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 = '1.02';
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::],
);

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 ($MODEL) {
      # check for already loaded models
      for (@REGISTRY, @models) {
         my ($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: Coro, Event, Glib or Tk.";
      }
   }

   @ISA = $MODEL;

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

=back

=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 watch 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::> module
when it finds the C<urxvt> module is loaded. When AnyEvent is loaded and
requested to find a suitable event model, it will first check for the
urxvt module.

The above isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt) uses
the above line exactly. 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.

=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:	1.10
Committed:	Fri Jan 13 13:16:15 2006 UTC (18 years, 5 months ago) by root
Branch:	MAIN
CVS Tags:	rel-1_02
Changes since 1.9:	+1 -1 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	1.10	our $VERSION = '1.02';
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 = $ENV{PERL_ANYEVENT_VERBOSE}*1;
80
81	root	1.8	our @REGISTRY;
82
83	root	1.1	my @models = (
84	root	1.8	[Coro::Event:: => AnyEvent::Impl::Coro::],
85			[Event:: => AnyEvent::Impl::Event::],
86			[Glib:: => AnyEvent::Impl::Glib::],
87			[Tk:: => AnyEvent::Impl::Tk::],
88	root	1.1	);
89
90	root	1.3	our %method = map +($_ => 1), qw(io timer condvar broadcast wait cancel DESTROY);
91
92	root	1.1	sub AUTOLOAD {
93			$AUTOLOAD =~ s/.*://;
94
95	root	1.3	$method{$AUTOLOAD}
96			or croak "$AUTOLOAD: not a valid method for AnyEvent objects";
97
98	root	1.2	unless ($MODEL) {
99			# check for already loaded models
100	root	1.8	for (@REGISTRY, @models) {
101			my ($package, $model) = @$_;
102	root	1.7	if (${"$package\::VERSION"} > 0) {
103	root	1.8	if (eval "require $model") {
104			$MODEL = $model;
105			warn "AnyEvent: found model '$model', using it.\n" if $verbose > 1;
106			last;
107			}
108	root	1.2	}
109	root	1.1	}
110
111	root	1.2	unless ($MODEL) {
112			# try to load a model
113
114	root	1.8	for (@REGISTRY, @models) {
115			my ($package, $model) = @$_;
116			if (eval "require $model") {
117			$MODEL = $model;
118			warn "AnyEvent: autoprobed and loaded model '$model', using it.\n" if $verbose > 1;
119			last;
120			}
121	root	1.2	}
122
123			$MODEL
124			or die "No event module selected for AnyEvent and autodetect failed. Install any one of these modules: Coro, Event, Glib or Tk.";
125	root	1.1	}
126			}
127
128	root	1.2	@ISA = $MODEL;
129
130			my $class = shift;
131			$class->$AUTOLOAD (@_);
132	root	1.1	}
133
134	root	1.2	=back
135
136	root	1.8	=head1 SUPPLYING YOUR OWN EVENT MODEL INTERFACE
137
138			If you need to support another event library which isn't directly
139			supported by AnyEvent, you can supply your own interface to it by
140			pushing, before the first watch gets created, the package name of
141			the event module and the package name of the interface to use onto
142			C<@AnyEvent::REGISTRY>. You can do that before and even without loading
143			AnyEvent.
144
145			Example:
146
147			push @AnyEvent::REGISTRY, [urxvt => urxvt::anyevent::];
148
149			This tells AnyEvent to (literally) use the C<urxvt::anyevent::> module
150			when it finds the C<urxvt> module is loaded. When AnyEvent is loaded and
151			requested to find a suitable event model, it will first check for the
152			urxvt module.
153
154			The above isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt) uses
155			the above line exactly. An interface isn't included in AnyEvent
156			because it doesn't make sense outside the embedded interpreter inside
157			I<rxvt-unicode>, and it is updated and maintained as part of the
158			I<rxvt-unicode> distribution.
159
160	root	1.7	=head1 ENVIRONMENT VARIABLES
161
162			The following environment variables are used by this module:
163
164			C<PERL_ANYEVENT_VERBOSE> when set to C<2> or higher, reports which event
165			model gets used.
166
167	root	1.2	=head1 EXAMPLE
168
169			The following program uses an io watcher to read data from stdin, a timer
170			to display a message once per second, and a condvar to exit the program
171			when the user enters quit:
172
173			use AnyEvent;
174
175			my $cv = AnyEvent->condvar;
176
177			my $io_watcher = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
178			warn "io event <$_[0]>\n"; # will always output <r>
179			chomp (my $input = <STDIN>); # read a line
180			warn "read: $input\n"; # output what has been read
181			$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i
182			});
183
184			my $time_watcher; # can only be used once
185
186			sub new_timer {
187			$timer = AnyEvent->timer (after => 1, cb => sub {
188			warn "timeout\n"; # print 'timeout' about every second
189			&new_timer; # and restart the time
190			});
191			}
192
193			new_timer; # create first timer
194
195			$cv->wait; # wait until user enters /^q/i
196
197	root	1.5	=head1 REAL-WORLD EXAMPLE
198
199			Consider the L<Net::FCP> module. It features (among others) the following
200			API calls, which are to freenet what HTTP GET requests are to http:
201
202			my $data = $fcp->client_get ($url); # blocks
203
204			my $transaction = $fcp->txn_client_get ($url); # does not block
205			$transaction->cb ( sub { ... } ); # set optional result callback
206			my $data = $transaction->result; # possibly blocks
207
208			The C<client_get> method works like C<LWP::Simple::get>: it requests the
209			given URL and waits till the data has arrived. It is defined to be:
210
211			sub client_get { $_[0]->txn_client_get ($_[1])->result }
212
213			And in fact is automatically generated. This is the blocking API of
214			L<Net::FCP>, and it works as simple as in any other, similar, module.
215
216			More complicated is C<txn_client_get>: It only creates a transaction
217			(completion, result, ...) object and initiates the transaction.
218
219			my $txn = bless { }, Net::FCP::Txn::;
220
221			It also creates a condition variable that is used to signal the completion
222			of the request:
223
224			$txn->{finished} = AnyAvent->condvar;
225
226			It then creates a socket in non-blocking mode.
227
228			socket $txn->{fh}, ...;
229			fcntl $txn->{fh}, F_SETFL, O_NONBLOCK;
230			connect $txn->{fh}, ...
231			and !$!{EWOULDBLOCK}
232			and !$!{EINPROGRESS}
233			and Carp::croak "unable to connect: $!\n";
234
235	root	1.6	Then it creates a write-watcher which gets called whenever an error occurs
236	root	1.5	or the connection succeeds:
237
238			$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'w', cb => sub { $txn->fh_ready_w });
239
240			And returns this transaction object. The C<fh_ready_w> callback gets
241			called as soon as the event loop detects that the socket is ready for
242			writing.
243
244			The C<fh_ready_w> method makes the socket blocking again, writes the
245			request data and replaces the watcher by a read watcher (waiting for reply
246			data). The actual code is more complicated, but that doesn't matter for
247			this example:
248
249			fcntl $txn->{fh}, F_SETFL, 0;
250			syswrite $txn->{fh}, $txn->{request}
251			or die "connection or write error";
252			$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
253
254			Again, C<fh_ready_r> waits till all data has arrived, and then stores the
255			result and signals any possible waiters that the request ahs finished:
256
257			sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
258
259			if (end-of-file or data complete) {
260			$txn->{result} = $txn->{buf};
261			$txn->{finished}->broadcast;
262	root	1.6	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
263	root	1.5	}
264
265			The C<result> method, finally, just waits for the finished signal (if the
266			request was already finished, it doesn't wait, of course, and returns the
267			data:
268
269			$txn->{finished}->wait;
270	root	1.6	return $txn->{result};
271	root	1.5
272			The actual code goes further and collects all errors (C<die>s, exceptions)
273			that occured during request processing. The C<result> method detects
274			wether an exception as thrown (it is stored inside the $txn object)
275			and just throws the exception, which means connection errors and other
276			problems get reported tot he code that tries to use the result, not in a
277			random callback.
278
279			All of this enables the following usage styles:
280
281			1. Blocking:
282
283			my $data = $fcp->client_get ($url);
284
285			2. Blocking, but parallelizing:
286
287			my @datas = map $_->result,
288			map $fcp->txn_client_get ($_),
289			@urls;
290
291			Both blocking examples work without the module user having to know
292			anything about events.
293
294			3a. Event-based in a main program, using any support Event module:
295
296			use Event;
297
298			$fcp->txn_client_get ($url)->cb (sub {
299			my $txn = shift;
300			my $data = $txn->result;
301			...
302			});
303
304			Event::loop;
305
306			3b. The module user could use AnyEvent, too:
307
308			use AnyEvent;
309
310			my $quit = AnyEvent->condvar;
311
312			$fcp->txn_client_get ($url)->cb (sub {
313			...
314			$quit->broadcast;
315			});
316
317			$quit->wait;
318
319	root	1.2	=head1 SEE ALSO
320
321	root	1.5	Event modules: L<Coro::Event>, L<Coro>, L<Event>, L<Glib::Event>, L<Glib>.
322
323			Implementations: L<AnyEvent::Impl::Coro>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>.
324
325			Nontrivial usage example: L<Net::FCP>.
326	root	1.2
327			=head1
328
329			=cut
330
331			1
332	root	1.1