[ViewVC] Diff of: cvs/AnyEvent/lib/AnyEvent.pm

Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.2 by root, Thu Dec 1 18:56:18 2005 UTC vs.
Revision 1.94 by root, Sat Apr 26 04:33:51 2008 UTC

…		…
1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent - provide framework for multiple event loops	3	AnyEvent - provide framework for multiple event loops
4		4
5	Event, Coro, Glib, Tk - various supported event loops	5	EV, Event, Coro::EV, Coro::Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event loops
6		6
7	=head1 SYNOPSIS	7	=head1 SYNOPSIS
8		8
9	use AnyEvent;	9	use AnyEvent;
10		10
11	my $w = AnyEvent->timer (fh => ..., poll => "[rw]+", cb => sub {	11	my $w = AnyEvent->io (fh => $fh, poll => "r\|w", cb => sub {
12	my ($poll_got) = @_;
13	...	12	...
14	});	13	});
		14
15	my $w = AnyEvent->io (after => $seconds, cb => sub {	15	my $w = AnyEvent->timer (after => $seconds, cb => sub {
16	...	16	...
17	});	17	});
18		18
19	# watchers get canceled whenever $w is destroyed	19	my $w = AnyEvent->condvar; # stores whether a condition was flagged
20	# only one watcher per $fh and $poll type is allowed
21	# (i.e. on a socket you cna have one r + one w or one rw
22	# watcher, not any more.
23	# timers can only be used once
24
25	my $w = AnyEvent->condvar; # kind of main loop replacement
26	# can only be used once
27	$w->wait; # enters main loop till $condvar gets ->send	20	$w->wait; # enters "main loop" till $condvar gets ->broadcast
28	$w->broadcast; # wake up waiting and future wait's	21	$w->broadcast; # wake up current and all future wait's
		22
		23	=head1 WHY YOU SHOULD USE THIS MODULE (OR NOT)
		24
		25	Glib, POE, IO::Async, Event... CPAN offers event models by the dozen
		26	nowadays. So what is different about AnyEvent?
		27
		28	Executive Summary: AnyEvent is I<compatible>, AnyEvent is I<free of
		29	policy> and AnyEvent is I<small and efficient>.
		30
		31	First and foremost, I<AnyEvent is not an event model> itself, it only
		32	interfaces to whatever event model the main program happens to use in a
		33	pragmatic way. For event models and certain classes of immortals alike,
		34	the statement "there can only be one" is a bitter reality: In general,
		35	only one event loop can be active at the same time in a process. AnyEvent
		36	helps hiding the differences between those event loops.
		37
		38	The goal of AnyEvent is to offer module authors the ability to do event
		39	programming (waiting for I/O or timer events) without subscribing to a
		40	religion, a way of living, and most importantly: without forcing your
		41	module users into the same thing by forcing them to use the same event
		42	model you use.
		43
		44	For modules like POE or IO::Async (which is a total misnomer as it is
		45	actually doing all I/O I<synchronously>...), using them in your module is
		46	like joining a cult: After you joined, you are dependent on them and you
		47	cannot use anything else, as it is simply incompatible to everything that
		48	isn't itself. What's worse, all the potential users of your module are
		49	I<also> forced to use the same event loop you use.
		50
		51	AnyEvent is different: AnyEvent + POE works fine. AnyEvent + Glib works
		52	fine. AnyEvent + Tk works fine etc. etc. but none of these work together
		53	with the rest: POE + IO::Async? no go. Tk + Event? no go. Again: if
		54	your module uses one of those, every user of your module has to use it,
		55	too. But if your module uses AnyEvent, it works transparently with all
		56	event models it supports (including stuff like POE and IO::Async, as long
		57	as those use one of the supported event loops. It is trivial to add new
		58	event loops to AnyEvent, too, so it is future-proof).
		59
		60	In addition to being free of having to use I<the one and only true event
		61	model>, AnyEvent also is free of bloat and policy: with POE or similar
		62	modules, you get an enourmous amount of code and strict rules you have to
		63	follow. AnyEvent, on the other hand, is lean and up to the point, by only
		64	offering the functionality that is necessary, in as thin as a wrapper as
		65	technically possible.
		66
		67	Of course, if you want lots of policy (this can arguably be somewhat
		68	useful) and you want to force your users to use the one and only event
		69	model, you should I<not> use this module.
		70
29		71
30	=head1 DESCRIPTION	72	=head1 DESCRIPTION
31		73
32	L<AnyEvent> provides an identical interface to multiple event loops. This	74	L<AnyEvent> provides an identical interface to multiple event loops. This
33	allows module authors to utilizy an event loop without forcing module	75	allows module authors to utilise an event loop without forcing module
34	users to use the same event loop (as only a single event loop can coexist	76	users to use the same event loop (as only a single event loop can coexist
35	peacefully at any one time).	77	peacefully at any one time).
36		78
37	The interface itself is vaguely similar but not identical to the Event	79	The interface itself is vaguely similar, but not identical to the L<Event>
38	module.	80	module.
39		81
40	On the first call of any method, the module tries to detect the currently	82	During the first call of any watcher-creation method, the module tries
41	loaded event loop by probing wether any of the following modules is	83	to detect the currently loaded event loop by probing whether one of the
42	loaded: L<Coro::Event>, L<Event>, L<Glib>, L<Tk>. The first one found is	84	following modules is already loaded: L<Coro::EV>, L<Coro::Event>, L<EV>,
43	used. If none is found, the module tries to load these modules in the	85	L<Event>, L<Glib>, L<AnyEvent::Impl::Perl>, L<Tk>, L<Event::Lib>, L<Qt>,
44	order given. The first one that could be successfully loaded will be	86	L<POE>. The first one found is used. If none are found, the module tries
45	used. If still none could be found, it will issue an error.	87	to load these modules (excluding Tk, Event::Lib, Qt and POE as the pure perl
		88	adaptor should always succeed) in the order given. The first one that can
		89	be successfully loaded will be used. If, after this, still none could be
		90	found, AnyEvent will fall back to a pure-perl event loop, which is not
		91	very efficient, but should work everywhere.
		92
		93	Because AnyEvent first checks for modules that are already loaded, loading
		94	an event model explicitly before first using AnyEvent will likely make
		95	that model the default. For example:
		96
		97	use Tk;
		98	use AnyEvent;
		99
		100	# .. AnyEvent will likely default to Tk
		101
		102	The I<likely> means that, if any module loads another event model and
		103	starts using it, all bets are off. Maybe you should tell their authors to
		104	use AnyEvent so their modules work together with others seamlessly...
		105
		106	The pure-perl implementation of AnyEvent is called
		107	C<AnyEvent::Impl::Perl>. Like other event modules you can load it
		108	explicitly.
		109
		110	=head1 WATCHERS
		111
		112	AnyEvent has the central concept of a I<watcher>, which is an object that
		113	stores relevant data for each kind of event you are waiting for, such as
		114	the callback to call, the filehandle to watch, etc.
		115
		116	These watchers are normal Perl objects with normal Perl lifetime. After
		117	creating a watcher it will immediately "watch" for events and invoke the
		118	callback when the event occurs (of course, only when the event model
		119	is in control).
		120
		121	To disable the watcher you have to destroy it (e.g. by setting the
		122	variable you store it in to C<undef> or otherwise deleting all references
		123	to it).
		124
		125	All watchers are created by calling a method on the C<AnyEvent> class.
		126
		127	Many watchers either are used with "recursion" (repeating timers for
		128	example), or need to refer to their watcher object in other ways.
		129
		130	An any way to achieve that is this pattern:
		131
		132	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
		133	# you can use $w here, for example to undef it
		134	undef $w;
		135	});
		136
		137	Note that C<my $w; $w => combination. This is necessary because in Perl,
		138	my variables are only visible after the statement in which they are
		139	declared.
		140
		141	=head2 I/O WATCHERS
		142
		143	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
		144	with the following mandatory key-value pairs as arguments:
		145
		146	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch
		147	for events. C<poll> must be a string that is either C<r> or C<w>,
		148	which creates a watcher waiting for "r"eadable or "w"ritable events,
		149	respectively. C<cb> is the callback to invoke each time the file handle
		150	becomes ready.
		151
		152	Although the callback might get passed parameters, their value and
		153	presence is undefined and you cannot rely on them. Portable AnyEvent
		154	callbacks cannot use arguments passed to I/O watcher callbacks.
		155
		156	The I/O watcher might use the underlying file descriptor or a copy of it.
		157	You must not close a file handle as long as any watcher is active on the
		158	underlying file descriptor.
		159
		160	Some event loops issue spurious readyness notifications, so you should
		161	always use non-blocking calls when reading/writing from/to your file
		162	handles.
		163
		164	Example:
		165
		166	# wait for readability of STDIN, then read a line and disable the watcher
		167	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		168	chomp (my $input = <STDIN>);
		169	warn "read: $input\n";
		170	undef $w;
		171	});
		172
		173	=head2 TIME WATCHERS
		174
		175	You can create a time watcher by calling the C<< AnyEvent->timer >>
		176	method with the following mandatory arguments:
		177
		178	C<after> specifies after how many seconds (fractional values are
		179	supported) the callback should be invoked. C<cb> is the callback to invoke
		180	in that case.
		181
		182	Although the callback might get passed parameters, their value and
		183	presence is undefined and you cannot rely on them. Portable AnyEvent
		184	callbacks cannot use arguments passed to time watcher callbacks.
		185
		186	The timer callback will be invoked at most once: if you want a repeating
		187	timer you have to create a new watcher (this is a limitation by both Tk
		188	and Glib).
		189
		190	Example:
		191
		192	# fire an event after 7.7 seconds
		193	my $w = AnyEvent->timer (after => 7.7, cb => sub {
		194	warn "timeout\n";
		195	});
		196
		197	# to cancel the timer:
		198	undef $w;
		199
		200	Example 2:
		201
		202	# fire an event after 0.5 seconds, then roughly every second
		203	my $w;
		204
		205	my $cb = sub {
		206	# cancel the old timer while creating a new one
		207	$w = AnyEvent->timer (after => 1, cb => $cb);
		208	};
		209
		210	# start the "loop" by creating the first watcher
		211	$w = AnyEvent->timer (after => 0.5, cb => $cb);
		212
		213	=head3 TIMING ISSUES
		214
		215	There are two ways to handle timers: based on real time (relative, "fire
		216	in 10 seconds") and based on wallclock time (absolute, "fire at 12
		217	o'clock").
		218
		219	While most event loops expect timers to specified in a relative way, they
		220	use absolute time internally. This makes a difference when your clock
		221	"jumps", for example, when ntp decides to set your clock backwards from
		222	the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to
		223	fire "after" a second might actually take six years to finally fire.
		224
		225	AnyEvent cannot compensate for this. The only event loop that is conscious
		226	about these issues is L<EV>, which offers both relative (ev_timer, based
		227	on true relative time) and absolute (ev_periodic, based on wallclock time)
		228	timers.
		229
		230	AnyEvent always prefers relative timers, if available, matching the
		231	AnyEvent API.
		232
		233	=head2 SIGNAL WATCHERS
		234
		235	You can watch for signals using a signal watcher, C<signal> is the signal
		236	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to
		237	be invoked whenever a signal occurs.
		238
		239	Although the callback might get passed parameters, their value and
		240	presence is undefined and you cannot rely on them. Portable AnyEvent
		241	callbacks cannot use arguments passed to signal watcher callbacks.
		242
		243	Multiple signal occurances can be clumped together into one callback
		244	invocation, and callback invocation will be synchronous. synchronous means
		245	that it might take a while until the signal gets handled by the process,
		246	but it is guarenteed not to interrupt any other callbacks.
		247
		248	The main advantage of using these watchers is that you can share a signal
		249	between multiple watchers.
		250
		251	This watcher might use C<%SIG>, so programs overwriting those signals
		252	directly will likely not work correctly.
		253
		254	Example: exit on SIGINT
		255
		256	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
		257
		258	=head2 CHILD PROCESS WATCHERS
		259
		260	You can also watch on a child process exit and catch its exit status.
		261
		262	The child process is specified by the C<pid> argument (if set to C<0>, it
		263	watches for any child process exit). The watcher will trigger as often
		264	as status change for the child are received. This works by installing a
		265	signal handler for C<SIGCHLD>. The callback will be called with the pid
		266	and exit status (as returned by waitpid), so unlike other watcher types,
		267	you I<can> rely on child watcher callback arguments.
		268
		269	There is a slight catch to child watchers, however: you usually start them
		270	I<after> the child process was created, and this means the process could
		271	have exited already (and no SIGCHLD will be sent anymore).
		272
		273	Not all event models handle this correctly (POE doesn't), but even for
		274	event models that I<do> handle this correctly, they usually need to be
		275	loaded before the process exits (i.e. before you fork in the first place).
		276
		277	This means you cannot create a child watcher as the very first thing in an
		278	AnyEvent program, you I<have> to create at least one watcher before you
		279	C<fork> the child (alternatively, you can call C<AnyEvent::detect>).
		280
		281	Example: fork a process and wait for it
		282
		283	my $done = AnyEvent->condvar;
		284
		285	AnyEvent::detect; # force event module to be initialised
		286
		287	my $pid = fork or exit 5;
		288
		289	my $w = AnyEvent->child (
		290	pid => $pid,
		291	cb => sub {
		292	my ($pid, $status) = @_;
		293	warn "pid $pid exited with status $status";
		294	$done->broadcast;
		295	},
		296	);
		297
		298	# do something else, then wait for process exit
		299	$done->wait;
		300
		301	=head2 CONDITION VARIABLES
		302
		303	Condition variables can be created by calling the C<< AnyEvent->condvar >>
		304	method without any arguments.
		305
		306	A condition variable waits for a condition - precisely that the C<<
		307	->broadcast >> method has been called.
		308
		309	They are very useful to signal that a condition has been fulfilled, for
		310	example, if you write a module that does asynchronous http requests,
		311	then a condition variable would be the ideal candidate to signal the
		312	availability of results.
		313
		314	You can also use condition variables to block your main program until
		315	an event occurs - for example, you could C<< ->wait >> in your main
		316	program until the user clicks the Quit button in your app, which would C<<
		317	->broadcast >> the "quit" event.
		318
		319	Note that condition variables recurse into the event loop - if you have
		320	two pirces of code that call C<< ->wait >> in a round-robbin fashion, you
		321	lose. Therefore, condition variables are good to export to your caller, but
		322	you should avoid making a blocking wait yourself, at least in callbacks,
		323	as this asks for trouble.
		324
		325	This object has two methods:
46		326
47	=over 4	327	=over 4
48		328
		329	=item $cv->wait
		330
		331	Wait (blocking if necessary) until the C<< ->broadcast >> method has been
		332	called on c<$cv>, while servicing other watchers normally.
		333
		334	You can only wait once on a condition - additional calls will return
		335	immediately.
		336
		337	Not all event models support a blocking wait - some die in that case
		338	(programs might want to do that to stay interactive), so I<if you are
		339	using this from a module, never require a blocking wait>, but let the
		340	caller decide whether the call will block or not (for example, by coupling
		341	condition variables with some kind of request results and supporting
		342	callbacks so the caller knows that getting the result will not block,
		343	while still suppporting blocking waits if the caller so desires).
		344
		345	Another reason I<never> to C<< ->wait >> in a module is that you cannot
		346	sensibly have two C<< ->wait >>'s in parallel, as that would require
		347	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
		348	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and
		349	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
		350	from different coroutines, however).
		351
		352	=item $cv->broadcast
		353
		354	Flag the condition as ready - a running C<< ->wait >> and all further
		355	calls to C<wait> will (eventually) return after this method has been
		356	called. If nobody is waiting the broadcast will be remembered..
		357
		358	=back
		359
		360	Example:
		361
		362	# wait till the result is ready
		363	my $result_ready = AnyEvent->condvar;
		364
		365	# do something such as adding a timer
		366	# or socket watcher the calls $result_ready->broadcast
		367	# when the "result" is ready.
		368	# in this case, we simply use a timer:
		369	my $w = AnyEvent->timer (
		370	after => 1,
		371	cb => sub { $result_ready->broadcast },
		372	);
		373
		374	# this "blocks" (while handling events) till the watcher
		375	# calls broadcast
		376	$result_ready->wait;
		377
		378	=head1 GLOBAL VARIABLES AND FUNCTIONS
		379
		380	=over 4
		381
		382	=item $AnyEvent::MODEL
		383
		384	Contains C<undef> until the first watcher is being created. Then it
		385	contains the event model that is being used, which is the name of the
		386	Perl class implementing the model. This class is usually one of the
		387	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case
		388	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).
		389
		390	The known classes so far are:
		391
		392	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
		393	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
		394	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
		395	AnyEvent::Impl::Event based on Event, second best choice.
		396	AnyEvent::Impl::Glib based on Glib, third-best choice.
		397	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
		398	AnyEvent::Impl::Tk based on Tk, very bad choice.
		399	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
		400	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		401	AnyEvent::Impl::POE based on POE, not generic enough for full support.
		402
		403	There is no support for WxWidgets, as WxWidgets has no support for
		404	watching file handles. However, you can use WxWidgets through the
		405	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
		406	second, which was considered to be too horrible to even consider for
		407	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
		408	it's adaptor.
		409
		410	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
		411	autodetecting them.
		412
		413	=item AnyEvent::detect
		414
		415	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
		416	if necessary. You should only call this function right before you would
		417	have created an AnyEvent watcher anyway, that is, as late as possible at
		418	runtime.
		419
		420	=back
		421
		422	=head1 WHAT TO DO IN A MODULE
		423
		424	As a module author, you should C<use AnyEvent> and call AnyEvent methods
		425	freely, but you should not load a specific event module or rely on it.
		426
		427	Be careful when you create watchers in the module body - AnyEvent will
		428	decide which event module to use as soon as the first method is called, so
		429	by calling AnyEvent in your module body you force the user of your module
		430	to load the event module first.
		431
		432	Never call C<< ->wait >> on a condition variable unless you I<know> that
		433	the C<< ->broadcast >> method has been called on it already. This is
		434	because it will stall the whole program, and the whole point of using
		435	events is to stay interactive.
		436
		437	It is fine, however, to call C<< ->wait >> when the user of your module
		438	requests it (i.e. if you create a http request object ad have a method
		439	called C<results> that returns the results, it should call C<< ->wait >>
		440	freely, as the user of your module knows what she is doing. always).
		441
		442	=head1 WHAT TO DO IN THE MAIN PROGRAM
		443
		444	There will always be a single main program - the only place that should
		445	dictate which event model to use.
		446
		447	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
		448	do anything special (it does not need to be event-based) and let AnyEvent
		449	decide which implementation to chose if some module relies on it.
		450
		451	If the main program relies on a specific event model. For example, in
		452	Gtk2 programs you have to rely on the Glib module. You should load the
		453	event module before loading AnyEvent or any module that uses it: generally
		454	speaking, you should load it as early as possible. The reason is that
		455	modules might create watchers when they are loaded, and AnyEvent will
		456	decide on the event model to use as soon as it creates watchers, and it
		457	might chose the wrong one unless you load the correct one yourself.
		458
		459	You can chose to use a rather inefficient pure-perl implementation by
		460	loading the C<AnyEvent::Impl::Perl> module, which gives you similar
		461	behaviour everywhere, but letting AnyEvent chose is generally better.
		462
49	=cut	463	=cut
50		464
51	package AnyEvent;	465	package AnyEvent;
52		466
53	no warnings;	467	no warnings;
54	use strict 'vars';	468	use strict;
		469
55	use Carp;	470	use Carp;
56		471
57	our $VERSION = 0.1;	472	our $VERSION = '3.3';
58	our $MODEL;	473	our $MODEL;
59		474
60	our $AUTOLOAD;	475	our $AUTOLOAD;
61	our @ISA;	476	our @ISA;
62		477
		478	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
		479
		480	our @REGISTRY;
		481
63	my @models = (	482	my @models = (
64	[Coro => Coro::Event::],	483	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
65	[Event => Event::],	484	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
66	[Glib => Glib::],	485	[EV:: => AnyEvent::Impl::EV::],
67	[Tk => Tk::],	486	[Event:: => AnyEvent::Impl::Event::],
		487	[Glib:: => AnyEvent::Impl::Glib::],
		488	[Tk:: => AnyEvent::Impl::Tk::],
		489	[Wx:: => AnyEvent::Impl::POE::],
		490	[Prima:: => AnyEvent::Impl::POE::],
		491	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
		492	# everything below here will not be autoprobed as the pureperl backend should work everywhere
		493	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		494	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		495	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
68	);	496	);
69		497
70	sub AUTOLOAD {	498	our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);
71	$AUTOLOAD =~ s/.*://;
72		499
		500	sub detect() {
73	unless ($MODEL) {	501	unless ($MODEL) {
74	# check for already loaded models	502	no strict 'refs';
75	for (@models) {
76	my ($model, $package) = @$_;
77	if (scalar keys %{ *{"$package\::"} }) {
78	eval "require AnyEvent::Impl::$model"
79	or die;
80		503
81	last if $MODEL;	504	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
		505	my $model = "AnyEvent::Impl::$1";
		506	if (eval "require $model") {
		507	$MODEL = $model;
		508	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;
		509	} else {
		510	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;
82	}	511	}
83	}	512	}
84		513
		514	# check for already loaded models
85	unless ($MODEL) {	515	unless ($MODEL) {
86	# try to load a model
87
88	for (@models) {	516	for (@REGISTRY, @models) {
89	my ($model, $package) = @$_;	517	my ($package, $model) = @$_;
90	eval "require AnyEvent::Impl::$model"	518	if (${"$package\::VERSION"} > 0) {
		519	if (eval "require $model") {
		520	$MODEL = $model;
		521	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;
		522	last;
91	or die;	523	}
92		524	}
93	last if $MODEL;
94	}	525	}
95		526
		527	unless ($MODEL) {
		528	# try to load a model
		529
		530	for (@REGISTRY, @models) {
		531	my ($package, $model) = @$_;
		532	if (eval "require $package"
		533	and ${"$package\::VERSION"} > 0
		534	and eval "require $model") {
		535	$MODEL = $model;
		536	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;
		537	last;
		538	}
		539	}
		540
96	$MODEL	541	$MODEL
97	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: Coro, Event, Glib or Tk.";	542	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: EV (or Coro+EV), Event (or Coro+Event) or Glib.";
		543	}
98	}	544	}
		545
		546	unshift @ISA, $MODEL;
		547	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
99	}	548	}
100		549
101	@ISA = $MODEL;	550	$MODEL
		551	}
		552
		553	sub AUTOLOAD {
		554	(my $func = $AUTOLOAD) =~ s/.*://;
		555
		556	$method{$func}
		557	or croak "$func: not a valid method for AnyEvent objects";
		558
		559	detect unless $MODEL;
102		560
103	my $class = shift;	561	my $class = shift;
104	$class->$AUTOLOAD (@_);	562	$class->$func (@_);
105	}	563	}
106		564
		565	package AnyEvent::Base;
		566
		567	# default implementation for ->condvar, ->wait, ->broadcast
		568
		569	sub condvar {
		570	bless \my $flag, "AnyEvent::Base::CondVar"
		571	}
		572
		573	sub AnyEvent::Base::CondVar::broadcast {
		574	${$_[0]}++;
		575	}
		576
		577	sub AnyEvent::Base::CondVar::wait {
		578	AnyEvent->one_event while !${$_[0]};
		579	}
		580
		581	# default implementation for ->signal
		582
		583	our %SIG_CB;
		584
		585	sub signal {
		586	my (undef, %arg) = @_;
		587
		588	my $signal = uc $arg{signal}
		589	or Carp::croak "required option 'signal' is missing";
		590
		591	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		592	$SIG{$signal} \|\|= sub {
		593	$_->() for values %{ $SIG_CB{$signal} \|\| {} };
		594	};
		595
		596	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"
		597	}
		598
		599	sub AnyEvent::Base::Signal::DESTROY {
		600	my ($signal, $cb) = @{$_[0]};
		601
		602	delete $SIG_CB{$signal}{$cb};
		603
		604	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };
		605	}
		606
		607	# default implementation for ->child
		608
		609	our %PID_CB;
		610	our $CHLD_W;
		611	our $CHLD_DELAY_W;
		612	our $PID_IDLE;
		613	our $WNOHANG;
		614
		615	sub _child_wait {
		616	while (0 < (my $pid = waitpid -1, $WNOHANG)) {
		617	$_->($pid, $?) for (values %{ $PID_CB{$pid} \|\| {} }),
		618	(values %{ $PID_CB{0} \|\| {} });
		619	}
		620
		621	undef $PID_IDLE;
		622	}
		623
		624	sub _sigchld {
		625	# make sure we deliver these changes "synchronous" with the event loop.
		626	$CHLD_DELAY_W \|\|= AnyEvent->timer (after => 0, cb => sub {
		627	undef $CHLD_DELAY_W;
		628	&_child_wait;
		629	});
		630	}
		631
		632	sub child {
		633	my (undef, %arg) = @_;
		634
		635	defined (my $pid = $arg{pid} + 0)
		636	or Carp::croak "required option 'pid' is missing";
		637
		638	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
		639
		640	unless ($WNOHANG) {
		641	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } \|\| 1;
		642	}
		643
		644	unless ($CHLD_W) {
		645	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
		646	# child could be a zombie already, so make at least one round
		647	&_sigchld;
		648	}
		649
		650	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"
		651	}
		652
		653	sub AnyEvent::Base::Child::DESTROY {
		654	my ($pid, $cb) = @{$_[0]};
		655
		656	delete $PID_CB{$pid}{$cb};
		657	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
		658
		659	undef $CHLD_W unless keys %PID_CB;
		660	}
		661
		662	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
		663
		664	This is an advanced topic that you do not normally need to use AnyEvent in
		665	a module. This section is only of use to event loop authors who want to
		666	provide AnyEvent compatibility.
		667
		668	If you need to support another event library which isn't directly
		669	supported by AnyEvent, you can supply your own interface to it by
		670	pushing, before the first watcher gets created, the package name of
		671	the event module and the package name of the interface to use onto
		672	C<@AnyEvent::REGISTRY>. You can do that before and even without loading
		673	AnyEvent, so it is reasonably cheap.
		674
		675	Example:
		676
		677	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
		678
		679	This tells AnyEvent to (literally) use the C<urxvt::anyevent::>
		680	package/class when it finds the C<urxvt> package/module is already loaded.
		681
		682	When AnyEvent is loaded and asked to find a suitable event model, it
		683	will first check for the presence of urxvt by trying to C<use> the
		684	C<urxvt::anyevent> module.
		685
		686	The class should provide implementations for all watcher types. See
		687	L<AnyEvent::Impl::EV> (source code), L<AnyEvent::Impl::Glib> (Source code)
		688	and so on for actual examples. Use C<perldoc -m AnyEvent::Impl::Glib> to
		689	see the sources.
		690
		691	If you don't provide C<signal> and C<child> watchers than AnyEvent will
		692	provide suitable (hopefully) replacements.
		693
		694	The above example isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt)
		695	terminal emulator uses the above line as-is. An interface isn't included
		696	in AnyEvent because it doesn't make sense outside the embedded interpreter
		697	inside I<rxvt-unicode>, and it is updated and maintained as part of the
		698	I<rxvt-unicode> distribution.
		699
		700	I<rxvt-unicode> also cheats a bit by not providing blocking access to
		701	condition variables: code blocking while waiting for a condition will
		702	C<die>. This still works with most modules/usages, and blocking calls must
		703	not be done in an interactive application, so it makes sense.
		704
		705	=head1 ENVIRONMENT VARIABLES
		706
		707	The following environment variables are used by this module:
		708
		709	=over 4
		710
		711	=item C<PERL_ANYEVENT_VERBOSE>
		712
		713	By default, AnyEvent will be completely silent except in fatal
		714	conditions. You can set this environment variable to make AnyEvent more
		715	talkative.
		716
		717	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		718	conditions, such as not being able to load the event model specified by
		719	C<PERL_ANYEVENT_MODEL>.
		720
		721	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		722	model it chooses.
		723
		724	=item C<PERL_ANYEVENT_MODEL>
		725
		726	This can be used to specify the event model to be used by AnyEvent, before
		727	autodetection and -probing kicks in. It must be a string consisting
		728	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		729	and the resulting module name is loaded and if the load was successful,
		730	used as event model. If it fails to load AnyEvent will proceed with
		731	autodetection and -probing.
		732
		733	This functionality might change in future versions.
		734
		735	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		736	could start your program like this:
		737
		738	PERL_ANYEVENT_MODEL=Perl perl ...
		739
107	=back	740	=back
108		741
109	=head1 EXAMPLE	742	=head1 EXAMPLE PROGRAM
110		743
111	The following program uses an io watcher to read data from stdin, a timer	744	The following program uses an I/O watcher to read data from STDIN, a timer
112	to display a message once per second, and a condvar to exit the program	745	to display a message once per second, and a condition variable to quit the
113	when the user enters quit:	746	program when the user enters quit:
114		747
115	use AnyEvent;	748	use AnyEvent;
116		749
117	my $cv = AnyEvent->condvar;	750	my $cv = AnyEvent->condvar;
118		751
119	my $io_watcher = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	752	my $io_watcher = AnyEvent->io (
		753	fh => \*STDIN,
		754	poll => 'r',
		755	cb => sub {
120	warn "io event <$_[0]>\n"; # will always output <r>	756	warn "io event <$_[0]>\n"; # will always output <r>
121	chomp (my $input = <STDIN>); # read a line	757	chomp (my $input = <STDIN>); # read a line
122	warn "read: $input\n"; # output what has been read	758	warn "read: $input\n"; # output what has been read
123	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	759	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i
		760	},
124	});	761	);
125		762
126	my $time_watcher; # can only be used once	763	my $time_watcher; # can only be used once
127		764
128	sub new_timer {	765	sub new_timer {
129	$timer = AnyEvent->timer (after => 1, cb => sub {	766	$timer = AnyEvent->timer (after => 1, cb => sub {
134		771
135	new_timer; # create first timer	772	new_timer; # create first timer
136		773
137	$cv->wait; # wait until user enters /^q/i	774	$cv->wait; # wait until user enters /^q/i
138		775
		776	=head1 REAL-WORLD EXAMPLE
		777
		778	Consider the L<Net::FCP> module. It features (among others) the following
		779	API calls, which are to freenet what HTTP GET requests are to http:
		780
		781	my $data = $fcp->client_get ($url); # blocks
		782
		783	my $transaction = $fcp->txn_client_get ($url); # does not block
		784	$transaction->cb ( sub { ... } ); # set optional result callback
		785	my $data = $transaction->result; # possibly blocks
		786
		787	The C<client_get> method works like C<LWP::Simple::get>: it requests the
		788	given URL and waits till the data has arrived. It is defined to be:
		789
		790	sub client_get { $_[0]->txn_client_get ($_[1])->result }
		791
		792	And in fact is automatically generated. This is the blocking API of
		793	L<Net::FCP>, and it works as simple as in any other, similar, module.
		794
		795	More complicated is C<txn_client_get>: It only creates a transaction
		796	(completion, result, ...) object and initiates the transaction.
		797
		798	my $txn = bless { }, Net::FCP::Txn::;
		799
		800	It also creates a condition variable that is used to signal the completion
		801	of the request:
		802
		803	$txn->{finished} = AnyAvent->condvar;
		804
		805	It then creates a socket in non-blocking mode.
		806
		807	socket $txn->{fh}, ...;
		808	fcntl $txn->{fh}, F_SETFL, O_NONBLOCK;
		809	connect $txn->{fh}, ...
		810	and !$!{EWOULDBLOCK}
		811	and !$!{EINPROGRESS}
		812	and Carp::croak "unable to connect: $!\n";
		813
		814	Then it creates a write-watcher which gets called whenever an error occurs
		815	or the connection succeeds:
		816
		817	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'w', cb => sub { $txn->fh_ready_w });
		818
		819	And returns this transaction object. The C<fh_ready_w> callback gets
		820	called as soon as the event loop detects that the socket is ready for
		821	writing.
		822
		823	The C<fh_ready_w> method makes the socket blocking again, writes the
		824	request data and replaces the watcher by a read watcher (waiting for reply
		825	data). The actual code is more complicated, but that doesn't matter for
		826	this example:
		827
		828	fcntl $txn->{fh}, F_SETFL, 0;
		829	syswrite $txn->{fh}, $txn->{request}
		830	or die "connection or write error";
		831	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
		832
		833	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
		834	result and signals any possible waiters that the request ahs finished:
		835
		836	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
		837
		838	if (end-of-file or data complete) {
		839	$txn->{result} = $txn->{buf};
		840	$txn->{finished}->broadcast;
		841	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
		842	}
		843
		844	The C<result> method, finally, just waits for the finished signal (if the
		845	request was already finished, it doesn't wait, of course, and returns the
		846	data:
		847
		848	$txn->{finished}->wait;
		849	return $txn->{result};
		850
		851	The actual code goes further and collects all errors (C<die>s, exceptions)
		852	that occured during request processing. The C<result> method detects
		853	whether an exception as thrown (it is stored inside the $txn object)
		854	and just throws the exception, which means connection errors and other
		855	problems get reported tot he code that tries to use the result, not in a
		856	random callback.
		857
		858	All of this enables the following usage styles:
		859
		860	1. Blocking:
		861
		862	my $data = $fcp->client_get ($url);
		863
		864	2. Blocking, but running in parallel:
		865
		866	my @datas = map $_->result,
		867	map $fcp->txn_client_get ($_),
		868	@urls;
		869
		870	Both blocking examples work without the module user having to know
		871	anything about events.
		872
		873	3a. Event-based in a main program, using any supported event module:
		874
		875	use EV;
		876
		877	$fcp->txn_client_get ($url)->cb (sub {
		878	my $txn = shift;
		879	my $data = $txn->result;
		880	...
		881	});
		882
		883	EV::loop;
		884
		885	3b. The module user could use AnyEvent, too:
		886
		887	use AnyEvent;
		888
		889	my $quit = AnyEvent->condvar;
		890
		891	$fcp->txn_client_get ($url)->cb (sub {
		892	...
		893	$quit->broadcast;
		894	});
		895
		896	$quit->wait;
		897
		898
		899	=head1 BENCHMARKS
		900
		901	To give you an idea of the performance and overheads that AnyEvent adds
		902	over the event loops themselves and to give you an impression of the speed
		903	of various event loops I prepared some benchmarks.
		904
		905	=head2 BENCHMARKING ANYEVENT OVERHEAD
		906
		907	Here is a benchmark of various supported event models used natively and
		908	through anyevent. The benchmark creates a lot of timers (with a zero
		909	timeout) and I/O watchers (watching STDOUT, a pty, to become writable,
		910	which it is), lets them fire exactly once and destroys them again.
		911
		912	Source code for this benchmark is found as F<eg/bench> in the AnyEvent
		913	distribution.
		914
		915	=head3 Explanation of the columns
		916
		917	I<watcher> is the number of event watchers created/destroyed. Since
		918	different event models feature vastly different performances, each event
		919	loop was given a number of watchers so that overall runtime is acceptable
		920	and similar between tested event loop (and keep them from crashing): Glib
		921	would probably take thousands of years if asked to process the same number
		922	of watchers as EV in this benchmark.
		923
		924	I<bytes> is the number of bytes (as measured by the resident set size,
		925	RSS) consumed by each watcher. This method of measuring captures both C
		926	and Perl-based overheads.
		927
		928	I<create> is the time, in microseconds (millionths of seconds), that it
		929	takes to create a single watcher. The callback is a closure shared between
		930	all watchers, to avoid adding memory overhead. That means closure creation
		931	and memory usage is not included in the figures.
		932
		933	I<invoke> is the time, in microseconds, used to invoke a simple
		934	callback. The callback simply counts down a Perl variable and after it was
		935	invoked "watcher" times, it would C<< ->broadcast >> a condvar once to
		936	signal the end of this phase.
		937
		938	I<destroy> is the time, in microseconds, that it takes to destroy a single
		939	watcher.
		940
		941	=head3 Results
		942
		943	name watchers bytes create invoke destroy comment
		944	EV/EV 400000 244 0.56 0.46 0.31 EV native interface
		945	EV/Any 100000 244 2.50 0.46 0.29 EV + AnyEvent watchers
		946	CoroEV/Any 100000 244 2.49 0.44 0.29 coroutines + Coro::Signal
		947	Perl/Any 100000 513 4.92 0.87 1.12 pure perl implementation
		948	Event/Event 16000 516 31.88 31.30 0.85 Event native interface
		949	Event/Any 16000 936 39.17 33.63 1.43 Event + AnyEvent watchers
		950	Glib/Any 16000 1357 98.22 12.41 54.00 quadratic behaviour
		951	Tk/Any 2000 1860 26.97 67.98 14.00 SEGV with >> 2000 watchers
		952	POE/Event 2000 6644 108.64 736.02 14.73 via POE::Loop::Event
		953	POE/Select 2000 6343 94.13 809.12 565.96 via POE::Loop::Select
		954
		955	=head3 Discussion
		956
		957	The benchmark does I<not> measure scalability of the event loop very
		958	well. For example, a select-based event loop (such as the pure perl one)
		959	can never compete with an event loop that uses epoll when the number of
		960	file descriptors grows high. In this benchmark, all events become ready at
		961	the same time, so select/poll-based implementations get an unnatural speed
		962	boost.
		963
		964	C<EV> is the sole leader regarding speed and memory use, which are both
		965	maximal/minimal, respectively. Even when going through AnyEvent, it uses
		966	far less memory than any other event loop and is still faster than Event
		967	natively.
		968
		969	The pure perl implementation is hit in a few sweet spots (both the
		970	constant timeout and the use of a single fd hit optimisations in the perl
		971	interpreter and the backend itself). Nevertheless this shows that it
		972	adds very little overhead in itself. Like any select-based backend its
		973	performance becomes really bad with lots of file descriptors (and few of
		974	them active), of course, but this was not subject of this benchmark.
		975
		976	The C<Event> module has a relatively high setup and callback invocation
		977	cost, but overall scores in on the third place.
		978
		979	C<Glib>'s memory usage is quite a bit higher, but it features a
		980	faster callback invocation and overall ends up in the same class as
		981	C<Event>. However, Glib scales extremely badly, doubling the number of
		982	watchers increases the processing time by more than a factor of four,
		983	making it completely unusable when using larger numbers of watchers
		984	(note that only a single file descriptor was used in the benchmark, so
		985	inefficiencies of C<poll> do not account for this).
		986
		987	The C<Tk> adaptor works relatively well. The fact that it crashes with
		988	more than 2000 watchers is a big setback, however, as correctness takes
		989	precedence over speed. Nevertheless, its performance is surprising, as the
		990	file descriptor is dup()ed for each watcher. This shows that the dup()
		991	employed by some adaptors is not a big performance issue (it does incur a
		992	hidden memory cost inside the kernel which is not reflected in the figures
		993	above).
		994
		995	C<POE>, regardless of underlying event loop (whether using its pure
		996	perl select-based backend or the Event module, the POE-EV backend
		997	couldn't be tested because it wasn't working) shows abysmal performance
		998	and memory usage: Watchers use almost 30 times as much memory as
		999	EV watchers, and 10 times as much memory as Event (the high memory
		1000	requirements are caused by requiring a session for each watcher). Watcher
		1001	invocation speed is almost 900 times slower than with AnyEvent's pure perl
		1002	implementation. The design of the POE adaptor class in AnyEvent can not
		1003	really account for this, as session creation overhead is small compared
		1004	to execution of the state machine, which is coded pretty optimally within
		1005	L<AnyEvent::Impl::POE>. POE simply seems to be abysmally slow.
		1006
		1007	=head3 Summary
		1008
		1009	=over 4
		1010
		1011	=item * Using EV through AnyEvent is faster than any other event loop
		1012	(even when used without AnyEvent), but most event loops have acceptable
		1013	performance with or without AnyEvent.
		1014
		1015	=item * The overhead AnyEvent adds is usually much smaller than the overhead of
		1016	the actual event loop, only with extremely fast event loops such as EV
		1017	adds AnyEvent significant overhead.
		1018
		1019	=item * You should avoid POE like the plague if you want performance or
		1020	reasonable memory usage.
		1021
		1022	=back
		1023
		1024	=head2 BENCHMARKING THE LARGE SERVER CASE
		1025
		1026	This benchmark atcually benchmarks the event loop itself. It works by
		1027	creating a number of "servers": each server consists of a socketpair, a
		1028	timeout watcher that gets reset on activity (but never fires), and an I/O
		1029	watcher waiting for input on one side of the socket. Each time the socket
		1030	watcher reads a byte it will write that byte to a random other "server".
		1031
		1032	The effect is that there will be a lot of I/O watchers, only part of which
		1033	are active at any one point (so there is a constant number of active
		1034	fds for each loop iterstaion, but which fds these are is random). The
		1035	timeout is reset each time something is read because that reflects how
		1036	most timeouts work (and puts extra pressure on the event loops).
		1037
		1038	In this benchmark, we use 10000 socketpairs (20000 sockets), of which 100
		1039	(1%) are active. This mirrors the activity of large servers with many
		1040	connections, most of which are idle at any one point in time.
		1041
		1042	Source code for this benchmark is found as F<eg/bench2> in the AnyEvent
		1043	distribution.
		1044
		1045	=head3 Explanation of the columns
		1046
		1047	I<sockets> is the number of sockets, and twice the number of "servers" (as
		1048	each server has a read and write socket end).
		1049
		1050	I<create> is the time it takes to create a socketpair (which is
		1051	nontrivial) and two watchers: an I/O watcher and a timeout watcher.
		1052
		1053	I<request>, the most important value, is the time it takes to handle a
		1054	single "request", that is, reading the token from the pipe and forwarding
		1055	it to another server. This includes deleting the old timeout and creating
		1056	a new one that moves the timeout into the future.
		1057
		1058	=head3 Results
		1059
		1060	name sockets create request
		1061	EV 20000 69.01 11.16
		1062	Perl 20000 75.28 112.76
		1063	Event 20000 212.62 257.32
		1064	Glib 20000 651.16 1896.30
		1065	POE 20000 349.67 12317.24 uses POE::Loop::Event
		1066
		1067	=head3 Discussion
		1068
		1069	This benchmark I<does> measure scalability and overall performance of the
		1070	particular event loop.
		1071
		1072	EV is again fastest. Since it is using epoll on my system, the setup time
		1073	is relatively high, though.
		1074
		1075	Perl surprisingly comes second. It is much faster than the C-based event
		1076	loops Event and Glib.
		1077
		1078	Event suffers from high setup time as well (look at its code and you will
		1079	understand why). Callback invocation also has a high overhead compared to
		1080	the C<< $_->() for .. >>-style loop that the Perl event loop uses. Event
		1081	uses select or poll in basically all documented configurations.
		1082
		1083	Glib is hit hard by its quadratic behaviour w.r.t. many watchers. It
		1084	clearly fails to perform with many filehandles or in busy servers.
		1085
		1086	POE is still completely out of the picture, taking over 1000 times as long
		1087	as EV, and over 100 times as long as the Perl implementation, even though
		1088	it uses a C-based event loop in this case.
		1089
		1090	=head3 Summary
		1091
		1092	=over 4
		1093
		1094	=item * The pure perl implementation performs extremely well, considering
		1095	that it uses select.
		1096
		1097	=item * Avoid Glib or POE in large projects where performance matters.
		1098
		1099	=back
		1100
		1101	=head2 BENCHMARKING SMALL SERVERS
		1102
		1103	While event loops should scale (and select-based ones do not...) even to
		1104	large servers, most programs we (or I :) actually write have only a few
		1105	I/O watchers.
		1106
		1107	In this benchmark, I use the same benchmark program as in the large server
		1108	case, but it uses only eight "servers", of which three are active at any
		1109	one time. This should reflect performance for a small server relatively
		1110	well.
		1111
		1112	The columns are identical to the previous table.
		1113
		1114	=head3 Results
		1115
		1116	name sockets create request
		1117	EV 16 20.00 6.54
		1118	Event 16 81.27 35.86
		1119	Glib 16 32.63 15.48
		1120	Perl 16 24.62 162.37
		1121	POE 16 261.87 276.28 uses POE::Loop::Event
		1122
		1123	=head3 Discussion
		1124
		1125	The benchmark tries to test the performance of a typical small
		1126	server. While knowing how various event loops perform is interesting, keep
		1127	in mind that their overhead in this case is usually not as important, due
		1128	to the small absolute number of watchers.
		1129
		1130	EV is again fastest.
		1131
		1132	The C-based event loops Event and Glib come in second this time, as the
		1133	overhead of running an iteration is much smaller in C than in Perl (little
		1134	code to execute in the inner loop, and perl's function calling overhead is
		1135	high, and updating all the data structures is costly).
		1136
		1137	The pure perl event loop is much slower, but still competitive.
		1138
		1139	POE also performs much better in this case, but is is stillf ar behind the
		1140	others.
		1141
		1142	=head3 Summary
		1143
		1144	=over 4
		1145
		1146	=item * C-based event loops perform very well with small number of
		1147	watchers, as the management overhead dominates.
		1148
		1149	=back
		1150
		1151
		1152	=head1 FORK
		1153
		1154	Most event libraries are not fork-safe. The ones who are usually are
		1155	because they are so inefficient. Only L<EV> is fully fork-aware.
		1156
		1157	If you have to fork, you must either do so I<before> creating your first
		1158	watcher OR you must not use AnyEvent at all in the child.
		1159
		1160
		1161	=head1 SECURITY CONSIDERATIONS
		1162
		1163	AnyEvent can be forced to load any event model via
		1164	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
		1165	execute arbitrary code or directly gain access, it can easily be used to
		1166	make the program hang or malfunction in subtle ways, as AnyEvent watchers
		1167	will not be active when the program uses a different event model than
		1168	specified in the variable.
		1169
		1170	You can make AnyEvent completely ignore this variable by deleting it
		1171	before the first watcher gets created, e.g. with a C<BEGIN> block:
		1172
		1173	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
		1174
		1175	use AnyEvent;
		1176
		1177
139	=head1 SEE ALSO	1178	=head1 SEE ALSO
140		1179
		1180	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,
141	L<Coro::Event>, L<Coro>, L<Event>, L<Glib::Event>, L<Glib>,	1181	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,
142	L<AnyEvent::Impl::Coro>,	1182	L<Event::Lib>, L<Qt>, L<POE>.
143	L<AnyEvent::Impl::Event>,
144	L<AnyEvent::Impl::Glib>,
145	L<AnyEvent::Impl::Tk>.
146		1183
147	=head1	1184	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,
		1185	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,
		1186	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,
		1187	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.
		1188
		1189	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.
		1190
		1191
		1192	=head1 AUTHOR
		1193
		1194	Marc Lehmann <schmorp@schmorp.de>
		1195	http://home.schmorp.de/
148		1196
149	=cut	1197	=cut
150		1198
151	1	1199	1
152		1200

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Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.2 by root, Thu Dec 1 18:56:18 2005 UTC vs.
Revision 1.94 by root, Sat Apr 26 04:33:51 2008 UTC