not so important
		447	to do it instantly, but only when there is nothing better to do. This
		448	"nothing better to do" is usually defined to be "no other events need
		449	attention by the event loop".
		450
		451	Idle watchers ideally get invoked when the event loop has nothing
		452	better to do, just before it would block the process to wait for new
		453	events. Instead of blocking, the idle watcher is invoked.
		454
		455	Most event loops unfortunately do not really support idle watchers (only
		456	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		457	will simply call the callback "from time to time".
		458
		459	Example: read lines from STDIN, but only process them when the
		460	program is otherwise idle:
		461
		462	my @lines; # read data
		463	my $idle_w;
		464	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		465	push @lines, scalar <STDIN>;
		466
		467	# start an idle watcher, if not already done
		468	$idle_w ||= AnyEvent->idle (cb => sub {
		469	# handle only one line, when there are lines left
		470	if (my $line = shift @lines) {
		471	print "handled when idle: $line";
		472	} else {
		473	# otherwise disable the idle watcher again
		474	undef $idle_w;
		475	}
		476	});
		477	});
358		478
359	=head2 CONDITION VARIABLES	479	=head2 CONDITION VARIABLES
360		480
361	If you are familiar with some event loops you will know that all of them	481	If you are familiar with some event loops you will know that all of them
362	require you to run some blocking "loop", "run" or similar function that	482	require you to run some blocking "loop", "run" or similar function that
363	will actively watch for new events and call your callbacks.	483	will actively watch for new events and call your callbacks.
364		484
365	AnyEvent is different, it expects somebody else to run the event loop and	485	AnyEvent is slightly different: it expects somebody else to run the event
366	will only block when necessary (usually when told by the user).	486	loop and will only block when necessary (usually when told by the user).
367		487
368	The instrument to do that is called a "condition variable", so called	488	The instrument to do that is called a "condition variable", so called
369	because they represent a condition that must become true.	489	because they represent a condition that must become true.
		490
		491	Now is probably a good time to look at the examples further below.
370		492
371	Condition variables can be created by calling the C<< AnyEvent->condvar	493	Condition variables can be created by calling the C<< AnyEvent->condvar
372	>> method, usually without arguments. The only argument pair allowed is	494	>> method, usually without arguments. The only argument pair allowed is
373	C<cb>, which specifies a callback to be called when the condition variable	495	C<cb>, which specifies a callback to be called when the condition variable
374	becomes true.	496	becomes true, with the condition variable as the first argument (but not
		497	the results).
375		498
376	After creation, the condition variable is "false" until it becomes "true"	499	After creation, the condition variable is "false" until it becomes "true"
377	by calling the C<send> method (or calling the condition variable as if it	500	by calling the C<send> method (or calling the condition variable as if it
378	were a callback, read about the caveats in the description for the C<<	501	were a callback, read about the caveats in the description for the C<<
379	->send >> method).	502	->send >> method).
…		…
425	after => 1,	548	after => 1,
426	cb => sub { $result_ready->send },	549	cb => sub { $result_ready->send },
427	);	550	);
428		551
429	# this "blocks" (while handling events) till the callback	552	# this "blocks" (while handling events) till the callback
430	# calls send	553	# calls -<send
431	$result_ready->recv;	554	$result_ready->recv;
432		555
433	Example: wait for a timer, but take advantage of the fact that	556	Example: wait for a timer, but take advantage of the fact that condition
434	condition variables are also code references.	557	variables are also callable directly.
435		558
436	my $done = AnyEvent->condvar;	559	my $done = AnyEvent->condvar;
437	my $delay = AnyEvent->timer (after => 5, cb => $done);	560	my $delay = AnyEvent->timer (after => 5, cb => $done);
438	$done->recv;	561	$done->recv;
		562
		563	Example: Imagine an API that returns a condvar and doesn't support
		564	callbacks. This is how you make a synchronous call, for example from
		565	the main program:
		566
		567	use AnyEvent::CouchDB;
		568
		569	...
		570
		571	my @info = $couchdb->info->recv;
		572
		573	And this is how you would just set a callback to be called whenever the
		574	results are available:
		575
		576	$couchdb->info->cb (sub {
		577	my @info = $_[0]->recv;
		578	});
439		579
440	=head3 METHODS FOR PRODUCERS	580	=head3 METHODS FOR PRODUCERS
441		581
442	These methods should only be used by the producing side, i.e. the	582	These methods should only be used by the producing side, i.e. the
443	code/module that eventually sends the signal. Note that it is also	583	code/module that eventually sends the signal. Note that it is also
…		…
456	immediately from within send.	596	immediately from within send.
457		597
458	Any arguments passed to the C<send> call will be returned by all	598	Any arguments passed to the C<send> call will be returned by all
459	future C<< ->recv >> calls.	599	future C<< ->recv >> calls.
460		600
461	Condition variables are overloaded so one can call them directly	601	Condition variables are overloaded so one can call them directly (as if
462	(as a code reference). Calling them directly is the same as calling	602	they were a code reference). Calling them directly is the same as calling
463	C<send>. Note, however, that many C-based event loops do not handle	603	C<send>.
464	overloading, so as tempting as it may be, passing a condition variable
465	instead of a callback does not work. Both the pure perl and EV loops
466	support overloading, however, as well as all functions that use perl to
467	invoke a callback (as in L<AnyEvent::Socket> and L<AnyEvent::DNS> for
468	example).
469		604
470	=item $cv->croak ($error)	605	=item $cv->croak ($error)
471		606
472	Similar to send, but causes all call's to C<< ->recv >> to invoke	607	Similar to send, but causes all call's to C<< ->recv >> to invoke
473	C<Carp::croak> with the given error message/object/scalar.	608	C<Carp::croak> with the given error message/object/scalar.
474		609
475	This can be used to signal any errors to the condition variable	610	This can be used to signal any errors to the condition variable
476	user/consumer.	611	user/consumer. Doing it this way instead of calling C<croak> directly
		612	delays the error detetcion, but has the overwhelmign advantage that it
		613	diagnoses the error at the place where the result is expected, and not
		614	deep in some event clalback without connection to the actual code causing
		615	the problem.
477		616
478	=item $cv->begin ([group callback])	617	=item $cv->begin ([group callback])
479		618
480	=item $cv->end	619	=item $cv->end
481
482	These two methods are EXPERIMENTAL and MIGHT CHANGE.
483		620
484	These two methods can be used to combine many transactions/events into	621	These two methods can be used to combine many transactions/events into
485	one. For example, a function that pings many hosts in parallel might want	622	one. For example, a function that pings many hosts in parallel might want
486	to use a condition variable for the whole process.	623	to use a condition variable for the whole process.
487		624
…		…
489	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end	626	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
490	>>, the (last) callback passed to C<begin> will be executed. That callback	627	>>, the (last) callback passed to C<begin> will be executed. That callback
491	is I<supposed> to call C<< ->send >>, but that is not required. If no	628	is I<supposed> to call C<< ->send >>, but that is not required. If no
492	callback was set, C<send> will be called without any arguments.	629	callback was set, C<send> will be called without any arguments.
493		630
494	Let's clarify this with the ping example:	631	You can think of C<< $cv->send >> giving you an OR condition (one call
		632	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		633	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		634
		635	Let's start with a simple example: you have two I/O watchers (for example,
		636	STDOUT and STDERR for a program), and you want to wait for both streams to
		637	close before activating a condvar:
		638
		639	my $cv = AnyEvent->condvar;
		640
		641	$cv->begin; # first watcher
		642	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		643	defined sysread $fh1, my $buf, 4096
		644	or $cv->end;
		645	});
		646
		647	$cv->begin; # second watcher
		648	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		649	defined sysread $fh2, my $buf, 4096
		650	or $cv->end;
		651	});
		652
		653	$cv->recv;
		654
		655	This works because for every event source (EOF on file handle), there is
		656	one call to C<begin>, so the condvar waits for all calls to C<end> before
		657	sending.
		658
		659	The ping example mentioned above is slightly more complicated, as the
		660	there are results to be passwd back, and the number of tasks that are
		661	begung can potentially be zero:
495		662
496	my $cv = AnyEvent->condvar;	663	my $cv = AnyEvent->condvar;
497		664
498	my %result;	665	my %result;
499	$cv->begin (sub { $cv->send (\%result) });	666	$cv->begin (sub { $cv->send (\%result) });
…		…
519	loop, which serves two important purposes: first, it sets the callback	686	loop, which serves two important purposes: first, it sets the callback
520	to be called once the counter reaches C<0>, and second, it ensures that	687	to be called once the counter reaches C<0>, and second, it ensures that
521	C<send> is called even when C<no> hosts are being pinged (the loop	688	C<send> is called even when C<no> hosts are being pinged (the loop
522	doesn't execute once).	689	doesn't execute once).
523		690
524	This is the general pattern when you "fan out" into multiple subrequests:	691	This is the general pattern when you "fan out" into multiple (but
525	use an outer C<begin>/C<end> pair to set the callback and ensure C<end>	692	potentially none) subrequests: use an outer C<begin>/C<end> pair to set
526	is called at least once, and then, for each subrequest you start, call	693	the callback and ensure C<end> is called at least once, and then, for each
527	C<begin> and for each subrequest you finish, call C<end>.	694	subrequest you start, call C<begin> and for each subrequest you finish,
		695	call C<end>.
528		696
529	=back	697	=back
530		698
531	=head3 METHODS FOR CONSUMERS	699	=head3 METHODS FOR CONSUMERS
532		700
…		…
548	function will call C<croak>.	716	function will call C<croak>.
549		717
550	In list context, all parameters passed to C<send> will be returned,	718	In list context, all parameters passed to C<send> will be returned,
551	in scalar context only the first one will be returned.	719	in scalar context only the first one will be returned.
552		720
		721	Note that doing a blocking wait in a callback is not supported by any
		722	event loop, that is, recursive invocation of a blocking C<< ->recv
		723	>> is not allowed, and the C<recv> call will C<croak> if such a
		724	condition is detected. This condition can be slightly loosened by using
		725	L<Coro::AnyEvent>, which allows you to do a blocking C<< ->recv >> from
		726	any thread that doesn't run the event loop itself.
		727
553	Not all event models support a blocking wait - some die in that case	728	Not all event models support a blocking wait - some die in that case
554	(programs might want to do that to stay interactive), so I<if you are	729	(programs might want to do that to stay interactive), so I<if you are
555	using this from a module, never require a blocking wait>, but let the	730	using this from a module, never require a blocking wait>. Instead, let the
556	caller decide whether the call will block or not (for example, by coupling	731	caller decide whether the call will block or not (for example, by coupling
557	condition variables with some kind of request results and supporting	732	condition variables with some kind of request results and supporting
558	callbacks so the caller knows that getting the result will not block,	733	callbacks so the caller knows that getting the result will not block,
559	while still supporting blocking waits if the caller so desires).	734	while still supporting blocking waits if the caller so desires).
560		735
561	Another reason I<never> to C<< ->recv >> in a module is that you cannot
562	sensibly have two C<< ->recv >>'s in parallel, as that would require
563	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
564	can supply.
565
566	The L<Coro> module, however, I<can> and I<does> supply coroutines and, in
567	fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe
568	versions and also integrates coroutines into AnyEvent, making blocking
569	C<< ->recv >> calls perfectly safe as long as they are done from another
570	coroutine (one that doesn't run the event loop).
571
572	You can ensure that C<< -recv >> never blocks by setting a callback and	736	You can ensure that C<< -recv >> never blocks by setting a callback and
573	only calling C<< ->recv >> from within that callback (or at a later	737	only calling C<< ->recv >> from within that callback (or at a later
574	time). This will work even when the event loop does not support blocking	738	time). This will work even when the event loop does not support blocking
575	waits otherwise.	739	waits otherwise.
576		740
577	=item $bool = $cv->ready	741	=item $bool = $cv->ready
578		742
579	Returns true when the condition is "true", i.e. whether C<send> or	743	Returns true when the condition is "true", i.e. whether C<send> or
580	C<croak> have been called.	744	C<croak> have been called.
581		745
582	=item $cb = $cv->cb ([new callback])	746	=item $cb = $cv->cb ($cb->($cv))
583		747
584	This is a mutator function that returns the callback set and optionally	748	This is a mutator function that returns the callback set and optionally
585	replaces it before doing so.	749	replaces it before doing so.
586		750
587	The callback will be called when the condition becomes "true", i.e. when	751	The callback will be called when the condition becomes "true", i.e. when
588	C<send> or C<croak> are called. Calling C<recv> inside the callback	752	C<send> or C<croak> are called, with the only argument being the condition
589	or at any later time is guaranteed not to block.	753	variable itself. Calling C<recv> inside the callback or at any later time
		754	is guaranteed not to block.
590		755
591	=back	756	=back
592		757
		758	=head1 SUPPORTED EVENT LOOPS/BACKENDS
		759
		760	The available backend classes are (every class has its own manpage):
		761
		762	=over 4
		763
		764	=item Backends that are autoprobed when no other event loop can be found.
		765
		766	EV is the preferred backend when no other event loop seems to be in
		767	use. If EV is not installed, then AnyEvent will try Event, and, failing
		768	that, will fall back to its own pure-perl implementation, which is
		769	available everywhere as it comes with AnyEvent itself.
		770
		771	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		772	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		773	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
		774
		775	=item Backends that are transparently being picked up when they are used.
		776
		777	These will be used when they are currently loaded when the first watcher
		778	is created, in which case it is assumed that the application is using
		779	them. This means that AnyEvent will automatically pick the right backend
		780	when the main program loads an event module before anything starts to
		781	create watchers. Nothing special needs to be done by the main program.
		782
		783	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		784	AnyEvent::Impl::Tk based on Tk, very broken.
		785	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		786	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		787
		788	=item Backends with special needs.
		789
		790	Qt requires the Qt::Application to be instantiated first, but will
		791	otherwise be picked up automatically. As long as the main program
		792	instantiates the application before any AnyEvent watchers are created,
		793	everything should just work.
		794
		795	AnyEvent::Impl::Qt based on Qt.
		796
		797	Support for IO::Async can only be partial, as it is too broken and
		798	architecturally limited to even support the AnyEvent API. It also
		799	is the only event loop that needs the loop to be set explicitly, so
		800	it can only be used by a main program knowing about AnyEvent. See
		801	L<AnyEvent::Impl::Async> for the gory details.
		802
		803	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
		804
		805	=item Event loops that are indirectly supported via other backends.
		806
		807	Some event loops can be supported via other modules:
		808
		809	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		810
		811	B<WxWidgets> has no support for watching file handles. However, you can
		812	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		813	polls 20 times per second, which was considered to be too horrible to even
		814	consider for AnyEvent.
		815
		816	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		817	backend, so it can be supported through POE.
		818
		819	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		820	load L<POE> when detecting them, in the hope that POE will pick them up,
		821	in which case everything will be automatic.
		822
		823	=back
		824
593	=head1 GLOBAL VARIABLES AND FUNCTIONS	825	=head1 GLOBAL VARIABLES AND FUNCTIONS
594		826
		827	These are not normally required to use AnyEvent, but can be useful to
		828	write AnyEvent extension modules.
		829
595	=over 4	830	=over 4
596		831
597	=item $AnyEvent::MODEL	832	=item $AnyEvent::MODEL
598		833
599	Contains C<undef> until the first watcher is being created. Then it	834	Contains C<undef> until the first watcher is being created, before the
		835	backend has been autodetected.
		836
600	contains the event model that is being used, which is the name of the	837	Afterwards it contains the event model that is being used, which is the
601	Perl class implementing the model. This class is usually one of the	838	name of the Perl class implementing the model. This class is usually one
602	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	839	of the C<AnyEvent::Impl:xxx> modules, but can be any other class in the
603	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	840	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
604		841	will be C<urxvt::anyevent>).
605	The known classes so far are:
606
607	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
608	AnyEvent::Impl::Event based on Event, second best choice.
609	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
610	AnyEvent::Impl::Glib based on Glib, third-best choice.
611	AnyEvent::Impl::Tk based on Tk, very bad choice.
612	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
613	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
614	AnyEvent::Impl::POE based on POE, not generic enough for full support.
615
616	There is no support for WxWidgets, as WxWidgets has no support for
617	watching file handles. However, you can use WxWidgets through the
618	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
619	second, which was considered to be too horrible to even consider for
620	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
621	it's adaptor.
622
623	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
624	autodetecting them.
625		842
626	=item AnyEvent::detect	843	=item AnyEvent::detect
627		844
628	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	845	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
629	if necessary. You should only call this function right before you would	846	if necessary. You should only call this function right before you would
630	have created an AnyEvent watcher anyway, that is, as late as possible at	847	have created an AnyEvent watcher anyway, that is, as late as possible at
631	runtime.	848	runtime, and not e.g. while initialising of your module.
		849
		850	If you need to do some initialisation before AnyEvent watchers are
		851	created, use C<post_detect>.
632		852
633	=item $guard = AnyEvent::post_detect { BLOCK }	853	=item $guard = AnyEvent::post_detect { BLOCK }
634		854
635	Arranges for the code block to be executed as soon as the event model is	855	Arranges for the code block to be executed as soon as the event model is
636	autodetected (or immediately if this has already happened).	856	autodetected (or immediately if this has already happened).
		857
		858	The block will be executed I<after> the actual backend has been detected
		859	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		860	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		861	other initialisations - see the sources of L<AnyEvent::Strict> or
		862	L<AnyEvent::AIO> to see how this is used.
		863
		864	The most common usage is to create some global watchers, without forcing
		865	event module detection too early, for example, L<AnyEvent::AIO> creates
		866	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		867	avoid autodetecting the event module at load time.
637		868
638	If called in scalar or list context, then it creates and returns an object	869	If called in scalar or list context, then it creates and returns an object
639	that automatically removes the callback again when it is destroyed. See	870	that automatically removes the callback again when it is destroyed. See
640	L<Coro::BDB> for a case where this is useful.	871	L<Coro::BDB> for a case where this is useful.
641		872
…		…
644	If there are any code references in this array (you can C<push> to it	875	If there are any code references in this array (you can C<push> to it
645	before or after loading AnyEvent), then they will called directly after	876	before or after loading AnyEvent), then they will called directly after
646	the event loop has been chosen.	877	the event loop has been chosen.
647		878
648	You should check C<$AnyEvent::MODEL> before adding to this array, though:	879	You should check C<$AnyEvent::MODEL> before adding to this array, though:
649	if it contains a true value then the event loop has already been detected,	880	if it is defined then the event loop has already been detected, and the
650	and the array will be ignored.	881	array will be ignored.
651		882
652	Best use C<AnyEvent::post_detect { BLOCK }> instead.	883	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		884	it,as it takes care of these details.
		885
		886	This variable is mainly useful for modules that can do something useful
		887	when AnyEvent is used and thus want to know when it is initialised, but do
		888	not need to even load it by default. This array provides the means to hook
		889	into AnyEvent passively, without loading it.
653		890
654	=back	891	=back
655		892
656	=head1 WHAT TO DO IN A MODULE	893	=head1 WHAT TO DO IN A MODULE
657		894
…		…
712		949
713		950
714	=head1 OTHER MODULES	951	=head1 OTHER MODULES
715		952
716	The following is a non-exhaustive list of additional modules that use	953	The following is a non-exhaustive list of additional modules that use
717	AnyEvent and can therefore be mixed easily with other AnyEvent modules	954	AnyEvent as a client and can therefore be mixed easily with other AnyEvent
718	in the same program. Some of the modules come with AnyEvent, some are	955	modules and other event loops in the same program. Some of the modules
719	available via CPAN.	956	come with AnyEvent, most are available via CPAN.
720		957
721	=over 4	958	=over 4
722		959
723	=item L<AnyEvent::Util>	960	=item L<AnyEvent::Util>
724		961
725	Contains various utility functions that replace often-used but blocking	962	Contains various utility functions that replace often-used but blocking
726	functions such as C<inet_aton> by event-/callback-based versions.	963	functions such as C<inet_aton> by event-/callback-based versions.
727
728	=item L<AnyEvent::Handle>
729
730	Provide read and write buffers and manages watchers for reads and writes.
731		964
732	=item L<AnyEvent::Socket>	965	=item L<AnyEvent::Socket>
733		966
734	Provides various utility functions for (internet protocol) sockets,	967	Provides various utility functions for (internet protocol) sockets,
735	addresses and name resolution. Also functions to create non-blocking tcp	968	addresses and name resolution. Also functions to create non-blocking tcp
736	connections or tcp servers, with IPv6 and SRV record support and more.	969	connections or tcp servers, with IPv6 and SRV record support and more.
737		970
		971	=item L<AnyEvent::Handle>
		972
		973	Provide read and write buffers, manages watchers for reads and writes,
		974	supports raw and formatted I/O, I/O queued and fully transparent and
		975	non-blocking SSL/TLS (via L<AnyEvent::TLS>.
		976
738	=item L<AnyEvent::DNS>	977	=item L<AnyEvent::DNS>
739		978
740	Provides rich asynchronous DNS resolver capabilities.	979	Provides rich asynchronous DNS resolver capabilities.
741		980
		981	=item L<AnyEvent::HTTP>
		982
		983	A simple-to-use HTTP library that is capable of making a lot of concurrent
		984	HTTP requests.
		985
742	=item L<AnyEvent::HTTPD>	986	=item L<AnyEvent::HTTPD>
743		987
744	Provides a simple web application server framework.	988	Provides a simple web application server framework.
745		989
746	=item L<AnyEvent::FastPing>	990	=item L<AnyEvent::FastPing>
747		991
748	The fastest ping in the west.	992	The fastest ping in the west.
749		993
		994	=item L<AnyEvent::DBI>
		995
		996	Executes L<DBI> requests asynchronously in a proxy process.
		997
		998	=item L<AnyEvent::AIO>
		999
		1000	Truly asynchronous I/O, should be in the toolbox of every event
		1001	programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
		1002	together.
		1003
		1004	=item L<AnyEvent::BDB>
		1005
		1006	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
		1007	L<BDB> and AnyEvent together.
		1008
		1009	=item L<AnyEvent::GPSD>
		1010
		1011	A non-blocking interface to gpsd, a daemon delivering GPS information.
		1012
750	=item L<Net::IRC3>	1013	=item L<AnyEvent::IRC>
751		1014
752	AnyEvent based IRC client module family.	1015	AnyEvent based IRC client module family (replacing the older Net::IRC3).
753		1016
754	=item L<Net::XMPP2>	1017	=item L<AnyEvent::XMPP>
755		1018
756	AnyEvent based XMPP (Jabber protocol) module family.	1019	AnyEvent based XMPP (Jabber protocol) module family (replacing the older
		1020	Net::XMPP2>.
		1021
		1022	=item L<AnyEvent::IGS>
		1023
		1024	A non-blocking interface to the Internet Go Server protocol (used by
		1025	L<App::IGS>).
757		1026
758	=item L<Net::FCP>	1027	=item L<Net::FCP>
759		1028
760	AnyEvent-based implementation of the Freenet Client Protocol, birthplace	1029	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
761	of AnyEvent.	1030	of AnyEvent.
…		…
766		1035
767	=item L<Coro>	1036	=item L<Coro>
768		1037
769	Has special support for AnyEvent via L<Coro::AnyEvent>.	1038	Has special support for AnyEvent via L<Coro::AnyEvent>.
770		1039
771	=item L<AnyEvent::AIO>, L<IO::AIO>
772
773	Truly asynchronous I/O, should be in the toolbox of every event
774	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
775	together.
776
777	=item L<AnyEvent::BDB>, L<BDB>
778
779	Truly asynchronous Berkeley DB access. AnyEvent::AIO transparently fuses
780	IO::AIO and AnyEvent together.
781
782	=item L<IO::Lambda>
783
784	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
785
786	=back	1040	=back
787		1041
788	=cut	1042	=cut
789		1043
790	package AnyEvent;	1044	package AnyEvent;
791		1045
		1046	# basically a tuned-down version of common::sense
		1047	sub common_sense {
792	no warnings;	1048	# no warnings
793	use strict;	1049	${^WARNING_BITS} ^= ${^WARNING_BITS};
		1050	# use strict vars subs
		1051	$^H |= 0x00000600;
		1052	}
794		1053
		1054	BEGIN { AnyEvent::common_sense }
		1055
795	use Carp;	1056	use Carp ();
796		1057
797	our $VERSION = '4.05';	1058	our $VERSION = 4.83;
798	our $MODEL;	1059	our $MODEL;
799		1060
800	our $AUTOLOAD;	1061	our $AUTOLOAD;
801	our @ISA;	1062	our @ISA;
802		1063
803	our @REGISTRY;	1064	our @REGISTRY;
804		1065
805	our $WIN32;	1066	our $WIN32;
806		1067
		1068	our $VERBOSE;
		1069
807	BEGIN {	1070	BEGIN {
808	my $win32 = ! ! ($^O =~ /mswin32/i);	1071	eval "sub WIN32(){ " . (($^O =~ /mswin32/i)*1) ." }";
809	eval "sub WIN32(){ $win32 }";	1072	eval "sub TAINT(){ " . (${^TAINT}*1) . " }";
810	}
811		1073
		1074	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1075	if ${^TAINT};
		1076
812	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;	1077	$VERBOSE = $ENV{PERL_ANYEVENT_VERBOSE}*1;
		1078
		1079	}
		1080
		1081	our $MAX_SIGNAL_LATENCY = 10;
813		1082
814	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred	1083	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
815		1084
816	{	1085	{
817	my $idx;	1086	my $idx;
…		…
825	[Event:: => AnyEvent::Impl::Event::],	1094	[Event:: => AnyEvent::Impl::Event::],
826	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1095	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
827	# everything below here will not be autoprobed	1096	# everything below here will not be autoprobed
828	# as the pureperl backend should work everywhere	1097	# as the pureperl backend should work everywhere
829	# and is usually faster	1098	# and is usually faster
830	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
831	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers	1099	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers
832	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy	1100	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		1101	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
833	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program	1102	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
834	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza	1103	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
835	[Wx:: => AnyEvent::Impl::POE::],	1104	[Wx:: => AnyEvent::Impl::POE::],
836	[Prima:: => AnyEvent::Impl::POE::],	1105	[Prima:: => AnyEvent::Impl::POE::],
		1106	# IO::Async is just too broken - we would need workarounds for its
		1107	# byzantine signal and broken child handling, among others.
		1108	# IO::Async is rather hard to detect, as it doesn't have any
		1109	# obvious default class.
		1110	# [IO::Async:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1111	# [IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1112	# [IO::Async::Notifier:: => AnyEvent::Impl::IOAsync::], # requires special main program
837	);	1113	);
838		1114
839	our %method = map +($_ => 1), qw(io timer time now signal child condvar one_event DESTROY);	1115	our %method = map +($_ => 1),
		1116	qw(io timer time now now_update signal child idle condvar one_event DESTROY);
840		1117
841	our @post_detect;	1118	our @post_detect;
842		1119
843	sub post_detect(&) {	1120	sub post_detect(&) {
844	my ($cb) = @_;	1121	my ($cb) = @_;
…		…
849	1	1126	1
850	} else {	1127	} else {
851	push @post_detect, $cb;	1128	push @post_detect, $cb;
852		1129
853	defined wantarray	1130	defined wantarray
854	? bless \$cb, "AnyEvent::Util::PostDetect"	1131	? bless \$cb, "AnyEvent::Util::postdetect"
855	: ()	1132	: ()
856	}	1133	}
857	}	1134	}
858		1135
859	sub AnyEvent::Util::PostDetect::DESTROY {	1136	sub AnyEvent::Util::postdetect::DESTROY {
860	@post_detect = grep $_ != ${$_[0]}, @post_detect;	1137	@post_detect = grep $_ != ${$_[0]}, @post_detect;
861	}	1138	}
862		1139
863	sub detect() {	1140	sub detect() {
864	unless ($MODEL) {	1141	unless ($MODEL) {
865	no strict 'refs';
866	local $SIG{__DIE__};	1142	local $SIG{__DIE__};
867		1143
868	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	1144	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
869	my $model = "AnyEvent::Impl::$1";	1145	my $model = "AnyEvent::Impl::$1";
870	if (eval "require $model") {	1146	if (eval "require $model") {
871	$MODEL = $model;	1147	$MODEL = $model;
872	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	1148	warn "AnyEvent: loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.\n" if $VERBOSE >= 2;
873	} else {	1149	} else {
874	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;	1150	warn "AnyEvent: unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@" if $VERBOSE;
875	}	1151	}
876	}	1152	}
877		1153
878	# check for already loaded models	1154	# check for already loaded models
879	unless ($MODEL) {	1155	unless ($MODEL) {
880	for (@REGISTRY, @models) {	1156	for (@REGISTRY, @models) {
881	my ($package, $model) = @$_;	1157	my ($package, $model) = @$_;
882	if (${"$package\::VERSION"} > 0) {	1158	if (${"$package\::VERSION"} > 0) {
883	if (eval "require $model") {	1159	if (eval "require $model") {
884	$MODEL = $model;	1160	$MODEL = $model;
885	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;	1161	warn "AnyEvent: autodetected model '$model', using it.\n" if $VERBOSE >= 2;
886	last;	1162	last;
887	}	1163	}
888	}	1164	}
889	}	1165	}
890		1166
…		…
895	my ($package, $model) = @$_;	1171	my ($package, $model) = @$_;
896	if (eval "require $package"	1172	if (eval "require $package"
897	and ${"$package\::VERSION"} > 0	1173	and ${"$package\::VERSION"} > 0
898	and eval "require $model") {	1174	and eval "require $model") {
899	$MODEL = $model;	1175	$MODEL = $model;
900	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;	1176	warn "AnyEvent: autoprobed model '$model', using it.\n" if $VERBOSE >= 2;
901	last;	1177	last;
902	}	1178	}
903	}	1179	}
904		1180
905	$MODEL	1181	$MODEL
906	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.";	1182	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.\n";
907	}	1183	}
908	}	1184	}
909		1185
		1186	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		1187
910	unshift @ISA, $MODEL;	1188	unshift @ISA, $MODEL;
911	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	1189
		1190	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
912		1191
913	(shift @post_detect)->() while @post_detect;	1192	(shift @post_detect)->() while @post_detect;
914	}	1193	}
915		1194
916	$MODEL	1195	$MODEL
…		…
918		1197
919	sub AUTOLOAD {	1198	sub AUTOLOAD {
920	(my $func = $AUTOLOAD) =~ s/.*://;	1199	(my $func = $AUTOLOAD) =~ s/.*://;
921		1200
922	$method{$func}	1201	$method{$func}
923	or croak "$func: not a valid method for AnyEvent objects";	1202	or Carp::croak "$func: not a valid method for AnyEvent objects";
924		1203
925	detect unless $MODEL;	1204	detect unless $MODEL;
926		1205
927	my $class = shift;	1206	my $class = shift;
928	$class->$func (@_);	1207	$class->$func (@_);
929	}	1208	}
930		1209
		1210	# utility function to dup a filehandle. this is used by many backends
		1211	# to support binding more than one watcher per filehandle (they usually
		1212	# allow only one watcher per fd, so we dup it to get a different one).
		1213	sub _dupfh($$;$$) {
		1214	my ($poll, $fh, $r, $w) = @_;
		1215
		1216	# cygwin requires the fh mode to be matching, unix doesn't
		1217	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1218
		1219	open my $fh2, $mode, $fh
		1220	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1221
		1222	# we assume CLOEXEC is already set by perl in all important cases
		1223
		1224	($fh2, $rw)
		1225	}
		1226
931	package AnyEvent::Base;	1227	package AnyEvent::Base;
932		1228
933	# default implementation for now and time	1229	# default implementations for many methods
934		1230
935	use Time::HiRes ();	1231	sub _time {
		1232	# probe for availability of Time::HiRes
		1233	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1234	warn "AnyEvent: using Time::HiRes for sub-second timing accuracy.\n" if $VERBOSE >= 8;
		1235	*_time = \&Time::HiRes::time;
		1236	# if (eval "use POSIX (); (POSIX::times())...
		1237	} else {
		1238	warn "AnyEvent: using built-in time(), WARNING, no sub-second resolution!\n" if $VERBOSE;
		1239	*_time = sub { time }; # epic fail
		1240	}
936		1241
937	sub time { Time::HiRes::time }	1242	&_time
938	sub now { Time::HiRes::time }	1243	}
		1244
		1245	sub time { _time }
		1246	sub now { _time }
		1247	sub now_update { }
939		1248
940	# default implementation for ->condvar	1249	# default implementation for ->condvar
941		1250
942	sub condvar {	1251	sub condvar {
943	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, AnyEvent::CondVar::	1252	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
944	}	1253	}
945		1254
946	# default implementation for ->signal	1255	# default implementation for ->signal
947		1256
948	our %SIG_CB;	1257	our $HAVE_ASYNC_INTERRUPT;
		1258	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1259	our (%SIG_ASY, %SIG_ASY_W);
		1260	our ($SIG_COUNT, $SIG_TW);
949		1261
		1262	sub _signal_exec {
		1263	$HAVE_ASYNC_INTERRUPT
		1264	? $SIGPIPE_R->drain
		1265	: sysread $SIGPIPE_R, my $dummy, 9;
		1266
		1267	while (%SIG_EV) {
		1268	for (keys %SIG_EV) {
		1269	delete $SIG_EV{$_};
		1270	$_->() for values %{ $SIG_CB{$_} || {} };
		1271	}
		1272	}
		1273	}
		1274
950	sub signal {	1275	sub _signal {
951	my (undef, %arg) = @_;	1276	my (undef, %arg) = @_;
952		1277
953	my $signal = uc $arg{signal}	1278	my $signal = uc $arg{signal}
954	or Carp::croak "required option 'signal' is missing";	1279	or Carp::croak "required option 'signal' is missing";
955		1280
956	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1281	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1282
		1283	if ($HAVE_ASYNC_INTERRUPT) {
		1284	# async::interrupt
		1285
		1286	$SIG_ASY{$signal} ||= do {
		1287	my $asy = new Async::Interrupt
		1288	cb => sub { undef $SIG_EV{$signal} },
		1289	signal => $signal,
		1290	pipe => [$SIGPIPE_R->filenos],
		1291	;
		1292	$asy->pipe_autodrain (0);
		1293
		1294	$asy
		1295	};
		1296
		1297	} else {
		1298	# pure perl
		1299
957	$SIG{$signal} ||= sub {	1300	$SIG{$signal} ||= sub {
958	$_->() for values %{ $SIG_CB{$signal} || {} };	1301	local $!;
		1302	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1303	undef $SIG_EV{$signal};
		1304	};
		1305
		1306	# can't do signal processing without introducing races in pure perl,
		1307	# so limit the signal latency.
		1308	++$SIG_COUNT;
		1309	$SIG_TW ||= AnyEvent->timer (
		1310	after => $MAX_SIGNAL_LATENCY,
		1311	interval => $MAX_SIGNAL_LATENCY,
		1312	cb => sub { }, # just for the PERL_ASYNC_CHECK
		1313	);
959	};	1314	}
960		1315
961	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1316	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
962	}	1317	}
963		1318
		1319	sub signal {
		1320	# probe for availability of Async::Interrupt
		1321	if (!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT} && eval "use Async::Interrupt 0.6 (); 1") {
		1322	warn "AnyEvent: using Async::Interrupt for race-free signal handling.\n" if $VERBOSE >= 8;
		1323
		1324	$HAVE_ASYNC_INTERRUPT = 1;
		1325	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1326	$SIG_IO = AnyEvent->io (fh => $SIGPIPE_R->fileno, poll => "r", cb => \&_signal_exec);
		1327
		1328	} else {
		1329	warn "AnyEvent: using emulated perl signal handling with latency timer.\n" if $VERBOSE >= 8;
		1330
		1331	require Fcntl;
		1332
		1333	if (AnyEvent::WIN32) {
		1334	require AnyEvent::Util;
		1335
		1336	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1337	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R) if $SIGPIPE_R;
		1338	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W) if $SIGPIPE_W; # just in case
		1339	} else {
		1340	pipe $SIGPIPE_R, $SIGPIPE_W;
		1341	fcntl $SIGPIPE_R, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_R;
		1342	fcntl $SIGPIPE_W, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_W; # just in case
		1343
		1344	# not strictly required, as $^F is normally 2, but let's make sure...
		1345	fcntl $SIGPIPE_R, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1346	fcntl $SIGPIPE_W, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1347	}
		1348
		1349	$SIGPIPE_R
		1350	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1351
		1352	$SIG_IO = AnyEvent->io (fh => $SIGPIPE_R, poll => "r", cb => \&_signal_exec);
		1353	}
		1354
		1355	*signal = \&_signal;
		1356	&signal
		1357	}
		1358
964	sub AnyEvent::Base::Signal::DESTROY {	1359	sub AnyEvent::Base::signal::DESTROY {
965	my ($signal, $cb) = @{$_[0]};	1360	my ($signal, $cb) = @{$_[0]};
966		1361
		1362	undef $SIG_TW
		1363	unless --$SIG_COUNT;
		1364
967	delete $SIG_CB{$signal}{$cb};	1365	delete $SIG_CB{$signal}{$cb};
968		1366
969	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };	1367	# delete doesn't work with older perls - they then
		1368	# print weird messages, or just unconditionally exit
		1369	# instead of getting the default action.
		1370	undef $SIG{$signal}
		1371	unless keys %{ $SIG_CB{$signal} };
970	}	1372	}
971		1373
972	# default implementation for ->child	1374	# default implementation for ->child
973		1375
974	our %PID_CB;	1376	our %PID_CB;
975	our $CHLD_W;	1377	our $CHLD_W;
976	our $CHLD_DELAY_W;	1378	our $CHLD_DELAY_W;
977	our $PID_IDLE;
978	our $WNOHANG;	1379	our $WNOHANG;
979		1380
980	sub _child_wait {	1381	sub _sigchld {
981	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1382	while (0 < (my $pid = waitpid -1, $WNOHANG)) {
		1383	$_->($pid, $?)
982	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1384	for values %{ $PID_CB{$pid} || {} },
983	(values %{ $PID_CB{0} || {} });	1385	values %{ $PID_CB{0} || {} };
984	}	1386	}
985
986	undef $PID_IDLE;
987	}
988
989	sub _sigchld {
990	# make sure we deliver these changes "synchronous" with the event loop.
991	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {
992	undef $CHLD_DELAY_W;
993	&_child_wait;
994	});
995	}	1387	}
996		1388
997	sub child {	1389	sub child {
998	my (undef, %arg) = @_;	1390	my (undef, %arg) = @_;
999		1391
1000	defined (my $pid = $arg{pid} + 0)	1392	defined (my $pid = $arg{pid} + 0)
1001	or Carp::croak "required option 'pid' is missing";	1393	or Carp::croak "required option 'pid' is missing";
1002		1394
1003	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1395	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
1004		1396
1005	unless ($WNOHANG) {	1397	# WNOHANG is almost cetrainly 1 everywhere
		1398	$WNOHANG ||= $^O =~ /^(?:openbsd|netbsd|linux|freebsd|cygwin|MSWin32)$/
		1399	? 1
1006	$WNOHANG = eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;	1400	: eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
1007	}
1008		1401
1009	unless ($CHLD_W) {	1402	unless ($CHLD_W) {
1010	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1403	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
1011	# child could be a zombie already, so make at least one round	1404	# child could be a zombie already, so make at least one round
1012	&_sigchld;	1405	&_sigchld;
1013	}	1406	}
1014		1407
1015	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	1408	bless [$pid, $arg{cb}], "AnyEvent::Base::child"
1016	}	1409	}
1017		1410
1018	sub AnyEvent::Base::Child::DESTROY {	1411	sub AnyEvent::Base::child::DESTROY {
1019	my ($pid, $cb) = @{$_[0]};	1412	my ($pid, $cb) = @{$_[0]};
1020		1413
1021	delete $PID_CB{$pid}{$cb};	1414	delete $PID_CB{$pid}{$cb};
1022	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1415	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
1023		1416
1024	undef $CHLD_W unless keys %PID_CB;	1417	undef $CHLD_W unless keys %PID_CB;
1025	}	1418	}
1026		1419
		1420	# idle emulation is done by simply using a timer, regardless
		1421	# of whether the process is idle or not, and not letting
		1422	# the callback use more than 50% of the time.
		1423	sub idle {
		1424	my (undef, %arg) = @_;
		1425
		1426	my ($cb, $w, $rcb) = $arg{cb};
		1427
		1428	$rcb = sub {
		1429	if ($cb) {
		1430	$w = _time;
		1431	&$cb;
		1432	$w = _time - $w;
		1433
		1434	# never use more then 50% of the time for the idle watcher,
		1435	# within some limits
		1436	$w = 0.0001 if $w < 0.0001;
		1437	$w = 5 if $w > 5;
		1438
		1439	$w = AnyEvent->timer (after => $w, cb => $rcb);
		1440	} else {
		1441	# clean up...
		1442	undef $w;
		1443	undef $rcb;
		1444	}
		1445	};
		1446
		1447	$w = AnyEvent->timer (after => 0.05, cb => $rcb);
		1448
		1449	bless \\$cb, "AnyEvent::Base::idle"
		1450	}
		1451
		1452	sub AnyEvent::Base::idle::DESTROY {
		1453	undef $${$_[0]};
		1454	}
		1455
1027	package AnyEvent::CondVar;	1456	package AnyEvent::CondVar;
1028		1457
1029	our @ISA = AnyEvent::CondVar::Base::;	1458	our @ISA = AnyEvent::CondVar::Base::;
1030		1459
1031	package AnyEvent::CondVar::Base;	1460	package AnyEvent::CondVar::Base;
1032		1461
1033	use overload	1462	#use overload
1034	'&{}' => sub { my $self = shift; sub { $self->send (@_) } },	1463	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
1035	fallback => 1;	1464	# fallback => 1;
		1465
		1466	# save 300+ kilobytes by dirtily hardcoding overloading
		1467	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1468	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1469	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1470	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1471
		1472	our $WAITING;
1036		1473
1037	sub _send {	1474	sub _send {
1038	# nop	1475	# nop
1039	}	1476	}
1040		1477
…		…
1053	sub ready {	1490	sub ready {
1054	$_[0]{_ae_sent}	1491	$_[0]{_ae_sent}
1055	}	1492	}
1056		1493
1057	sub _wait {	1494	sub _wait {
		1495	$WAITING
		1496	and !$_[0]{_ae_sent}
		1497	and Carp::croak "AnyEvent::CondVar: recursive blocking wait detected";
		1498
		1499	local $WAITING = 1;
1058	AnyEvent->one_event while !$_[0]{_ae_sent};	1500	AnyEvent->one_event while !$_[0]{_ae_sent};
1059	}	1501	}
1060		1502
1061	sub recv {	1503	sub recv {
1062	$_[0]->_wait;	1504	$_[0]->_wait;
…		…
1081	}	1523	}
1082		1524
1083	# undocumented/compatibility with pre-3.4	1525	# undocumented/compatibility with pre-3.4
1084	*broadcast = \&send;	1526	*broadcast = \&send;
1085	*wait = \&_wait;	1527	*wait = \&_wait;
		1528
		1529	=head1 ERROR AND EXCEPTION HANDLING
		1530
		1531	In general, AnyEvent does not do any error handling - it relies on the
		1532	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1533	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1534	checking of all AnyEvent methods, however, which is highly useful during
		1535	development.
		1536
		1537	As for exception handling (i.e. runtime errors and exceptions thrown while
		1538	executing a callback), this is not only highly event-loop specific, but
		1539	also not in any way wrapped by this module, as this is the job of the main
		1540	program.
		1541
		1542	The pure perl event loop simply re-throws the exception (usually
		1543	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1544	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1545	so on.
		1546
		1547	=head1 ENVIRONMENT VARIABLES
		1548
		1549	The following environment variables are used by this module or its
		1550	submodules.
		1551
		1552	Note that AnyEvent will remove I<all> environment variables starting with
		1553	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		1554	enabled.
		1555
		1556	=over 4
		1557
		1558	=item C<PERL_ANYEVENT_VERBOSE>
		1559
		1560	By default, AnyEvent will be completely silent except in fatal
		1561	conditions. You can set this environment variable to make AnyEvent more
		1562	talkative.
		1563
		1564	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1565	conditions, such as not being able to load the event model specified by
		1566	C<PERL_ANYEVENT_MODEL>.
		1567
		1568	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1569	model it chooses.
		1570
		1571	When set to C<8> or higher, then AnyEvent will report extra information on
		1572	which optional modules it loads and how it implements certain features.
		1573
		1574	=item C<PERL_ANYEVENT_STRICT>
		1575
		1576	AnyEvent does not do much argument checking by default, as thorough
		1577	argument checking is very costly. Setting this variable to a true value
		1578	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1579	check the arguments passed to most method calls. If it finds any problems,
		1580	it will croak.
		1581
		1582	In other words, enables "strict" mode.
		1583
		1584	Unlike C<use strict> (or it's modern cousin, C<< use L<common::sense>
		1585	>>, it is definitely recommended to keep it off in production. Keeping
		1586	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		1587	can be very useful, however.
		1588
		1589	=item C<PERL_ANYEVENT_MODEL>
		1590
		1591	This can be used to specify the event model to be used by AnyEvent, before
		1592	auto detection and -probing kicks in. It must be a string consisting
		1593	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1594	and the resulting module name is loaded and if the load was successful,
		1595	used as event model. If it fails to load AnyEvent will proceed with
		1596	auto detection and -probing.
		1597
		1598	This functionality might change in future versions.
		1599
		1600	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1601	could start your program like this:
		1602
		1603	PERL_ANYEVENT_MODEL=Perl perl ...
		1604
		1605	=item C<PERL_ANYEVENT_PROTOCOLS>
		1606
		1607	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1608	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1609	of auto probing).
		1610
		1611	Must be set to a comma-separated list of protocols or address families,
		1612	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1613	used, and preference will be given to protocols mentioned earlier in the
		1614	list.
		1615
		1616	This variable can effectively be used for denial-of-service attacks
		1617	against local programs (e.g. when setuid), although the impact is likely
		1618	small, as the program has to handle conenction and other failures anyways.
		1619
		1620	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1621	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1622	- only support IPv4, never try to resolve or contact IPv6
		1623	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1624	IPv6, but prefer IPv6 over IPv4.
		1625
		1626	=item C<PERL_ANYEVENT_EDNS0>
		1627
		1628	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1629	for DNS. This extension is generally useful to reduce DNS traffic, but
		1630	some (broken) firewalls drop such DNS packets, which is why it is off by
		1631	default.
		1632
		1633	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1634	EDNS0 in its DNS requests.
		1635
		1636	=item C<PERL_ANYEVENT_MAX_FORKS>
		1637
		1638	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1639	will create in parallel.
		1640
		1641	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		1642
		1643	The default value for the C<max_outstanding> parameter for the default DNS
		1644	resolver - this is the maximum number of parallel DNS requests that are
		1645	sent to the DNS server.
		1646
		1647	=item C<PERL_ANYEVENT_RESOLV_CONF>
		1648
		1649	The file to use instead of F</etc/resolv.conf> (or OS-specific
		1650	configuration) in the default resolver. When set to the empty string, no
		1651	default config will be used.
		1652
		1653	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		1654
		1655	When neither C<ca_file> nor C<ca_path> was specified during
		1656	L<AnyEvent::TLS> context creation, and either of these environment
		1657	variables exist, they will be used to specify CA certificate locations
		1658	instead of a system-dependent default.
		1659
		1660	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		1661
		1662	When these are set to C<1>, then the respective modules are not
		1663	loaded. Mostly good for testing AnyEvent itself.
		1664
		1665	=back
1086		1666
1087	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1667	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
1088		1668
1089	This is an advanced topic that you do not normally need to use AnyEvent in	1669	This is an advanced topic that you do not normally need to use AnyEvent in
1090	a module. This section is only of use to event loop authors who want to	1670	a module. This section is only of use to event loop authors who want to
…		…
1124		1704
1125	I<rxvt-unicode> also cheats a bit by not providing blocking access to	1705	I<rxvt-unicode> also cheats a bit by not providing blocking access to
1126	condition variables: code blocking while waiting for a condition will	1706	condition variables: code blocking while waiting for a condition will
1127	C<die>. This still works with most modules/usages, and blocking calls must	1707	C<die>. This still works with most modules/usages, and blocking calls must
1128	not be done in an interactive application, so it makes sense.	1708	not be done in an interactive application, so it makes sense.
1129
1130	=head1 ENVIRONMENT VARIABLES
1131
1132	The following environment variables are used by this module:
1133
1134	=over 4
1135
1136	=item C<PERL_ANYEVENT_VERBOSE>
1137
1138	By default, AnyEvent will be completely silent except in fatal
1139	conditions. You can set this environment variable to make AnyEvent more
1140	talkative.
1141
1142	When set to C<1> or higher, causes AnyEvent to warn about unexpected
1143	conditions, such as not being able to load the event model specified by
1144	C<PERL_ANYEVENT_MODEL>.
1145
1146	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
1147	model it chooses.
1148
1149	=item C<PERL_ANYEVENT_MODEL>
1150
1151	This can be used to specify the event model to be used by AnyEvent, before
1152	auto detection and -probing kicks in. It must be a string consisting
1153	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
1154	and the resulting module name is loaded and if the load was successful,
1155	used as event model. If it fails to load AnyEvent will proceed with
1156	auto detection and -probing.
1157
1158	This functionality might change in future versions.
1159
1160	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
1161	could start your program like this:
1162
1163	PERL_ANYEVENT_MODEL=Perl perl ...
1164
1165	=item C<PERL_ANYEVENT_PROTOCOLS>
1166
1167	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
1168	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
1169	of auto probing).
1170
1171	Must be set to a comma-separated list of protocols or address families,
1172	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
1173	used, and preference will be given to protocols mentioned earlier in the
1174	list.
1175
1176	This variable can effectively be used for denial-of-service attacks
1177	against local programs (e.g. when setuid), although the impact is likely
1178	small, as the program has to handle connection errors already-
1179
1180	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
1181	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
1182	- only support IPv4, never try to resolve or contact IPv6
1183	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
1184	IPv6, but prefer IPv6 over IPv4.
1185
1186	=item C<PERL_ANYEVENT_EDNS0>
1187
1188	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
1189	for DNS. This extension is generally useful to reduce DNS traffic, but
1190	some (broken) firewalls drop such DNS packets, which is why it is off by
1191	default.
1192
1193	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
1194	EDNS0 in its DNS requests.
1195
1196	=item C<PERL_ANYEVENT_MAX_FORKS>
1197
1198	The maximum number of child processes that C<AnyEvent::Util::fork_call>
1199	will create in parallel.
1200
1201	=back
1202		1709
1203	=head1 EXAMPLE PROGRAM	1710	=head1 EXAMPLE PROGRAM
1204		1711
1205	The following program uses an I/O watcher to read data from STDIN, a timer	1712	The following program uses an I/O watcher to read data from STDIN, a timer
1206	to display a message once per second, and a condition variable to quit the	1713	to display a message once per second, and a condition variable to quit the
…		…
1400	watcher.	1907	watcher.
1401		1908
1402	=head3 Results	1909	=head3 Results
1403		1910
1404	name watchers bytes create invoke destroy comment	1911	name watchers bytes create invoke destroy comment
1405	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	1912	EV/EV 400000 224 0.47 0.35 0.27 EV native interface
1406	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	1913	EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers
1407	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	1914	CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal
1408	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	1915	Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation
1409	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	1916	Event/Event 16000 517 32.20 31.80 0.81 Event native interface
1410	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers	1917	Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers
		1918	IOAsync/Any 16000 989 38.10 32.77 11.13 via IO::Async::Loop::IO_Poll
		1919	IOAsync/Any 16000 990 37.59 29.50 10.61 via IO::Async::Loop::Epoll
1411	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	1920	Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour
1412	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	1921	Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers
1413	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	1922	POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event
1414	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	1923	POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select
1415		1924
1416	=head3 Discussion	1925	=head3 Discussion
1417		1926
1418	The benchmark does I<not> measure scalability of the event loop very	1927	The benchmark does I<not> measure scalability of the event loop very
1419	well. For example, a select-based event loop (such as the pure perl one)	1928	well. For example, a select-based event loop (such as the pure perl one)
…		…
1444	performance becomes really bad with lots of file descriptors (and few of	1953	performance becomes really bad with lots of file descriptors (and few of
1445	them active), of course, but this was not subject of this benchmark.	1954	them active), of course, but this was not subject of this benchmark.
1446		1955
1447	The C<Event> module has a relatively high setup and callback invocation	1956	The C<Event> module has a relatively high setup and callback invocation
1448	cost, but overall scores in on the third place.	1957	cost, but overall scores in on the third place.
		1958
		1959	C<IO::Async> performs admirably well, about on par with C<Event>, even
		1960	when using its pure perl backend.
1449		1961
1450	C<Glib>'s memory usage is quite a bit higher, but it features a	1962	C<Glib>'s memory usage is quite a bit higher, but it features a
1451	faster callback invocation and overall ends up in the same class as	1963	faster callback invocation and overall ends up in the same class as
1452	C<Event>. However, Glib scales extremely badly, doubling the number of	1964	C<Event>. However, Glib scales extremely badly, doubling the number of
1453	watchers increases the processing time by more than a factor of four,	1965	watchers increases the processing time by more than a factor of four,
…		…
1531	it to another server. This includes deleting the old timeout and creating	2043	it to another server. This includes deleting the old timeout and creating
1532	a new one that moves the timeout into the future.	2044	a new one that moves the timeout into the future.
1533		2045
1534	=head3 Results	2046	=head3 Results
1535		2047
1536	name sockets create request	2048	name sockets create request
1537	EV 20000 69.01 11.16	2049	EV 20000 69.01 11.16
1538	Perl 20000 73.32 35.87	2050	Perl 20000 73.32 35.87
		2051	IOAsync 20000 157.00 98.14 epoll
		2052	IOAsync 20000 159.31 616.06 poll
1539	Event 20000 212.62 257.32	2053	Event 20000 212.62 257.32
1540	Glib 20000 651.16 1896.30	2054	Glib 20000 651.16 1896.30
1541	POE 20000 349.67 12317.24 uses POE::Loop::Event	2055	POE 20000 349.67 12317.24 uses POE::Loop::Event
1542		2056
1543	=head3 Discussion	2057	=head3 Discussion
1544		2058
1545	This benchmark I<does> measure scalability and overall performance of the	2059	This benchmark I<does> measure scalability and overall performance of the
1546	particular event loop.	2060	particular event loop.
…		…
1548	EV is again fastest. Since it is using epoll on my system, the setup time	2062	EV is again fastest. Since it is using epoll on my system, the setup time
1549	is relatively high, though.	2063	is relatively high, though.
1550		2064
1551	Perl surprisingly comes second. It is much faster than the C-based event	2065	Perl surprisingly comes second. It is much faster than the C-based event
1552	loops Event and Glib.	2066	loops Event and Glib.
		2067
		2068	IO::Async performs very well when using its epoll backend, and still quite
		2069	good compared to Glib when using its pure perl backend.
1553		2070
1554	Event suffers from high setup time as well (look at its code and you will	2071	Event suffers from high setup time as well (look at its code and you will
1555	understand why). Callback invocation also has a high overhead compared to	2072	understand why). Callback invocation also has a high overhead compared to
1556	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event	2073	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
1557	uses select or poll in basically all documented configurations.	2074	uses select or poll in basically all documented configurations.
…		…
1620	=item * C-based event loops perform very well with small number of	2137	=item * C-based event loops perform very well with small number of
1621	watchers, as the management overhead dominates.	2138	watchers, as the management overhead dominates.
1622		2139
1623	=back	2140	=back
1624		2141
		2142	=head2 THE IO::Lambda BENCHMARK
		2143
		2144	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2145	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2146	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2147	shouldn't come as a surprise to anybody). As such, the benchmark is
		2148	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2149	very optimal. But how would AnyEvent compare when used without the extra
		2150	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2151
		2152	The benchmark itself creates an echo-server, and then, for 500 times,
		2153	connects to the echo server, sends a line, waits for the reply, and then
		2154	creates the next connection. This is a rather bad benchmark, as it doesn't
		2155	test the efficiency of the framework or much non-blocking I/O, but it is a
		2156	benchmark nevertheless.
		2157
		2158	name runtime
		2159	Lambda/select 0.330 sec
		2160	+ optimized 0.122 sec
		2161	Lambda/AnyEvent 0.327 sec
		2162	+ optimized 0.138 sec
		2163	Raw sockets/select 0.077 sec
		2164	POE/select, components 0.662 sec
		2165	POE/select, raw sockets 0.226 sec
		2166	POE/select, optimized 0.404 sec
		2167
		2168	AnyEvent/select/nb 0.085 sec
		2169	AnyEvent/EV/nb 0.068 sec
		2170	+state machine 0.134 sec
		2171
		2172	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2173	benchmarks actually make blocking connects and use 100% blocking I/O,
		2174	defeating the purpose of an event-based solution. All of the newly
		2175	written AnyEvent benchmarks use 100% non-blocking connects (using
		2176	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2177	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2178	generally require a lot more bookkeeping and event handling than blocking
		2179	connects (which involve a single syscall only).
		2180
		2181	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2182	offers similar expressive power as POE and IO::Lambda, using conventional
		2183	Perl syntax. This means that both the echo server and the client are 100%
		2184	non-blocking, further placing it at a disadvantage.
		2185
		2186	As you can see, the AnyEvent + EV combination even beats the
		2187	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2188	backend easily beats IO::Lambda and POE.
		2189
		2190	And even the 100% non-blocking version written using the high-level (and
		2191	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda by a
		2192	large margin, even though it does all of DNS, tcp-connect and socket I/O
		2193	in a non-blocking way.
		2194
		2195	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2196	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2197	part of the IO::lambda distribution and were used without any changes.
		2198
		2199
		2200	=head1 SIGNALS
		2201
		2202	AnyEvent currently installs handlers for these signals:
		2203
		2204	=over 4
		2205
		2206	=item SIGCHLD
		2207
		2208	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2209	emulation for event loops that do not support them natively. Also, some
		2210	event loops install a similar handler.
		2211
		2212	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2213	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2214
		2215	=item SIGPIPE
		2216
		2217	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2218	when AnyEvent gets loaded.
		2219
		2220	The rationale for this is that AnyEvent users usually do not really depend
		2221	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2222	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2223	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2224	some random socket.
		2225
		2226	The rationale for installing a no-op handler as opposed to ignoring it is
		2227	that this way, the handler will be restored to defaults on exec.
		2228
		2229	Feel free to install your own handler, or reset it to defaults.
		2230
		2231	=back
		2232
		2233	=cut
		2234
		2235	undef $SIG{CHLD}
		2236	if $SIG{CHLD} eq 'IGNORE';
		2237
		2238	$SIG{PIPE} = sub { }
		2239	unless defined $SIG{PIPE};
		2240
		2241	=head1 RECOMMENDED/OPTIONAL MODULES
		2242
		2243	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2244	it's built-in modules) are required to use it.
		2245
		2246	That does not mean that AnyEvent won't take advantage of some additional
		2247	modules if they are installed.
		2248
		2249	This section epxlains which additional modules will be used, and how they
		2250	affect AnyEvent's operetion.
		2251
		2252	=over 4
		2253
		2254	=item L<Async::Interrupt>
		2255
		2256	This slightly arcane module is used to implement fast signal handling: To
		2257	my knowledge, there is no way to do completely race-free and quick
		2258	signal handling in pure perl. To ensure that signals still get
		2259	delivered, AnyEvent will start an interval timer to wake up perl (and
		2260	catch the signals) with soemd elay (default is 10 seconds, look for
		2261	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2262
		2263	If this module is available, then it will be used to implement signal
		2264	catching, which means that signals will not be delayed, and the event loop
		2265	will not be interrupted regularly, which is more efficient (And good for
		2266	battery life on laptops).
		2267
		2268	This affects not just the pure-perl event loop, but also other event loops
		2269	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2270
		2271	=item L<EV>
		2272
		2273	This module isn't really "optional", as it is simply one of the backend
		2274	event loops that AnyEvent can use. However, it is simply the best event
		2275	loop available in terms of features, speed and stability: It supports
		2276	the AnyEvent API optimally, implements all the watcher types in XS, does
		2277	automatic timer adjustments even when no monotonic clock is available,
		2278	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2279	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2280	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2281
		2282	=item L<Guard>
		2283
		2284	The guard module, when used, will be used to implement
		2285	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2286	lot less memory), but otherwise doesn't affect guard operation much. It is
		2287	purely used for performance.
		2288
		2289	=item L<JSON> and L<JSON::XS>
		2290
		2291	This module is required when you want to read or write JSON data via
		2292	L<AnyEvent::Handle>. It is also written in pure-perl, but can take
		2293	advantage of the ulta-high-speed L<JSON::XS> module when it is installed.
		2294
		2295	In fact, L<AnyEvent::Handle> will use L<JSON::XS> by default if it is
		2296	installed.
		2297
		2298	=item L<Net::SSLeay>
		2299
		2300	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2301	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2302	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2303
		2304	=item L<Time::HiRes>
		2305
		2306	This module is part of perl since release 5.008. It will be used when the
		2307	chosen event library does not come with a timing source on it's own. The
		2308	pure-perl event loop (L<AnyEvent::Impl::Perl>) will additionally use it to
		2309	try to use a monotonic clock for timing stability.
		2310
		2311	=back
		2312
1625		2313
1626	=head1 FORK	2314	=head1 FORK
1627		2315
1628	Most event libraries are not fork-safe. The ones who are usually are	2316	Most event libraries are not fork-safe. The ones who are usually are
1629	because they rely on inefficient but fork-safe C<select> or C<poll>	2317	because they rely on inefficient but fork-safe C<select> or C<poll>
1630	calls. Only L<EV> is fully fork-aware.	2318	calls. Only L<EV> is fully fork-aware.
1631		2319
1632	If you have to fork, you must either do so I<before> creating your first	2320	If you have to fork, you must either do so I<before> creating your first
1633	watcher OR you must not use AnyEvent at all in the child.	2321	watcher OR you must not use AnyEvent at all in the child OR you must do
		2322	something completely out of the scope of AnyEvent.
1634		2323
1635		2324
1636	=head1 SECURITY CONSIDERATIONS	2325	=head1 SECURITY CONSIDERATIONS
1637		2326
1638	AnyEvent can be forced to load any event model via	2327	AnyEvent can be forced to load any event model via
…		…
1643	specified in the variable.	2332	specified in the variable.
1644		2333
1645	You can make AnyEvent completely ignore this variable by deleting it	2334	You can make AnyEvent completely ignore this variable by deleting it
1646	before the first watcher gets created, e.g. with a C<BEGIN> block:	2335	before the first watcher gets created, e.g. with a C<BEGIN> block:
1647		2336
1648	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	2337	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1649		2338
1650	use AnyEvent;	2339	use AnyEvent;
1651		2340
1652	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can	2341	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1653	be used to probe what backend is used and gain other information (which is	2342	be used to probe what backend is used and gain other information (which is
1654	probably even less useful to an attacker than PERL_ANYEVENT_MODEL).	2343	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2344	$ENV{PERL_ANYEVENT_STRICT}.
		2345
		2346	Note that AnyEvent will remove I<all> environment variables starting with
		2347	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2348	enabled.
		2349
		2350
		2351	=head1 BUGS
		2352
		2353	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2354	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2355	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2356	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2357	pronounced).
1655		2358
1656		2359
1657	=head1 SEE ALSO	2360	=head1 SEE ALSO
1658		2361
1659	Utility functions: L<AnyEvent::Util>.	2362	Utility functions: L<AnyEvent::Util>.
…		…
1662	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.	2365	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
1663		2366
1664	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,	2367	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
1665	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,	2368	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
1666	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,	2369	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1667	L<AnyEvent::Impl::POE>.	2370	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>.
1668		2371
1669	Non-blocking file handles, sockets, TCP clients and	2372	Non-blocking file handles, sockets, TCP clients and
1670	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>.	2373	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
1671		2374
1672	Asynchronous DNS: L<AnyEvent::DNS>.	2375	Asynchronous DNS: L<AnyEvent::DNS>.
1673		2376
1674	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,	2377	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>,
		2378	L<Coro::Event>,
1675		2379
1676	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>, L<AnyEvent::DNS>.	2380	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::XMPP>,
		2381	L<AnyEvent::HTTP>.
1677		2382
1678		2383
1679	=head1 AUTHOR	2384	=head1 AUTHOR
1680		2385
1681	Marc Lehmann <schmorp@schmorp.de>	2386	Marc Lehmann <schmorp@schmorp.de>
1682	http://home.schmorp.de/	2387	http://home.schmorp.de/
1683		2388
1684	=cut	2389	=cut
1685		2390
1686	1	2391	1
1687		2392

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