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;
   }
};

# 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

=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

=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

=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:	1.30
Committed:	Sat Aug 11 19:59:19 2001 UTC (22 years, 10 months ago) by root
Branch:	MAIN
Changes since 1.29:	+0 -20 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	# static methods. not really.
124
125			=head2 STATIC METHODS
126
127			Static methods are actually functions that operate on the current process only.
128
129			=over 4
130
131	root	1.13	=item async { ... } [@args...]
132	root	1.8
133			Create a new asynchronous process and return it's process object
134			(usually unused). When the sub returns the new process is automatically
135			terminated.
136
137	root	1.13	# create a new coroutine that just prints its arguments
138			async {
139			print "@_\n";
140			} 1,2,3,4;
141
142			The coderef you submit MUST NOT be a closure that refers to variables
143			in an outer scope. This does NOT work. Pass arguments into it instead.
144
145	root	1.8	=cut
146
147	root	1.13	sub async(&@) {
148			my $pid = new Coro @_;
149	root	1.24	$manager->ready; # this ensures that the stack is cloned from the manager
150	root	1.11	$pid->ready;
151			$pid;
152	root	1.8	}
153	root	1.1
154	root	1.8	=item schedule
155	root	1.6
156	root	1.8	Calls the scheduler. Please note that the current process will not be put
157			into the ready queue, so calling this function usually means you will
158			never be called again.
159	root	1.1
160			=cut
161
162	root	1.22	=item cede
163	root	1.1
164	root	1.22	"Cede" to other processes. This function puts the current process into the
165			ready queue and calls C<schedule>, which has the effect of giving up the
166			current "timeslice" to other coroutines of the same or higher priority.
167	root	1.7
168	root	1.8	=cut
169
170			=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	1.8	sub terminate {
179	root	1.28	$current->cancel;
180	root	1.23	&schedule;
181	root	1.28	die; # NORETURN
182	root	1.1	}
183	root	1.6
184	root	1.8	=back
185
186			# dynamic methods
187
188			=head2 PROCESS METHODS
189
190			These are the methods you can call on process objects.
191	root	1.6
192	root	1.8	=over 4
193
194	root	1.13	=item new Coro \&sub [, @args...]
195	root	1.8
196			Create a new process and return it. When the sub returns the process
197			automatically terminates. To start the process you must first put it into
198			the ready queue by calling the ready method.
199	root	1.6
200	root	1.13	The coderef you submit MUST NOT be a closure that refers to variables
201			in an outer scope. This does NOT work. Pass arguments into it instead.
202
203	root	1.6	=cut
204
205	root	1.13	sub _newcoro {
206			terminate &{+shift};
207			}
208
209	root	1.8	sub new {
210			my $class = shift;
211			bless {
212	root	1.13	_coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
213	root	1.8	}, $class;
214			}
215	root	1.6
216	root	1.8	=item $process->ready
217	root	1.1
218	root	1.8	Put the current process into the ready queue.
219	root	1.1
220	root	1.8	=cut
221	root	1.28
222			=item $process->cancel
223
224			Like C<terminate>, but terminates the specified process instead.
225
226			=cut
227
228			sub cancel {
229			push @destroy, $_[0];
230			$manager->ready;
231	root	1.8	}
232	root	1.1
233	root	1.8	=back
234	root	1.2
235	root	1.8	=cut
236	root	1.2
237	root	1.8	1;
238	root	1.14
239	root	1.17	=head1 BUGS/LIMITATIONS
240	root	1.14
241			- could be faster, especially when the core would introduce special
242			support for coroutines (like it does for threads).
243			- there is still a memleak on coroutine termination that I could not
244			identify. Could be as small as a single SV.
245			- this module is not well-tested.
246	root	1.17	- if variables or arguments "disappear" (become undef) or become
247			corrupted please contact the author so he cen iron out the
248			remaining bugs.
249			- this module is not thread-safe. You must only ever use this module from
250			the same thread (this requirement might be loosened in the future to
251	root	1.20	allow per-thread schedulers, but Coro::State does not yet allow this).
252	root	1.9
253			=head1 SEE ALSO
254
255			L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>,
256	root	1.25	L<Coro::Signal>, L<Coro::State>, L<Coro::Event>, L<Coro::RWLock>,
257	root	1.26	L<Coro::Handle>, L<Coro::Socket>.
258	root	1.1
259			=head1 AUTHOR
260
261			Marc Lehmann <pcg@goof.com>
262			http://www.goof.com/pcg/marc/
263
264			=cut
265