AnyEvent/lib/AnyEvent.pm

=head1 NAME

AnyEvent - provide framework for multiple event loops

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

=head1 SYNOPSIS

   use AnyEvent;

   my $w = AnyEvent->io (fh => ..., poll => "[rw]+", cb => sub {
      my ($poll_got) = @_;
      ...
   });

* only one io watcher per $fh and $poll type is allowed (i.e. on a socket
you can have one r + one w or one rw watcher, not any more (limitation by
Tk).

* the C<$poll_got> passed to the handler needs to be checked by looking
for single characters (e.g. with a regex), as it can contain more event
types than were requested (e.g. a 'w' watcher might generate 'rw' events,
limitation by Glib).

* AnyEvent will keep filehandles alive, so as long as the watcher exists,
the filehandle exists.

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

* io and time watchers get canceled whenever $w is destroyed, so keep a copy

* timers can only be used once and must be recreated for repeated
operation (limitation by Glib and Tk).

   my $w = AnyEvent->condvar; # kind of main loop replacement
   $w->wait; # enters main loop till $condvar gets ->broadcast
   $w->broadcast; # wake up current and all future wait's

* condvars are used to give blocking behaviour when neccessary. Create
a condvar for any "request" or "event" your module might create, C<<
->broadcast >> it when the event happens and provide a function that calls
C<< ->wait >> for it. See the examples below.

=head1 DESCRIPTION

L<AnyEvent> provides an identical interface to multiple event loops. This
allows module authors to utilizy 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, it will issue an error.

=over 4

=cut

package AnyEvent;

no warnings;
use strict 'vars';
use Carp;

our $VERSION = '0.4';
our $MODEL;

our $AUTOLOAD;
our @ISA;

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

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

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

sub AUTOLOAD {
   $AUTOLOAD =~ s/.*://;

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

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

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

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

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

   @ISA = $MODEL;

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

=back

=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:	1.7
Committed:	Fri Dec 30 01:28:31 2005 UTC (18 years, 6 months ago) by root
Branch:	MAIN
CVS Tags:	rel-0_4
Changes since 1.6:	+27 -10 lines
Log Message:	* empty log message *
#	User	Rev	Content
1	root	1.1	=head1 NAME
2
3	root	1.2	AnyEvent - provide framework for multiple event loops
4
5			Event, Coro, Glib, Tk - various supported event loops
6	root	1.1
7			=head1 SYNOPSIS
8
9	root	1.7	use AnyEvent;
10	root	1.2
11	root	1.5	my $w = AnyEvent->io (fh => ..., poll => "[rw]+", cb => sub {
12	root	1.2	my ($poll_got) = @_;
13			...
14			});
15	root	1.5
16	root	1.7	* only one io watcher per $fh and $poll type is allowed (i.e. on a socket
17			you can have one r + one w or one rw watcher, not any more (limitation by
18			Tk).
19
20			* the C<$poll_got> passed to the handler needs to be checked by looking
21			for single characters (e.g. with a regex), as it can contain more event
22			types than were requested (e.g. a 'w' watcher might generate 'rw' events,
23			limitation by Glib).
24	root	1.5
25	root	1.7	* AnyEvent will keep filehandles alive, so as long as the watcher exists,
26	root	1.5	the filehandle exists.
27
28			my $w = AnyEvent->timer (after => $seconds, cb => sub {
29	root	1.2	...
30			});
31
32	root	1.7	* io and time watchers get canceled whenever $w is destroyed, so keep a copy
33	root	1.5
34	root	1.7	* timers can only be used once and must be recreated for repeated
35			operation (limitation by Glib and Tk).
36	root	1.2
37			my $w = AnyEvent->condvar; # kind of main loop replacement
38	root	1.5	$w->wait; # enters main loop till $condvar gets ->broadcast
39			$w->broadcast; # wake up current and all future wait's
40
41	root	1.7	* condvars are used to give blocking behaviour when neccessary. Create
42	root	1.5	a condvar for any "request" or "event" your module might create, C<<
43			->broadcast >> it when the event happens and provide a function that calls
44			C<< ->wait >> for it. See the examples below.
45	root	1.2
46	root	1.1	=head1 DESCRIPTION
47
48	root	1.2	L<AnyEvent> provides an identical interface to multiple event loops. This
49			allows module authors to utilizy an event loop without forcing module
50			users to use the same event loop (as only a single event loop can coexist
51			peacefully at any one time).
52
53			The interface itself is vaguely similar but not identical to the Event
54			module.
55
56			On the first call of any method, the module tries to detect the currently
57			loaded event loop by probing wether any of the following modules is
58			loaded: L<Coro::Event>, L<Event>, L<Glib>, L<Tk>. The first one found is
59			used. If none is found, the module tries to load these modules in the
60			order given. The first one that could be successfully loaded will be
61			used. If still none could be found, it will issue an error.
62
63	root	1.1	=over 4
64
65			=cut
66
67			package AnyEvent;
68
69	root	1.2	no warnings;
70			use strict 'vars';
71	root	1.1	use Carp;
72
73	root	1.7	our $VERSION = '0.4';
74	root	1.2	our $MODEL;
75	root	1.1
76	root	1.2	our $AUTOLOAD;
77			our @ISA;
78	root	1.1
79	root	1.7	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
80
81	root	1.1	my @models = (
82			[Coro => Coro::Event::],
83			[Event => Event::],
84			[Glib => Glib::],
85			[Tk => Tk::],
86			);
87
88	root	1.3	our %method = map +($_ => 1), qw(io timer condvar broadcast wait cancel DESTROY);
89
90	root	1.1	sub AUTOLOAD {
91			$AUTOLOAD =~ s/.*://;
92
93	root	1.3	$method{$AUTOLOAD}
94			or croak "$AUTOLOAD: not a valid method for AnyEvent objects";
95
96	root	1.2	unless ($MODEL) {
97			# check for already loaded models
98			for (@models) {
99			my ($model, $package) = @$_;
100	root	1.7	if (${"$package\::VERSION"} > 0) {
101	root	1.4	eval "require AnyEvent::Impl::$model";
102	root	1.7	warn "AnyEvent: found model '$model', using it.\n" if $MODEL && $verbose > 1;
103	root	1.2	last if $MODEL;
104			}
105	root	1.1	}
106
107	root	1.2	unless ($MODEL) {
108			# try to load a model
109
110			for (@models) {
111			my ($model, $package) = @$_;
112	root	1.4	eval "require AnyEvent::Impl::$model";
113	root	1.7	warn "AnyEvent: autprobed and loaded model '$model', using it.\n" if $MODEL && $verbose > 1;
114	root	1.2	last if $MODEL;
115			}
116
117			$MODEL
118			or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: Coro, Event, Glib or Tk.";
119	root	1.1	}
120			}
121
122	root	1.2	@ISA = $MODEL;
123
124			my $class = shift;
125			$class->$AUTOLOAD (@_);
126	root	1.1	}
127
128	root	1.2	=back
129
130	root	1.7	=head1 ENVIRONMENT VARIABLES
131
132			The following environment variables are used by this module:
133
134			C<PERL_ANYEVENT_VERBOSE> when set to C<2> or higher, reports which event
135			model gets used.
136
137	root	1.2	=head1 EXAMPLE
138
139			The following program uses an io watcher to read data from stdin, a timer
140			to display a message once per second, and a condvar to exit the program
141			when the user enters quit:
142
143			use AnyEvent;
144
145			my $cv = AnyEvent->condvar;
146
147			my $io_watcher = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
148			warn "io event <$_[0]>\n"; # will always output <r>
149			chomp (my $input = <STDIN>); # read a line
150			warn "read: $input\n"; # output what has been read
151			$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i
152			});
153
154			my $time_watcher; # can only be used once
155
156			sub new_timer {
157			$timer = AnyEvent->timer (after => 1, cb => sub {
158			warn "timeout\n"; # print 'timeout' about every second
159			&new_timer; # and restart the time
160			});
161			}
162
163			new_timer; # create first timer
164
165			$cv->wait; # wait until user enters /^q/i
166
167	root	1.5	=head1 REAL-WORLD EXAMPLE
168
169			Consider the L<Net::FCP> module. It features (among others) the following
170			API calls, which are to freenet what HTTP GET requests are to http:
171
172			my $data = $fcp->client_get ($url); # blocks
173
174			my $transaction = $fcp->txn_client_get ($url); # does not block
175			$transaction->cb ( sub { ... } ); # set optional result callback
176			my $data = $transaction->result; # possibly blocks
177
178			The C<client_get> method works like C<LWP::Simple::get>: it requests the
179			given URL and waits till the data has arrived. It is defined to be:
180
181			sub client_get { $_[0]->txn_client_get ($_[1])->result }
182
183			And in fact is automatically generated. This is the blocking API of
184			L<Net::FCP>, and it works as simple as in any other, similar, module.
185
186			More complicated is C<txn_client_get>: It only creates a transaction
187			(completion, result, ...) object and initiates the transaction.
188
189			my $txn = bless { }, Net::FCP::Txn::;
190
191			It also creates a condition variable that is used to signal the completion
192			of the request:
193
194			$txn->{finished} = AnyAvent->condvar;
195
196			It then creates a socket in non-blocking mode.
197
198			socket $txn->{fh}, ...;
199			fcntl $txn->{fh}, F_SETFL, O_NONBLOCK;
200			connect $txn->{fh}, ...
201			and !$!{EWOULDBLOCK}
202			and !$!{EINPROGRESS}
203			and Carp::croak "unable to connect: $!\n";
204
205	root	1.6	Then it creates a write-watcher which gets called whenever an error occurs
206	root	1.5	or the connection succeeds:
207
208			$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'w', cb => sub { $txn->fh_ready_w });
209
210			And returns this transaction object. The C<fh_ready_w> callback gets
211			called as soon as the event loop detects that the socket is ready for
212			writing.
213
214			The C<fh_ready_w> method makes the socket blocking again, writes the
215			request data and replaces the watcher by a read watcher (waiting for reply
216			data). The actual code is more complicated, but that doesn't matter for
217			this example:
218
219			fcntl $txn->{fh}, F_SETFL, 0;
220			syswrite $txn->{fh}, $txn->{request}
221			or die "connection or write error";
222			$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
223
224			Again, C<fh_ready_r> waits till all data has arrived, and then stores the
225			result and signals any possible waiters that the request ahs finished:
226
227			sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
228
229			if (end-of-file or data complete) {
230			$txn->{result} = $txn->{buf};
231			$txn->{finished}->broadcast;
232	root	1.6	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
233	root	1.5	}
234
235			The C<result> method, finally, just waits for the finished signal (if the
236			request was already finished, it doesn't wait, of course, and returns the
237			data:
238
239			$txn->{finished}->wait;
240	root	1.6	return $txn->{result};
241	root	1.5
242			The actual code goes further and collects all errors (C<die>s, exceptions)
243			that occured during request processing. The C<result> method detects
244			wether an exception as thrown (it is stored inside the $txn object)
245			and just throws the exception, which means connection errors and other
246			problems get reported tot he code that tries to use the result, not in a
247			random callback.
248
249			All of this enables the following usage styles:
250
251			1. Blocking:
252
253			my $data = $fcp->client_get ($url);
254
255			2. Blocking, but parallelizing:
256
257			my @datas = map $_->result,
258			map $fcp->txn_client_get ($_),
259			@urls;
260
261			Both blocking examples work without the module user having to know
262			anything about events.
263
264			3a. Event-based in a main program, using any support Event module:
265
266			use Event;
267
268			$fcp->txn_client_get ($url)->cb (sub {
269			my $txn = shift;
270			my $data = $txn->result;
271			...
272			});
273
274			Event::loop;
275
276			3b. The module user could use AnyEvent, too:
277
278			use AnyEvent;
279
280			my $quit = AnyEvent->condvar;
281
282			$fcp->txn_client_get ($url)->cb (sub {
283			...
284			$quit->broadcast;
285			});
286
287			$quit->wait;
288
289	root	1.2	=head1 SEE ALSO
290
291	root	1.5	Event modules: L<Coro::Event>, L<Coro>, L<Event>, L<Glib::Event>, L<Glib>.
292
293			Implementations: L<AnyEvent::Impl::Coro>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>.
294
295			Nontrivial usage example: L<Net::FCP>.
296	root	1.2
297			=head1
298
299			=cut
300
301			1
302	root	1.1