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.

This module is still experimental, see the BUGS section below.

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 = 0.51;

@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 start the process you must first put it into the ready queue by
calling the ready method.

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 _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 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];
}

=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 must 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:	1.40
Committed:	Sun Oct 28 17:00:05 2001 UTC (22 years, 7 months ago) by root
Branch:	MAIN
Changes since 1.39:	+28 -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	This module is still experimental, see the BUGS section below.
27
28	In this module, coroutines are defined as "callchain + lexical variables
29	+ @_ + $_ + $@ + $^W + C stack), that is, a coroutine has it's own
30	callchain, it's own set of lexicals and it's own set of perl's most
31	important global variables.
32
33	=cut
34
35	package Coro;
36
37	no warnings qw(uninitialized);
38
39	use Coro::State;
40
41	use base Exporter;
42
43	$VERSION = 0.51;
44
45	@EXPORT = qw(async cede schedule terminate current);
46	%EXPORT_TAGS = (
47	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
48	);
49	@EXPORT_OK = @{$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	=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	=head2 STATIC METHODS
142
143	Static methods are actually functions that operate on the current process only.
144
145	=over 4
146
147	=item async { ... } [@args...]
148
149	Create a new asynchronous process and return it's process object
150	(usually unused). When the sub returns the new process is automatically
151	terminated.
152
153	# create a new coroutine that just prints its arguments
154	async {
155	print "@_\n";
156	} 1,2,3,4;
157
158	The coderef you submit MUST NOT be a closure that refers to variables
159	in an outer scope. This does NOT work. Pass arguments into it instead.
160
161	=cut
162
163	sub async(&@) {
164	my $pid = new Coro @_;
165	$manager->ready; # this ensures that the stack is cloned from the manager
166	$pid->ready;
167	$pid;
168	}
169
170	=item schedule
171
172	Calls the scheduler. Please note that the current process will not be put
173	into the ready queue, so calling this function usually means you will
174	never be called again.
175
176	=cut
177
178	=item cede
179
180	"Cede" to other processes. This function puts the current process into the
181	ready queue and calls C<schedule>, which has the effect of giving up the
182	current "timeslice" to other coroutines of the same or higher priority.
183
184	=cut
185
186	=item terminate [arg...]
187
188	Terminates the current process.
189
190	Future versions of this function will allow result arguments.
191
192	=cut
193
194	sub terminate {
195	$current->{status} = [@_];
196	$current->cancel;
197	&schedule;
198	die; # NORETURN
199	}
200
201	=back
202
203	# dynamic methods
204
205	=head2 PROCESS METHODS
206
207	These are the methods you can call on process objects.
208
209	=over 4
210
211	=item new Coro \&sub [, @args...]
212
213	Create a new process and return it. When the sub returns the process
214	automatically terminates as if C<terminate> with the returned values were
215	called. To start the process you must first put it into the ready queue by
216	calling the ready method.
217
218	The coderef you submit MUST NOT be a closure that refers to variables
219	in an outer scope. This does NOT work. Pass arguments into it instead.
220
221	=cut
222
223	sub _newcoro {
224	terminate &{+shift};
225	}
226
227	sub new {
228	my $class = shift;
229	bless {
230	_coro_state => (new Coro::State $_[0] && \&_newcoro, @_),
231	}, $class;
232	}
233
234	=item $process->ready
235
236	Put the given process into the ready queue.
237
238	=cut
239
240	=item $process->cancel
241
242	Like C<terminate>, but terminates the specified process instead.
243
244	=cut
245
246	sub cancel {
247	push @destroy, $_[0];
248	$manager->ready;
249	&schedule if $current == $_[0];
250	}
251
252	=item $process->join
253
254	Wait until the coroutine terminates and return any values given to the
255	C<terminate> function. C<join> can be called multiple times from multiple
256	processes.
257
258	=cut
259
260	sub join {
261	my $self = shift;
262	unless ($self->{status}) {
263	push @{$self->{join}}, $current;
264	&schedule;
265	}
266	wantarray ? @{$self->{status}} : $self->{status}[0];
267	}
268
269	=item $oldprio = $process->prio($newprio)
270
271	Sets the priority of the process. Higher priority processes get run before
272	lower priority processes. Priorities are smalled signed integer (currently
273	-4 .. +3), that you can refer to using PRIO_xxx constants (use the import
274	tag :prio 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	=back
310
311	=cut
312
313	1;
314
315	=head1 BUGS/LIMITATIONS
316
317	- you must make very sure that no coro is still active on global destruction.
318	very bad things might happen otherwise (usually segfaults).
319	- this module is not thread-safe. You must only ever use this module from
320	the same thread (this requirement might be loosened in the future to
321	allow per-thread schedulers, but Coro::State does not yet allow this).
322
323	=head1 SEE ALSO
324
325	L<Coro::Channel>, L<Coro::Cont>, L<Coro::Specific>, L<Coro::Semaphore>,
326	L<Coro::Signal>, L<Coro::State>, L<Coro::Event>, L<Coro::RWLock>,
327	L<Coro::Handle>, L<Coro::Socket>.
328
329	=head1 AUTHOR
330
331	Marc Lehmann <pcg@goof.com>
332	http://www.goof.com/pcg/marc/
333
334	=cut
335