EV-Loop-Async/Async.pm

=head1 NAME

EV::Loop::Async - run an EV event loop asynchronously

=head1 SYNOPSIS

  use EV::Loop::Async;
  
  my $loop = EV::Loop::Async::default;
  my $timer;
  my $flag;
  
  # create a watcher, but make sure the loop is locked
  {
     $loop->scope_lock; # lock the loop structures
     $timer = $loop->timer (5, 1, sub { $flag = 1 });
     $loop->notify; # tell loop to take note of the timer
  }
  
  1 while $flag; # $flag will be set asynchronously
  
  # implement a critical section, uninterrupted by any callbacks
  {
     $loop->interrupt->scope_block;
     # critical section, no watcher callback interruptions
  }
  
  # stop the timer watcher again - locking is required once more
  {
     $loop->scope_lock; # lock the loop structures
     $timer->stop;
     # no need to notify
  }

=head1 DESCRIPTION

This module implements a rather specialised event loop - it takes a normal
L<EV> event loop and runs it in a separate thread. That means it will poll
for events even while your foreground Perl interpreter is busy (you don't
need to have perls pseudo-threads enabled for this either).

Whenever the event loop detecs new events, it will interrupt perl and ask
it to invoke all the pending watcher callbacks. This invocation will be
"synchronous" (in the perl thread), but it can happen at any time.

See the documentation for L<Async::Interrupt> for details on when and how
your perl program can be interrupted (and how to avoid it), and how to
integrate background event loops into foreground ones.

=head1 FAQ

=over 4

=item Why on earth...???

Sometimes you need lower latency for specific events, but it's too heavy
to continuously poll for events. And perl already does this for you
anyways, so this module only uses this existing mechanism.

=item When do I have to lock?

When in doubt, lock. Do not start or stop a watcher, do not create a
watcher (unless with the C<_ns> methods) and do not DESTROY an active
watcher without locking either.

Any other event loop modifications need to be done while locked as
well. So when in doubt, lock (best using C<scope_lock>).

=item Why explicit locking?

Because I was too lazy to wrap everything and there are probably only a
few people on this world using this module.

=back

=head1 FUNCTIONS, METHODS AND VARIABLES OF THIS MODULE

=over 4

=cut

package EV::Loop::Async;

use common::sense;

use EV ();
use Async::Interrupt ();

use base 'EV::Loop';

BEGIN {
   our $VERSION = '1.01';

   require XSLoader;
   XSLoader::load ("EV::Loop::Async", $VERSION);
}

=item $loop = EV::Loop::Async::default

Return the default loop, usable by all programs. The default loop will be
created on the first call to C<default> by calling X<new EV::Loop>, and
should be used by all programs unless they have special requirements.

The associated L<Async::Interrupt> object is stored in
C<$EV::Loop::Async::AI>, and can be used to lock critical sections etc.

=cut

our ($LOOP, $INTERRUPT);

sub default() {
   $LOOP || do {
      $LOOP      = new EV::Loop::Async;
      $INTERRUPT = $LOOP->interrupt;

      $LOOP
   }
}

=item $EV::Loop::Async::LOOP

The default async loop, available after the first call to
C<EV::Loop::Async::default>.

=item $EV::Loop::Async::INTERRUPT

The default loop's L<Async::Interrupt> object, for easy access.

Example: create a section of code where no callback invocations will
interrupt:

   {
      $EV::Loop::Async::INTERRUPT->scope_block;
      # no default loop callbacks will be executed here.
      # the loop will not be locked, however.
   }

Example: embed the default EV::Async::Loop loop into the default L<EV>
loop (note that it could be any other event loop as well).

   my $async_w = EV::io
                    $EV::Loop::Async::LOOP->interrupt->pipe_fileno,
                    EV::READ,
                    sub { };

=item $loop = new EV::Loop::Async $flags, [Async-Interrupt-Arguments...]

This constructor:

=over 4

=item 1. creates a new C<EV::Loop> (similar C<new EV::Loop>).

=item 2. creates a new L<Async::Interrupt> object and attaches itself to it.

=item 3. creates a new background thread.

=item 4. runs C<< $loop->run >> in that thread.

=back

The resulting loop will be running and unlocked when it is returned.

Example: create a new loop, block it's interrupt object and embed
it into the foreground L<AnyEvent> event loop. This basically runs the
C<EV::Loop::Async> loop in a synchronous way inside another loop.

   my $loop  = new EV::Loop::Async 0;
   my $async = $loop->interrupt;

   $async->block;

   my $async_w = AnyEvent->io (
      fh => $async->pipe_fileno,
      poll => "r",
      cb => sub {
         # temporarily unblock to handle events
         $async->unblock;
         $async->block;
      },
   );

=cut

sub new {
   my ($class, $flags, @asy) = @_;

   my $self = bless $class->SUPER::new ($flags), $class;
   my ($c_func, $c_arg) = _c_func $self;
   my $asy = new Async::Interrupt @asy, c_cb => [$c_func, $c_arg];
   _attach $self, $asy, $asy->signal_func;

   $self
}

=item $loop->notify

Wake up the asynchronous loop. This is useful after registering a new
watcher, to ensure that the background event loop integrates the new
watcher(s) (which only happens when it iterates, which you can force by
calling this method).

Without calling this method, the event loop I<eventually> takes notice
of new watchers, bit when this happens is not well-defined (can be
instantaneous, or take a few hours).

No locking is required.

Example: lock the loop, create a timer, nudge the loop so it takes notice
of the new timer, then evily busy-wait till the timer fires.

   my $timer;
   my $flag;

   {
      $loop->scope_lock;
      $timer = $loop->timer (1, 0, sub { $flag = 1 });
      $loop->notify;
   }

   1 until $flag;

=item $loop->lock

=item $loop->unlock

Lock/unlock the loop data structures. Since the event loop runs in
a separate thread, you have to lock the loop data structures before
accessing them in any way. Since I was lazy, you have to do this manually.

You must lock under the same conditions as you would have to lock the
underlying C library, e.g. when starting or stopping watchers (but not
when creating or destroying them, but note that create and destroy often
starts and stops for you, in which case you have to lock).

When in doubt, lock.

See also the next method, C<< $loop->scope_lock >> for a more failsafe way
to lock parts of your code.

Note that there must be exactly one call of "unblock" for every previous
call to "block" (i.e. calls can nest).

=item $loop->scope_lock

Calls C<lock> immediately, and C<unlock> automatically whent he current
scope is left.

=item $loop->set_max_foreground_loops ($max_loops)

The background loop will immediately stop polling for new events after it
has collected at least one new event, regardless of how long it then takes
to actually handle them.

When Perl finally handles the events, there could be many more ready
file descriptors. To improve latency and performance, you can ask
C<EV::Loop::Async> to loop an additional number of times in the foreground
after invoking the callbacks, effectively doing the polling in the
foreground.

The default is C<0>, meaning that no foreground polling will be done. A
value of C<1> means that, after handling the pending events, it will call
C<< $loop->loop (EV::LOOP_NONBLOCK) >> and handle the resulting events, if
any. A value of C<2> means that this will be iterated twice.

When a foreground event poll does not yield any new events, then no
further iterations will be made, so this is only a I<maximum> value of
additional loop runs.

Take also note of the standard EV C<set_io_collect_interval>
functionality, which can achieve a similar, but different, effect - YMMV.

=back

=head1 SEE ALSO

L<EV>, L<Async::Interrupt>.

=head1 AUTHOR

 Marc Lehmann <schmorp@schmorp.de>
 http://home.schmorp.de/

=cut

1

Revision:	1.9
Committed:	Mon Nov 1 22:28:41 2010 UTC (15 years, 4 months ago) by root
Branch:	MAIN
CVS Tags:	rel-1_01, HEAD
Changes since 1.8:	+1 -1 lines
Log Message:	1.01
#	Content
1	=head1 NAME
2
3	EV::Loop::Async - run an EV event loop asynchronously
4
5	=head1 SYNOPSIS
6
7	use EV::Loop::Async;
8
9	my $loop = EV::Loop::Async::default;
10	my $timer;
11	my $flag;
12
13	# create a watcher, but make sure the loop is locked
14	{
15	$loop->scope_lock; # lock the loop structures
16	$timer = $loop->timer (5, 1, sub { $flag = 1 });
17	$loop->notify; # tell loop to take note of the timer
18	}
19
20	1 while $flag; # $flag will be set asynchronously
21
22	# implement a critical section, uninterrupted by any callbacks
23	{
24	$loop->interrupt->scope_block;
25	# critical section, no watcher callback interruptions
26	}
27
28	# stop the timer watcher again - locking is required once more
29	{
30	$loop->scope_lock; # lock the loop structures
31	$timer->stop;
32	# no need to notify
33	}
34
35	=head1 DESCRIPTION
36
37	This module implements a rather specialised event loop - it takes a normal
38	L<EV> event loop and runs it in a separate thread. That means it will poll
39	for events even while your foreground Perl interpreter is busy (you don't
40	need to have perls pseudo-threads enabled for this either).
41
42	Whenever the event loop detecs new events, it will interrupt perl and ask
43	it to invoke all the pending watcher callbacks. This invocation will be
44	"synchronous" (in the perl thread), but it can happen at any time.
45
46	See the documentation for L<Async::Interrupt> for details on when and how
47	your perl program can be interrupted (and how to avoid it), and how to
48	integrate background event loops into foreground ones.
49
50	=head1 FAQ
51
52	=over 4
53
54	=item Why on earth...???
55
56	Sometimes you need lower latency for specific events, but it's too heavy
57	to continuously poll for events. And perl already does this for you
58	anyways, so this module only uses this existing mechanism.
59
60	=item When do I have to lock?
61
62	When in doubt, lock. Do not start or stop a watcher, do not create a
63	watcher (unless with the C<_ns> methods) and do not DESTROY an active
64	watcher without locking either.
65
66	Any other event loop modifications need to be done while locked as
67	well. So when in doubt, lock (best using C<scope_lock>).
68
69	=item Why explicit locking?
70
71	Because I was too lazy to wrap everything and there are probably only a
72	few people on this world using this module.
73
74	=back
75
76	=head1 FUNCTIONS, METHODS AND VARIABLES OF THIS MODULE
77
78	=over 4
79
80	=cut
81
82	package EV::Loop::Async;
83
84	use common::sense;
85
86	use EV ();
87	use Async::Interrupt ();
88
89	use base 'EV::Loop';
90
91	BEGIN {
92	our $VERSION = '1.01';
93
94	require XSLoader;
95	XSLoader::load ("EV::Loop::Async", $VERSION);
96	}
97
98	=item $loop = EV::Loop::Async::default
99
100	Return the default loop, usable by all programs. The default loop will be
101	created on the first call to C<default> by calling X<new EV::Loop>, and
102	should be used by all programs unless they have special requirements.
103
104	The associated L<Async::Interrupt> object is stored in
105	C<$EV::Loop::Async::AI>, and can be used to lock critical sections etc.
106
107	=cut
108
109	our ($LOOP, $INTERRUPT);
110
111	sub default() {
112	$LOOP \|\| do {
113	$LOOP = new EV::Loop::Async;
114	$INTERRUPT = $LOOP->interrupt;
115
116	$LOOP
117	}
118	}
119
120	=item $EV::Loop::Async::LOOP
121
122	The default async loop, available after the first call to
123	C<EV::Loop::Async::default>.
124
125	=item $EV::Loop::Async::INTERRUPT
126
127	The default loop's L<Async::Interrupt> object, for easy access.
128
129	Example: create a section of code where no callback invocations will
130	interrupt:
131
132	{
133	$EV::Loop::Async::INTERRUPT->scope_block;
134	# no default loop callbacks will be executed here.
135	# the loop will not be locked, however.
136	}
137
138	Example: embed the default EV::Async::Loop loop into the default L<EV>
139	loop (note that it could be any other event loop as well).
140
141	my $async_w = EV::io
142	$EV::Loop::Async::LOOP->interrupt->pipe_fileno,
143	EV::READ,
144	sub { };
145
146	=item $loop = new EV::Loop::Async $flags, [Async-Interrupt-Arguments...]
147
148	This constructor:
149
150	=over 4
151
152	=item 1. creates a new C<EV::Loop> (similar C<new EV::Loop>).
153
154	=item 2. creates a new L<Async::Interrupt> object and attaches itself to it.
155
156	=item 3. creates a new background thread.
157
158	=item 4. runs C<< $loop->run >> in that thread.
159
160	=back
161
162	The resulting loop will be running and unlocked when it is returned.
163
164	Example: create a new loop, block it's interrupt object and embed
165	it into the foreground L<AnyEvent> event loop. This basically runs the
166	C<EV::Loop::Async> loop in a synchronous way inside another loop.
167
168	my $loop = new EV::Loop::Async 0;
169	my $async = $loop->interrupt;
170
171	$async->block;
172
173	my $async_w = AnyEvent->io (
174	fh => $async->pipe_fileno,
175	poll => "r",
176	cb => sub {
177	# temporarily unblock to handle events
178	$async->unblock;
179	$async->block;
180	},
181	);
182
183	=cut
184
185	sub new {
186	my ($class, $flags, @asy) = @_;
187
188	my $self = bless $class->SUPER::new ($flags), $class;
189	my ($c_func, $c_arg) = _c_func $self;
190	my $asy = new Async::Interrupt @asy, c_cb => [$c_func, $c_arg];
191	_attach $self, $asy, $asy->signal_func;
192
193	$self
194	}
195
196	=item $loop->notify
197
198	Wake up the asynchronous loop. This is useful after registering a new
199	watcher, to ensure that the background event loop integrates the new
200	watcher(s) (which only happens when it iterates, which you can force by
201	calling this method).
202
203	Without calling this method, the event loop I<eventually> takes notice
204	of new watchers, bit when this happens is not well-defined (can be
205	instantaneous, or take a few hours).
206
207	No locking is required.
208
209	Example: lock the loop, create a timer, nudge the loop so it takes notice
210	of the new timer, then evily busy-wait till the timer fires.
211
212	my $timer;
213	my $flag;
214
215	{
216	$loop->scope_lock;
217	$timer = $loop->timer (1, 0, sub { $flag = 1 });
218	$loop->notify;
219	}
220
221	1 until $flag;
222
223	=item $loop->lock
224
225	=item $loop->unlock
226
227	Lock/unlock the loop data structures. Since the event loop runs in
228	a separate thread, you have to lock the loop data structures before
229	accessing them in any way. Since I was lazy, you have to do this manually.
230
231	You must lock under the same conditions as you would have to lock the
232	underlying C library, e.g. when starting or stopping watchers (but not
233	when creating or destroying them, but note that create and destroy often
234	starts and stops for you, in which case you have to lock).
235
236	When in doubt, lock.
237
238	See also the next method, C<< $loop->scope_lock >> for a more failsafe way
239	to lock parts of your code.
240
241	Note that there must be exactly one call of "unblock" for every previous
242	call to "block" (i.e. calls can nest).
243
244	=item $loop->scope_lock
245
246	Calls C<lock> immediately, and C<unlock> automatically whent he current
247	scope is left.
248
249	=item $loop->set_max_foreground_loops ($max_loops)
250
251	The background loop will immediately stop polling for new events after it
252	has collected at least one new event, regardless of how long it then takes
253	to actually handle them.
254
255	When Perl finally handles the events, there could be many more ready
256	file descriptors. To improve latency and performance, you can ask
257	C<EV::Loop::Async> to loop an additional number of times in the foreground
258	after invoking the callbacks, effectively doing the polling in the
259	foreground.
260
261	The default is C<0>, meaning that no foreground polling will be done. A
262	value of C<1> means that, after handling the pending events, it will call
263	C<< $loop->loop (EV::LOOP_NONBLOCK) >> and handle the resulting events, if
264	any. A value of C<2> means that this will be iterated twice.
265
266	When a foreground event poll does not yield any new events, then no
267	further iterations will be made, so this is only a I<maximum> value of
268	additional loop runs.
269
270	Take also note of the standard EV C<set_io_collect_interval>
271	functionality, which can achieve a similar, but different, effect - YMMV.
272
273	=back
274
275	=head1 SEE ALSO
276
277	L<EV>, L<Async::Interrupt>.
278
279	=head1 AUTHOR
280
281	Marc Lehmann <schmorp@schmorp.de>
282	http://home.schmorp.de/
283
284	=cut
285
286	1
287