Coro/Coro.pm

=head1 NAME

Coro - coroutine process abstraction

=head1 SYNOPSIS

 use Coro;

 async {
    # some asynchronous thread of execution
 };

 # alternatively create an async process 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.

This module is still experimental, see the BUGS section below.

In this module, coroutines are defined as "callchain + lexical variables
+ @_ + $_ + $@ + $^W + C stack), that is, a coroutine has it's own
callchain, it's own set of lexicals and it's own set of perl's most
important global variables.

=cut

package Coro;

use Coro::State;

use base Exporter;

$VERSION = 0.45;

@EXPORT = qw(async cede schedule terminate current);
@EXPORT_OK = qw($current);

{
   my @async;
   my $init;

   # this way of handling attributes simply is NOT scalable ;()
   sub import {
      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;
      };
   }

}

=item $main

This coroutine represents the main program.

=cut

our $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).

=cut

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

our $current = $main;

sub current() { $current }

=item $idle

The coroutine to switch to when no other coroutine is running. The default
implementation prints "FATAL: deadlock detected" and exits.

=cut

# should be done using priorities :(
our $idle = new Coro sub {
   print STDERR "FATAL: deadlock detected\n";
   exit(51);
};

# this coroutine is necessary because a coroutine
# cannot destroy itself.
my @destroy;
my $manager = new Coro sub {
   while() {
      delete ((pop @destroy)->{_coro_state}) while @destroy;
      &schedule;
   }
};

# we really need priorities...
my @ready; # the ready queue. hehe, rather broken ;)

# static methods. not really.

=head2 STATIC METHODS

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

=over 4

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

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

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

The coderef you submit MUST NOT be a closure that refers to variables
in an outer scope. This does NOT work. Pass arguments into it instead.

=cut

sub async(&@) {
   my $pid = new Coro @_;
   $manager->ready; # this ensures that the stack is cloned from the manager
   $pid->ready;
   $pid;
}

=item schedule

Calls the scheduler. Please note that the current process will not be put
into the ready queue, so calling this function usually means you will
never be called again.

=cut

my $prev;

sub schedule {
   # should be done using priorities :(
   ($prev, $current) = ($current, shift @ready || $idle);
   Coro::State::transfer($prev, $current);
}

=item cede

"Cede" to other processes. This function puts the current process 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.

=cut

sub cede {
   $current->ready;
   &schedule;
}

=item terminate

Terminates the current process.

Future versions of this function will allow result arguments.

=cut

sub terminate {
   $current->cancel;
   &schedule;
   die; # NORETURN
}

=back

# dynamic methods

=head2 PROCESS METHODS

These are the methods you can call on process objects.

=over 4

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

Create a new process and return it. When the sub returns the process
automatically terminates. To start the process you must first put it into
the ready queue by calling the ready method.

The coderef you submit MUST NOT be a closure that refers to variables
in an outer scope. This does NOT work. Pass arguments into it instead.

=cut

sub _newcoro {
   terminate &{+shift};
}

sub new {
   my $class = shift;
   bless {
      _coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
   }, $class;
}

=item $process->ready

Put the current process into the ready queue.

=cut

sub ready {
   push @ready, $_[0];
}

=item $process->cancel

Like C<terminate>, but terminates the specified process instead.

=cut

sub cancel {
   push @destroy, $_[0];
   $manager->ready;
}

=back

=cut

1;

=head1 BUGS/LIMITATIONS

 - could be faster, especially when the core would introduce special
   support for coroutines (like it does for threads).
 - there is still a memleak on coroutine termination that I could not
   identify. Could be as small as a single SV.
 - this module is not well-tested.
 - if variables or arguments "disappear" (become undef) or become
   corrupted please contact the author so he cen iron out the
   remaining bugs.
 - this module is not thread-safe. You must 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

L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>,
L<Coro::Signal>, L<Coro::State>, L<Coro::Event>, L<Coro::RWLock>,
L<Coro::Handle>, L<Coro::Socket>.

=head1 AUTHOR

 Marc Lehmann <pcg@goof.com>
 http://www.goof.com/pcg/marc/

=cut

Revision:	1.29
Committed:	Sat Aug 11 00:37:31 2001 UTC (22 years, 9 months ago) by root
Branch:	MAIN
Changes since 1.28:	+1 -1 lines
Log Message:	* empty log message *
#	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	1.8	# alternatively create an async process 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	1.14	This module collection manages coroutines. Coroutines are similar to
24			Threads but don't run in parallel.
25
26			This module is still experimental, see the BUGS section below.
27
28	root	1.20	In this module, coroutines are defined as "callchain + lexical variables
29	root	1.23	+ @_ + $_ + $@ + $^W + C stack), that is, a coroutine has it's own
30			callchain, it's own set of lexicals and it's own set of perl's most
31			important global variables.
32	root	1.22
33	root	1.8	=cut
34
35			package Coro;
36
37			use Coro::State;
38
39			use base Exporter;
40
41	root	1.29	$VERSION = 0.45;
42	root	1.8
43	root	1.22	@EXPORT = qw(async cede schedule terminate current);
44	root	1.8	@EXPORT_OK = qw($current);
45
46			{
47			my @async;
48	root	1.26	my $init;
49	root	1.8
50			# this way of handling attributes simply is NOT scalable ;()
51			sub import {
52			Coro->export_to_level(1, @_);
53			my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
54			*{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
55			my ($package, $ref) = (shift, shift);
56			my @attrs;
57			for (@_) {
58			if ($_ eq "Coro") {
59			push @async, $ref;
60	root	1.26	unless ($init++) {
61			eval q{
62			sub INIT {
63			&async(pop @async) while @async;
64			}
65			};
66			}
67	root	1.8	} else {
68	root	1.17	push @attrs, $_;
69	root	1.8	}
70			}
71	root	1.17	return $old ? $old->($package, $ref, @attrs) : @attrs;
72	root	1.8	};
73			}
74
75			}
76
77			=item $main
78	root	1.2
79	root	1.8	This coroutine represents the main program.
80	root	1.1
81			=cut
82
83	root	1.9	our $main = new Coro;
84	root	1.8
85	root	1.19	=item $current (or as function: current)
86	root	1.1
87	root	1.8	The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course).
88	root	1.1
89	root	1.8	=cut
90
91			# maybe some other module used Coro::Specific before...
92			if ($current) {
93			$main->{specific} = $current->{specific};
94	root	1.1	}
95
96	root	1.9	our $current = $main;
97	root	1.19
98			sub current() { $current }
99	root	1.9
100			=item $idle
101
102			The coroutine to switch to when no other coroutine is running. The default
103			implementation prints "FATAL: deadlock detected" and exits.
104
105			=cut
106
107			# should be done using priorities :(
108			our $idle = new Coro sub {
109			print STDERR "FATAL: deadlock detected\n";
110			exit(51);
111			};
112	root	1.8
113	root	1.24	# this coroutine is necessary because a coroutine
114			# cannot destroy itself.
115			my @destroy;
116			my $manager = new Coro sub {
117			while() {
118			delete ((pop @destroy)->{_coro_state}) while @destroy;
119			&schedule;
120			}
121			};
122
123	root	1.8	# we really need priorities...
124	root	1.16	my @ready; # the ready queue. hehe, rather broken ;)
125	root	1.8
126			# static methods. not really.
127
128			=head2 STATIC METHODS
129
130			Static methods are actually functions that operate on the current process only.
131
132			=over 4
133
134	root	1.13	=item async { ... } [@args...]
135	root	1.8
136			Create a new asynchronous process and return it's process object
137			(usually unused). When the sub returns the new process is automatically
138			terminated.
139
140	root	1.13	# create a new coroutine that just prints its arguments
141			async {
142			print "@_\n";
143			} 1,2,3,4;
144
145			The coderef you submit MUST NOT be a closure that refers to variables
146			in an outer scope. This does NOT work. Pass arguments into it instead.
147
148	root	1.8	=cut
149
150	root	1.13	sub async(&@) {
151			my $pid = new Coro @_;
152	root	1.24	$manager->ready; # this ensures that the stack is cloned from the manager
153	root	1.11	$pid->ready;
154			$pid;
155	root	1.8	}
156	root	1.1
157	root	1.8	=item schedule
158	root	1.6
159	root	1.8	Calls the scheduler. Please note that the current process will not be put
160			into the ready queue, so calling this function usually means you will
161			never be called again.
162	root	1.1
163			=cut
164
165	root	1.8	my $prev;
166
167			sub schedule {
168	root	1.9	# should be done using priorities :(
169			($prev, $current) = ($current, shift @ready \|\| $idle);
170	root	1.8	Coro::State::transfer($prev, $current);
171	root	1.1	}
172
173	root	1.22	=item cede
174	root	1.1
175	root	1.22	"Cede" to other processes. This function puts the current process into the
176			ready queue and calls C<schedule>, which has the effect of giving up the
177			current "timeslice" to other coroutines of the same or higher priority.
178	root	1.7
179	root	1.8	=cut
180
181	root	1.22	sub cede {
182	root	1.8	$current->ready;
183			&schedule;
184			}
185	root	1.7
186	root	1.8	=item terminate
187	root	1.7
188	root	1.8	Terminates the current process.
189	root	1.1
190	root	1.13	Future versions of this function will allow result arguments.
191
192	root	1.1	=cut
193
194	root	1.8	sub terminate {
195	root	1.28	$current->cancel;
196	root	1.23	&schedule;
197	root	1.28	die; # NORETURN
198	root	1.1	}
199	root	1.6
200	root	1.8	=back
201
202			# dynamic methods
203
204			=head2 PROCESS METHODS
205
206			These are the methods you can call on process objects.
207	root	1.6
208	root	1.8	=over 4
209
210	root	1.13	=item new Coro \&sub [, @args...]
211	root	1.8
212			Create a new process and return it. When the sub returns the process
213			automatically terminates. To start the process you must first put it into
214			the ready queue by calling the ready method.
215	root	1.6
216	root	1.13	The coderef you submit MUST NOT be a closure that refers to variables
217			in an outer scope. This does NOT work. Pass arguments into it instead.
218
219	root	1.6	=cut
220
221	root	1.13	sub _newcoro {
222			terminate &{+shift};
223			}
224
225	root	1.8	sub new {
226			my $class = shift;
227			bless {
228	root	1.13	_coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
229	root	1.8	}, $class;
230			}
231	root	1.6
232	root	1.8	=item $process->ready
233	root	1.1
234	root	1.8	Put the current process into the ready queue.
235	root	1.1
236	root	1.8	=cut
237	root	1.1
238	root	1.8	sub ready {
239			push @ready, $_[0];
240	root	1.28	}
241
242			=item $process->cancel
243
244			Like C<terminate>, but terminates the specified process instead.
245
246			=cut
247
248			sub cancel {
249			push @destroy, $_[0];
250			$manager->ready;
251	root	1.8	}
252	root	1.1
253	root	1.8	=back
254	root	1.2
255	root	1.8	=cut
256	root	1.2
257	root	1.8	1;
258	root	1.14
259	root	1.17	=head1 BUGS/LIMITATIONS
260	root	1.14
261			- could be faster, especially when the core would introduce special
262			support for coroutines (like it does for threads).
263			- there is still a memleak on coroutine termination that I could not
264			identify. Could be as small as a single SV.
265			- this module is not well-tested.
266	root	1.17	- if variables or arguments "disappear" (become undef) or become
267			corrupted please contact the author so he cen iron out the
268			remaining bugs.
269			- this module is not thread-safe. You must only ever use this module from
270			the same thread (this requirement might be loosened in the future to
271	root	1.20	allow per-thread schedulers, but Coro::State does not yet allow this).
272	root	1.9
273			=head1 SEE ALSO
274
275			L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>,
276	root	1.25	L<Coro::Signal>, L<Coro::State>, L<Coro::Event>, L<Coro::RWLock>,
277	root	1.26	L<Coro::Handle>, L<Coro::Socket>.
278	root	1.1
279			=head1 AUTHOR
280
281			Marc Lehmann <pcg@goof.com>
282			http://www.goof.com/pcg/marc/
283
284			=cut
285