[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 1.57 by root, Thu Apr 24 03:19:28 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
42	loaded: L<Coro::Event>, L<Event>, L<Glib>, L<Tk>. The first one found is	84	the following modules is already loaded: L<Coro::EV>, L<Coro::Event>,
		85	L<EV>, L<Event>, L<Glib>, L<Tk>, L<Event::Lib>, L<Qt>. The first one
43	used. If none is found, the module tries to load these modules in the	86	found is used. If none are found, the module tries to load these modules
44	order given. The first one that could be successfully loaded will be	87	(excluding Event::Lib and Qt) in the order given. The first one that can
45	used. If still none could be found, it will issue an error.	88	be successfully loaded will be used. If, after this, still none could be
		89	found, AnyEvent will fall back to a pure-perl event loop, which is not
		90	very efficient, but should work everywhere.
		91
		92	Because AnyEvent first checks for modules that are already loaded, loading
		93	an event model explicitly before first using AnyEvent will likely make
		94	that model the default. For example:
		95
		96	use Tk;
		97	use AnyEvent;
		98
		99	# .. AnyEvent will likely default to Tk
		100
		101	The I<likely> means that, if any module loads another event model and
		102	starts using it, all bets are off. Maybe you should tell their authors to
		103	use AnyEvent so their modules work together with others seamlessly...
		104
		105	The pure-perl implementation of AnyEvent is called
		106	C<AnyEvent::Impl::Perl>. Like other event modules you can load it
		107	explicitly.
		108
		109	=head1 WATCHERS
		110
		111	AnyEvent has the central concept of a I<watcher>, which is an object that
		112	stores relevant data for each kind of event you are waiting for, such as
		113	the callback to call, the filehandle to watch, etc.
		114
		115	These watchers are normal Perl objects with normal Perl lifetime. After
		116	creating a watcher it will immediately "watch" for events and invoke the
		117	callback when the event occurs (of course, only when the event model
		118	is in control).
		119
		120	To disable the watcher you have to destroy it (e.g. by setting the
		121	variable you store it in to C<undef> or otherwise deleting all references
		122	to it).
		123
		124	All watchers are created by calling a method on the C<AnyEvent> class.
		125
		126	Many watchers either are used with "recursion" (repeating timers for
		127	example), or need to refer to their watcher object in other ways.
		128
		129	An any way to achieve that is this pattern:
		130
		131	my $w; $w = AnyEvent->type (arg => value ..., cb => sub {
		132	# you can use $w here, for example to undef it
		133	undef $w;
		134	});
		135
		136	Note that C<my $w; $w => combination. This is necessary because in Perl,
		137	my variables are only visible after the statement in which they are
		138	declared.
		139
		140	=head2 IO WATCHERS
		141
		142	You can create an I/O watcher by calling the C<< AnyEvent->io >> method
		143	with the following mandatory key-value pairs as arguments:
		144
		145	C<fh> the Perl I<file handle> (I<not> file descriptor) to watch for
		146	events. C<poll> must be a string that is either C<r> or C<w>, which
		147	creates a watcher waiting for "r"eadable or "w"ritable events,
		148	respectively. C<cb> is the callback to invoke each time the file handle
		149	becomes ready.
		150
		151	As long as the I/O watcher exists it will keep the file descriptor or a
		152	copy of it alive/open.
		153
		154	It is not allowed to close a file handle as long as any watcher is active
		155	on the underlying file descriptor.
		156
		157	Some event loops issue spurious readyness notifications, so you should
		158	always use non-blocking calls when reading/writing from/to your file
		159	handles.
		160
		161	Example:
		162
		163	# wait for readability of STDIN, then read a line and disable the watcher
		164	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		165	chomp (my $input = <STDIN>);
		166	warn "read: $input\n";
		167	undef $w;
		168	});
		169
		170	=head2 TIME WATCHERS
		171
		172	You can create a time watcher by calling the C<< AnyEvent->timer >>
		173	method with the following mandatory arguments:
		174
		175	C<after> specifies after how many seconds (fractional values are
		176	supported) should the timer activate. C<cb> the callback to invoke in that
		177	case.
		178
		179	The timer callback will be invoked at most once: if you want a repeating
		180	timer you have to create a new watcher (this is a limitation by both Tk
		181	and Glib).
		182
		183	Example:
		184
		185	# fire an event after 7.7 seconds
		186	my $w = AnyEvent->timer (after => 7.7, cb => sub {
		187	warn "timeout\n";
		188	});
		189
		190	# to cancel the timer:
		191	undef $w;
		192
		193	Example 2:
		194
		195	# fire an event after 0.5 seconds, then roughly every second
		196	my $w;
		197
		198	my $cb = sub {
		199	# cancel the old timer while creating a new one
		200	$w = AnyEvent->timer (after => 1, cb => $cb);
		201	};
		202
		203	# start the "loop" by creating the first watcher
		204	$w = AnyEvent->timer (after => 0.5, cb => $cb);
		205
		206	=head3 TIMING ISSUES
		207
		208	There are two ways to handle timers: based on real time (relative, "fire
		209	in 10 seconds") and based on wallclock time (absolute, "fire at 12
		210	o'clock").
		211
		212	While most event loops expect timers to specified in a relative way, they use
		213	absolute time internally. This makes a difference when your clock "jumps",
		214	for example, when ntp decides to set your clock backwards from the wrong 2014-01-01 to
		215	2008-01-01, a watcher that you created to fire "after" a second might actually take
		216	six years to finally fire.
		217
		218	AnyEvent cannot compensate for this. The only event loop that is conscious
		219	about these issues is L<EV>, which offers both relative (ev_timer) and
		220	absolute (ev_periodic) timers.
		221
		222	AnyEvent always prefers relative timers, if available, matching the
		223	AnyEvent API.
		224
		225	=head2 SIGNAL WATCHERS
		226
		227	You can watch for signals using a signal watcher, C<signal> is the signal
		228	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to
		229	be invoked whenever a signal occurs.
		230
		231	Multiple signals occurances can be clumped together into one callback
		232	invocation, and callback invocation will be synchronous. synchronous means
		233	that it might take a while until the signal gets handled by the process,
		234	but it is guarenteed not to interrupt any other callbacks.
		235
		236	The main advantage of using these watchers is that you can share a signal
		237	between multiple watchers.
		238
		239	This watcher might use C<%SIG>, so programs overwriting those signals
		240	directly will likely not work correctly.
		241
		242	Example: exit on SIGINT
		243
		244	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
		245
		246	=head2 CHILD PROCESS WATCHERS
		247
		248	You can also watch on a child process exit and catch its exit status.
		249
		250	The child process is specified by the C<pid> argument (if set to C<0>, it
		251	watches for any child process exit). The watcher will trigger as often
		252	as status change for the child are received. This works by installing a
		253	signal handler for C<SIGCHLD>. The callback will be called with the pid
		254	and exit status (as returned by waitpid).
		255
		256	Example: wait for pid 1333
		257
		258	my $w = AnyEvent->child (
		259	pid => 1333,
		260	cb => sub {
		261	my ($pid, $status) = @_;
		262	warn "pid $pid exited with status $status";
		263	},
		264	);
		265
		266	=head2 CONDITION VARIABLES
		267
		268	Condition variables can be created by calling the C<< AnyEvent->condvar >>
		269	method without any arguments.
		270
		271	A condition variable waits for a condition - precisely that the C<<
		272	->broadcast >> method has been called.
		273
		274	They are very useful to signal that a condition has been fulfilled, for
		275	example, if you write a module that does asynchronous http requests,
		276	then a condition variable would be the ideal candidate to signal the
		277	availability of results.
		278
		279	You can also use condition variables to block your main program until
		280	an event occurs - for example, you could C<< ->wait >> in your main
		281	program until the user clicks the Quit button in your app, which would C<<
		282	->broadcast >> the "quit" event.
		283
		284	Note that condition variables recurse into the event loop - if you have
		285	two pirces of code that call C<< ->wait >> in a round-robbin fashion, you
		286	lose. Therefore, condition variables are good to export to your caller, but
		287	you should avoid making a blocking wait yourself, at least in callbacks,
		288	as this asks for trouble.
		289
		290	This object has two methods:
46		291
47	=over 4	292	=over 4
48		293
		294	=item $cv->wait
		295
		296	Wait (blocking if necessary) until the C<< ->broadcast >> method has been
		297	called on c<$cv>, while servicing other watchers normally.
		298
		299	You can only wait once on a condition - additional calls will return
		300	immediately.
		301
		302	Not all event models support a blocking wait - some die in that case
		303	(programs might want to do that to stay interactive), so I<if you are
		304	using this from a module, never require a blocking wait>, but let the
		305	caller decide whether the call will block or not (for example, by coupling
		306	condition variables with some kind of request results and supporting
		307	callbacks so the caller knows that getting the result will not block,
		308	while still suppporting blocking waits if the caller so desires).
		309
		310	Another reason I<never> to C<< ->wait >> in a module is that you cannot
		311	sensibly have two C<< ->wait >>'s in parallel, as that would require
		312	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
		313	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and
		314	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
		315	from different coroutines, however).
		316
		317	=item $cv->broadcast
		318
		319	Flag the condition as ready - a running C<< ->wait >> and all further
		320	calls to C<wait> will (eventually) return after this method has been
		321	called. If nobody is waiting the broadcast will be remembered..
		322
		323	=back
		324
		325	Example:
		326
		327	# wait till the result is ready
		328	my $result_ready = AnyEvent->condvar;
		329
		330	# do something such as adding a timer
		331	# or socket watcher the calls $result_ready->broadcast
		332	# when the "result" is ready.
		333	# in this case, we simply use a timer:
		334	my $w = AnyEvent->timer (
		335	after => 1,
		336	cb => sub { $result_ready->broadcast },
		337	);
		338
		339	# this "blocks" (while handling events) till the watcher
		340	# calls broadcast
		341	$result_ready->wait;
		342
		343	=head1 GLOBAL VARIABLES AND FUNCTIONS
		344
		345	=over 4
		346
		347	=item $AnyEvent::MODEL
		348
		349	Contains C<undef> until the first watcher is being created. Then it
		350	contains the event model that is being used, which is the name of the
		351	Perl class implementing the model. This class is usually one of the
		352	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case
		353	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).
		354
		355	The known classes so far are:
		356
		357	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
		358	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
		359	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
		360	AnyEvent::Impl::Event based on Event, second best choice.
		361	AnyEvent::Impl::Glib based on Glib, third-best choice.
		362	AnyEvent::Impl::Tk based on Tk, very bad choice.
		363	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
		364	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
		365	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		366
		367	=item AnyEvent::detect
		368
		369	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
		370	if necessary. You should only call this function right before you would
		371	have created an AnyEvent watcher anyway, that is, as late as possible at
		372	runtime.
		373
		374	=back
		375
		376	=head1 WHAT TO DO IN A MODULE
		377
		378	As a module author, you should C<use AnyEvent> and call AnyEvent methods
		379	freely, but you should not load a specific event module or rely on it.
		380
		381	Be careful when you create watchers in the module body - AnyEvent will
		382	decide which event module to use as soon as the first method is called, so
		383	by calling AnyEvent in your module body you force the user of your module
		384	to load the event module first.
		385
		386	Never call C<< ->wait >> on a condition variable unless you I<know> that
		387	the C<< ->broadcast >> method has been called on it already. This is
		388	because it will stall the whole program, and the whole point of using
		389	events is to stay interactive.
		390
		391	It is fine, however, to call C<< ->wait >> when the user of your module
		392	requests it (i.e. if you create a http request object ad have a method
		393	called C<results> that returns the results, it should call C<< ->wait >>
		394	freely, as the user of your module knows what she is doing. always).
		395
		396	=head1 WHAT TO DO IN THE MAIN PROGRAM
		397
		398	There will always be a single main program - the only place that should
		399	dictate which event model to use.
		400
		401	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
		402	do anything special (it does not need to be event-based) and let AnyEvent
		403	decide which implementation to chose if some module relies on it.
		404
		405	If the main program relies on a specific event model. For example, in
		406	Gtk2 programs you have to rely on the Glib module. You should load the
		407	event module before loading AnyEvent or any module that uses it: generally
		408	speaking, you should load it as early as possible. The reason is that
		409	modules might create watchers when they are loaded, and AnyEvent will
		410	decide on the event model to use as soon as it creates watchers, and it
		411	might chose the wrong one unless you load the correct one yourself.
		412
		413	You can chose to use a rather inefficient pure-perl implementation by
		414	loading the C<AnyEvent::Impl::Perl> module, which gives you similar
		415	behaviour everywhere, but letting AnyEvent chose is generally better.
		416
49	=cut	417	=cut
50		418
51	package AnyEvent;	419	package AnyEvent;
52		420
53	no warnings;	421	no warnings;
54	use strict 'vars';	422	use strict;
		423
55	use Carp;	424	use Carp;
56		425
57	our $VERSION = 0.2;	426	our $VERSION = '3.12';
58	our $MODEL;	427	our $MODEL;
59		428
60	our $AUTOLOAD;	429	our $AUTOLOAD;
61	our @ISA;	430	our @ISA;
62		431
		432	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
		433
		434	our @REGISTRY;
		435
63	my @models = (	436	my @models = (
64	[Coro => Coro::Event::],	437	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
65	[Event => Event::],	438	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
66	[Glib => Glib::],	439	[EV:: => AnyEvent::Impl::EV::],
67	[Tk => Tk::],	440	[Event:: => AnyEvent::Impl::Event::],
		441	[Glib:: => AnyEvent::Impl::Glib::],
		442	[Tk:: => AnyEvent::Impl::Tk::],
		443	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
68	);	444	);
		445	my @models_detect = (
		446	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		447	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		448	);
69		449
70	our %method = map +($_ => 1), qw(io timer condvar broadcast wait cancel DESTROY);	450	our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);
71		451
72	sub AUTOLOAD {	452	sub detect() {
73	$AUTOLOAD =~ s/.*://;
74
75	$method{$AUTOLOAD}
76	or croak "$AUTOLOAD: not a valid method for AnyEvent objects";
77
78	unless ($MODEL) {	453	unless ($MODEL) {
79	# check for already loaded models	454	no strict 'refs';
80	for (@models) {	455
81	my ($model, $package) = @$_;	456	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
82	if (scalar keys %{ *{"$package\::"} }) {	457	my $model = "AnyEvent::Impl::$1";
83	eval "require AnyEvent::Impl::$model";	458	if (eval "require $model") {
84	last if $MODEL;	459	$MODEL = $model;
		460	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;
85	}	461	}
86	}	462	}
87		463
		464	# check for already loaded models
88	unless ($MODEL) {	465	unless ($MODEL) {
89	# try to load a model	466	for (@REGISTRY, @models, @models_detect) {
90
91	for (@models) {
92	my ($model, $package) = @$_;	467	my ($package, $model) = @$_;
93	eval "require AnyEvent::Impl::$model";	468	if (${"$package\::VERSION"} > 0) {
94	last if $MODEL;	469	if (eval "require $model") {
		470	$MODEL = $model;
		471	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;
		472	last;
		473	}
		474	}
95	}	475	}
96		476
		477	unless ($MODEL) {
		478	# try to load a model
		479
		480	for (@REGISTRY, @models) {
		481	my ($package, $model) = @$_;
		482	if (eval "require $package"
		483	and ${"$package\::VERSION"} > 0
		484	and eval "require $model") {
		485	$MODEL = $model;
		486	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;
		487	last;
		488	}
		489	}
		490
97	$MODEL	491	$MODEL
98	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: Coro, Event, Glib or Tk.";	492	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.";
		493	}
99	}	494	}
		495
		496	unshift @ISA, $MODEL;
		497	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
100	}	498	}
101		499
102	@ISA = $MODEL;	500	$MODEL
		501	}
		502
		503	sub AUTOLOAD {
		504	(my $func = $AUTOLOAD) =~ s/.*://;
		505
		506	$method{$func}
		507	or croak "$func: not a valid method for AnyEvent objects";
		508
		509	detect unless $MODEL;
103		510
104	my $class = shift;	511	my $class = shift;
105	$class->$AUTOLOAD (@_);	512	$class->$func (@_);
106	}	513	}
		514
		515	package AnyEvent::Base;
		516
		517	# default implementation for ->condvar, ->wait, ->broadcast
		518
		519	sub condvar {
		520	bless \my $flag, "AnyEvent::Base::CondVar"
		521	}
		522
		523	sub AnyEvent::Base::CondVar::broadcast {
		524	${$_[0]}++;
		525	}
		526
		527	sub AnyEvent::Base::CondVar::wait {
		528	AnyEvent->one_event while !${$_[0]};
		529	}
		530
		531	# default implementation for ->signal
		532
		533	our %SIG_CB;
		534
		535	sub signal {
		536	my (undef, %arg) = @_;
		537
		538	my $signal = uc $arg{signal}
		539	or Carp::croak "required option 'signal' is missing";
		540
		541	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		542	$SIG{$signal} \|\|= sub {
		543	$_->() for values %{ $SIG_CB{$signal} \|\| {} };
		544	};
		545
		546	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"
		547	}
		548
		549	sub AnyEvent::Base::Signal::DESTROY {
		550	my ($signal, $cb) = @{$_[0]};
		551
		552	delete $SIG_CB{$signal}{$cb};
		553
		554	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };
		555	}
		556
		557	# default implementation for ->child
		558
		559	our %PID_CB;
		560	our $CHLD_W;
		561	our $CHLD_DELAY_W;
		562	our $PID_IDLE;
		563	our $WNOHANG;
		564
		565	sub _child_wait {
		566	while (0 < (my $pid = waitpid -1, $WNOHANG)) {
		567	$_->($pid, $?) for (values %{ $PID_CB{$pid} \|\| {} }),
		568	(values %{ $PID_CB{0} \|\| {} });
		569	}
		570
		571	undef $PID_IDLE;
		572	}
		573
		574	sub _sigchld {
		575	# make sure we deliver these changes "synchronous" with the event loop.
		576	$CHLD_DELAY_W \|\|= AnyEvent->timer (after => 0, cb => sub {
		577	undef $CHLD_DELAY_W;
		578	&_child_wait;
		579	});
		580	}
		581
		582	sub child {
		583	my (undef, %arg) = @_;
		584
		585	defined (my $pid = $arg{pid} + 0)
		586	or Carp::croak "required option 'pid' is missing";
		587
		588	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
		589
		590	unless ($WNOHANG) {
		591	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } \|\| 1;
		592	}
		593
		594	unless ($CHLD_W) {
		595	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
		596	# child could be a zombie already, so make at least one round
		597	&_sigchld;
		598	}
		599
		600	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"
		601	}
		602
		603	sub AnyEvent::Base::Child::DESTROY {
		604	my ($pid, $cb) = @{$_[0]};
		605
		606	delete $PID_CB{$pid}{$cb};
		607	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
		608
		609	undef $CHLD_W unless keys %PID_CB;
		610	}
		611
		612	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
		613
		614	This is an advanced topic that you do not normally need to use AnyEvent in
		615	a module. This section is only of use to event loop authors who want to
		616	provide AnyEvent compatibility.
		617
		618	If you need to support another event library which isn't directly
		619	supported by AnyEvent, you can supply your own interface to it by
		620	pushing, before the first watcher gets created, the package name of
		621	the event module and the package name of the interface to use onto
		622	C<@AnyEvent::REGISTRY>. You can do that before and even without loading
		623	AnyEvent, so it is reasonably cheap.
		624
		625	Example:
		626
		627	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
		628
		629	This tells AnyEvent to (literally) use the C<urxvt::anyevent::>
		630	package/class when it finds the C<urxvt> package/module is already loaded.
		631
		632	When AnyEvent is loaded and asked to find a suitable event model, it
		633	will first check for the presence of urxvt by trying to C<use> the
		634	C<urxvt::anyevent> module.
		635
		636	The class should provide implementations for all watcher types. See
		637	L<AnyEvent::Impl::EV> (source code), L<AnyEvent::Impl::Glib> (Source code)
		638	and so on for actual examples. Use C<perldoc -m AnyEvent::Impl::Glib> to
		639	see the sources.
		640
		641	If you don't provide C<signal> and C<child> watchers than AnyEvent will
		642	provide suitable (hopefully) replacements.
		643
		644	The above example isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt)
		645	terminal emulator uses the above line as-is. An interface isn't included
		646	in AnyEvent because it doesn't make sense outside the embedded interpreter
		647	inside I<rxvt-unicode>, and it is updated and maintained as part of the
		648	I<rxvt-unicode> distribution.
		649
		650	I<rxvt-unicode> also cheats a bit by not providing blocking access to
		651	condition variables: code blocking while waiting for a condition will
		652	C<die>. This still works with most modules/usages, and blocking calls must
		653	not be done in an interactive application, so it makes sense.
		654
		655	=head1 ENVIRONMENT VARIABLES
		656
		657	The following environment variables are used by this module:
		658
		659	=over 4
		660
		661	=item C<PERL_ANYEVENT_VERBOSE>
		662
		663	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		664	model it chooses.
		665
		666	=item C<PERL_ANYEVENT_MODEL>
		667
		668	This can be used to specify the event model to be used by AnyEvent, before
		669	autodetection and -probing kicks in. It must be a string consisting
		670	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		671	and the resulting module name is loaded and if the load was successful,
		672	used as event model. If it fails to load AnyEvent will proceed with
		673	autodetection and -probing.
		674
		675	This functionality might change in future versions.
		676
		677	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		678	could start your program like this:
		679
		680	PERL_ANYEVENT_MODEL=Perl perl ...
107		681
108	=back	682	=back
109		683
110	=head1 EXAMPLE	684	=head1 EXAMPLE PROGRAM
111		685
112	The following program uses an io watcher to read data from stdin, a timer	686	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	687	to display a message once per second, and a condition variable to quit the
114	when the user enters quit:	688	program when the user enters quit:
115		689
116	use AnyEvent;	690	use AnyEvent;
117		691
118	my $cv = AnyEvent->condvar;	692	my $cv = AnyEvent->condvar;
119		693
120	my $io_watcher = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {	694	my $io_watcher = AnyEvent->io (
		695	fh => \*STDIN,
		696	poll => 'r',
		697	cb => sub {
121	warn "io event <$_[0]>\n"; # will always output <r>	698	warn "io event <$_[0]>\n"; # will always output <r>
122	chomp (my $input = <STDIN>); # read a line	699	chomp (my $input = <STDIN>); # read a line
123	warn "read: $input\n"; # output what has been read	700	warn "read: $input\n"; # output what has been read
124	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i	701	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i
		702	},
125	});	703	);
126		704
127	my $time_watcher; # can only be used once	705	my $time_watcher; # can only be used once
128		706
129	sub new_timer {	707	sub new_timer {
130	$timer = AnyEvent->timer (after => 1, cb => sub {	708	$timer = AnyEvent->timer (after => 1, cb => sub {
135		713
136	new_timer; # create first timer	714	new_timer; # create first timer
137		715
138	$cv->wait; # wait until user enters /^q/i	716	$cv->wait; # wait until user enters /^q/i
139		717
		718	=head1 REAL-WORLD EXAMPLE
		719
		720	Consider the L<Net::FCP> module. It features (among others) the following
		721	API calls, which are to freenet what HTTP GET requests are to http:
		722
		723	my $data = $fcp->client_get ($url); # blocks
		724
		725	my $transaction = $fcp->txn_client_get ($url); # does not block
		726	$transaction->cb ( sub { ... } ); # set optional result callback
		727	my $data = $transaction->result; # possibly blocks
		728
		729	The C<client_get> method works like C<LWP::Simple::get>: it requests the
		730	given URL and waits till the data has arrived. It is defined to be:
		731
		732	sub client_get { $_[0]->txn_client_get ($_[1])->result }
		733
		734	And in fact is automatically generated. This is the blocking API of
		735	L<Net::FCP>, and it works as simple as in any other, similar, module.
		736
		737	More complicated is C<txn_client_get>: It only creates a transaction
		738	(completion, result, ...) object and initiates the transaction.
		739
		740	my $txn = bless { }, Net::FCP::Txn::;
		741
		742	It also creates a condition variable that is used to signal the completion
		743	of the request:
		744
		745	$txn->{finished} = AnyAvent->condvar;
		746
		747	It then creates a socket in non-blocking mode.
		748
		749	socket $txn->{fh}, ...;
		750	fcntl $txn->{fh}, F_SETFL, O_NONBLOCK;
		751	connect $txn->{fh}, ...
		752	and !$!{EWOULDBLOCK}
		753	and !$!{EINPROGRESS}
		754	and Carp::croak "unable to connect: $!\n";
		755
		756	Then it creates a write-watcher which gets called whenever an error occurs
		757	or the connection succeeds:
		758
		759	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'w', cb => sub { $txn->fh_ready_w });
		760
		761	And returns this transaction object. The C<fh_ready_w> callback gets
		762	called as soon as the event loop detects that the socket is ready for
		763	writing.
		764
		765	The C<fh_ready_w> method makes the socket blocking again, writes the
		766	request data and replaces the watcher by a read watcher (waiting for reply
		767	data). The actual code is more complicated, but that doesn't matter for
		768	this example:
		769
		770	fcntl $txn->{fh}, F_SETFL, 0;
		771	syswrite $txn->{fh}, $txn->{request}
		772	or die "connection or write error";
		773	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
		774
		775	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
		776	result and signals any possible waiters that the request ahs finished:
		777
		778	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
		779
		780	if (end-of-file or data complete) {
		781	$txn->{result} = $txn->{buf};
		782	$txn->{finished}->broadcast;
		783	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
		784	}
		785
		786	The C<result> method, finally, just waits for the finished signal (if the
		787	request was already finished, it doesn't wait, of course, and returns the
		788	data:
		789
		790	$txn->{finished}->wait;
		791	return $txn->{result};
		792
		793	The actual code goes further and collects all errors (C<die>s, exceptions)
		794	that occured during request processing. The C<result> method detects
		795	whether an exception as thrown (it is stored inside the $txn object)
		796	and just throws the exception, which means connection errors and other
		797	problems get reported tot he code that tries to use the result, not in a
		798	random callback.
		799
		800	All of this enables the following usage styles:
		801
		802	1. Blocking:
		803
		804	my $data = $fcp->client_get ($url);
		805
		806	2. Blocking, but running in parallel:
		807
		808	my @datas = map $_->result,
		809	map $fcp->txn_client_get ($_),
		810	@urls;
		811
		812	Both blocking examples work without the module user having to know
		813	anything about events.
		814
		815	3a. Event-based in a main program, using any supported event module:
		816
		817	use EV;
		818
		819	$fcp->txn_client_get ($url)->cb (sub {
		820	my $txn = shift;
		821	my $data = $txn->result;
		822	...
		823	});
		824
		825	EV::loop;
		826
		827	3b. The module user could use AnyEvent, too:
		828
		829	use AnyEvent;
		830
		831	my $quit = AnyEvent->condvar;
		832
		833	$fcp->txn_client_get ($url)->cb (sub {
		834	...
		835	$quit->broadcast;
		836	});
		837
		838	$quit->wait;
		839
		840	=head1 FORK
		841
		842	Most event libraries are not fork-safe. The ones who are usually are
		843	because they are so inefficient. Only L<EV> is fully fork-aware.
		844
		845	If you have to fork, you must either do so I<before> creating your first
		846	watcher OR you must not use AnyEvent at all in the child.
		847
		848	=head1 SECURITY CONSIDERATIONS
		849
		850	AnyEvent can be forced to load any event model via
		851	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
		852	execute arbitrary code or directly gain access, it can easily be used to
		853	make the program hang or malfunction in subtle ways, as AnyEvent watchers
		854	will not be active when the program uses a different event model than
		855	specified in the variable.
		856
		857	You can make AnyEvent completely ignore this variable by deleting it
		858	before the first watcher gets created, e.g. with a C<BEGIN> block:
		859
		860	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
		861
		862	use AnyEvent;
		863
140	=head1 SEE ALSO	864	=head1 SEE ALSO
141		865
		866	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>,	867	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,
143	L<AnyEvent::Impl::Coro>,	868	L<Event::Lib>, L<Qt>.
144	L<AnyEvent::Impl::Event>,	869
145	L<AnyEvent::Impl::Glib>,	870	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,
		871	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,
		872	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,
146	L<AnyEvent::Impl::Tk>.	873	L<AnyEvent::Impl::Qt>.
147		874
148	=head1	875	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.
		876
		877	=head1 AUTHOR
		878
		879	Marc Lehmann <schmorp@schmorp.de>
		880	http://home.schmorp.de/
149		881
150	=cut	882	=cut
151		883
152	1	884	1
153		885

Diff Legend

-–
+Removed lines
-+
+Added lines
-<
+Changed lines
->
+Changed lines

Comparing AnyEvent/lib/AnyEvent.pm (file contents): Revision 1.4 by root, Thu Dec 1 22:04:50 2005 UTC vs. Revision 1.57 by root, Thu Apr 24 03:19:28 2008 UTC

Diff Legend

Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.4 by root, Thu Dec 1 22:04:50 2005 UTC vs.
Revision 1.57 by root, Thu Apr 24 03:19:28 2008 UTC