AnyEvent/lib/AnyEvent.pm

=head1 NAME

AnyEvent - provide framework for multiple event loops

Event, Coro, Glib, Tk, Perl - various supported event loops

=head1 SYNOPSIS

   use AnyEvent;

   my $w = AnyEvent->io (fh => $fh, poll => "r|w", cb => sub {
      ...
   });

   my $w = AnyEvent->timer (after => $seconds, cb => sub {
      ...
   });

   my $w = AnyEvent->condvar; # stores wether a condition was flagged
   $w->wait; # enters "main loop" till $condvar gets ->broadcast
   $w->broadcast; # wake up current and all future wait's

=head1 DESCRIPTION

L<AnyEvent> provides an identical interface to multiple event loops. This
allows module authors to utilise an event loop without forcing module
users to use the same event loop (as only a single event loop can coexist
peacefully at any one time).

The interface itself is vaguely similar but not identical to the Event
module.

On the first call of any method, the module tries to detect the currently
loaded event loop by probing wether any of the following modules is
loaded: L<Coro::Event>, L<Event>, L<Glib>, L<Tk>. The first one found is
used. If none is found, the module tries to load these modules in the
order given. The first one that could be successfully loaded will be
used. If still none could be found, AnyEvent will fall back to a pure-perl
event loop, which is also not very efficient.

Because AnyEvent first checks for modules that are already loaded, loading
an Event model explicitly before first using AnyEvent will likely make
that model the default. For example:

   use Tk;
   use AnyEvent;

   # .. AnyEvent will likely default to Tk

The pure-perl implementation of AnyEvent is called
C<AnyEvent::Impl::Perl>. Like other event modules you can load it
explicitly.

=head1 WATCHERS

AnyEvent has the central concept of a I<watcher>, which is an object that
stores relevant data for each kind of event you are waiting for, such as
the callback to call, the filehandle to watch, etc.

These watchers are normal Perl objects with normal Perl lifetime. After
creating a watcher it will immediately "watch" for events and invoke
the callback. To disable the watcher you have to destroy it (e.g. by
setting the variable that stores it to C<undef> or otherwise deleting all
references to it).

All watchers are created by calling a method on the C<AnyEvent> class.

=head2 IO WATCHERS

You can create I/O watcher by calling the C<< AnyEvent->io >> method with
the following mandatory arguments:

C<fh> the Perl I<filehandle> (not filedescriptor) to watch for
events. C<poll> must be a string that is either C<r> or C<w>, that creates
a watcher waiting for "r"eadable or "w"ritable events. C<cb> teh callback
to invoke everytime the filehandle becomes ready.

Only one io watcher per C<fh> and C<poll> combination is allowed (i.e. on
a socket you can have one r + one w, not any more (limitation comes from
Tk - if you are sure you are not using Tk this limitation is gone).

Filehandles will be kept alive, so as long as the watcher exists, the
filehandle exists, too.

Example:

   # wait for readability of STDIN, then read a line and disable the watcher
   my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
      chomp (my $input = <STDIN>);
      warn "read: $input\n";
      undef $w;
   });

=head2 TIME WATCHERS

You can create a time watcher by calling the C<< AnyEvent->timer >>
method with the following mandatory arguments:

C<after> after how many seconds (fractions are supported) should the timer
activate. C<cb> the callback to invoke.

The timer callback will be invoked at most once: if you want a repeating
timer you have to create a new watcher (this is a limitation by both Tk
and Glib).

Example:

   # fire an event after 7.7 seconds
   my $w = AnyEvent->timer (after => 7.7, cb => sub {
      warn "timeout\n";
   });

   # to cancel the timer:
   undef $w

=head2 CONDITION WATCHERS

Condition watchers can be created by calling the C<< AnyEvent->condvar >>
method without any arguments.

A condition watcher watches for a condition - precisely that the C<<
->broadcast >> method has been called.

The watcher has only two methods:

=over 4

=item $cv->wait

Wait (blocking if necessary) until the C<< ->broadcast >> method has been
called on c<$cv>, while servicing other watchers normally.

Not all event models support a blocking wait - some die in that case, so
if you are using this from a module, never require a blocking wait, but
let the caller decide wether the call will block or not (for example,
by coupling condition variables with some kind of request results and
supporting callbacks so the caller knows that getting the result will not
block, while still suppporting blockign waits if the caller so desires).

You can only wait once on a condition - additional calls will return
immediately.

=item $cv->broadcast

Flag the condition as ready - a running C<< ->wait >> and all further
calls to C<wait> will return after this method has been called. If nobody
is waiting the broadcast will be remembered..

Example:

   # wait till the result is ready
   my $result_ready = AnyEvent->condvar;

   # do something such as adding a timer
   # or socket watcher the calls $result_ready->broadcast
   # when the "result" is ready.

   $result_ready->wait;

=back

=head2 SIGNAL WATCHERS

You can listen for signals using a signal watcher, C<signal> is the signal
I<name> without any C<SIG> prefix.

These watchers might use C<%SIG>, so programs overwriting those signals
directly will likely not work correctly.

Example: exit on SIGINT

   my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });

=head1 GLOBALS

=over 4

=item $AnyEvent::MODEL

Contains C<undef> until the first watcher is being created. Then it
contains the event model that is being used, which is the name of the
Perl class implementing the model. This class is usually one of the
C<AnyEvent::Impl:xxx> modules, but can be any other class in the case
AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).

The known classes so far are:

   AnyEvent::Impl::Coro      based on Coro::Event, best choise.
   AnyEvent::Impl::Event     based on Event, also best choice :)
   AnyEvent::Impl::Glib      based on Glib, second-best choice.
   AnyEvent::Impl::Tk        based on Tk, very bad choice.
   AnyEvent::Impl::Perl      pure-perl implementation, inefficient.

=item AnyEvent::detect

Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model if
necessary. You should only call this function right before you would have
created an AnyEvent watcher anyway, that is, very late at runtime.

=back

=head1 WHAT TO DO IN A MODULE

As a module author, you should "use AnyEvent" and call AnyEvent methods
freely, but you should not load a specific event module or rely on it.

Be careful when you create watchers in the module body - Anyevent will
decide which event module to use as soon as the first method is called, so
by calling AnyEvent in your module body you force the user of your module
to load the event module first.

=head1 WHAT TO DO IN THE MAIN PROGRAM

There will always be a single main program - the only place that should
dictate which event model to use.

If it doesn't care, it can just "use AnyEvent" and use it itself, or not
do anything special and let AnyEvent decide which implementation to chose.

If the main program relies on a specific event model (for example, in Gtk2
programs you have to rely on either Glib or Glib::Event), you should load
it before loading AnyEvent or any module that uses it, generally, as early
as possible. The reason is that modules might create watchers when they
are loaded, and AnyEvent will decide on the event model to use as soon as
it creates watchers, and it might chose the wrong one unless you load the
correct one yourself.

You can chose to use a rather inefficient pure-perl implementation by
loading the C<AnyEvent::Impl::Perl> module, but letting AnyEvent chose is
generally better.

=cut

package AnyEvent;

no warnings;
use strict;
use Carp;

our $VERSION = '2.5';
our $MODEL;

our $AUTOLOAD;
our @ISA;

our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;

our @REGISTRY;

my @models = (
   [Coro::Event::          => AnyEvent::Impl::Coro::],
   [Event::                => AnyEvent::Impl::Event::],
   [Glib::                 => AnyEvent::Impl::Glib::],
   [Tk::                   => AnyEvent::Impl::Tk::],
   [AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
);

our %method = map +($_ => 1), qw(io timer condvar broadcast wait signal one_event DESTROY);

sub detect() {
   unless ($MODEL) {
      no strict 'refs';

      # check for already loaded models
      for (@REGISTRY, @models) {
         my ($package, $model) = @$_;
         if (${"$package\::VERSION"} > 0) {
            if (eval "require $model") {
               $MODEL = $model;
               warn "AnyEvent: found model '$model', using it.\n" if $verbose > 1;
               last;
            }
         }
      }

      unless ($MODEL) {
         # try to load a model

         for (@REGISTRY, @models) {
            my ($package, $model) = @$_;
            if (eval "require $model") {
               $MODEL = $model;
               warn "AnyEvent: autoprobed and loaded model '$model', using it.\n" if $verbose > 1;
               last;
            }
         }

         $MODEL
           or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: Event (or Coro+Event), Glib or Tk.";
      }

      unshift @ISA, $MODEL;
      push @{"$MODEL\::ISA"}, "AnyEvent::Base";
   }

   $MODEL
}

sub AUTOLOAD {
   (my $func = $AUTOLOAD) =~ s/.*://;

   $method{$func}
      or croak "$func: not a valid method for AnyEvent objects";

   detect unless $MODEL;

   my $class = shift;
   $class->$func (@_);
}

package AnyEvent::Base;

# default implementation for signal

our %SIG_CB;

sub signal {
   my (undef, %arg) = @_;

   my $signal = uc $arg{signal}
      or Carp::croak "required option 'signal' is missing";

   my $w = bless [$signal, $arg{cb}], "AnyEvent::Base::Signal";

   $SIG_CB{$signal}{$arg{cb}} = $arg{cb};
   $SIG{$signal} ||= sub {
      $_->() for values %{ $SIG_CB{$signal} };
   };

   $w
}

sub AnyEvent::Base::Signal::DESTROY {
   my ($signal, $cb) = @{$_[0]};

   delete $SIG_CB{$signal}{$cb};

   $SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };
}

=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE

If you need to support another event library which isn't directly
supported by AnyEvent, you can supply your own interface to it by
pushing, before the first watcher gets created, the package name of
the event module and the package name of the interface to use onto
C<@AnyEvent::REGISTRY>. You can do that before and even without loading
AnyEvent.

Example:

   push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];

This tells AnyEvent to (literally) use the C<urxvt::anyevent::>
package/class when it finds the C<urxvt> package/module is loaded. When
AnyEvent is loaded and asked to find a suitable event model, it will
first check for the presence of urxvt.

The class should provide implementations for all watcher types (see
L<AnyEvent::Impl::Event> (source code), L<AnyEvent::Impl::Glib>
(Source code) and so on for actual examples, use C<perldoc -m
AnyEvent::Impl::Glib> to see the sources).

The above isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt)
uses the above line as-is. An interface isn't included in AnyEvent
because it doesn't make sense outside the embedded interpreter inside
I<rxvt-unicode>, and it is updated and maintained as part of the
I<rxvt-unicode> distribution.

I<rxvt-unicode> also cheats a bit by not providing blocking access to
condition variables: code blocking while waiting for a condition will
C<die>. This still works with most modules/usages, and blocking calls must
not be in an interactive appliation, so it makes sense.

=head1 ENVIRONMENT VARIABLES

The following environment variables are used by this module:

C<PERL_ANYEVENT_VERBOSE> when set to C<2> or higher, reports which event
model gets used.

=head1 EXAMPLE

The following program uses an io watcher to read data from stdin, a timer
to display a message once per second, and a condvar to exit the program
when the user enters quit:

   use AnyEvent;

   my $cv = AnyEvent->condvar;

   my $io_watcher = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
      warn "io event <$_[0]>\n";   # will always output <r>
      chomp (my $input = <STDIN>); # read a line
      warn "read: $input\n";       # output what has been read
      $cv->broadcast if $input =~ /^q/i; # quit program if /^q/i
   });

   my $time_watcher; # can only be used once

   sub new_timer {
      $timer = AnyEvent->timer (after => 1, cb => sub {
         warn "timeout\n"; # print 'timeout' about every second
         &new_timer; # and restart the time
      });
   }

   new_timer; # create first timer

   $cv->wait; # wait until user enters /^q/i

=head1 REAL-WORLD EXAMPLE

Consider the L<Net::FCP> module. It features (among others) the following
API calls, which are to freenet what HTTP GET requests are to http:

   my $data = $fcp->client_get ($url); # blocks

   my $transaction = $fcp->txn_client_get ($url); # does not block
   $transaction->cb ( sub { ... } ); # set optional result callback
   my $data = $transaction->result; # possibly blocks

The C<client_get> method works like C<LWP::Simple::get>: it requests the
given URL and waits till the data has arrived. It is defined to be:

   sub client_get { $_[0]->txn_client_get ($_[1])->result }

And in fact is automatically generated. This is the blocking API of
L<Net::FCP>, and it works as simple as in any other, similar, module.

More complicated is C<txn_client_get>: It only creates a transaction
(completion, result, ...) object and initiates the transaction.

   my $txn = bless { }, Net::FCP::Txn::;

It also creates a condition variable that is used to signal the completion
of the request:

   $txn->{finished} = AnyAvent->condvar;

It then creates a socket in non-blocking mode.

   socket $txn->{fh}, ...;
   fcntl $txn->{fh}, F_SETFL, O_NONBLOCK;
   connect $txn->{fh}, ...
      and !$!{EWOULDBLOCK}
      and !$!{EINPROGRESS}
      and Carp::croak "unable to connect: $!\n";

Then it creates a write-watcher which gets called whenever an error occurs
or the connection succeeds:

   $txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'w', cb => sub { $txn->fh_ready_w });

And returns this transaction object. The C<fh_ready_w> callback gets
called as soon as the event loop detects that the socket is ready for
writing.

The C<fh_ready_w> method makes the socket blocking again, writes the
request data and replaces the watcher by a read watcher (waiting for reply
data). The actual code is more complicated, but that doesn't matter for
this example:

   fcntl $txn->{fh}, F_SETFL, 0;
   syswrite $txn->{fh}, $txn->{request}
      or die "connection or write error";
   $txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });

Again, C<fh_ready_r> waits till all data has arrived, and then stores the
result and signals any possible waiters that the request ahs finished:

   sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};

   if (end-of-file or data complete) {
     $txn->{result} = $txn->{buf};
     $txn->{finished}->broadcast;
     $txb->{cb}->($txn) of $txn->{cb}; # also call callback
   }

The C<result> method, finally, just waits for the finished signal (if the
request was already finished, it doesn't wait, of course, and returns the
data:

   $txn->{finished}->wait;
   return $txn->{result};

The actual code goes further and collects all errors (C<die>s, exceptions)
that occured during request processing. The C<result> method detects
wether an exception as thrown (it is stored inside the $txn object)
and just throws the exception, which means connection errors and other
problems get reported tot he code that tries to use the result, not in a
random callback.

All of this enables the following usage styles:

1. Blocking:

   my $data = $fcp->client_get ($url);

2. Blocking, but parallelizing:

   my @datas = map $_->result,
                  map $fcp->txn_client_get ($_),
                     @urls;

Both blocking examples work without the module user having to know
anything about events.

3a. Event-based in a main program, using any support Event module:

   use Event;

   $fcp->txn_client_get ($url)->cb (sub {
      my $txn = shift;
      my $data = $txn->result;
      ...
   });

   Event::loop;

3b. The module user could use AnyEvent, too:

   use AnyEvent;

   my $quit = AnyEvent->condvar;

   $fcp->txn_client_get ($url)->cb (sub {
      ...
      $quit->broadcast;
   });

   $quit->wait;

=head1 SEE ALSO

Event modules: L<Coro::Event>, L<Coro>, L<Event>, L<Glib::Event>, L<Glib>.

Implementations: L<AnyEvent::Impl::Coro>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>.

Nontrivial usage example: L<Net::FCP>.

=head1

=cut

1

Revision:	1.19
Committed:	Sun Dec 10 23:59:15 2006 UTC (17 years, 6 months ago) by root
Branch:	MAIN
Changes since 1.18:	+71 -14 lines
Log Message:	implement sigwatcher
#	User	Rev	Content
1	root	1.1	=head1 NAME
2
3	root	1.2	AnyEvent - provide framework for multiple event loops
4
5	root	1.14	Event, Coro, Glib, Tk, Perl - various supported event loops
6	root	1.1
7			=head1 SYNOPSIS
8
9	root	1.7	use AnyEvent;
10	root	1.2
11	root	1.14	my $w = AnyEvent->io (fh => $fh, poll => "r\|w", cb => sub {
12	root	1.2	...
13			});
14	root	1.5
15			my $w = AnyEvent->timer (after => $seconds, cb => sub {
16	root	1.2	...
17			});
18
19	root	1.14	my $w = AnyEvent->condvar; # stores wether a condition was flagged
20			$w->wait; # enters "main loop" till $condvar gets ->broadcast
21	root	1.5	$w->broadcast; # wake up current and all future wait's
22
23	root	1.1	=head1 DESCRIPTION
24
25	root	1.2	L<AnyEvent> provides an identical interface to multiple event loops. This
26	root	1.13	allows module authors to utilise an event loop without forcing module
27	root	1.2	users to use the same event loop (as only a single event loop can coexist
28			peacefully at any one time).
29
30			The interface itself is vaguely similar but not identical to the Event
31			module.
32
33			On the first call of any method, the module tries to detect the currently
34			loaded event loop by probing wether any of the following modules is
35			loaded: L<Coro::Event>, L<Event>, L<Glib>, L<Tk>. The first one found is
36			used. If none is found, the module tries to load these modules in the
37			order given. The first one that could be successfully loaded will be
38	root	1.14	used. If still none could be found, AnyEvent will fall back to a pure-perl
39			event loop, which is also not very efficient.
40
41			Because AnyEvent first checks for modules that are already loaded, loading
42			an Event model explicitly before first using AnyEvent will likely make
43			that model the default. For example:
44
45			use Tk;
46			use AnyEvent;
47
48			# .. AnyEvent will likely default to Tk
49
50			The pure-perl implementation of AnyEvent is called
51			C<AnyEvent::Impl::Perl>. Like other event modules you can load it
52			explicitly.
53
54			=head1 WATCHERS
55
56			AnyEvent has the central concept of a I<watcher>, which is an object that
57			stores relevant data for each kind of event you are waiting for, such as
58			the callback to call, the filehandle to watch, etc.
59
60			These watchers are normal Perl objects with normal Perl lifetime. After
61			creating a watcher it will immediately "watch" for events and invoke
62			the callback. To disable the watcher you have to destroy it (e.g. by
63			setting the variable that stores it to C<undef> or otherwise deleting all
64			references to it).
65
66			All watchers are created by calling a method on the C<AnyEvent> class.
67
68			=head2 IO WATCHERS
69
70			You can create I/O watcher by calling the C<< AnyEvent->io >> method with
71			the following mandatory arguments:
72
73			C<fh> the Perl I<filehandle> (not filedescriptor) to watch for
74			events. C<poll> must be a string that is either C<r> or C<w>, that creates
75			a watcher waiting for "r"eadable or "w"ritable events. C<cb> teh callback
76			to invoke everytime the filehandle becomes ready.
77
78			Only one io watcher per C<fh> and C<poll> combination is allowed (i.e. on
79			a socket you can have one r + one w, not any more (limitation comes from
80			Tk - if you are sure you are not using Tk this limitation is gone).
81
82			Filehandles will be kept alive, so as long as the watcher exists, the
83			filehandle exists, too.
84
85			Example:
86
87			# wait for readability of STDIN, then read a line and disable the watcher
88			my $w; $w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
89			chomp (my $input = <STDIN>);
90			warn "read: $input\n";
91			undef $w;
92			});
93
94	root	1.19	=head2 TIME WATCHERS
95	root	1.14
96	root	1.19	You can create a time watcher by calling the C<< AnyEvent->timer >>
97	root	1.14	method with the following mandatory arguments:
98
99			C<after> after how many seconds (fractions are supported) should the timer
100			activate. C<cb> the callback to invoke.
101
102			The timer callback will be invoked at most once: if you want a repeating
103			timer you have to create a new watcher (this is a limitation by both Tk
104			and Glib).
105
106			Example:
107
108			# fire an event after 7.7 seconds
109			my $w = AnyEvent->timer (after => 7.7, cb => sub {
110			warn "timeout\n";
111			});
112
113			# to cancel the timer:
114			undef $w
115
116			=head2 CONDITION WATCHERS
117
118			Condition watchers can be created by calling the C<< AnyEvent->condvar >>
119			method without any arguments.
120
121			A condition watcher watches for a condition - precisely that the C<<
122			->broadcast >> method has been called.
123
124			The watcher has only two methods:
125	root	1.2
126	root	1.1	=over 4
127
128	root	1.14	=item $cv->wait
129
130			Wait (blocking if necessary) until the C<< ->broadcast >> method has been
131			called on c<$cv>, while servicing other watchers normally.
132
133			Not all event models support a blocking wait - some die in that case, so
134			if you are using this from a module, never require a blocking wait, but
135			let the caller decide wether the call will block or not (for example,
136			by coupling condition variables with some kind of request results and
137			supporting callbacks so the caller knows that getting the result will not
138			block, while still suppporting blockign waits if the caller so desires).
139
140			You can only wait once on a condition - additional calls will return
141			immediately.
142
143			=item $cv->broadcast
144
145			Flag the condition as ready - a running C<< ->wait >> and all further
146			calls to C<wait> will return after this method has been called. If nobody
147			is waiting the broadcast will be remembered..
148
149			Example:
150
151			# wait till the result is ready
152			my $result_ready = AnyEvent->condvar;
153
154			# do something such as adding a timer
155			# or socket watcher the calls $result_ready->broadcast
156			# when the "result" is ready.
157
158			$result_ready->wait;
159
160			=back
161
162	root	1.19	=head2 SIGNAL WATCHERS
163
164			You can listen for signals using a signal watcher, C<signal> is the signal
165			I<name> without any C<SIG> prefix.
166
167			These watchers might use C<%SIG>, so programs overwriting those signals
168			directly will likely not work correctly.
169
170			Example: exit on SIGINT
171
172			my $w = AnyEvent->signal (signal => "INT", cb => sub { exit 1 });
173
174	root	1.16	=head1 GLOBALS
175
176			=over 4
177
178			=item $AnyEvent::MODEL
179
180			Contains C<undef> until the first watcher is being created. Then it
181			contains the event model that is being used, which is the name of the
182			Perl class implementing the model. This class is usually one of the
183			C<AnyEvent::Impl:xxx> modules, but can be any other class in the case
184			AnyEvent has been extended at runtime (e.g. in I<rxvt-unicode>).
185
186			The known classes so far are:
187
188			AnyEvent::Impl::Coro based on Coro::Event, best choise.
189			AnyEvent::Impl::Event based on Event, also best choice :)
190			AnyEvent::Impl::Glib based on Glib, second-best choice.
191			AnyEvent::Impl::Tk based on Tk, very bad choice.
192			AnyEvent::Impl::Perl pure-perl implementation, inefficient.
193
194	root	1.19	=item AnyEvent::detect
195
196			Returns C<$AnyEvent::MODEL>, forcing autodetection of the event model if
197			necessary. You should only call this function right before you would have
198			created an AnyEvent watcher anyway, that is, very late at runtime.
199
200	root	1.16	=back
201
202	root	1.14	=head1 WHAT TO DO IN A MODULE
203
204			As a module author, you should "use AnyEvent" and call AnyEvent methods
205			freely, but you should not load a specific event module or rely on it.
206
207			Be careful when you create watchers in the module body - Anyevent will
208			decide which event module to use as soon as the first method is called, so
209			by calling AnyEvent in your module body you force the user of your module
210			to load the event module first.
211
212			=head1 WHAT TO DO IN THE MAIN PROGRAM
213
214			There will always be a single main program - the only place that should
215			dictate which event model to use.
216
217			If it doesn't care, it can just "use AnyEvent" and use it itself, or not
218			do anything special and let AnyEvent decide which implementation to chose.
219
220			If the main program relies on a specific event model (for example, in Gtk2
221			programs you have to rely on either Glib or Glib::Event), you should load
222			it before loading AnyEvent or any module that uses it, generally, as early
223			as possible. The reason is that modules might create watchers when they
224			are loaded, and AnyEvent will decide on the event model to use as soon as
225			it creates watchers, and it might chose the wrong one unless you load the
226			correct one yourself.
227
228			You can chose to use a rather inefficient pure-perl implementation by
229			loading the C<AnyEvent::Impl::Perl> module, but letting AnyEvent chose is
230			generally better.
231
232	root	1.1	=cut
233
234			package AnyEvent;
235
236	root	1.2	no warnings;
237	root	1.19	use strict;
238	root	1.1	use Carp;
239
240	root	1.19	our $VERSION = '2.5';
241	root	1.2	our $MODEL;
242	root	1.1
243	root	1.2	our $AUTOLOAD;
244			our @ISA;
245	root	1.1
246	root	1.7	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
247
248	root	1.8	our @REGISTRY;
249
250	root	1.1	my @models = (
251	root	1.18	[Coro::Event:: => AnyEvent::Impl::Coro::],
252			[Event:: => AnyEvent::Impl::Event::],
253			[Glib:: => AnyEvent::Impl::Glib::],
254			[Tk:: => AnyEvent::Impl::Tk::],
255			[AnyEvent::Impl::Perl:: => AnyEvent::Impl::Perl::],
256	root	1.1	);
257
258	root	1.19	our %method = map +($_ => 1), qw(io timer condvar broadcast wait signal one_event DESTROY);
259	root	1.3
260	root	1.19	sub detect() {
261			unless ($MODEL) {
262			no strict 'refs';
263	root	1.1
264	root	1.2	# check for already loaded models
265	root	1.8	for (@REGISTRY, @models) {
266			my ($package, $model) = @$_;
267	root	1.7	if (${"$package\::VERSION"} > 0) {
268	root	1.8	if (eval "require $model") {
269			$MODEL = $model;
270			warn "AnyEvent: found model '$model', using it.\n" if $verbose > 1;
271			last;
272			}
273	root	1.2	}
274	root	1.1	}
275
276	root	1.2	unless ($MODEL) {
277			# try to load a model
278
279	root	1.8	for (@REGISTRY, @models) {
280			my ($package, $model) = @$_;
281			if (eval "require $model") {
282			$MODEL = $model;
283			warn "AnyEvent: autoprobed and loaded model '$model', using it.\n" if $verbose > 1;
284			last;
285			}
286	root	1.2	}
287
288			$MODEL
289	root	1.19	or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: Event (or Coro+Event), Glib or Tk.";
290	root	1.1	}
291	root	1.19
292			unshift @ISA, $MODEL;
293			push @{"$MODEL\::ISA"}, "AnyEvent::Base";
294	root	1.1	}
295
296	root	1.19	$MODEL
297			}
298
299			sub AUTOLOAD {
300			(my $func = $AUTOLOAD) =~ s/.*://;
301
302			$method{$func}
303			or croak "$func: not a valid method for AnyEvent objects";
304
305			detect unless $MODEL;
306	root	1.2
307			my $class = shift;
308	root	1.18	$class->$func (@_);
309	root	1.1	}
310
311	root	1.19	package AnyEvent::Base;
312
313			# default implementation for signal
314
315			our %SIG_CB;
316
317			sub signal {
318			my (undef, %arg) = @_;
319
320			my $signal = uc $arg{signal}
321			or Carp::croak "required option 'signal' is missing";
322
323			my $w = bless [$signal, $arg{cb}], "AnyEvent::Base::Signal";
324
325			$SIG_CB{$signal}{$arg{cb}} = $arg{cb};
326			$SIG{$signal} \|\|= sub {
327			$_->() for values %{ $SIG_CB{$signal} };
328			};
329
330			$w
331			}
332
333			sub AnyEvent::Base::Signal::DESTROY {
334			my ($signal, $cb) = @{$_[0]};
335
336			delete $SIG_CB{$signal}{$cb};
337
338			$SIG{$signal} = 'DEFAULT' unless keys %{ $SIG_CB{$signal} };
339			}
340
341	root	1.8	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
342
343			If you need to support another event library which isn't directly
344			supported by AnyEvent, you can supply your own interface to it by
345	root	1.11	pushing, before the first watcher gets created, the package name of
346	root	1.8	the event module and the package name of the interface to use onto
347			C<@AnyEvent::REGISTRY>. You can do that before and even without loading
348			AnyEvent.
349
350			Example:
351
352			push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
353
354	root	1.12	This tells AnyEvent to (literally) use the C<urxvt::anyevent::>
355			package/class when it finds the C<urxvt> package/module is loaded. When
356			AnyEvent is loaded and asked to find a suitable event model, it will
357			first check for the presence of urxvt.
358
359	root	1.19	The class should provide implementations for all watcher types (see
360	root	1.12	L<AnyEvent::Impl::Event> (source code), L<AnyEvent::Impl::Glib>
361			(Source code) and so on for actual examples, use C<perldoc -m
362			AnyEvent::Impl::Glib> to see the sources).
363	root	1.8
364	root	1.12	The above isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt)
365			uses the above line as-is. An interface isn't included in AnyEvent
366	root	1.8	because it doesn't make sense outside the embedded interpreter inside
367			I<rxvt-unicode>, and it is updated and maintained as part of the
368			I<rxvt-unicode> distribution.
369
370	root	1.12	I<rxvt-unicode> also cheats a bit by not providing blocking access to
371			condition variables: code blocking while waiting for a condition will
372			C<die>. This still works with most modules/usages, and blocking calls must
373			not be in an interactive appliation, so it makes sense.
374
375	root	1.7	=head1 ENVIRONMENT VARIABLES
376
377			The following environment variables are used by this module:
378
379			C<PERL_ANYEVENT_VERBOSE> when set to C<2> or higher, reports which event
380			model gets used.
381
382	root	1.2	=head1 EXAMPLE
383
384			The following program uses an io watcher to read data from stdin, a timer
385			to display a message once per second, and a condvar to exit the program
386			when the user enters quit:
387
388			use AnyEvent;
389
390			my $cv = AnyEvent->condvar;
391
392			my $io_watcher = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
393			warn "io event <$_[0]>\n"; # will always output <r>
394			chomp (my $input = <STDIN>); # read a line
395			warn "read: $input\n"; # output what has been read
396			$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i
397			});
398
399			my $time_watcher; # can only be used once
400
401			sub new_timer {
402			$timer = AnyEvent->timer (after => 1, cb => sub {
403			warn "timeout\n"; # print 'timeout' about every second
404			&new_timer; # and restart the time
405			});
406			}
407
408			new_timer; # create first timer
409
410			$cv->wait; # wait until user enters /^q/i
411
412	root	1.5	=head1 REAL-WORLD EXAMPLE
413
414			Consider the L<Net::FCP> module. It features (among others) the following
415			API calls, which are to freenet what HTTP GET requests are to http:
416
417			my $data = $fcp->client_get ($url); # blocks
418
419			my $transaction = $fcp->txn_client_get ($url); # does not block
420			$transaction->cb ( sub { ... } ); # set optional result callback
421			my $data = $transaction->result; # possibly blocks
422
423			The C<client_get> method works like C<LWP::Simple::get>: it requests the
424			given URL and waits till the data has arrived. It is defined to be:
425
426			sub client_get { $_[0]->txn_client_get ($_[1])->result }
427
428			And in fact is automatically generated. This is the blocking API of
429			L<Net::FCP>, and it works as simple as in any other, similar, module.
430
431			More complicated is C<txn_client_get>: It only creates a transaction
432			(completion, result, ...) object and initiates the transaction.
433
434			my $txn = bless { }, Net::FCP::Txn::;
435
436			It also creates a condition variable that is used to signal the completion
437			of the request:
438
439			$txn->{finished} = AnyAvent->condvar;
440
441			It then creates a socket in non-blocking mode.
442
443			socket $txn->{fh}, ...;
444			fcntl $txn->{fh}, F_SETFL, O_NONBLOCK;
445			connect $txn->{fh}, ...
446			and !$!{EWOULDBLOCK}
447			and !$!{EINPROGRESS}
448			and Carp::croak "unable to connect: $!\n";
449
450	root	1.6	Then it creates a write-watcher which gets called whenever an error occurs
451	root	1.5	or the connection succeeds:
452
453			$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'w', cb => sub { $txn->fh_ready_w });
454
455			And returns this transaction object. The C<fh_ready_w> callback gets
456			called as soon as the event loop detects that the socket is ready for
457			writing.
458
459			The C<fh_ready_w> method makes the socket blocking again, writes the
460			request data and replaces the watcher by a read watcher (waiting for reply
461			data). The actual code is more complicated, but that doesn't matter for
462			this example:
463
464			fcntl $txn->{fh}, F_SETFL, 0;
465			syswrite $txn->{fh}, $txn->{request}
466			or die "connection or write error";
467			$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
468
469			Again, C<fh_ready_r> waits till all data has arrived, and then stores the
470			result and signals any possible waiters that the request ahs finished:
471
472			sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
473
474			if (end-of-file or data complete) {
475			$txn->{result} = $txn->{buf};
476			$txn->{finished}->broadcast;
477	root	1.6	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
478	root	1.5	}
479
480			The C<result> method, finally, just waits for the finished signal (if the
481			request was already finished, it doesn't wait, of course, and returns the
482			data:
483
484			$txn->{finished}->wait;
485	root	1.6	return $txn->{result};
486	root	1.5
487			The actual code goes further and collects all errors (C<die>s, exceptions)
488			that occured during request processing. The C<result> method detects
489			wether an exception as thrown (it is stored inside the $txn object)
490			and just throws the exception, which means connection errors and other
491			problems get reported tot he code that tries to use the result, not in a
492			random callback.
493
494			All of this enables the following usage styles:
495
496			1. Blocking:
497
498			my $data = $fcp->client_get ($url);
499
500			2. Blocking, but parallelizing:
501
502			my @datas = map $_->result,
503			map $fcp->txn_client_get ($_),
504			@urls;
505
506			Both blocking examples work without the module user having to know
507			anything about events.
508
509			3a. Event-based in a main program, using any support Event module:
510
511			use Event;
512
513			$fcp->txn_client_get ($url)->cb (sub {
514			my $txn = shift;
515			my $data = $txn->result;
516			...
517			});
518
519			Event::loop;
520
521			3b. The module user could use AnyEvent, too:
522
523			use AnyEvent;
524
525			my $quit = AnyEvent->condvar;
526
527			$fcp->txn_client_get ($url)->cb (sub {
528			...
529			$quit->broadcast;
530			});
531
532			$quit->wait;
533
534	root	1.2	=head1 SEE ALSO
535
536	root	1.5	Event modules: L<Coro::Event>, L<Coro>, L<Event>, L<Glib::Event>, L<Glib>.
537
538			Implementations: L<AnyEvent::Impl::Coro>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>.
539
540			Nontrivial usage example: L<Net::FCP>.
541	root	1.2
542			=head1
543
544			=cut
545
546			1
547	root	1.1