Coro/Coro.pm

=head1 NAME

Coro - coroutine process abstraction

=head1 SYNOPSIS

 use Coro;

 async {
    # some asynchronous thread of execution
 };

 # alternatively create an async coroutine 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 unblock_sub);
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
         # coroutine itself intact (we basically make it a zombie
         # coroutine that always runs the manager thread, so it's possible
         # to transfer() to this coroutine).
         $coro->_clone_state_from ($manager);
      }
      &schedule;
   }
};

# static methods. not really.

=back

=head2 STATIC METHODS

Static methods are actually functions that operate on the current coroutine only.

=over 4

=item async { ... } [@args...]

Create a new asynchronous coroutine and return it's coroutine object
(usually unused). When the sub returns the new coroutine 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 coroutine 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 coroutine
      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;
   }

=item cede

"Cede" to other coroutines. This function puts the current coroutine 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.

=item terminate [arg...]

Terminates the current coroutine with the given status values (see L<cancel>).

=cut

sub terminate {
   $current->cancel (@_);
}

=back

# dynamic methods

=head2 COROUTINE METHODS

These are the methods you can call on coroutine objects.

=over 4

=item new Coro \&sub [, @args...]

Create a new coroutine and return it. When the sub returns the coroutine
automatically terminates as if C<terminate> with the returned values were
called. To make the coroutine 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 = $coroutine->ready

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

=item $is_ready = $coroutine->is_ready

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

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

Terminates the given coroutine 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 $coroutine->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 coroutine.

=cut

sub join {
   my $self = shift;
   unless ($self->{status}) {
      push @{$self->{join}}, $current;
      &schedule;
   }
   wantarray ? @{$self->{status}} : $self->{status}[0];
}

=item $oldprio = $coroutine->prio ($newprio)

Sets (or gets, if the argument is missing) the priority of the
coroutine. Higher priority coroutines get run before lower priority
coroutines. 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 coroutine will take effect immediately,
but changing the priority of coroutines in the ready queue (but not
running) will only take effect after the next schedule (of that
coroutine). This is a bug that will be fixed in some future version.

=item $newprio = $coroutine->nice ($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 = $coroutine->desc ($newdesc)

Sets (or gets in case the argument is missing) the description for this
coroutine. This is just a free-form string you can associate with a coroutine.

=cut

sub desc {
   my $old = $_[0]{desc};
   $_[0]{desc} = $_[1] if @_ > 1;
   $old;
}

=back

=head2 UTILITY FUNCTIONS

=over 4

=item unblock_sub { ... }

This utility function takes a BLOCK or code reference and "unblocks" it,
returning the new coderef. This means that the new coderef will return
immediately without blocking, returning nothing, while the original code
ref will be called (with parameters) from within its own coroutine.

The reason this fucntion exists is that many event libraries (such as the
venerable L<Event|Event> module) are not coroutine-safe (a weaker form
of thread-safety). This means you must not block within event callbacks,
otherwise you might suffer from crashes or worse.

This function allows your callbacks to block by executing them in another
coroutine where it is safe to block. One example where blocking is handy
is when you use the L<Coro::AIO|Coro::AIO> functions to save results to
disk.

In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
creating event callbacks that want to block.

=cut

our @unblock_pool;
our @unblock_queue;
our $UNBLOCK_POOL_SIZE = 2;

sub unblock_handler_ {
   while () {
      my ($cb, @arg) = @{ delete $Coro::current->{arg} };
      $cb->(@arg);

      last if @unblock_pool >= $UNBLOCK_POOL_SIZE;
      push @unblock_pool, $Coro::current;
      schedule;
   }        
}           

our $unblock_scheduler = async {
   while () {
      while (my $cb = pop @unblock_queue) {
         my $handler = (pop @unblock_pool or new Coro \&unblock_handler_);
         $handler->{arg} = $cb;
         $handler->ready;
         cede;
      }

      schedule;
   }
};

sub unblock_sub(&) {
   my $cb = shift;

   sub {
      push @unblock_queue, [$cb, @_];
      $unblock_scheduler->ready;
   }
}

=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:	1.92
Committed:	Fri Dec 1 03:47:55 2006 UTC (17 years, 6 months ago) by root
Branch:	MAIN
Changes since 1.91:	+99 -38 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 coroutine 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 $VERSION = '3.0';
47
48	our @EXPORT = qw(async cede schedule terminate current unblock_sub);
49	our %EXPORT_TAGS = (
50	prio => [qw(PRIO_MAX PRIO_HIGH PRIO_NORMAL PRIO_LOW PRIO_IDLE PRIO_MIN)],
51	);
52	our @EXPORT_OK = @{$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, because the program has no other way to continue.
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 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
131	=cut
132
133	$idle = sub {
134	print STDERR "FATAL: deadlock detected\n";
135	exit (51);
136	};
137
138	# this coroutine is necessary because a coroutine
139	# cannot destroy itself.
140	my @destroy;
141	my $manager; $manager = new Coro sub {
142	while () {
143	# 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	while (@destroy) {
149	my $coro = pop @destroy;
150	$coro->{status} \|\|= [];
151	$_->ready for @{delete $coro->{join} \|\| []};
152
153	# the next line destroys the coro state, but keeps the
154	# coroutine itself intact (we basically make it a zombie
155	# coroutine that always runs the manager thread, so it's possible
156	# to transfer() to this coroutine).
157	$coro->_clone_state_from ($manager);
158	}
159	&schedule;
160	}
161	};
162
163	# static methods. not really.
164
165	=back
166
167	=head2 STATIC METHODS
168
169	Static methods are actually functions that operate on the current coroutine only.
170
171	=over 4
172
173	=item async { ... } [@args...]
174
175	Create a new asynchronous coroutine and return it's coroutine object
176	(usually unused). When the sub returns the new coroutine is automatically
177	terminated.
178
179	Calling C<exit> in a coroutine will not work correctly, so do not do that.
180
181	When the coroutine dies, the program will exit, just as in the main
182	program.
183
184	# create a new coroutine that just prints its arguments
185	async {
186	print "@_\n";
187	} 1,2,3,4;
188
189	=cut
190
191	sub async(&@) {
192	my $pid = new Coro @_;
193	$pid->ready;
194	$pid
195	}
196
197	=item schedule
198
199	Calls the scheduler. Please note that the current coroutine will not be put
200	into the ready queue, so calling this function usually means you will
201	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 coroutine
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
223	=item cede
224
225	"Cede" to other coroutines. This function puts the current coroutine into the
226	ready queue and calls C<schedule>, which has the effect of giving up the
227	current "timeslice" to other coroutines of the same or higher priority.
228
229	=item terminate [arg...]
230
231	Terminates the current coroutine with the given status values (see L<cancel>).
232
233	=cut
234
235	sub terminate {
236	$current->cancel (@_);
237	}
238
239	=back
240
241	# dynamic methods
242
243	=head2 COROUTINE METHODS
244
245	These are the methods you can call on coroutine objects.
246
247	=over 4
248
249	=item new Coro \&sub [, @args...]
250
251	Create a new coroutine and return it. When the sub returns the coroutine
252	automatically terminates as if C<terminate> with the returned values were
253	called. To make the coroutine run you must first put it into the ready queue
254	by calling the ready method.
255
256	Calling C<exit> in a coroutine will not work correctly, so do not do that.
257
258	=cut
259
260	sub _new_coro {
261	terminate &{+shift};
262	}
263
264	sub new {
265	my $class = shift;
266
267	$class->SUPER::new (\&_new_coro, @_)
268	}
269
270	=item $success = $coroutine->ready
271
272	Put the given coroutine into the ready queue (according to it's priority)
273	and return true. If the coroutine is already in the ready queue, do nothing
274	and return false.
275
276	=item $is_ready = $coroutine->is_ready
277
278	Return wether the coroutine is currently the ready queue or not,
279
280	=item $coroutine->cancel (arg...)
281
282	Terminates the given coroutine and makes it return the given arguments as
283	status (default: the empty list).
284
285	=cut
286
287	sub cancel {
288	my $self = shift;
289	$self->{status} = [@_];
290	push @destroy, $self;
291	$manager->ready;
292	&schedule if $current == $self;
293	}
294
295	=item $coroutine->join
296
297	Wait until the coroutine terminates and return any values given to the
298	C<terminate> or C<cancel> functions. C<join> can be called multiple times
299	from multiple coroutine.
300
301	=cut
302
303	sub join {
304	my $self = shift;
305	unless ($self->{status}) {
306	push @{$self->{join}}, $current;
307	&schedule;
308	}
309	wantarray ? @{$self->{status}} : $self->{status}[0];
310	}
311
312	=item $oldprio = $coroutine->prio ($newprio)
313
314	Sets (or gets, if the argument is missing) the priority of the
315	coroutine. Higher priority coroutines get run before lower priority
316	coroutines. Priorities are small signed integers (currently -4 .. +3),
317	that you can refer to using PRIO_xxx constants (use the import tag :prio
318	to get then):
319
320	PRIO_MAX > PRIO_HIGH > PRIO_NORMAL > PRIO_LOW > PRIO_IDLE > PRIO_MIN
321	3 > 1 > 0 > -1 > -3 > -4
322
323	# set priority to HIGH
324	current->prio(PRIO_HIGH);
325
326	The idle coroutine ($Coro::idle) always has a lower priority than any
327	existing coroutine.
328
329	Changing the priority of the current coroutine will take effect immediately,
330	but changing the priority of coroutines in the ready queue (but not
331	running) will only take effect after the next schedule (of that
332	coroutine). This is a bug that will be fixed in some future version.
333
334	=item $newprio = $coroutine->nice ($change)
335
336	Similar to C<prio>, but subtract the given value from the priority (i.e.
337	higher values mean lower priority, just as in unix).
338
339	=item $olddesc = $coroutine->desc ($newdesc)
340
341	Sets (or gets in case the argument is missing) the description for this
342	coroutine. This is just a free-form string you can associate with a coroutine.
343
344	=cut
345
346	sub desc {
347	my $old = $_[0]{desc};
348	$_[0]{desc} = $_[1] if @_ > 1;
349	$old;
350	}
351
352	=back
353
354	=head2 UTILITY FUNCTIONS
355
356	=over 4
357
358	=item unblock_sub { ... }
359
360	This utility function takes a BLOCK or code reference and "unblocks" it,
361	returning the new coderef. This means that the new coderef will return
362	immediately without blocking, returning nothing, while the original code
363	ref will be called (with parameters) from within its own coroutine.
364
365	The reason this fucntion exists is that many event libraries (such as the
366	venerable L<Event\|Event> module) are not coroutine-safe (a weaker form
367	of thread-safety). This means you must not block within event callbacks,
368	otherwise you might suffer from crashes or worse.
369
370	This function allows your callbacks to block by executing them in another
371	coroutine where it is safe to block. One example where blocking is handy
372	is when you use the L<Coro::AIO\|Coro::AIO> functions to save results to
373	disk.
374
375	In short: simply use C<unblock_sub { ... }> instead of C<sub { ... }> when
376	creating event callbacks that want to block.
377
378	=cut
379
380	our @unblock_pool;
381	our @unblock_queue;
382	our $UNBLOCK_POOL_SIZE = 2;
383
384	sub unblock_handler_ {
385	while () {
386	my ($cb, @arg) = @{ delete $Coro::current->{arg} };
387	$cb->(@arg);
388
389	last if @unblock_pool >= $UNBLOCK_POOL_SIZE;
390	push @unblock_pool, $Coro::current;
391	schedule;
392	}
393	}
394
395	our $unblock_scheduler = async {
396	while () {
397	while (my $cb = pop @unblock_queue) {
398	my $handler = (pop @unblock_pool or new Coro \&unblock_handler_);
399	$handler->{arg} = $cb;
400	$handler->ready;
401	cede;
402	}
403
404	schedule;
405	}
406	};
407
408	sub unblock_sub(&) {
409	my $cb = shift;
410
411	sub {
412	push @unblock_queue, [$cb, @_];
413	$unblock_scheduler->ready;
414	}
415	}
416
417	=back
418
419	=cut
420
421	1;
422
423	=head1 BUGS/LIMITATIONS
424
425	- you must make very sure that no coro is still active on global
426	destruction. very bad things might happen otherwise (usually segfaults).
427
428	- this module is not thread-safe. You should only ever use this module
429	from the same thread (this requirement might be losened in the future
430	to allow per-thread schedulers, but Coro::State does not yet allow
431	this).
432
433	=head1 SEE ALSO
434
435	Support/Utility: L<Coro::Cont>, L<Coro::Specific>, L<Coro::State>, L<Coro::Util>.
436
437	Locking/IPC: L<Coro::Signal>, L<Coro::Channel>, L<Coro::Semaphore>, L<Coro::SemaphoreSet>, L<Coro::RWLock>.
438
439	Event/IO: L<Coro::Timer>, L<Coro::Event>, L<Coro::Handle>, L<Coro::Socket>, L<Coro::Select>.
440
441	Embedding: L<Coro:MakeMaker>
442
443	=head1 AUTHOR
444
445	Marc Lehmann <schmorp@schmorp.de>
446	http://home.schmorp.de/
447
448	=cut
449