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;

use strict;
no warnings "uninitialized";

use Coro::State;

use base Exporter::;

our $idle;    # idle coroutine
our $main;    # main coroutine
our $current; # current coroutine

our $VERSION = '2.5';

our @EXPORT = qw(async cede schedule terminate current);
our %EXPORT_TAGS = (
      prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
);
our @EXPORT_OK = @{$EXPORT_TAGS{prio}};

{
   my @async;
   my $init;

   # this way of handling attributes simply is NOT scalable ;()
   sub import {
      no strict 'refs';

      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} || []};

         # the next line destroys the _coro_state, but keeps the
         # process itself intact (we basically make it a zombie
         # process that always runs the manager thread, so it's possible
         # to transfer() to this process).
         $coro->{_coro_state}->_clone_state_from ($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.

When the coroutine dies, the program will exit, just as in the main
program.

   # create a new coroutine that just prints its arguments
   async {
      print "@_\n";
   } 1,2,3,4;

=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 with the given status values (see L<cancel>).

=cut

sub terminate {
   $current->cancel (@_);
}

=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 \&_newcoro, @_),
   }, $class;
}

=item $process->ready

Put the given process into the ready queue.

=cut

=item $process->cancel (arg...)

Terminates the given process and makes it return the given arguments as
status (default: the empty list).

=cut

sub cancel {
   my $self = shift;
   $self->{status} = [@_];
   push @destroy, $self;
   $manager->ready;
   &schedule if $current == $self;
}

=item $process->join

Wait until the coroutine terminates and return any values given to the
C<terminate> or C<cancel> functions. 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 {
   shift->{_coro_state}->prio (@_)
}

=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 {
   shift->{_coro_state}->nice (@_)
}

=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

Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.

Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.

Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.

Embedding: L<Coro:MakeMaker>

=head1 AUTHOR

 Marc Lehmann <schmorp@schmorp.de>
 http://home.schmorp.de/

=cut

Revision:	1.82
Committed:	Fri Nov 24 13:40:36 2006 UTC (17 years, 6 months ago) by root
Branch:	MAIN
Changes since 1.81:	+6 -8 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	root	1.71	use strict;
36			no warnings "uninitialized";
37	root	1.36
38	root	1.8	use Coro::State;
39
40	root	1.71	use base Exporter::;
41	pcg	1.55
42	root	1.71	our $idle; # idle coroutine
43			our $main; # main coroutine
44			our $current; # current coroutine
45	root	1.8
46	root	1.80	our $VERSION = '2.5';
47	root	1.8
48	root	1.71	our @EXPORT = qw(async cede schedule terminate current);
49			our %EXPORT_TAGS = (
50	root	1.31	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
51			);
52	root	1.71	our @EXPORT_OK = @{$EXPORT_TAGS{prio}};
53	root	1.8
54			{
55			my @async;
56	root	1.26	my $init;
57	root	1.8
58			# this way of handling attributes simply is NOT scalable ;()
59			sub import {
60	root	1.71	no strict 'refs';
61
62	root	1.8	Coro->export_to_level(1, @_);
63	root	1.71
64	root	1.8	my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
65			*{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
66			my ($package, $ref) = (shift, shift);
67			my @attrs;
68			for (@_) {
69			if ($_ eq "Coro") {
70			push @async, $ref;
71	root	1.26	unless ($init++) {
72			eval q{
73			sub INIT {
74			&async(pop @async) while @async;
75			}
76			};
77			}
78	root	1.8	} else {
79	root	1.17	push @attrs, $_;
80	root	1.8	}
81			}
82	root	1.17	return $old ? $old->($package, $ref, @attrs) : @attrs;
83	root	1.8	};
84			}
85
86			}
87
88	root	1.43	=over 4
89
90	root	1.8	=item $main
91	root	1.2
92	root	1.8	This coroutine represents the main program.
93	root	1.1
94			=cut
95
96	pcg	1.55	$main = new Coro;
97	root	1.8
98	root	1.19	=item $current (or as function: current)
99	root	1.1
100	root	1.8	The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course).
101	root	1.1
102	root	1.8	=cut
103
104			# maybe some other module used Coro::Specific before...
105			if ($current) {
106			$main->{specific} = $current->{specific};
107	root	1.1	}
108
109	pcg	1.55	$current = $main;
110	root	1.19
111			sub current() { $current }
112	root	1.9
113			=item $idle
114
115			The coroutine to switch to when no other coroutine is running. The default
116			implementation prints "FATAL: deadlock detected" and exits.
117
118			=cut
119
120			# should be done using priorities :(
121	pcg	1.55	$idle = new Coro sub {
122	root	1.9	print STDERR "FATAL: deadlock detected\n";
123			exit(51);
124			};
125	root	1.8
126	root	1.24	# this coroutine is necessary because a coroutine
127			# cannot destroy itself.
128			my @destroy;
129	root	1.38	my $manager;
130			$manager = new Coro sub {
131	pcg	1.57	while () {
132	root	1.37	# by overwriting the state object with the manager we destroy it
133			# while still being able to schedule this coroutine (in case it has
134			# been readied multiple times. this is harmless since the manager
135			# can be called as many times as neccessary and will always
136			# remove itself from the runqueue
137	root	1.40	while (@destroy) {
138			my $coro = pop @destroy;
139			$coro->{status} \|\|= [];
140			$_->ready for @{delete $coro->{join} \|\| []};
141	pcg	1.59
142			# the next line destroys the _coro_state, but keeps the
143			# process itself intact (we basically make it a zombie
144			# process that always runs the manager thread, so it's possible
145			# to transfer() to this process).
146	root	1.82	$coro->{_coro_state}->_clone_state_from ($manager->{_coro_state});
147	root	1.40	}
148	root	1.24	&schedule;
149			}
150			};
151
152	root	1.8	# static methods. not really.
153	root	1.43
154			=back
155	root	1.8
156			=head2 STATIC METHODS
157
158			Static methods are actually functions that operate on the current process only.
159
160			=over 4
161
162	root	1.13	=item async { ... } [@args...]
163	root	1.8
164			Create a new asynchronous process and return it's process object
165			(usually unused). When the sub returns the new process is automatically
166			terminated.
167
168	root	1.79	When the coroutine dies, the program will exit, just as in the main
169			program.
170
171	root	1.13	# create a new coroutine that just prints its arguments
172			async {
173			print "@_\n";
174			} 1,2,3,4;
175
176	root	1.8	=cut
177
178	root	1.13	sub async(&@) {
179			my $pid = new Coro @_;
180	root	1.24	$manager->ready; # this ensures that the stack is cloned from the manager
181	root	1.11	$pid->ready;
182			$pid;
183	root	1.8	}
184	root	1.1
185	root	1.8	=item schedule
186	root	1.6
187	root	1.8	Calls the scheduler. Please note that the current process will not be put
188			into the ready queue, so calling this function usually means you will
189			never be called again.
190	root	1.1
191			=cut
192
193	root	1.22	=item cede
194	root	1.1
195	root	1.22	"Cede" to other processes. This function puts the current process into the
196			ready queue and calls C<schedule>, which has the effect of giving up the
197			current "timeslice" to other coroutines of the same or higher priority.
198	root	1.7
199	root	1.8	=cut
200
201	root	1.40	=item terminate [arg...]
202	root	1.7
203	pcg	1.59	Terminates the current process with the given status values (see L<cancel>).
204	root	1.13
205	root	1.1	=cut
206
207	root	1.8	sub terminate {
208	pcg	1.59	$current->cancel (@_);
209	root	1.1	}
210	root	1.6
211	root	1.8	=back
212
213			# dynamic methods
214
215			=head2 PROCESS METHODS
216
217			These are the methods you can call on process objects.
218	root	1.6
219	root	1.8	=over 4
220
221	root	1.13	=item new Coro \&sub [, @args...]
222	root	1.8
223			Create a new process and return it. When the sub returns the process
224	root	1.40	automatically terminates as if C<terminate> with the returned values were
225	root	1.41	called. To make the process run you must first put it into the ready queue
226			by calling the ready method.
227	root	1.13
228	root	1.6	=cut
229
230	root	1.13	sub _newcoro {
231			terminate &{+shift};
232			}
233
234	root	1.8	sub new {
235			my $class = shift;
236			bless {
237	root	1.81	_coro_state => (new Coro::State \&_newcoro, @_),
238	root	1.8	}, $class;
239			}
240	root	1.6
241	root	1.8	=item $process->ready
242	root	1.1
243	root	1.39	Put the given process into the ready queue.
244	root	1.1
245	root	1.8	=cut
246	root	1.28
247	pcg	1.59	=item $process->cancel (arg...)
248	root	1.28
249	root	1.79	Terminates the given process and makes it return the given arguments as
250	pcg	1.59	status (default: the empty list).
251	root	1.28
252			=cut
253
254			sub cancel {
255	pcg	1.59	my $self = shift;
256			$self->{status} = [@_];
257			push @destroy, $self;
258	root	1.28	$manager->ready;
259	pcg	1.59	&schedule if $current == $self;
260	root	1.40	}
261
262			=item $process->join
263
264			Wait until the coroutine terminates and return any values given to the
265	pcg	1.59	C<terminate> or C<cancel> functions. C<join> can be called multiple times
266			from multiple processes.
267	root	1.40
268			=cut
269
270			sub join {
271			my $self = shift;
272			unless ($self->{status}) {
273			push @{$self->{join}}, $current;
274			&schedule;
275			}
276			wantarray ? @{$self->{status}} : $self->{status}[0];
277	root	1.31	}
278
279	root	1.82	=item $oldprio = $process->prio ($newprio)
280	root	1.31
281	root	1.41	Sets (or gets, if the argument is missing) the priority of the
282			process. Higher priority processes get run before lower priority
283	root	1.52	processes. Priorities are small signed integers (currently -4 .. +3),
284	root	1.41	that you can refer to using PRIO_xxx constants (use the import tag :prio
285			to get then):
286	root	1.31
287			PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
288			3 > 1 > 0 > -1 > -3 > -4
289
290			# set priority to HIGH
291			current->prio(PRIO_HIGH);
292
293			The idle coroutine ($Coro::idle) always has a lower priority than any
294			existing coroutine.
295
296			Changing the priority of the current process will take effect immediately,
297			but changing the priority of processes in the ready queue (but not
298			running) will only take effect after the next schedule (of that
299			process). This is a bug that will be fixed in some future version.
300
301			=cut
302
303			sub prio {
304	root	1.82	shift->{_coro_state}->prio (@_)
305	root	1.31	}
306
307	root	1.82	=item $newprio = $process->nice ($change)
308	root	1.31
309			Similar to C<prio>, but subtract the given value from the priority (i.e.
310			higher values mean lower priority, just as in unix).
311
312			=cut
313
314			sub nice {
315	root	1.82	shift->{_coro_state}->nice (@_)
316	root	1.41	}
317
318	root	1.82	=item $olddesc = $process->desc ($newdesc)
319	root	1.41
320			Sets (or gets in case the argument is missing) the description for this
321			process. This is just a free-form string you can associate with a process.
322
323			=cut
324
325			sub desc {
326			my $old = $_[0]{desc};
327			$_[0]{desc} = $_[1] if @_ > 1;
328			$old;
329	root	1.8	}
330	root	1.1
331	root	1.8	=back
332	root	1.2
333	root	1.8	=cut
334	root	1.2
335	root	1.8	1;
336	root	1.14
337	root	1.17	=head1 BUGS/LIMITATIONS
338	root	1.14
339	root	1.52	- you must make very sure that no coro is still active on global
340	root	1.53	destruction. very bad things might happen otherwise (usually segfaults).
341	root	1.52
342			- this module is not thread-safe. You should only ever use this module
343			from the same thread (this requirement might be losened in the future
344			to allow per-thread schedulers, but Coro::State does not yet allow
345			this).
346	root	1.9
347			=head1 SEE ALSO
348
349	root	1.67	Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.
350
351			Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
352
353			Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
354
355			Embedding: L<Coro:MakeMaker>
356	root	1.1
357			=head1 AUTHOR
358
359	root	1.66	Marc Lehmann <schmorp@schmorp.de>
360	root	1.64	http://home.schmorp.de/
361	root	1.1
362			=cut
363