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 = 0.12;

@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);
};

# 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 {
   push @destroy, $current;
   $manager->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>, L<Coro::RWLock>,
L<Coro::L<Coro::Handle>, L<Coro::Socket>.

=head1 AUTHOR

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

=cut

Revision:	1.25
Committed:	Wed Jul 25 21:12:57 2001 UTC (22 years, 10 months ago) by root
Branch:	MAIN
Changes since 1.24:	+2 -1 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	$VERSION = 0.12;
42
43	@EXPORT = qw(async cede schedule terminate current);
44	@EXPORT_OK = qw($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	push @attrs, $_;
61	}
62	}
63	return $old ? $old->($package, $ref, @attrs) : @attrs;
64	};
65	}
66
67	sub INIT {
68	&async(pop @async) while @async;
69	}
70	}
71
72	=item $main
73
74	This coroutine represents the main program.
75
76	=cut
77
78	our $main = new Coro;
79
80	=item $current (or as function: current)
81
82	The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course).
83
84	=cut
85
86	# maybe some other module used Coro::Specific before...
87	if ($current) {
88	$main->{specific} = $current->{specific};
89	}
90
91	our $current = $main;
92
93	sub current() { $current }
94
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
108	# this coroutine is necessary because a coroutine
109	# cannot destroy itself.
110	my @destroy;
111	my $manager = new Coro sub {
112	while() {
113	delete ((pop @destroy)->{_coro_state}) while @destroy;
114	&schedule;
115	}
116	};
117
118	# we really need priorities...
119	my @ready; # the ready queue. hehe, rather broken ;)
120
121	# static methods. not really.
122
123	=head2 STATIC METHODS
124
125	Static methods are actually functions that operate on the current process only.
126
127	=over 4
128
129	=item async { ... } [@args...]
130
131	Create a new asynchronous process and return it's process object
132	(usually unused). When the sub returns the new process is automatically
133	terminated.
134
135	# create a new coroutine that just prints its arguments
136	async {
137	print "@_\n";
138	} 1,2,3,4;
139
140	The coderef you submit MUST NOT be a closure that refers to variables
141	in an outer scope. This does NOT work. Pass arguments into it instead.
142
143	=cut
144
145	sub async(&@) {
146	my $pid = new Coro @_;
147	$manager->ready; # this ensures that the stack is cloned from the manager
148	$pid->ready;
149	$pid;
150	}
151
152	=item schedule
153
154	Calls the scheduler. Please note that the current process will not be put
155	into the ready queue, so calling this function usually means you will
156	never be called again.
157
158	=cut
159
160	my $prev;
161
162	sub schedule {
163	# should be done using priorities :(
164	($prev, $current) = ($current, shift @ready \|\| $idle);
165	Coro::State::transfer($prev, $current);
166	}
167
168	=item cede
169
170	"Cede" to other processes. This function puts the current process into the
171	ready queue and calls C<schedule>, which has the effect of giving up the
172	current "timeslice" to other coroutines of the same or higher priority.
173
174	=cut
175
176	sub cede {
177	$current->ready;
178	&schedule;
179	}
180
181	=item terminate
182
183	Terminates the current process.
184
185	Future versions of this function will allow result arguments.
186
187	=cut
188
189	sub terminate {
190	push @destroy, $current;
191	$manager->ready;
192	&schedule;
193	# NORETURN
194	}
195
196	=back
197
198	# dynamic methods
199
200	=head2 PROCESS METHODS
201
202	These are the methods you can call on process objects.
203
204	=over 4
205
206	=item new Coro \&sub [, @args...]
207
208	Create a new process and return it. When the sub returns the process
209	automatically terminates. To start the process you must first put it into
210	the ready queue by calling the ready method.
211
212	The coderef you submit MUST NOT be a closure that refers to variables
213	in an outer scope. This does NOT work. Pass arguments into it instead.
214
215	=cut
216
217	sub _newcoro {
218	terminate &{+shift};
219	}
220
221	sub new {
222	my $class = shift;
223	bless {
224	_coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
225	}, $class;
226	}
227
228	=item $process->ready
229
230	Put the current process into the ready queue.
231
232	=cut
233
234	sub ready {
235	push @ready, $_[0];
236	}
237
238	=back
239
240	=cut
241
242	1;
243
244	=head1 BUGS/LIMITATIONS
245
246	- could be faster, especially when the core would introduce special
247	support for coroutines (like it does for threads).
248	- there is still a memleak on coroutine termination that I could not
249	identify. Could be as small as a single SV.
250	- this module is not well-tested.
251	- if variables or arguments "disappear" (become undef) or become
252	corrupted please contact the author so he cen iron out the
253	remaining bugs.
254	- this module is not thread-safe. You must only ever use this module from
255	the same thread (this requirement might be loosened in the future to
256	allow per-thread schedulers, but Coro::State does not yet allow this).
257
258	=head1 SEE ALSO
259
260	L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>,
261	L<Coro::Signal>, L<Coro::State>, L<Coro::Event>, L<Coro::RWLock>,
262	L<Coro::L<Coro::Handle>, L<Coro::Socket>.
263
264	=head1 AUTHOR
265
266	Marc Lehmann <pcg@goof.com>
267	http://www.goof.com/pcg/marc/
268
269	=cut
270