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;

use strict;
no warnings "uninitialized";

use Coro::State;

use base qw(Coro::State Exporter);

our $idle;    # idle handler
our $main;    # main coroutine
our $current; # current coroutine

our $VERSION = '2.5';

our @EXPORT = qw(async cede schedule terminate current);
our %EXPORT_TAGS = (
      prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
);
our @EXPORT_OK = @{$EXPORT_TAGS{prio}};

{
   my @async;
   my $init;

   # this way of handling attributes simply is NOT scalable ;()
   sub import {
      no strict 'refs';

      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).

This variable is B<strictly> I<read-only>. It is provided for performance
reasons. If performance is not essentiel you are encouraged to use the
C<Coro::current> function instead.

=cut

# maybe some other module used Coro::Specific before...
if ($current) {
   $main->{specific} = $current->{specific};
}

$current = $main;

sub current() { $current }

=item $idle

A callback that is called whenever the scheduler finds no ready coroutines
to run. The default implementation prints "FATAL: deadlock detected" and
exits.

This hook is overwritten by modules such as C<Coro::Timer> and
C<Coro::Event> to wait on an external event that hopefully wakes up some
coroutine.

=cut

$idle = 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).
         $coro->_clone_state_from ($manager);
      }
      &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.

When the coroutine dies, the program will exit, just as in the main
program.

   # 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 _new_coro {
#   $current->_clear_idle_sp; # set the idle sp on the following cede
   _set_cede_self;  # ensures that cede cede's us first
   cede;
   terminate &{+shift};
}

sub new {
   my $class = shift;

   $class->SUPER::new (\&_new_coro, @_)
}

=item $process->ready

Put the given process into the ready queue.

=cut

=item $process->cancel (arg...)

Terminates 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.

=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).

=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

Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.

Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.

Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.

Embedding: L<Coro:MakeMaker>

=head1 AUTHOR

 Marc Lehmann <schmorp@schmorp.de>
 http://home.schmorp.de/

=cut

Revision:	1.84
Committed:	Sat Nov 25 00:40:26 2006 UTC (17 years, 6 months ago) by root
Branch:	MAIN
Changes since 1.83:	+5 -2 lines
Log Message:	* empty log message *
#	User	Rev	Content
1	root	1.1	=head1 NAME
2
3	root	1.8	Coro - coroutine process abstraction
4	root	1.1
5			=head1 SYNOPSIS
6
7			use Coro;
8
9	root	1.8	async {
10			# some asynchronous thread of execution
11	root	1.2	};
12
13	root	1.8	# alternatively create an async process like this:
14	root	1.6
15	root	1.8	sub some_func : Coro {
16			# some more async code
17			}
18
19	root	1.22	cede;
20	root	1.2
21	root	1.1	=head1 DESCRIPTION
22
23	root	1.14	This module collection manages coroutines. Coroutines are similar to
24	root	1.42	threads but don't run in parallel.
25	root	1.14
26	root	1.20	In this module, coroutines are defined as "callchain + lexical variables
27	root	1.23	+ @_ + $_ + $@ + $^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	root	1.22
31	root	1.8	=cut
32
33			package Coro;
34
35	root	1.71	use strict;
36			no warnings "uninitialized";
37	root	1.36
38	root	1.8	use Coro::State;
39
40	root	1.83	use base qw(Coro::State Exporter);
41	pcg	1.55
42	root	1.83	our $idle; # idle handler
43	root	1.71	our $main; # main coroutine
44			our $current; # current coroutine
45	root	1.8
46	root	1.80	our $VERSION = '2.5';
47	root	1.8
48	root	1.71	our @EXPORT = qw(async cede schedule terminate current);
49			our %EXPORT_TAGS = (
50	root	1.31	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
51			);
52	root	1.71	our @EXPORT_OK = @{$EXPORT_TAGS{prio}};
53	root	1.8
54			{
55			my @async;
56	root	1.26	my $init;
57	root	1.8
58			# this way of handling attributes simply is NOT scalable ;()
59			sub import {
60	root	1.71	no strict 'refs';
61
62	root	1.8	Coro->export_to_level(1, @_);
63	root	1.71
64	root	1.8	my $old = *{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"}{CODE};
65			*{(caller)[0]."::MODIFY_CODE_ATTRIBUTES"} = sub {
66			my ($package, $ref) = (shift, shift);
67			my @attrs;
68			for (@_) {
69			if ($_ eq "Coro") {
70			push @async, $ref;
71	root	1.26	unless ($init++) {
72			eval q{
73			sub INIT {
74			&async(pop @async) while @async;
75			}
76			};
77			}
78	root	1.8	} else {
79	root	1.17	push @attrs, $_;
80	root	1.8	}
81			}
82	root	1.17	return $old ? $old->($package, $ref, @attrs) : @attrs;
83	root	1.8	};
84			}
85
86			}
87
88	root	1.43	=over 4
89
90	root	1.8	=item $main
91	root	1.2
92	root	1.8	This coroutine represents the main program.
93	root	1.1
94			=cut
95
96	pcg	1.55	$main = new Coro;
97	root	1.8
98	root	1.19	=item $current (or as function: current)
99	root	1.1
100	root	1.83	The current coroutine (the last coroutine switched to). The initial value
101			is C<$main> (of course).
102
103			This variable is B<strictly> I<read-only>. It is provided for performance
104			reasons. If performance is not essentiel you are encouraged to use the
105			C<Coro::current> function instead.
106	root	1.1
107	root	1.8	=cut
108
109			# maybe some other module used Coro::Specific before...
110			if ($current) {
111			$main->{specific} = $current->{specific};
112	root	1.1	}
113
114	pcg	1.55	$current = $main;
115	root	1.19
116			sub current() { $current }
117	root	1.9
118			=item $idle
119
120	root	1.83	A callback that is called whenever the scheduler finds no ready coroutines
121			to run. The default implementation prints "FATAL: deadlock detected" and
122			exits.
123
124			This hook is overwritten by modules such as C<Coro::Timer> and
125			C<Coro::Event> to wait on an external event that hopefully wakes up some
126			coroutine.
127	root	1.9
128			=cut
129
130	root	1.83	$idle = sub {
131	root	1.9	print STDERR "FATAL: deadlock detected\n";
132	root	1.83	exit (51);
133	root	1.9	};
134	root	1.8
135	root	1.24	# this coroutine is necessary because a coroutine
136			# cannot destroy itself.
137			my @destroy;
138	root	1.38	my $manager;
139			$manager = new Coro sub {
140	pcg	1.57	while () {
141	root	1.37	# by overwriting the state object with the manager we destroy it
142			# while still being able to schedule this coroutine (in case it has
143			# been readied multiple times. this is harmless since the manager
144			# can be called as many times as neccessary and will always
145			# remove itself from the runqueue
146	root	1.40	while (@destroy) {
147			my $coro = pop @destroy;
148			$coro->{status} \|\|= [];
149			$_->ready for @{delete $coro->{join} \|\| []};
150	pcg	1.59
151	root	1.83	# the next line destroys the coro state, but keeps the
152	pcg	1.59	# process itself intact (we basically make it a zombie
153			# process that always runs the manager thread, so it's possible
154			# to transfer() to this process).
155	root	1.83	$coro->_clone_state_from ($manager);
156	root	1.40	}
157	root	1.24	&schedule;
158			}
159			};
160
161	root	1.8	# static methods. not really.
162	root	1.43
163			=back
164	root	1.8
165			=head2 STATIC METHODS
166
167			Static methods are actually functions that operate on the current process only.
168
169			=over 4
170
171	root	1.13	=item async { ... } [@args...]
172	root	1.8
173			Create a new asynchronous process and return it's process object
174			(usually unused). When the sub returns the new process is automatically
175			terminated.
176
177	root	1.79	When the coroutine dies, the program will exit, just as in the main
178			program.
179
180	root	1.13	# create a new coroutine that just prints its arguments
181			async {
182			print "@_\n";
183			} 1,2,3,4;
184
185	root	1.8	=cut
186
187	root	1.13	sub async(&@) {
188			my $pid = new Coro @_;
189	root	1.24	$manager->ready; # this ensures that the stack is cloned from the manager
190	root	1.11	$pid->ready;
191			$pid;
192	root	1.8	}
193	root	1.1
194	root	1.8	=item schedule
195	root	1.6
196	root	1.8	Calls the scheduler. Please note that the current process will not be put
197			into the ready queue, so calling this function usually means you will
198			never be called again.
199	root	1.1
200			=cut
201
202	root	1.22	=item cede
203	root	1.1
204	root	1.22	"Cede" to other processes. This function puts the current process into the
205			ready queue and calls C<schedule>, which has the effect of giving up the
206			current "timeslice" to other coroutines of the same or higher priority.
207	root	1.7
208	root	1.8	=cut
209
210	root	1.40	=item terminate [arg...]
211	root	1.7
212	pcg	1.59	Terminates the current process with the given status values (see L<cancel>).
213	root	1.13
214	root	1.1	=cut
215
216	root	1.8	sub terminate {
217	pcg	1.59	$current->cancel (@_);
218	root	1.1	}
219	root	1.6
220	root	1.8	=back
221
222			# dynamic methods
223
224			=head2 PROCESS METHODS
225
226			These are the methods you can call on process objects.
227	root	1.6
228	root	1.8	=over 4
229
230	root	1.13	=item new Coro \&sub [, @args...]
231	root	1.8
232			Create a new process and return it. When the sub returns the process
233	root	1.40	automatically terminates as if C<terminate> with the returned values were
234	root	1.41	called. To make the process run you must first put it into the ready queue
235			by calling the ready method.
236	root	1.13
237	root	1.6	=cut
238
239	root	1.84	sub _new_coro {
240			# $current->_clear_idle_sp; # set the idle sp on the following cede
241			_set_cede_self; # ensures that cede cede's us first
242			cede;
243	root	1.13	terminate &{+shift};
244			}
245
246	root	1.8	sub new {
247			my $class = shift;
248	root	1.83
249	root	1.84	$class->SUPER::new (\&_new_coro, @_)
250	root	1.8	}
251	root	1.6
252	root	1.8	=item $process->ready
253	root	1.1
254	root	1.39	Put the given process into the ready queue.
255	root	1.1
256	root	1.8	=cut
257	root	1.28
258	pcg	1.59	=item $process->cancel (arg...)
259	root	1.28
260	root	1.79	Terminates the given process and makes it return the given arguments as
261	pcg	1.59	status (default: the empty list).
262	root	1.28
263			=cut
264
265			sub cancel {
266	pcg	1.59	my $self = shift;
267			$self->{status} = [@_];
268			push @destroy, $self;
269	root	1.28	$manager->ready;
270	pcg	1.59	&schedule if $current == $self;
271	root	1.40	}
272
273			=item $process->join
274
275			Wait until the coroutine terminates and return any values given to the
276	pcg	1.59	C<terminate> or C<cancel> functions. C<join> can be called multiple times
277			from multiple processes.
278	root	1.40
279			=cut
280
281			sub join {
282			my $self = shift;
283			unless ($self->{status}) {
284			push @{$self->{join}}, $current;
285			&schedule;
286			}
287			wantarray ? @{$self->{status}} : $self->{status}[0];
288	root	1.31	}
289
290	root	1.82	=item $oldprio = $process->prio ($newprio)
291	root	1.31
292	root	1.41	Sets (or gets, if the argument is missing) the priority of the
293			process. Higher priority processes get run before lower priority
294	root	1.52	processes. Priorities are small signed integers (currently -4 .. +3),
295	root	1.41	that you can refer to using PRIO_xxx constants (use the import tag :prio
296			to get then):
297	root	1.31
298			PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
299			3 > 1 > 0 > -1 > -3 > -4
300
301			# set priority to HIGH
302			current->prio(PRIO_HIGH);
303
304			The idle coroutine ($Coro::idle) always has a lower priority than any
305			existing coroutine.
306
307			Changing the priority of the current process will take effect immediately,
308			but changing the priority of processes in the ready queue (but not
309			running) will only take effect after the next schedule (of that
310			process). This is a bug that will be fixed in some future version.
311
312	root	1.82	=item $newprio = $process->nice ($change)
313	root	1.31
314			Similar to C<prio>, but subtract the given value from the priority (i.e.
315			higher values mean lower priority, just as in unix).
316
317	root	1.82	=item $olddesc = $process->desc ($newdesc)
318	root	1.41
319			Sets (or gets in case the argument is missing) the description for this
320			process. This is just a free-form string you can associate with a process.
321
322			=cut
323
324			sub desc {
325			my $old = $_[0]{desc};
326			$_[0]{desc} = $_[1] if @_ > 1;
327			$old;
328	root	1.8	}
329	root	1.1
330	root	1.8	=back
331	root	1.2
332	root	1.8	=cut
333	root	1.2
334	root	1.8	1;
335	root	1.14
336	root	1.17	=head1 BUGS/LIMITATIONS
337	root	1.14
338	root	1.52	- you must make very sure that no coro is still active on global
339	root	1.53	destruction. very bad things might happen otherwise (usually segfaults).
340	root	1.52
341			- this module is not thread-safe. You should only ever use this module
342			from the same thread (this requirement might be losened in the future
343			to allow per-thread schedulers, but Coro::State does not yet allow
344			this).
345	root	1.9
346			=head1 SEE ALSO
347
348	root	1.67	Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.
349
350			Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
351
352			Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
353
354			Embedding: L<Coro:MakeMaker>
355	root	1.1
356			=head1 AUTHOR
357
358	root	1.66	Marc Lehmann <schmorp@schmorp.de>
359	root	1.64	http://home.schmorp.de/
360	root	1.1
361			=cut
362