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 = '1.0';
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:	1.8
Committed:	Sun Jan 8 04:20:05 2006 UTC (20 years, 2 months ago) by root
Branch:	MAIN
CVS Tags:	rel-1_0
Changes since 1.7:	+45 -15 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 = '1.0';
74	our $MODEL;
75
76	our $AUTOLOAD;
77	our @ISA;
78
79	our $verbose = $ENV{PERL_ANYEVENT_VERBOSE}*1;
80
81	our @REGISTRY;
82
83	my @models = (
84	[Coro::Event:: => AnyEvent::Impl::Coro::],
85	[Event:: => AnyEvent::Impl::Event::],
86	[Glib:: => AnyEvent::Impl::Glib::],
87	[Tk:: => AnyEvent::Impl::Tk::],
88	);
89
90	our %method = map +($_ => 1), qw(io timer condvar broadcast wait cancel DESTROY);
91
92	sub AUTOLOAD {
93	$AUTOLOAD =~ s/.*://;
94
95	$method{$AUTOLOAD}
96	or croak "$AUTOLOAD: not a valid method for AnyEvent objects";
97
98	unless ($MODEL) {
99	# check for already loaded models
100	for (@REGISTRY, @models) {
101	my ($package, $model) = @$_;
102	if (${"$package\::VERSION"} > 0) {
103	if (eval "require $model") {
104	$MODEL = $model;
105	warn "AnyEvent: found model '$model', using it.\n" if $verbose > 1;
106	last;
107	}
108	}
109	}
110
111	unless ($MODEL) {
112	# try to load a model
113
114	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	}
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	}
126	}
127
128	@ISA = $MODEL;
129
130	my $class = shift;
131	$class->$AUTOLOAD (@_);
132	}
133
134	=back
135
136	=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	=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	=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	=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	Then it creates a write-watcher which gets called whenever an error occurs
236	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	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
263	}
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	return $txn->{result};
271
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	=head1 SEE ALSO
320
321	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
327	=head1
328
329	=cut
330
331	1
332