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 qw(Coro::State Exporter);

our $idle;    # idle handler
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).

This variable is B<strictly> I<read-only>. It is provided for performance
reasons. If performance is not essentiel you are encouraged to use the
C<Coro::current> function instead.

=cut

# maybe some other module used Coro::Specific before...
if ($current) {
   $main->{specific} = $current->{specific};
}

$current = $main;

sub current() { $current }

=item $idle

A callback that is called whenever the scheduler finds no ready coroutines
to run. The default implementation prints "FATAL: deadlock detected" and
exits.

This hook is overwritten by modules such as C<Coro::Timer> and
C<Coro::Event> to wait on an external event that hopefully wakes up some
coroutine.

=cut

$idle = 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).
         $coro->_clone_state_from ($manager);
      }
      &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;

   $class->SUPER::new (\&_newcoro, @_)
}

=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.

=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).

=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:	1.83
Committed:	Fri Nov 24 15:34:33 2006 UTC (17 years, 6 months ago) by root
Branch:	MAIN
CVS Tags:	stack_sharing
Changes since 1.82:	+21 -25 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	1.83	use base qw(Coro::State Exporter);
41	pcg	1.55
42	root	1.83	our $idle; # idle handler
43	root	1.71	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 $current (or as function: current)
99	root	1.1
100	root	1.83	The current coroutine (the last coroutine switched to). The initial value
101			is C<$main> (of course).
102
103			This variable is B<strictly> I<read-only>. It is provided for performance
104			reasons. If performance is not essentiel you are encouraged to use the
105			C<Coro::current> function instead.
106	root	1.1
107	root	1.8	=cut
108
109			# maybe some other module used Coro::Specific before...
110			if ($current) {
111			$main->{specific} = $current->{specific};
112	root	1.1	}
113
114	pcg	1.55	$current = $main;
115	root	1.19
116			sub current() { $current }
117	root	1.9
118			=item $idle
119
120	root	1.83	A callback that is called whenever the scheduler finds no ready coroutines
121			to run. The default implementation prints "FATAL: deadlock detected" and
122			exits.
123
124			This hook is overwritten by modules such as C<Coro::Timer> and
125			C<Coro::Event> to wait on an external event that hopefully wakes up some
126			coroutine.
127	root	1.9
128			=cut
129
130	root	1.83	$idle = sub {
131	root	1.9	print STDERR "FATAL: deadlock detected\n";
132	root	1.83	exit (51);
133	root	1.9	};
134	root	1.8
135	root	1.24	# this coroutine is necessary because a coroutine
136			# cannot destroy itself.
137			my @destroy;
138	root	1.38	my $manager;
139			$manager = new Coro sub {
140	pcg	1.57	while () {
141	root	1.37	# by overwriting the state object with the manager we destroy it
142			# while still being able to schedule this coroutine (in case it has
143			# been readied multiple times. this is harmless since the manager
144			# can be called as many times as neccessary and will always
145			# remove itself from the runqueue
146	root	1.40	while (@destroy) {
147			my $coro = pop @destroy;
148			$coro->{status} \|\|= [];
149			$_->ready for @{delete $coro->{join} \|\| []};
150	pcg	1.59
151	root	1.83	# the next line destroys the coro state, but keeps the
152	pcg	1.59	# process itself intact (we basically make it a zombie
153			# process that always runs the manager thread, so it's possible
154			# to transfer() to this process).
155	root	1.83	$coro->_clone_state_from ($manager);
156	root	1.40	}
157	root	1.24	&schedule;
158			}
159			};
160
161	root	1.8	# static methods. not really.
162	root	1.43
163			=back
164	root	1.8
165			=head2 STATIC METHODS
166
167			Static methods are actually functions that operate on the current process only.
168
169			=over 4
170
171	root	1.13	=item async { ... } [@args...]
172	root	1.8
173			Create a new asynchronous process and return it's process object
174			(usually unused). When the sub returns the new process is automatically
175			terminated.
176
177	root	1.79	When the coroutine dies, the program will exit, just as in the main
178			program.
179
180	root	1.13	# create a new coroutine that just prints its arguments
181			async {
182			print "@_\n";
183			} 1,2,3,4;
184
185	root	1.8	=cut
186
187	root	1.13	sub async(&@) {
188			my $pid = new Coro @_;
189	root	1.24	$manager->ready; # this ensures that the stack is cloned from the manager
190	root	1.11	$pid->ready;
191			$pid;
192	root	1.8	}
193	root	1.1
194	root	1.8	=item schedule
195	root	1.6
196	root	1.8	Calls the scheduler. Please note that the current process will not be put
197			into the ready queue, so calling this function usually means you will
198			never be called again.
199	root	1.1
200			=cut
201
202	root	1.22	=item cede
203	root	1.1
204	root	1.22	"Cede" to other processes. This function puts the current process into the
205			ready queue and calls C<schedule>, which has the effect of giving up the
206			current "timeslice" to other coroutines of the same or higher priority.
207	root	1.7
208	root	1.8	=cut
209
210	root	1.40	=item terminate [arg...]
211	root	1.7
212	pcg	1.59	Terminates the current process with the given status values (see L<cancel>).
213	root	1.13
214	root	1.1	=cut
215
216	root	1.8	sub terminate {
217	pcg	1.59	$current->cancel (@_);
218	root	1.1	}
219	root	1.6
220	root	1.8	=back
221
222			# dynamic methods
223
224			=head2 PROCESS METHODS
225
226			These are the methods you can call on process objects.
227	root	1.6
228	root	1.8	=over 4
229
230	root	1.13	=item new Coro \&sub [, @args...]
231	root	1.8
232			Create a new process and return it. When the sub returns the process
233	root	1.40	automatically terminates as if C<terminate> with the returned values were
234	root	1.41	called. To make the process run you must first put it into the ready queue
235			by calling the ready method.
236	root	1.13
237	root	1.6	=cut
238
239	root	1.13	sub _newcoro {
240			terminate &{+shift};
241			}
242
243	root	1.8	sub new {
244			my $class = shift;
245	root	1.83
246			$class->SUPER::new (\&_newcoro, @_)
247	root	1.8	}
248	root	1.6
249	root	1.8	=item $process->ready
250	root	1.1
251	root	1.39	Put the given process into the ready queue.
252	root	1.1
253	root	1.8	=cut
254	root	1.28
255	pcg	1.59	=item $process->cancel (arg...)
256	root	1.28
257	root	1.79	Terminates the given process and makes it return the given arguments as
258	pcg	1.59	status (default: the empty list).
259	root	1.28
260			=cut
261
262			sub cancel {
263	pcg	1.59	my $self = shift;
264			$self->{status} = [@_];
265			push @destroy, $self;
266	root	1.28	$manager->ready;
267	pcg	1.59	&schedule if $current == $self;
268	root	1.40	}
269
270			=item $process->join
271
272			Wait until the coroutine terminates and return any values given to the
273	pcg	1.59	C<terminate> or C<cancel> functions. C<join> can be called multiple times
274			from multiple processes.
275	root	1.40
276			=cut
277
278			sub join {
279			my $self = shift;
280			unless ($self->{status}) {
281			push @{$self->{join}}, $current;
282			&schedule;
283			}
284			wantarray ? @{$self->{status}} : $self->{status}[0];
285	root	1.31	}
286
287	root	1.82	=item $oldprio = $process->prio ($newprio)
288	root	1.31
289	root	1.41	Sets (or gets, if the argument is missing) the priority of the
290			process. Higher priority processes get run before lower priority
291	root	1.52	processes. Priorities are small signed integers (currently -4 .. +3),
292	root	1.41	that you can refer to using PRIO_xxx constants (use the import tag :prio
293			to get then):
294	root	1.31
295			PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
296			3 > 1 > 0 > -1 > -3 > -4
297
298			# set priority to HIGH
299			current->prio(PRIO_HIGH);
300
301			The idle coroutine ($Coro::idle) always has a lower priority than any
302			existing coroutine.
303
304			Changing the priority of the current process will take effect immediately,
305			but changing the priority of processes in the ready queue (but not
306			running) will only take effect after the next schedule (of that
307			process). This is a bug that will be fixed in some future version.
308
309	root	1.82	=item $newprio = $process->nice ($change)
310	root	1.31
311			Similar to C<prio>, but subtract the given value from the priority (i.e.
312			higher values mean lower priority, just as in unix).
313
314	root	1.82	=item $olddesc = $process->desc ($newdesc)
315	root	1.41
316			Sets (or gets in case the argument is missing) the description for this
317			process. This is just a free-form string you can associate with a process.
318
319			=cut
320
321			sub desc {
322			my $old = $_[0]{desc};
323			$_[0]{desc} = $_[1] if @_ > 1;
324			$old;
325	root	1.8	}
326	root	1.1
327	root	1.8	=back
328	root	1.2
329	root	1.8	=cut
330	root	1.2
331	root	1.8	1;
332	root	1.14
333	root	1.17	=head1 BUGS/LIMITATIONS
334	root	1.14
335	root	1.52	- you must make very sure that no coro is still active on global
336	root	1.53	destruction. very bad things might happen otherwise (usually segfaults).
337	root	1.52
338			- this module is not thread-safe. You should only ever use this module
339			from the same thread (this requirement might be losened in the future
340			to allow per-thread schedulers, but Coro::State does not yet allow
341			this).
342	root	1.9
343			=head1 SEE ALSO
344
345	root	1.67	Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.
346
347			Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
348
349			Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
350
351			Embedding: L<Coro:MakeMaker>
352	root	1.1
353			=head1 AUTHOR
354
355	root	1.66	Marc Lehmann <schmorp@schmorp.de>
356	root	1.64	http://home.schmorp.de/
357	root	1.1
358			=cut
359