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;

no warnings qw(uninitialized);

use Coro::State;

use base Exporter;

$VERSION = 0.51;

@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 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 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 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];
}

=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 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::Handle>, L<Coro::Socket>.

=head1 AUTHOR

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

=cut

Revision:	1.40
Committed:	Sun Oct 28 17:00:05 2001 UTC (22 years, 7 months ago) by root
Branch:	MAIN
Changes since 1.39:	+28 -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			Threads but don't run in parallel.
25
26			This module is still experimental, see the BUGS section below.
27
28	root	1.20	In this module, coroutines are defined as "callchain + lexical variables
29	root	1.23	+ @_ + $_ + $@ + $^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	root	1.22
33	root	1.8	=cut
34
35			package Coro;
36
37	root	1.36	no warnings qw(uninitialized);
38
39	root	1.8	use Coro::State;
40
41			use base Exporter;
42
43	root	1.38	$VERSION = 0.51;
44	root	1.8
45	root	1.22	@EXPORT = qw(async cede schedule terminate current);
46	root	1.31	%EXPORT_TAGS = (
47			prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
48			);
49			@EXPORT_OK = @{$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			=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
141			=head2 STATIC METHODS
142
143			Static methods are actually functions that operate on the current process only.
144
145			=over 4
146
147	root	1.13	=item async { ... } [@args...]
148	root	1.8
149			Create a new asynchronous process and return it's process object
150			(usually unused). When the sub returns the new process is automatically
151			terminated.
152
153	root	1.13	# create a new coroutine that just prints its arguments
154			async {
155			print "@_\n";
156			} 1,2,3,4;
157
158			The coderef you submit MUST NOT be a closure that refers to variables
159			in an outer scope. This does NOT work. Pass arguments into it instead.
160
161	root	1.8	=cut
162
163	root	1.13	sub async(&@) {
164			my $pid = new Coro @_;
165	root	1.24	$manager->ready; # this ensures that the stack is cloned from the manager
166	root	1.11	$pid->ready;
167			$pid;
168	root	1.8	}
169	root	1.1
170	root	1.8	=item schedule
171	root	1.6
172	root	1.8	Calls the scheduler. Please note that the current process will not be put
173			into the ready queue, so calling this function usually means you will
174			never be called again.
175	root	1.1
176			=cut
177
178	root	1.22	=item cede
179	root	1.1
180	root	1.22	"Cede" to other processes. This function puts the current process into the
181			ready queue and calls C<schedule>, which has the effect of giving up the
182			current "timeslice" to other coroutines of the same or higher priority.
183	root	1.7
184	root	1.8	=cut
185
186	root	1.40	=item terminate [arg...]
187	root	1.7
188	root	1.8	Terminates the current process.
189	root	1.1
190	root	1.13	Future versions of this function will allow result arguments.
191
192	root	1.1	=cut
193
194	root	1.8	sub terminate {
195	root	1.40	$current->{status} = [@_];
196	root	1.28	$current->cancel;
197	root	1.23	&schedule;
198	root	1.28	die; # NORETURN
199	root	1.1	}
200	root	1.6
201	root	1.8	=back
202
203			# dynamic methods
204
205			=head2 PROCESS METHODS
206
207			These are the methods you can call on process objects.
208	root	1.6
209	root	1.8	=over 4
210
211	root	1.13	=item new Coro \&sub [, @args...]
212	root	1.8
213			Create a new process and return it. When the sub returns the process
214	root	1.40	automatically terminates as if C<terminate> with the returned values were
215			called. To start the process you must first put it into the ready queue by
216			calling the ready method.
217	root	1.6
218	root	1.13	The coderef you submit MUST NOT be a closure that refers to variables
219			in an outer scope. This does NOT work. Pass arguments into it instead.
220
221	root	1.6	=cut
222
223	root	1.13	sub _newcoro {
224			terminate &{+shift};
225			}
226
227	root	1.8	sub new {
228			my $class = shift;
229			bless {
230	root	1.13	_coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
231	root	1.8	}, $class;
232			}
233	root	1.6
234	root	1.8	=item $process->ready
235	root	1.1
236	root	1.39	Put the given process into the ready queue.
237	root	1.1
238	root	1.8	=cut
239	root	1.28
240			=item $process->cancel
241
242			Like C<terminate>, but terminates the specified process instead.
243
244			=cut
245
246			sub cancel {
247			push @destroy, $_[0];
248			$manager->ready;
249	root	1.35	&schedule if $current == $_[0];
250	root	1.40	}
251
252			=item $process->join
253
254			Wait until the coroutine terminates and return any values given to the
255			C<terminate> function. C<join> can be called multiple times from multiple
256			processes.
257
258			=cut
259
260			sub join {
261			my $self = shift;
262			unless ($self->{status}) {
263			push @{$self->{join}}, $current;
264			&schedule;
265			}
266			wantarray ? @{$self->{status}} : $self->{status}[0];
267	root	1.31	}
268
269			=item $oldprio = $process->prio($newprio)
270
271			Sets the priority of the process. Higher priority processes get run before
272			lower priority processes. Priorities are smalled signed integer (currently
273			-4 .. +3), that you can refer to using PRIO_xxx constants (use the import
274			tag :prio to get then):
275
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	1.8	}
308	root	1.1
309	root	1.8	=back
310	root	1.2
311	root	1.8	=cut
312	root	1.2
313	root	1.8	1;
314	root	1.14
315	root	1.17	=head1 BUGS/LIMITATIONS
316	root	1.14
317	root	1.33	- you must make very sure that no coro is still active on global destruction.
318			very bad things might happen otherwise (usually segfaults).
319	root	1.17	- this module is not thread-safe. You must only ever use this module from
320			the same thread (this requirement might be loosened in the future to
321	root	1.20	allow per-thread schedulers, but Coro::State does not yet allow this).
322	root	1.9
323			=head1 SEE ALSO
324
325			L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>,
326	root	1.25	L<Coro::Signal>, L<Coro::State>, L<Coro::Event>, L<Coro::RWLock>,
327	root	1.26	L<Coro::Handle>, L<Coro::Socket>.
328	root	1.1
329			=head1 AUTHOR
330
331			Marc Lehmann <pcg@goof.com>
332			http://www.goof.com/pcg/marc/
333
334			=cut
335