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 = 0.97;

@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} || []};

         # 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

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:	1.61
Committed:	Fri May 14 13:25:08 2004 UTC (20 years ago) by pcg
Branch:	MAIN
Changes since 1.60:	+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	$VERSION = 0.97;
44
45	@EXPORT = qw(async cede schedule terminate current);
46	%EXPORT_TAGS = (
47	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
48	);
49	@EXPORT_OK = @{$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
136	# the next line destroys the _coro_state, but keeps the
137	# process itself intact (we basically make it a zombie
138	# process that always runs the manager thread, so it's possible
139	# to transfer() to this process).
140	$coro->{_coro_state} = $manager->{_coro_state};
141	}
142	&schedule;
143	}
144	};
145
146	# static methods. not really.
147
148	=back
149
150	=head2 STATIC METHODS
151
152	Static methods are actually functions that operate on the current process only.
153
154	=over 4
155
156	=item async { ... } [@args...]
157
158	Create a new asynchronous process and return it's process object
159	(usually unused). When the sub returns the new process is automatically
160	terminated.
161
162	# create a new coroutine that just prints its arguments
163	async {
164	print "@_\n";
165	} 1,2,3,4;
166
167	=cut
168
169	sub async(&@) {
170	my $pid = new Coro @_;
171	$manager->ready; # this ensures that the stack is cloned from the manager
172	$pid->ready;
173	$pid;
174	}
175
176	=item schedule
177
178	Calls the scheduler. Please note that the current process will not be put
179	into the ready queue, so calling this function usually means you will
180	never be called again.
181
182	=cut
183
184	=item cede
185
186	"Cede" to other processes. This function puts the current process into the
187	ready queue and calls C<schedule>, which has the effect of giving up the
188	current "timeslice" to other coroutines of the same or higher priority.
189
190	=cut
191
192	=item terminate [arg...]
193
194	Terminates the current process with the given status values (see L<cancel>).
195
196	=cut
197
198	sub terminate {
199	$current->cancel (@_);
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 (arg...)
239
240	Temrinates the given process and makes it return the given arguments as
241	status (default: the empty list).
242
243	=cut
244
245	sub cancel {
246	my $self = shift;
247	$self->{status} = [@_];
248	push @destroy, $self;
249	$manager->ready;
250	&schedule if $current == $self;
251	}
252
253	=item $process->join
254
255	Wait until the coroutine terminates and return any values given to the
256	C<terminate> or C<cancel> functions. C<join> can be called multiple times
257	from multiple processes.
258
259	=cut
260
261	sub join {
262	my $self = shift;
263	unless ($self->{status}) {
264	push @{$self->{join}}, $current;
265	&schedule;
266	}
267	wantarray ? @{$self->{status}} : $self->{status}[0];
268	}
269
270	=item $oldprio = $process->prio($newprio)
271
272	Sets (or gets, if the argument is missing) the priority of the
273	process. Higher priority processes get run before lower priority
274	processes. Priorities are small signed integers (currently -4 .. +3),
275	that you can refer to using PRIO_xxx constants (use the import tag :prio
276	to get then):
277
278	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
279	3 > 1 > 0 > -1 > -3 > -4
280
281	# set priority to HIGH
282	current->prio(PRIO_HIGH);
283
284	The idle coroutine ($Coro::idle) always has a lower priority than any
285	existing coroutine.
286
287	Changing the priority of the current process will take effect immediately,
288	but changing the priority of processes in the ready queue (but not
289	running) will only take effect after the next schedule (of that
290	process). This is a bug that will be fixed in some future version.
291
292	=cut
293
294	sub prio {
295	my $old = $_[0]{prio};
296	$_[0]{prio} = $_[1] if @_ > 1;
297	$old;
298	}
299
300	=item $newprio = $process->nice($change)
301
302	Similar to C<prio>, but subtract the given value from the priority (i.e.
303	higher values mean lower priority, just as in unix).
304
305	=cut
306
307	sub nice {
308	$_[0]{prio} -= $_[1];
309	}
310
311	=item $olddesc = $process->desc($newdesc)
312
313	Sets (or gets in case the argument is missing) the description for this
314	process. This is just a free-form string you can associate with a process.
315
316	=cut
317
318	sub desc {
319	my $old = $_[0]{desc};
320	$_[0]{desc} = $_[1] if @_ > 1;
321	$old;
322	}
323
324	=back
325
326	=cut
327
328	1;
329
330	=head1 BUGS/LIMITATIONS
331
332	- you must make very sure that no coro is still active on global
333	destruction. very bad things might happen otherwise (usually segfaults).
334
335	- this module is not thread-safe. You should only ever use this module
336	from the same thread (this requirement might be losened in the future
337	to allow per-thread schedulers, but Coro::State does not yet allow
338	this).
339
340	=head1 SEE ALSO
341
342	L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>,
343	L<Coro::Signal>, L<Coro::State>, L<Coro::Timer>, L<Coro::Event>,
344	L<Coro::L<Coro::RWLock>, Handle>, L<Coro::Socket>.
345
346	=head1 AUTHOR
347
348	Marc Lehmann <pcg@goof.com>
349	http://www.goof.com/pcg/marc/
350
351	=cut
352