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

Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.4 by root, Thu Dec 1 22:04:50 2005 UTC vs.
Revision 1.56 by root, Thu Apr 24 03:10:03 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 - 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<Tk>. The first one found is used. If none are found,
44	order given. The first one that could be successfully loaded will be	86	the module tries to load these modules in the stated order. The first one
45	used. If still none could be found, it will issue an error.	87	that can be successfully loaded will be used. If, after this, still none
		88	could be found, AnyEvent will fall back to a pure-perl event loop, which
		89	is not very efficient, but should work everywhere.
		90
		91	Because AnyEvent first checks for modules that are already loaded, loading
		92	an event model explicitly before first using AnyEvent will likely make
		93	that model the default. For example:
		94
		95	use Tk;
		96	use AnyEvent;
		97
		98	# .. AnyEvent will likely default to Tk
		99
		100	The I<likely> means that, if any module loads another event model and
		101	starts using it, all bets are off. Maybe you should tell their authors to
		102	use AnyEvent so their modules work together with others seamlessly...
		103
		104	The pure-perl implementation of AnyEvent is called
		105	C<AnyEvent::Impl::Perl>. Like other event modules you can load it
		106	explicitly.
		107
		108	=head1 WATCHERS
		109
		110	AnyEvent has the central concept of a I<watcher>, which is an object that
		111	stores relevant data for each kind of event you are waiting for, such as
		112	the callback to call, the filehandle to watch, etc.
		113
		114	These watchers are normal Perl objects with normal Perl lifetime. After
		115	creating a watcher it will immediately "watch" for events and invoke the
		116	callback when the event occurs (of course, only when the event model
		117	is in control).
		118
		119	To disable the watcher you have to destroy it (e.g. by setting the
		120	variable you store it in to C<undef> or otherwise deleting all references
		121	to it).
		122
		123	All watchers are created by calling a method on the C<AnyEvent> class.
		124
		125	Many watchers either are used with "recursion" (repeating timers for
		126	example), or need to refer to their watcher object in other ways.
		127
		128	An any way to achieve that is this pattern:
		129
		130	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
		131	# you can use $w here, for example to undef it
		132	undef $w;
		133	});
		134
		135	Note that C<my $w; $w => combination. This is necessary because in Perl,
		136	my variables are only visible after the statement in which they are
		137	declared.
		138
		139	=head2 IO WATCHERS
		140
		141	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
		142	with the following mandatory key-value pairs as arguments:
		143
		144	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch for
		145	events. C<poll> must be a string that is either C<r> or C<w>, which
		146	creates a watcher waiting for "r"eadable or "w"ritable events,
		147	respectively. C<cb> is the callback to invoke each time the file handle
		148	becomes ready.
		149
		150	As long as the I/O watcher exists it will keep the file descriptor or a
		151	copy of it alive/open.
		152
		153	It is not allowed to close a file handle as long as any watcher is active
		154	on the underlying file descriptor.
		155
		156	Some event loops issue spurious readyness notifications, so you should
		157	always use non-blocking calls when reading/writing from/to your file
		158	handles.
		159
		160	Example:
		161
		162	# wait for readability of STDIN, then read a line and disable the watcher
		163	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		164	chomp (my $input = <STDIN>);
		165	warn "read: $input\n";
		166	undef $w;
		167	});
		168
		169	=head2 TIME WATCHERS
		170
		171	You can create a time watcher by calling the C<< AnyEvent->timer >>
		172	method with the following mandatory arguments:
		173
		174	C<after> specifies after how many seconds (fractional values are
		175	supported) should the timer activate. C<cb> the callback to invoke in that
		176	case.
		177
		178	The timer callback will be invoked at most once: if you want a repeating
		179	timer you have to create a new watcher (this is a limitation by both Tk
		180	and Glib).
		181
		182	Example:
		183
		184	# fire an event after 7.7 seconds
		185	my $w = AnyEvent->timer (after => 7.7, cb => sub {
		186	warn "timeout\n";
		187	});
		188
		189	# to cancel the timer:
		190	undef $w;
		191
		192	Example 2:
		193
		194	# fire an event after 0.5 seconds, then roughly every second
		195	my $w;
		196
		197	my $cb = sub {
		198	# cancel the old timer while creating a new one
		199	$w = AnyEvent->timer (after => 1, cb => $cb);
		200	};
		201
		202	# start the "loop" by creating the first watcher
		203	$w = AnyEvent->timer (after => 0.5, cb => $cb);
		204
		205	=head3 TIMING ISSUES
		206
		207	There are two ways to handle timers: based on real time (relative, "fire
		208	in 10 seconds") and based on wallclock time (absolute, "fire at 12
		209	o'clock").
		210
		211	While most event loops expect timers to specified in a relative way, they use
		212	absolute time internally. This makes a difference when your clock "jumps",
		213	for example, when ntp decides to set your clock backwards from the wrong 2014-01-01 to
		214	2008-01-01, a watcher that you created to fire "after" a second might actually take
		215	six years to finally fire.
		216
		217	AnyEvent cannot compensate for this. The only event loop that is conscious
		218	about these issues is L<EV>, which offers both relative (ev_timer) and
		219	absolute (ev_periodic) timers.
		220
		221	AnyEvent always prefers relative timers, if available, matching the
		222	AnyEvent API.
		223
		224	=head2 SIGNAL WATCHERS
		225
		226	You can watch for signals using a signal watcher, C<signal> is the signal
		227	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to
		228	be invoked whenever a signal occurs.
		229
		230	Multiple signals occurances can be clumped together into one callback
		231	invocation, and callback invocation will be synchronous. synchronous means
		232	that it might take a while until the signal gets handled by the process,
		233	but it is guarenteed not to interrupt any other callbacks.
		234
		235	The main advantage of using these watchers is that you can share a signal
		236	between multiple watchers.
		237
		238	This watcher might use C<%SIG>, so programs overwriting those signals
		239	directly will likely not work correctly.
		240
		241	Example: exit on SIGINT
		242
		243	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
		244
		245	=head2 CHILD PROCESS WATCHERS
		246
		247	You can also watch on a child process exit and catch its exit status.
		248
		249	The child process is specified by the C<pid> argument (if set to C<0>, it
		250	watches for any child process exit). The watcher will trigger as often
		251	as status change for the child are received. This works by installing a
		252	signal handler for C<SIGCHLD>. The callback will be called with the pid
		253	and exit status (as returned by waitpid).
		254
		255	Example: wait for pid 1333
		256
		257	my $w = AnyEvent->child (
		258	pid => 1333,
		259	cb => sub {
		260	my ($pid, $status) = @_;
		261	warn "pid $pid exited with status $status";
		262	},
		263	);
		264
		265	=head2 CONDITION VARIABLES
		266
		267	Condition variables can be created by calling the C<< AnyEvent->condvar >>
		268	method without any arguments.
		269
		270	A condition variable waits for a condition - precisely that the C<<
		271	->broadcast >> method has been called.
		272
		273	They are very useful to signal that a condition has been fulfilled, for
		274	example, if you write a module that does asynchronous http requests,
		275	then a condition variable would be the ideal candidate to signal the
		276	availability of results.
		277
		278	You can also use condition variables to block your main program until
		279	an event occurs - for example, you could C<< ->wait >> in your main
		280	program until the user clicks the Quit button in your app, which would C<<
		281	->broadcast >> the "quit" event.
		282
		283	Note that condition variables recurse into the event loop - if you have
		284	two pirces of code that call C<< ->wait >> in a round-robbin fashion, you
		285	lose. Therefore, condition variables are good to export to your caller, but
		286	you should avoid making a blocking wait yourself, at least in callbacks,
		287	as this asks for trouble.
		288
		289	This object has two methods:
46		290
47	=over 4	291	=over 4
48		292
		293	=item $cv->wait
		294
		295	Wait (blocking if necessary) until the C<< ->broadcast >> method has been
		296	called on c<$cv>, while servicing other watchers normally.
		297
		298	You can only wait once on a condition - additional calls will return
		299	immediately.
		300
		301	Not all event models support a blocking wait - some die in that case
		302	(programs might want to do that to stay interactive), so I<if you are
		303	using this from a module, never require a blocking wait>, but let the
		304	caller decide whether the call will block or not (for example, by coupling
		305	condition variables with some kind of request results and supporting
		306	callbacks so the caller knows that getting the result will not block,
		307	while still suppporting blocking waits if the caller so desires).
		308
		309	Another reason I<never> to C<< ->wait >> in a module is that you cannot
		310	sensibly have two C<< ->wait >>'s in parallel, as that would require
		311	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
		312	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and
		313	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
		314	from different coroutines, however).
		315
		316	=item $cv->broadcast
		317
		318	Flag the condition as ready - a running C<< ->wait >> and all further
		319	calls to C<wait> will (eventually) return after this method has been
		320	called. If nobody is waiting the broadcast will be remembered..
		321
		322	=back
		323
		324	Example:
		325
		326	# wait till the result is ready
		327	my $result_ready = AnyEvent->condvar;
		328
		329	# do something such as adding a timer
		330	# or socket watcher the calls $result_ready->broadcast
		331	# when the "result" is ready.
		332	# in this case, we simply use a timer:
		333	my $w = AnyEvent->timer (
		334	after => 1,
		335	cb => sub { $result_ready->broadcast },
		336	);
		337
		338	# this "blocks" (while handling events) till the watcher
		339	# calls broadcast
		340	$result_ready->wait;
		341
		342	=head1 GLOBAL VARIABLES AND FUNCTIONS
		343
		344	=over 4
		345
		346	=item $AnyEvent::MODEL
		347
		348	Contains C<undef> until the first watcher is being created. Then it
		349	contains the event model that is being used, which is the name of the
		350	Perl class implementing the model. This class is usually one of the
		351	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case
		352	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).
		353
		354	The known classes so far are:
		355
		356	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
		357	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
		358	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
		359	AnyEvent::Impl::Event based on Event, second best choice.
		360	AnyEvent::Impl::Glib based on Glib, third-best choice.
		361	AnyEvent::Impl::Tk based on Tk, very bad choice.
		362	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
		363	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
		364	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		365
		366	=item AnyEvent::detect
		367
		368	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
		369	if necessary. You should only call this function right before you would
		370	have created an AnyEvent watcher anyway, that is, as late as possible at
		371	runtime.
		372
		373	=back
		374
		375	=head1 WHAT TO DO IN A MODULE
		376
		377	As a module author, you should C<use AnyEvent> and call AnyEvent methods
		378	freely, but you should not load a specific event module or rely on it.
		379
		380	Be careful when you create watchers in the module body - AnyEvent will
		381	decide which event module to use as soon as the first method is called, so
		382	by calling AnyEvent in your module body you force the user of your module
		383	to load the event module first.
		384
		385	Never call C<< ->wait >> on a condition variable unless you I<know> that
		386	the C<< ->broadcast >> method has been called on it already. This is
		387	because it will stall the whole program, and the whole point of using
		388	events is to stay interactive.
		389
		390	It is fine, however, to call C<< ->wait >> when the user of your module
		391	requests it (i.e. if you create a http request object ad have a method
		392	called C<results> that returns the results, it should call C<< ->wait >>
		393	freely, as the user of your module knows what she is doing. always).
		394
		395	=head1 WHAT TO DO IN THE MAIN PROGRAM
		396
		397	There will always be a single main program - the only place that should
		398	dictate which event model to use.
		399
		400	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
		401	do anything special (it does not need to be event-based) and let AnyEvent
		402	decide which implementation to chose if some module relies on it.
		403
		404	If the main program relies on a specific event model. For example, in
		405	Gtk2 programs you have to rely on the Glib module. You should load the
		406	event module before loading AnyEvent or any module that uses it: generally
		407	speaking, you should load it as early as possible. The reason is that
		408	modules might create watchers when they are loaded, and AnyEvent will
		409	decide on the event model to use as soon as it creates watchers, and it
		410	might chose the wrong one unless you load the correct one yourself.
		411
		412	You can chose to use a rather inefficient pure-perl implementation by
		413	loading the C<AnyEvent::Impl::Perl> module, which gives you similar
		414	behaviour everywhere, but letting AnyEvent chose is generally better.
		415
49	=cut	416	=cut
50		417
51	package AnyEvent;	418	package AnyEvent;
52		419
53	no warnings;	420	no warnings;
54	use strict 'vars';	421	use strict;
		422
55	use Carp;	423	use Carp;
56		424
57	our $VERSION = 0.2;	425	our $VERSION = '3.12';
58	our $MODEL;	426	our $MODEL;
59		427
60	our $AUTOLOAD;	428	our $AUTOLOAD;
61	our @ISA;	429	our @ISA;
62		430
		431	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
		432
		433	our @REGISTRY;
		434
63	my @models = (	435	my @models = (
64	[Coro => Coro::Event::],	436	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
65	[Event => Event::],	437	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
66	[Glib => Glib::],	438	[EV:: => AnyEvent::Impl::EV::],
67	[Tk => Tk::],	439	[Event:: => AnyEvent::Impl::Event::],
		440	[Glib:: => AnyEvent::Impl::Glib::],
		441	[Tk:: => AnyEvent::Impl::Tk::],
		442	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
68	);	443	);
		444	my @models_detect = (
		445	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		446	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		447	);
69		448
70	our %method = map +($_ => 1), qw(io timer condvar broadcast wait cancel DESTROY);	449	our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);
71		450
72	sub AUTOLOAD {	451	sub detect() {
73	$AUTOLOAD =~ s/.*://;
74
75	$method{$AUTOLOAD}
76	or croak "$AUTOLOAD: not a valid method for AnyEvent objects";
77
78	unless ($MODEL) {	452	unless ($MODEL) {
79	# check for already loaded models	453	no strict 'refs';
80	for (@models) {	454
81	my ($model, $package) = @$_;	455	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
82	if (scalar keys %{ *{"$package\::"} }) {	456	my $model = "AnyEvent::Impl::$1";
83	eval "require AnyEvent::Impl::$model";	457	if (eval "require $model") {
84	last if $MODEL;	458	$MODEL = $model;
		459	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;
85	}	460	}
86	}	461	}
87		462
		463	# check for already loaded models
88	unless ($MODEL) {	464	unless ($MODEL) {
89	# try to load a model	465	for (@REGISTRY, @models, @models_detect) {
90
91	for (@models) {
92	my ($model, $package) = @$_;	466	my ($package, $model) = @$_;
93	eval "require AnyEvent::Impl::$model";	467	if (${"$package\::VERSION"} > 0) {
94	last if $MODEL;	468	if (eval "require $model") {
		469	$MODEL = $model;
		470	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;
		471	last;
		472	}
		473	}
95	}	474	}
96		475
		476	unless ($MODEL) {
		477	# try to load a model
		478
		479	for (@REGISTRY, @models) {
		480	my ($package, $model) = @$_;
		481	if (eval "require $package"
		482	and ${"$package\::VERSION"} > 0
		483	and eval "require $model") {
		484	$MODEL = $model;
		485	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;
		486	last;
		487	}
		488	}
		489
97	$MODEL	490	$MODEL
98	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: Coro, Event, Glib or Tk.";	491	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.";
		492	}
99	}	493	}
		494
		495	unshift @ISA, $MODEL;
		496	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
100	}	497	}
101		498
102	@ISA = $MODEL;	499	$MODEL
		500	}
		501
		502	sub AUTOLOAD {
		503	(my $func = $AUTOLOAD) =~ s/.*://;
		504
		505	$method{$func}
		506	or croak "$func: not a valid method for AnyEvent objects";
		507
		508	detect unless $MODEL;
103		509
104	my $class = shift;	510	my $class = shift;
105	$class->$AUTOLOAD (@_);	511	$class->$func (@_);
106	}	512	}
		513
		514	package AnyEvent::Base;
		515
		516	# default implementation for ->condvar, ->wait, ->broadcast
		517
		518	sub condvar {
		519	bless \my $flag, "AnyEvent::Base::CondVar"
		520	}
		521
		522	sub AnyEvent::Base::CondVar::broadcast {
		523	${$_[0]}++;
		524	}
		525
		526	sub AnyEvent::Base::CondVar::wait {
		527	AnyEvent->one_event while !${$_[0]};
		528	}
		529
		530	# default implementation for ->signal
		531
		532	our %SIG_CB;
		533
		534	sub signal {
		535	my (undef, %arg) = @_;
		536
		537	my $signal = uc $arg{signal}
		538	or Carp::croak "required option 'signal' is missing";
		539
		540	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		541	$SIG{$signal} \|\|= sub {
		542	$_->() for values %{ $SIG_CB{$signal} \|\| {} };
		543	};
		544
		545	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"
		546	}
		547
		548	sub AnyEvent::Base::Signal::DESTROY {
		549	my ($signal, $cb) = @{$_[0]};
		550
		551	delete $SIG_CB{$signal}{$cb};
		552
		553	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };
		554	}
		555
		556	# default implementation for ->child
		557
		558	our %PID_CB;
		559	our $CHLD_W;
		560	our $CHLD_DELAY_W;
		561	our $PID_IDLE;
		562	our $WNOHANG;
		563
		564	sub _child_wait {
		565	while (0 < (my $pid = waitpid -1, $WNOHANG)) {
		566	$_->($pid, $?) for (values %{ $PID_CB{$pid} \|\| {} }),
		567	(values %{ $PID_CB{0} \|\| {} });
		568	}
		569
		570	undef $PID_IDLE;
		571	}
		572
		573	sub _sigchld {
		574	# make sure we deliver these changes "synchronous" with the event loop.
		575	$CHLD_DELAY_W \|\|= AnyEvent->timer (after => 0, cb => sub {
		576	undef $CHLD_DELAY_W;
		577	&_child_wait;
		578	});
		579	}
		580
		581	sub child {
		582	my (undef, %arg) = @_;
		583
		584	defined (my $pid = $arg{pid} + 0)
		585	or Carp::croak "required option 'pid' is missing";
		586
		587	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
		588
		589	unless ($WNOHANG) {
		590	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } \|\| 1;
		591	}
		592
		593	unless ($CHLD_W) {
		594	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
		595	# child could be a zombie already, so make at least one round
		596	&_sigchld;
		597	}
		598
		599	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"
		600	}
		601
		602	sub AnyEvent::Base::Child::DESTROY {
		603	my ($pid, $cb) = @{$_[0]};
		604
		605	delete $PID_CB{$pid}{$cb};
		606	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
		607
		608	undef $CHLD_W unless keys %PID_CB;
		609	}
		610
		611	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
		612
		613	This is an advanced topic that you do not normally need to use AnyEvent in
		614	a module. This section is only of use to event loop authors who want to
		615	provide AnyEvent compatibility.
		616
		617	If you need to support another event library which isn't directly
		618	supported by AnyEvent, you can supply your own interface to it by
		619	pushing, before the first watcher gets created, the package name of
		620	the event module and the package name of the interface to use onto
		621	C<@AnyEvent::REGISTRY>. You can do that before and even without loading
		622	AnyEvent, so it is reasonably cheap.
		623
		624	Example:
		625
		626	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
		627
		628	This tells AnyEvent to (literally) use the C<urxvt::anyevent::>
		629	package/class when it finds the C<urxvt> package/module is already loaded.
		630
		631	When AnyEvent is loaded and asked to find a suitable event model, it
		632	will first check for the presence of urxvt by trying to C<use> the
		633	C<urxvt::anyevent> module.
		634
		635	The class should provide implementations for all watcher types. See
		636	L<AnyEvent::Impl::EV> (source code), L<AnyEvent::Impl::Glib> (Source code)
		637	and so on for actual examples. Use C<perldoc -m AnyEvent::Impl::Glib> to
		638	see the sources.
		639
		640	If you don't provide C<signal> and C<child> watchers than AnyEvent will
		641	provide suitable (hopefully) replacements.
		642
		643	The above example isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt)
		644	terminal emulator uses the above line as-is. An interface isn't included
		645	in AnyEvent because it doesn't make sense outside the embedded interpreter
		646	inside I<rxvt-unicode>, and it is updated and maintained as part of the
		647	I<rxvt-unicode> distribution.
		648
		649	I<rxvt-unicode> also cheats a bit by not providing blocking access to
		650	condition variables: code blocking while waiting for a condition will
		651	C<die>. This still works with most modules/usages, and blocking calls must
		652	not be done in an interactive application, so it makes sense.
		653
		654	=head1 ENVIRONMENT VARIABLES
		655
		656	The following environment variables are used by this module:
		657
		658	=over 4
		659
		660	=item C<PERL_ANYEVENT_VERBOSE>
		661
		662	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		663	model it chooses.
		664
		665	=item C<PERL_ANYEVENT_MODEL>
		666
		667	This can be used to specify the event model to be used by AnyEvent, before
		668	autodetection and -probing kicks in. It must be a string consisting
		669	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		670	and the resulting module name is loaded and if the load was successful,
		671	used as event model. If it fails to load AnyEvent will proceed with
		672	autodetection and -probing.
		673
		674	This functionality might change in future versions.
		675
		676	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		677	could start your program like this:
		678
		679	PERL_ANYEVENT_MODEL=Perl perl ...
107		680
108	=back	681	=back
109		682
110	=head1 EXAMPLE	683	=head1 EXAMPLE PROGRAM
111		684
112	The following program uses an io watcher to read data from stdin, a timer	685	The following program uses an IO watcher to read data from STDIN, a timer
113	to display a message once per second, and a condvar to exit the program	686	to display a message once per second, and a condition variable to quit the
114	when the user enters quit:	687	program when the user enters quit:
115		688
116	use AnyEvent;	689	use AnyEvent;
117		690
118	my $cv = AnyEvent->condvar;	691	my $cv = AnyEvent->condvar;
119		692
120	my $io_watcher = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	693	my $io_watcher = AnyEvent->io (
		694	fh => \*STDIN,
		695	poll => 'r',
		696	cb => sub {
121	warn "io event <$_[0]>\n"; # will always output <r>	697	warn "io event <$_[0]>\n"; # will always output <r>
122	chomp (my $input = <STDIN>); # read a line	698	chomp (my $input = <STDIN>); # read a line
123	warn "read: $input\n"; # output what has been read	699	warn "read: $input\n"; # output what has been read
124	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	700	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i
		701	},
125	});	702	);
126		703
127	my $time_watcher; # can only be used once	704	my $time_watcher; # can only be used once
128		705
129	sub new_timer {	706	sub new_timer {
130	$timer = AnyEvent->timer (after => 1, cb => sub {	707	$timer = AnyEvent->timer (after => 1, cb => sub {
135		712
136	new_timer; # create first timer	713	new_timer; # create first timer
137		714
138	$cv->wait; # wait until user enters /^q/i	715	$cv->wait; # wait until user enters /^q/i
139		716
		717	=head1 REAL-WORLD EXAMPLE
		718
		719	Consider the L<Net::FCP> module. It features (among others) the following
		720	API calls, which are to freenet what HTTP GET requests are to http:
		721
		722	my $data = $fcp->client_get ($url); # blocks
		723
		724	my $transaction = $fcp->txn_client_get ($url); # does not block
		725	$transaction->cb ( sub { ... } ); # set optional result callback
		726	my $data = $transaction->result; # possibly blocks
		727
		728	The C<client_get> method works like C<LWP::Simple::get>: it requests the
		729	given URL and waits till the data has arrived. It is defined to be:
		730
		731	sub client_get { $_[0]->txn_client_get ($_[1])->result }
		732
		733	And in fact is automatically generated. This is the blocking API of
		734	L<Net::FCP>, and it works as simple as in any other, similar, module.
		735
		736	More complicated is C<txn_client_get>: It only creates a transaction
		737	(completion, result, ...) object and initiates the transaction.
		738
		739	my $txn = bless { }, Net::FCP::Txn::;
		740
		741	It also creates a condition variable that is used to signal the completion
		742	of the request:
		743
		744	$txn->{finished} = AnyAvent->condvar;
		745
		746	It then creates a socket in non-blocking mode.
		747
		748	socket $txn->{fh}, ...;
		749	fcntl $txn->{fh}, F_SETFL, O_NONBLOCK;
		750	connect $txn->{fh}, ...
		751	and !$!{EWOULDBLOCK}
		752	and !$!{EINPROGRESS}
		753	and Carp::croak "unable to connect: $!\n";
		754
		755	Then it creates a write-watcher which gets called whenever an error occurs
		756	or the connection succeeds:
		757
		758	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'w', cb => sub { $txn->fh_ready_w });
		759
		760	And returns this transaction object. The C<fh_ready_w> callback gets
		761	called as soon as the event loop detects that the socket is ready for
		762	writing.
		763
		764	The C<fh_ready_w> method makes the socket blocking again, writes the
		765	request data and replaces the watcher by a read watcher (waiting for reply
		766	data). The actual code is more complicated, but that doesn't matter for
		767	this example:
		768
		769	fcntl $txn->{fh}, F_SETFL, 0;
		770	syswrite $txn->{fh}, $txn->{request}
		771	or die "connection or write error";
		772	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
		773
		774	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
		775	result and signals any possible waiters that the request ahs finished:
		776
		777	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
		778
		779	if (end-of-file or data complete) {
		780	$txn->{result} = $txn->{buf};
		781	$txn->{finished}->broadcast;
		782	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
		783	}
		784
		785	The C<result> method, finally, just waits for the finished signal (if the
		786	request was already finished, it doesn't wait, of course, and returns the
		787	data:
		788
		789	$txn->{finished}->wait;
		790	return $txn->{result};
		791
		792	The actual code goes further and collects all errors (C<die>s, exceptions)
		793	that occured during request processing. The C<result> method detects
		794	whether an exception as thrown (it is stored inside the $txn object)
		795	and just throws the exception, which means connection errors and other
		796	problems get reported tot he code that tries to use the result, not in a
		797	random callback.
		798
		799	All of this enables the following usage styles:
		800
		801	1. Blocking:
		802
		803	my $data = $fcp->client_get ($url);
		804
		805	2. Blocking, but running in parallel:
		806
		807	my @datas = map $_->result,
		808	map $fcp->txn_client_get ($_),
		809	@urls;
		810
		811	Both blocking examples work without the module user having to know
		812	anything about events.
		813
		814	3a. Event-based in a main program, using any supported event module:
		815
		816	use EV;
		817
		818	$fcp->txn_client_get ($url)->cb (sub {
		819	my $txn = shift;
		820	my $data = $txn->result;
		821	...
		822	});
		823
		824	EV::loop;
		825
		826	3b. The module user could use AnyEvent, too:
		827
		828	use AnyEvent;
		829
		830	my $quit = AnyEvent->condvar;
		831
		832	$fcp->txn_client_get ($url)->cb (sub {
		833	...
		834	$quit->broadcast;
		835	});
		836
		837	$quit->wait;
		838
		839	=head1 FORK
		840
		841	Most event libraries are not fork-safe. The ones who are usually are
		842	because they are so inefficient. Only L<EV> is fully fork-aware.
		843
		844	If you have to fork, you must either do so I<before> creating your first
		845	watcher OR you must not use AnyEvent at all in the child.
		846
		847	=head1 SECURITY CONSIDERATIONS
		848
		849	AnyEvent can be forced to load any event model via
		850	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
		851	execute arbitrary code or directly gain access, it can easily be used to
		852	make the program hang or malfunction in subtle ways, as AnyEvent watchers
		853	will not be active when the program uses a different event model than
		854	specified in the variable.
		855
		856	You can make AnyEvent completely ignore this variable by deleting it
		857	before the first watcher gets created, e.g. with a C<BEGIN> block:
		858
		859	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
		860
		861	use AnyEvent;
		862
140	=head1 SEE ALSO	863	=head1 SEE ALSO
141		864
		865	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,
142	L<Coro::Event>, L<Coro>, L<Event>, L<Glib::Event>, L<Glib>,	866	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,
143	L<AnyEvent::Impl::Coro>,	867	L<Event::Lib>, L<Qt>.
144	L<AnyEvent::Impl::Event>,	868
145	L<AnyEvent::Impl::Glib>,	869	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,
		870	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,
		871	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,
146	L<AnyEvent::Impl::Tk>.	872	L<AnyEvent::Impl::Qt>.
147		873
148	=head1	874	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.
		875
		876	=head1 AUTHOR
		877
		878	Marc Lehmann <schmorp@schmorp.de>
		879	http://home.schmorp.de/
149		880
150	=cut	881	=cut
151		882
152	1	883	1
153		884

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Comparing AnyEvent/lib/AnyEvent.pm (file contents): Revision 1.4 by root, Thu Dec 1 22:04:50 2005 UTC vs. Revision 1.56 by root, Thu Apr 24 03:10:03 2008 UTC

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Comparing AnyEvent/lib/AnyEvent.pm (file contents):
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Revision 1.56 by root, Thu Apr 24 03:10:03 2008 UTC