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 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 prove 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:	1.12
Committed:	Thu Jul 20 01:39:40 2006 UTC (17 years, 11 months ago) by root
Branch:	MAIN
Changes since 1.11:	+16 -6 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	root	1.11	pushing, before the first watcher gets created, the package name of
141	root	1.8	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	root	1.12	This tells AnyEvent to (literally) use the C<urxvt::anyevent::>
150			package/class when it finds the C<urxvt> package/module is loaded. When
151			AnyEvent is loaded and asked to find a suitable event model, it will
152			first check for the presence of urxvt.
153
154			The class should prove implementations for all watcher types (see
155			L<AnyEvent::Impl::Event> (source code), L<AnyEvent::Impl::Glib>
156			(Source code) and so on for actual examples, use C<perldoc -m
157			AnyEvent::Impl::Glib> to see the sources).
158	root	1.8
159	root	1.12	The above isn't fictitious, the I<rxvt-unicode> (a.k.a. urxvt)
160			uses the above line as-is. An interface isn't included in AnyEvent
161	root	1.8	because it doesn't make sense outside the embedded interpreter inside
162			I<rxvt-unicode>, and it is updated and maintained as part of the
163			I<rxvt-unicode> distribution.
164
165	root	1.12	I<rxvt-unicode> also cheats a bit by not providing blocking access to
166			condition variables: code blocking while waiting for a condition will
167			C<die>. This still works with most modules/usages, and blocking calls must
168			not be in an interactive appliation, so it makes sense.
169
170	root	1.7	=head1 ENVIRONMENT VARIABLES
171
172			The following environment variables are used by this module:
173
174			C<PERL_ANYEVENT_VERBOSE> when set to C<2> or higher, reports which event
175			model gets used.
176
177	root	1.2	=head1 EXAMPLE
178
179			The following program uses an io watcher to read data from stdin, a timer
180			to display a message once per second, and a condvar to exit the program
181			when the user enters quit:
182
183			use AnyEvent;
184
185			my $cv = AnyEvent->condvar;
186
187			my $io_watcher = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {
188			warn "io event <$_[0]>\n"; # will always output <r>
189			chomp (my $input = <STDIN>); # read a line
190			warn "read: $input\n"; # output what has been read
191			$cv->broadcast if $input =~ /^q/i; # quit program if /^q/i
192			});
193
194			my $time_watcher; # can only be used once
195
196			sub new_timer {
197			$timer = AnyEvent->timer (after => 1, cb => sub {
198			warn "timeout\n"; # print 'timeout' about every second
199			&new_timer; # and restart the time
200			});
201			}
202
203			new_timer; # create first timer
204
205			$cv->wait; # wait until user enters /^q/i
206
207	root	1.5	=head1 REAL-WORLD EXAMPLE
208
209			Consider the L<Net::FCP> module. It features (among others) the following
210			API calls, which are to freenet what HTTP GET requests are to http:
211
212			my $data = $fcp->client_get ($url); # blocks
213
214			my $transaction = $fcp->txn_client_get ($url); # does not block
215			$transaction->cb ( sub { ... } ); # set optional result callback
216			my $data = $transaction->result; # possibly blocks
217
218			The C<client_get> method works like C<LWP::Simple::get>: it requests the
219			given URL and waits till the data has arrived. It is defined to be:
220
221			sub client_get { $_[0]->txn_client_get ($_[1])->result }
222
223			And in fact is automatically generated. This is the blocking API of
224			L<Net::FCP>, and it works as simple as in any other, similar, module.
225
226			More complicated is C<txn_client_get>: It only creates a transaction
227			(completion, result, ...) object and initiates the transaction.
228
229			my $txn = bless { }, Net::FCP::Txn::;
230
231			It also creates a condition variable that is used to signal the completion
232			of the request:
233
234			$txn->{finished} = AnyAvent->condvar;
235
236			It then creates a socket in non-blocking mode.
237
238			socket $txn->{fh}, ...;
239			fcntl $txn->{fh}, F_SETFL, O_NONBLOCK;
240			connect $txn->{fh}, ...
241			and !$!{EWOULDBLOCK}
242			and !$!{EINPROGRESS}
243			and Carp::croak "unable to connect: $!\n";
244
245	root	1.6	Then it creates a write-watcher which gets called whenever an error occurs
246	root	1.5	or the connection succeeds:
247
248			$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'w', cb => sub { $txn->fh_ready_w });
249
250			And returns this transaction object. The C<fh_ready_w> callback gets
251			called as soon as the event loop detects that the socket is ready for
252			writing.
253
254			The C<fh_ready_w> method makes the socket blocking again, writes the
255			request data and replaces the watcher by a read watcher (waiting for reply
256			data). The actual code is more complicated, but that doesn't matter for
257			this example:
258
259			fcntl $txn->{fh}, F_SETFL, 0;
260			syswrite $txn->{fh}, $txn->{request}
261			or die "connection or write error";
262			$txn->{w} = AnyEvent->io (fh => $txn->{fh}, poll => 'r', cb => sub { $txn->fh_ready_r });
263
264			Again, C<fh_ready_r> waits till all data has arrived, and then stores the
265			result and signals any possible waiters that the request ahs finished:
266
267			sysread $txn->{fh}, $txn->{buf}, length $txn->{$buf};
268
269			if (end-of-file or data complete) {
270			$txn->{result} = $txn->{buf};
271			$txn->{finished}->broadcast;
272	root	1.6	$txb->{cb}->($txn) of $txn->{cb}; # also call callback
273	root	1.5	}
274
275			The C<result> method, finally, just waits for the finished signal (if the
276			request was already finished, it doesn't wait, of course, and returns the
277			data:
278
279			$txn->{finished}->wait;
280	root	1.6	return $txn->{result};
281	root	1.5
282			The actual code goes further and collects all errors (C<die>s, exceptions)
283			that occured during request processing. The C<result> method detects
284			wether an exception as thrown (it is stored inside the $txn object)
285			and just throws the exception, which means connection errors and other
286			problems get reported tot he code that tries to use the result, not in a
287			random callback.
288
289			All of this enables the following usage styles:
290
291			1. Blocking:
292
293			my $data = $fcp->client_get ($url);
294
295			2. Blocking, but parallelizing:
296
297			my @datas = map $_->result,
298			map $fcp->txn_client_get ($_),
299			@urls;
300
301			Both blocking examples work without the module user having to know
302			anything about events.
303
304			3a. Event-based in a main program, using any support Event module:
305
306			use Event;
307
308			$fcp->txn_client_get ($url)->cb (sub {
309			my $txn = shift;
310			my $data = $txn->result;
311			...
312			});
313
314			Event::loop;
315
316			3b. The module user could use AnyEvent, too:
317
318			use AnyEvent;
319
320			my $quit = AnyEvent->condvar;
321
322			$fcp->txn_client_get ($url)->cb (sub {
323			...
324			$quit->broadcast;
325			});
326
327			$quit->wait;
328
329	root	1.2	=head1 SEE ALSO
330
331	root	1.5	Event modules: L<Coro::Event>, L<Coro>, L<Event>, L<Glib::Event>, L<Glib>.
332
333			Implementations: L<AnyEvent::Impl::Coro>, L<AnyEvent::Impl::Event>, L<AnyEvent::Impl::Glib>, L<AnyEvent::Impl::Tk>.
334
335			Nontrivial usage example: L<Net::FCP>.
336	root	1.2
337			=head1
338
339			=cut
340
341			1
342	root	1.1