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 = 0.5;

@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;
   &schedule if $current == $_[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:	1.36
Committed:	Mon Sep 24 01:36:20 2001 UTC (22 years, 8 months ago) by root
Branch:	MAIN
Changes since 1.35:	+2 -0 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	1.34	$VERSION = 0.5;
44	root	1.8
45	root	1.22	@EXPORT = qw(async cede schedule terminate current);
46	root	1.31	%EXPORT_TAGS = (
47			prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
48			);
49			@EXPORT_OK = @{$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			my $manager = new Coro sub {
122			while() {
123			delete ((pop @destroy)->{_coro_state}) while @destroy;
124			&schedule;
125			}
126			};
127
128	root	1.8	# static methods. not really.
129
130			=head2 STATIC METHODS
131
132			Static methods are actually functions that operate on the current process only.
133
134			=over 4
135
136	root	1.13	=item async { ... } [@args...]
137	root	1.8
138			Create a new asynchronous process and return it's process object
139			(usually unused). When the sub returns the new process is automatically
140			terminated.
141
142	root	1.13	# create a new coroutine that just prints its arguments
143			async {
144			print "@_\n";
145			} 1,2,3,4;
146
147			The coderef you submit MUST NOT be a closure that refers to variables
148			in an outer scope. This does NOT work. Pass arguments into it instead.
149
150	root	1.8	=cut
151
152	root	1.13	sub async(&@) {
153			my $pid = new Coro @_;
154	root	1.24	$manager->ready; # this ensures that the stack is cloned from the manager
155	root	1.11	$pid->ready;
156			$pid;
157	root	1.8	}
158	root	1.1
159	root	1.8	=item schedule
160	root	1.6
161	root	1.8	Calls the scheduler. Please note that the current process will not be put
162			into the ready queue, so calling this function usually means you will
163			never be called again.
164	root	1.1
165			=cut
166
167	root	1.22	=item cede
168	root	1.1
169	root	1.22	"Cede" to other processes. This function puts the current process into the
170			ready queue and calls C<schedule>, which has the effect of giving up the
171			current "timeslice" to other coroutines of the same or higher priority.
172	root	1.7
173	root	1.8	=cut
174
175			=item terminate
176	root	1.7
177	root	1.8	Terminates the current process.
178	root	1.1
179	root	1.13	Future versions of this function will allow result arguments.
180
181	root	1.1	=cut
182
183	root	1.8	sub terminate {
184	root	1.28	$current->cancel;
185	root	1.23	&schedule;
186	root	1.28	die; # NORETURN
187	root	1.1	}
188	root	1.6
189	root	1.8	=back
190
191			# dynamic methods
192
193			=head2 PROCESS METHODS
194
195			These are the methods you can call on process objects.
196	root	1.6
197	root	1.8	=over 4
198
199	root	1.13	=item new Coro \&sub [, @args...]
200	root	1.8
201			Create a new process and return it. When the sub returns the process
202			automatically terminates. To start the process you must first put it into
203			the ready queue by calling the ready method.
204	root	1.6
205	root	1.13	The coderef you submit MUST NOT be a closure that refers to variables
206			in an outer scope. This does NOT work. Pass arguments into it instead.
207
208	root	1.6	=cut
209
210	root	1.13	sub _newcoro {
211			terminate &{+shift};
212			}
213
214	root	1.8	sub new {
215			my $class = shift;
216			bless {
217	root	1.13	_coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
218	root	1.8	}, $class;
219			}
220	root	1.6
221	root	1.8	=item $process->ready
222	root	1.1
223	root	1.8	Put the current process into the ready queue.
224	root	1.1
225	root	1.8	=cut
226	root	1.28
227			=item $process->cancel
228
229			Like C<terminate>, but terminates the specified process instead.
230
231			=cut
232
233			sub cancel {
234			push @destroy, $_[0];
235			$manager->ready;
236	root	1.35	&schedule if $current == $_[0];
237	root	1.31	}
238
239			=item $oldprio = $process->prio($newprio)
240
241			Sets the priority of the process. Higher priority processes get run before
242			lower priority processes. Priorities are smalled signed integer (currently
243			-4 .. +3), that you can refer to using PRIO_xxx constants (use the import
244			tag :prio to get then):
245
246			PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
247			3 > 1 > 0 > -1 > -3 > -4
248
249			# set priority to HIGH
250			current->prio(PRIO_HIGH);
251
252			The idle coroutine ($Coro::idle) always has a lower priority than any
253			existing coroutine.
254
255			Changing the priority of the current process will take effect immediately,
256			but changing the priority of processes in the ready queue (but not
257			running) will only take effect after the next schedule (of that
258			process). This is a bug that will be fixed in some future version.
259
260			=cut
261
262			sub prio {
263			my $old = $_[0]{prio};
264			$_[0]{prio} = $_[1] if @_ > 1;
265			$old;
266			}
267
268			=item $newprio = $process->nice($change)
269
270			Similar to C<prio>, but subtract the given value from the priority (i.e.
271			higher values mean lower priority, just as in unix).
272
273			=cut
274
275			sub nice {
276			$_[0]{prio} -= $_[1];
277	root	1.8	}
278	root	1.1
279	root	1.8	=back
280	root	1.2
281	root	1.8	=cut
282	root	1.2
283	root	1.8	1;
284	root	1.14
285	root	1.17	=head1 BUGS/LIMITATIONS
286	root	1.14
287	root	1.33	- you must make very sure that no coro is still active on global destruction.
288			very bad things might happen otherwise (usually segfaults).
289	root	1.17	- this module is not thread-safe. You must only ever use this module from
290			the same thread (this requirement might be loosened in the future to
291	root	1.20	allow per-thread schedulers, but Coro::State does not yet allow this).
292	root	1.9
293			=head1 SEE ALSO
294
295			L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>,
296	root	1.25	L<Coro::Signal>, L<Coro::State>, L<Coro::Event>, L<Coro::RWLock>,
297	root	1.26	L<Coro::Handle>, L<Coro::Socket>.
298	root	1.1
299			=head1 AUTHOR
300
301			Marc Lehmann <pcg@goof.com>
302			http://www.goof.com/pcg/marc/
303
304			=cut
305