Coro/Coro/State.pm

=head1 NAME

Coro::State - create and manage simple coroutines

=head1 SYNOPSIS

 use Coro::State;

 $new = new Coro::State sub {
    print "in coroutine (called with @_), switching back\n";
    $new->transfer($main);
    print "in coroutine again, switching back\n";
    $new->transfer($main);
 }, 5;

 $main = new Coro::State;

 print "in main, switching to coroutine\n";
 $main->transfer($new);
 print "back in main, switch to coroutine again\n";
 $main->transfer($new);
 print "back in main\n";

=head1 DESCRIPTION

This module implements coroutines. Coroutines, similar to continuations,
allow you to run more than one "thread of execution" in parallel. Unlike
threads this, only voluntary switching is used so locking problems are
greatly reduced.

This module provides only low-level functionality. See L<Coro> and related
modules for a more useful process abstraction including scheduling.

=head2 MEMORY CONSUMPTION

A newly created coroutine that has not been used only allocates a
relatively small (a few hundred bytes) structure. Only on the first
C<transfer> will perl stacks (a few k) and optionally C stack (4-16k) be
allocated. On systems supporting mmap a 128k stack is allocated, on the
assumption that the OS has on-demand virtual memory. All this is very
system-dependent. On my i686-pc-linux-gnu system this amounts to about 10k
per coroutine, 5k when the experimental context sharing is enabled.

=over 4

=cut

package Coro::State;

BEGIN {
   $VERSION = 0.5;

   require XSLoader;
   XSLoader::load Coro::State, $VERSION;
}

use base 'Exporter';

@EXPORT_OK = qw(SAVE_DEFAV SAVE_DEFSV SAVE_ERRSV SAVE_CCTXT);

=item $coro = new [$coderef] [, @args...]

Create a new coroutine and return it. The first C<transfer> call to this
coroutine will start execution at the given coderef. If the subroutine
returns it will be executed again.

If the coderef is omitted this function will create a new "empty"
coroutine, i.e. a coroutine that cannot be transfered to but can be used
to save the current coroutine in.

=cut

# this is called (or rather: goto'ed) for each and every
# new coroutine. IT MUST NEVER RETURN and should not call
# anything that changes the stacklevel (like eval).
sub initialize {
   my $proc = shift;
   eval {
      &$proc while 1;
   };
   if ($@) {
      print STDERR "FATAL: uncaught exception\n$@";
   }
   _exit 255;
}

sub new {
   my $class = shift;
   my $proc = shift || sub { die "tried to transfer to an empty coroutine" };
   bless _newprocess [$proc, @_], $class;
}

=item $prev->transfer($next,$flags)

Save the state of the current subroutine in C<$prev> and switch to the
coroutine saved in C<$next>.

The "state" of a subroutine includes the scope, i.e. lexical variables and
the current execution state. The C<$flags> value can be used to specify
that additional state be saved (and later restored), by C<||>-ing the
following constants together:

   Constant    Effect
   SAVE_DEFAV  save/restore @_
   SAVE_DEFSV  save/restore $_
   SAVE_ERRSV  save/restore $@
   SAVE_CCTXT  save/restore C-stack (you usually want this)

These constants are not exported by default. If you don't need any extra
additional state saved use C<0> as the flags value.

If you feel that something important is missing then tell me.  Also
remember that every function call that might call C<transfer> (such
as C<Coro::Channel::put>) might clobber any global and/or special
variables. Yes, this is by design ;) You can always create your own
process abstraction model that saves these variables.

The easiest way to do this is to create your own scheduling primitive like
this:

  sub schedule {
     local ($_, $@, ...);
     $old->transfer($new);
  }

IMPLEMENTORS NOTE: all Coro::State functions/methods expect either the
usual Coro::State object or a hashref with a key named "_coro_state" that
contains the real Coro::State object. That is, you can do:

  $obj->{_coro_state} = new Coro::State ...;
  Coro::State::transfer(..., $obj);

This exists mainly to ease subclassing (wether through @ISA or not).

=cut

=item Coro::State::flush

To be efficient (actually, to not be abysmaly slow), this module does
some fair amount of caching (a possibly complex structure for every
subroutine in use). If you don't use coroutines anymore or you want to
reclaim some memory then you can call this function which will flush all
internal caches. The caches will be rebuilt when needed so this is a safe
operation.

=cut

1;

=back

=head1 BUGS

This module has not yet been extensively tested. Expect segfaults and
specially memleaks.

This module is not thread-safe. You must only ever use this module from
the same thread (this requirenmnt might be loosened in the future).

=head1 SEE ALSO

L<Coro>.

=head1 AUTHOR

 Marc Lehmann <pcg@goof.com>
 http://www.goof.com/pcg/marc/

=cut

Revision:	1.17
Committed:	Sun Sep 16 01:34:36 2001 UTC (22 years, 8 months ago) by root
Branch:	MAIN
Changes since 1.16:	+1 -1 lines
Log Message:	* empty log message *
#	User	Rev	Content
1	root	1.1	=head1 NAME
2
3			Coro::State - create and manage simple coroutines
4
5			=head1 SYNOPSIS
6
7			use Coro::State;
8
9			$new = new Coro::State sub {
10	root	1.3	print "in coroutine (called with @_), switching back\n";
11	root	1.1	$new->transfer($main);
12			print "in coroutine again, switching back\n";
13			$new->transfer($main);
14	root	1.3	}, 5;
15	root	1.1
16			$main = new Coro::State;
17
18			print "in main, switching to coroutine\n";
19			$main->transfer($new);
20			print "back in main, switch to coroutine again\n";
21			$main->transfer($new);
22			print "back in main\n";
23
24			=head1 DESCRIPTION
25
26			This module implements coroutines. Coroutines, similar to continuations,
27			allow you to run more than one "thread of execution" in parallel. Unlike
28			threads this, only voluntary switching is used so locking problems are
29			greatly reduced.
30
31			This module provides only low-level functionality. See L<Coro> and related
32			modules for a more useful process abstraction including scheduling.
33
34	root	1.9	=head2 MEMORY CONSUMPTION
35
36			A newly created coroutine that has not been used only allocates a
37			relatively small (a few hundred bytes) structure. Only on the first
38			C<transfer> will perl stacks (a few k) and optionally C stack (4-16k) be
39			allocated. On systems supporting mmap a 128k stack is allocated, on the
40			assumption that the OS has on-demand virtual memory. All this is very
41			system-dependent. On my i686-pc-linux-gnu system this amounts to about 10k
42	root	1.11	per coroutine, 5k when the experimental context sharing is enabled.
43	root	1.9
44	root	1.1	=over 4
45
46			=cut
47
48			package Coro::State;
49
50			BEGIN {
51	root	1.17	$VERSION = 0.5;
52	root	1.1
53			require XSLoader;
54			XSLoader::load Coro::State, $VERSION;
55			}
56
57	root	1.5	use base 'Exporter';
58
59	root	1.9	@EXPORT_OK = qw(SAVE_DEFAV SAVE_DEFSV SAVE_ERRSV SAVE_CCTXT);
60	root	1.5
61	root	1.3	=item $coro = new [$coderef] [, @args...]
62	root	1.1
63			Create a new coroutine and return it. The first C<transfer> call to this
64	root	1.10	coroutine will start execution at the given coderef. If the subroutine
65	root	1.1	returns it will be executed again.
66
67			If the coderef is omitted this function will create a new "empty"
68			coroutine, i.e. a coroutine that cannot be transfered to but can be used
69			to save the current coroutine in.
70
71			=cut
72
73	root	1.12	# this is called (or rather: goto'ed) for each and every
74			# new coroutine. IT MUST NEVER RETURN and should not call
75			# anything that changes the stacklevel (like eval).
76	root	1.8	sub initialize {
77	root	1.3	my $proc = shift;
78	root	1.13	eval {
79			&$proc while 1;
80			};
81			if ($@) {
82			print STDERR "FATAL: uncaught exception\n$@";
83			}
84			_exit 255;
85	root	1.3	}
86
87	root	1.1	sub new {
88	root	1.3	my $class = shift;
89	root	1.4	my $proc = shift \|\| sub { die "tried to transfer to an empty coroutine" };
90	root	1.3	bless _newprocess [$proc, @_], $class;
91	root	1.1	}
92
93	root	1.10	=item $prev->transfer($next,$flags)
94	root	1.1
95			Save the state of the current subroutine in C<$prev> and switch to the
96			coroutine saved in C<$next>.
97
98	root	1.5	The "state" of a subroutine includes the scope, i.e. lexical variables and
99			the current execution state. The C<$flags> value can be used to specify
100	root	1.8	that additional state be saved (and later restored), by C<\|\|>-ing the
101			following constants together:
102	root	1.5
103	root	1.9	Constant Effect
104			SAVE_DEFAV save/restore @_
105			SAVE_DEFSV save/restore $_
106			SAVE_ERRSV save/restore $@
107			SAVE_CCTXT save/restore C-stack (you usually want this)
108	root	1.5
109	root	1.15	These constants are not exported by default. If you don't need any extra
110			additional state saved use C<0> as the flags value.
111	root	1.2
112	root	1.5	If you feel that something important is missing then tell me. Also
113	root	1.2	remember that every function call that might call C<transfer> (such
114			as C<Coro::Channel::put>) might clobber any global and/or special
115			variables. Yes, this is by design ;) You can always create your own
116			process abstraction model that saves these variables.
117	root	1.1
118	root	1.9	The easiest way to do this is to create your own scheduling primitive like
119			this:
120	root	1.1
121			sub schedule {
122			local ($_, $@, ...);
123			$old->transfer($new);
124			}
125
126			IMPLEMENTORS NOTE: all Coro::State functions/methods expect either the
127			usual Coro::State object or a hashref with a key named "_coro_state" that
128			contains the real Coro::State object. That is, you can do:
129
130			$obj->{_coro_state} = new Coro::State ...;
131			Coro::State::transfer(..., $obj);
132
133			This exists mainly to ease subclassing (wether through @ISA or not).
134
135			=cut
136
137	root	1.5	=item Coro::State::flush
138
139			To be efficient (actually, to not be abysmaly slow), this module does
140			some fair amount of caching (a possibly complex structure for every
141			subroutine in use). If you don't use coroutines anymore or you want to
142			reclaim some memory then you can call this function which will flush all
143			internal caches. The caches will be rebuilt when needed so this is a safe
144			operation.
145
146			=cut
147
148	root	1.1	1;
149
150			=back
151
152			=head1 BUGS
153
154			This module has not yet been extensively tested. Expect segfaults and
155			specially memleaks.
156	root	1.5
157			This module is not thread-safe. You must only ever use this module from
158			the same thread (this requirenmnt might be loosened in the future).
159	root	1.1
160			=head1 SEE ALSO
161
162			L<Coro>.
163
164			=head1 AUTHOR
165
166			Marc Lehmann <pcg@goof.com>
167			http://www.goof.com/pcg/marc/
168
169			=cut
170