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 = 0.13;

@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:	1.28
Committed:	Fri Aug 10 21:03:40 2001 UTC (22 years, 9 months ago) by root
Branch:	MAIN
Changes since 1.27:	+13 -3 lines
Log Message:	* empty log message *
#	Content
1	=head1 NAME
2
3	Coro - coroutine process abstraction
4
5	=head1 SYNOPSIS
6
7	use Coro;
8
9	async {
10	# some asynchronous thread of execution
11	};
12
13	# alternatively create an async process like this:
14
15	sub some_func : Coro {
16	# some more async code
17	}
18
19	cede;
20
21	=head1 DESCRIPTION
22
23	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	In this module, coroutines are defined as "callchain + lexical variables
29	+ @_ + $_ + $@ + $^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
33	=cut
34
35	package Coro;
36
37	use Coro::State;
38
39	use base Exporter;
40
41	$VERSION = 0.13;
42
43	@EXPORT = qw(async cede schedule terminate current);
44	@EXPORT_OK = qw($current);
45
46	{
47	my @async;
48	my $init;
49
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, $ref;
60	unless ($init++) {
61	eval q{
62	sub INIT {
63	&async(pop @async) while @async;
64	}
65	};
66	}
67	} else {
68	push @attrs, $_;
69	}
70	}
71	return $old ? $old->($package, $ref, @attrs) : @attrs;
72	};
73	}
74
75	}
76
77	=item $main
78
79	This coroutine represents the main program.
80
81	=cut
82
83	our $main = new Coro;
84
85	=item $current (or as function: current)
86
87	The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course).
88
89	=cut
90
91	# maybe some other module used Coro::Specific before...
92	if ($current) {
93	$main->{specific} = $current->{specific};
94	}
95
96	our $current = $main;
97
98	sub current() { $current }
99
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
113	# 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	# we really need priorities...
124	my @ready; # the ready queue. hehe, rather broken ;)
125
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	=item async { ... } [@args...]
135
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	# 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	=cut
149
150	sub async(&@) {
151	my $pid = new Coro @_;
152	$manager->ready; # this ensures that the stack is cloned from the manager
153	$pid->ready;
154	$pid;
155	}
156
157	=item schedule
158
159	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
163	=cut
164
165	my $prev;
166
167	sub schedule {
168	# should be done using priorities :(
169	($prev, $current) = ($current, shift @ready \|\| $idle);
170	Coro::State::transfer($prev, $current);
171	}
172
173	=item cede
174
175	"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
179	=cut
180
181	sub cede {
182	$current->ready;
183	&schedule;
184	}
185
186	=item terminate
187
188	Terminates the current process.
189
190	Future versions of this function will allow result arguments.
191
192	=cut
193
194	sub terminate {
195	$current->cancel;
196	&schedule;
197	die; # NORETURN
198	}
199
200	=back
201
202	# dynamic methods
203
204	=head2 PROCESS METHODS
205
206	These are the methods you can call on process objects.
207
208	=over 4
209
210	=item new Coro \&sub [, @args...]
211
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
216	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	=cut
220
221	sub _newcoro {
222	terminate &{+shift};
223	}
224
225	sub new {
226	my $class = shift;
227	bless {
228	_coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
229	}, $class;
230	}
231
232	=item $process->ready
233
234	Put the current process into the ready queue.
235
236	=cut
237
238	sub ready {
239	push @ready, $_[0];
240	}
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	}
252
253	=back
254
255	=cut
256
257	1;
258
259	=head1 BUGS/LIMITATIONS
260
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	- 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	allow per-thread schedulers, but Coro::State does not yet allow this).
272
273	=head1 SEE ALSO
274
275	L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>,
276	L<Coro::Signal>, L<Coro::State>, L<Coro::Event>, L<Coro::RWLock>,
277	L<Coro::Handle>, L<Coro::Socket>.
278
279	=head1 AUTHOR
280
281	Marc Lehmann <pcg@goof.com>
282	http://www.goof.com/pcg/marc/
283
284	=cut
285