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;

use Coro::State;

use base Exporter;

$VERSION = 0.49;

@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 = new Coro sub {
   while() {
      delete ((pop @destroy)->{_coro_state}) while @destroy;
      &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

Terminates the current process.

Future versions of this function will allow result arguments.

=cut

sub terminate {
   $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. 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

=item $process->cancel

Like C<terminate>, but terminates the specified process instead.

=cut

sub cancel {
   push @destroy, $_[0];
   $manager->ready;
}

=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

 - 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>, L<Coro::RWLock>,
L<Coro::Handle>, L<Coro::Socket>.

=head1 AUTHOR

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

=cut

Revision:	1.32
Committed:	Sun Sep 2 01:03:53 2001 UTC (22 years, 9 months ago) by root
Branch:	MAIN
Changes since 1.31:	+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			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			use Coro::State;
38
39			use base Exporter;
40
41	root	1.32	$VERSION = 0.49;
42	root	1.8
43	root	1.22	@EXPORT = qw(async cede schedule terminate current);
44	root	1.31	%EXPORT_TAGS = (
45			prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
46			);
47			@EXPORT_OK = @{$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			my $manager = new Coro sub {
120			while() {
121			delete ((pop @destroy)->{_coro_state}) while @destroy;
122			&schedule;
123			}
124			};
125
126	root	1.8	# static methods. not really.
127
128			=head2 STATIC METHODS
129
130			Static methods are actually functions that operate on the current process only.
131
132			=over 4
133
134	root	1.13	=item async { ... } [@args...]
135	root	1.8
136			Create a new asynchronous process and return it's process object
137			(usually unused). When the sub returns the new process is automatically
138			terminated.
139
140	root	1.13	# create a new coroutine that just prints its arguments
141			async {
142			print "@_\n";
143			} 1,2,3,4;
144
145			The coderef you submit MUST NOT be a closure that refers to variables
146			in an outer scope. This does NOT work. Pass arguments into it instead.
147
148	root	1.8	=cut
149
150	root	1.13	sub async(&@) {
151			my $pid = new Coro @_;
152	root	1.24	$manager->ready; # this ensures that the stack is cloned from the manager
153	root	1.11	$pid->ready;
154			$pid;
155	root	1.8	}
156	root	1.1
157	root	1.8	=item schedule
158	root	1.6
159	root	1.8	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	root	1.1
163			=cut
164
165	root	1.22	=item cede
166	root	1.1
167	root	1.22	"Cede" to other processes. This function puts the current process into the
168			ready queue and calls C<schedule>, which has the effect of giving up the
169			current "timeslice" to other coroutines of the same or higher priority.
170	root	1.7
171	root	1.8	=cut
172
173			=item terminate
174	root	1.7
175	root	1.8	Terminates the current process.
176	root	1.1
177	root	1.13	Future versions of this function will allow result arguments.
178
179	root	1.1	=cut
180
181	root	1.8	sub terminate {
182	root	1.28	$current->cancel;
183	root	1.23	&schedule;
184	root	1.28	die; # NORETURN
185	root	1.1	}
186	root	1.6
187	root	1.8	=back
188
189			# dynamic methods
190
191			=head2 PROCESS METHODS
192
193			These are the methods you can call on process objects.
194	root	1.6
195	root	1.8	=over 4
196
197	root	1.13	=item new Coro \&sub [, @args...]
198	root	1.8
199			Create a new process and return it. When the sub returns the process
200			automatically terminates. To start the process you must first put it into
201			the ready queue by calling the ready method.
202	root	1.6
203	root	1.13	The coderef you submit MUST NOT be a closure that refers to variables
204			in an outer scope. This does NOT work. Pass arguments into it instead.
205
206	root	1.6	=cut
207
208	root	1.13	sub _newcoro {
209			terminate &{+shift};
210			}
211
212	root	1.8	sub new {
213			my $class = shift;
214			bless {
215	root	1.13	_coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
216	root	1.8	}, $class;
217			}
218	root	1.6
219	root	1.8	=item $process->ready
220	root	1.1
221	root	1.8	Put the current process into the ready queue.
222	root	1.1
223	root	1.8	=cut
224	root	1.28
225			=item $process->cancel
226
227			Like C<terminate>, but terminates the specified process instead.
228
229			=cut
230
231			sub cancel {
232			push @destroy, $_[0];
233			$manager->ready;
234	root	1.31	}
235
236			=item $oldprio = $process->prio($newprio)
237
238			Sets the priority of the process. Higher priority processes get run before
239			lower priority processes. Priorities are smalled signed integer (currently
240			-4 .. +3), that you can refer to using PRIO_xxx constants (use the import
241			tag :prio to get then):
242
243			PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
244			3 > 1 > 0 > -1 > -3 > -4
245
246			# set priority to HIGH
247			current->prio(PRIO_HIGH);
248
249			The idle coroutine ($Coro::idle) always has a lower priority than any
250			existing coroutine.
251
252			Changing the priority of the current process will take effect immediately,
253			but changing the priority of processes in the ready queue (but not
254			running) will only take effect after the next schedule (of that
255			process). This is a bug that will be fixed in some future version.
256
257			=cut
258
259			sub prio {
260			my $old = $_[0]{prio};
261			$_[0]{prio} = $_[1] if @_ > 1;
262			$old;
263			}
264
265			=item $newprio = $process->nice($change)
266
267			Similar to C<prio>, but subtract the given value from the priority (i.e.
268			higher values mean lower priority, just as in unix).
269
270			=cut
271
272			sub nice {
273			$_[0]{prio} -= $_[1];
274	root	1.8	}
275	root	1.1
276	root	1.8	=back
277	root	1.2
278	root	1.8	=cut
279	root	1.2
280	root	1.8	1;
281	root	1.14
282	root	1.17	=head1 BUGS/LIMITATIONS
283	root	1.14
284			- could be faster, especially when the core would introduce special
285			support for coroutines (like it does for threads).
286			- there is still a memleak on coroutine termination that I could not
287			identify. Could be as small as a single SV.
288			- this module is not well-tested.
289	root	1.17	- if variables or arguments "disappear" (become undef) or become
290			corrupted please contact the author so he cen iron out the
291			remaining bugs.
292			- this module is not thread-safe. You must only ever use this module from
293			the same thread (this requirement might be loosened in the future to
294	root	1.20	allow per-thread schedulers, but Coro::State does not yet allow this).
295	root	1.9
296			=head1 SEE ALSO
297
298			L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>,
299	root	1.25	L<Coro::Signal>, L<Coro::State>, L<Coro::Event>, L<Coro::RWLock>,
300	root	1.26	L<Coro::Handle>, L<Coro::Socket>.
301	root	1.1
302			=head1 AUTHOR
303
304			Marc Lehmann <pcg@goof.com>
305			http://www.goof.com/pcg/marc/
306
307			=cut
308