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 = 0.52;

@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;
      };
   }

}

=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.

=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:	1.42
Committed:	Tue Nov 6 20:37:20 2001 UTC (22 years, 6 months ago) by root
Branch:	MAIN
Changes since 1.41:	+2 -4 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	1.41	$VERSION = 0.52;
42	root	1.8
43	root	1.22	@EXPORT = qw(async cede schedule terminate current);
44	root	1.31	%EXPORT_TAGS = (
45			prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
46			);
47			@EXPORT_OK = @{$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			=item $main
81	root	1.2
82	root	1.8	This coroutine represents the main program.
83	root	1.1
84			=cut
85
86	root	1.9	our $main = new Coro;
87	root	1.8
88	root	1.19	=item $current (or as function: current)
89	root	1.1
90	root	1.8	The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course).
91	root	1.1
92	root	1.8	=cut
93
94			# maybe some other module used Coro::Specific before...
95			if ($current) {
96			$main->{specific} = $current->{specific};
97	root	1.1	}
98
99	root	1.9	our $current = $main;
100	root	1.19
101			sub current() { $current }
102	root	1.9
103			=item $idle
104
105			The coroutine to switch to when no other coroutine is running. The default
106			implementation prints "FATAL: deadlock detected" and exits.
107
108			=cut
109
110			# should be done using priorities :(
111			our $idle = new Coro sub {
112			print STDERR "FATAL: deadlock detected\n";
113			exit(51);
114			};
115	root	1.8
116	root	1.24	# this coroutine is necessary because a coroutine
117			# cannot destroy itself.
118			my @destroy;
119	root	1.38	my $manager;
120			$manager = new Coro sub {
121	root	1.24	while() {
122	root	1.37	# by overwriting the state object with the manager we destroy it
123			# while still being able to schedule this coroutine (in case it has
124			# been readied multiple times. this is harmless since the manager
125			# can be called as many times as neccessary and will always
126			# remove itself from the runqueue
127	root	1.40	while (@destroy) {
128			my $coro = pop @destroy;
129			$coro->{status} \|\|= [];
130			$_->ready for @{delete $coro->{join} \|\| []};
131			$coro->{_coro_state} = $manager->{_coro_state};
132			}
133	root	1.24	&schedule;
134			}
135			};
136
137	root	1.8	# static methods. not really.
138
139			=head2 STATIC METHODS
140
141			Static methods are actually functions that operate on the current process only.
142
143			=over 4
144
145	root	1.13	=item async { ... } [@args...]
146	root	1.8
147			Create a new asynchronous process and return it's process object
148			(usually unused). When the sub returns the new process is automatically
149			terminated.
150
151	root	1.13	# create a new coroutine that just prints its arguments
152			async {
153			print "@_\n";
154			} 1,2,3,4;
155
156			The coderef you submit MUST NOT be a closure that refers to variables
157			in an outer scope. This does NOT work. Pass arguments into it instead.
158
159	root	1.8	=cut
160
161	root	1.13	sub async(&@) {
162			my $pid = new Coro @_;
163	root	1.24	$manager->ready; # this ensures that the stack is cloned from the manager
164	root	1.11	$pid->ready;
165			$pid;
166	root	1.8	}
167	root	1.1
168	root	1.8	=item schedule
169	root	1.6
170	root	1.8	Calls the scheduler. Please note that the current process will not be put
171			into the ready queue, so calling this function usually means you will
172			never be called again.
173	root	1.1
174			=cut
175
176	root	1.22	=item cede
177	root	1.1
178	root	1.22	"Cede" to other processes. This function puts the current process into the
179			ready queue and calls C<schedule>, which has the effect of giving up the
180			current "timeslice" to other coroutines of the same or higher priority.
181	root	1.7
182	root	1.8	=cut
183
184	root	1.40	=item terminate [arg...]
185	root	1.7
186	root	1.8	Terminates the current process.
187	root	1.1
188	root	1.13	Future versions of this function will allow result arguments.
189
190	root	1.1	=cut
191
192	root	1.8	sub terminate {
193	root	1.40	$current->{status} = [@_];
194	root	1.28	$current->cancel;
195	root	1.23	&schedule;
196	root	1.28	die; # NORETURN
197	root	1.1	}
198	root	1.6
199	root	1.8	=back
200
201			# dynamic methods
202
203			=head2 PROCESS METHODS
204
205			These are the methods you can call on process objects.
206	root	1.6
207	root	1.8	=over 4
208
209	root	1.13	=item new Coro \&sub [, @args...]
210	root	1.8
211			Create a new process and return it. When the sub returns the process
212	root	1.40	automatically terminates as if C<terminate> with the returned values were
213	root	1.41	called. To make the process run you must first put it into the ready queue
214			by calling the ready method.
215	root	1.13
216	root	1.6	=cut
217
218	root	1.13	sub _newcoro {
219			terminate &{+shift};
220			}
221
222	root	1.8	sub new {
223			my $class = shift;
224			bless {
225	root	1.13	_coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
226	root	1.8	}, $class;
227			}
228	root	1.6
229	root	1.8	=item $process->ready
230	root	1.1
231	root	1.39	Put the given process into the ready queue.
232	root	1.1
233	root	1.8	=cut
234	root	1.28
235			=item $process->cancel
236
237			Like C<terminate>, but terminates the specified process instead.
238
239			=cut
240
241			sub cancel {
242			push @destroy, $_[0];
243			$manager->ready;
244	root	1.35	&schedule if $current == $_[0];
245	root	1.40	}
246
247			=item $process->join
248
249			Wait until the coroutine terminates and return any values given to the
250			C<terminate> function. C<join> can be called multiple times from multiple
251			processes.
252
253			=cut
254
255			sub join {
256			my $self = shift;
257			unless ($self->{status}) {
258			push @{$self->{join}}, $current;
259			&schedule;
260			}
261			wantarray ? @{$self->{status}} : $self->{status}[0];
262	root	1.31	}
263
264			=item $oldprio = $process->prio($newprio)
265
266	root	1.41	Sets (or gets, if the argument is missing) the priority of the
267			process. Higher priority processes get run before lower priority
268			processes. Priorities are smalled signed integer (currently -4 .. +3),
269			that you can refer to using PRIO_xxx constants (use the import tag :prio
270			to get then):
271	root	1.31
272			PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
273			3 > 1 > 0 > -1 > -3 > -4
274
275			# set priority to HIGH
276			current->prio(PRIO_HIGH);
277
278			The idle coroutine ($Coro::idle) always has a lower priority than any
279			existing coroutine.
280
281			Changing the priority of the current process will take effect immediately,
282			but changing the priority of processes in the ready queue (but not
283			running) will only take effect after the next schedule (of that
284			process). This is a bug that will be fixed in some future version.
285
286			=cut
287
288			sub prio {
289			my $old = $_[0]{prio};
290			$_[0]{prio} = $_[1] if @_ > 1;
291			$old;
292			}
293
294			=item $newprio = $process->nice($change)
295
296			Similar to C<prio>, but subtract the given value from the priority (i.e.
297			higher values mean lower priority, just as in unix).
298
299			=cut
300
301			sub nice {
302			$_[0]{prio} -= $_[1];
303	root	1.41	}
304
305			=item $olddesc = $process->desc($newdesc)
306
307			Sets (or gets in case the argument is missing) the description for this
308			process. This is just a free-form string you can associate with a process.
309
310			=cut
311
312			sub desc {
313			my $old = $_[0]{desc};
314			$_[0]{desc} = $_[1] if @_ > 1;
315			$old;
316	root	1.8	}
317	root	1.1
318	root	1.8	=back
319	root	1.2
320	root	1.8	=cut
321	root	1.2
322	root	1.8	1;
323	root	1.14
324	root	1.17	=head1 BUGS/LIMITATIONS
325	root	1.14
326	root	1.33	- you must make very sure that no coro is still active on global destruction.
327			very bad things might happen otherwise (usually segfaults).
328	root	1.42	- this module is not thread-safe. You should only ever use this module from
329	root	1.17	the same thread (this requirement might be loosened in the future to
330	root	1.20	allow per-thread schedulers, but Coro::State does not yet allow this).
331	root	1.9
332			=head1 SEE ALSO
333
334			L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>,
335	root	1.25	L<Coro::Signal>, L<Coro::State>, L<Coro::Event>, L<Coro::RWLock>,
336	root	1.26	L<Coro::Handle>, L<Coro::Socket>.
337	root	1.1
338			=head1 AUTHOR
339
340			Marc Lehmann <pcg@goof.com>
341			http://www.goof.com/pcg/marc/
342
343			=cut
344