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 *
#	Content
1	=head1 NAME
2
3	AnyEvent - provide framework for multiple event loops
4
5	Event, Coro, Glib, Tk - various supported event loops
6
7	=head1 SYNOPSIS
8
9	use AnyEvent;
10
11	my $w = AnyEvent->io (fh => ..., poll => "[rw]+", cb => sub {
12	my ($poll_got) = @_;
13	...
14	});
15
16	* 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
25	* AnyEvent will keep filehandles alive, so as long as the watcher exists,
26	the filehandle exists.
27
28	my $w = AnyEvent->timer (after => $seconds, cb => sub {
29	...
30	});
31
32	* io and time watchers get canceled whenever $w is destroyed, so keep a copy
33
34	* timers can only be used once and must be recreated for repeated
35	operation (limitation by Glib and Tk).
36
37	my $w = AnyEvent->condvar; # kind of main loop replacement
38	$w->wait; # enters main loop till $condvar gets ->broadcast
39	$w->broadcast; # wake up current and all future wait's
40
41	* condvars are used to give blocking behaviour when neccessary. Create
42	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
46	=head1 DESCRIPTION
47
48	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	=over 4
64
65	=cut
66
67	package AnyEvent;
68
69	no warnings;
70	use strict 'vars';
71	use Carp;
72
73	our $VERSION = '0.4';
74	our $MODEL;
75
76	our $AUTOLOAD;
77	our @ISA;
78
79	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
80
81	my @models = (
82	[Coro => Coro::Event::],
83	[Event => Event::],
84	[Glib => Glib::],
85	[Tk => Tk::],
86	);
87
88	our %method = map +($_ => 1), qw(io timer condvar broadcast wait cancel DESTROY);
89
90	sub AUTOLOAD {
91	$AUTOLOAD =~ s/.*://;
92
93	$method{$AUTOLOAD}
94	or croak "$AUTOLOAD: not a valid method for AnyEvent objects";
95
96	unless ($MODEL) {
97	# check for already loaded models
98	for (@models) {
99	my ($model, $package) = @$_;
100	if (${"$package\::VERSION"} > 0) {
101	eval "require AnyEvent::Impl::$model";
102	warn "AnyEvent: found model '$model', using it.\n" if $MODEL && $verbose > 1;
103	last if $MODEL;
104	}
105	}
106
107	unless ($MODEL) {
108	# try to load a model
109
110	for (@models) {
111	my ($model, $package) = @$_;
112	eval "require AnyEvent::Impl::$model";
113	warn "AnyEvent: autprobed and loaded model '$model', using it.\n" if $MODEL && $verbose > 1;
114	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	}
120	}
121
122	@ISA = $MODEL;
123
124	my $class = shift;
125	$class->$AUTOLOAD (@_);
126	}
127
128	=back
129
130	=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	=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	=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	Then it creates a write-watcher which gets called whenever an error occurs
206	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	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
233	}
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	return $txn->{result};
241
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	=head1 SEE ALSO
290
291	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
297	=head1
298
299	=cut
300
301	1
302