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;

BEGIN { eval { require warnings } && warnings->unimport ("uninitialized") }

use Coro::State;

use vars qw($idle $main $current);

use base Exporter;

$VERSION = 0.95;

@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;
      };
   }

}

=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} || []};
         $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.

Future versions of this function will allow result arguments.

=cut

sub terminate {
   $current->{status} = [@_];
   $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 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

Like C<terminate>, but terminates the specified process instead.

=cut

sub cancel {
   push @destroy, $_[0];
   $manager->ready;
   &schedule if $current == $_[0];
}

=item $process->join

Wait until the coroutine terminates and return any values given to the
C<terminate> function. 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

L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>,
L<Coro::Signal>, L<Coro::State>, L<Coro::Timer>, L<Coro::Event>,
L<Coro::L<Coro::RWLock>, Handle>, L<Coro::Socket>.

=head1 AUTHOR

 Marc Lehmann <pcg@goof.com>
 http://www.goof.com/pcg/marc/

=cut

Revision:	1.58
Committed:	Fri Feb 13 23:17:41 2004 UTC (20 years, 3 months ago) by pcg
Branch:	MAIN
Changes since 1.57:	+1 -1 lines
Log Message:	* empty log message *
#	Content
1	=head1 NAME
2
3	Coro - coroutine process abstraction
4
5	=head1 SYNOPSIS
6
7	use Coro;
8
9	async {
10	# some asynchronous thread of execution
11	};
12
13	# alternatively create an async process like this:
14
15	sub some_func : Coro {
16	# some more async code
17	}
18
19	cede;
20
21	=head1 DESCRIPTION
22
23	This module collection manages coroutines. Coroutines are similar to
24	threads but don't run in parallel.
25
26	In this module, coroutines are defined as "callchain + lexical variables
27	+ @_ + $_ + $@ + $^W + C stack), that is, a coroutine has it's own
28	callchain, it's own set of lexicals and it's own set of perl's most
29	important global variables.
30
31	=cut
32
33	package Coro;
34
35	BEGIN { eval { require warnings } && warnings->unimport ("uninitialized") }
36
37	use Coro::State;
38
39	use vars qw($idle $main $current);
40
41	use base Exporter;
42
43	$VERSION = 0.95;
44
45	@EXPORT = qw(async cede schedule terminate current);
46	%EXPORT_TAGS = (
47	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
48	);
49	@EXPORT_OK = @{$EXPORT_TAGS{prio}};
50
51	{
52	my @async;
53	my $init;
54
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, $ref;
65	unless ($init++) {
66	eval q{
67	sub INIT {
68	&async(pop @async) while @async;
69	}
70	};
71	}
72	} else {
73	push @attrs, $_;
74	}
75	}
76	return $old ? $old->($package, $ref, @attrs) : @attrs;
77	};
78	}
79
80	}
81
82	=over 4
83
84	=item $main
85
86	This coroutine represents the main program.
87
88	=cut
89
90	$main = new Coro;
91
92	=item $current (or as function: current)
93
94	The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course).
95
96	=cut
97
98	# maybe some other module used Coro::Specific before...
99	if ($current) {
100	$main->{specific} = $current->{specific};
101	}
102
103	$current = $main;
104
105	sub current() { $current }
106
107	=item $idle
108
109	The coroutine to switch to when no other coroutine is running. The default
110	implementation prints "FATAL: deadlock detected" and exits.
111
112	=cut
113
114	# should be done using priorities :(
115	$idle = new Coro sub {
116	print STDERR "FATAL: deadlock detected\n";
117	exit(51);
118	};
119
120	# this coroutine is necessary because a coroutine
121	# cannot destroy itself.
122	my @destroy;
123	my $manager;
124	$manager = new Coro sub {
125	while () {
126	# by overwriting the state object with the manager we destroy it
127	# while still being able to schedule this coroutine (in case it has
128	# been readied multiple times. this is harmless since the manager
129	# can be called as many times as neccessary and will always
130	# remove itself from the runqueue
131	while (@destroy) {
132	my $coro = pop @destroy;
133	$coro->{status} \|\|= [];
134	$_->ready for @{delete $coro->{join} \|\| []};
135	$coro->{_coro_state} = $manager->{_coro_state};
136	}
137	&schedule;
138	}
139	};
140
141	# static methods. not really.
142
143	=back
144
145	=head2 STATIC METHODS
146
147	Static methods are actually functions that operate on the current process only.
148
149	=over 4
150
151	=item async { ... } [@args...]
152
153	Create a new asynchronous process and return it's process object
154	(usually unused). When the sub returns the new process is automatically
155	terminated.
156
157	# create a new coroutine that just prints its arguments
158	async {
159	print "@_\n";
160	} 1,2,3,4;
161
162	=cut
163
164	sub async(&@) {
165	my $pid = new Coro @_;
166	$manager->ready; # this ensures that the stack is cloned from the manager
167	$pid->ready;
168	$pid;
169	}
170
171	=item schedule
172
173	Calls the scheduler. Please note that the current process will not be put
174	into the ready queue, so calling this function usually means you will
175	never be called again.
176
177	=cut
178
179	=item cede
180
181	"Cede" to other processes. This function puts the current process into the
182	ready queue and calls C<schedule>, which has the effect of giving up the
183	current "timeslice" to other coroutines of the same or higher priority.
184
185	=cut
186
187	=item terminate [arg...]
188
189	Terminates the current process.
190
191	Future versions of this function will allow result arguments.
192
193	=cut
194
195	sub terminate {
196	$current->{status} = [@_];
197	$current->cancel;
198	&schedule;
199	die; # NORETURN
200	}
201
202	=back
203
204	# dynamic methods
205
206	=head2 PROCESS METHODS
207
208	These are the methods you can call on process objects.
209
210	=over 4
211
212	=item new Coro \&sub [, @args...]
213
214	Create a new process and return it. When the sub returns the process
215	automatically terminates as if C<terminate> with the returned values were
216	called. To make the process run you must first put it into the ready queue
217	by calling the ready method.
218
219	=cut
220
221	sub _newcoro {
222	terminate &{+shift};
223	}
224
225	sub new {
226	my $class = shift;
227	bless {
228	_coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
229	}, $class;
230	}
231
232	=item $process->ready
233
234	Put the given process into the ready queue.
235
236	=cut
237
238	=item $process->cancel
239
240	Like C<terminate>, but terminates the specified process instead.
241
242	=cut
243
244	sub cancel {
245	push @destroy, $_[0];
246	$manager->ready;
247	&schedule if $current == $_[0];
248	}
249
250	=item $process->join
251
252	Wait until the coroutine terminates and return any values given to the
253	C<terminate> function. C<join> can be called multiple times from multiple
254	processes.
255
256	=cut
257
258	sub join {
259	my $self = shift;
260	unless ($self->{status}) {
261	push @{$self->{join}}, $current;
262	&schedule;
263	}
264	wantarray ? @{$self->{status}} : $self->{status}[0];
265	}
266
267	=item $oldprio = $process->prio($newprio)
268
269	Sets (or gets, if the argument is missing) the priority of the
270	process. Higher priority processes get run before lower priority
271	processes. Priorities are small signed integers (currently -4 .. +3),
272	that you can refer to using PRIO_xxx constants (use the import tag :prio
273	to get then):
274
275	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
276	3 > 1 > 0 > -1 > -3 > -4
277
278	# set priority to HIGH
279	current->prio(PRIO_HIGH);
280
281	The idle coroutine ($Coro::idle) always has a lower priority than any
282	existing coroutine.
283
284	Changing the priority of the current process will take effect immediately,
285	but changing the priority of processes in the ready queue (but not
286	running) will only take effect after the next schedule (of that
287	process). This is a bug that will be fixed in some future version.
288
289	=cut
290
291	sub prio {
292	my $old = $_[0]{prio};
293	$_[0]{prio} = $_[1] if @_ > 1;
294	$old;
295	}
296
297	=item $newprio = $process->nice($change)
298
299	Similar to C<prio>, but subtract the given value from the priority (i.e.
300	higher values mean lower priority, just as in unix).
301
302	=cut
303
304	sub nice {
305	$_[0]{prio} -= $_[1];
306	}
307
308	=item $olddesc = $process->desc($newdesc)
309
310	Sets (or gets in case the argument is missing) the description for this
311	process. This is just a free-form string you can associate with a process.
312
313	=cut
314
315	sub desc {
316	my $old = $_[0]{desc};
317	$_[0]{desc} = $_[1] if @_ > 1;
318	$old;
319	}
320
321	=back
322
323	=cut
324
325	1;
326
327	=head1 BUGS/LIMITATIONS
328
329	- you must make very sure that no coro is still active on global
330	destruction. very bad things might happen otherwise (usually segfaults).
331
332	- this module is not thread-safe. You should only ever use this module
333	from the same thread (this requirement might be losened in the future
334	to allow per-thread schedulers, but Coro::State does not yet allow
335	this).
336
337	=head1 SEE ALSO
338
339	L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>,
340	L<Coro::Signal>, L<Coro::State>, L<Coro::Timer>, L<Coro::Event>,
341	L<Coro::L<Coro::RWLock>, Handle>, L<Coro::Socket>.
342
343	=head1 AUTHOR
344
345	Marc Lehmann <pcg@goof.com>
346	http://www.goof.com/pcg/marc/
347
348	=cut
349