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 used in this module also
guarantees 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 = '3.7';

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 essential 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 do the same as calling exit outside
the coroutine. Likewise, when the coroutine dies, the program will exit,
just as it would 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. As the coroutine is being reused, stuff like C<on_destroy>
will not work in the expected way, unless you call terminate or cancel,
which somehow defeats the purpose of pooling.

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 () {
      eval {
         my ($cb, @arg) = @{ delete $current->{_invoke} or return };
         $cb->(@arg);
      };
      warn $@ if $@;

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

      $current->save (Coro::State::SAVE_DEF);
      $current->prio (0);
      schedule;
   }
}

sub async_pool(&@) {
   # this is also inlined into the unlock_scheduler
   my $coro = (pop @pool) || do {
      my $coro = new Coro \&pool_handler;
      $coro->{desc} = "async_pool";
      $coro
   };

   $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 occurred.
      # 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.

Returns true if at least one coroutine switch has happened.

=item Coro::cede_notself

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

Returns true if at least one coroutine switch has happened.

=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.

See C<async> for additional discussion.

=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 switched 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 object
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 function 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 loosened 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:	1.128
Committed:	Wed Sep 19 21:39:15 2007 UTC (16 years, 8 months ago) by root
Branch:	MAIN
Changes since 1.127:	+6 -2 lines
Log Message:	yeah
#	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	root	1.124	machines. The specific flavor of coroutine used in this module also
26			guarantees you that it will not switch between coroutines unless
27	root	1.98	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	1.128	our $VERSION = '3.7';
56	root	1.8
57	root	1.105	our @EXPORT = qw(async async_pool cede schedule terminate current unblock_sub);
58	root	1.71	our %EXPORT_TAGS = (
59	root	1.31	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
60			);
61	root	1.97	our @EXPORT_OK = (@{$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	root	1.124	reasons. If performance is not essential you are encouraged to use the
114	root	1.83	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	1.122	Calling C<exit> in a coroutine will do the same as calling exit outside
191			the coroutine. Likewise, when the coroutine dies, the program will exit,
192			just as it would in the main program.
193	root	1.79
194	root	1.13	# create a new coroutine that just prints its arguments
195			async {
196			print "@_\n";
197			} 1,2,3,4;
198
199	root	1.8	=cut
200
201	root	1.13	sub async(&@) {
202	root	1.104	my $coro = new Coro @_;
203			$coro->ready;
204			$coro
205	root	1.8	}
206	root	1.1
207	root	1.105	=item async_pool { ... } [@args...]
208
209			Similar to C<async>, but uses a coroutine pool, so you should not call
210			terminate or join (although you are allowed to), and you get a coroutine
211			that might have executed other code already (which can be good or bad :).
212
213			Also, the block is executed in an C<eval> context and a warning will be
214	root	1.108	issued in case of an exception instead of terminating the program, as
215			C<async> does. As the coroutine is being reused, stuff like C<on_destroy>
216			will not work in the expected way, unless you call terminate or cancel,
217			which somehow defeats the purpose of pooling.
218	root	1.105
219			The priority will be reset to C<0> after each job, otherwise the coroutine
220			will be re-used "as-is".
221
222			The pool size is limited to 8 idle coroutines (this can be adjusted by
223			changing $Coro::POOL_SIZE), and there can be as many non-idle coros as
224			required.
225
226			If you are concerned about pooled coroutines growing a lot because a
227			single C<async_pool> used a lot of stackspace you can e.g. C<async_pool {
228			terminate }> once per second or so to slowly replenish the pool.
229
230			=cut
231
232			our $POOL_SIZE = 8;
233			our @pool;
234
235			sub pool_handler {
236			while () {
237			eval {
238	root	1.110	my ($cb, @arg) = @{ delete $current->{_invoke} or return };
239	root	1.105	$cb->(@arg);
240			};
241			warn $@ if $@;
242
243			last if @pool >= $POOL_SIZE;
244			push @pool, $current;
245
246	root	1.118	$current->save (Coro::State::SAVE_DEF);
247	root	1.105	$current->prio (0);
248			schedule;
249	root	1.106	}
250			}
251	root	1.105
252			sub async_pool(&@) {
253			# this is also inlined into the unlock_scheduler
254	root	1.128	my $coro = (pop @pool) \|\| do {
255			my $coro = new Coro \&pool_handler;
256			$coro->{desc} = "async_pool";
257			$coro
258			};
259	root	1.105
260			$coro->{_invoke} = [@_];
261			$coro->ready;
262
263			$coro
264			}
265
266	root	1.8	=item schedule
267	root	1.6
268	root	1.92	Calls the scheduler. Please note that the current coroutine will not be put
269	root	1.8	into the ready queue, so calling this function usually means you will
270	root	1.91	never be called again unless something else (e.g. an event handler) calls
271			ready.
272
273			The canonical way to wait on external events is this:
274
275			{
276	root	1.92	# remember current coroutine
277	root	1.91	my $current = $Coro::current;
278
279			# register a hypothetical event handler
280			on_event_invoke sub {
281			# wake up sleeping coroutine
282			$current->ready;
283			undef $current;
284			};
285
286	root	1.124	# call schedule until event occurred.
287	root	1.91	# in case we are woken up for other reasons
288			# (current still defined), loop.
289			Coro::schedule while $current;
290			}
291	root	1.1
292	root	1.22	=item cede
293	root	1.1
294	root	1.92	"Cede" to other coroutines. This function puts the current coroutine into the
295	root	1.22	ready queue and calls C<schedule>, which has the effect of giving up the
296			current "timeslice" to other coroutines of the same or higher priority.
297	root	1.7
298	root	1.107	Returns true if at least one coroutine switch has happened.
299
300	root	1.102	=item Coro::cede_notself
301
302			Works like cede, but is not exported by default and will cede to any
303			coroutine, regardless of priority, once.
304
305	root	1.107	Returns true if at least one coroutine switch has happened.
306
307	root	1.40	=item terminate [arg...]
308	root	1.7
309	root	1.92	Terminates the current coroutine with the given status values (see L<cancel>).
310	root	1.13
311	root	1.1	=cut
312
313	root	1.8	sub terminate {
314	pcg	1.59	$current->cancel (@_);
315	root	1.1	}
316	root	1.6
317	root	1.8	=back
318
319			# dynamic methods
320
321	root	1.92	=head2 COROUTINE METHODS
322	root	1.8
323	root	1.92	These are the methods you can call on coroutine objects.
324	root	1.6
325	root	1.8	=over 4
326
327	root	1.13	=item new Coro \&sub [, @args...]
328	root	1.8
329	root	1.92	Create a new coroutine and return it. When the sub returns the coroutine
330	root	1.40	automatically terminates as if C<terminate> with the returned values were
331	root	1.92	called. To make the coroutine run you must first put it into the ready queue
332	root	1.41	by calling the ready method.
333	root	1.13
334	root	1.121	See C<async> for additional discussion.
335	root	1.89
336	root	1.6	=cut
337
338	root	1.94	sub _run_coro {
339	root	1.13	terminate &{+shift};
340			}
341
342	root	1.8	sub new {
343			my $class = shift;
344	root	1.83
345	root	1.94	$class->SUPER::new (\&_run_coro, @_)
346	root	1.8	}
347	root	1.6
348	root	1.92	=item $success = $coroutine->ready
349	root	1.1
350	root	1.92	Put the given coroutine into the ready queue (according to it's priority)
351			and return true. If the coroutine is already in the ready queue, do nothing
352	root	1.90	and return false.
353	root	1.1
354	root	1.92	=item $is_ready = $coroutine->is_ready
355	root	1.90
356	root	1.92	Return wether the coroutine is currently the ready queue or not,
357	root	1.28
358	root	1.92	=item $coroutine->cancel (arg...)
359	root	1.28
360	root	1.92	Terminates the given coroutine and makes it return the given arguments as
361	root	1.103	status (default: the empty list). Never returns if the coroutine is the
362			current coroutine.
363	root	1.28
364			=cut
365
366			sub cancel {
367	pcg	1.59	my $self = shift;
368			$self->{status} = [@_];
369	root	1.103
370			if ($current == $self) {
371			push @destroy, $self;
372			$manager->ready;
373			&schedule while 1;
374			} else {
375			$self->_cancel;
376			}
377	root	1.40	}
378
379	root	1.92	=item $coroutine->join
380	root	1.40
381			Wait until the coroutine terminates and return any values given to the
382	pcg	1.59	C<terminate> or C<cancel> functions. C<join> can be called multiple times
383	root	1.92	from multiple coroutine.
384	root	1.40
385			=cut
386
387			sub join {
388			my $self = shift;
389	root	1.103
390	root	1.40	unless ($self->{status}) {
391	root	1.103	my $current = $current;
392
393			push @{$self->{destroy_cb}}, sub {
394			$current->ready;
395			undef $current;
396			};
397
398			&schedule while $current;
399	root	1.40	}
400	root	1.103
401	root	1.40	wantarray ? @{$self->{status}} : $self->{status}[0];
402	root	1.31	}
403
404	root	1.101	=item $coroutine->on_destroy (\&cb)
405
406			Registers a callback that is called when this coroutine gets destroyed,
407			but before it is joined. The callback gets passed the terminate arguments,
408			if any.
409
410			=cut
411
412			sub on_destroy {
413			my ($self, $cb) = @_;
414
415			push @{ $self->{destroy_cb} }, $cb;
416			}
417
418	root	1.92	=item $oldprio = $coroutine->prio ($newprio)
419	root	1.31
420	root	1.41	Sets (or gets, if the argument is missing) the priority of the
421	root	1.92	coroutine. Higher priority coroutines get run before lower priority
422			coroutines. Priorities are small signed integers (currently -4 .. +3),
423	root	1.41	that you can refer to using PRIO_xxx constants (use the import tag :prio
424			to get then):
425	root	1.31
426			PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
427			3 > 1 > 0 > -1 > -3 > -4
428
429			# set priority to HIGH
430			current->prio(PRIO_HIGH);
431
432			The idle coroutine ($Coro::idle) always has a lower priority than any
433			existing coroutine.
434
435	root	1.92	Changing the priority of the current coroutine will take effect immediately,
436			but changing the priority of coroutines in the ready queue (but not
437	root	1.31	running) will only take effect after the next schedule (of that
438	root	1.92	coroutine). This is a bug that will be fixed in some future version.
439	root	1.31
440	root	1.92	=item $newprio = $coroutine->nice ($change)
441	root	1.31
442			Similar to C<prio>, but subtract the given value from the priority (i.e.
443			higher values mean lower priority, just as in unix).
444
445	root	1.92	=item $olddesc = $coroutine->desc ($newdesc)
446	root	1.41
447			Sets (or gets in case the argument is missing) the description for this
448	root	1.92	coroutine. This is just a free-form string you can associate with a coroutine.
449	root	1.41
450			=cut
451
452			sub desc {
453			my $old = $_[0]{desc};
454			$_[0]{desc} = $_[1] if @_ > 1;
455			$old;
456	root	1.8	}
457	root	1.1
458	root	1.8	=back
459	root	1.2
460	root	1.97	=head2 GLOBAL FUNCTIONS
461	root	1.92
462			=over 4
463
464	root	1.97	=item Coro::nready
465
466			Returns the number of coroutines that are currently in the ready state,
467	root	1.124	i.e. that can be switched to. The value C<0> means that the only runnable
468	root	1.97	coroutine is the currently running one, so C<cede> would have no effect,
469			and C<schedule> would cause a deadlock unless there is an idle handler
470			that wakes up some coroutines.
471
472	root	1.103	=item my $guard = Coro::guard { ... }
473
474	root	1.119	This creates and returns a guard object. Nothing happens until the object
475	root	1.103	gets destroyed, in which case the codeblock given as argument will be
476			executed. This is useful to free locks or other resources in case of a
477			runtime error or when the coroutine gets canceled, as in both cases the
478			guard block will be executed. The guard object supports only one method,
479			C<< ->cancel >>, which will keep the codeblock from being executed.
480
481			Example: set some flag and clear it again when the coroutine gets canceled
482			or the function returns:
483
484			sub do_something {
485			my $guard = Coro::guard { $busy = 0 };
486			$busy = 1;
487
488			# do something that requires $busy to be true
489			}
490
491			=cut
492
493			sub guard(&) {
494			bless \(my $cb = $_[0]), "Coro::guard"
495			}
496
497			sub Coro::guard::cancel {
498			${$_[0]} = sub { };
499			}
500
501			sub Coro::guard::DESTROY {
502			${$_[0]}->();
503			}
504
505
506	root	1.92	=item unblock_sub { ... }
507
508			This utility function takes a BLOCK or code reference and "unblocks" it,
509			returning the new coderef. This means that the new coderef will return
510			immediately without blocking, returning nothing, while the original code
511			ref will be called (with parameters) from within its own coroutine.
512
513	root	1.124	The reason this function exists is that many event libraries (such as the
514	root	1.92	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form
515			of thread-safety). This means you must not block within event callbacks,
516			otherwise you might suffer from crashes or worse.
517
518			This function allows your callbacks to block by executing them in another
519			coroutine where it is safe to block. One example where blocking is handy
520			is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
521			disk.
522
523			In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
524			creating event callbacks that want to block.
525
526			=cut
527
528			our @unblock_queue;
529
530	root	1.105	# we create a special coro because we want to cede,
531			# to reduce pressure on the coro pool (because most callbacks
532			# return immediately and can be reused) and because we cannot cede
533			# inside an event callback.
534	root	1.92	our $unblock_scheduler = async {
535			while () {
536			while (my $cb = pop @unblock_queue) {
537	root	1.105	# this is an inlined copy of async_pool
538			my $coro = (pop @pool or new Coro \&pool_handler);
539
540			$coro->{_invoke} = $cb;
541			$coro->ready;
542			cede; # for short-lived callbacks, this reduces pressure on the coro pool
543	root	1.92	}
544	root	1.105	schedule; # sleep well
545	root	1.92	}
546			};
547
548			sub unblock_sub(&) {
549			my $cb = shift;
550
551			sub {
552	root	1.105	unshift @unblock_queue, [$cb, @_];
553	root	1.92	$unblock_scheduler->ready;
554			}
555			}
556
557			=back
558
559	root	1.8	=cut
560	root	1.2
561	root	1.8	1;
562	root	1.14
563	root	1.17	=head1 BUGS/LIMITATIONS
564	root	1.14
565	root	1.52	- you must make very sure that no coro is still active on global
566	root	1.53	destruction. very bad things might happen otherwise (usually segfaults).
567	root	1.52
568			- this module is not thread-safe. You should only ever use this module
569	root	1.124	from the same thread (this requirement might be loosened in the future
570	root	1.52	to allow per-thread schedulers, but Coro::State does not yet allow
571			this).
572	root	1.9
573			=head1 SEE ALSO
574
575	root	1.67	Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.
576
577			Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
578
579			Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
580
581			Embedding: L<Coro:MakeMaker>
582	root	1.1
583			=head1 AUTHOR
584
585	root	1.66	Marc Lehmann <schmorp@schmorp.de>
586	root	1.64	http://home.schmorp.de/
587	root	1.1
588			=cut
589