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 *
#	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	use strict;
36	no warnings "uninitialized";
37
38	use Coro::State;
39
40	use base qw(Coro::State Exporter);
41
42	our $idle; # idle handler
43	our $main; # main coroutine
44	our $current; # current coroutine
45
46	our $VERSION = '2.5';
47
48	our @EXPORT = qw(async cede schedule terminate current);
49	our %EXPORT_TAGS = (
50	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
51	);
52	our @EXPORT_OK = @{$EXPORT_TAGS{prio}};
53
54	{
55	my @async;
56	my $init;
57
58	# this way of handling attributes simply is NOT scalable ;()
59	sub import {
60	no strict 'refs';
61
62	Coro->export_to_level(1, @_);
63
64	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, $ref;
71	unless ($init++) {
72	eval q{
73	sub INIT {
74	&async(pop @async) while @async;
75	}
76	};
77	}
78	} else {
79	push @attrs, $_;
80	}
81	}
82	return $old ? $old->($package, $ref, @attrs) : @attrs;
83	};
84	}
85
86	}
87
88	=over 4
89
90	=item $main
91
92	This coroutine represents the main program.
93
94	=cut
95
96	$main = new Coro;
97
98	=item $current (or as function: current)
99
100	The current coroutine (the last coroutine switched to). The initial value
101	is C<$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
107	=cut
108
109	# maybe some other module used Coro::Specific before...
110	if ($current) {
111	$main->{specific} = $current->{specific};
112	}
113
114	$current = $main;
115
116	sub current() { $current }
117
118	=item $idle
119
120	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
128	=cut
129
130	$idle = sub {
131	print STDERR "FATAL: deadlock detected\n";
132	exit (51);
133	};
134
135	# this coroutine is necessary because a coroutine
136	# cannot destroy itself.
137	my @destroy;
138	my $manager;
139	$manager = new Coro sub {
140	while () {
141	# 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	while (@destroy) {
147	my $coro = pop @destroy;
148	$coro->{status} \|\|= [];
149	$_->ready for @{delete $coro->{join} \|\| []};
150
151	# the next line destroys the coro state, but keeps the
152	# 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	$coro->_clone_state_from ($manager);
156	}
157	&schedule;
158	}
159	};
160
161	# static methods. not really.
162
163	=back
164
165	=head2 STATIC METHODS
166
167	Static methods are actually functions that operate on the current process only.
168
169	=over 4
170
171	=item async { ... } [@args...]
172
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	When the coroutine dies, the program will exit, just as in the main
178	program.
179
180	# create a new coroutine that just prints its arguments
181	async {
182	print "@_\n";
183	} 1,2,3,4;
184
185	=cut
186
187	sub async(&@) {
188	my $pid = new Coro @_;
189	$manager->ready; # this ensures that the stack is cloned from the manager
190	$pid->ready;
191	$pid;
192	}
193
194	=item schedule
195
196	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
200	=cut
201
202	=item cede
203
204	"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
208	=cut
209
210	=item terminate [arg...]
211
212	Terminates the current process with the given status values (see L<cancel>).
213
214	=cut
215
216	sub terminate {
217	$current->cancel (@_);
218	}
219
220	=back
221
222	# dynamic methods
223
224	=head2 PROCESS METHODS
225
226	These are the methods you can call on process objects.
227
228	=over 4
229
230	=item new Coro \&sub [, @args...]
231
232	Create a new process and return it. When the sub returns the process
233	automatically terminates as if C<terminate> with the returned values were
234	called. To make the process run you must first put it into the ready queue
235	by calling the ready method.
236
237	=cut
238
239	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	terminate &{+shift};
244	}
245
246	sub new {
247	my $class = shift;
248
249	$class->SUPER::new (\&_new_coro, @_)
250	}
251
252	=item $process->ready
253
254	Put the given process into the ready queue.
255
256	=cut
257
258	=item $process->cancel (arg...)
259
260	Terminates the given process and makes it return the given arguments as
261	status (default: the empty list).
262
263	=cut
264
265	sub cancel {
266	my $self = shift;
267	$self->{status} = [@_];
268	push @destroy, $self;
269	$manager->ready;
270	&schedule if $current == $self;
271	}
272
273	=item $process->join
274
275	Wait until the coroutine terminates and return any values given to the
276	C<terminate> or C<cancel> functions. C<join> can be called multiple times
277	from multiple processes.
278
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	}
289
290	=item $oldprio = $process->prio ($newprio)
291
292	Sets (or gets, if the argument is missing) the priority of the
293	process. Higher priority processes get run before lower priority
294	processes. Priorities are small signed integers (currently -4 .. +3),
295	that you can refer to using PRIO_xxx constants (use the import tag :prio
296	to get then):
297
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	=item $newprio = $process->nice ($change)
313
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	=item $olddesc = $process->desc ($newdesc)
318
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	}
329
330	=back
331
332	=cut
333
334	1;
335
336	=head1 BUGS/LIMITATIONS
337
338	- you must make very sure that no coro is still active on global
339	destruction. very bad things might happen otherwise (usually segfaults).
340
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
346	=head1 SEE ALSO
347
348	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
356	=head1 AUTHOR
357
358	Marc Lehmann <schmorp@schmorp.de>
359	http://home.schmorp.de/
360
361	=cut
362