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 = 1.5;

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} = $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.

   # 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 $_[0] && \&_newcoro, @_),
   }, $class;
}

=item $process->ready

Put the given process into the ready queue.

=cut

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

Temrinates 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 {
   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];
}

=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:	1.71
Committed:	Tue Nov 29 12:36:18 2005 UTC (18 years, 6 months ago) by root
Branch:	MAIN
CVS Tags:	rel-1_5
Changes since 1.70:	+13 -7 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	1.71	our $VERSION = 1.5;
47	root	1.8
48	root	1.71	our @EXPORT = qw(async cede schedule terminate current);
49			our %EXPORT_TAGS = (
50	root	1.31	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
51			);
52	root	1.71	our @EXPORT_OK = @{$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	1.40	$coro->{_coro_state} = $manager->{_coro_state};
147			}
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	1.13	# create a new coroutine that just prints its arguments
169			async {
170			print "@_\n";
171			} 1,2,3,4;
172
173	root	1.8	=cut
174
175	root	1.13	sub async(&@) {
176			my $pid = new Coro @_;
177	root	1.24	$manager->ready; # this ensures that the stack is cloned from the manager
178	root	1.11	$pid->ready;
179			$pid;
180	root	1.8	}
181	root	1.1
182	root	1.8	=item schedule
183	root	1.6
184	root	1.8	Calls the scheduler. Please note that the current process will not be put
185			into the ready queue, so calling this function usually means you will
186			never be called again.
187	root	1.1
188			=cut
189
190	root	1.22	=item cede
191	root	1.1
192	root	1.22	"Cede" to other processes. This function puts the current process into the
193			ready queue and calls C<schedule>, which has the effect of giving up the
194			current "timeslice" to other coroutines of the same or higher priority.
195	root	1.7
196	root	1.8	=cut
197
198	root	1.40	=item terminate [arg...]
199	root	1.7
200	pcg	1.59	Terminates the current process with the given status values (see L<cancel>).
201	root	1.13
202	root	1.1	=cut
203
204	root	1.8	sub terminate {
205	pcg	1.59	$current->cancel (@_);
206	root	1.1	}
207	root	1.6
208	root	1.8	=back
209
210			# dynamic methods
211
212			=head2 PROCESS METHODS
213
214			These are the methods you can call on process objects.
215	root	1.6
216	root	1.8	=over 4
217
218	root	1.13	=item new Coro \&sub [, @args...]
219	root	1.8
220			Create a new process and return it. When the sub returns the process
221	root	1.40	automatically terminates as if C<terminate> with the returned values were
222	root	1.41	called. To make the process run you must first put it into the ready queue
223			by calling the ready method.
224	root	1.13
225	root	1.6	=cut
226
227	root	1.13	sub _newcoro {
228			terminate &{+shift};
229			}
230
231	root	1.8	sub new {
232			my $class = shift;
233			bless {
234	root	1.13	_coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
235	root	1.8	}, $class;
236			}
237	root	1.6
238	root	1.8	=item $process->ready
239	root	1.1
240	root	1.39	Put the given process into the ready queue.
241	root	1.1
242	root	1.8	=cut
243	root	1.28
244	pcg	1.59	=item $process->cancel (arg...)
245	root	1.28
246	pcg	1.59	Temrinates the given process and makes it return the given arguments as
247			status (default: the empty list).
248	root	1.28
249			=cut
250
251			sub cancel {
252	pcg	1.59	my $self = shift;
253			$self->{status} = [@_];
254			push @destroy, $self;
255	root	1.28	$manager->ready;
256	pcg	1.59	&schedule if $current == $self;
257	root	1.40	}
258
259			=item $process->join
260
261			Wait until the coroutine terminates and return any values given to the
262	pcg	1.59	C<terminate> or C<cancel> functions. C<join> can be called multiple times
263			from multiple processes.
264	root	1.40
265			=cut
266
267			sub join {
268			my $self = shift;
269			unless ($self->{status}) {
270			push @{$self->{join}}, $current;
271			&schedule;
272			}
273			wantarray ? @{$self->{status}} : $self->{status}[0];
274	root	1.31	}
275
276			=item $oldprio = $process->prio($newprio)
277
278	root	1.41	Sets (or gets, if the argument is missing) the priority of the
279			process. Higher priority processes get run before lower priority
280	root	1.52	processes. Priorities are small signed integers (currently -4 .. +3),
281	root	1.41	that you can refer to using PRIO_xxx constants (use the import tag :prio
282			to get then):
283	root	1.31
284			PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
285			3 > 1 > 0 > -1 > -3 > -4
286
287			# set priority to HIGH
288			current->prio(PRIO_HIGH);
289
290			The idle coroutine ($Coro::idle) always has a lower priority than any
291			existing coroutine.
292
293			Changing the priority of the current process will take effect immediately,
294			but changing the priority of processes in the ready queue (but not
295			running) will only take effect after the next schedule (of that
296			process). This is a bug that will be fixed in some future version.
297
298			=cut
299
300			sub prio {
301			my $old = $_[0]{prio};
302			$_[0]{prio} = $_[1] if @_ > 1;
303			$old;
304			}
305
306			=item $newprio = $process->nice($change)
307
308			Similar to C<prio>, but subtract the given value from the priority (i.e.
309			higher values mean lower priority, just as in unix).
310
311			=cut
312
313			sub nice {
314			$_[0]{prio} -= $_[1];
315	root	1.41	}
316
317			=item $olddesc = $process->desc($newdesc)
318
319			Sets (or gets in case the argument is missing) the description for this
320			process. This is just a free-form string you can associate with a process.
321
322			=cut
323
324			sub desc {
325			my $old = $_[0]{desc};
326			$_[0]{desc} = $_[1] if @_ > 1;
327			$old;
328	root	1.8	}
329	root	1.1
330	root	1.8	=back
331	root	1.2
332	root	1.8	=cut
333	root	1.2
334	root	1.8	1;
335	root	1.14
336	root	1.17	=head1 BUGS/LIMITATIONS
337	root	1.14
338	root	1.52	- you must make very sure that no coro is still active on global
339	root	1.53	destruction. very bad things might happen otherwise (usually segfaults).
340	root	1.52
341			- this module is not thread-safe. You should only ever use this module
342			from the same thread (this requirement might be losened in the future
343			to allow per-thread schedulers, but Coro::State does not yet allow
344			this).
345	root	1.9
346			=head1 SEE ALSO
347
348	root	1.67	Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.
349
350			Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
351
352			Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
353
354			Embedding: L<Coro:MakeMaker>
355	root	1.1
356			=head1 AUTHOR
357
358	root	1.66	Marc Lehmann <schmorp@schmorp.de>
359	root	1.64	http://home.schmorp.de/
360	root	1.1
361			=cut
362