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.

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;

no warnings qw(uninitialized);

use Coro::State;

use base Exporter;

$VERSION = 0.531;

@EXPORT = qw(async cede schedule terminate current);
%EXPORT_TAGS = (
      prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
);
@EXPORT_OK = @{$EXPORT_TAGS{prio}};

{
   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;
      };
   }

}

=over 4

=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;
$manager = new Coro sub {
   while() {
      # by overwriting the state object with the manager we destroy it
      # while still being able to schedule this coroutine (in case it has
      # been readied multiple times. this is harmless since the manager
      # can be called as many times as neccessary and will always
      # remove itself from the runqueue
      while (@destroy) {
         my $coro = pop @destroy;
         $coro->{status} ||= [];
         $_->ready for @{delete $coro->{join} || []};
         $coro->{_coro_state} = $manager->{_coro_state};
      }
      &schedule;
   }
};

# static methods. not really.

=back

=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 [arg...]

Terminates the current process.

Future versions of this function will allow result arguments.

=cut

sub terminate {
   $current->{status} = [@_];
   $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 as if C<terminate> with the returned values were
called. To make the process run you must first put it into the ready queue
by calling the ready method.

=cut

sub _newcoro {
   terminate &{+shift};
}

sub new {
   my $class = shift;
   bless {
      _coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
   }, $class;
}

=item $process->ready

Put the given 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;
   &schedule if $current == $_[0];
}

=item $process->join

Wait until the coroutine terminates and return any values given to the
C<terminate> function. C<join> can be called multiple times from multiple
processes.

=cut

sub join {
   my $self = shift;
   unless ($self->{status}) {
      push @{$self->{join}}, $current;
      &schedule;
   }
   wantarray ? @{$self->{status}} : $self->{status}[0];
}

=item $oldprio = $process->prio($newprio)

Sets (or gets, if the argument is missing) the priority of the
process. Higher priority processes get run before lower priority
processes. Priorities are smalled signed integer (currently -4 .. +3),
that you can refer to using PRIO_xxx constants (use the import tag :prio
to get then):

   PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
       3    >     1     >      0      >    -1    >    -3     >    -4

   # set priority to HIGH
   current->prio(PRIO_HIGH);

The idle coroutine ($Coro::idle) always has a lower priority than any
existing coroutine.

Changing the priority of the current process will take effect immediately,
but changing the priority of processes in the ready queue (but not
running) will only take effect after the next schedule (of that
process). This is a bug that will be fixed in some future version.

=cut

sub prio {
   my $old = $_[0]{prio};
   $_[0]{prio} = $_[1] if @_ > 1;
   $old;
}

=item $newprio = $process->nice($change)

Similar to C<prio>, but subtract the given value from the priority (i.e.
higher values mean lower priority, just as in unix).

=cut

sub nice {
   $_[0]{prio} -= $_[1];
}

=item $olddesc = $process->desc($newdesc)

Sets (or gets in case the argument is missing) the description for this
process. This is just a free-form string you can associate with a process.

=cut

sub desc {
   my $old = $_[0]{desc};
   $_[0]{desc} = $_[1] if @_ > 1;
   $old;
}

=back

=cut

1;

=head1 BUGS/LIMITATIONS

 - you must make very sure that no coro is still active on global destruction.
   very bad things might happen otherwise (usually segfaults).
 - this module is not thread-safe. You should 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:	1.45
Committed:	Mon Dec 10 21:18:28 2001 UTC (22 years, 5 months ago) by root
Branch:	MAIN
Changes since 1.44:	+1 -1 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	root	1.42	threads but don't run in parallel.
25	root	1.14
26	root	1.20	In this module, coroutines are defined as "callchain + lexical variables
27	root	1.23	+ @_ + $_ + $@ + $^W + C stack), that is, a coroutine has it's own
28			callchain, it's own set of lexicals and it's own set of perl's most
29			important global variables.
30	root	1.22
31	root	1.8	=cut
32
33			package Coro;
34
35	root	1.36	no warnings qw(uninitialized);
36
37	root	1.8	use Coro::State;
38
39			use base Exporter;
40
41	root	1.45	$VERSION = 0.531;
42	root	1.8
43	root	1.22	@EXPORT = qw(async cede schedule terminate current);
44	root	1.31	%EXPORT_TAGS = (
45			prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
46			);
47			@EXPORT_OK = @{$EXPORT_TAGS{prio}};
48	root	1.8
49			{
50			my @async;
51	root	1.26	my $init;
52	root	1.8
53			# this way of handling attributes simply is NOT scalable ;()
54			sub import {
55			Coro->export_to_level(1, @_);
56			my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
57			*{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
58			my ($package, $ref) = (shift, shift);
59			my @attrs;
60			for (@_) {
61			if ($_ eq "Coro") {
62			push @async, $ref;
63	root	1.26	unless ($init++) {
64			eval q{
65			sub INIT {
66			&async(pop @async) while @async;
67			}
68			};
69			}
70	root	1.8	} else {
71	root	1.17	push @attrs, $_;
72	root	1.8	}
73			}
74	root	1.17	return $old ? $old->($package, $ref, @attrs) : @attrs;
75	root	1.8	};
76			}
77
78			}
79
80	root	1.43	=over 4
81
82	root	1.8	=item $main
83	root	1.2
84	root	1.8	This coroutine represents the main program.
85	root	1.1
86			=cut
87
88	root	1.9	our $main = new Coro;
89	root	1.8
90	root	1.19	=item $current (or as function: current)
91	root	1.1
92	root	1.8	The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course).
93	root	1.1
94	root	1.8	=cut
95
96			# maybe some other module used Coro::Specific before...
97			if ($current) {
98			$main->{specific} = $current->{specific};
99	root	1.1	}
100
101	root	1.9	our $current = $main;
102	root	1.19
103			sub current() { $current }
104	root	1.9
105			=item $idle
106
107			The coroutine to switch to when no other coroutine is running. The default
108			implementation prints "FATAL: deadlock detected" and exits.
109
110			=cut
111
112			# should be done using priorities :(
113			our $idle = new Coro sub {
114			print STDERR "FATAL: deadlock detected\n";
115			exit(51);
116			};
117	root	1.8
118	root	1.24	# this coroutine is necessary because a coroutine
119			# cannot destroy itself.
120			my @destroy;
121	root	1.38	my $manager;
122			$manager = new Coro sub {
123	root	1.24	while() {
124	root	1.37	# by overwriting the state object with the manager we destroy it
125			# while still being able to schedule this coroutine (in case it has
126			# been readied multiple times. this is harmless since the manager
127			# can be called as many times as neccessary and will always
128			# remove itself from the runqueue
129	root	1.40	while (@destroy) {
130			my $coro = pop @destroy;
131			$coro->{status} \|\|= [];
132			$_->ready for @{delete $coro->{join} \|\| []};
133			$coro->{_coro_state} = $manager->{_coro_state};
134			}
135	root	1.24	&schedule;
136			}
137			};
138
139	root	1.8	# static methods. not really.
140	root	1.43
141			=back
142	root	1.8
143			=head2 STATIC METHODS
144
145			Static methods are actually functions that operate on the current process only.
146
147			=over 4
148
149	root	1.13	=item async { ... } [@args...]
150	root	1.8
151			Create a new asynchronous process and return it's process object
152			(usually unused). When the sub returns the new process is automatically
153			terminated.
154
155	root	1.13	# create a new coroutine that just prints its arguments
156			async {
157			print "@_\n";
158			} 1,2,3,4;
159
160			The coderef you submit MUST NOT be a closure that refers to variables
161			in an outer scope. This does NOT work. Pass arguments into it instead.
162
163	root	1.8	=cut
164
165	root	1.13	sub async(&@) {
166			my $pid = new Coro @_;
167	root	1.24	$manager->ready; # this ensures that the stack is cloned from the manager
168	root	1.11	$pid->ready;
169			$pid;
170	root	1.8	}
171	root	1.1
172	root	1.8	=item schedule
173	root	1.6
174	root	1.8	Calls the scheduler. Please note that the current process will not be put
175			into the ready queue, so calling this function usually means you will
176			never be called again.
177	root	1.1
178			=cut
179
180	root	1.22	=item cede
181	root	1.1
182	root	1.22	"Cede" to other processes. This function puts the current process into the
183			ready queue and calls C<schedule>, which has the effect of giving up the
184			current "timeslice" to other coroutines of the same or higher priority.
185	root	1.7
186	root	1.8	=cut
187
188	root	1.40	=item terminate [arg...]
189	root	1.7
190	root	1.8	Terminates the current process.
191	root	1.1
192	root	1.13	Future versions of this function will allow result arguments.
193
194	root	1.1	=cut
195
196	root	1.8	sub terminate {
197	root	1.40	$current->{status} = [@_];
198	root	1.28	$current->cancel;
199	root	1.23	&schedule;
200	root	1.28	die; # NORETURN
201	root	1.1	}
202	root	1.6
203	root	1.8	=back
204
205			# dynamic methods
206
207			=head2 PROCESS METHODS
208
209			These are the methods you can call on process objects.
210	root	1.6
211	root	1.8	=over 4
212
213	root	1.13	=item new Coro \&sub [, @args...]
214	root	1.8
215			Create a new process and return it. When the sub returns the process
216	root	1.40	automatically terminates as if C<terminate> with the returned values were
217	root	1.41	called. To make the process run you must first put it into the ready queue
218			by calling the ready method.
219	root	1.13
220	root	1.6	=cut
221
222	root	1.13	sub _newcoro {
223			terminate &{+shift};
224			}
225
226	root	1.8	sub new {
227			my $class = shift;
228			bless {
229	root	1.13	_coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
230	root	1.8	}, $class;
231			}
232	root	1.6
233	root	1.8	=item $process->ready
234	root	1.1
235	root	1.39	Put the given process into the ready queue.
236	root	1.1
237	root	1.8	=cut
238	root	1.28
239			=item $process->cancel
240
241			Like C<terminate>, but terminates the specified process instead.
242
243			=cut
244
245			sub cancel {
246			push @destroy, $_[0];
247			$manager->ready;
248	root	1.35	&schedule if $current == $_[0];
249	root	1.40	}
250
251			=item $process->join
252
253			Wait until the coroutine terminates and return any values given to the
254			C<terminate> function. C<join> can be called multiple times from multiple
255			processes.
256
257			=cut
258
259			sub join {
260			my $self = shift;
261			unless ($self->{status}) {
262			push @{$self->{join}}, $current;
263			&schedule;
264			}
265			wantarray ? @{$self->{status}} : $self->{status}[0];
266	root	1.31	}
267
268			=item $oldprio = $process->prio($newprio)
269
270	root	1.41	Sets (or gets, if the argument is missing) the priority of the
271			process. Higher priority processes get run before lower priority
272			processes. Priorities are smalled signed integer (currently -4 .. +3),
273			that you can refer to using PRIO_xxx constants (use the import tag :prio
274			to get then):
275	root	1.31
276			PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
277			3 > 1 > 0 > -1 > -3 > -4
278
279			# set priority to HIGH
280			current->prio(PRIO_HIGH);
281
282			The idle coroutine ($Coro::idle) always has a lower priority than any
283			existing coroutine.
284
285			Changing the priority of the current process will take effect immediately,
286			but changing the priority of processes in the ready queue (but not
287			running) will only take effect after the next schedule (of that
288			process). This is a bug that will be fixed in some future version.
289
290			=cut
291
292			sub prio {
293			my $old = $_[0]{prio};
294			$_[0]{prio} = $_[1] if @_ > 1;
295			$old;
296			}
297
298			=item $newprio = $process->nice($change)
299
300			Similar to C<prio>, but subtract the given value from the priority (i.e.
301			higher values mean lower priority, just as in unix).
302
303			=cut
304
305			sub nice {
306			$_[0]{prio} -= $_[1];
307	root	1.41	}
308
309			=item $olddesc = $process->desc($newdesc)
310
311			Sets (or gets in case the argument is missing) the description for this
312			process. This is just a free-form string you can associate with a process.
313
314			=cut
315
316			sub desc {
317			my $old = $_[0]{desc};
318			$_[0]{desc} = $_[1] if @_ > 1;
319			$old;
320	root	1.8	}
321	root	1.1
322	root	1.8	=back
323	root	1.2
324	root	1.8	=cut
325	root	1.2
326	root	1.8	1;
327	root	1.14
328	root	1.17	=head1 BUGS/LIMITATIONS
329	root	1.14
330	root	1.33	- you must make very sure that no coro is still active on global destruction.
331			very bad things might happen otherwise (usually segfaults).
332	root	1.42	- this module is not thread-safe. You should only ever use this module from
333	root	1.17	the same thread (this requirement might be loosened in the future to
334	root	1.20	allow per-thread schedulers, but Coro::State does not yet allow this).
335	root	1.9
336			=head1 SEE ALSO
337
338			L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>,
339	root	1.25	L<Coro::Signal>, L<Coro::State>, L<Coro::Event>, L<Coro::RWLock>,
340	root	1.26	L<Coro::Handle>, L<Coro::Socket>.
341	root	1.1
342			=head1 AUTHOR
343
344			Marc Lehmann <pcg@goof.com>
345			http://www.goof.com/pcg/marc/
346
347			=cut
348