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;

no warnings qw(uninitialized);

use Coro::State;

use base Exporter;

$VERSION = 0.52;

@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
      while (@destroy) {
         my $coro = pop @destroy;
         $coro->{status} ||= [];
         $_->ready for @{delete $coro->{join} || []};
         $coro->{_coro_state} = $manager->{_coro_state};
      }
      &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 [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 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];
}

=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 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:	1.42
Committed:	Tue Nov 6 20:37:20 2001 UTC (22 years, 7 months ago) by root
Branch:	MAIN
Changes since 1.41:	+2 -4 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	no warnings qw(uninitialized);
36
37	use Coro::State;
38
39	use base Exporter;
40
41	$VERSION = 0.52;
42
43	@EXPORT = qw(async cede schedule terminate current);
44	%EXPORT_TAGS = (
45	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
46	);
47	@EXPORT_OK = @{$EXPORT_TAGS{prio}};
48
49	{
50	my @async;
51	my $init;
52
53	# this way of handling attributes simply is NOT scalable ;()
54	sub import {
55	Coro->export_to_level(1, @_);
56	my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
57	*{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
58	my ($package, $ref) = (shift, shift);
59	my @attrs;
60	for (@_) {
61	if ($_ eq "Coro") {
62	push @async, $ref;
63	unless ($init++) {
64	eval q{
65	sub INIT {
66	&async(pop @async) while @async;
67	}
68	};
69	}
70	} else {
71	push @attrs, $_;
72	}
73	}
74	return $old ? $old->($package, $ref, @attrs) : @attrs;
75	};
76	}
77
78	}
79
80	=item $main
81
82	This coroutine represents the main program.
83
84	=cut
85
86	our $main = new Coro;
87
88	=item $current (or as function: current)
89
90	The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course).
91
92	=cut
93
94	# maybe some other module used Coro::Specific before...
95	if ($current) {
96	$main->{specific} = $current->{specific};
97	}
98
99	our $current = $main;
100
101	sub current() { $current }
102
103	=item $idle
104
105	The coroutine to switch to when no other coroutine is running. The default
106	implementation prints "FATAL: deadlock detected" and exits.
107
108	=cut
109
110	# should be done using priorities :(
111	our $idle = new Coro sub {
112	print STDERR "FATAL: deadlock detected\n";
113	exit(51);
114	};
115
116	# this coroutine is necessary because a coroutine
117	# cannot destroy itself.
118	my @destroy;
119	my $manager;
120	$manager = new Coro sub {
121	while() {
122	# by overwriting the state object with the manager we destroy it
123	# while still being able to schedule this coroutine (in case it has
124	# been readied multiple times. this is harmless since the manager
125	# can be called as many times as neccessary and will always
126	# remove itself from the runqueue
127	while (@destroy) {
128	my $coro = pop @destroy;
129	$coro->{status} \|\|= [];
130	$_->ready for @{delete $coro->{join} \|\| []};
131	$coro->{_coro_state} = $manager->{_coro_state};
132	}
133	&schedule;
134	}
135	};
136
137	# static methods. not really.
138
139	=head2 STATIC METHODS
140
141	Static methods are actually functions that operate on the current process only.
142
143	=over 4
144
145	=item async { ... } [@args...]
146
147	Create a new asynchronous process and return it's process object
148	(usually unused). When the sub returns the new process is automatically
149	terminated.
150
151	# create a new coroutine that just prints its arguments
152	async {
153	print "@_\n";
154	} 1,2,3,4;
155
156	The coderef you submit MUST NOT be a closure that refers to variables
157	in an outer scope. This does NOT work. Pass arguments into it instead.
158
159	=cut
160
161	sub async(&@) {
162	my $pid = new Coro @_;
163	$manager->ready; # this ensures that the stack is cloned from the manager
164	$pid->ready;
165	$pid;
166	}
167
168	=item schedule
169
170	Calls the scheduler. Please note that the current process will not be put
171	into the ready queue, so calling this function usually means you will
172	never be called again.
173
174	=cut
175
176	=item cede
177
178	"Cede" to other processes. This function puts the current process into the
179	ready queue and calls C<schedule>, which has the effect of giving up the
180	current "timeslice" to other coroutines of the same or higher priority.
181
182	=cut
183
184	=item terminate [arg...]
185
186	Terminates the current process.
187
188	Future versions of this function will allow result arguments.
189
190	=cut
191
192	sub terminate {
193	$current->{status} = [@_];
194	$current->cancel;
195	&schedule;
196	die; # NORETURN
197	}
198
199	=back
200
201	# dynamic methods
202
203	=head2 PROCESS METHODS
204
205	These are the methods you can call on process objects.
206
207	=over 4
208
209	=item new Coro \&sub [, @args...]
210
211	Create a new process and return it. When the sub returns the process
212	automatically terminates as if C<terminate> with the returned values were
213	called. To make the process run you must first put it into the ready queue
214	by calling the ready method.
215
216	=cut
217
218	sub _newcoro {
219	terminate &{+shift};
220	}
221
222	sub new {
223	my $class = shift;
224	bless {
225	_coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
226	}, $class;
227	}
228
229	=item $process->ready
230
231	Put the given process into the ready queue.
232
233	=cut
234
235	=item $process->cancel
236
237	Like C<terminate>, but terminates the specified process instead.
238
239	=cut
240
241	sub cancel {
242	push @destroy, $_[0];
243	$manager->ready;
244	&schedule if $current == $_[0];
245	}
246
247	=item $process->join
248
249	Wait until the coroutine terminates and return any values given to the
250	C<terminate> function. C<join> can be called multiple times from multiple
251	processes.
252
253	=cut
254
255	sub join {
256	my $self = shift;
257	unless ($self->{status}) {
258	push @{$self->{join}}, $current;
259	&schedule;
260	}
261	wantarray ? @{$self->{status}} : $self->{status}[0];
262	}
263
264	=item $oldprio = $process->prio($newprio)
265
266	Sets (or gets, if the argument is missing) the priority of the
267	process. Higher priority processes get run before lower priority
268	processes. Priorities are smalled signed integer (currently -4 .. +3),
269	that you can refer to using PRIO_xxx constants (use the import tag :prio
270	to get then):
271
272	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
273	3 > 1 > 0 > -1 > -3 > -4
274
275	# set priority to HIGH
276	current->prio(PRIO_HIGH);
277
278	The idle coroutine ($Coro::idle) always has a lower priority than any
279	existing coroutine.
280
281	Changing the priority of the current process will take effect immediately,
282	but changing the priority of processes in the ready queue (but not
283	running) will only take effect after the next schedule (of that
284	process). This is a bug that will be fixed in some future version.
285
286	=cut
287
288	sub prio {
289	my $old = $_[0]{prio};
290	$_[0]{prio} = $_[1] if @_ > 1;
291	$old;
292	}
293
294	=item $newprio = $process->nice($change)
295
296	Similar to C<prio>, but subtract the given value from the priority (i.e.
297	higher values mean lower priority, just as in unix).
298
299	=cut
300
301	sub nice {
302	$_[0]{prio} -= $_[1];
303	}
304
305	=item $olddesc = $process->desc($newdesc)
306
307	Sets (or gets in case the argument is missing) the description for this
308	process. This is just a free-form string you can associate with a process.
309
310	=cut
311
312	sub desc {
313	my $old = $_[0]{desc};
314	$_[0]{desc} = $_[1] if @_ > 1;
315	$old;
316	}
317
318	=back
319
320	=cut
321
322	1;
323
324	=head1 BUGS/LIMITATIONS
325
326	- you must make very sure that no coro is still active on global destruction.
327	very bad things might happen otherwise (usually segfaults).
328	- this module is not thread-safe. You should only ever use this module from
329	the same thread (this requirement might be loosened in the future to
330	allow per-thread schedulers, but Coro::State does not yet allow this).
331
332	=head1 SEE ALSO
333
334	L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>,
335	L<Coro::Signal>, L<Coro::State>, L<Coro::Event>, L<Coro::RWLock>,
336	L<Coro::Handle>, L<Coro::Socket>.
337
338	=head1 AUTHOR
339
340	Marc Lehmann <pcg@goof.com>
341	http://www.goof.com/pcg/marc/
342
343	=cut
344