Coro/Coro.pm

=head1 NAME

Coro - coroutine process abstraction

=head1 SYNOPSIS

 use Coro;

 async {
    # some asynchronous thread of execution
 };

 # alternatively create an async coroutine like this:

 sub some_func : Coro {
    # some more async code
 }

 cede;

=head1 DESCRIPTION

This module collection manages coroutines. Coroutines are similar
to threads but don't run in parallel at the same time even on SMP
machines. The specific flavor of coroutine use din this module also
guarentees you that it will not switch between coroutines unless
necessary, at easily-identified points in your program, so locking and
parallel access are rarely an issue, making coroutine programming much
safer than threads programming.

(Perl, however, does not natively support real threads but instead does a
very slow and memory-intensive emulation of processes using threads. This
is a performance win on Windows machines, and a loss everywhere else).

In this module, coroutines are defined as "callchain + lexical variables +
@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,
its own set of lexicals and its own set of perls most important global
variables.

=cut

package Coro;

use strict;
no warnings "uninitialized";

use Coro::State;

use base qw(Coro::State Exporter);

our $idle;    # idle handler
our $main;    # main coroutine
our $current; # current coroutine

our $VERSION = '3.3';

our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
our %EXPORT_TAGS = (
      prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
);
our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));

{
   my @async;
   my $init;

   # this way of handling attributes simply is NOT scalable ;()
   sub import {
      no strict 'refs';

      Coro->export_to_level (1, @_);

      my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
      *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
         my ($package, $ref) = (shift, shift);
         my @attrs;
         for (@_) {
            if ($_ eq "Coro") {
               push @async, $ref;
               unless ($init++) {
                  eval q{
                     sub INIT {
                        &async(pop @async) while @async;
                     }
                  };
               }
            } else {
               push @attrs, $_;
            }
         }
         return $old ? $old->($package, $ref, @attrs) : @attrs;
      };
   }

}

=over 4

=item $main

This coroutine represents the main program.

=cut

$main = new Coro;

=item $current (or as function: current)

The current coroutine (the last coroutine switched to). The initial value
is C<$main> (of course).

This variable is B<strictly> I<read-only>. It is provided for performance
reasons. If performance is not essentiel you are encouraged to use the
C<Coro::current> function instead.

=cut

# maybe some other module used Coro::Specific before...
$main->{specific} = $current->{specific}
   if $current;

_set_current $main;

sub current() { $current }

=item $idle

A callback that is called whenever the scheduler finds no ready coroutines
to run. The default implementation prints "FATAL: deadlock detected" and
exits, because the program has no other way to continue.

This hook is overwritten by modules such as C<Coro::Timer> and
C<Coro::Event> to wait on an external event that hopefully wake up a
coroutine so the scheduler can run it.

Please note that if your callback recursively invokes perl (e.g. for event
handlers), then it must be prepared to be called recursively.

=cut

$idle = sub {
   require Carp;
   Carp::croak ("FATAL: deadlock detected");
};

sub _cancel {
   my ($self) = @_;

   # free coroutine data and mark as destructed
   $self->_destroy
      or return;

   # call all destruction callbacks
   $_->(@{$self->{status}})
      for @{(delete $self->{destroy_cb}) || []};
}

# this coroutine is necessary because a coroutine
# cannot destroy itself.
my @destroy;
my $manager;

$manager = new Coro sub {
   while () {
      (shift @destroy)->_cancel
         while @destroy;

      &schedule;
   }
};

$manager->prio (PRIO_MAX);

# static methods. not really.

=back

=head2 STATIC METHODS

Static methods are actually functions that operate on the current coroutine only.

=over 4

=item async { ... } [@args...]

Create a new asynchronous coroutine and return it's coroutine object
(usually unused). When the sub returns the new coroutine is automatically
terminated.

Calling C<exit> in a coroutine will not work correctly, so do not do that.

When the coroutine dies, the program will exit, just as in the main
program.

   # create a new coroutine that just prints its arguments
   async {
      print "@_\n";
   } 1,2,3,4;

=cut

sub async(&@) {
   my $coro = new Coro @_;
   $coro->ready;
   $coro
}

=item async_pool { ... } [@args...]

Similar to C<async>, but uses a coroutine pool, so you should not call
terminate or join (although you are allowed to), and you get a coroutine
that might have executed other code already (which can be good or bad :).

Also, the block is executed in an C<eval> context and a warning will be
issued in case of an exception instead of terminating the program, as C<async> does.

The priority will be reset to C<0> after each job, otherwise the coroutine
will be re-used "as-is".

The pool size is limited to 8 idle coroutines (this can be adjusted by
changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
required.

If you are concerned about pooled coroutines growing a lot because a
single C<async_pool> used a lot of stackspace you can e.g. C<async_pool {
terminate }> once per second or so to slowly replenish the pool.

=cut

our $POOL_SIZE = 8;
our @pool;

sub pool_handler {
   while () {
      my ($cb, @arg) = @{ delete $current->{_invoke} };

      eval {
         $cb->(@arg);
      };
      warn $@ if $@;

      last if @pool >= $POOL_SIZE;
      push @pool, $current;

      $current->prio (0);
      schedule;
   }        
}           

sub async_pool(&@) {
   # this is also inlined into the unlock_scheduler
   my $coro = (pop @pool or new Coro \&pool_handler);

   $coro->{_invoke} = [@_];
   $coro->ready;

   $coro
}

=item schedule

Calls the scheduler. Please note that the current coroutine will not be put
into the ready queue, so calling this function usually means you will
never be called again unless something else (e.g. an event handler) calls
ready.

The canonical way to wait on external events is this:

   {
      # remember current coroutine
      my $current = $Coro::current;

      # register a hypothetical event handler
      on_event_invoke sub {
         # wake up sleeping coroutine
         $current->ready;
         undef $current;
      };

      # call schedule until event occured.
      # in case we are woken up for other reasons
      # (current still defined), loop.
      Coro::schedule while $current;
   }

=item cede

"Cede" to other coroutines. This function puts the current coroutine into the
ready queue and calls C<schedule>, which has the effect of giving up the
current "timeslice" to other coroutines of the same or higher priority.

=item Coro::cede_notself

Works like cede, but is not exported by default and will cede to any
coroutine, regardless of priority, once.

=item terminate [arg...]

Terminates the current coroutine with the given status values (see L<cancel>).

=cut

sub terminate {
   $current->cancel (@_);
}

=back

# dynamic methods

=head2 COROUTINE METHODS

These are the methods you can call on coroutine objects.

=over 4

=item new Coro \&sub [, @args...]

Create a new coroutine and return it. When the sub returns the coroutine
automatically terminates as if C<terminate> with the returned values were
called. To make the coroutine run you must first put it into the ready queue
by calling the ready method.

Calling C<exit> in a coroutine will not work correctly, so do not do that.

=cut

sub _run_coro {
   terminate &{+shift};
}

sub new {
   my $class = shift;

   $class->SUPER::new (\&_run_coro, @_)
}

=item $success = $coroutine->ready

Put the given coroutine into the ready queue (according to it's priority)
and return true. If the coroutine is already in the ready queue, do nothing
and return false.

=item $is_ready = $coroutine->is_ready

Return wether the coroutine is currently the ready queue or not,

=item $coroutine->cancel (arg...)

Terminates the given coroutine and makes it return the given arguments as
status (default: the empty list). Never returns if the coroutine is the
current coroutine.

=cut

sub cancel {
   my $self = shift;
   $self->{status} = [@_];

   if ($current == $self) {
      push @destroy, $self;
      $manager->ready;
      &schedule while 1;
   } else {
      $self->_cancel;
   }
}

=item $coroutine->join

Wait until the coroutine terminates and return any values given to the
C<terminate> or C<cancel> functions. C<join> can be called multiple times
from multiple coroutine.

=cut

sub join {
   my $self = shift;

   unless ($self->{status}) {
      my $current = $current;

      push @{$self->{destroy_cb}}, sub {
         $current->ready;
         undef $current;
      };

      &schedule while $current;
   }

   wantarray ? @{$self->{status}} : $self->{status}[0];
}

=item $coroutine->on_destroy (\&cb)

Registers a callback that is called when this coroutine gets destroyed,
but before it is joined. The callback gets passed the terminate arguments,
if any.

=cut

sub on_destroy {
   my ($self, $cb) = @_;

   push @{ $self->{destroy_cb} }, $cb;
}

=item $oldprio = $coroutine->prio ($newprio)

Sets (or gets, if the argument is missing) the priority of the
coroutine. Higher priority coroutines get run before lower priority
coroutines. Priorities are small signed integers (currently -4 .. +3),
that you can refer to using PRIO_xxx constants (use the import tag :prio
to get then):

   PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
       3    >     1     >      0      >    -1    >    -3     >    -4

   # set priority to HIGH
   current->prio(PRIO_HIGH);

The idle coroutine ($Coro::idle) always has a lower priority than any
existing coroutine.

Changing the priority of the current coroutine will take effect immediately,
but changing the priority of coroutines in the ready queue (but not
running) will only take effect after the next schedule (of that
coroutine). This is a bug that will be fixed in some future version.

=item $newprio = $coroutine->nice ($change)

Similar to C<prio>, but subtract the given value from the priority (i.e.
higher values mean lower priority, just as in unix).

=item $olddesc = $coroutine->desc ($newdesc)

Sets (or gets in case the argument is missing) the description for this
coroutine. This is just a free-form string you can associate with a coroutine.

=cut

sub desc {
   my $old = $_[0]{desc};
   $_[0]{desc} = $_[1] if @_ > 1;
   $old;
}

=back

=head2 GLOBAL FUNCTIONS

=over 4

=item Coro::nready

Returns the number of coroutines that are currently in the ready state,
i.e. that can be swicthed to. The value C<0> means that the only runnable
coroutine is the currently running one, so C<cede> would have no effect,
and C<schedule> would cause a deadlock unless there is an idle handler
that wakes up some coroutines.

=item my $guard = Coro::guard { ... }

This creates and returns a guard object. Nothing happens until the objetc
gets destroyed, in which case the codeblock given as argument will be
executed. This is useful to free locks or other resources in case of a
runtime error or when the coroutine gets canceled, as in both cases the
guard block will be executed. The guard object supports only one method,
C<< ->cancel >>, which will keep the codeblock from being executed.

Example: set some flag and clear it again when the coroutine gets canceled
or the function returns:

   sub do_something {
      my $guard = Coro::guard { $busy = 0 };
      $busy = 1;

      # do something that requires $busy to be true
   }

=cut

sub guard(&) {
   bless \(my $cb = $_[0]), "Coro::guard"
}

sub Coro::guard::cancel {
   ${$_[0]} = sub { };
}

sub Coro::guard::DESTROY {
   ${$_[0]}->();
}


=item unblock_sub { ... }

This utility function takes a BLOCK or code reference and "unblocks" it,
returning the new coderef. This means that the new coderef will return
immediately without blocking, returning nothing, while the original code
ref will be called (with parameters) from within its own coroutine.

The reason this fucntion exists is that many event libraries (such as the
venerable L<Event|Event> module) are not coroutine-safe (a weaker form
of thread-safety). This means you must not block within event callbacks,
otherwise you might suffer from crashes or worse.

This function allows your callbacks to block by executing them in another
coroutine where it is safe to block. One example where blocking is handy
is when you use the L<Coro::AIO|Coro::AIO> functions to save results to
disk.

In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
creating event callbacks that want to block.

=cut

our @unblock_queue;

# we create a special coro because we want to cede,
# to reduce pressure on the coro pool (because most callbacks
# return immediately and can be reused) and because we cannot cede
# inside an event callback.
our $unblock_scheduler = async {
   while () {
      while (my $cb = pop @unblock_queue) {
         # this is an inlined copy of async_pool
         my $coro = (pop @pool or new Coro \&pool_handler);

         $coro->{_invoke} = $cb;
         $coro->ready;
         cede; # for short-lived callbacks, this reduces pressure on the coro pool
      }
      schedule; # sleep well
   }
};

sub unblock_sub(&) {
   my $cb = shift;

   sub {
      unshift @unblock_queue, [$cb, @_];
      $unblock_scheduler->ready;
   }
}

=back

=cut

1;

=head1 BUGS/LIMITATIONS

 - you must make very sure that no coro is still active on global
   destruction. very bad things might happen otherwise (usually segfaults).

 - this module is not thread-safe. You should only ever use this module
   from the same thread (this requirement might be losened in the future
   to allow per-thread schedulers, but Coro::State does not yet allow
   this).

=head1 SEE ALSO

Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.

Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.

Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.

Embedding: L<Coro:MakeMaker>

=head1 AUTHOR

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

=cut

Revision:	1.105
Committed:	Fri Jan 5 16:55:01 2007 UTC (17 years, 5 months ago) by root
Branch:	MAIN
Changes since 1.104:	+65 -21 lines
Log Message:	coro pool
#	User	Rev	Content
1	root	1.1	=head1 NAME
2
3	root	1.8	Coro - coroutine process abstraction
4	root	1.1
5			=head1 SYNOPSIS
6
7			use Coro;
8
9	root	1.8	async {
10			# some asynchronous thread of execution
11	root	1.2	};
12
13	root	1.92	# alternatively create an async coroutine like this:
14	root	1.6
15	root	1.8	sub some_func : Coro {
16			# some more async code
17			}
18
19	root	1.22	cede;
20	root	1.2
21	root	1.1	=head1 DESCRIPTION
22
23	root	1.98	This module collection manages coroutines. Coroutines are similar
24			to threads but don't run in parallel at the same time even on SMP
25			machines. The specific flavor of coroutine use din this module also
26			guarentees you that it will not switch between coroutines unless
27			necessary, at easily-identified points in your program, so locking and
28			parallel access are rarely an issue, making coroutine programming much
29			safer than threads programming.
30
31			(Perl, however, does not natively support real threads but instead does a
32			very slow and memory-intensive emulation of processes using threads. This
33			is a performance win on Windows machines, and a loss everywhere else).
34
35			In this module, coroutines are defined as "callchain + lexical variables +
36			@_ + $_ + $@ + $/ + C stack), that is, a coroutine has its own callchain,
37			its own set of lexicals and its own set of perls most important global
38			variables.
39	root	1.22
40	root	1.8	=cut
41
42			package Coro;
43
44	root	1.71	use strict;
45			no warnings "uninitialized";
46	root	1.36
47	root	1.8	use Coro::State;
48
49	root	1.83	use base qw(Coro::State Exporter);
50	pcg	1.55
51	root	1.83	our $idle; # idle handler
52	root	1.71	our $main; # main coroutine
53			our $current; # current coroutine
54	root	1.8
55	root	1.101	our $VERSION = '3.3';
56	root	1.8
57	root	1.105	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
58	root	1.71	our %EXPORT_TAGS = (
59	root	1.31	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
60			);
61	root	1.97	our @EXPORT_OK = (@{$EXPORT_TAGS{prio}}, qw(nready));
62	root	1.8
63			{
64			my @async;
65	root	1.26	my $init;
66	root	1.8
67			# this way of handling attributes simply is NOT scalable ;()
68			sub import {
69	root	1.71	no strict 'refs';
70
71	root	1.93	Coro->export_to_level (1, @_);
72	root	1.71
73	root	1.8	my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
74			*{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
75			my ($package, $ref) = (shift, shift);
76			my @attrs;
77			for (@_) {
78			if ($_ eq "Coro") {
79			push @async, $ref;
80	root	1.26	unless ($init++) {
81			eval q{
82			sub INIT {
83			&async(pop @async) while @async;
84			}
85			};
86			}
87	root	1.8	} else {
88	root	1.17	push @attrs, $_;
89	root	1.8	}
90			}
91	root	1.17	return $old ? $old->($package, $ref, @attrs) : @attrs;
92	root	1.8	};
93			}
94
95			}
96
97	root	1.43	=over 4
98
99	root	1.8	=item $main
100	root	1.2
101	root	1.8	This coroutine represents the main program.
102	root	1.1
103			=cut
104
105	pcg	1.55	$main = new Coro;
106	root	1.8
107	root	1.19	=item $current (or as function: current)
108	root	1.1
109	root	1.83	The current coroutine (the last coroutine switched to). The initial value
110			is C<$main> (of course).
111
112			This variable is B<strictly> I<read-only>. It is provided for performance
113			reasons. If performance is not essentiel you are encouraged to use the
114			C<Coro::current> function instead.
115	root	1.1
116	root	1.8	=cut
117
118			# maybe some other module used Coro::Specific before...
119	root	1.93	$main->{specific} = $current->{specific}
120			if $current;
121	root	1.1
122	root	1.93	_set_current $main;
123	root	1.19
124			sub current() { $current }
125	root	1.9
126			=item $idle
127
128	root	1.83	A callback that is called whenever the scheduler finds no ready coroutines
129			to run. The default implementation prints "FATAL: deadlock detected" and
130	root	1.91	exits, because the program has no other way to continue.
131	root	1.83
132			This hook is overwritten by modules such as C<Coro::Timer> and
133	root	1.91	C<Coro::Event> to wait on an external event that hopefully wake up a
134			coroutine so the scheduler can run it.
135
136			Please note that if your callback recursively invokes perl (e.g. for event
137			handlers), then it must be prepared to be called recursively.
138	root	1.9
139			=cut
140
141	root	1.83	$idle = sub {
142	root	1.96	require Carp;
143			Carp::croak ("FATAL: deadlock detected");
144	root	1.9	};
145	root	1.8
146	root	1.103	sub _cancel {
147			my ($self) = @_;
148
149			# free coroutine data and mark as destructed
150			$self->_destroy
151			or return;
152
153			# call all destruction callbacks
154			$_->(@{$self->{status}})
155			for @{(delete $self->{destroy_cb}) \|\| []};
156			}
157
158	root	1.24	# this coroutine is necessary because a coroutine
159			# cannot destroy itself.
160			my @destroy;
161	root	1.103	my $manager;
162
163			$manager = new Coro sub {
164	pcg	1.57	while () {
165	root	1.103	(shift @destroy)->_cancel
166			while @destroy;
167
168	root	1.24	&schedule;
169			}
170			};
171
172	root	1.103	$manager->prio (PRIO_MAX);
173
174	root	1.8	# static methods. not really.
175	root	1.43
176			=back
177	root	1.8
178			=head2 STATIC METHODS
179
180	root	1.92	Static methods are actually functions that operate on the current coroutine only.
181	root	1.8
182			=over 4
183
184	root	1.13	=item async { ... } [@args...]
185	root	1.8
186	root	1.92	Create a new asynchronous coroutine and return it's coroutine object
187			(usually unused). When the sub returns the new coroutine is automatically
188	root	1.8	terminated.
189
190	root	1.89	Calling C<exit> in a coroutine will not work correctly, so do not do that.
191
192	root	1.79	When the coroutine dies, the program will exit, just as in the main
193			program.
194
195	root	1.13	# create a new coroutine that just prints its arguments
196			async {
197			print "@_\n";
198			} 1,2,3,4;
199
200	root	1.8	=cut
201
202	root	1.13	sub async(&@) {
203	root	1.104	my $coro = new Coro @_;
204			$coro->ready;
205			$coro
206	root	1.8	}
207	root	1.1
208	root	1.105	=item async_pool { ... } [@args...]
209
210			Similar to C<async>, but uses a coroutine pool, so you should not call
211			terminate or join (although you are allowed to), and you get a coroutine
212			that might have executed other code already (which can be good or bad :).
213
214			Also, the block is executed in an C<eval> context and a warning will be
215			issued in case of an exception instead of terminating the program, as C<async> does.
216
217			The priority will be reset to C<0> after each job, otherwise the coroutine
218			will be re-used "as-is".
219
220			The pool size is limited to 8 idle coroutines (this can be adjusted by
221			changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
222			required.
223
224			If you are concerned about pooled coroutines growing a lot because a
225			single C<async_pool> used a lot of stackspace you can e.g. C<async_pool {
226			terminate }> once per second or so to slowly replenish the pool.
227
228			=cut
229
230			our $POOL_SIZE = 8;
231			our @pool;
232
233			sub pool_handler {
234			while () {
235			my ($cb, @arg) = @{ delete $current->{_invoke} };
236
237			eval {
238			$cb->(@arg);
239			};
240			warn $@ if $@;
241
242			last if @pool >= $POOL_SIZE;
243			push @pool, $current;
244
245			$current->prio (0);
246			schedule;
247			}
248			}
249
250			sub async_pool(&@) {
251			# this is also inlined into the unlock_scheduler
252			my $coro = (pop @pool or new Coro \&pool_handler);
253
254			$coro->{_invoke} = [@_];
255			$coro->ready;
256
257			$coro
258			}
259
260	root	1.8	=item schedule
261	root	1.6
262	root	1.92	Calls the scheduler. Please note that the current coroutine will not be put
263	root	1.8	into the ready queue, so calling this function usually means you will
264	root	1.91	never be called again unless something else (e.g. an event handler) calls
265			ready.
266
267			The canonical way to wait on external events is this:
268
269			{
270	root	1.92	# remember current coroutine
271	root	1.91	my $current = $Coro::current;
272
273			# register a hypothetical event handler
274			on_event_invoke sub {
275			# wake up sleeping coroutine
276			$current->ready;
277			undef $current;
278			};
279
280			# call schedule until event occured.
281			# in case we are woken up for other reasons
282			# (current still defined), loop.
283			Coro::schedule while $current;
284			}
285	root	1.1
286	root	1.22	=item cede
287	root	1.1
288	root	1.92	"Cede" to other coroutines. This function puts the current coroutine into the
289	root	1.22	ready queue and calls C<schedule>, which has the effect of giving up the
290			current "timeslice" to other coroutines of the same or higher priority.
291	root	1.7
292	root	1.102	=item Coro::cede_notself
293
294			Works like cede, but is not exported by default and will cede to any
295			coroutine, regardless of priority, once.
296
297	root	1.40	=item terminate [arg...]
298	root	1.7
299	root	1.92	Terminates the current coroutine with the given status values (see L<cancel>).
300	root	1.13
301	root	1.1	=cut
302
303	root	1.8	sub terminate {
304	pcg	1.59	$current->cancel (@_);
305	root	1.1	}
306	root	1.6
307	root	1.8	=back
308
309			# dynamic methods
310
311	root	1.92	=head2 COROUTINE METHODS
312	root	1.8
313	root	1.92	These are the methods you can call on coroutine objects.
314	root	1.6
315	root	1.8	=over 4
316
317	root	1.13	=item new Coro \&sub [, @args...]
318	root	1.8
319	root	1.92	Create a new coroutine and return it. When the sub returns the coroutine
320	root	1.40	automatically terminates as if C<terminate> with the returned values were
321	root	1.92	called. To make the coroutine run you must first put it into the ready queue
322	root	1.41	by calling the ready method.
323	root	1.13
324	root	1.89	Calling C<exit> in a coroutine will not work correctly, so do not do that.
325
326	root	1.6	=cut
327
328	root	1.94	sub _run_coro {
329	root	1.13	terminate &{+shift};
330			}
331
332	root	1.8	sub new {
333			my $class = shift;
334	root	1.83
335	root	1.94	$class->SUPER::new (\&_run_coro, @_)
336	root	1.8	}
337	root	1.6
338	root	1.92	=item $success = $coroutine->ready
339	root	1.1
340	root	1.92	Put the given coroutine into the ready queue (according to it's priority)
341			and return true. If the coroutine is already in the ready queue, do nothing
342	root	1.90	and return false.
343	root	1.1
344	root	1.92	=item $is_ready = $coroutine->is_ready
345	root	1.90
346	root	1.92	Return wether the coroutine is currently the ready queue or not,
347	root	1.28
348	root	1.92	=item $coroutine->cancel (arg...)
349	root	1.28
350	root	1.92	Terminates the given coroutine and makes it return the given arguments as
351	root	1.103	status (default: the empty list). Never returns if the coroutine is the
352			current coroutine.
353	root	1.28
354			=cut
355
356			sub cancel {
357	pcg	1.59	my $self = shift;
358			$self->{status} = [@_];
359	root	1.103
360			if ($current == $self) {
361			push @destroy, $self;
362			$manager->ready;
363			&schedule while 1;
364			} else {
365			$self->_cancel;
366			}
367	root	1.40	}
368
369	root	1.92	=item $coroutine->join
370	root	1.40
371			Wait until the coroutine terminates and return any values given to the
372	pcg	1.59	C<terminate> or C<cancel> functions. C<join> can be called multiple times
373	root	1.92	from multiple coroutine.
374	root	1.40
375			=cut
376
377			sub join {
378			my $self = shift;
379	root	1.103
380	root	1.40	unless ($self->{status}) {
381	root	1.103	my $current = $current;
382
383			push @{$self->{destroy_cb}}, sub {
384			$current->ready;
385			undef $current;
386			};
387
388			&schedule while $current;
389	root	1.40	}
390	root	1.103
391	root	1.40	wantarray ? @{$self->{status}} : $self->{status}[0];
392	root	1.31	}
393
394	root	1.101	=item $coroutine->on_destroy (\&cb)
395
396			Registers a callback that is called when this coroutine gets destroyed,
397			but before it is joined. The callback gets passed the terminate arguments,
398			if any.
399
400			=cut
401
402			sub on_destroy {
403			my ($self, $cb) = @_;
404
405			push @{ $self->{destroy_cb} }, $cb;
406			}
407
408	root	1.92	=item $oldprio = $coroutine->prio ($newprio)
409	root	1.31
410	root	1.41	Sets (or gets, if the argument is missing) the priority of the
411	root	1.92	coroutine. Higher priority coroutines get run before lower priority
412			coroutines. Priorities are small signed integers (currently -4 .. +3),
413	root	1.41	that you can refer to using PRIO_xxx constants (use the import tag :prio
414			to get then):
415	root	1.31
416			PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
417			3 > 1 > 0 > -1 > -3 > -4
418
419			# set priority to HIGH
420			current->prio(PRIO_HIGH);
421
422			The idle coroutine ($Coro::idle) always has a lower priority than any
423			existing coroutine.
424
425	root	1.92	Changing the priority of the current coroutine will take effect immediately,
426			but changing the priority of coroutines in the ready queue (but not
427	root	1.31	running) will only take effect after the next schedule (of that
428	root	1.92	coroutine). This is a bug that will be fixed in some future version.
429	root	1.31
430	root	1.92	=item $newprio = $coroutine->nice ($change)
431	root	1.31
432			Similar to C<prio>, but subtract the given value from the priority (i.e.
433			higher values mean lower priority, just as in unix).
434
435	root	1.92	=item $olddesc = $coroutine->desc ($newdesc)
436	root	1.41
437			Sets (or gets in case the argument is missing) the description for this
438	root	1.92	coroutine. This is just a free-form string you can associate with a coroutine.
439	root	1.41
440			=cut
441
442			sub desc {
443			my $old = $_[0]{desc};
444			$_[0]{desc} = $_[1] if @_ > 1;
445			$old;
446	root	1.8	}
447	root	1.1
448	root	1.8	=back
449	root	1.2
450	root	1.97	=head2 GLOBAL FUNCTIONS
451	root	1.92
452			=over 4
453
454	root	1.97	=item Coro::nready
455
456			Returns the number of coroutines that are currently in the ready state,
457			i.e. that can be swicthed to. The value C<0> means that the only runnable
458			coroutine is the currently running one, so C<cede> would have no effect,
459			and C<schedule> would cause a deadlock unless there is an idle handler
460			that wakes up some coroutines.
461
462	root	1.103	=item my $guard = Coro::guard { ... }
463
464			This creates and returns a guard object. Nothing happens until the objetc
465			gets destroyed, in which case the codeblock given as argument will be
466			executed. This is useful to free locks or other resources in case of a
467			runtime error or when the coroutine gets canceled, as in both cases the
468			guard block will be executed. The guard object supports only one method,
469			C<< ->cancel >>, which will keep the codeblock from being executed.
470
471			Example: set some flag and clear it again when the coroutine gets canceled
472			or the function returns:
473
474			sub do_something {
475			my $guard = Coro::guard { $busy = 0 };
476			$busy = 1;
477
478			# do something that requires $busy to be true
479			}
480
481			=cut
482
483			sub guard(&) {
484			bless \(my $cb = $_[0]), "Coro::guard"
485			}
486
487			sub Coro::guard::cancel {
488			${$_[0]} = sub { };
489			}
490
491			sub Coro::guard::DESTROY {
492			${$_[0]}->();
493			}
494
495
496	root	1.92	=item unblock_sub { ... }
497
498			This utility function takes a BLOCK or code reference and "unblocks" it,
499			returning the new coderef. This means that the new coderef will return
500			immediately without blocking, returning nothing, while the original code
501			ref will be called (with parameters) from within its own coroutine.
502
503			The reason this fucntion exists is that many event libraries (such as the
504			venerable L<Event\|Event> module) are not coroutine-safe (a weaker form
505			of thread-safety). This means you must not block within event callbacks,
506			otherwise you might suffer from crashes or worse.
507
508			This function allows your callbacks to block by executing them in another
509			coroutine where it is safe to block. One example where blocking is handy
510			is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
511			disk.
512
513			In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
514			creating event callbacks that want to block.
515
516			=cut
517
518			our @unblock_queue;
519
520	root	1.105	# we create a special coro because we want to cede,
521			# to reduce pressure on the coro pool (because most callbacks
522			# return immediately and can be reused) and because we cannot cede
523			# inside an event callback.
524	root	1.92	our $unblock_scheduler = async {
525			while () {
526			while (my $cb = pop @unblock_queue) {
527	root	1.105	# this is an inlined copy of async_pool
528			my $coro = (pop @pool or new Coro \&pool_handler);
529
530			$coro->{_invoke} = $cb;
531			$coro->ready;
532			cede; # for short-lived callbacks, this reduces pressure on the coro pool
533	root	1.92	}
534	root	1.105	schedule; # sleep well
535	root	1.92	}
536			};
537
538			sub unblock_sub(&) {
539			my $cb = shift;
540
541			sub {
542	root	1.105	unshift @unblock_queue, [$cb, @_];
543	root	1.92	$unblock_scheduler->ready;
544			}
545			}
546
547			=back
548
549	root	1.8	=cut
550	root	1.2
551	root	1.8	1;
552	root	1.14
553	root	1.17	=head1 BUGS/LIMITATIONS
554	root	1.14
555	root	1.52	- you must make very sure that no coro is still active on global
556	root	1.53	destruction. very bad things might happen otherwise (usually segfaults).
557	root	1.52
558			- this module is not thread-safe. You should only ever use this module
559			from the same thread (this requirement might be losened in the future
560			to allow per-thread schedulers, but Coro::State does not yet allow
561			this).
562	root	1.9
563			=head1 SEE ALSO
564
565	root	1.67	Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.
566
567			Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
568
569			Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
570
571			Embedding: L<Coro:MakeMaker>
572	root	1.1
573			=head1 AUTHOR
574
575	root	1.66	Marc Lehmann <schmorp@schmorp.de>
576	root	1.64	http://home.schmorp.de/
577	root	1.1
578			=cut
579