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;

BEGIN { eval { require warnings } && warnings->unimport ("uninitialized") }

use Coro::State;

use vars qw($idle $main $current);

use base Exporter;

$VERSION = 0.8;

@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

$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};
}

$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 :(
$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 small signed integers (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 losened 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::Timer>, L<Coro::Event>,
L<Coro::L<Coro::RWLock>, Handle>, L<Coro::Socket>.

=head1 AUTHOR

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

=cut

Revision:	1.55
Committed:	Wed Nov 5 20:02:44 2003 UTC (20 years, 7 months ago) by pcg
Branch:	MAIN
Changes since 1.54:	+7 -5 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	+ @_ + $_ + $@ + $^W + C stack), that is, a coroutine has it's own
28			callchain, it's own set of lexicals and it's own set of perl's most
29			important global variables.
30	root	1.22
31	root	1.8	=cut
32
33			package Coro;
34
35	pcg	1.55	BEGIN { eval { require warnings } && warnings->unimport ("uninitialized") }
36	root	1.36
37	root	1.8	use Coro::State;
38
39	pcg	1.55	use vars qw($idle $main $current);
40
41	root	1.8	use base Exporter;
42
43	pcg	1.55	$VERSION = 0.8;
44	root	1.8
45	root	1.22	@EXPORT = qw(async cede schedule terminate current);
46	root	1.31	%EXPORT_TAGS = (
47			prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
48			);
49			@EXPORT_OK = @{$EXPORT_TAGS{prio}};
50	root	1.8
51			{
52			my @async;
53	root	1.26	my $init;
54	root	1.8
55			# this way of handling attributes simply is NOT scalable ;()
56			sub import {
57			Coro->export_to_level(1, @_);
58			my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
59			*{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
60			my ($package, $ref) = (shift, shift);
61			my @attrs;
62			for (@_) {
63			if ($_ eq "Coro") {
64			push @async, $ref;
65	root	1.26	unless ($init++) {
66			eval q{
67			sub INIT {
68			&async(pop @async) while @async;
69			}
70			};
71			}
72	root	1.8	} else {
73	root	1.17	push @attrs, $_;
74	root	1.8	}
75			}
76	root	1.17	return $old ? $old->($package, $ref, @attrs) : @attrs;
77	root	1.8	};
78			}
79
80			}
81
82	root	1.43	=over 4
83
84	root	1.8	=item $main
85	root	1.2
86	root	1.8	This coroutine represents the main program.
87	root	1.1
88			=cut
89
90	pcg	1.55	$main = new Coro;
91	root	1.8
92	root	1.19	=item $current (or as function: current)
93	root	1.1
94	root	1.8	The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course).
95	root	1.1
96	root	1.8	=cut
97
98			# maybe some other module used Coro::Specific before...
99			if ($current) {
100			$main->{specific} = $current->{specific};
101	root	1.1	}
102
103	pcg	1.55	$current = $main;
104	root	1.19
105			sub current() { $current }
106	root	1.9
107			=item $idle
108
109			The coroutine to switch to when no other coroutine is running. The default
110			implementation prints "FATAL: deadlock detected" and exits.
111
112			=cut
113
114			# should be done using priorities :(
115	pcg	1.55	$idle = new Coro sub {
116	root	1.9	print STDERR "FATAL: deadlock detected\n";
117			exit(51);
118			};
119	root	1.8
120	root	1.24	# this coroutine is necessary because a coroutine
121			# cannot destroy itself.
122			my @destroy;
123	root	1.38	my $manager;
124			$manager = new Coro sub {
125	root	1.24	while() {
126	root	1.37	# by overwriting the state object with the manager we destroy it
127			# while still being able to schedule this coroutine (in case it has
128			# been readied multiple times. this is harmless since the manager
129			# can be called as many times as neccessary and will always
130			# remove itself from the runqueue
131	root	1.40	while (@destroy) {
132			my $coro = pop @destroy;
133			$coro->{status} \|\|= [];
134			$_->ready for @{delete $coro->{join} \|\| []};
135			$coro->{_coro_state} = $manager->{_coro_state};
136			}
137	root	1.24	&schedule;
138			}
139			};
140
141	root	1.8	# static methods. not really.
142	root	1.43
143			=back
144	root	1.8
145			=head2 STATIC METHODS
146
147			Static methods are actually functions that operate on the current process only.
148
149			=over 4
150
151	root	1.13	=item async { ... } [@args...]
152	root	1.8
153			Create a new asynchronous process and return it's process object
154			(usually unused). When the sub returns the new process is automatically
155			terminated.
156
157	root	1.13	# create a new coroutine that just prints its arguments
158			async {
159			print "@_\n";
160			} 1,2,3,4;
161
162			The coderef you submit MUST NOT be a closure that refers to variables
163			in an outer scope. This does NOT work. Pass arguments into it instead.
164
165	root	1.8	=cut
166
167	root	1.13	sub async(&@) {
168			my $pid = new Coro @_;
169	root	1.24	$manager->ready; # this ensures that the stack is cloned from the manager
170	root	1.11	$pid->ready;
171			$pid;
172	root	1.8	}
173	root	1.1
174	root	1.8	=item schedule
175	root	1.6
176	root	1.8	Calls the scheduler. Please note that the current process will not be put
177			into the ready queue, so calling this function usually means you will
178			never be called again.
179	root	1.1
180			=cut
181
182	root	1.22	=item cede
183	root	1.1
184	root	1.22	"Cede" to other processes. This function puts the current process into the
185			ready queue and calls C<schedule>, which has the effect of giving up the
186			current "timeslice" to other coroutines of the same or higher priority.
187	root	1.7
188	root	1.8	=cut
189
190	root	1.40	=item terminate [arg...]
191	root	1.7
192	root	1.8	Terminates the current process.
193	root	1.1
194	root	1.13	Future versions of this function will allow result arguments.
195
196	root	1.1	=cut
197
198	root	1.8	sub terminate {
199	root	1.40	$current->{status} = [@_];
200	root	1.28	$current->cancel;
201	root	1.23	&schedule;
202	root	1.28	die; # NORETURN
203	root	1.1	}
204	root	1.6
205	root	1.8	=back
206
207			# dynamic methods
208
209			=head2 PROCESS METHODS
210
211			These are the methods you can call on process objects.
212	root	1.6
213	root	1.8	=over 4
214
215	root	1.13	=item new Coro \&sub [, @args...]
216	root	1.8
217			Create a new process and return it. When the sub returns the process
218	root	1.40	automatically terminates as if C<terminate> with the returned values were
219	root	1.41	called. To make the process run you must first put it into the ready queue
220			by calling the ready method.
221	root	1.13
222	root	1.6	=cut
223
224	root	1.13	sub _newcoro {
225			terminate &{+shift};
226			}
227
228	root	1.8	sub new {
229			my $class = shift;
230			bless {
231	root	1.13	_coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
232	root	1.8	}, $class;
233			}
234	root	1.6
235	root	1.8	=item $process->ready
236	root	1.1
237	root	1.39	Put the given process into the ready queue.
238	root	1.1
239	root	1.8	=cut
240	root	1.28
241			=item $process->cancel
242
243			Like C<terminate>, but terminates the specified process instead.
244
245			=cut
246
247			sub cancel {
248			push @destroy, $_[0];
249			$manager->ready;
250	root	1.35	&schedule if $current == $_[0];
251	root	1.40	}
252
253			=item $process->join
254
255			Wait until the coroutine terminates and return any values given to the
256			C<terminate> function. C<join> can be called multiple times from multiple
257			processes.
258
259			=cut
260
261			sub join {
262			my $self = shift;
263			unless ($self->{status}) {
264			push @{$self->{join}}, $current;
265			&schedule;
266			}
267			wantarray ? @{$self->{status}} : $self->{status}[0];
268	root	1.31	}
269
270			=item $oldprio = $process->prio($newprio)
271
272	root	1.41	Sets (or gets, if the argument is missing) the priority of the
273			process. Higher priority processes get run before lower priority
274	root	1.52	processes. Priorities are small signed integers (currently -4 .. +3),
275	root	1.41	that you can refer to using PRIO_xxx constants (use the import tag :prio
276			to get then):
277	root	1.31
278			PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
279			3 > 1 > 0 > -1 > -3 > -4
280
281			# set priority to HIGH
282			current->prio(PRIO_HIGH);
283
284			The idle coroutine ($Coro::idle) always has a lower priority than any
285			existing coroutine.
286
287			Changing the priority of the current process will take effect immediately,
288			but changing the priority of processes in the ready queue (but not
289			running) will only take effect after the next schedule (of that
290			process). This is a bug that will be fixed in some future version.
291
292			=cut
293
294			sub prio {
295			my $old = $_[0]{prio};
296			$_[0]{prio} = $_[1] if @_ > 1;
297			$old;
298			}
299
300			=item $newprio = $process->nice($change)
301
302			Similar to C<prio>, but subtract the given value from the priority (i.e.
303			higher values mean lower priority, just as in unix).
304
305			=cut
306
307			sub nice {
308			$_[0]{prio} -= $_[1];
309	root	1.41	}
310
311			=item $olddesc = $process->desc($newdesc)
312
313			Sets (or gets in case the argument is missing) the description for this
314			process. This is just a free-form string you can associate with a process.
315
316			=cut
317
318			sub desc {
319			my $old = $_[0]{desc};
320			$_[0]{desc} = $_[1] if @_ > 1;
321			$old;
322	root	1.8	}
323	root	1.1
324	root	1.8	=back
325	root	1.2
326	root	1.8	=cut
327	root	1.2
328	root	1.8	1;
329	root	1.14
330	root	1.17	=head1 BUGS/LIMITATIONS
331	root	1.14
332	root	1.52	- you must make very sure that no coro is still active on global
333	root	1.53	destruction. very bad things might happen otherwise (usually segfaults).
334	root	1.52
335			- this module is not thread-safe. You should only ever use this module
336			from the same thread (this requirement might be losened in the future
337			to allow per-thread schedulers, but Coro::State does not yet allow
338			this).
339	root	1.9
340			=head1 SEE ALSO
341
342			L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>,
343	pcg	1.54	L<Coro::Signal>, L<Coro::State>, L<Coro::Timer>, L<Coro::Event>,
344			L<Coro::L<Coro::RWLock>, Handle>, L<Coro::Socket>.
345	root	1.1
346			=head1 AUTHOR
347
348			Marc Lehmann <pcg@goof.com>
349			http://www.goof.com/pcg/marc/
350
351			=cut
352