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

Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.1 by root, Wed Apr 27 01:26:44 2005 UTC vs.
Revision 1.63 by root, Fri Apr 25 02:03:38 2008 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	AnyEvent - ???	3	AnyEvent - provide framework for multiple event loops
		4
		5	EV, Event, Coro::EV, Coro::Event, Glib, Tk, Perl, Event::Lib, Qt, POE - various supported event loops
4		6
5	=head1 SYNOPSIS	7	=head1 SYNOPSIS
6		8
		9	use AnyEvent;
		10
		11	my $w = AnyEvent->io (fh => $fh, poll => "r\|w", cb => sub {
		12	...
		13	});
		14
		15	my $w = AnyEvent->timer (after => $seconds, cb => sub {
		16	...
		17	});
		18
		19	my $w = AnyEvent->condvar; # stores whether a condition was flagged
		20	$w->wait; # enters "main loop" till $condvar gets ->broadcast
		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
		71
7	=head1 DESCRIPTION	72	=head1 DESCRIPTION
8		73
		74	L<AnyEvent> provides an identical interface to multiple event loops. This
		75	allows module authors to utilise an event loop without forcing module
		76	users to use the same event loop (as only a single event loop can coexist
		77	peacefully at any one time).
		78
		79	The interface itself is vaguely similar, but not identical to the L<Event>
		80	module.
		81
		82	During the first call of any watcher-creation method, the module tries
		83	to detect the currently loaded event loop by probing whether one of the
		84	following modules is already loaded: L<Coro::EV>, L<Coro::Event>, L<EV>,
		85	L<Event>, L<Glib>, L<Tk>, L<AnyEvent::Impl::Perl>, L<Event::Lib>, L<Qt>,
		86	L<POE>. The first one found is used. If none are found, the module tries
		87	to load these modules (excluding 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 IO 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 for
		147	events. C<poll> must be a string that is either C<r> or C<w>, which
		148	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	As long as the I/O watcher exists it will keep the file descriptor or a
		153	copy of it alive/open.
		154
		155	It is not allowed to close a file handle as long as any watcher is active
		156	on the underlying file descriptor.
		157
		158	Some event loops issue spurious readyness notifications, so you should
		159	always use non-blocking calls when reading/writing from/to your file
		160	handles.
		161
		162	Example:
		163
		164	# wait for readability of STDIN, then read a line and disable the watcher
		165	my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
		166	chomp (my $input = <STDIN>);
		167	warn "read: $input\n";
		168	undef $w;
		169	});
		170
		171	=head2 TIME WATCHERS
		172
		173	You can create a time watcher by calling the C<< AnyEvent->timer >>
		174	method with the following mandatory arguments:
		175
		176	C<after> specifies after how many seconds (fractional values are
		177	supported) should the timer activate. C<cb> the callback to invoke in that
		178	case.
		179
		180	The timer callback will be invoked at most once: if you want a repeating
		181	timer you have to create a new watcher (this is a limitation by both Tk
		182	and Glib).
		183
		184	Example:
		185
		186	# fire an event after 7.7 seconds
		187	my $w = AnyEvent->timer (after => 7.7, cb => sub {
		188	warn "timeout\n";
		189	});
		190
		191	# to cancel the timer:
		192	undef $w;
		193
		194	Example 2:
		195
		196	# fire an event after 0.5 seconds, then roughly every second
		197	my $w;
		198
		199	my $cb = sub {
		200	# cancel the old timer while creating a new one
		201	$w = AnyEvent->timer (after => 1, cb => $cb);
		202	};
		203
		204	# start the "loop" by creating the first watcher
		205	$w = AnyEvent->timer (after => 0.5, cb => $cb);
		206
		207	=head3 TIMING ISSUES
		208
		209	There are two ways to handle timers: based on real time (relative, "fire
		210	in 10 seconds") and based on wallclock time (absolute, "fire at 12
		211	o'clock").
		212
		213	While most event loops expect timers to specified in a relative way, they
		214	use absolute time internally. This makes a difference when your clock
		215	"jumps", for example, when ntp decides to set your clock backwards from
		216	the wrong date of 2014-01-01 to 2008-01-01, a watcher that is supposed to
		217	fire "after" a second might actually take six years to finally fire.
		218
		219	AnyEvent cannot compensate for this. The only event loop that is conscious
		220	about these issues is L<EV>, which offers both relative (ev_timer, based
		221	on true relative time) and absolute (ev_periodic, based on wallclock time)
		222	timers.
		223
		224	AnyEvent always prefers relative timers, if available, matching the
		225	AnyEvent API.
		226
		227	=head2 SIGNAL WATCHERS
		228
		229	You can watch for signals using a signal watcher, C<signal> is the signal
		230	I<name> without any C<SIG> prefix, C<cb> is the Perl callback to
		231	be invoked whenever a signal occurs.
		232
		233	Multiple signal occurances can be clumped together into one callback
		234	invocation, and callback invocation will be synchronous. synchronous means
		235	that it might take a while until the signal gets handled by the process,
		236	but it is guarenteed not to interrupt any other callbacks.
		237
		238	The main advantage of using these watchers is that you can share a signal
		239	between multiple watchers.
		240
		241	This watcher might use C<%SIG>, so programs overwriting those signals
		242	directly will likely not work correctly.
		243
		244	Example: exit on SIGINT
		245
		246	my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
		247
		248	=head2 CHILD PROCESS WATCHERS
		249
		250	You can also watch on a child process exit and catch its exit status.
		251
		252	The child process is specified by the C<pid> argument (if set to C<0>, it
		253	watches for any child process exit). The watcher will trigger as often
		254	as status change for the child are received. This works by installing a
		255	signal handler for C<SIGCHLD>. The callback will be called with the pid
		256	and exit status (as returned by waitpid).
		257
		258	Example: wait for pid 1333
		259
		260	my $w = AnyEvent->child (
		261	pid => 1333,
		262	cb => sub {
		263	my ($pid, $status) = @_;
		264	warn "pid $pid exited with status $status";
		265	},
		266	);
		267
		268	=head2 CONDITION VARIABLES
		269
		270	Condition variables can be created by calling the C<< AnyEvent->condvar >>
		271	method without any arguments.
		272
		273	A condition variable waits for a condition - precisely that the C<<
		274	->broadcast >> method has been called.
		275
		276	They are very useful to signal that a condition has been fulfilled, for
		277	example, if you write a module that does asynchronous http requests,
		278	then a condition variable would be the ideal candidate to signal the
		279	availability of results.
		280
		281	You can also use condition variables to block your main program until
		282	an event occurs - for example, you could C<< ->wait >> in your main
		283	program until the user clicks the Quit button in your app, which would C<<
		284	->broadcast >> the "quit" event.
		285
		286	Note that condition variables recurse into the event loop - if you have
		287	two pirces of code that call C<< ->wait >> in a round-robbin fashion, you
		288	lose. Therefore, condition variables are good to export to your caller, but
		289	you should avoid making a blocking wait yourself, at least in callbacks,
		290	as this asks for trouble.
		291
		292	This object has two methods:
		293
9	=over 4	294	=over 4
10		295
		296	=item $cv->wait
		297
		298	Wait (blocking if necessary) until the C<< ->broadcast >> method has been
		299	called on c<$cv>, while servicing other watchers normally.
		300
		301	You can only wait once on a condition - additional calls will return
		302	immediately.
		303
		304	Not all event models support a blocking wait - some die in that case
		305	(programs might want to do that to stay interactive), so I<if you are
		306	using this from a module, never require a blocking wait>, but let the
		307	caller decide whether the call will block or not (for example, by coupling
		308	condition variables with some kind of request results and supporting
		309	callbacks so the caller knows that getting the result will not block,
		310	while still suppporting blocking waits if the caller so desires).
		311
		312	Another reason I<never> to C<< ->wait >> in a module is that you cannot
		313	sensibly have two C<< ->wait >>'s in parallel, as that would require
		314	multiple interpreters or coroutines/threads, none of which C<AnyEvent>
		315	can supply (the coroutine-aware backends L<AnyEvent::Impl::CoroEV> and
		316	L<AnyEvent::Impl::CoroEvent> explicitly support concurrent C<< ->wait >>'s
		317	from different coroutines, however).
		318
		319	=item $cv->broadcast
		320
		321	Flag the condition as ready - a running C<< ->wait >> and all further
		322	calls to C<wait> will (eventually) return after this method has been
		323	called. If nobody is waiting the broadcast will be remembered..
		324
		325	=back
		326
		327	Example:
		328
		329	# wait till the result is ready
		330	my $result_ready = AnyEvent->condvar;
		331
		332	# do something such as adding a timer
		333	# or socket watcher the calls $result_ready->broadcast
		334	# when the "result" is ready.
		335	# in this case, we simply use a timer:
		336	my $w = AnyEvent->timer (
		337	after => 1,
		338	cb => sub { $result_ready->broadcast },
		339	);
		340
		341	# this "blocks" (while handling events) till the watcher
		342	# calls broadcast
		343	$result_ready->wait;
		344
		345	=head1 GLOBAL VARIABLES AND FUNCTIONS
		346
		347	=over 4
		348
		349	=item $AnyEvent::MODEL
		350
		351	Contains C<undef> until the first watcher is being created. Then it
		352	contains the event model that is being used, which is the name of the
		353	Perl class implementing the model. This class is usually one of the
		354	C<AnyEvent::Impl:xxx> modules, but can be any other class in the case
		355	AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).
		356
		357	The known classes so far are:
		358
		359	AnyEvent::Impl::CoroEV based on Coro::EV, best choice.
		360	AnyEvent::Impl::CoroEvent based on Coro::Event, second best choice.
		361	AnyEvent::Impl::EV based on EV (an interface to libev, best choice).
		362	AnyEvent::Impl::Event based on Event, second best choice.
		363	AnyEvent::Impl::Glib based on Glib, third-best choice.
		364	AnyEvent::Impl::Tk based on Tk, very bad choice.
		365	AnyEvent::Impl::Perl pure-perl implementation, inefficient but portable.
		366	AnyEvent::Impl::Qt based on Qt, cannot be autoprobed (see its docs).
		367	AnyEvent::Impl::EventLib based on Event::Lib, leaks memory and worse.
		368	AnyEvent::Impl::POE based on POE, not generic enough for full support.
		369
		370	There is no support for WxWidgets, as WxWidgets has no support for
		371	watching file handles. However, you can use WxWidgets through the
		372	POE Adaptor, as POE has a Wx backend that simply polls 20 times per
		373	second, which was considered to be too horrible to even consider for
		374	AnyEvent. Likewise, other POE backends can be used by AnyEvent by using
		375	it's adaptor.
		376
		377	AnyEvent knows about L<Prima> and L<Wx> and will try to use L<POE> when
		378	autodetecting them.
		379
		380	=item AnyEvent::detect
		381
		382	Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model
		383	if necessary. You should only call this function right before you would
		384	have created an AnyEvent watcher anyway, that is, as late as possible at
		385	runtime.
		386
		387	=back
		388
		389	=head1 WHAT TO DO IN A MODULE
		390
		391	As a module author, you should C<use AnyEvent> and call AnyEvent methods
		392	freely, but you should not load a specific event module or rely on it.
		393
		394	Be careful when you create watchers in the module body - AnyEvent will
		395	decide which event module to use as soon as the first method is called, so
		396	by calling AnyEvent in your module body you force the user of your module
		397	to load the event module first.
		398
		399	Never call C<< ->wait >> on a condition variable unless you I<know> that
		400	the C<< ->broadcast >> method has been called on it already. This is
		401	because it will stall the whole program, and the whole point of using
		402	events is to stay interactive.
		403
		404	It is fine, however, to call C<< ->wait >> when the user of your module
		405	requests it (i.e. if you create a http request object ad have a method
		406	called C<results> that returns the results, it should call C<< ->wait >>
		407	freely, as the user of your module knows what she is doing. always).
		408
		409	=head1 WHAT TO DO IN THE MAIN PROGRAM
		410
		411	There will always be a single main program - the only place that should
		412	dictate which event model to use.
		413
		414	If it doesn't care, it can just "use AnyEvent" and use it itself, or not
		415	do anything special (it does not need to be event-based) and let AnyEvent
		416	decide which implementation to chose if some module relies on it.
		417
		418	If the main program relies on a specific event model. For example, in
		419	Gtk2 programs you have to rely on the Glib module. You should load the
		420	event module before loading AnyEvent or any module that uses it: generally
		421	speaking, you should load it as early as possible. The reason is that
		422	modules might create watchers when they are loaded, and AnyEvent will
		423	decide on the event model to use as soon as it creates watchers, and it
		424	might chose the wrong one unless you load the correct one yourself.
		425
		426	You can chose to use a rather inefficient pure-perl implementation by
		427	loading the C<AnyEvent::Impl::Perl> module, which gives you similar
		428	behaviour everywhere, but letting AnyEvent chose is generally better.
		429
11	=cut	430	=cut
12		431
13	package AnyEvent;	432	package AnyEvent;
14		433
		434	no warnings;
		435	use strict;
		436
15	use Carp;	437	use Carp;
16		438
17	$VERSION = 0.1;	439	our $VERSION = '3.3';
		440	our $MODEL;
18		441
19	no warnings;	442	our $AUTOLOAD;
		443	our @ISA;
		444
		445	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
		446
		447	our @REGISTRY;
20		448
21	my @models = (	449	my @models = (
22	[Coro => Coro::Event::],	450	[Coro::EV:: => AnyEvent::Impl::CoroEV::],
23	[Event => Event::],	451	[Coro::Event:: => AnyEvent::Impl::CoroEvent::],
24	[Glib => Glib::],	452	[EV:: => AnyEvent::Impl::EV::],
25	[Tk => Tk::],	453	[Event:: => AnyEvent::Impl::Event::],
		454	[Glib:: => AnyEvent::Impl::Glib::],
		455	[Tk:: => AnyEvent::Impl::Tk::],
		456	[Wx:: => AnyEvent::Impl::POE::],
		457	[Prima:: => AnyEvent::Impl::POE::],
		458	[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
		459	# everything below here will not be autoprobed as the pureperl backend should work everywhere
		460	[Event::Lib:: => AnyEvent::Impl::EventLib::], # too buggy
		461	[Qt:: => AnyEvent::Impl::Qt::], # requires special main program
		462	[POE::Kernel:: => AnyEvent::Impl::POE::], # lasciate ogni speranza
26	);	463	);
27		464
		465	our %method = map +($_ => 1), qw(io timer signal child condvar broadcast wait one_event DESTROY);
		466
		467	sub detect() {
		468	unless ($MODEL) {
		469	no strict 'refs';
		470
		471	if ($ENV{PERL_ANYEVENT_MODEL} =~ /^([a-zA-Z]+)$/) {
		472	my $model = "AnyEvent::Impl::$1";
		473	if (eval "require $model") {
		474	$MODEL = $model;
		475	warn "AnyEvent: loaded model '$model' (forced by \$PERL_ANYEVENT_MODEL), using it.\n" if $verbose > 1;
		476	} else {
		477	warn "AnyEvent: unable to load model '$model' (from \$PERL_ANYEVENT_MODEL):\n$@" if $verbose;
		478	}
		479	}
		480
		481	# check for already loaded models
		482	unless ($MODEL) {
		483	for (@REGISTRY, @models) {
		484	my ($package, $model) = @$_;
		485	if (${"$package\::VERSION"} > 0) {
		486	if (eval "require $model") {
		487	$MODEL = $model;
		488	warn "AnyEvent: autodetected model '$model', using it.\n" if $verbose > 1;
		489	last;
		490	}
		491	}
		492	}
		493
		494	unless ($MODEL) {
		495	# try to load a model
		496
		497	for (@REGISTRY, @models) {
		498	my ($package, $model) = @$_;
		499	if (eval "require $package"
		500	and ${"$package\::VERSION"} > 0
		501	and eval "require $model") {
		502	$MODEL = $model;
		503	warn "AnyEvent: autoprobed model '$model', using it.\n" if $verbose > 1;
		504	last;
		505	}
		506	}
		507
		508	$MODEL
		509	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.";
		510	}
		511	}
		512
		513	unshift @ISA, $MODEL;
		514	push @{"$MODEL\::ISA"}, "AnyEvent::Base";
		515	}
		516
		517	$MODEL
		518	}
		519
28	sub AUTOLOAD {	520	sub AUTOLOAD {
29	$AUTOLOAD =~ s/.*://;	521	(my $func = $AUTOLOAD) =~ s/.*://;
30		522
31	for (@models) {	523	$method{$func}
32	my ($model, $package) = @$_;	524	or croak "$func: not a valid method for AnyEvent objects";
33	if (defined ${"$package\::VERSION"}) {	525
34	$EVENT = "AnyEvent::Impl::$model";	526	detect unless $MODEL;
35	eval "require $EVENT"; die if $@;	527
36	goto &{"$EVENT\::$AUTOLOAD"};	528	my $class = shift;
37	}	529	$class->$func (@_);
		530	}
		531
		532	package AnyEvent::Base;
		533
		534	# default implementation for ->condvar, ->wait, ->broadcast
		535
		536	sub condvar {
		537	bless \my $flag, "AnyEvent::Base::CondVar"
		538	}
		539
		540	sub AnyEvent::Base::CondVar::broadcast {
		541	${$_[0]}++;
		542	}
		543
		544	sub AnyEvent::Base::CondVar::wait {
		545	AnyEvent->one_event while !${$_[0]};
		546	}
		547
		548	# default implementation for ->signal
		549
		550	our %SIG_CB;
		551
		552	sub signal {
		553	my (undef, %arg) = @_;
		554
		555	my $signal = uc $arg{signal}
		556	or Carp::croak "required option 'signal' is missing";
		557
		558	$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
		559	$SIG{$signal} \|\|= sub {
		560	$_->() for values %{ $SIG_CB{$signal} \|\| {} };
		561	};
		562
		563	bless [$signal, $arg{cb}], "AnyEvent::Base::Signal"
		564	}
		565
		566	sub AnyEvent::Base::Signal::DESTROY {
		567	my ($signal, $cb) = @{$_[0]};
		568
		569	delete $SIG_CB{$signal}{$cb};
		570
		571	$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };
		572	}
		573
		574	# default implementation for ->child
		575
		576	our %PID_CB;
		577	our $CHLD_W;
		578	our $CHLD_DELAY_W;
		579	our $PID_IDLE;
		580	our $WNOHANG;
		581
		582	sub _child_wait {
		583	while (0 < (my $pid = waitpid -1, $WNOHANG)) {
		584	$_->($pid, $?) for (values %{ $PID_CB{$pid} \|\| {} }),
		585	(values %{ $PID_CB{0} \|\| {} });
38	}	586	}
39		587
40	for (@models) {	588	undef $PID_IDLE;
41	my ($model, $package) = @$_;	589	}
42	$EVENT = "AnyEvent::Impl::$model";	590
43	if (eval "require $EVENT") {	591	sub _sigchld {
44	goto &{"$EVENT\::$AUTOLOAD"};	592	# make sure we deliver these changes "synchronous" with the event loop.
45	}	593	$CHLD_DELAY_W \|\|= AnyEvent->timer (after => 0, cb => sub {
		594	undef $CHLD_DELAY_W;
		595	&_child_wait;
		596	});
		597	}
		598
		599	sub child {
		600	my (undef, %arg) = @_;
		601
		602	defined (my $pid = $arg{pid} + 0)
		603	or Carp::croak "required option 'pid' is missing";
		604
		605	$PID_CB{$pid}{$arg{cb}} = $arg{cb};
		606
		607	unless ($WNOHANG) {
		608	$WNOHANG = eval { require POSIX; &POSIX::WNOHANG } \|\| 1;
46	}	609	}
47		610
48	die "No event module selected for AnyEvent and autodetect failed. Install any of these: Coro, Event, Glib or Tk.";	611	unless ($CHLD_W) {
49	}	612	$CHLD_W = AnyEvent->signal (signal => 'CHLD', cb => \&_sigchld);
		613	# child could be a zombie already, so make at least one round
		614	&_sigchld;
		615	}
50		616
51	1;	617	bless [$pid, $arg{cb}], "AnyEvent::Base::Child"
		618	}
52		619
		620	sub AnyEvent::Base::Child::DESTROY {
		621	my ($pid, $cb) = @{$_[0]};
		622
		623	delete $PID_CB{$pid}{$cb};
		624	delete $PID_CB{$pid} unless keys %{ $PID_CB{$pid} };
		625
		626	undef $CHLD_W unless keys %PID_CB;
		627	}
		628
		629	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
		630
		631	This is an advanced topic that you do not normally need to use AnyEvent in
		632	a module. This section is only of use to event loop authors who want to
		633	provide AnyEvent compatibility.
		634
		635	If you need to support another event library which isn't directly
		636	supported by AnyEvent, you can supply your own interface to it by
		637	pushing, before the first watcher gets created, the package name of
		638	the event module and the package name of the interface to use onto
		639	C<@AnyEvent::REGISTRY>. You can do that before and even without loading
		640	AnyEvent, so it is reasonably cheap.
		641
		642	Example:
		643
		644	push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
		645
		646	This tells AnyEvent to (literally) use the C<urxvt::anyevent::>
		647	package/class when it finds the C<urxvt> package/module is already loaded.
		648
		649	When AnyEvent is loaded and asked to find a suitable event model, it
		650	will first check for the presence of urxvt by trying to C<use> the
		651	C<urxvt::anyevent> module.
		652
		653	The class should provide implementations for all watcher types. See
		654	L<AnyEvent::Impl::EV> (source code), L<AnyEvent::Impl::Glib> (Source code)
		655	and so on for actual examples. Use C<perldoc -m AnyEvent::Impl::Glib> to
		656	see the sources.
		657
		658	If you don't provide C<signal> and C<child> watchers than AnyEvent will
		659	provide suitable (hopefully) replacements.
		660
		661	The above example isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt)
		662	terminal emulator uses the above line as-is. An interface isn't included
		663	in AnyEvent because it doesn't make sense outside the embedded interpreter
		664	inside I<rxvt-unicode>, and it is updated and maintained as part of the
		665	I<rxvt-unicode> distribution.
		666
		667	I<rxvt-unicode> also cheats a bit by not providing blocking access to
		668	condition variables: code blocking while waiting for a condition will
		669	C<die>. This still works with most modules/usages, and blocking calls must
		670	not be done in an interactive application, so it makes sense.
		671
		672	=head1 ENVIRONMENT VARIABLES
		673
		674	The following environment variables are used by this module:
		675
		676	=over 4
		677
		678	=item C<PERL_ANYEVENT_VERBOSE>
		679
		680	By default, AnyEvent will be completely silent except in fatal
		681	conditions. You can set this environment variable to make AnyEvent more
		682	talkative.
		683
		684	When set to C<1> or higher, causes AnyEvent to warn about unexpected
		685	conditions, such as not being able to load the event model specified by
		686	C<PERL_ANYEVENT_MODEL>.
		687
		688	When set to C<2> or higher, cause AnyEvent to report to STDERR which event
		689	model it chooses.
		690
		691	=item C<PERL_ANYEVENT_MODEL>
		692
		693	This can be used to specify the event model to be used by AnyEvent, before
		694	autodetection and -probing kicks in. It must be a string consisting
		695	entirely of ASCII letters. The string C<AnyEvent::Impl::> gets prepended
		696	and the resulting module name is loaded and if the load was successful,
		697	used as event model. If it fails to load AnyEvent will proceed with
		698	autodetection and -probing.
		699
		700	This functionality might change in future versions.
		701
		702	For example, to force the pure perl model (L<AnyEvent::Impl::Perl>) you
		703	could start your program like this:
		704
		705	PERL_ANYEVENT_MODEL=Perl perl ...
		706
		707	=back
		708
		709	=head1 EXAMPLE PROGRAM
		710
		711	The following program uses an IO watcher to read data from STDIN, a timer
		712	to display a message once per second, and a condition variable to quit the
		713	program when the user enters quit:
		714
		715	use AnyEvent;
		716
		717	my $cv = AnyEvent->condvar;
		718
		719	my $io_watcher = AnyEvent->io (
		720	fh => \*STDIN,
		721	poll => 'r',
		722	cb => sub {
		723	warn "io event <$_[0]>\n"; # will always output <r>
		724	chomp (my $input = <STDIN>); # read a line
		725	warn "read: $input\n"; # output what has been read
		726	$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i
		727	},
		728	);
		729
		730	my $time_watcher; # can only be used once
		731
		732	sub new_timer {
		733	$timer = AnyEvent->timer (after => 1, cb => sub {
		734	warn "timeout\n"; # print 'timeout' about every second
		735	&new_timer; # and restart the time
		736	});
		737	}
		738
		739	new_timer; # create first timer
		740
		741	$cv->wait; # wait until user enters /^q/i
		742
		743	=head1 REAL-WORLD EXAMPLE
		744
		745	Consider the L<Net::FCP> module. It features (among others) the following
		746	API calls, which are to freenet what HTTP GET requests are to http:
		747
		748	my $data = $fcp->client_get ($url); # blocks
		749
		750	my $transaction = $fcp->txn_client_get ($url); # does not block
		751	$transaction->cb ( sub { ... } ); # set optional result callback
		752	my $data = $transaction->result; # possibly blocks
		753
		754	The C<client_get> method works like C<LWP::Simple::get>: it requests the
		755	given URL and waits till the data has arrived. It is defined to be:
		756
		757	sub client_get { $_[0]->txn_client_get ($_[1])->result }
		758
		759	And in fact is automatically generated. This is the blocking API of
		760	L<Net::FCP>, and it works as simple as in any other, similar, module.
		761
		762	More complicated is C<txn_client_get>: It only creates a transaction
		763	(completion, result, ...) object and initiates the transaction.
		764
		765	my $txn = bless { }, Net::FCP::Txn::;
		766
		767	It also creates a condition variable that is used to signal the completion
		768	of the request:
		769
		770	$txn->{finished} = AnyAvent->condvar;
		771
		772	It then creates a socket in non-blocking mode.
		773
		774	socket $txn->{fh}, ...;
		775	fcntl $txn->{fh}, F_SETFL, O_NONBLOCK;
		776	connect $txn->{fh}, ...
		777	and !$!{EWOULDBLOCK}
		778	and !$!{EINPROGRESS}
		779	and Carp::croak "unable to connect: $!\n";
		780
		781	Then it creates a write-watcher which gets called whenever an error occurs
		782	or the connection succeeds:
		783
		784	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'w', cb => sub { $txn->fh_ready_w });
		785
		786	And returns this transaction object. The C<fh_ready_w> callback gets
		787	called as soon as the event loop detects that the socket is ready for
		788	writing.
		789
		790	The C<fh_ready_w> method makes the socket blocking again, writes the
		791	request data and replaces the watcher by a read watcher (waiting for reply
		792	data). The actual code is more complicated, but that doesn't matter for
		793	this example:
		794
		795	fcntl $txn->{fh}, F_SETFL, 0;
		796	syswrite $txn->{fh}, $txn->{request}
		797	or die "connection or write error";
		798	$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
		799
		800	Again, C<fh_ready_r> waits till all data has arrived, and then stores the
		801	result and signals any possible waiters that the request ahs finished:
		802
		803	sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
		804
		805	if (end-of-file or data complete) {
		806	$txn->{result} = $txn->{buf};
		807	$txn->{finished}->broadcast;
		808	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
		809	}
		810
		811	The C<result> method, finally, just waits for the finished signal (if the
		812	request was already finished, it doesn't wait, of course, and returns the
		813	data:
		814
		815	$txn->{finished}->wait;
		816	return $txn->{result};
		817
		818	The actual code goes further and collects all errors (C<die>s, exceptions)
		819	that occured during request processing. The C<result> method detects
		820	whether an exception as thrown (it is stored inside the $txn object)
		821	and just throws the exception, which means connection errors and other
		822	problems get reported tot he code that tries to use the result, not in a
		823	random callback.
		824
		825	All of this enables the following usage styles:
		826
		827	1. Blocking:
		828
		829	my $data = $fcp->client_get ($url);
		830
		831	2. Blocking, but running in parallel:
		832
		833	my @datas = map $_->result,
		834	map $fcp->txn_client_get ($_),
		835	@urls;
		836
		837	Both blocking examples work without the module user having to know
		838	anything about events.
		839
		840	3a. Event-based in a main program, using any supported event module:
		841
		842	use EV;
		843
		844	$fcp->txn_client_get ($url)->cb (sub {
		845	my $txn = shift;
		846	my $data = $txn->result;
		847	...
		848	});
		849
		850	EV::loop;
		851
		852	3b. The module user could use AnyEvent, too:
		853
		854	use AnyEvent;
		855
		856	my $quit = AnyEvent->condvar;
		857
		858	$fcp->txn_client_get ($url)->cb (sub {
		859	...
		860	$quit->broadcast;
		861	});
		862
		863	$quit->wait;
		864
		865	=head1 FORK
		866
		867	Most event libraries are not fork-safe. The ones who are usually are
		868	because they are so inefficient. Only L<EV> is fully fork-aware.
		869
		870	If you have to fork, you must either do so I<before> creating your first
		871	watcher OR you must not use AnyEvent at all in the child.
		872
		873	=head1 SECURITY CONSIDERATIONS
		874
		875	AnyEvent can be forced to load any event model via
		876	$ENV{PERL_ANYEVENT_MODEL}. While this cannot (to my knowledge) be used to
		877	execute arbitrary code or directly gain access, it can easily be used to
		878	make the program hang or malfunction in subtle ways, as AnyEvent watchers
		879	will not be active when the program uses a different event model than
		880	specified in the variable.
		881
		882	You can make AnyEvent completely ignore this variable by deleting it
		883	before the first watcher gets created, e.g. with a C<BEGIN> block:
		884
		885	BEGIN { delete $ENV{PERL_ANYEVENT_MODEL} }
		886
		887	use AnyEvent;
		888
		889	=head1 SEE ALSO
		890
		891	Event modules: L<Coro::EV>, L<EV>, L<EV::Glib>, L<Glib::EV>,
		892	L<Coro::Event>, L<Event>, L<Glib::Event>, L<Glib>, L<Coro>, L<Tk>,
		893	L<Event::Lib>, L<Qt>, L<POE>.
		894
		895	Implementations: L<AnyEvent::Impl::CoroEV>, L<AnyEvent::Impl::EV>,
		896	L<AnyEvent::Impl::CoroEvent>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>,
		897	L<AnyEvent::Impl::Tk>, L<AnyEvent::Impl::Perl>, L<AnyEvent::Impl::EventLib>,
		898	L<AnyEvent::Impl::Qt>, L<AnyEvent::Impl::POE>.
		899
		900	Nontrivial usage examples: L<Net::FCP>, L<Net::XMPP2>.
		901
		902	=head1 AUTHOR
		903
		904	Marc Lehmann <schmorp@schmorp.de>
		905	http://home.schmorp.de/
		906
		907	=cut
		908
		909	1
		910

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Comparing AnyEvent/lib/AnyEvent.pm (file contents): Revision 1.1 by root, Wed Apr 27 01:26:44 2005 UTC vs. Revision 1.63 by root, Fri Apr 25 02:03:38 2008 UTC

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Comparing AnyEvent/lib/AnyEvent.pm (file contents):
Revision 1.1 by root, Wed Apr 27 01:26:44 2005 UTC vs.
Revision 1.63 by root, Fri Apr 25 02:03:38 2008 UTC