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
      (pop @destroy)->{_coro_state} = $manager->{_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 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 $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:	1.39
Committed:	Tue Oct 9 00:39:08 2001 UTC (22 years, 7 months ago) by root
Branch:	MAIN
Changes since 1.38:	+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	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			(pop @destroy)->{_coro_state} = $manager->{_coro_state} while @destroy;
130	root	1.24	&schedule;
131			}
132			};
133
134	root	1.8	# static methods. not really.
135
136			=head2 STATIC METHODS
137
138			Static methods are actually functions that operate on the current process only.
139
140			=over 4
141
142	root	1.13	=item async { ... } [@args...]
143	root	1.8
144			Create a new asynchronous process and return it's process object
145			(usually unused). When the sub returns the new process is automatically
146			terminated.
147
148	root	1.13	# create a new coroutine that just prints its arguments
149			async {
150			print "@_\n";
151			} 1,2,3,4;
152
153			The coderef you submit MUST NOT be a closure that refers to variables
154			in an outer scope. This does NOT work. Pass arguments into it instead.
155
156	root	1.8	=cut
157
158	root	1.13	sub async(&@) {
159			my $pid = new Coro @_;
160	root	1.24	$manager->ready; # this ensures that the stack is cloned from the manager
161	root	1.11	$pid->ready;
162			$pid;
163	root	1.8	}
164	root	1.1
165	root	1.8	=item schedule
166	root	1.6
167	root	1.8	Calls the scheduler. Please note that the current process will not be put
168			into the ready queue, so calling this function usually means you will
169			never be called again.
170	root	1.1
171			=cut
172
173	root	1.22	=item cede
174	root	1.1
175	root	1.22	"Cede" to other processes. This function puts the current process into the
176			ready queue and calls C<schedule>, which has the effect of giving up the
177			current "timeslice" to other coroutines of the same or higher priority.
178	root	1.7
179	root	1.8	=cut
180
181			=item terminate
182	root	1.7
183	root	1.8	Terminates the current process.
184	root	1.1
185	root	1.13	Future versions of this function will allow result arguments.
186
187	root	1.1	=cut
188
189	root	1.8	sub terminate {
190	root	1.28	$current->cancel;
191	root	1.23	&schedule;
192	root	1.28	die; # NORETURN
193	root	1.1	}
194	root	1.6
195	root	1.8	=back
196
197			# dynamic methods
198
199			=head2 PROCESS METHODS
200
201			These are the methods you can call on process objects.
202	root	1.6
203	root	1.8	=over 4
204
205	root	1.13	=item new Coro \&sub [, @args...]
206	root	1.8
207			Create a new process and return it. When the sub returns the process
208			automatically terminates. To start the process you must first put it into
209			the ready queue by calling the ready method.
210	root	1.6
211	root	1.13	The coderef you submit MUST NOT be a closure that refers to variables
212			in an outer scope. This does NOT work. Pass arguments into it instead.
213
214	root	1.6	=cut
215
216	root	1.13	sub _newcoro {
217			terminate &{+shift};
218			}
219
220	root	1.8	sub new {
221			my $class = shift;
222			bless {
223	root	1.13	_coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
224	root	1.8	}, $class;
225			}
226	root	1.6
227	root	1.8	=item $process->ready
228	root	1.1
229	root	1.39	Put the given process into the ready queue.
230	root	1.1
231	root	1.8	=cut
232	root	1.28
233			=item $process->cancel
234
235			Like C<terminate>, but terminates the specified process instead.
236
237			=cut
238
239			sub cancel {
240			push @destroy, $_[0];
241			$manager->ready;
242	root	1.35	&schedule if $current == $_[0];
243	root	1.31	}
244
245			=item $oldprio = $process->prio($newprio)
246
247			Sets the priority of the process. Higher priority processes get run before
248			lower priority processes. Priorities are smalled signed integer (currently
249			-4 .. +3), that you can refer to using PRIO_xxx constants (use the import
250			tag :prio to get then):
251
252			PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
253			3 > 1 > 0 > -1 > -3 > -4
254
255			# set priority to HIGH
256			current->prio(PRIO_HIGH);
257
258			The idle coroutine ($Coro::idle) always has a lower priority than any
259			existing coroutine.
260
261			Changing the priority of the current process will take effect immediately,
262			but changing the priority of processes in the ready queue (but not
263			running) will only take effect after the next schedule (of that
264			process). This is a bug that will be fixed in some future version.
265
266			=cut
267
268			sub prio {
269			my $old = $_[0]{prio};
270			$_[0]{prio} = $_[1] if @_ > 1;
271			$old;
272			}
273
274			=item $newprio = $process->nice($change)
275
276			Similar to C<prio>, but subtract the given value from the priority (i.e.
277			higher values mean lower priority, just as in unix).
278
279			=cut
280
281			sub nice {
282			$_[0]{prio} -= $_[1];
283	root	1.8	}
284	root	1.1
285	root	1.8	=back
286	root	1.2
287	root	1.8	=cut
288	root	1.2
289	root	1.8	1;
290	root	1.14
291	root	1.17	=head1 BUGS/LIMITATIONS
292	root	1.14
293	root	1.33	- you must make very sure that no coro is still active on global destruction.
294			very bad things might happen otherwise (usually segfaults).
295	root	1.17	- this module is not thread-safe. You must only ever use this module from
296			the same thread (this requirement might be loosened in the future to
297	root	1.20	allow per-thread schedulers, but Coro::State does not yet allow this).
298	root	1.9
299			=head1 SEE ALSO
300
301			L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>,
302	root	1.25	L<Coro::Signal>, L<Coro::State>, L<Coro::Event>, L<Coro::RWLock>,
303	root	1.26	L<Coro::Handle>, L<Coro::Socket>.
304	root	1.1
305			=head1 AUTHOR
306
307			Marc Lehmann <pcg@goof.com>
308			http://www.goof.com/pcg/marc/
309
310			=cut
311