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Revision 1.249 by root, Mon Jul 20 06:00:42 2009 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent - provide framework for multiple event loops	3	AnyEvent - events independent of event loop implementation
4		4
5	EV, Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event loops	5	EV, Event, Glib, Tk, Perl, Event::Lib, Qt and POE are various supported
		6	event loops.
6		7
7	=head1 SYNOPSIS	8	=head1 SYNOPSIS
8		9
9	use AnyEvent;	10	use AnyEvent;
10		11
		12	# file descriptor readable
11	my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub {	13	my $w = AnyEvent->io (fh => $fh, poll => "r", cb => sub { ... });
		14
		15	# one-shot or repeating timers
		16	my $w = AnyEvent->timer (after => $seconds, cb => sub { ... });
		17	my $w = AnyEvent->timer (after => $seconds, interval => $seconds, cb => ...
		18
		19	print AnyEvent->now; # prints current event loop time
		20	print AnyEvent->time; # think Time::HiRes::time or simply CORE::time.
		21
		22	# POSIX signal
		23	my $w = AnyEvent->signal (signal => "TERM", cb => sub { ... });
		24
		25	# child process exit
		26	my $w = AnyEvent->child (pid => $pid, cb => sub {
		27	my ($pid, $status) = @_;
12	...	28	...
13	});	29	});
14		30
15	my $w = AnyEvent->timer (after => $seconds, cb => sub {	31	# called when event loop idle (if applicable)
16	...	32	my $w = AnyEvent->idle (cb => sub { ... });
17	});
18		33
19	my $w = AnyEvent->condvar; # stores whether a condition was flagged	34	my $w = AnyEvent->condvar; # stores whether a condition was flagged
20	$w->send; # wake up current and all future recv's	35	$w->send; # wake up current and all future recv's
21	$w->recv; # enters "main loop" till $condvar gets ->send	36	$w->recv; # enters "main loop" till $condvar gets ->send
		37	# use a condvar in callback mode:
		38	$w->cb (sub { $_[0]->recv });
22		39
23	=head1 INTRODUCTION/TUTORIAL	40	=head1 INTRODUCTION/TUTORIAL
24		41
25	This manpage is mainly a reference manual. If you are interested	42	This manpage is mainly a reference manual. If you are interested
26	in a tutorial or some gentle introduction, have a look at the	43	in a tutorial or some gentle introduction, have a look at the
27	L<AnyEvent::Intro> manpage.	44	L<AnyEvent::Intro> manpage.
28		45
		46	=head1 SUPPORT
		47
		48	There is a mailinglist for discussing all things AnyEvent, and an IRC
		49	channel, too.
		50
		51	See the AnyEvent project page at the B<Schmorpforge Ta-Sa Software
		52	Respository>, at L<http://anyevent.schmorp.de>, for more info.
		53
29	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)	54	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
30		55
31	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen	56	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
32	nowadays. So what is different about AnyEvent?	57	nowadays. So what is different about AnyEvent?
33		58
34	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of	59	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
35	policy> and AnyEvent is I<small and efficient>.	60	policy> and AnyEvent is I<small and efficient>.
36		61
37	First and foremost, I<AnyEvent is not an event model> itself, it only	62	First and foremost, I<AnyEvent is not an event model> itself, it only
38	interfaces to whatever event model the main program happens to use in a	63	interfaces to whatever event model the main program happens to use, in a
39	pragmatic way. For event models and certain classes of immortals alike,	64	pragmatic way. For event models and certain classes of immortals alike,
40	the statement "there can only be one" is a bitter reality: In general,	65	the statement "there can only be one" is a bitter reality: In general,
41	only one event loop can be active at the same time in a process. AnyEvent	66	only one event loop can be active at the same time in a process. AnyEvent
42	helps hiding the differences between those event loops.	67	cannot change this, but it can hide the differences between those event
		68	loops.
43		69
44	The goal of AnyEvent is to offer module authors the ability to do event	70	The goal of AnyEvent is to offer module authors the ability to do event
45	programming (waiting for I/O or timer events) without subscribing to a	71	programming (waiting for I/O or timer events) without subscribing to a
46	religion, a way of living, and most importantly: without forcing your	72	religion, a way of living, and most importantly: without forcing your
47	module users into the same thing by forcing them to use the same event	73	module users into the same thing by forcing them to use the same event
48	model you use.	74	model you use.
49		75
50	For modules like POE or IO::Async (which is a total misnomer as it is	76	For modules like POE or IO::Async (which is a total misnomer as it is
51	actually doing all I/O I<synchronously>...), using them in your module is	77	actually doing all I/O I<synchronously>...), using them in your module is
52	like joining a cult: After you joined, you are dependent on them and you	78	like joining a cult: After you joined, you are dependent on them and you
53	cannot use anything else, as it is simply incompatible to everything that	79	cannot use anything else, as they are simply incompatible to everything
54	isn't itself. What's worse, all the potential users of your module are	80	that isn't them. What's worse, all the potential users of your
55	I<also> forced to use the same event loop you use.	81	module are I<also> forced to use the same event loop you use.
56		82
57	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works	83	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
58	fine. AnyEvent + Tk works fine etc. etc. but none of these work together	84	fine. AnyEvent + Tk works fine etc. etc. but none of these work together
59	with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if	85	with the rest: POE + IO::Async? No go. Tk + Event? No go. Again: if
60	your module uses one of those, every user of your module has to use it,	86	your module uses one of those, every user of your module has to use it,
61	too. But if your module uses AnyEvent, it works transparently with all	87	too. But if your module uses AnyEvent, it works transparently with all
62	event models it supports (including stuff like POE and IO::Async, as long	88	event models it supports (including stuff like IO::Async, as long as those
63	as those use one of the supported event loops. It is trivial to add new	89	use one of the supported event loops. It is trivial to add new event loops
64	event loops to AnyEvent, too, so it is future-proof).	90	to AnyEvent, too, so it is future-proof).
65		91
66	In addition to being free of having to use I<the one and only true event	92	In addition to being free of having to use I<the one and only true event
67	model>, AnyEvent also is free of bloat and policy: with POE or similar	93	model>, AnyEvent also is free of bloat and policy: with POE or similar
68	modules, you get an enormous amount of code and strict rules you have to	94	modules, you get an enormous amount of code and strict rules you have to
69	follow. AnyEvent, on the other hand, is lean and up to the point, by only	95	follow. AnyEvent, on the other hand, is lean and up to the point, by only
…		…
127	These watchers are normal Perl objects with normal Perl lifetime. After	153	These watchers are normal Perl objects with normal Perl lifetime. After
128	creating a watcher it will immediately "watch" for events and invoke the	154	creating a watcher it will immediately "watch" for events and invoke the
129	callback when the event occurs (of course, only when the event model	155	callback when the event occurs (of course, only when the event model
130	is in control).	156	is in control).
131		157
		158	Note that B<callbacks must not permanently change global variables>
		159	potentially in use by the event loop (such as C<$_> or C<$[>) and that B<<
		160	callbacks must not C<die> >>. The former is good programming practise in
		161	Perl and the latter stems from the fact that exception handling differs
		162	widely between event loops.
		163
132	To disable the watcher you have to destroy it (e.g. by setting the	164	To disable the watcher you have to destroy it (e.g. by setting the
133	variable you store it in to C<undef> or otherwise deleting all references	165	variable you store it in to C<undef> or otherwise deleting all references
134	to it).	166	to it).
135		167
136	All watchers are created by calling a method on the C<AnyEvent> class.	168	All watchers are created by calling a method on the C<AnyEvent> class.
…		…
138	Many watchers either are used with "recursion" (repeating timers for	170	Many watchers either are used with "recursion" (repeating timers for
139	example), or need to refer to their watcher object in other ways.	171	example), or need to refer to their watcher object in other ways.
140		172
141	An any way to achieve that is this pattern:	173	An any way to achieve that is this pattern:
142		174
143	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {	175	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
144	# you can use $w here, for example to undef it	176	# you can use $w here, for example to undef it
145	undef $w;	177	undef $w;
146	});	178	});
147		179
148	Note that C<my $w; $w => combination. This is necessary because in Perl,	180	Note that C<my $w; $w => combination. This is necessary because in Perl,
149	my variables are only visible after the statement in which they are	181	my variables are only visible after the statement in which they are
150	declared.	182	declared.
151		183
152	=head2 I/O WATCHERS	184	=head2 I/O WATCHERS
153		185
154	You can create an I/O watcher by calling the C<< AnyEvent->io >> method	186	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
155	with the following mandatory key-value pairs as arguments:	187	with the following mandatory key-value pairs as arguments:
156		188
157	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch	189	C<fh> is the Perl I<file handle> (or a naked file descriptor) to watch
		190	for events (AnyEvent might or might not keep a reference to this file
		191	handle). Note that only file handles pointing to things for which
		192	non-blocking operation makes sense are allowed. This includes sockets,
		193	most character devices, pipes, fifos and so on, but not for example files
		194	or block devices.
		195
158	for events. C<poll> must be a string that is either C<r> or C<w>,	196	C<poll> must be a string that is either C<r> or C<w>, which creates a
159	which creates a watcher waiting for "r"eadable or "w"ritable events,	197	watcher waiting for "r"eadable or "w"ritable events, respectively.
		198
160	respectively. C<cb> is the callback to invoke each time the file handle	199	C<cb> is the callback to invoke each time the file handle becomes ready.
161	becomes ready.
162		200
163	Although the callback might get passed parameters, their value and	201	Although the callback might get passed parameters, their value and
164	presence is undefined and you cannot rely on them. Portable AnyEvent	202	presence is undefined and you cannot rely on them. Portable AnyEvent
165	callbacks cannot use arguments passed to I/O watcher callbacks.	203	callbacks cannot use arguments passed to I/O watcher callbacks.
166		204
…		…
170		208
171	Some event loops issue spurious readyness notifications, so you should	209	Some event loops issue spurious readyness notifications, so you should
172	always use non-blocking calls when reading/writing from/to your file	210	always use non-blocking calls when reading/writing from/to your file
173	handles.	211	handles.
174		212
175	Example:
176
177	# wait for readability of STDIN, then read a line and disable the watcher	213	Example: wait for readability of STDIN, then read a line and disable the
		214	watcher.
		215
178	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	216	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
179	chomp (my $input = <STDIN>);	217	chomp (my $input = <STDIN>);
180	warn "read: $input\n";	218	warn "read: $input\n";
181	undef $w;	219	undef $w;
182	});	220	});
…		…
192		230
193	Although the callback might get passed parameters, their value and	231	Although the callback might get passed parameters, their value and
194	presence is undefined and you cannot rely on them. Portable AnyEvent	232	presence is undefined and you cannot rely on them. Portable AnyEvent
195	callbacks cannot use arguments passed to time watcher callbacks.	233	callbacks cannot use arguments passed to time watcher callbacks.
196		234
197	The timer callback will be invoked at most once: if you want a repeating	235	The callback will normally be invoked once only. If you specify another
198	timer you have to create a new watcher (this is a limitation by both Tk	236	parameter, C<interval>, as a strictly positive number (> 0), then the
199	and Glib).	237	callback will be invoked regularly at that interval (in fractional
		238	seconds) after the first invocation. If C<interval> is specified with a
		239	false value, then it is treated as if it were missing.
200		240
201	Example:	241	The callback will be rescheduled before invoking the callback, but no
		242	attempt is done to avoid timer drift in most backends, so the interval is
		243	only approximate.
202		244
203	# fire an event after 7.7 seconds	245	Example: fire an event after 7.7 seconds.
		246
204	my $w = AnyEvent->timer (after => 7.7, cb => sub {	247	my $w = AnyEvent->timer (after => 7.7, cb => sub {
205	warn "timeout\n";	248	warn "timeout\n";
206	});	249	});
207		250
208	# to cancel the timer:	251	# to cancel the timer:
209	undef $w;	252	undef $w;
210		253
211	Example 2:
212
213	# fire an event after 0.5 seconds, then roughly every second	254	Example 2: fire an event after 0.5 seconds, then roughly every second.
214	my $w;
215		255
216	my $cb = sub {
217	# cancel the old timer while creating a new one
218	$w = AnyEvent->timer (after => 1, cb => $cb);	256	my $w = AnyEvent->timer (after => 0.5, interval => 1, cb => sub {
		257	warn "timeout\n";
219	};	258	};
220
221	# start the "loop" by creating the first watcher
222	$w = AnyEvent->timer (after => 0.5, cb => $cb);
223		259
224	=head3 TIMING ISSUES	260	=head3 TIMING ISSUES
225		261
226	There are two ways to handle timers: based on real time (relative, "fire	262	There are two ways to handle timers: based on real time (relative, "fire
227	in 10 seconds") and based on wallclock time (absolute, "fire at 12	263	in 10 seconds") and based on wallclock time (absolute, "fire at 12
…		…
300	In either case, if you care (and in most cases, you don't), then you	336	In either case, if you care (and in most cases, you don't), then you
301	can get whatever behaviour you want with any event loop, by taking the	337	can get whatever behaviour you want with any event loop, by taking the
302	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into	338	difference between C<< AnyEvent->time >> and C<< AnyEvent->now >> into
303	account.	339	account.
304		340
		341	=item AnyEvent->now_update
		342
		343	Some event loops (such as L<EV> or L<AnyEvent::Impl::Perl>) cache
		344	the current time for each loop iteration (see the discussion of L<<
		345	AnyEvent->now >>, above).
		346
		347	When a callback runs for a long time (or when the process sleeps), then
		348	this "current" time will differ substantially from the real time, which
		349	might affect timers and time-outs.
		350
		351	When this is the case, you can call this method, which will update the
		352	event loop's idea of "current time".
		353
		354	Note that updating the time I<might> cause some events to be handled.
		355
305	=back	356	=back
306		357
307	=head2 SIGNAL WATCHERS	358	=head2 SIGNAL WATCHERS
308		359
309	You can watch for signals using a signal watcher, C<signal> is the signal	360	You can watch for signals using a signal watcher, C<signal> is the signal
310	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to	361	I<name> in uppercase and without any C<SIG> prefix, C<cb> is the Perl
311	be invoked whenever a signal occurs.	362	callback to be invoked whenever a signal occurs.
312		363
313	Although the callback might get passed parameters, their value and	364	Although the callback might get passed parameters, their value and
314	presence is undefined and you cannot rely on them. Portable AnyEvent	365	presence is undefined and you cannot rely on them. Portable AnyEvent
315	callbacks cannot use arguments passed to signal watcher callbacks.	366	callbacks cannot use arguments passed to signal watcher callbacks.
316		367
…		…
318	invocation, and callback invocation will be synchronous. Synchronous means	369	invocation, and callback invocation will be synchronous. Synchronous means
319	that it might take a while until the signal gets handled by the process,	370	that it might take a while until the signal gets handled by the process,
320	but it is guaranteed not to interrupt any other callbacks.	371	but it is guaranteed not to interrupt any other callbacks.
321		372
322	The main advantage of using these watchers is that you can share a signal	373	The main advantage of using these watchers is that you can share a signal
323	between multiple watchers.	374	between multiple watchers, and AnyEvent will ensure that signals will not
		375	interrupt your program at bad times.
324		376
325	This watcher might use C<%SIG>, so programs overwriting those signals	377	This watcher might use C<%SIG> (depending on the event loop used),
326	directly will likely not work correctly.	378	so programs overwriting those signals directly will likely not work
		379	correctly.
327		380
328	Example: exit on SIGINT	381	Example: exit on SIGINT
329		382
330	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });	383	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
331		384
		385	=head3 Signal Races, Delays and Workarounds
		386
		387	Many event loops (e.g. Glib, Tk, Qt, IO::Async) do not support attaching
		388	callbacks to signals in a generic way, which is a pity, as you cannot do
		389	race-free signal handling in perl. AnyEvent will try to do it's best, but
		390	in some cases, signals will be delayed. The maximum time a signal might
		391	be delayed is specified in C<$AnyEvent::MAX_SIGNAL_LATENCY> (default: 10
		392	seconds). This variable can be changed only before the first signal
		393	watcher is created, and should be left alone otherwise. Higher values
		394	will cause fewer spurious wake-ups, which is better for power and CPU
		395	saving. All these problems can be avoided by installing the optional
		396	L<Async::Interrupt> module. This will not work with inherently broken
		397	event loops such as L<Event> or L<Event::Lib> (and not with L<POE>
		398	currently, as POE does it's own workaround with one-second latency). With
		399	those, you just have to suffer the delays.
		400
332	=head2 CHILD PROCESS WATCHERS	401	=head2 CHILD PROCESS WATCHERS
333		402
334	You can also watch on a child process exit and catch its exit status.	403	You can also watch on a child process exit and catch its exit status.
335		404
336	The child process is specified by the C<pid> argument (if set to C<0>, it	405	The child process is specified by the C<pid> argument (if set to C<0>, it
337	watches for any child process exit). The watcher will trigger as often	406	watches for any child process exit). The watcher will triggered only when
338	as status change for the child are received. This works by installing a	407	the child process has finished and an exit status is available, not on
339	signal handler for C<SIGCHLD>. The callback will be called with the pid	408	any trace events (stopped/continued).
340	and exit status (as returned by waitpid), so unlike other watcher types,	409
341	you I<can> rely on child watcher callback arguments.	410	The callback will be called with the pid and exit status (as returned by
		411	waitpid), so unlike other watcher types, you I<can> rely on child watcher
		412	callback arguments.
		413
		414	This watcher type works by installing a signal handler for C<SIGCHLD>,
		415	and since it cannot be shared, nothing else should use SIGCHLD or reap
		416	random child processes (waiting for specific child processes, e.g. inside
		417	C<system>, is just fine).
342		418
343	There is a slight catch to child watchers, however: you usually start them	419	There is a slight catch to child watchers, however: you usually start them
344	I<after> the child process was created, and this means the process could	420	I<after> the child process was created, and this means the process could
345	have exited already (and no SIGCHLD will be sent anymore).	421	have exited already (and no SIGCHLD will be sent anymore).
346		422
347	Not all event models handle this correctly (POE doesn't), but even for	423	Not all event models handle this correctly (neither POE nor IO::Async do,
		424	see their AnyEvent::Impl manpages for details), but even for event models
348	event models that I<do> handle this correctly, they usually need to be	425	that I<do> handle this correctly, they usually need to be loaded before
349	loaded before the process exits (i.e. before you fork in the first place).	426	the process exits (i.e. before you fork in the first place). AnyEvent's
		427	pure perl event loop handles all cases correctly regardless of when you
		428	start the watcher.
350		429
351	This means you cannot create a child watcher as the very first thing in an	430	This means you cannot create a child watcher as the very first
352	AnyEvent program, you I<have> to create at least one watcher before you	431	thing in an AnyEvent program, you I<have> to create at least one
353	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).	432	watcher before you C<fork> the child (alternatively, you can call
		433	C<AnyEvent::detect>).
		434
		435	As most event loops do not support waiting for child events, they will be
		436	emulated by AnyEvent in most cases, in which the latency and race problems
		437	mentioned in the description of signal watchers apply.
354		438
355	Example: fork a process and wait for it	439	Example: fork a process and wait for it
356		440
357	my $done = AnyEvent->condvar;	441	my $done = AnyEvent->condvar;
358		442
359	my $pid = fork or exit 5;	443	my $pid = fork or exit 5;
360		444
361	my $w = AnyEvent->child (	445	my $w = AnyEvent->child (
362	pid => $pid,	446	pid => $pid,
363	cb => sub {	447	cb => sub {
364	my ($pid, $status) = @_;	448	my ($pid, $status) = @_;
365	warn "pid $pid exited with status $status";	449	warn "pid $pid exited with status $status";
366	$done->send;	450	$done->send;
367	},	451	},
368	);	452	);
369		453
370	# do something else, then wait for process exit	454	# do something else, then wait for process exit
371	$done->recv;	455	$done->recv;
		456
		457	=head2 IDLE WATCHERS
		458
		459	Sometimes there is a need to do something, but it is not so important
		460	to do it instantly, but only when there is nothing better to do. This
		461	"nothing better to do" is usually defined to be "no other events need
		462	attention by the event loop".
		463
		464	Idle watchers ideally get invoked when the event loop has nothing
		465	better to do, just before it would block the process to wait for new
		466	events. Instead of blocking, the idle watcher is invoked.
		467
		468	Most event loops unfortunately do not really support idle watchers (only
		469	EV, Event and Glib do it in a usable fashion) - for the rest, AnyEvent
		470	will simply call the callback "from time to time".
		471
		472	Example: read lines from STDIN, but only process them when the
		473	program is otherwise idle:
		474
		475	my @lines; # read data
		476	my $idle_w;
		477	my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		478	push @lines, scalar <STDIN>;
		479
		480	# start an idle watcher, if not already done
		481	$idle_w ||= AnyEvent->idle (cb => sub {
		482	# handle only one line, when there are lines left
		483	if (my $line = shift @lines) {
		484	print "handled when idle: $line";
		485	} else {
		486	# otherwise disable the idle watcher again
		487	undef $idle_w;
		488	}
		489	});
		490	});
372		491
373	=head2 CONDITION VARIABLES	492	=head2 CONDITION VARIABLES
374		493
375	If you are familiar with some event loops you will know that all of them	494	If you are familiar with some event loops you will know that all of them
376	require you to run some blocking "loop", "run" or similar function that	495	require you to run some blocking "loop", "run" or similar function that
377	will actively watch for new events and call your callbacks.	496	will actively watch for new events and call your callbacks.
378		497
379	AnyEvent is different, it expects somebody else to run the event loop and	498	AnyEvent is slightly different: it expects somebody else to run the event
380	will only block when necessary (usually when told by the user).	499	loop and will only block when necessary (usually when told by the user).
381		500
382	The instrument to do that is called a "condition variable", so called	501	The instrument to do that is called a "condition variable", so called
383	because they represent a condition that must become true.	502	because they represent a condition that must become true.
		503
		504	Now is probably a good time to look at the examples further below.
384		505
385	Condition variables can be created by calling the C<< AnyEvent->condvar	506	Condition variables can be created by calling the C<< AnyEvent->condvar
386	>> method, usually without arguments. The only argument pair allowed is	507	>> method, usually without arguments. The only argument pair allowed is
387	C<cb>, which specifies a callback to be called when the condition variable	508	C<cb>, which specifies a callback to be called when the condition variable
388	becomes true.	509	becomes true, with the condition variable as the first argument (but not
		510	the results).
389		511
390	After creation, the condition variable is "false" until it becomes "true"	512	After creation, the condition variable is "false" until it becomes "true"
391	by calling the C<send> method (or calling the condition variable as if it	513	by calling the C<send> method (or calling the condition variable as if it
392	were a callback, read about the caveats in the description for the C<<	514	were a callback, read about the caveats in the description for the C<<
393	->send >> method).	515	->send >> method).
…		…
439	after => 1,	561	after => 1,
440	cb => sub { $result_ready->send },	562	cb => sub { $result_ready->send },
441	);	563	);
442		564
443	# this "blocks" (while handling events) till the callback	565	# this "blocks" (while handling events) till the callback
444	# calls send	566	# calls -<send
445	$result_ready->recv;	567	$result_ready->recv;
446		568
447	Example: wait for a timer, but take advantage of the fact that	569	Example: wait for a timer, but take advantage of the fact that condition
448	condition variables are also code references.	570	variables are also callable directly.
449		571
450	my $done = AnyEvent->condvar;	572	my $done = AnyEvent->condvar;
451	my $delay = AnyEvent->timer (after => 5, cb => $done);	573	my $delay = AnyEvent->timer (after => 5, cb => $done);
452	$done->recv;	574	$done->recv;
		575
		576	Example: Imagine an API that returns a condvar and doesn't support
		577	callbacks. This is how you make a synchronous call, for example from
		578	the main program:
		579
		580	use AnyEvent::CouchDB;
		581
		582	...
		583
		584	my @info = $couchdb->info->recv;
		585
		586	And this is how you would just set a callback to be called whenever the
		587	results are available:
		588
		589	$couchdb->info->cb (sub {
		590	my @info = $_[0]->recv;
		591	});
453		592
454	=head3 METHODS FOR PRODUCERS	593	=head3 METHODS FOR PRODUCERS
455		594
456	These methods should only be used by the producing side, i.e. the	595	These methods should only be used by the producing side, i.e. the
457	code/module that eventually sends the signal. Note that it is also	596	code/module that eventually sends the signal. Note that it is also
…		…
470	immediately from within send.	609	immediately from within send.
471		610
472	Any arguments passed to the C<send> call will be returned by all	611	Any arguments passed to the C<send> call will be returned by all
473	future C<< ->recv >> calls.	612	future C<< ->recv >> calls.
474		613
475	Condition variables are overloaded so one can call them directly	614	Condition variables are overloaded so one can call them directly (as if
476	(as a code reference). Calling them directly is the same as calling	615	they were a code reference). Calling them directly is the same as calling
477	C<send>. Note, however, that many C-based event loops do not handle	616	C<send>.
478	overloading, so as tempting as it may be, passing a condition variable
479	instead of a callback does not work. Both the pure perl and EV loops
480	support overloading, however, as well as all functions that use perl to
481	invoke a callback (as in L<AnyEvent::Socket> and L<AnyEvent::DNS> for
482	example).
483		617
484	=item $cv->croak ($error)	618	=item $cv->croak ($error)
485		619
486	Similar to send, but causes all call's to C<< ->recv >> to invoke	620	Similar to send, but causes all call's to C<< ->recv >> to invoke
487	C<Carp::croak> with the given error message/object/scalar.	621	C<Carp::croak> with the given error message/object/scalar.
488		622
489	This can be used to signal any errors to the condition variable	623	This can be used to signal any errors to the condition variable
490	user/consumer.	624	user/consumer. Doing it this way instead of calling C<croak> directly
		625	delays the error detetcion, but has the overwhelmign advantage that it
		626	diagnoses the error at the place where the result is expected, and not
		627	deep in some event clalback without connection to the actual code causing
		628	the problem.
491		629
492	=item $cv->begin ([group callback])	630	=item $cv->begin ([group callback])
493		631
494	=item $cv->end	632	=item $cv->end
495
496	These two methods are EXPERIMENTAL and MIGHT CHANGE.
497		633
498	These two methods can be used to combine many transactions/events into	634	These two methods can be used to combine many transactions/events into
499	one. For example, a function that pings many hosts in parallel might want	635	one. For example, a function that pings many hosts in parallel might want
500	to use a condition variable for the whole process.	636	to use a condition variable for the whole process.
501		637
…		…
503	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end	639	C<< ->end >> will decrement it. If the counter reaches C<0> in C<< ->end
504	>>, the (last) callback passed to C<begin> will be executed. That callback	640	>>, the (last) callback passed to C<begin> will be executed. That callback
505	is I<supposed> to call C<< ->send >>, but that is not required. If no	641	is I<supposed> to call C<< ->send >>, but that is not required. If no
506	callback was set, C<send> will be called without any arguments.	642	callback was set, C<send> will be called without any arguments.
507		643
508	Let's clarify this with the ping example:	644	You can think of C<< $cv->send >> giving you an OR condition (one call
		645	sends), while C<< $cv->begin >> and C<< $cv->end >> giving you an AND
		646	condition (all C<begin> calls must be C<end>'ed before the condvar sends).
		647
		648	Let's start with a simple example: you have two I/O watchers (for example,
		649	STDOUT and STDERR for a program), and you want to wait for both streams to
		650	close before activating a condvar:
		651
		652	my $cv = AnyEvent->condvar;
		653
		654	$cv->begin; # first watcher
		655	my $w1 = AnyEvent->io (fh => $fh1, cb => sub {
		656	defined sysread $fh1, my $buf, 4096
		657	or $cv->end;
		658	});
		659
		660	$cv->begin; # second watcher
		661	my $w2 = AnyEvent->io (fh => $fh2, cb => sub {
		662	defined sysread $fh2, my $buf, 4096
		663	or $cv->end;
		664	});
		665
		666	$cv->recv;
		667
		668	This works because for every event source (EOF on file handle), there is
		669	one call to C<begin>, so the condvar waits for all calls to C<end> before
		670	sending.
		671
		672	The ping example mentioned above is slightly more complicated, as the
		673	there are results to be passwd back, and the number of tasks that are
		674	begung can potentially be zero:
509		675
510	my $cv = AnyEvent->condvar;	676	my $cv = AnyEvent->condvar;
511		677
512	my %result;	678	my %result;
513	$cv->begin (sub { $cv->send (\%result) });	679	$cv->begin (sub { $cv->send (\%result) });
…		…
533	loop, which serves two important purposes: first, it sets the callback	699	loop, which serves two important purposes: first, it sets the callback
534	to be called once the counter reaches C<0>, and second, it ensures that	700	to be called once the counter reaches C<0>, and second, it ensures that
535	C<send> is called even when C<no> hosts are being pinged (the loop	701	C<send> is called even when C<no> hosts are being pinged (the loop
536	doesn't execute once).	702	doesn't execute once).
537		703
538	This is the general pattern when you "fan out" into multiple subrequests:	704	This is the general pattern when you "fan out" into multiple (but
539	use an outer C<begin>/C<end> pair to set the callback and ensure C<end>	705	potentially none) subrequests: use an outer C<begin>/C<end> pair to set
540	is called at least once, and then, for each subrequest you start, call	706	the callback and ensure C<end> is called at least once, and then, for each
541	C<begin> and for each subrequest you finish, call C<end>.	707	subrequest you start, call C<begin> and for each subrequest you finish,
		708	call C<end>.
542		709
543	=back	710	=back
544		711
545	=head3 METHODS FOR CONSUMERS	712	=head3 METHODS FOR CONSUMERS
546		713
…		…
562	function will call C<croak>.	729	function will call C<croak>.
563		730
564	In list context, all parameters passed to C<send> will be returned,	731	In list context, all parameters passed to C<send> will be returned,
565	in scalar context only the first one will be returned.	732	in scalar context only the first one will be returned.
566		733
		734	Note that doing a blocking wait in a callback is not supported by any
		735	event loop, that is, recursive invocation of a blocking C<< ->recv
		736	>> is not allowed, and the C<recv> call will C<croak> if such a
		737	condition is detected. This condition can be slightly loosened by using
		738	L<Coro::AnyEvent>, which allows you to do a blocking C<< ->recv >> from
		739	any thread that doesn't run the event loop itself.
		740
567	Not all event models support a blocking wait - some die in that case	741	Not all event models support a blocking wait - some die in that case
568	(programs might want to do that to stay interactive), so I<if you are	742	(programs might want to do that to stay interactive), so I<if you are
569	using this from a module, never require a blocking wait>, but let the	743	using this from a module, never require a blocking wait>. Instead, let the
570	caller decide whether the call will block or not (for example, by coupling	744	caller decide whether the call will block or not (for example, by coupling
571	condition variables with some kind of request results and supporting	745	condition variables with some kind of request results and supporting
572	callbacks so the caller knows that getting the result will not block,	746	callbacks so the caller knows that getting the result will not block,
573	while still supporting blocking waits if the caller so desires).	747	while still supporting blocking waits if the caller so desires).
574		748
575	Another reason I<never> to C<< ->recv >> in a module is that you cannot
576	sensibly have two C<< ->recv >>'s in parallel, as that would require
577	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
578	can supply.
579
580	The L<Coro> module, however, I<can> and I<does> supply coroutines and, in
581	fact, L<Coro::AnyEvent> replaces AnyEvent's condvars by coroutine-safe
582	versions and also integrates coroutines into AnyEvent, making blocking
583	C<< ->recv >> calls perfectly safe as long as they are done from another
584	coroutine (one that doesn't run the event loop).
585
586	You can ensure that C<< -recv >> never blocks by setting a callback and	749	You can ensure that C<< -recv >> never blocks by setting a callback and
587	only calling C<< ->recv >> from within that callback (or at a later	750	only calling C<< ->recv >> from within that callback (or at a later
588	time). This will work even when the event loop does not support blocking	751	time). This will work even when the event loop does not support blocking
589	waits otherwise.	752	waits otherwise.
590		753
591	=item $bool = $cv->ready	754	=item $bool = $cv->ready
592		755
593	Returns true when the condition is "true", i.e. whether C<send> or	756	Returns true when the condition is "true", i.e. whether C<send> or
594	C<croak> have been called.	757	C<croak> have been called.
595		758
596	=item $cb = $cv->cb ([new callback])	759	=item $cb = $cv->cb ($cb->($cv))
597		760
598	This is a mutator function that returns the callback set and optionally	761	This is a mutator function that returns the callback set and optionally
599	replaces it before doing so.	762	replaces it before doing so.
600		763
601	The callback will be called when the condition becomes "true", i.e. when	764	The callback will be called when the condition becomes "true", i.e. when
…		…
603	variable itself. Calling C<recv> inside the callback or at any later time	766	variable itself. Calling C<recv> inside the callback or at any later time
604	is guaranteed not to block.	767	is guaranteed not to block.
605		768
606	=back	769	=back
607		770
		771	=head1 SUPPORTED EVENT LOOPS/BACKENDS
		772
		773	The available backend classes are (every class has its own manpage):
		774
		775	=over 4
		776
		777	=item Backends that are autoprobed when no other event loop can be found.
		778
		779	EV is the preferred backend when no other event loop seems to be in
		780	use. If EV is not installed, then AnyEvent will try Event, and, failing
		781	that, will fall back to its own pure-perl implementation, which is
		782	available everywhere as it comes with AnyEvent itself.
		783
		784	AnyEvent::Impl::EV based on EV (interface to libev, best choice).
		785	AnyEvent::Impl::Event based on Event, very stable, few glitches.
		786	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
		787
		788	=item Backends that are transparently being picked up when they are used.
		789
		790	These will be used when they are currently loaded when the first watcher
		791	is created, in which case it is assumed that the application is using
		792	them. This means that AnyEvent will automatically pick the right backend
		793	when the main program loads an event module before anything starts to
		794	create watchers. Nothing special needs to be done by the main program.
		795
		796	AnyEvent::Impl::Glib based on Glib, slow but very stable.
		797	AnyEvent::Impl::Tk based on Tk, very broken.
		798	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		799	AnyEvent::Impl::POE based on POE, very slow, some limitations.
		800
		801	=item Backends with special needs.
		802
		803	Qt requires the Qt::Application to be instantiated first, but will
		804	otherwise be picked up automatically. As long as the main program
		805	instantiates the application before any AnyEvent watchers are created,
		806	everything should just work.
		807
		808	AnyEvent::Impl::Qt based on Qt.
		809
		810	Support for IO::Async can only be partial, as it is too broken and
		811	architecturally limited to even support the AnyEvent API. It also
		812	is the only event loop that needs the loop to be set explicitly, so
		813	it can only be used by a main program knowing about AnyEvent. See
		814	L<AnyEvent::Impl::Async> for the gory details.
		815
		816	AnyEvent::Impl::IOAsync based on IO::Async, cannot be autoprobed.
		817
		818	=item Event loops that are indirectly supported via other backends.
		819
		820	Some event loops can be supported via other modules:
		821
		822	There is no direct support for WxWidgets (L<Wx>) or L<Prima>.
		823
		824	B<WxWidgets> has no support for watching file handles. However, you can
		825	use WxWidgets through the POE adaptor, as POE has a Wx backend that simply
		826	polls 20 times per second, which was considered to be too horrible to even
		827	consider for AnyEvent.
		828
		829	B<Prima> is not supported as nobody seems to be using it, but it has a POE
		830	backend, so it can be supported through POE.
		831
		832	AnyEvent knows about both L<Prima> and L<Wx>, however, and will try to
		833	load L<POE> when detecting them, in the hope that POE will pick them up,
		834	in which case everything will be automatic.
		835
		836	=back
		837
608	=head1 GLOBAL VARIABLES AND FUNCTIONS	838	=head1 GLOBAL VARIABLES AND FUNCTIONS
609		839
		840	These are not normally required to use AnyEvent, but can be useful to
		841	write AnyEvent extension modules.
		842
610	=over 4	843	=over 4
611		844
612	=item $AnyEvent::MODEL	845	=item $AnyEvent::MODEL
613		846
614	Contains C<undef> until the first watcher is being created. Then it	847	Contains C<undef> until the first watcher is being created, before the
		848	backend has been autodetected.
		849
615	contains the event model that is being used, which is the name of the	850	Afterwards it contains the event model that is being used, which is the
616	Perl class implementing the model. This class is usually one of the	851	name of the Perl class implementing the model. This class is usually one
617	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case	852	of the C<AnyEvent::Impl:xxx> modules, but can be any other class in the
618	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).	853	case AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode> it
619		854	will be C<urxvt::anyevent>).
620	The known classes so far are:
621
622	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
623	AnyEvent::Impl::Event based on Event, second best choice.
624	AnyEvent::Impl::Perl pure-perl implementation, fast and portable.
625	AnyEvent::Impl::Glib based on Glib, third-best choice.
626	AnyEvent::Impl::Tk based on Tk, very bad choice.
627	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
628	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
629	AnyEvent::Impl::POE based on POE, not generic enough for full support.
630
631	There is no support for WxWidgets, as WxWidgets has no support for
632	watching file handles. However, you can use WxWidgets through the
633	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
634	second, which was considered to be too horrible to even consider for
635	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
636	it's adaptor.
637
638	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
639	autodetecting them.
640		855
641	=item AnyEvent::detect	856	=item AnyEvent::detect
642		857
643	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model	858	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
644	if necessary. You should only call this function right before you would	859	if necessary. You should only call this function right before you would
645	have created an AnyEvent watcher anyway, that is, as late as possible at	860	have created an AnyEvent watcher anyway, that is, as late as possible at
646	runtime.	861	runtime, and not e.g. while initialising of your module.
		862
		863	If you need to do some initialisation before AnyEvent watchers are
		864	created, use C<post_detect>.
647		865
648	=item $guard = AnyEvent::post_detect { BLOCK }	866	=item $guard = AnyEvent::post_detect { BLOCK }
649		867
650	Arranges for the code block to be executed as soon as the event model is	868	Arranges for the code block to be executed as soon as the event model is
651	autodetected (or immediately if this has already happened).	869	autodetected (or immediately if this has already happened).
		870
		871	The block will be executed I<after> the actual backend has been detected
		872	(C<$AnyEvent::MODEL> is set), but I<before> any watchers have been
		873	created, so it is possible to e.g. patch C<@AnyEvent::ISA> or do
		874	other initialisations - see the sources of L<AnyEvent::Strict> or
		875	L<AnyEvent::AIO> to see how this is used.
		876
		877	The most common usage is to create some global watchers, without forcing
		878	event module detection too early, for example, L<AnyEvent::AIO> creates
		879	and installs the global L<IO::AIO> watcher in a C<post_detect> block to
		880	avoid autodetecting the event module at load time.
652		881
653	If called in scalar or list context, then it creates and returns an object	882	If called in scalar or list context, then it creates and returns an object
654	that automatically removes the callback again when it is destroyed. See	883	that automatically removes the callback again when it is destroyed. See
655	L<Coro::BDB> for a case where this is useful.	884	L<Coro::BDB> for a case where this is useful.
656		885
…		…
659	If there are any code references in this array (you can C<push> to it	888	If there are any code references in this array (you can C<push> to it
660	before or after loading AnyEvent), then they will called directly after	889	before or after loading AnyEvent), then they will called directly after
661	the event loop has been chosen.	890	the event loop has been chosen.
662		891
663	You should check C<$AnyEvent::MODEL> before adding to this array, though:	892	You should check C<$AnyEvent::MODEL> before adding to this array, though:
664	if it contains a true value then the event loop has already been detected,	893	if it is defined then the event loop has already been detected, and the
665	and the array will be ignored.	894	array will be ignored.
666		895
667	Best use C<AnyEvent::post_detect { BLOCK }> instead.	896	Best use C<AnyEvent::post_detect { BLOCK }> when your application allows
		897	it,as it takes care of these details.
		898
		899	This variable is mainly useful for modules that can do something useful
		900	when AnyEvent is used and thus want to know when it is initialised, but do
		901	not need to even load it by default. This array provides the means to hook
		902	into AnyEvent passively, without loading it.
668		903
669	=back	904	=back
670		905
671	=head1 WHAT TO DO IN A MODULE	906	=head1 WHAT TO DO IN A MODULE
672		907
…		…
727		962
728		963
729	=head1 OTHER MODULES	964	=head1 OTHER MODULES
730		965
731	The following is a non-exhaustive list of additional modules that use	966	The following is a non-exhaustive list of additional modules that use
732	AnyEvent and can therefore be mixed easily with other AnyEvent modules	967	AnyEvent as a client and can therefore be mixed easily with other AnyEvent
733	in the same program. Some of the modules come with AnyEvent, some are	968	modules and other event loops in the same program. Some of the modules
734	available via CPAN.	969	come with AnyEvent, most are available via CPAN.
735		970
736	=over 4	971	=over 4
737		972
738	=item L<AnyEvent::Util>	973	=item L<AnyEvent::Util>
739		974
740	Contains various utility functions that replace often-used but blocking	975	Contains various utility functions that replace often-used but blocking
741	functions such as C<inet_aton> by event-/callback-based versions.	976	functions such as C<inet_aton> by event-/callback-based versions.
742
743	=item L<AnyEvent::Handle>
744
745	Provide read and write buffers and manages watchers for reads and writes.
746		977
747	=item L<AnyEvent::Socket>	978	=item L<AnyEvent::Socket>
748		979
749	Provides various utility functions for (internet protocol) sockets,	980	Provides various utility functions for (internet protocol) sockets,
750	addresses and name resolution. Also functions to create non-blocking tcp	981	addresses and name resolution. Also functions to create non-blocking tcp
751	connections or tcp servers, with IPv6 and SRV record support and more.	982	connections or tcp servers, with IPv6 and SRV record support and more.
752		983
		984	=item L<AnyEvent::Handle>
		985
		986	Provide read and write buffers, manages watchers for reads and writes,
		987	supports raw and formatted I/O, I/O queued and fully transparent and
		988	non-blocking SSL/TLS (via L<AnyEvent::TLS>.
		989
753	=item L<AnyEvent::DNS>	990	=item L<AnyEvent::DNS>
754		991
755	Provides rich asynchronous DNS resolver capabilities.	992	Provides rich asynchronous DNS resolver capabilities.
756		993
		994	=item L<AnyEvent::HTTP>
		995
		996	A simple-to-use HTTP library that is capable of making a lot of concurrent
		997	HTTP requests.
		998
757	=item L<AnyEvent::HTTPD>	999	=item L<AnyEvent::HTTPD>
758		1000
759	Provides a simple web application server framework.	1001	Provides a simple web application server framework.
760		1002
761	=item L<AnyEvent::FastPing>	1003	=item L<AnyEvent::FastPing>
762		1004
763	The fastest ping in the west.	1005	The fastest ping in the west.
764		1006
		1007	=item L<AnyEvent::DBI>
		1008
		1009	Executes L<DBI> requests asynchronously in a proxy process.
		1010
		1011	=item L<AnyEvent::AIO>
		1012
		1013	Truly asynchronous I/O, should be in the toolbox of every event
		1014	programmer. AnyEvent::AIO transparently fuses L<IO::AIO> and AnyEvent
		1015	together.
		1016
		1017	=item L<AnyEvent::BDB>
		1018
		1019	Truly asynchronous Berkeley DB access. AnyEvent::BDB transparently fuses
		1020	L<BDB> and AnyEvent together.
		1021
		1022	=item L<AnyEvent::GPSD>
		1023
		1024	A non-blocking interface to gpsd, a daemon delivering GPS information.
		1025
765	=item L<Net::IRC3>	1026	=item L<AnyEvent::IRC>
766		1027
767	AnyEvent based IRC client module family.	1028	AnyEvent based IRC client module family (replacing the older Net::IRC3).
768		1029
769	=item L<Net::XMPP2>	1030	=item L<AnyEvent::XMPP>
770		1031
771	AnyEvent based XMPP (Jabber protocol) module family.	1032	AnyEvent based XMPP (Jabber protocol) module family (replacing the older
		1033	Net::XMPP2>.
		1034
		1035	=item L<AnyEvent::IGS>
		1036
		1037	A non-blocking interface to the Internet Go Server protocol (used by
		1038	L<App::IGS>).
772		1039
773	=item L<Net::FCP>	1040	=item L<Net::FCP>
774		1041
775	AnyEvent-based implementation of the Freenet Client Protocol, birthplace	1042	AnyEvent-based implementation of the Freenet Client Protocol, birthplace
776	of AnyEvent.	1043	of AnyEvent.
…		…
781		1048
782	=item L<Coro>	1049	=item L<Coro>
783		1050
784	Has special support for AnyEvent via L<Coro::AnyEvent>.	1051	Has special support for AnyEvent via L<Coro::AnyEvent>.
785		1052
786	=item L<AnyEvent::AIO>, L<IO::AIO>
787
788	Truly asynchronous I/O, should be in the toolbox of every event
789	programmer. AnyEvent::AIO transparently fuses IO::AIO and AnyEvent
790	together.
791
792	=item L<AnyEvent::BDB>, L<BDB>
793
794	Truly asynchronous Berkeley DB access. AnyEvent::AIO transparently fuses
795	IO::AIO and AnyEvent together.
796
797	=item L<IO::Lambda>
798
799	The lambda approach to I/O - don't ask, look there. Can use AnyEvent.
800
801	=back	1053	=back
802		1054
803	=cut	1055	=cut
804		1056
805	package AnyEvent;	1057	package AnyEvent;
806		1058
		1059	# basically a tuned-down version of common::sense
		1060	sub common_sense {
807	no warnings;	1061	# no warnings
808	use strict;	1062	${^WARNING_BITS} ^= ${^WARNING_BITS};
		1063	# use strict vars subs
		1064	$^H |= 0x00000600;
		1065	}
809		1066
		1067	BEGIN { AnyEvent::common_sense }
		1068
810	use Carp;	1069	use Carp ();
811		1070
812	our $VERSION = 4.11;	1071	our $VERSION = 4.85;
813	our $MODEL;	1072	our $MODEL;
814		1073
815	our $AUTOLOAD;	1074	our $AUTOLOAD;
816	our @ISA;	1075	our @ISA;
817		1076
818	our @REGISTRY;	1077	our @REGISTRY;
819		1078
820	our $WIN32;	1079	our $WIN32;
821		1080
		1081	our $VERBOSE;
		1082
822	BEGIN {	1083	BEGIN {
823	my $win32 = ! ! ($^O =~ /mswin32/i);	1084	eval "sub WIN32(){ " . (($^O =~ /mswin32/i)*1) ." }";
824	eval "sub WIN32(){ $win32 }";	1085	eval "sub TAINT(){ " . (${^TAINT}*1) . " }";
825	}
826		1086
		1087	delete @ENV{grep /^PERL_ANYEVENT_/, keys %ENV}
		1088	if ${^TAINT};
		1089
827	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;	1090	$VERBOSE = $ENV{PERL_ANYEVENT_VERBOSE}*1;
		1091
		1092	}
		1093
		1094	our $MAX_SIGNAL_LATENCY = 10;
828		1095
829	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred	1096	our %PROTOCOL; # (ipv4|ipv6) => (1|2), higher numbers are preferred
830		1097
831	{	1098	{
832	my $idx;	1099	my $idx;
…		…
840	[Event:: => AnyEvent::Impl::Event::],	1107	[Event:: => AnyEvent::Impl::Event::],
841	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],	1108	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
842	# everything below here will not be autoprobed	1109	# everything below here will not be autoprobed
843	# as the pureperl backend should work everywhere	1110	# as the pureperl backend should work everywhere
844	# and is usually faster	1111	# and is usually faster
845	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
846	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers	1112	[Glib:: => AnyEvent::Impl::Glib::], # becomes extremely slow with many watchers
847	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy	1113	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		1114	[Tk:: => AnyEvent::Impl::Tk::], # crashes with many handles
848	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program	1115	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
849	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza	1116	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
850	[Wx:: => AnyEvent::Impl::POE::],	1117	[Wx:: => AnyEvent::Impl::POE::],
851	[Prima:: => AnyEvent::Impl::POE::],	1118	[Prima:: => AnyEvent::Impl::POE::],
		1119	# IO::Async is just too broken - we would need workarounds for its
		1120	# byzantine signal and broken child handling, among others.
		1121	# IO::Async is rather hard to detect, as it doesn't have any
		1122	# obvious default class.
		1123	# [IO::Async:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1124	# [IO::Async::Loop:: => AnyEvent::Impl::IOAsync::], # requires special main program
		1125	# [IO::Async::Notifier:: => AnyEvent::Impl::IOAsync::], # requires special main program
852	);	1126	);
853		1127
854	our %method = map +($_ => 1), qw(io timer time now signal child condvar one_event DESTROY);	1128	our %method = map +($_ => 1),
		1129	qw(io timer time now now_update signal child idle condvar one_event DESTROY);
855		1130
856	our @post_detect;	1131	our @post_detect;
857		1132
858	sub post_detect(&) {	1133	sub post_detect(&) {
859	my ($cb) = @_;	1134	my ($cb) = @_;
…		…
864	1	1139	1
865	} else {	1140	} else {
866	push @post_detect, $cb;	1141	push @post_detect, $cb;
867		1142
868	defined wantarray	1143	defined wantarray
869	? bless \$cb, "AnyEvent::Util::PostDetect"	1144	? bless \$cb, "AnyEvent::Util::postdetect"
870	: ()	1145	: ()
871	}	1146	}
872	}	1147	}
873		1148
874	sub AnyEvent::Util::PostDetect::DESTROY {	1149	sub AnyEvent::Util::postdetect::DESTROY {
875	@post_detect = grep $_ != ${$_[0]}, @post_detect;	1150	@post_detect = grep $_ != ${$_[0]}, @post_detect;
876	}	1151	}
877		1152
878	sub detect() {	1153	sub detect() {
879	unless ($MODEL) {	1154	unless ($MODEL) {
880	no strict 'refs';
881	local $SIG{__DIE__};	1155	local $SIG{__DIE__};
882		1156
883	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {	1157	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
884	my $model = "AnyEvent::Impl::$1";	1158	my $model = "AnyEvent::Impl::$1";
885	if (eval "require $model") {	1159	if (eval "require $model") {
886	$MODEL = $model;	1160	$MODEL = $model;
887	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;	1161	warn "AnyEvent: loaded model '$model' (forced by \$ENV{PERL_ANYEVENT_MODEL}), using it.\n" if $VERBOSE >= 2;
888	} else {	1162	} else {
889	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;	1163	warn "AnyEvent: unable to load model '$model' (from \$ENV{PERL_ANYEVENT_MODEL}):\n$@" if $VERBOSE;
890	}	1164	}
891	}	1165	}
892		1166
893	# check for already loaded models	1167	# check for already loaded models
894	unless ($MODEL) {	1168	unless ($MODEL) {
895	for (@REGISTRY, @models) {	1169	for (@REGISTRY, @models) {
896	my ($package, $model) = @$_;	1170	my ($package, $model) = @$_;
897	if (${"$package\::VERSION"} > 0) {	1171	if (${"$package\::VERSION"} > 0) {
898	if (eval "require $model") {	1172	if (eval "require $model") {
899	$MODEL = $model;	1173	$MODEL = $model;
900	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;	1174	warn "AnyEvent: autodetected model '$model', using it.\n" if $VERBOSE >= 2;
901	last;	1175	last;
902	}	1176	}
903	}	1177	}
904	}	1178	}
905		1179
…		…
910	my ($package, $model) = @$_;	1184	my ($package, $model) = @$_;
911	if (eval "require $package"	1185	if (eval "require $package"
912	and ${"$package\::VERSION"} > 0	1186	and ${"$package\::VERSION"} > 0
913	and eval "require $model") {	1187	and eval "require $model") {
914	$MODEL = $model;	1188	$MODEL = $model;
915	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;	1189	warn "AnyEvent: autoprobed model '$model', using it.\n" if $VERBOSE >= 2;
916	last;	1190	last;
917	}	1191	}
918	}	1192	}
919		1193
920	$MODEL	1194	$MODEL
921	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.";	1195	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV, Event or Glib.\n";
922	}	1196	}
923	}	1197	}
924		1198
		1199	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		1200
925	unshift @ISA, $MODEL;	1201	unshift @ISA, $MODEL;
926	push @{"$MODEL\::ISA"}, "AnyEvent::Base";	1202
		1203	require AnyEvent::Strict if $ENV{PERL_ANYEVENT_STRICT};
927		1204
928	(shift @post_detect)->() while @post_detect;	1205	(shift @post_detect)->() while @post_detect;
929	}	1206	}
930		1207
931	$MODEL	1208	$MODEL
…		…
933		1210
934	sub AUTOLOAD {	1211	sub AUTOLOAD {
935	(my $func = $AUTOLOAD) =~ s/.*://;	1212	(my $func = $AUTOLOAD) =~ s/.*://;
936		1213
937	$method{$func}	1214	$method{$func}
938	or croak "$func: not a valid method for AnyEvent objects";	1215	or Carp::croak "$func: not a valid method for AnyEvent objects";
939		1216
940	detect unless $MODEL;	1217	detect unless $MODEL;
941		1218
942	my $class = shift;	1219	my $class = shift;
943	$class->$func (@_);	1220	$class->$func (@_);
944	}	1221	}
945		1222
		1223	# utility function to dup a filehandle. this is used by many backends
		1224	# to support binding more than one watcher per filehandle (they usually
		1225	# allow only one watcher per fd, so we dup it to get a different one).
		1226	sub _dupfh($$;$$) {
		1227	my ($poll, $fh, $r, $w) = @_;
		1228
		1229	# cygwin requires the fh mode to be matching, unix doesn't
		1230	my ($rw, $mode) = $poll eq "r" ? ($r, "<&") : ($w, ">&");
		1231
		1232	open my $fh2, $mode, $fh
		1233	or die "AnyEvent->io: cannot dup() filehandle in mode '$poll': $!,";
		1234
		1235	# we assume CLOEXEC is already set by perl in all important cases
		1236
		1237	($fh2, $rw)
		1238	}
		1239
946	package AnyEvent::Base;	1240	package AnyEvent::Base;
947		1241
948	# default implementation for now and time	1242	# default implementations for many methods
949		1243
950	use Time::HiRes ();	1244	sub _time {
		1245	# probe for availability of Time::HiRes
		1246	if (eval "use Time::HiRes (); Time::HiRes::time (); 1") {
		1247	warn "AnyEvent: using Time::HiRes for sub-second timing accuracy.\n" if $VERBOSE >= 8;
		1248	*_time = \&Time::HiRes::time;
		1249	# if (eval "use POSIX (); (POSIX::times())...
		1250	} else {
		1251	warn "AnyEvent: using built-in time(), WARNING, no sub-second resolution!\n" if $VERBOSE;
		1252	*_time = sub { time }; # epic fail
		1253	}
951		1254
952	sub time { Time::HiRes::time }	1255	&_time
953	sub now { Time::HiRes::time }	1256	}
		1257
		1258	sub time { _time }
		1259	sub now { _time }
		1260	sub now_update { }
954		1261
955	# default implementation for ->condvar	1262	# default implementation for ->condvar
956		1263
957	sub condvar {	1264	sub condvar {
958	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, AnyEvent::CondVar::	1265	bless { @_ == 3 ? (_ae_cb => $_[2]) : () }, "AnyEvent::CondVar"
959	}	1266	}
960		1267
961	# default implementation for ->signal	1268	# default implementation for ->signal
962		1269
963	our %SIG_CB;	1270	our $HAVE_ASYNC_INTERRUPT;
		1271	our ($SIGPIPE_R, $SIGPIPE_W, %SIG_CB, %SIG_EV, $SIG_IO);
		1272	our (%SIG_ASY, %SIG_ASY_W);
		1273	our ($SIG_COUNT, $SIG_TW);
964		1274
		1275	sub _signal_exec {
		1276	$HAVE_ASYNC_INTERRUPT
		1277	? $SIGPIPE_R->drain
		1278	: sysread $SIGPIPE_R, my $dummy, 9;
		1279
		1280	while (%SIG_EV) {
		1281	for (keys %SIG_EV) {
		1282	delete $SIG_EV{$_};
		1283	$_->() for values %{ $SIG_CB{$_} || {} };
		1284	}
		1285	}
		1286	}
		1287
		1288	# install a dumym wakeupw atcher to reduce signal catching latency
		1289	sub _sig_add() {
		1290	unless ($SIG_COUNT++) {
		1291	# try to align timer on a full-second boundary, if possible
		1292	my $NOW = AnyEvent->now;
		1293
		1294	$SIG_TW = AnyEvent->timer (
		1295	after => $MAX_SIGNAL_LATENCY - ($NOW - int $NOW),
		1296	interval => $MAX_SIGNAL_LATENCY,
		1297	cb => sub { }, # just for the PERL_ASYNC_CHECK
		1298	);
		1299	}
		1300	}
		1301
		1302	sub _sig_del {
		1303	undef $SIG_TW
		1304	unless --$SIG_COUNT;
		1305	}
		1306
965	sub signal {	1307	sub _signal {
966	my (undef, %arg) = @_;	1308	my (undef, %arg) = @_;
967		1309
968	my $signal = uc $arg{signal}	1310	my $signal = uc $arg{signal}
969	or Carp::croak "required option 'signal' is missing";	1311	or Carp::croak "required option 'signal' is missing";
970		1312
971	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};	1313	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		1314
		1315	if ($HAVE_ASYNC_INTERRUPT) {
		1316	# async::interrupt
		1317
		1318	$SIG_ASY{$signal} ||= do {
		1319	my $asy = new Async::Interrupt
		1320	cb => sub { undef $SIG_EV{$signal} },
		1321	signal => $signal,
		1322	pipe => [$SIGPIPE_R->filenos],
		1323	;
		1324	$asy->pipe_autodrain (0);
		1325
		1326	$asy
		1327	};
		1328
		1329	} else {
		1330	# pure perl
		1331
972	$SIG{$signal} ||= sub {	1332	$SIG{$signal} ||= sub {
973	$_->() for values %{ $SIG_CB{$signal} || {} };	1333	local $!;
		1334	syswrite $SIGPIPE_W, "\x00", 1 unless %SIG_EV;
		1335	undef $SIG_EV{$signal};
		1336	};
		1337
		1338	# can't do signal processing without introducing races in pure perl,
		1339	# so limit the signal latency.
		1340	_sig_add;
974	};	1341	}
975		1342
976	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"	1343	bless [$signal, $arg{cb}], "AnyEvent::Base::signal"
977	}	1344	}
978		1345
		1346	sub signal {
		1347	# probe for availability of Async::Interrupt
		1348	if (!$ENV{PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT} && eval "use Async::Interrupt 0.6 (); 1") {
		1349	warn "AnyEvent: using Async::Interrupt for race-free signal handling.\n" if $VERBOSE >= 8;
		1350
		1351	$HAVE_ASYNC_INTERRUPT = 1;
		1352	$SIGPIPE_R = new Async::Interrupt::EventPipe;
		1353	$SIG_IO = AnyEvent->io (fh => $SIGPIPE_R->fileno, poll => "r", cb => \&_signal_exec);
		1354
		1355	} else {
		1356	warn "AnyEvent: using emulated perl signal handling with latency timer.\n" if $VERBOSE >= 8;
		1357
		1358	require Fcntl;
		1359
		1360	if (AnyEvent::WIN32) {
		1361	require AnyEvent::Util;
		1362
		1363	($SIGPIPE_R, $SIGPIPE_W) = AnyEvent::Util::portable_pipe ();
		1364	AnyEvent::Util::fh_nonblocking ($SIGPIPE_R) if $SIGPIPE_R;
		1365	AnyEvent::Util::fh_nonblocking ($SIGPIPE_W) if $SIGPIPE_W; # just in case
		1366	} else {
		1367	pipe $SIGPIPE_R, $SIGPIPE_W;
		1368	fcntl $SIGPIPE_R, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_R;
		1369	fcntl $SIGPIPE_W, &Fcntl::F_SETFL, &Fcntl::O_NONBLOCK if $SIGPIPE_W; # just in case
		1370
		1371	# not strictly required, as $^F is normally 2, but let's make sure...
		1372	fcntl $SIGPIPE_R, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1373	fcntl $SIGPIPE_W, &Fcntl::F_SETFD, &Fcntl::FD_CLOEXEC;
		1374	}
		1375
		1376	$SIGPIPE_R
		1377	or Carp::croak "AnyEvent: unable to create a signal reporting pipe: $!\n";
		1378
		1379	$SIG_IO = AnyEvent->io (fh => $SIGPIPE_R, poll => "r", cb => \&_signal_exec);
		1380	}
		1381
		1382	*signal = \&_signal;
		1383	&signal
		1384	}
		1385
979	sub AnyEvent::Base::Signal::DESTROY {	1386	sub AnyEvent::Base::signal::DESTROY {
980	my ($signal, $cb) = @{$_[0]};	1387	my ($signal, $cb) = @{$_[0]};
981		1388
		1389	_sig_del;
		1390
982	delete $SIG_CB{$signal}{$cb};	1391	delete $SIG_CB{$signal}{$cb};
983		1392
984	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };	1393	$HAVE_ASYNC_INTERRUPT
		1394	? delete $SIG_ASY{$signal}
		1395	: # delete doesn't work with older perls - they then
		1396	# print weird messages, or just unconditionally exit
		1397	# instead of getting the default action.
		1398	undef $SIG{$signal}
		1399	unless keys %{ $SIG_CB{$signal} };
985	}	1400	}
986		1401
987	# default implementation for ->child	1402	# default implementation for ->child
988		1403
989	our %PID_CB;	1404	our %PID_CB;
990	our $CHLD_W;	1405	our $CHLD_W;
991	our $CHLD_DELAY_W;	1406	our $CHLD_DELAY_W;
992	our $PID_IDLE;
993	our $WNOHANG;	1407	our $WNOHANG;
994		1408
995	sub _child_wait {	1409	sub _sigchld {
996	while (0 < (my $pid = waitpid -1, $WNOHANG)) {	1410	while (0 < (my $pid = waitpid -1, $WNOHANG)) {
		1411	$_->($pid, $?)
997	$_->($pid, $?) for (values %{ $PID_CB{$pid} || {} }),	1412	for values %{ $PID_CB{$pid} || {} },
998	(values %{ $PID_CB{0} || {} });	1413	values %{ $PID_CB{0} || {} };
999	}	1414	}
1000
1001	undef $PID_IDLE;
1002	}
1003
1004	sub _sigchld {
1005	# make sure we deliver these changes "synchronous" with the event loop.
1006	$CHLD_DELAY_W ||= AnyEvent->timer (after => 0, cb => sub {
1007	undef $CHLD_DELAY_W;
1008	&_child_wait;
1009	});
1010	}	1415	}
1011		1416
1012	sub child {	1417	sub child {
1013	my (undef, %arg) = @_;	1418	my (undef, %arg) = @_;
1014		1419
1015	defined (my $pid = $arg{pid} + 0)	1420	defined (my $pid = $arg{pid} + 0)
1016	or Carp::croak "required option 'pid' is missing";	1421	or Carp::croak "required option 'pid' is missing";
1017		1422
1018	$PID_CB{$pid}{$arg{cb}} = $arg{cb};	1423	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
1019		1424
1020	unless ($WNOHANG) {	1425	# WNOHANG is almost cetrainly 1 everywhere
		1426	$WNOHANG ||= $^O =~ /^(?:openbsd|netbsd|linux|freebsd|cygwin|MSWin32)$/
		1427	? 1
1021	$WNOHANG = eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;	1428	: eval { local $SIG{__DIE__}; require POSIX; &POSIX::WNOHANG } || 1;
1022	}
1023		1429
1024	unless ($CHLD_W) {	1430	unless ($CHLD_W) {
1025	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);	1431	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
1026	# child could be a zombie already, so make at least one round	1432	# child could be a zombie already, so make at least one round
1027	&_sigchld;	1433	&_sigchld;
1028	}	1434	}
1029		1435
1030	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"	1436	bless [$pid, $arg{cb}], "AnyEvent::Base::child"
1031	}	1437	}
1032		1438
1033	sub AnyEvent::Base::Child::DESTROY {	1439	sub AnyEvent::Base::child::DESTROY {
1034	my ($pid, $cb) = @{$_[0]};	1440	my ($pid, $cb) = @{$_[0]};
1035		1441
1036	delete $PID_CB{$pid}{$cb};	1442	delete $PID_CB{$pid}{$cb};
1037	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };	1443	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
1038		1444
1039	undef $CHLD_W unless keys %PID_CB;	1445	undef $CHLD_W unless keys %PID_CB;
1040	}	1446	}
1041		1447
		1448	# idle emulation is done by simply using a timer, regardless
		1449	# of whether the process is idle or not, and not letting
		1450	# the callback use more than 50% of the time.
		1451	sub idle {
		1452	my (undef, %arg) = @_;
		1453
		1454	my ($cb, $w, $rcb) = $arg{cb};
		1455
		1456	$rcb = sub {
		1457	if ($cb) {
		1458	$w = _time;
		1459	&$cb;
		1460	$w = _time - $w;
		1461
		1462	# never use more then 50% of the time for the idle watcher,
		1463	# within some limits
		1464	$w = 0.0001 if $w < 0.0001;
		1465	$w = 5 if $w > 5;
		1466
		1467	$w = AnyEvent->timer (after => $w, cb => $rcb);
		1468	} else {
		1469	# clean up...
		1470	undef $w;
		1471	undef $rcb;
		1472	}
		1473	};
		1474
		1475	$w = AnyEvent->timer (after => 0.05, cb => $rcb);
		1476
		1477	bless \\$cb, "AnyEvent::Base::idle"
		1478	}
		1479
		1480	sub AnyEvent::Base::idle::DESTROY {
		1481	undef $${$_[0]};
		1482	}
		1483
1042	package AnyEvent::CondVar;	1484	package AnyEvent::CondVar;
1043		1485
1044	our @ISA = AnyEvent::CondVar::Base::;	1486	our @ISA = AnyEvent::CondVar::Base::;
1045		1487
1046	package AnyEvent::CondVar::Base;	1488	package AnyEvent::CondVar::Base;
1047		1489
1048	use overload	1490	#use overload
1049	'&{}' => sub { my $self = shift; sub { $self->send (@_) } },	1491	# '&{}' => sub { my $self = shift; sub { $self->send (@_) } },
1050	fallback => 1;	1492	# fallback => 1;
		1493
		1494	# save 300+ kilobytes by dirtily hardcoding overloading
		1495	${"AnyEvent::CondVar::Base::OVERLOAD"}{dummy}++; # Register with magic by touching.
		1496	*{'AnyEvent::CondVar::Base::()'} = sub { }; # "Make it findable via fetchmethod."
		1497	*{'AnyEvent::CondVar::Base::(&{}'} = sub { my $self = shift; sub { $self->send (@_) } }; # &{}
		1498	${'AnyEvent::CondVar::Base::()'} = 1; # fallback
		1499
		1500	our $WAITING;
1051		1501
1052	sub _send {	1502	sub _send {
1053	# nop	1503	# nop
1054	}	1504	}
1055		1505
…		…
1068	sub ready {	1518	sub ready {
1069	$_[0]{_ae_sent}	1519	$_[0]{_ae_sent}
1070	}	1520	}
1071		1521
1072	sub _wait {	1522	sub _wait {
		1523	$WAITING
		1524	and !$_[0]{_ae_sent}
		1525	and Carp::croak "AnyEvent::CondVar: recursive blocking wait detected";
		1526
		1527	local $WAITING = 1;
1073	AnyEvent->one_event while !$_[0]{_ae_sent};	1528	AnyEvent->one_event while !$_[0]{_ae_sent};
1074	}	1529	}
1075		1530
1076	sub recv {	1531	sub recv {
1077	$_[0]->_wait;	1532	$_[0]->_wait;
…		…
1096	}	1551	}
1097		1552
1098	# undocumented/compatibility with pre-3.4	1553	# undocumented/compatibility with pre-3.4
1099	*broadcast = \&send;	1554	*broadcast = \&send;
1100	*wait = \&_wait;	1555	*wait = \&_wait;
		1556
		1557	=head1 ERROR AND EXCEPTION HANDLING
		1558
		1559	In general, AnyEvent does not do any error handling - it relies on the
		1560	caller to do that if required. The L<AnyEvent::Strict> module (see also
		1561	the C<PERL_ANYEVENT_STRICT> environment variable, below) provides strict
		1562	checking of all AnyEvent methods, however, which is highly useful during
		1563	development.
		1564
		1565	As for exception handling (i.e. runtime errors and exceptions thrown while
		1566	executing a callback), this is not only highly event-loop specific, but
		1567	also not in any way wrapped by this module, as this is the job of the main
		1568	program.
		1569
		1570	The pure perl event loop simply re-throws the exception (usually
		1571	within C<< condvar->recv >>), the L<Event> and L<EV> modules call C<<
		1572	$Event/EV::DIED->() >>, L<Glib> uses C<< install_exception_handler >> and
		1573	so on.
		1574
		1575	=head1 ENVIRONMENT VARIABLES
		1576
		1577	The following environment variables are used by this module or its
		1578	submodules.
		1579
		1580	Note that AnyEvent will remove I<all> environment variables starting with
		1581	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		1582	enabled.
		1583
		1584	=over 4
		1585
		1586	=item C<PERL_ANYEVENT_VERBOSE>
		1587
		1588	By default, AnyEvent will be completely silent except in fatal
		1589	conditions. You can set this environment variable to make AnyEvent more
		1590	talkative.
		1591
		1592	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		1593	conditions, such as not being able to load the event model specified by
		1594	C<PERL_ANYEVENT_MODEL>.
		1595
		1596	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		1597	model it chooses.
		1598
		1599	When set to C<8> or higher, then AnyEvent will report extra information on
		1600	which optional modules it loads and how it implements certain features.
		1601
		1602	=item C<PERL_ANYEVENT_STRICT>
		1603
		1604	AnyEvent does not do much argument checking by default, as thorough
		1605	argument checking is very costly. Setting this variable to a true value
		1606	will cause AnyEvent to load C<AnyEvent::Strict> and then to thoroughly
		1607	check the arguments passed to most method calls. If it finds any problems,
		1608	it will croak.
		1609
		1610	In other words, enables "strict" mode.
		1611
		1612	Unlike C<use strict> (or it's modern cousin, C<< use L<common::sense>
		1613	>>, it is definitely recommended to keep it off in production. Keeping
		1614	C<PERL_ANYEVENT_STRICT=1> in your environment while developing programs
		1615	can be very useful, however.
		1616
		1617	=item C<PERL_ANYEVENT_MODEL>
		1618
		1619	This can be used to specify the event model to be used by AnyEvent, before
		1620	auto detection and -probing kicks in. It must be a string consisting
		1621	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		1622	and the resulting module name is loaded and if the load was successful,
		1623	used as event model. If it fails to load AnyEvent will proceed with
		1624	auto detection and -probing.
		1625
		1626	This functionality might change in future versions.
		1627
		1628	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		1629	could start your program like this:
		1630
		1631	PERL_ANYEVENT_MODEL=Perl perl ...
		1632
		1633	=item C<PERL_ANYEVENT_PROTOCOLS>
		1634
		1635	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
		1636	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
		1637	of auto probing).
		1638
		1639	Must be set to a comma-separated list of protocols or address families,
		1640	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
		1641	used, and preference will be given to protocols mentioned earlier in the
		1642	list.
		1643
		1644	This variable can effectively be used for denial-of-service attacks
		1645	against local programs (e.g. when setuid), although the impact is likely
		1646	small, as the program has to handle conenction and other failures anyways.
		1647
		1648	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
		1649	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
		1650	- only support IPv4, never try to resolve or contact IPv6
		1651	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
		1652	IPv6, but prefer IPv6 over IPv4.
		1653
		1654	=item C<PERL_ANYEVENT_EDNS0>
		1655
		1656	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
		1657	for DNS. This extension is generally useful to reduce DNS traffic, but
		1658	some (broken) firewalls drop such DNS packets, which is why it is off by
		1659	default.
		1660
		1661	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
		1662	EDNS0 in its DNS requests.
		1663
		1664	=item C<PERL_ANYEVENT_MAX_FORKS>
		1665
		1666	The maximum number of child processes that C<AnyEvent::Util::fork_call>
		1667	will create in parallel.
		1668
		1669	=item C<PERL_ANYEVENT_MAX_OUTSTANDING_DNS>
		1670
		1671	The default value for the C<max_outstanding> parameter for the default DNS
		1672	resolver - this is the maximum number of parallel DNS requests that are
		1673	sent to the DNS server.
		1674
		1675	=item C<PERL_ANYEVENT_RESOLV_CONF>
		1676
		1677	The file to use instead of F</etc/resolv.conf> (or OS-specific
		1678	configuration) in the default resolver. When set to the empty string, no
		1679	default config will be used.
		1680
		1681	=item C<PERL_ANYEVENT_CA_FILE>, C<PERL_ANYEVENT_CA_PATH>.
		1682
		1683	When neither C<ca_file> nor C<ca_path> was specified during
		1684	L<AnyEvent::TLS> context creation, and either of these environment
		1685	variables exist, they will be used to specify CA certificate locations
		1686	instead of a system-dependent default.
		1687
		1688	=item C<PERL_ANYEVENT_AVOID_GUARD> and C<PERL_ANYEVENT_AVOID_ASYNC_INTERRUPT>
		1689
		1690	When these are set to C<1>, then the respective modules are not
		1691	loaded. Mostly good for testing AnyEvent itself.
		1692
		1693	=back
1101		1694
1102	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE	1695	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
1103		1696
1104	This is an advanced topic that you do not normally need to use AnyEvent in	1697	This is an advanced topic that you do not normally need to use AnyEvent in
1105	a module. This section is only of use to event loop authors who want to	1698	a module. This section is only of use to event loop authors who want to
…		…
1139		1732
1140	I<rxvt-unicode> also cheats a bit by not providing blocking access to	1733	I<rxvt-unicode> also cheats a bit by not providing blocking access to
1141	condition variables: code blocking while waiting for a condition will	1734	condition variables: code blocking while waiting for a condition will
1142	C<die>. This still works with most modules/usages, and blocking calls must	1735	C<die>. This still works with most modules/usages, and blocking calls must
1143	not be done in an interactive application, so it makes sense.	1736	not be done in an interactive application, so it makes sense.
1144
1145	=head1 ENVIRONMENT VARIABLES
1146
1147	The following environment variables are used by this module:
1148
1149	=over 4
1150
1151	=item C<PERL_ANYEVENT_VERBOSE>
1152
1153	By default, AnyEvent will be completely silent except in fatal
1154	conditions. You can set this environment variable to make AnyEvent more
1155	talkative.
1156
1157	When set to C<1> or higher, causes AnyEvent to warn about unexpected
1158	conditions, such as not being able to load the event model specified by
1159	C<PERL_ANYEVENT_MODEL>.
1160
1161	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
1162	model it chooses.
1163
1164	=item C<PERL_ANYEVENT_MODEL>
1165
1166	This can be used to specify the event model to be used by AnyEvent, before
1167	auto detection and -probing kicks in. It must be a string consisting
1168	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
1169	and the resulting module name is loaded and if the load was successful,
1170	used as event model. If it fails to load AnyEvent will proceed with
1171	auto detection and -probing.
1172
1173	This functionality might change in future versions.
1174
1175	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
1176	could start your program like this:
1177
1178	PERL_ANYEVENT_MODEL=Perl perl ...
1179
1180	=item C<PERL_ANYEVENT_PROTOCOLS>
1181
1182	Used by both L<AnyEvent::DNS> and L<AnyEvent::Socket> to determine preferences
1183	for IPv4 or IPv6. The default is unspecified (and might change, or be the result
1184	of auto probing).
1185
1186	Must be set to a comma-separated list of protocols or address families,
1187	current supported: C<ipv4> and C<ipv6>. Only protocols mentioned will be
1188	used, and preference will be given to protocols mentioned earlier in the
1189	list.
1190
1191	This variable can effectively be used for denial-of-service attacks
1192	against local programs (e.g. when setuid), although the impact is likely
1193	small, as the program has to handle connection errors already-
1194
1195	Examples: C<PERL_ANYEVENT_PROTOCOLS=ipv4,ipv6> - prefer IPv4 over IPv6,
1196	but support both and try to use both. C<PERL_ANYEVENT_PROTOCOLS=ipv4>
1197	- only support IPv4, never try to resolve or contact IPv6
1198	addresses. C<PERL_ANYEVENT_PROTOCOLS=ipv6,ipv4> support either IPv4 or
1199	IPv6, but prefer IPv6 over IPv4.
1200
1201	=item C<PERL_ANYEVENT_EDNS0>
1202
1203	Used by L<AnyEvent::DNS> to decide whether to use the EDNS0 extension
1204	for DNS. This extension is generally useful to reduce DNS traffic, but
1205	some (broken) firewalls drop such DNS packets, which is why it is off by
1206	default.
1207
1208	Setting this variable to C<1> will cause L<AnyEvent::DNS> to announce
1209	EDNS0 in its DNS requests.
1210
1211	=item C<PERL_ANYEVENT_MAX_FORKS>
1212
1213	The maximum number of child processes that C<AnyEvent::Util::fork_call>
1214	will create in parallel.
1215
1216	=back
1217		1737
1218	=head1 EXAMPLE PROGRAM	1738	=head1 EXAMPLE PROGRAM
1219		1739
1220	The following program uses an I/O watcher to read data from STDIN, a timer	1740	The following program uses an I/O watcher to read data from STDIN, a timer
1221	to display a message once per second, and a condition variable to quit the	1741	to display a message once per second, and a condition variable to quit the
…		…
1415	watcher.	1935	watcher.
1416		1936
1417	=head3 Results	1937	=head3 Results
1418		1938
1419	name watchers bytes create invoke destroy comment	1939	name watchers bytes create invoke destroy comment
1420	EV/EV 400000 244 0.56 0.46 0.31 EV native interface	1940	EV/EV 400000 224 0.47 0.35 0.27 EV native interface
1421	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers	1941	EV/Any 100000 224 2.88 0.34 0.27 EV + AnyEvent watchers
1422	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal	1942	CoroEV/Any 100000 224 2.85 0.35 0.28 coroutines + Coro::Signal
1423	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation	1943	Perl/Any 100000 452 4.13 0.73 0.95 pure perl implementation
1424	Event/Event 16000 516 31.88 31.30 0.85 Event native interface	1944	Event/Event 16000 517 32.20 31.80 0.81 Event native interface
1425	Event/Any 16000 590 35.75 31.42 1.08 Event + AnyEvent watchers	1945	Event/Any 16000 590 35.85 31.55 1.06 Event + AnyEvent watchers
		1946	IOAsync/Any 16000 989 38.10 32.77 11.13 via IO::Async::Loop::IO_Poll
		1947	IOAsync/Any 16000 990 37.59 29.50 10.61 via IO::Async::Loop::Epoll
1426	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour	1948	Glib/Any 16000 1357 102.33 12.31 51.00 quadratic behaviour
1427	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers	1949	Tk/Any 2000 1860 27.20 66.31 14.00 SEGV with >> 2000 watchers
1428	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event	1950	POE/Event 2000 6328 109.99 751.67 14.02 via POE::Loop::Event
1429	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select	1951	POE/Select 2000 6027 94.54 809.13 579.80 via POE::Loop::Select
1430		1952
1431	=head3 Discussion	1953	=head3 Discussion
1432		1954
1433	The benchmark does I<not> measure scalability of the event loop very	1955	The benchmark does I<not> measure scalability of the event loop very
1434	well. For example, a select-based event loop (such as the pure perl one)	1956	well. For example, a select-based event loop (such as the pure perl one)
…		…
1459	performance becomes really bad with lots of file descriptors (and few of	1981	performance becomes really bad with lots of file descriptors (and few of
1460	them active), of course, but this was not subject of this benchmark.	1982	them active), of course, but this was not subject of this benchmark.
1461		1983
1462	The C<Event> module has a relatively high setup and callback invocation	1984	The C<Event> module has a relatively high setup and callback invocation
1463	cost, but overall scores in on the third place.	1985	cost, but overall scores in on the third place.
		1986
		1987	C<IO::Async> performs admirably well, about on par with C<Event>, even
		1988	when using its pure perl backend.
1464		1989
1465	C<Glib>'s memory usage is quite a bit higher, but it features a	1990	C<Glib>'s memory usage is quite a bit higher, but it features a
1466	faster callback invocation and overall ends up in the same class as	1991	faster callback invocation and overall ends up in the same class as
1467	C<Event>. However, Glib scales extremely badly, doubling the number of	1992	C<Event>. However, Glib scales extremely badly, doubling the number of
1468	watchers increases the processing time by more than a factor of four,	1993	watchers increases the processing time by more than a factor of four,
…		…
1546	it to another server. This includes deleting the old timeout and creating	2071	it to another server. This includes deleting the old timeout and creating
1547	a new one that moves the timeout into the future.	2072	a new one that moves the timeout into the future.
1548		2073
1549	=head3 Results	2074	=head3 Results
1550		2075
1551	name sockets create request	2076	name sockets create request
1552	EV 20000 69.01 11.16	2077	EV 20000 69.01 11.16
1553	Perl 20000 73.32 35.87	2078	Perl 20000 73.32 35.87
		2079	IOAsync 20000 157.00 98.14 epoll
		2080	IOAsync 20000 159.31 616.06 poll
1554	Event 20000 212.62 257.32	2081	Event 20000 212.62 257.32
1555	Glib 20000 651.16 1896.30	2082	Glib 20000 651.16 1896.30
1556	POE 20000 349.67 12317.24 uses POE::Loop::Event	2083	POE 20000 349.67 12317.24 uses POE::Loop::Event
1557		2084
1558	=head3 Discussion	2085	=head3 Discussion
1559		2086
1560	This benchmark I<does> measure scalability and overall performance of the	2087	This benchmark I<does> measure scalability and overall performance of the
1561	particular event loop.	2088	particular event loop.
…		…
1563	EV is again fastest. Since it is using epoll on my system, the setup time	2090	EV is again fastest. Since it is using epoll on my system, the setup time
1564	is relatively high, though.	2091	is relatively high, though.
1565		2092
1566	Perl surprisingly comes second. It is much faster than the C-based event	2093	Perl surprisingly comes second. It is much faster than the C-based event
1567	loops Event and Glib.	2094	loops Event and Glib.
		2095
		2096	IO::Async performs very well when using its epoll backend, and still quite
		2097	good compared to Glib when using its pure perl backend.
1568		2098
1569	Event suffers from high setup time as well (look at its code and you will	2099	Event suffers from high setup time as well (look at its code and you will
1570	understand why). Callback invocation also has a high overhead compared to	2100	understand why). Callback invocation also has a high overhead compared to
1571	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event	2101	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
1572	uses select or poll in basically all documented configurations.	2102	uses select or poll in basically all documented configurations.
…		…
1635	=item * C-based event loops perform very well with small number of	2165	=item * C-based event loops perform very well with small number of
1636	watchers, as the management overhead dominates.	2166	watchers, as the management overhead dominates.
1637		2167
1638	=back	2168	=back
1639		2169
		2170	=head2 THE IO::Lambda BENCHMARK
		2171
		2172	Recently I was told about the benchmark in the IO::Lambda manpage, which
		2173	could be misinterpreted to make AnyEvent look bad. In fact, the benchmark
		2174	simply compares IO::Lambda with POE, and IO::Lambda looks better (which
		2175	shouldn't come as a surprise to anybody). As such, the benchmark is
		2176	fine, and mostly shows that the AnyEvent backend from IO::Lambda isn't
		2177	very optimal. But how would AnyEvent compare when used without the extra
		2178	baggage? To explore this, I wrote the equivalent benchmark for AnyEvent.
		2179
		2180	The benchmark itself creates an echo-server, and then, for 500 times,
		2181	connects to the echo server, sends a line, waits for the reply, and then
		2182	creates the next connection. This is a rather bad benchmark, as it doesn't
		2183	test the efficiency of the framework or much non-blocking I/O, but it is a
		2184	benchmark nevertheless.
		2185
		2186	name runtime
		2187	Lambda/select 0.330 sec
		2188	+ optimized 0.122 sec
		2189	Lambda/AnyEvent 0.327 sec
		2190	+ optimized 0.138 sec
		2191	Raw sockets/select 0.077 sec
		2192	POE/select, components 0.662 sec
		2193	POE/select, raw sockets 0.226 sec
		2194	POE/select, optimized 0.404 sec
		2195
		2196	AnyEvent/select/nb 0.085 sec
		2197	AnyEvent/EV/nb 0.068 sec
		2198	+state machine 0.134 sec
		2199
		2200	The benchmark is also a bit unfair (my fault): the IO::Lambda/POE
		2201	benchmarks actually make blocking connects and use 100% blocking I/O,
		2202	defeating the purpose of an event-based solution. All of the newly
		2203	written AnyEvent benchmarks use 100% non-blocking connects (using
		2204	AnyEvent::Socket::tcp_connect and the asynchronous pure perl DNS
		2205	resolver), so AnyEvent is at a disadvantage here, as non-blocking connects
		2206	generally require a lot more bookkeeping and event handling than blocking
		2207	connects (which involve a single syscall only).
		2208
		2209	The last AnyEvent benchmark additionally uses L<AnyEvent::Handle>, which
		2210	offers similar expressive power as POE and IO::Lambda, using conventional
		2211	Perl syntax. This means that both the echo server and the client are 100%
		2212	non-blocking, further placing it at a disadvantage.
		2213
		2214	As you can see, the AnyEvent + EV combination even beats the
		2215	hand-optimised "raw sockets benchmark", while AnyEvent + its pure perl
		2216	backend easily beats IO::Lambda and POE.
		2217
		2218	And even the 100% non-blocking version written using the high-level (and
		2219	slow :) L<AnyEvent::Handle> abstraction beats both POE and IO::Lambda by a
		2220	large margin, even though it does all of DNS, tcp-connect and socket I/O
		2221	in a non-blocking way.
		2222
		2223	The two AnyEvent benchmarks programs can be found as F<eg/ae0.pl> and
		2224	F<eg/ae2.pl> in the AnyEvent distribution, the remaining benchmarks are
		2225	part of the IO::lambda distribution and were used without any changes.
		2226
		2227
		2228	=head1 SIGNALS
		2229
		2230	AnyEvent currently installs handlers for these signals:
		2231
		2232	=over 4
		2233
		2234	=item SIGCHLD
		2235
		2236	A handler for C<SIGCHLD> is installed by AnyEvent's child watcher
		2237	emulation for event loops that do not support them natively. Also, some
		2238	event loops install a similar handler.
		2239
		2240	Additionally, when AnyEvent is loaded and SIGCHLD is set to IGNORE, then
		2241	AnyEvent will reset it to default, to avoid losing child exit statuses.
		2242
		2243	=item SIGPIPE
		2244
		2245	A no-op handler is installed for C<SIGPIPE> when C<$SIG{PIPE}> is C<undef>
		2246	when AnyEvent gets loaded.
		2247
		2248	The rationale for this is that AnyEvent users usually do not really depend
		2249	on SIGPIPE delivery (which is purely an optimisation for shell use, or
		2250	badly-written programs), but C<SIGPIPE> can cause spurious and rare
		2251	program exits as a lot of people do not expect C<SIGPIPE> when writing to
		2252	some random socket.
		2253
		2254	The rationale for installing a no-op handler as opposed to ignoring it is
		2255	that this way, the handler will be restored to defaults on exec.
		2256
		2257	Feel free to install your own handler, or reset it to defaults.
		2258
		2259	=back
		2260
		2261	=cut
		2262
		2263	undef $SIG{CHLD}
		2264	if $SIG{CHLD} eq 'IGNORE';
		2265
		2266	$SIG{PIPE} = sub { }
		2267	unless defined $SIG{PIPE};
		2268
		2269	=head1 RECOMMENDED/OPTIONAL MODULES
		2270
		2271	One of AnyEvent's main goals is to be 100% Pure-Perl(tm): only perl (and
		2272	it's built-in modules) are required to use it.
		2273
		2274	That does not mean that AnyEvent won't take advantage of some additional
		2275	modules if they are installed.
		2276
		2277	This section epxlains which additional modules will be used, and how they
		2278	affect AnyEvent's operetion.
		2279
		2280	=over 4
		2281
		2282	=item L<Async::Interrupt>
		2283
		2284	This slightly arcane module is used to implement fast signal handling: To
		2285	my knowledge, there is no way to do completely race-free and quick
		2286	signal handling in pure perl. To ensure that signals still get
		2287	delivered, AnyEvent will start an interval timer to wake up perl (and
		2288	catch the signals) with some delay (default is 10 seconds, look for
		2289	C<$AnyEvent::MAX_SIGNAL_LATENCY>).
		2290
		2291	If this module is available, then it will be used to implement signal
		2292	catching, which means that signals will not be delayed, and the event loop
		2293	will not be interrupted regularly, which is more efficient (And good for
		2294	battery life on laptops).
		2295
		2296	This affects not just the pure-perl event loop, but also other event loops
		2297	that have no signal handling on their own (e.g. Glib, Tk, Qt).
		2298
		2299	Some event loops (POE, Event, Event::Lib) offer signal watchers natively,
		2300	and either employ their own workarounds (POE) or use AnyEvent's workaround
		2301	(using C<$AnyEvent::MAX_SIGNAL_LATENCY>). Installing L<Async::Interrupt>
		2302	does nothing for those backends.
		2303
		2304	=item L<EV>
		2305
		2306	This module isn't really "optional", as it is simply one of the backend
		2307	event loops that AnyEvent can use. However, it is simply the best event
		2308	loop available in terms of features, speed and stability: It supports
		2309	the AnyEvent API optimally, implements all the watcher types in XS, does
		2310	automatic timer adjustments even when no monotonic clock is available,
		2311	can take avdantage of advanced kernel interfaces such as C<epoll> and
		2312	C<kqueue>, and is the fastest backend I<by far>. You can even embed
		2313	L<Glib>/L<Gtk2> in it (or vice versa, see L<EV::Glib> and L<Glib::EV>).
		2314
		2315	=item L<Guard>
		2316
		2317	The guard module, when used, will be used to implement
		2318	C<AnyEvent::Util::guard>. This speeds up guards considerably (and uses a
		2319	lot less memory), but otherwise doesn't affect guard operation much. It is
		2320	purely used for performance.
		2321
		2322	=item L<JSON> and L<JSON::XS>
		2323
		2324	This module is required when you want to read or write JSON data via
		2325	L<AnyEvent::Handle>. It is also written in pure-perl, but can take
		2326	advantage of the ultra-high-speed L<JSON::XS> module when it is installed.
		2327
		2328	In fact, L<AnyEvent::Handle> will use L<JSON::XS> by default if it is
		2329	installed.
		2330
		2331	=item L<Net::SSLeay>
		2332
		2333	Implementing TLS/SSL in Perl is certainly interesting, but not very
		2334	worthwhile: If this module is installed, then L<AnyEvent::Handle> (with
		2335	the help of L<AnyEvent::TLS>), gains the ability to do TLS/SSL.
		2336
		2337	=item L<Time::HiRes>
		2338
		2339	This module is part of perl since release 5.008. It will be used when the
		2340	chosen event library does not come with a timing source on it's own. The
		2341	pure-perl event loop (L<AnyEvent::Impl::Perl>) will additionally use it to
		2342	try to use a monotonic clock for timing stability.
		2343
		2344	=back
		2345
1640		2346
1641	=head1 FORK	2347	=head1 FORK
1642		2348
1643	Most event libraries are not fork-safe. The ones who are usually are	2349	Most event libraries are not fork-safe. The ones who are usually are
1644	because they rely on inefficient but fork-safe C<select> or C<poll>	2350	because they rely on inefficient but fork-safe C<select> or C<poll>
1645	calls. Only L<EV> is fully fork-aware.	2351	calls. Only L<EV> is fully fork-aware.
1646		2352
1647	If you have to fork, you must either do so I<before> creating your first	2353	If you have to fork, you must either do so I<before> creating your first
1648	watcher OR you must not use AnyEvent at all in the child.	2354	watcher OR you must not use AnyEvent at all in the child OR you must do
		2355	something completely out of the scope of AnyEvent.
1649		2356
1650		2357
1651	=head1 SECURITY CONSIDERATIONS	2358	=head1 SECURITY CONSIDERATIONS
1652		2359
1653	AnyEvent can be forced to load any event model via	2360	AnyEvent can be forced to load any event model via
…		…
1658	specified in the variable.	2365	specified in the variable.
1659		2366
1660	You can make AnyEvent completely ignore this variable by deleting it	2367	You can make AnyEvent completely ignore this variable by deleting it
1661	before the first watcher gets created, e.g. with a C<BEGIN> block:	2368	before the first watcher gets created, e.g. with a C<BEGIN> block:
1662		2369
1663	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }	2370	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
1664		2371
1665	use AnyEvent;	2372	use AnyEvent;
1666		2373
1667	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can	2374	Similar considerations apply to $ENV{PERL_ANYEVENT_VERBOSE}, as that can
1668	be used to probe what backend is used and gain other information (which is	2375	be used to probe what backend is used and gain other information (which is
1669	probably even less useful to an attacker than PERL_ANYEVENT_MODEL).	2376	probably even less useful to an attacker than PERL_ANYEVENT_MODEL), and
		2377	$ENV{PERL_ANYEVENT_STRICT}.
		2378
		2379	Note that AnyEvent will remove I<all> environment variables starting with
		2380	C<PERL_ANYEVENT_> from C<%ENV> when it is loaded while taint mode is
		2381	enabled.
		2382
		2383
		2384	=head1 BUGS
		2385
		2386	Perl 5.8 has numerous memleaks that sometimes hit this module and are hard
		2387	to work around. If you suffer from memleaks, first upgrade to Perl 5.10
		2388	and check wether the leaks still show up. (Perl 5.10.0 has other annoying
		2389	memleaks, such as leaking on C<map> and C<grep> but it is usually not as
		2390	pronounced).
1670		2391
1671		2392
1672	=head1 SEE ALSO	2393	=head1 SEE ALSO
1673		2394
1674	Utility functions: L<AnyEvent::Util>.	2395	Utility functions: L<AnyEvent::Util>.
…		…
1677	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.	2398	L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>, L<POE>.
1678		2399
1679	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,	2400	Implementations: L<AnyEvent::Impl::EV>, L<AnyEvent::Impl::Event>,
1680	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,	2401	L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>,
1681	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,	2402	L<AnyEvent::Impl::EventLib>, L<AnyEvent::Impl::Qt>,
1682	L<AnyEvent::Impl::POE>.	2403	L<AnyEvent::Impl::POE>, L<AnyEvent::Impl::IOAsync>.
1683		2404
1684	Non-blocking file handles, sockets, TCP clients and	2405	Non-blocking file handles, sockets, TCP clients and
1685	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>.	2406	servers: L<AnyEvent::Handle>, L<AnyEvent::Socket>, L<AnyEvent::TLS>.
1686		2407
1687	Asynchronous DNS: L<AnyEvent::DNS>.	2408	Asynchronous DNS: L<AnyEvent::DNS>.
1688		2409
1689	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>, L<Coro::Event>,	2410	Coroutine support: L<Coro>, L<Coro::AnyEvent>, L<Coro::EV>,
		2411	L<Coro::Event>,
1690		2412
1691	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>, L<AnyEvent::DNS>.	2413	Nontrivial usage examples: L<AnyEvent::GPSD>, L<AnyEvent::XMPP>,
		2414	L<AnyEvent::HTTP>.
1692		2415
1693		2416
1694	=head1 AUTHOR	2417	=head1 AUTHOR
1695		2418
1696	Marc Lehmann <schmorp@schmorp.de>	2419	Marc Lehmann <schmorp@schmorp.de>
1697	http://home.schmorp.de/	2420	http://home.schmorp.de/
1698		2421
1699	=cut	2422	=cut
1700		2423
1701	1	2424	1
1702		2425

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