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 = 0.652;

@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

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.

=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;

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 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
   or "panic: top_env").

 - 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::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:	1.52
Committed:	Tue May 27 00:26:34 2003 UTC (21 years ago) by root
Branch:	MAIN
Changes since 1.51:	+9 -6 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	$VERSION = 0.652;
42
43	@EXPORT = qw(async cede schedule terminate current);
44	%EXPORT_TAGS = (
45	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
46	);
47	@EXPORT_OK = @{$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	=over 4
81
82	=item $main
83
84	This coroutine represents the main program.
85
86	=cut
87
88	our $main = new Coro;
89
90	=item $current (or as function: current)
91
92	The current coroutine (the last coroutine switched to). The initial value is C<$main> (of course).
93
94	=cut
95
96	# maybe some other module used Coro::Specific before...
97	if ($current) {
98	$main->{specific} = $current->{specific};
99	}
100
101	our $current = $main;
102
103	sub current() { $current }
104
105	=item $idle
106
107	The coroutine to switch to when no other coroutine is running. The default
108	implementation prints "FATAL: deadlock detected" and exits.
109
110	=cut
111
112	# should be done using priorities :(
113	our $idle = new Coro sub {
114	print STDERR "FATAL: deadlock detected\n";
115	exit(51);
116	};
117
118	# this coroutine is necessary because a coroutine
119	# cannot destroy itself.
120	my @destroy;
121	my $manager;
122	$manager = new Coro sub {
123	while() {
124	# by overwriting the state object with the manager we destroy it
125	# while still being able to schedule this coroutine (in case it has
126	# been readied multiple times. this is harmless since the manager
127	# can be called as many times as neccessary and will always
128	# remove itself from the runqueue
129	while (@destroy) {
130	my $coro = pop @destroy;
131	$coro->{status} \|\|= [];
132	$_->ready for @{delete $coro->{join} \|\| []};
133	$coro->{_coro_state} = $manager->{_coro_state};
134	}
135	&schedule;
136	}
137	};
138
139	# static methods. not really.
140
141	=back
142
143	=head2 STATIC METHODS
144
145	Static methods are actually functions that operate on the current process only.
146
147	=over 4
148
149	=item async { ... } [@args...]
150
151	Create a new asynchronous process and return it's process object
152	(usually unused). When the sub returns the new process is automatically
153	terminated.
154
155	# create a new coroutine that just prints its arguments
156	async {
157	print "@_\n";
158	} 1,2,3,4;
159
160	The coderef you submit MUST NOT be a closure that refers to variables
161	in an outer scope. This does NOT work. Pass arguments into it instead.
162
163	=cut
164
165	sub async(&@) {
166	my $pid = new Coro @_;
167	$manager->ready; # this ensures that the stack is cloned from the manager
168	$pid->ready;
169	$pid;
170	}
171
172	=item schedule
173
174	Calls the scheduler. Please note that the current process will not be put
175	into the ready queue, so calling this function usually means you will
176	never be called again.
177
178	=cut
179
180	=item cede
181
182	"Cede" to other processes. This function puts the current process into the
183	ready queue and calls C<schedule>, which has the effect of giving up the
184	current "timeslice" to other coroutines of the same or higher priority.
185
186	=cut
187
188	=item terminate [arg...]
189
190	Terminates the current process.
191
192	Future versions of this function will allow result arguments.
193
194	=cut
195
196	sub terminate {
197	$current->{status} = [@_];
198	$current->cancel;
199	&schedule;
200	die; # NORETURN
201	}
202
203	=back
204
205	# dynamic methods
206
207	=head2 PROCESS METHODS
208
209	These are the methods you can call on process objects.
210
211	=over 4
212
213	=item new Coro \&sub [, @args...]
214
215	Create a new process and return it. When the sub returns the process
216	automatically terminates as if C<terminate> with the returned values were
217	called. To make the process run you must first put it into the ready queue
218	by calling the ready method.
219
220	=cut
221
222	sub _newcoro {
223	terminate &{+shift};
224	}
225
226	sub new {
227	my $class = shift;
228	bless {
229	_coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
230	}, $class;
231	}
232
233	=item $process->ready
234
235	Put the given process into the ready queue.
236
237	=cut
238
239	=item $process->cancel
240
241	Like C<terminate>, but terminates the specified process instead.
242
243	=cut
244
245	sub cancel {
246	push @destroy, $_[0];
247	$manager->ready;
248	&schedule if $current == $_[0];
249	}
250
251	=item $process->join
252
253	Wait until the coroutine terminates and return any values given to the
254	C<terminate> function. C<join> can be called multiple times from multiple
255	processes.
256
257	=cut
258
259	sub join {
260	my $self = shift;
261	unless ($self->{status}) {
262	push @{$self->{join}}, $current;
263	&schedule;
264	}
265	wantarray ? @{$self->{status}} : $self->{status}[0];
266	}
267
268	=item $oldprio = $process->prio($newprio)
269
270	Sets (or gets, if the argument is missing) the priority of the
271	process. Higher priority processes get run before lower priority
272	processes. Priorities are small signed integers (currently -4 .. +3),
273	that you can refer to using PRIO_xxx constants (use the import tag :prio
274	to get then):
275
276	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
277	3 > 1 > 0 > -1 > -3 > -4
278
279	# set priority to HIGH
280	current->prio(PRIO_HIGH);
281
282	The idle coroutine ($Coro::idle) always has a lower priority than any
283	existing coroutine.
284
285	Changing the priority of the current process will take effect immediately,
286	but changing the priority of processes in the ready queue (but not
287	running) will only take effect after the next schedule (of that
288	process). This is a bug that will be fixed in some future version.
289
290	=cut
291
292	sub prio {
293	my $old = $_[0]{prio};
294	$_[0]{prio} = $_[1] if @_ > 1;
295	$old;
296	}
297
298	=item $newprio = $process->nice($change)
299
300	Similar to C<prio>, but subtract the given value from the priority (i.e.
301	higher values mean lower priority, just as in unix).
302
303	=cut
304
305	sub nice {
306	$_[0]{prio} -= $_[1];
307	}
308
309	=item $olddesc = $process->desc($newdesc)
310
311	Sets (or gets in case the argument is missing) the description for this
312	process. This is just a free-form string you can associate with a process.
313
314	=cut
315
316	sub desc {
317	my $old = $_[0]{desc};
318	$_[0]{desc} = $_[1] if @_ > 1;
319	$old;
320	}
321
322	=back
323
324	=cut
325
326	1;
327
328	=head1 BUGS/LIMITATIONS
329
330	- you must make very sure that no coro is still active on global
331	destruction. very bad things might happen otherwise (usually segfaults
332	or "panic: top_env").
333
334	- this module is not thread-safe. You should only ever use this module
335	from the same thread (this requirement might be losened in the future
336	to allow per-thread schedulers, but Coro::State does not yet allow
337	this).
338
339	=head1 SEE ALSO
340
341	L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>,
342	L<Coro::Signal>, L<Coro::State>, L<Coro::Event>, L<Coro::RWLock>,
343	L<Coro::Handle>, L<Coro::Socket>.
344
345	=head1 AUTHOR
346
347	Marc Lehmann <pcg@goof.com>
348	http://www.goof.com/pcg/marc/
349
350	=cut
351