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 = '3.0';

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, because the program has no other way to continue.

This hook is overwritten by modules such as C<Coro::Timer> and
C<Coro::Event> to wait on an external event that hopefully wake up a
coroutine so the scheduler can run it.

Please note that if your callback recursively invokes perl (e.g. for event
handlers), then it must be prepared to be called recursively.

=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.

Calling C<exit> in a coroutine will not work correctly, so do not do that.

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 @_;
   $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 unless something else (e.g. an event handler) calls
ready.

The canonical way to wait on external events is this:

   {
      # remember current process
      my $current = $Coro::current;

      # register a hypothetical event handler
      on_event_invoke sub {
         # wake up sleeping coroutine
         $current->ready;
         undef $current;
      };

      # call schedule until event occured.
      # in case we are woken up for other reasons
      # (current still defined), loop.
      Coro::schedule while $current;
   }

=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.

Calling C<exit> in a coroutine will not work correctly, so do not do that.

=cut

sub _new_coro {
   terminate &{+shift};
}

sub new {
   my $class = shift;

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

=item $success = $process->ready

Put the given process into the ready queue (according to it's priority)
and return true. If the process is already in the ready queue, do nothing
and return false.

=item $is_ready = $process->is_ready

Return wether the process is currently the ready queue or not,

=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:	1.91
Committed:	Fri Dec 1 02:17:37 2006 UTC (17 years, 6 months ago) by root
Branch:	MAIN
Changes since 1.90:	+27 -4 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	1.88	our $VERSION = '3.0';
47	root	1.8
48	root	1.71	our @EXPORT = qw(async cede schedule terminate current);
49			our %EXPORT_TAGS = (
50	root	1.31	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
51			);
52	root	1.71	our @EXPORT_OK = @{$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	root	1.91	exits, because the program has no other way to continue.
123	root	1.83
124			This hook is overwritten by modules such as C<Coro::Timer> and
125	root	1.91	C<Coro::Event> to wait on an external event that hopefully wake up a
126			coroutine so the scheduler can run it.
127
128			Please note that if your callback recursively invokes perl (e.g. for event
129			handlers), then it must be prepared to be called recursively.
130	root	1.9
131			=cut
132
133	root	1.83	$idle = sub {
134	root	1.9	print STDERR "FATAL: deadlock detected\n";
135	root	1.83	exit (51);
136	root	1.9	};
137	root	1.8
138	root	1.24	# this coroutine is necessary because a coroutine
139			# cannot destroy itself.
140			my @destroy;
141	root	1.86	my $manager; $manager = new Coro sub {
142	pcg	1.57	while () {
143	root	1.37	# by overwriting the state object with the manager we destroy it
144			# while still being able to schedule this coroutine (in case it has
145			# been readied multiple times. this is harmless since the manager
146			# can be called as many times as neccessary and will always
147			# remove itself from the runqueue
148	root	1.40	while (@destroy) {
149			my $coro = pop @destroy;
150			$coro->{status} \|\|= [];
151			$_->ready for @{delete $coro->{join} \|\| []};
152	pcg	1.59
153	root	1.83	# the next line destroys the coro state, but keeps the
154	pcg	1.59	# process itself intact (we basically make it a zombie
155			# process that always runs the manager thread, so it's possible
156			# to transfer() to this process).
157	root	1.83	$coro->_clone_state_from ($manager);
158	root	1.40	}
159	root	1.24	&schedule;
160			}
161			};
162
163	root	1.8	# static methods. not really.
164	root	1.43
165			=back
166	root	1.8
167			=head2 STATIC METHODS
168
169			Static methods are actually functions that operate on the current process only.
170
171			=over 4
172
173	root	1.13	=item async { ... } [@args...]
174	root	1.8
175			Create a new asynchronous process and return it's process object
176			(usually unused). When the sub returns the new process is automatically
177			terminated.
178
179	root	1.89	Calling C<exit> in a coroutine will not work correctly, so do not do that.
180
181	root	1.79	When the coroutine dies, the program will exit, just as in the main
182			program.
183
184	root	1.13	# create a new coroutine that just prints its arguments
185			async {
186			print "@_\n";
187			} 1,2,3,4;
188
189	root	1.8	=cut
190
191	root	1.13	sub async(&@) {
192			my $pid = new Coro @_;
193	root	1.11	$pid->ready;
194	root	1.85	$pid
195	root	1.8	}
196	root	1.1
197	root	1.8	=item schedule
198	root	1.6
199	root	1.8	Calls the scheduler. Please note that the current process will not be put
200			into the ready queue, so calling this function usually means you will
201	root	1.91	never be called again unless something else (e.g. an event handler) calls
202			ready.
203
204			The canonical way to wait on external events is this:
205
206			{
207			# remember current process
208			my $current = $Coro::current;
209
210			# register a hypothetical event handler
211			on_event_invoke sub {
212			# wake up sleeping coroutine
213			$current->ready;
214			undef $current;
215			};
216
217			# call schedule until event occured.
218			# in case we are woken up for other reasons
219			# (current still defined), loop.
220			Coro::schedule while $current;
221			}
222	root	1.1
223			=cut
224
225	root	1.22	=item cede
226	root	1.1
227	root	1.22	"Cede" to other processes. This function puts the current process into the
228			ready queue and calls C<schedule>, which has the effect of giving up the
229			current "timeslice" to other coroutines of the same or higher priority.
230	root	1.7
231	root	1.8	=cut
232
233	root	1.40	=item terminate [arg...]
234	root	1.7
235	pcg	1.59	Terminates the current process with the given status values (see L<cancel>).
236	root	1.13
237	root	1.1	=cut
238
239	root	1.8	sub terminate {
240	pcg	1.59	$current->cancel (@_);
241	root	1.1	}
242	root	1.6
243	root	1.8	=back
244
245			# dynamic methods
246
247			=head2 PROCESS METHODS
248
249			These are the methods you can call on process objects.
250	root	1.6
251	root	1.8	=over 4
252
253	root	1.13	=item new Coro \&sub [, @args...]
254	root	1.8
255			Create a new process and return it. When the sub returns the process
256	root	1.40	automatically terminates as if C<terminate> with the returned values were
257	root	1.41	called. To make the process run you must first put it into the ready queue
258			by calling the ready method.
259	root	1.13
260	root	1.89	Calling C<exit> in a coroutine will not work correctly, so do not do that.
261
262	root	1.6	=cut
263
264	root	1.84	sub _new_coro {
265	root	1.13	terminate &{+shift};
266			}
267
268	root	1.8	sub new {
269			my $class = shift;
270	root	1.83
271	root	1.84	$class->SUPER::new (\&_new_coro, @_)
272	root	1.8	}
273	root	1.6
274	root	1.90	=item $success = $process->ready
275	root	1.1
276	root	1.90	Put the given process into the ready queue (according to it's priority)
277			and return true. If the process is already in the ready queue, do nothing
278			and return false.
279	root	1.1
280	root	1.90	=item $is_ready = $process->is_ready
281
282			Return wether the process is currently the ready queue or not,
283	root	1.28
284	pcg	1.59	=item $process->cancel (arg...)
285	root	1.28
286	root	1.79	Terminates the given process and makes it return the given arguments as
287	pcg	1.59	status (default: the empty list).
288	root	1.28
289			=cut
290
291			sub cancel {
292	pcg	1.59	my $self = shift;
293			$self->{status} = [@_];
294			push @destroy, $self;
295	root	1.28	$manager->ready;
296	pcg	1.59	&schedule if $current == $self;
297	root	1.40	}
298
299			=item $process->join
300
301			Wait until the coroutine terminates and return any values given to the
302	pcg	1.59	C<terminate> or C<cancel> functions. C<join> can be called multiple times
303			from multiple processes.
304	root	1.40
305			=cut
306
307			sub join {
308			my $self = shift;
309			unless ($self->{status}) {
310			push @{$self->{join}}, $current;
311			&schedule;
312			}
313			wantarray ? @{$self->{status}} : $self->{status}[0];
314	root	1.31	}
315
316	root	1.82	=item $oldprio = $process->prio ($newprio)
317	root	1.31
318	root	1.41	Sets (or gets, if the argument is missing) the priority of the
319			process. Higher priority processes get run before lower priority
320	root	1.52	processes. Priorities are small signed integers (currently -4 .. +3),
321	root	1.41	that you can refer to using PRIO_xxx constants (use the import tag :prio
322			to get then):
323	root	1.31
324			PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
325			3 > 1 > 0 > -1 > -3 > -4
326
327			# set priority to HIGH
328			current->prio(PRIO_HIGH);
329
330			The idle coroutine ($Coro::idle) always has a lower priority than any
331			existing coroutine.
332
333			Changing the priority of the current process will take effect immediately,
334			but changing the priority of processes in the ready queue (but not
335			running) will only take effect after the next schedule (of that
336			process). This is a bug that will be fixed in some future version.
337
338	root	1.82	=item $newprio = $process->nice ($change)
339	root	1.31
340			Similar to C<prio>, but subtract the given value from the priority (i.e.
341			higher values mean lower priority, just as in unix).
342
343	root	1.82	=item $olddesc = $process->desc ($newdesc)
344	root	1.41
345			Sets (or gets in case the argument is missing) the description for this
346			process. This is just a free-form string you can associate with a process.
347
348			=cut
349
350			sub desc {
351			my $old = $_[0]{desc};
352			$_[0]{desc} = $_[1] if @_ > 1;
353			$old;
354	root	1.8	}
355	root	1.1
356	root	1.8	=back
357	root	1.2
358	root	1.8	=cut
359	root	1.2
360	root	1.8	1;
361	root	1.14
362	root	1.17	=head1 BUGS/LIMITATIONS
363	root	1.14
364	root	1.52	- you must make very sure that no coro is still active on global
365	root	1.53	destruction. very bad things might happen otherwise (usually segfaults).
366	root	1.52
367			- this module is not thread-safe. You should only ever use this module
368			from the same thread (this requirement might be losened in the future
369			to allow per-thread schedulers, but Coro::State does not yet allow
370			this).
371	root	1.9
372			=head1 SEE ALSO
373
374	root	1.67	Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.
375
376			Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
377
378			Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
379
380			Embedding: L<Coro:MakeMaker>
381	root	1.1
382			=head1 AUTHOR
383
384	root	1.66	Marc Lehmann <schmorp@schmorp.de>
385	root	1.64	http://home.schmorp.de/
386	root	1.1
387			=cut
388