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), 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.

WARNING: When using this module, make sure that, at program end, no
coroutines are still running OR just call exit before falling off the
end. The reason for this is that some coroutine of yours might have called
into a C function, and falling off the end of main:: results in returning
to that C function instead if to the main C interpreter.

WARNING: Unless you really know what you are doing, do NOT do context
switches inside callbacks from the XS level. The reason for this is
similar to the reason above:  A callback calls a perl function, this
perl function does a context switch, some other callback is called, the
original function returns from it - to what? To the wrong XS function,
with totally different return values. Unfortunately, this includes
callbacks done by perl itself (tie'd variables!).

The only workaround for this is to do coroutines on C level.

=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

sub terminate {
   my $self = $current;
   $self->{_results} = [@_];
   $current = shift @ready || $idle;
   Coro::State::transfer(delete $self->{_coro_state}, $current);
   # cannot return
   die;
}

=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:	1.22
Committed:	Mon Jul 23 02:14:19 2001 UTC (22 years, 10 months ago) by root
Branch:	MAIN
Changes since 1.21:	+23 -9 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), that is, a coroutine has it's own callchain, it's
30	own set of lexicals and it's own set of perl's most important global
31	variables.
32
33	WARNING: When using this module, make sure that, at program end, no
34	coroutines are still running OR just call exit before falling off the
35	end. The reason for this is that some coroutine of yours might have called
36	into a C function, and falling off the end of main:: results in returning
37	to that C function instead if to the main C interpreter.
38
39	WARNING: Unless you really know what you are doing, do NOT do context
40	switches inside callbacks from the XS level. The reason for this is
41	similar to the reason above: A callback calls a perl function, this
42	perl function does a context switch, some other callback is called, the
43	original function returns from it - to what? To the wrong XS function,
44	with totally different return values. Unfortunately, this includes
45	callbacks done by perl itself (tie'd variables!).
46
47	The only workaround for this is to do coroutines on C level.
48
49	=cut
50
51	package Coro;
52
53	use Coro::State;
54
55	use base Exporter;
56
57	$VERSION = 0.10;
58
59	@EXPORT = qw(async cede schedule terminate current);
60	@EXPORT_OK = qw($current);
61
62	{
63	my @async;
64
65	# this way of handling attributes simply is NOT scalable ;()
66	sub import {
67	Coro->export_to_level(1, @_);
68	my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
69	*{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
70	my ($package, $ref) = (shift, shift);
71	my @attrs;
72	for (@_) {
73	if ($_ eq "Coro") {
74	push @async, $ref;
75	} else {
76	push @attrs, $_;
77	}
78	}
79	return $old ? $old->($package, $ref, @attrs) : @attrs;
80	};
81	}
82
83	sub INIT {
84	&async(pop @async) while @async;
85	}
86	}
87
88	=item $main
89
90	This coroutine represents the main program.
91
92	=cut
93
94	our $main = new Coro;
95
96	=item $current (or as function: current)
97
98	The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course).
99
100	=cut
101
102	# maybe some other module used Coro::Specific before...
103	if ($current) {
104	$main->{specific} = $current->{specific};
105	}
106
107	our $current = $main;
108
109	sub current() { $current }
110
111	=item $idle
112
113	The coroutine to switch to when no other coroutine is running. The default
114	implementation prints "FATAL: deadlock detected" and exits.
115
116	=cut
117
118	# should be done using priorities :(
119	our $idle = new Coro sub {
120	print STDERR "FATAL: deadlock detected\n";
121	exit(51);
122	};
123
124	# we really need priorities...
125	my @ready; # the ready queue. hehe, rather broken ;)
126
127	# static methods. not really.
128
129	=head2 STATIC METHODS
130
131	Static methods are actually functions that operate on the current process only.
132
133	=over 4
134
135	=item async { ... } [@args...]
136
137	Create a new asynchronous process and return it's process object
138	(usually unused). When the sub returns the new process is automatically
139	terminated.
140
141	# create a new coroutine that just prints its arguments
142	async {
143	print "@_\n";
144	} 1,2,3,4;
145
146	The coderef you submit MUST NOT be a closure that refers to variables
147	in an outer scope. This does NOT work. Pass arguments into it instead.
148
149	=cut
150
151	sub async(&@) {
152	my $pid = new Coro @_;
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	my $self = $current;
196	$self->{_results} = [@_];
197	$current = shift @ready \|\| $idle;
198	Coro::State::transfer(delete $self->{_coro_state}, $current);
199	# cannot return
200	die;
201	}
202
203	=back
204
205	# dynamic methods
206
207	=head2 PROCESS METHODS
208
209	These are the methods you can call on process objects.
210
211	=over 4
212
213	=item new Coro \&sub [, @args...]
214
215	Create a new process and return it. When the sub returns the process
216	automatically terminates. To start the process you must first put it into
217	the ready queue by calling the ready method.
218
219	The coderef you submit MUST NOT be a closure that refers to variables
220	in an outer scope. This does NOT work. Pass arguments into it instead.
221
222	=cut
223
224	sub _newcoro {
225	terminate &{+shift};
226	}
227
228	sub new {
229	my $class = shift;
230	bless {
231	_coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
232	}, $class;
233	}
234
235	=item $process->ready
236
237	Put the current process into the ready queue.
238
239	=cut
240
241	sub ready {
242	push @ready, $_[0];
243	}
244
245	=back
246
247	=cut
248
249	1;
250
251	=head1 BUGS/LIMITATIONS
252
253	- could be faster, especially when the core would introduce special
254	support for coroutines (like it does for threads).
255	- there is still a memleak on coroutine termination that I could not
256	identify. Could be as small as a single SV.
257	- this module is not well-tested.
258	- if variables or arguments "disappear" (become undef) or become
259	corrupted please contact the author so he cen iron out the
260	remaining bugs.
261	- this module is not thread-safe. You must only ever use this module from
262	the same thread (this requirement might be loosened in the future to
263	allow per-thread schedulers, but Coro::State does not yet allow this).
264
265	=head1 SEE ALSO
266
267	L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>,
268	L<Coro::Signal>, L<Coro::State>, L<Coro::Event>.
269
270	=head1 AUTHOR
271
272	Marc Lehmann <pcg@goof.com>
273	http://www.goof.com/pcg/marc/
274
275	=cut
276