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 Deliantra
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 (1024 bytes per call) into Storable, and C<Coro::cede>'ing
regularly (at most 50 times per second by default, though).

As it seems that Storable is not reentrant, this module also wraps most
functions of the Storable module so that only one freeze or thaw is done
at any one moment (recursive invocations are not currently supported).

=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.

=item $guard = guard

Acquire the Storable lock, for when you want to call Storable yourself.

Note that this module already wraps the Storable functions, so there is
rarely the need to do this yourself.

=back

=cut

package Coro::Storable;

use strict qw(subs vars);
no warnings;

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

BEGIN {
   # suppress warnings
   local $^W = 0;
   require Storable;
}

use Storable;
use base "Exporter";

our $VERSION = 4.748;
our @EXPORT = qw(thaw freeze nfreeze blocking_thaw blocking_freeze blocking_nfreeze);

our $GRANULARITY = 0.02;

my $lock = new Coro::Semaphore;

sub guard {
   $lock->guard
}

# wrap xs functions
for (qw(net_pstore pstore net_mstore mstore pretrieve mretrieve dclone)) {
   my $orig = \&{"Storable::$_"};
   *{"Storable::$_"} = sub {
      my $guard = $lock->guard;
      &$orig
   };
   die if $@;
}

sub thaw($) {
   open my $fh, "<:cede($GRANULARITY)", \$_[0]
      or die "cannot open pst via PerlIO::cede: $!";
   Storable::fd_retrieve $fh
}

sub freeze($) {
   open my $fh, ">:cede($GRANULARITY)", \my $buf
      or die "cannot open pst via PerlIO::cede: $!";
   Storable::store_fd $_[0], $fh;
   $buf
}

sub nfreeze($) {
   open my $fh, ">:cede($GRANULARITY)", \my $buf
      or die "cannot open pst via PerlIO::cede: $!";
   Storable::nstore_fd $_[0], $fh;
   $buf
}

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

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
}

1;

=head1 AUTHOR

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

=cut


Revision:	1.28
Committed:	Wed Sep 24 21:20:05 2008 UTC (15 years, 9 months ago) by root
Branch:	MAIN
Changes since 1.27:	+8 -51 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	root	1.22	so that it cede's more often. Some applications (such as the Deliantra
13	root	1.1	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	root	1.27	amounts of data (1024 bytes per call) into Storable, and C<Coro::cede>'ing
18			regularly (at most 50 times per second by default, though).
19	root	1.6
20	root	1.22	As it seems that Storable is not reentrant, this module also wraps most
21			functions of the Storable module so that only one freeze or thaw is done
22			at any one moment (recursive invocations are not currently supported).
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	1.22	=item $guard = guard
63	root	1.8
64			Acquire the Storable lock, for when you want to call Storable yourself.
65
66	root	1.22	Note that this module already wraps the Storable functions, so there is
67			rarely the need to do this yourself.
68
69	root	1.1	=back
70
71			=cut
72
73			package Coro::Storable;
74
75	root	1.22	use strict qw(subs vars);
76	root	1.13	no warnings;
77	root	1.1
78			use Coro ();
79	root	1.2	use Coro::Semaphore ();
80	root	1.1
81	root	1.13	BEGIN {
82			# suppress warnings
83			local $^W = 0;
84			require Storable;
85			}
86
87	root	1.1	use Storable;
88			use base "Exporter";
89
90	root	1.26	our $VERSION = 4.748;
91	root	1.9	our @EXPORT = qw(thaw freeze nfreeze blocking_thaw blocking_freeze blocking_nfreeze);
92	root	1.1
93	root	1.28	our $GRANULARITY = 0.02;
94
95	root	1.2	my $lock = new Coro::Semaphore;
96
97	root	1.8	sub guard {
98			$lock->guard
99			}
100
101	root	1.22	# wrap xs functions
102	root	1.26	for (qw(net_pstore pstore net_mstore mstore pretrieve mretrieve dclone)) {
103	root	1.22	my $orig = \&{"Storable::$_"};
104			*{"Storable::$_"} = sub {
105			my $guard = $lock->guard;
106			&$orig
107			};
108			die if $@;
109			}
110
111	root	1.6	sub thaw($) {
112	root	1.28	open my $fh, "<:cede($GRANULARITY)", \$_[0]
113			or die "cannot open pst via PerlIO::cede: $!";
114	root	1.6	Storable::fd_retrieve $fh
115			}
116
117	root	1.1	sub freeze($) {
118	root	1.28	open my $fh, ">:cede($GRANULARITY)", \my $buf
119			or die "cannot open pst via PerlIO::cede: $!";
120	root	1.6	Storable::store_fd $_[0], $fh;
121	root	1.1	$buf
122			}
123
124	root	1.6	sub nfreeze($) {
125	root	1.28	open my $fh, ">:cede($GRANULARITY)", \my $buf
126			or die "cannot open pst via PerlIO::cede: $!";
127	root	1.6	Storable::nstore_fd $_[0], $fh;
128			$buf
129			}
130
131	root	1.10	sub blocking_thaw($) {
132	root	1.9	open my $fh, "<", \$_[0]
133			or die "cannot open pst: $!";
134			Storable::fd_retrieve $fh
135			}
136
137	root	1.10	sub blocking_freeze($) {
138	root	1.6	open my $fh, ">", \my $buf
139			or die "cannot open pst: $!";
140			Storable::store_fd $_[0], $fh;
141			close $fh;
142
143			$buf
144			}
145
146	root	1.10	sub blocking_nfreeze($) {
147	root	1.6	open my $fh, ">", \my $buf
148			or die "cannot open pst: $!";
149			Storable::nstore_fd $_[0], $fh;
150			close $fh;
151
152			$buf
153	root	1.1	}
154
155			1;
156
157			=head1 AUTHOR
158
159			Marc Lehmann <schmorp@schmorp.de>
160			http://home.schmorp.de/
161
162			=cut
163
164