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.

This is being implemented by using a perlio layer that feeds only small
amounts of data (512 bytes per call) into Storable, and C<Coro::cede>'ing
regularly (at most 1000 times per second by default, though).

As it seems that Storable is not reentrant, this module also serialises
calls to freeze and thaw between coroutines as necessary (for this to work
reliably you always have to use this module, however).

=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 4096 bytes read in.

=item $pst = freeze $ref

Freeze the given scalar into a Storable object. It uses the same format as
C<Storable::store_fd>.

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.

=item $pst = nfreeze $ref

Same as C<freeze> but is compatible to C<Storable::nstore_fd> (note the
C<n>).

=item $pst = blocking_freeze $ref

Same as C<freeze> but is guaranteed to block. This is useful e.g. in
C<Coro::Util::fork_eval> when you want to serialise a data structure
for use with the C<thaw> function for this module. You cannot use
C<Storable::freeze> for this as Storable uses incompatible formats for
memory and file images.

=item $pst = blocking_nfreeze $ref

Same as C<blocking_freeze> but uses C<nfreeze> internally.

=back

=cut

package Coro::Storable;

use strict;

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

use Storable;
use base "Exporter";

our $VERSION = '0.2';
our @EXPORT = qw(thaw freeze nfreeze blocking_freeze blocking_nfreeze);

my $lock = new Coro::Semaphore;

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

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

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

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

sub nfreeze($) {
   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 blocking_freeze {
   open my $fh, ">", \my $buf
         or die "cannot open pst: $!";
   Storable::store_fd $_[0], $fh;
   close $fh;

   $buf
}

sub blocking_nfreeze {
   open my $fh, ">", \my $buf
         or die "cannot open pst: $!";
   Storable::nstore_fd $_[0], $fh;
   close $fh;

   $buf
}

package PerlIO::via::CoroCede;

# generic cede-on-read/write filtering layer

use Time::HiRes ("time");

our $GRANULARITY = 0.001;

my $next_cede;

sub PUSHED {
   __PACKAGE__
}

sub FILL {
   if ($next_cede <= time) {
      $next_cede = time + $GRANULARITY; # calling time() twice usually is a net win
      Coro::cede;
   }

   read $_[1], my $buf, 512
      or return undef;

   $buf
}

sub WRITE {
   if ($next_cede <= (my $now = time)) {
      Coro::cede;
      $next_cede = $now + $GRANULARITY;
   }

   (print {$_[2]} $_[1]) ? length $_[1] : -1
}

1;

=head1 AUTHOR

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

=cut


Revision:	1.7
Committed:	Wed Oct 3 18:37:48 2007 UTC (16 years, 8 months ago) by root
Branch:	MAIN
CVS Tags:	rel-4_0, rel-4_01, rel-4_03, rel-4_02
Changes since 1.6:	+2 -2 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	1.6	This is being implemented by using a perlio layer that feeds only small
17			amounts of data (512 bytes per call) into Storable, and C<Coro::cede>'ing
18			regularly (at most 1000 times per second by default, though).
19
20	root	1.2	As it seems that Storable is not reentrant, this module also serialises
21	root	1.6	calls to freeze and thaw between coroutines as necessary (for this to work
22			reliably you always have to use this module, however).
23	root	1.2
24	root	1.1	=head1 FUNCTIONS
25
26			=over 4
27
28			=item $ref = thaw $pst
29
30			Retrieve an object from the given $pst, which must have been created with
31			C<Coro::Storable::freeze> or C<Storable::store_fd>/C<Storable::store>
32			(sorry, but Storable uses incompatible formats for disk/mem objects).
33
34	root	1.4	This works by calling C<Coro::cede> for every 4096 bytes read in.
35	root	1.1
36			=item $pst = freeze $ref
37
38			Freeze the given scalar into a Storable object. It uses the same format as
39	root	1.6	C<Storable::store_fd>.
40	root	1.1
41			This works by calling C<Coro::cede> for every write that Storable
42			issues. Unfortunately, Storable often makes many very small writes, so it
43			is rather inefficient. But it does keep the latency low.
44
45	root	1.6	=item $pst = nfreeze $ref
46
47	root	1.7	Same as C<freeze> but is compatible to C<Storable::nstore_fd> (note the
48	root	1.6	C<n>).
49
50			=item $pst = blocking_freeze $ref
51
52			Same as C<freeze> but is guaranteed to block. This is useful e.g. in
53			C<Coro::Util::fork_eval> when you want to serialise a data structure
54			for use with the C<thaw> function for this module. You cannot use
55	root	1.7	C<Storable::freeze> for this as Storable uses incompatible formats for
56	root	1.6	memory and file images.
57
58			=item $pst = blocking_nfreeze $ref
59
60			Same as C<blocking_freeze> but uses C<nfreeze> internally.
61
62	root	1.1	=back
63
64			=cut
65
66			package Coro::Storable;
67
68			use strict;
69
70			use Coro ();
71	root	1.2	use Coro::Semaphore ();
72	root	1.1
73			use Storable;
74			use base "Exporter";
75
76	root	1.6	our $VERSION = '0.2';
77			our @EXPORT = qw(thaw freeze nfreeze blocking_freeze blocking_nfreeze);
78	root	1.1
79	root	1.2	my $lock = new Coro::Semaphore;
80
81	root	1.6	sub thaw($) {
82			my $guard = $lock->guard;
83
84			open my $fh, "<:via(CoroCede)", \$_[0]
85			or die "cannot open pst via CoroCede: $!";
86			Storable::fd_retrieve $fh
87			}
88
89	root	1.1	sub freeze($) {
90	root	1.2	my $guard = $lock->guard;
91
92	root	1.1	open my $fh, ">:via(CoroCede)", \my $buf
93			or die "cannot open pst via CoroCede: $!";
94	root	1.6	Storable::store_fd $_[0], $fh;
95	root	1.1	$buf
96			}
97
98	root	1.6	sub nfreeze($) {
99	root	1.2	my $guard = $lock->guard;
100
101	root	1.6	open my $fh, ">:via(CoroCede)", \my $buf
102	root	1.1	or die "cannot open pst via CoroCede: $!";
103	root	1.6	Storable::nstore_fd $_[0], $fh;
104			$buf
105			}
106
107			sub blocking_freeze {
108			open my $fh, ">", \my $buf
109			or die "cannot open pst: $!";
110			Storable::store_fd $_[0], $fh;
111			close $fh;
112
113			$buf
114			}
115
116			sub blocking_nfreeze {
117			open my $fh, ">", \my $buf
118			or die "cannot open pst: $!";
119			Storable::nstore_fd $_[0], $fh;
120			close $fh;
121
122			$buf
123	root	1.1	}
124
125			package PerlIO::via::CoroCede;
126
127			# generic cede-on-read/write filtering layer
128
129	root	1.6	use Time::HiRes ("time");
130
131			our $GRANULARITY = 0.001;
132
133			my $next_cede;
134
135	root	1.1	sub PUSHED {
136			__PACKAGE__
137			}
138
139			sub FILL {
140	root	1.6	if ($next_cede <= time) {
141			$next_cede = time + $GRANULARITY; # calling time() twice usually is a net win
142			Coro::cede;
143			}
144
145	root	1.5	read $_[1], my $buf, 512
146	root	1.3	or return undef;
147	root	1.6
148	root	1.1	$buf
149			}
150
151			sub WRITE {
152	root	1.6	if ($next_cede <= (my $now = time)) {
153			Coro::cede;
154			$next_cede = $now + $GRANULARITY;
155			}
156
157	root	1.1	(print {$_[2]} $_[1]) ? length $_[1] : -1
158			}
159
160			1;
161
162			=head1 AUTHOR
163
164			Marc Lehmann <schmorp@schmorp.de>
165			http://home.schmorp.de/
166
167			=cut
168
169