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 = 0.10;

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

{
   my @async;

   # 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;
            } else {
               push @attrs, $_;
            }
         }
         return $old ? $old->($package, $ref, @attrs) : @attrs;
      };
   }

   sub INIT {
      &async(pop @async) while @async;
   }
}

=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);
};

# 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 @_;
   $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

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

sub terminate {
   push @destroy, $current;
   $terminate->ready;
   &schedule;
   # 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];
}

=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>.

=head1 AUTHOR

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

=cut

Revision:	1.23
Committed:	Mon Jul 23 04:23:32 2001 UTC (22 years, 10 months ago) by root
Branch:	MAIN
Changes since 1.22:	+17 -25 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	1.20	$VERSION = 0.10;
42	root	1.8
43	root	1.22	@EXPORT = qw(async cede schedule terminate current);
44	root	1.8	@EXPORT_OK = qw($current);
45
46			{
47			my @async;
48
49			# this way of handling attributes simply is NOT scalable ;()
50			sub import {
51			Coro->export_to_level(1, @_);
52			my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
53			*{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
54			my ($package, $ref) = (shift, shift);
55			my @attrs;
56			for (@_) {
57			if ($_ eq "Coro") {
58			push @async, $ref;
59			} else {
60	root	1.17	push @attrs, $_;
61	root	1.8	}
62			}
63	root	1.17	return $old ? $old->($package, $ref, @attrs) : @attrs;
64	root	1.8	};
65			}
66
67			sub INIT {
68	root	1.20	&async(pop @async) while @async;
69	root	1.8	}
70			}
71
72			=item $main
73	root	1.2
74	root	1.8	This coroutine represents the main program.
75	root	1.1
76			=cut
77
78	root	1.9	our $main = new Coro;
79	root	1.8
80	root	1.19	=item $current (or as function: current)
81	root	1.1
82	root	1.8	The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course).
83	root	1.1
84	root	1.8	=cut
85
86			# maybe some other module used Coro::Specific before...
87			if ($current) {
88			$main->{specific} = $current->{specific};
89	root	1.1	}
90
91	root	1.9	our $current = $main;
92	root	1.19
93			sub current() { $current }
94	root	1.9
95			=item $idle
96
97			The coroutine to switch to when no other coroutine is running. The default
98			implementation prints "FATAL: deadlock detected" and exits.
99
100			=cut
101
102			# should be done using priorities :(
103			our $idle = new Coro sub {
104			print STDERR "FATAL: deadlock detected\n";
105			exit(51);
106			};
107	root	1.8
108			# we really need priorities...
109	root	1.16	my @ready; # the ready queue. hehe, rather broken ;)
110	root	1.8
111			# static methods. not really.
112
113			=head2 STATIC METHODS
114
115			Static methods are actually functions that operate on the current process only.
116
117			=over 4
118
119	root	1.13	=item async { ... } [@args...]
120	root	1.8
121			Create a new asynchronous process and return it's process object
122			(usually unused). When the sub returns the new process is automatically
123			terminated.
124
125	root	1.13	# create a new coroutine that just prints its arguments
126			async {
127			print "@_\n";
128			} 1,2,3,4;
129
130			The coderef you submit MUST NOT be a closure that refers to variables
131			in an outer scope. This does NOT work. Pass arguments into it instead.
132
133	root	1.8	=cut
134
135	root	1.13	sub async(&@) {
136			my $pid = new Coro @_;
137	root	1.11	$pid->ready;
138			$pid;
139	root	1.8	}
140	root	1.1
141	root	1.8	=item schedule
142	root	1.6
143	root	1.8	Calls the scheduler. Please note that the current process will not be put
144			into the ready queue, so calling this function usually means you will
145			never be called again.
146	root	1.1
147			=cut
148
149	root	1.8	my $prev;
150
151			sub schedule {
152	root	1.9	# should be done using priorities :(
153			($prev, $current) = ($current, shift @ready \|\| $idle);
154	root	1.8	Coro::State::transfer($prev, $current);
155	root	1.1	}
156
157	root	1.22	=item cede
158	root	1.1
159	root	1.22	"Cede" to other processes. This function puts the current process into the
160			ready queue and calls C<schedule>, which has the effect of giving up the
161			current "timeslice" to other coroutines of the same or higher priority.
162	root	1.7
163	root	1.8	=cut
164
165	root	1.22	sub cede {
166	root	1.8	$current->ready;
167			&schedule;
168			}
169	root	1.7
170	root	1.8	=item terminate
171	root	1.7
172	root	1.8	Terminates the current process.
173	root	1.1
174	root	1.13	Future versions of this function will allow result arguments.
175
176	root	1.1	=cut
177
178	root	1.23	# this coroutine is necessary because a coroutine
179			# cannot destroy itself.
180			my @destroy;
181			my $terminate = new Coro sub {
182			while() {
183			delete ((pop @destroy)->{_coro_state}) while @destroy;
184			&schedule;
185			}
186			};
187
188	root	1.8	sub terminate {
189	root	1.23	push @destroy, $current;
190			$terminate->ready;
191			&schedule;
192			# NORETURN
193	root	1.1	}
194	root	1.6
195	root	1.8	=back
196
197			# dynamic methods
198
199			=head2 PROCESS METHODS
200
201			These are the methods you can call on process objects.
202	root	1.6
203	root	1.8	=over 4
204
205	root	1.13	=item new Coro \&sub [, @args...]
206	root	1.8
207			Create a new process and return it. When the sub returns the process
208			automatically terminates. To start the process you must first put it into
209			the ready queue by calling the ready method.
210	root	1.6
211	root	1.13	The coderef you submit MUST NOT be a closure that refers to variables
212			in an outer scope. This does NOT work. Pass arguments into it instead.
213
214	root	1.6	=cut
215
216	root	1.13	sub _newcoro {
217			terminate &{+shift};
218			}
219
220	root	1.8	sub new {
221			my $class = shift;
222			bless {
223	root	1.13	_coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
224	root	1.8	}, $class;
225			}
226	root	1.6
227	root	1.8	=item $process->ready
228	root	1.1
229	root	1.8	Put the current process into the ready queue.
230	root	1.1
231	root	1.8	=cut
232	root	1.1
233	root	1.8	sub ready {
234			push @ready, $_[0];
235			}
236	root	1.1
237	root	1.8	=back
238	root	1.2
239	root	1.8	=cut
240	root	1.2
241	root	1.8	1;
242	root	1.14
243	root	1.17	=head1 BUGS/LIMITATIONS
244	root	1.14
245			- could be faster, especially when the core would introduce special
246			support for coroutines (like it does for threads).
247			- there is still a memleak on coroutine termination that I could not
248			identify. Could be as small as a single SV.
249			- this module is not well-tested.
250	root	1.17	- if variables or arguments "disappear" (become undef) or become
251			corrupted please contact the author so he cen iron out the
252			remaining bugs.
253			- this module is not thread-safe. You must only ever use this module from
254			the same thread (this requirement might be loosened in the future to
255	root	1.20	allow per-thread schedulers, but Coro::State does not yet allow this).
256	root	1.9
257			=head1 SEE ALSO
258
259			L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>,
260	root	1.10	L<Coro::Signal>, L<Coro::State>, L<Coro::Event>.
261	root	1.1
262			=head1 AUTHOR
263
264			Marc Lehmann <pcg@goof.com>
265			http://www.goof.com/pcg/marc/
266
267			=cut
268