Coro/Coro/AnyEvent.pm

=head1 NAME

Coro::AnyEvent - integrate threads into AnyEvent

=head1 SYNOPSIS

 use Coro;
 use AnyEvent;
 # using both Coro and AnyEvent will automatically load Coro::AnyEvent

 # or load it manually for it's utility functions:
 use Coro::AnyEvent;

 Coro::AnyEvent::sleep 5;     # block current thread for 5s
 Coro::AnyEvent::poll;        # poll for new events once
 Coro::AnyEvent::idle;        # block until process no longer busy
 Coro::AnyEvent::idle_upto 5; # same, but only up to 5 seconds

 Coro::AnyEvent::readable $fh, 60
    or die "fh didn't become readable within 60 seconds\n";

=head1 DESCRIPTION

When one naively starts to use threads in Perl, one will quickly run
into the problem that threads that block on a syscall (sleeping,
reading from a socket etc.) will block all threads.

If one then uses an event loop, the problem is that the event loop has
no knowledge of threads and will not run them before it polls for new
events, again blocking the whole process.

This module integrates threads into any event loop supported by
AnyEvent, combining event-based programming with coroutine-based
programming in a natural way.

As of Coro 5.21 and newer, this module gets loaded automatically when
AnyEvent initialises itself and Coro is used in the same process, thus
there is no need to load it manually if you just want your threads to
coexist with AnyEvent.

If you want to use any functions from this module, you of course still
need to C<use Coro::AnyEvent>, just as with other perl modules.

Also, this module autodetects the event loop used (by relying on
L<AnyEvent>) and will either automatically defer to the high-performance
L<Coro::EV> or L<Coro::Event> modules, or will use a generic integration
method that should work with any event loop supported by L<AnyEvent>.

=head1 USAGE

=head2 RUN AN EVENT LOOP - OR NOT?

For performance reasons, it is recommended that the main program or
something else runs the event loop of the event model you use, i.e.

   use Gtk2; # <- the event model
   use AnyEvent;
   use Coro:

   # initialise stuff
   async { ... };

   # now run mainloop of Gtk2
   main Gtk2;

You can move the event loop into a thread as well, although this tends to
get confusing:

   use Gtk2;
   use AnyEvent;
   use Coro:

   async { main Gtk2 };

   # do other things...
   while () {
      use Coro::AnyEvent;
      Coro::AnyEvent::sleep 1;
      print "ping...\n";
   }

You can also do nothing, in which case Coro:AnyEvent will invoke the event
loop as needed, which is less efficient, but sometimes very convenient.

What you I<MUST NOT DO EVER> is to block inside an event loop
callback. The reason is that most event loops are not reentrant and this
can cause a deadlock at best and corrupt memory at worst.

Coro will try to catch you when you block in the event loop
("FATAL:$Coro::IDLE blocked itself"), but this is just best effort and
only works when you do not run your own event loop.

To avoid this problem, simply do not block inside an event callback
- start a new thread (e.g. with C<Coro:async_pool>) or use
C<Coro::unblock_sub>.

=head2 INVERSION OF CONTROL

If you need to wait for a single event, the rouse functions will come in
handy (see the Coro manpage for details):

   # wait for single SIGINT
   {
      my $int_w = AnyEvent->signal (signal => "INT", cb => Coro::rouse_cb);
      Coro::rouse_wait;
   }

=head2 EVENT MODULES OTHER THEN ANYEVENT

Keep in mind that, as shipped, Coro and Coro::AnyEvent only work with
AnyEvent, and only when AnyEvent is actually used (i.e. initialised), so
this will not work:

   # does not work: EV without AnyEvent is not recognised
   use EV;
   use Coro;

   EV::loop;

And neither does this, unless you actually I<use> AnyEvent for something:

   # does not work: AnyEvent must be initialised (e.g. by creating watchers)
   use EV;
   use AnyEvent;
   use Coro;

   EV::loop;

This does work, however, because you create a watcher (condvars work,
too), thus forcing AnyEvent to initialise itself:

   # does work: AnyEvent is actually used
   use EV;
   use AnyEvent;
   use Coro;

   my $timer = AE::timer 1, 1, sub { };

   EV::loop;

And if you want to use AnyEvent just to bridge between Coro and your event
model of choice, you can simply force it to initialise itself, like this:

   # does work: AnyEvent is initialised manually
   use POE;
   use AnyEvent;
   use Coro;

   AnyEvent::detect; # force AnyEvent to integrate Coro into POE
   POE::Kernel->run;

=head1 FUNCTIONS

Coro::AnyEvent also offers a few functions that might be useful.

=over 4

=cut

package Coro::AnyEvent;

use common::sense;

use Coro;
use AnyEvent ();

our $VERSION = 5.25;

#############################################################################
# idle handler

our $IDLE;

#############################################################################
# 0-timeout idle emulation watcher

our $ACTIVITY;

sub _activity {
   $ACTIVITY ||= AE::timer 0, 0, \&_schedule;
}

Coro::_set_readyhook (\&AnyEvent::detect);

AnyEvent::post_detect {
   unshift @AnyEvent::CondVar::ISA, "Coro::AnyEvent::CondVar";

   my $model = $AnyEvent::MODEL;

   if ($model eq "AnyEvent::Impl::EV" and eval { require Coro::EV }) {
      # provide faster versions of some functions
      Coro::EV::_set_readyhook ();

      eval '
         *sleep = \&Coro::EV::timer_once;
         *poll  = \&Coro::EV::_poll;
         *idle  = sub() {
            my $w = EV::idle Coro::rouse_cb;
            Coro::rouse_wait;
         };
         *idle_upto = sub($) {
            my $cb = Coro::rouse_cb;
            my $t = EV::timer $_[0], 0, $cb;
            my $w = EV::idle $cb;
            Coro::rouse_wait;
         };
         *readable = sub($;$) {
            EV::READ  & Coro::EV::timed_io_once $_[0], EV::READ , $_[1]
         };
         *writable = sub($;$) {
            EV::WRITE & Coro::EV::timed_io_once $_[0], EV::WRITE, $_[1]
         };
      ';
      die if $@;

   } elsif ($model eq "AnyEvent::Impl::Event" and eval { require Coro::Event }) {
      Coro::_set_readyhook undef;
      # let Coro::Event do its thing
   } else {
      # do the inefficient thing ourselves
      Coro::_set_readyhook \&_activity;

      $IDLE = new Coro sub {
         my $one_event = AnyEvent->can ("one_event");

         while () {
            $one_event->();
            Coro::schedule if Coro::nready;
         }
      };
      $IDLE->{desc} = "[AnyEvent idle process]";

      $Coro::idle = $IDLE;

      # call the readyhook, in case coroutines were already readied
      _activity;
   }
};

=item Coro::AnyEvent::poll

This call will block the current thread until the event loop has polled
for new events and instructs the event loop to poll for new events once,
without blocking.

Note that this call will not actually execute the poll, just block until
new events have been polled, so other threads will have a chance to run.

This is useful when you have a thread that does some computations, but you
still want to poll for new events from time to time. Simply call C<poll>
from time to time:

   my $long_calc = async {
      for (1..10000) {
         Coro::AnyEvent::poll:
         # do some stuff, make sure it takes at least 0.001s or so
      }
   }

Although you should also consider C<idle> or C<idle_upto> in such cases.

=item Coro::AnyEvent::sleep $seconds

This blocks the current thread for at least the given number of seconds.

=item Coro::AnyEvent::idle

This call is similar to C<poll> in that it will also poll for
events. Unlike C<poll>, it will only resume the thread once there are no
events to handle anymore, i.e. when the process is otherwise idle.

This is good for background threads that shouldn't use CPU time when
foreground jobs are ready to run.

=item Coro::AnyEvent::idle_upto $seconds

Like C<idle>, but with a maximum waiting time.

If your process is busy handling events, calling C<idle> can mean that
your thread will never be resumed. To avoid this, you can use C<idle_upto>
and specify a timeout, after which your thread will be resumed even if the
process is completely busy.

=item Coro::AnyEvent::readable $fh_or_fileno[, $timeout]

=item Coro::AnyEvent::writable $fh_or_fileno[, $timeout]

Blocks the current thread until the given file handle (or file descriptor)
becomes readable (or writable), or the given timeout has elapsed,
whichever happens first. No timeout counts as infinite timeout.

Returns true when the file handle became ready, false when a timeout
occured.

Note that these functions are quite inefficient as compared to using a
single watcher (they recreate watchers on every invocation) or compared to
using Coro::Handle.

Note also that they only work for sources that have reasonable
non-blocking behaviour (e.g. not files).

Example: wait until STDIN becomes readable, then quit the program.

   use Coro::AnyEvent;
   print "press enter to quit...\n";
   Coro::AnyEvent::readable *STDIN;
   exit 0;

=cut

sub poll() {
   my $w = AE::timer 0, 0, Coro::rouse_cb;
   Coro::rouse_wait;
}

sub sleep($) {
   my $w = AE::timer $_[0], 0, Coro::rouse_cb;
   Coro::rouse_wait;
}

sub idle() {
   my $w = AE::idle Coro::rouse_cb;
   Coro::rouse_wait;
}

sub idle_upto($) {
   my $cb = Coro::rouse_cb;
   my $t = AE::timer shift, 0, $cb;
   my $w = AE::idle $cb;
   Coro::rouse_wait;
}

sub readable($;$) {
   my $cb = Coro::rouse_cb;
   my $w = AE::io $_[0], 0, sub { $cb->(1) };
   my $t = defined $_[1] && AE::timer $_[1], 0, sub { $cb->(0) };
   Coro::rouse_wait
}

sub writable($;$) {
   my $cb = Coro::rouse_cb;
   my $w = AE::io $_[0], 1, sub { $cb->(1) };
   my $t = defined $_[1] && AE::timer $_[1], 0, sub { $cb->(0) };
   Coro::rouse_wait
}

#############################################################################
# override condvars

package Coro::AnyEvent::CondVar;

sub _send {
   (delete $_[0]{_ae_coro})->ready if $_[0]{_ae_coro};
}

sub _wait {
   while (!$_[0]{_ae_sent}) {
      local $_[0]{_ae_coro} = $Coro::current;
      Coro::schedule;
   }
}

1;

=back

=head1 IMPLEMENTATION DETAILS

Unfortunately, few event loops (basically only L<EV> and L<Event>)
support the kind of integration required for smooth operations well, and
consequently, AnyEvent cannot completely offer the functionality required
by this module, so we need to improvise.

Here is what this module does when it has to work with other event loops:

=over 4

=item * run ready threads before blocking the process

Each time a thread is put into the ready queue (and there are no other
threads in the ready queue), a timer with an C<after> value of C<0> is
registered with AnyEvent.

This creates something similar to an I<idle> watcher, i.e. a watcher
that keeps the event loop from blocking but still polls for new
events. (Unfortunately, some badly designed event loops (e.g. Event::Lib)
don't support a timeout of C<0> and will always block for a bit).

The callback for that timer will C<cede> to other threads of the same or
higher priority for as long as such threads exists. This has the effect of
running all threads that have work to do until all threads block to wait
for external events.

If no threads of equal or higher priority are ready, it will cede to any
thread, but only once. This has the effect of running lower-priority
threads as well, but it will not keep higher priority threads from
receiving new events.

The priority used is simply the priority of the thread that runs the event
loop, usually the main program, which usually has a priority of C<0>. Note
that Coro::AnyEvent does I<not> run an event loop for you, so unless the
main program runs one, there will simply be no event loop to C<cede> to
(event handling will still work, somewhat inefficiently, but any thread
will have a higher priority than event handling in that case).

=item * provide a suitable idle callback.

In addition to hooking into C<ready>, this module will also provide a
C<$Coro::idle> handler that runs the event loop. It is best not to take
advantage of this too often, as this is rather inefficient, but it should
work perfectly fine.

=item * provide overrides for AnyEvent's condvars

This module installs overrides for AnyEvent's condvars. That is, when
the module is loaded it will provide its own condition variables. This
makes them coroutine-safe, i.e. you can safely block on them from within a
coroutine.

=item * lead to data corruption or worse

As C<unblock_sub> cannot be used by this module (as it is the module
that implements it, basically), you must not call into the event
loop recursively from any coroutine. This is not usually a difficult
restriction to live with, just use condvars, C<unblock_sub> or other means
of inter-coroutine-communications.

If you use a module that supports AnyEvent (or uses the same event loop
as AnyEvent, making the compatible), and it offers callbacks of any kind,
then you must not block in them, either (or use e.g. C<unblock_sub>), see
the description of C<unblock_sub> in the L<Coro> module.

This also means that you should load the module as early as possible,
as only condvars created after this module has been loaded will work
correctly.

=back

=head1 SEE ALSO

L<AnyEvent>, to see which event loops are supported, L<Coro::EV> and
L<Coro::Event> for more efficient and more correct solutions (they will be
used automatically if applicable).

=head1 AUTHOR

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

=cut

Revision:	1.63
Committed:	Thu Feb 10 08:06:27 2011 UTC (13 years, 4 months ago) by root
Branch:	MAIN
Changes since 1.62:	+1 -1 lines
Log Message:	* empty log message *
#	User	Rev	Content
1	root	1.1	=head1 NAME
2
3	root	1.39	Coro::AnyEvent - integrate threads into AnyEvent
4	root	1.1
5			=head1 SYNOPSIS
6
7			use Coro;
8	root	1.54	use AnyEvent;
9			# using both Coro and AnyEvent will automatically load Coro::AnyEvent
10	root	1.1
11	root	1.62	# or load it manually for it's utility functions:
12			use Coro::AnyEvent;
13
14			Coro::AnyEvent::sleep 5; # block current thread for 5s
15			Coro::AnyEvent::poll; # poll for new events once
16			Coro::AnyEvent::idle; # block until process no longer busy
17			Coro::AnyEvent::idle_upto 5; # same, but only up to 5 seconds
18
19			Coro::AnyEvent::readable $fh, 60
20	root	1.63	or die "fh didn't become readable within 60 seconds\n";
21	root	1.2
22	root	1.39	=head1 DESCRIPTION
23	root	1.2
24	root	1.39	When one naively starts to use threads in Perl, one will quickly run
25			into the problem that threads that block on a syscall (sleeping,
26			reading from a socket etc.) will block all threads.
27	root	1.2
28			If one then uses an event loop, the problem is that the event loop has
29	root	1.39	no knowledge of threads and will not run them before it polls for new
30	root	1.2	events, again blocking the whole process.
31
32	root	1.39	This module integrates threads into any event loop supported by
33	root	1.2	AnyEvent, combining event-based programming with coroutine-based
34			programming in a natural way.
35
36	root	1.54	As of Coro 5.21 and newer, this module gets loaded automatically when
37			AnyEvent initialises itself and Coro is used in the same process, thus
38			there is no need to load it manually if you just want your threads to
39			coexist with AnyEvent.
40
41			If you want to use any functions from this module, you of course still
42			need to C<use Coro::AnyEvent>, just as with other perl modules.
43	root	1.1
44	root	1.55	Also, this module autodetects the event loop used (by relying on
45			L<AnyEvent>) and will either automatically defer to the high-performance
46			L<Coro::EV> or L<Coro::Event> modules, or will use a generic integration
47			method that should work with any event loop supported by L<AnyEvent>.
48
49	root	1.39	=head1 USAGE
50	root	1.1
51	root	1.55	=head2 RUN AN EVENT LOOP - OR NOT?
52
53			For performance reasons, it is recommended that the main program or
54			something else runs the event loop of the event model you use, i.e.
55
56			use Gtk2; # <- the event model
57			use AnyEvent;
58			use Coro:
59
60			# initialise stuff
61			async { ... };
62
63			# now run mainloop of Gtk2
64			main Gtk2;
65
66			You can move the event loop into a thread as well, although this tends to
67			get confusing:
68
69			use Gtk2;
70			use AnyEvent;
71			use Coro:
72
73			async { main Gtk2 };
74
75			# do other things...
76			while () {
77			use Coro::AnyEvent;
78			Coro::AnyEvent::sleep 1;
79			print "ping...\n";
80			}
81
82			You can also do nothing, in which case Coro:AnyEvent will invoke the event
83			loop as needed, which is less efficient, but sometimes very convenient.
84
85			What you I<MUST NOT DO EVER> is to block inside an event loop
86			callback. The reason is that most event loops are not reentrant and this
87			can cause a deadlock at best and corrupt memory at worst.
88
89			Coro will try to catch you when you block in the event loop
90			("FATAL:$Coro::IDLE blocked itself"), but this is just best effort and
91			only works when you do not run your own event loop.
92
93			To avoid this problem, simply do not block inside an event callback
94			- start a new thread (e.g. with C<Coro:async_pool>) or use
95			C<Coro::unblock_sub>.
96
97			=head2 INVERSION OF CONTROL
98	root	1.2
99	root	1.55	If you need to wait for a single event, the rouse functions will come in
100			handy (see the Coro manpage for details):
101	root	1.39
102	root	1.40	# wait for single SIGINT
103			{
104			my $int_w = AnyEvent->signal (signal => "INT", cb => Coro::rouse_cb);
105			Coro::rouse_wait;
106			}
107	root	1.39
108	root	1.54	=head2 EVENT MODULES OTHER THEN ANYEVENT
109
110			Keep in mind that, as shipped, Coro and Coro::AnyEvent only work with
111			AnyEvent, and only when AnyEvent is actually used (i.e. initialised), so
112			this will not work:
113
114	root	1.55	# does not work: EV without AnyEvent is not recognised
115	root	1.54	use EV;
116			use Coro;
117
118			EV::loop;
119
120			And neither does this, unless you actually I<use> AnyEvent for something:
121
122	root	1.55	# does not work: AnyEvent must be initialised (e.g. by creating watchers)
123	root	1.54	use EV;
124			use AnyEvent;
125			use Coro;
126
127			EV::loop;
128
129			This does work, however, because you create a watcher (condvars work,
130			too), thus forcing AnyEvent to initialise itself:
131
132			# does work: AnyEvent is actually used
133			use EV;
134			use AnyEvent;
135			use Coro;
136
137			my $timer = AE::timer 1, 1, sub { };
138
139			EV::loop;
140
141			And if you want to use AnyEvent just to bridge between Coro and your event
142			model of choice, you can simply force it to initialise itself, like this:
143
144			# does work: AnyEvent is initialised manually
145			use POE;
146			use AnyEvent;
147			use Coro;
148
149	root	1.55	AnyEvent::detect; # force AnyEvent to integrate Coro into POE
150	root	1.54	POE::Kernel->run;
151
152	root	1.40	=head1 FUNCTIONS
153	root	1.2
154	root	1.55	Coro::AnyEvent also offers a few functions that might be useful.
155	root	1.2
156	root	1.4	=over 4
157
158	root	1.1	=cut
159
160			package Coro::AnyEvent;
161
162	root	1.52	use common::sense;
163	root	1.1
164			use Coro;
165			use AnyEvent ();
166
167	root	1.61	our $VERSION = 5.25;
168	root	1.1
169	root	1.5	#############################################################################
170			# idle handler
171
172	root	1.9	our $IDLE;
173	root	1.1
174	root	1.5	#############################################################################
175			# 0-timeout idle emulation watcher
176
177	root	1.1	our $ACTIVITY;
178
179			sub _activity {
180	root	1.51	$ACTIVITY \|\|= AE::timer 0, 0, \&_schedule;
181	root	1.1	}
182
183	root	1.14	Coro::_set_readyhook (\&AnyEvent::detect);
184	root	1.8
185			AnyEvent::post_detect {
186	root	1.10	unshift @AnyEvent::CondVar::ISA, "Coro::AnyEvent::CondVar";
187	root	1.5
188	root	1.8	my $model = $AnyEvent::MODEL;
189	root	1.1
190	root	1.40	if ($model eq "AnyEvent::Impl::EV" and eval { require Coro::EV }) {
191	root	1.58	# provide faster versions of some functions
192			Coro::EV::_set_readyhook ();
193	root	1.40
194			eval '
195			*sleep = \&Coro::EV::timer_once;
196	root	1.48	*poll = \&Coro::EV::_poll;
197	root	1.52	*idle = sub() {
198	root	1.40	my $w = EV::idle Coro::rouse_cb;
199			Coro::rouse_wait;
200			};
201	root	1.52	*idle_upto = sub($) {
202	root	1.40	my $cb = Coro::rouse_cb;
203			my $t = EV::timer $_[0], 0, $cb;
204			my $w = EV::idle $cb;
205			Coro::rouse_wait;
206			};
207	root	1.52	*readable = sub($;$) {
208	root	1.40	EV::READ & Coro::EV::timed_io_once $_[0], EV::READ , $_[1]
209			};
210	root	1.52	*writable = sub($;$) {
211	root	1.40	EV::WRITE & Coro::EV::timed_io_once $_[0], EV::WRITE, $_[1]
212			};
213			';
214			die if $@;
215
216			} elsif ($model eq "AnyEvent::Impl::Event" and eval { require Coro::Event }) {
217	root	1.58	Coro::_set_readyhook undef;
218	root	1.40	# let Coro::Event do its thing
219	root	1.1	} else {
220	root	1.40	# do the inefficient thing ourselves
221	root	1.1	Coro::_set_readyhook \&_activity;
222	root	1.9
223			$IDLE = new Coro sub {
224	root	1.32	my $one_event = AnyEvent->can ("one_event");
225	root	1.40
226	root	1.9	while () {
227	root	1.32	$one_event->();
228	root	1.55	Coro::schedule if Coro::nready;
229	root	1.9	}
230			};
231			$IDLE->{desc} = "[AnyEvent idle process]";
232
233	root	1.32	$Coro::idle = $IDLE;
234	root	1.47
235			# call the readyhook, in case coroutines were already readied
236			_activity;
237	root	1.1	}
238	root	1.8	};
239	root	1.5
240	root	1.40	=item Coro::AnyEvent::poll
241
242			This call will block the current thread until the event loop has polled
243			for new events and instructs the event loop to poll for new events once,
244			without blocking.
245
246			Note that this call will not actually execute the poll, just block until
247			new events have been polled, so other threads will have a chance to run.
248
249			This is useful when you have a thread that does some computations, but you
250			still want to poll for new events from time to time. Simply call C<poll>
251			from time to time:
252
253			my $long_calc = async {
254			for (1..10000) {
255			Coro::AnyEvent::poll:
256			# do some stuff, make sure it takes at least 0.001s or so
257			}
258			}
259
260			Although you should also consider C<idle> or C<idle_upto> in such cases.
261
262			=item Coro::AnyEvent::sleep $seconds
263
264			This blocks the current thread for at least the given number of seconds.
265
266			=item Coro::AnyEvent::idle
267
268			This call is similar to C<poll> in that it will also poll for
269			events. Unlike C<poll>, it will only resume the thread once there are no
270			events to handle anymore, i.e. when the process is otherwise idle.
271
272	root	1.56	This is good for background threads that shouldn't use CPU time when
273			foreground jobs are ready to run.
274
275	root	1.40	=item Coro::AnyEvent::idle_upto $seconds
276
277			Like C<idle>, but with a maximum waiting time.
278
279			If your process is busy handling events, calling C<idle> can mean that
280			your thread will never be resumed. To avoid this, you can use C<idle_upto>
281			and specify a timeout, after which your thread will be resumed even if the
282			process is completely busy.
283
284	root	1.44	=item Coro::AnyEvent::readable $fh_or_fileno[, $timeout]
285	root	1.40
286	root	1.44	=item Coro::AnyEvent::writable $fh_or_fileno[, $timeout]
287	root	1.40
288	root	1.44	Blocks the current thread until the given file handle (or file descriptor)
289			becomes readable (or writable), or the given timeout has elapsed,
290			whichever happens first. No timeout counts as infinite timeout.
291	root	1.40
292			Returns true when the file handle became ready, false when a timeout
293			occured.
294
295			Note that these functions are quite inefficient as compared to using a
296			single watcher (they recreate watchers on every invocation) or compared to
297			using Coro::Handle.
298
299			Note also that they only work for sources that have reasonable
300			non-blocking behaviour (e.g. not files).
301
302			Example: wait until STDIN becomes readable, then quit the program.
303
304			use Coro::AnyEvent;
305			print "press enter to quit...\n";
306			Coro::AnyEvent::readable *STDIN;
307			exit 0;
308
309			=cut
310
311			sub poll() {
312	root	1.51	my $w = AE::timer 0, 0, Coro::rouse_cb;
313	root	1.40	Coro::rouse_wait;
314			}
315
316			sub sleep($) {
317	root	1.51	my $w = AE::timer $_[0], 0, Coro::rouse_cb;
318	root	1.40	Coro::rouse_wait;
319			}
320
321			sub idle() {
322	root	1.51	my $w = AE::idle Coro::rouse_cb;
323	root	1.40	Coro::rouse_wait;
324			}
325
326			sub idle_upto($) {
327			my $cb = Coro::rouse_cb;
328	root	1.51	my $t = AE::timer shift, 0, $cb;
329			my $w = AE::idle $cb;
330	root	1.40	Coro::rouse_wait;
331			}
332
333			sub readable($;$) {
334			my $cb = Coro::rouse_cb;
335	root	1.51	my $w = AE::io $_[0], 0, sub { $cb->(1) };
336			my $t = defined $_[1] && AE::timer $_[1], 0, sub { $cb->(0) };
337	root	1.40	Coro::rouse_wait
338			}
339
340			sub writable($;$) {
341			my $cb = Coro::rouse_cb;
342	root	1.51	my $w = AE::io $_[0], 1, sub { $cb->(1) };
343			my $t = defined $_[1] && AE::timer $_[1], 0, sub { $cb->(0) };
344	root	1.40	Coro::rouse_wait
345			}
346
347	root	1.5	#############################################################################
348			# override condvars
349
350	root	1.10	package Coro::AnyEvent::CondVar;
351	root	1.5
352	root	1.10	sub _send {
353			(delete $_[0]{_ae_coro})->ready if $_[0]{_ae_coro};
354	root	1.5	}
355
356	root	1.10	sub _wait {
357			while (!$_[0]{_ae_sent}) {
358			local $_[0]{_ae_coro} = $Coro::current;
359	root	1.5	Coro::schedule;
360			}
361			}
362	root	1.1
363			1;
364
365	root	1.40	=back
366
367			=head1 IMPLEMENTATION DETAILS
368
369			Unfortunately, few event loops (basically only L<EV> and L<Event>)
370			support the kind of integration required for smooth operations well, and
371			consequently, AnyEvent cannot completely offer the functionality required
372			by this module, so we need to improvise.
373
374			Here is what this module does when it has to work with other event loops:
375
376			=over 4
377
378			=item * run ready threads before blocking the process
379
380			Each time a thread is put into the ready queue (and there are no other
381			threads in the ready queue), a timer with an C<after> value of C<0> is
382			registered with AnyEvent.
383
384			This creates something similar to an I<idle> watcher, i.e. a watcher
385			that keeps the event loop from blocking but still polls for new
386			events. (Unfortunately, some badly designed event loops (e.g. Event::Lib)
387			don't support a timeout of C<0> and will always block for a bit).
388
389			The callback for that timer will C<cede> to other threads of the same or
390			higher priority for as long as such threads exists. This has the effect of
391			running all threads that have work to do until all threads block to wait
392			for external events.
393
394			If no threads of equal or higher priority are ready, it will cede to any
395			thread, but only once. This has the effect of running lower-priority
396			threads as well, but it will not keep higher priority threads from
397			receiving new events.
398
399			The priority used is simply the priority of the thread that runs the event
400			loop, usually the main program, which usually has a priority of C<0>. Note
401			that Coro::AnyEvent does I<not> run an event loop for you, so unless the
402			main program runs one, there will simply be no event loop to C<cede> to
403			(event handling will still work, somewhat inefficiently, but any thread
404			will have a higher priority than event handling in that case).
405
406			=item * provide a suitable idle callback.
407
408			In addition to hooking into C<ready>, this module will also provide a
409			C<$Coro::idle> handler that runs the event loop. It is best not to take
410			advantage of this too often, as this is rather inefficient, but it should
411			work perfectly fine.
412
413			=item * provide overrides for AnyEvent's condvars
414
415			This module installs overrides for AnyEvent's condvars. That is, when
416			the module is loaded it will provide its own condition variables. This
417			makes them coroutine-safe, i.e. you can safely block on them from within a
418			coroutine.
419
420			=item * lead to data corruption or worse
421
422			As C<unblock_sub> cannot be used by this module (as it is the module
423			that implements it, basically), you must not call into the event
424			loop recursively from any coroutine. This is not usually a difficult
425			restriction to live with, just use condvars, C<unblock_sub> or other means
426			of inter-coroutine-communications.
427
428			If you use a module that supports AnyEvent (or uses the same event loop
429			as AnyEvent, making the compatible), and it offers callbacks of any kind,
430			then you must not block in them, either (or use e.g. C<unblock_sub>), see
431			the description of C<unblock_sub> in the L<Coro> module.
432
433			This also means that you should load the module as early as possible,
434			as only condvars created after this module has been loaded will work
435			correctly.
436
437			=back
438
439	root	1.3	=head1 SEE ALSO
440
441			L<AnyEvent>, to see which event loops are supported, L<Coro::EV> and
442			L<Coro::Event> for more efficient and more correct solutions (they will be
443			used automatically if applicable).
444
445	root	1.1	=head1 AUTHOR
446
447			Marc Lehmann <schmorp@schmorp.de>
448			http://home.schmorp.de/
449
450			=cut
451