Coro/Coro/Storable.pm

=head1 NAME

Coro::Storable - offer a more fine-grained Storable interface

=head1 SYNOPSIS

 use Coro::Storable;

=head1 DESCRIPTION

This module implements a few functions from the Storable module in a way
so that it cede's more often. Some applications (such as the Crossfire
game server) sometimes need to load large Storable objects without
blocking the server for a long time.

As it seems that Storable is not reentrant, this module also serialises
calls to freeze and thaw between coroutines.

=head1 FUNCTIONS

=over 4

=item $ref = thaw $pst

Retrieve an object from the given $pst, which must have been created with
C<Coro::Storable::freeze> or C<Storable::store_fd>/C<Storable::store>
(sorry, but Storable uses incompatible formats for disk/mem objects).

This works by calling C<Coro::cede> for every 512 bytes read in.

=item $pst = freeze $ref

Freeze the given scalar into a Storable object. It uses the same format as
C<Storable::nstore_fd> (note the C<n>).

This works by calling C<Coro::cede> for every write that Storable
issues. Unfortunately, Storable often makes many very small writes, so it
is rather inefficient. But it does keep the latency low.

=back

=cut

package Coro::Storable;

use strict;

use Coro ();
use Coro::Semaphore ();

use Storable;
use base "Exporter";

our $VERSION = '0.1';
our @EXPORT = qw(freeze thaw);

my $lock = new Coro::Semaphore;

sub freeze($) {
   my $guard = $lock->guard;

   open my $fh, ">:via(CoroCede)", \my $buf
      or die "cannot open pst via CoroCede: $!";
   Storable::nstore_fd $_[0], $fh;
   $buf
}

sub thaw($) {
   my $guard = $lock->guard;

   open my $fh, "<:via(CoroCede)", \$_[0]
      or die "cannot open pst via CoroCede: $!";
   Storable::fd_retrieve $fh
}

package PerlIO::via::CoroCede;

# generic cede-on-read/write filtering layer

sub PUSHED {
   __PACKAGE__
}

sub FILL {
   Coro::cede;
   read $_[1], my $buf, 512
      or return undef;
   $buf
}

sub WRITE {
   Coro::cede;
   (print {$_[2]} $_[1]) ? length $_[1] : -1
}

1;

=head1 AUTHOR

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

=cut


Revision:	1.3
Committed:	Wed Apr 18 13:46:32 2007 UTC (17 years, 1 month ago) by root
Branch:	MAIN
Changes since 1.2:	+2 -1 lines
Log Message:	* empty log message *
#	User	Rev	Content
1	root	1.1	=head1 NAME
2
3			Coro::Storable - offer a more fine-grained Storable interface
4
5			=head1 SYNOPSIS
6
7			use Coro::Storable;
8
9			=head1 DESCRIPTION
10
11			This module implements a few functions from the Storable module in a way
12			so that it cede's more often. Some applications (such as the Crossfire
13			game server) sometimes need to load large Storable objects without
14			blocking the server for a long time.
15
16	root	1.2	As it seems that Storable is not reentrant, this module also serialises
17			calls to freeze and thaw between coroutines.
18
19	root	1.1	=head1 FUNCTIONS
20
21			=over 4
22
23			=item $ref = thaw $pst
24
25			Retrieve an object from the given $pst, which must have been created with
26			C<Coro::Storable::freeze> or C<Storable::store_fd>/C<Storable::store>
27			(sorry, but Storable uses incompatible formats for disk/mem objects).
28
29			This works by calling C<Coro::cede> for every 512 bytes read in.
30
31			=item $pst = freeze $ref
32
33			Freeze the given scalar into a Storable object. It uses the same format as
34			C<Storable::nstore_fd> (note the C<n>).
35
36			This works by calling C<Coro::cede> for every write that Storable
37			issues. Unfortunately, Storable often makes many very small writes, so it
38			is rather inefficient. But it does keep the latency low.
39
40			=back
41
42			=cut
43
44			package Coro::Storable;
45
46			use strict;
47
48			use Coro ();
49	root	1.2	use Coro::Semaphore ();
50	root	1.1
51			use Storable;
52			use base "Exporter";
53
54			our $VERSION = '0.1';
55			our @EXPORT = qw(freeze thaw);
56
57	root	1.2	my $lock = new Coro::Semaphore;
58
59	root	1.1	sub freeze($) {
60	root	1.2	my $guard = $lock->guard;
61
62	root	1.1	open my $fh, ">:via(CoroCede)", \my $buf
63			or die "cannot open pst via CoroCede: $!";
64			Storable::nstore_fd $_[0], $fh;
65			$buf
66			}
67
68			sub thaw($) {
69	root	1.2	my $guard = $lock->guard;
70
71	root	1.1	open my $fh, "<:via(CoroCede)", \$_[0]
72			or die "cannot open pst via CoroCede: $!";
73			Storable::fd_retrieve $fh
74			}
75
76			package PerlIO::via::CoroCede;
77
78			# generic cede-on-read/write filtering layer
79
80			sub PUSHED {
81			__PACKAGE__
82			}
83
84			sub FILL {
85			Coro::cede;
86	root	1.3	read $_[1], my $buf, 512
87			or return undef;
88	root	1.1	$buf
89			}
90
91			sub WRITE {
92			Coro::cede;
93			(print {$_[2]} $_[1]) ? length $_[1] : -1
94			}
95
96			1;
97
98			=head1 AUTHOR
99
100			Marc Lehmann <schmorp@schmorp.de>
101			http://home.schmorp.de/
102
103			=cut
104
105