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.

=item $guard = guard;

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

=back

=cut

package Coro::Storable;

use strict;
no warnings;

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

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

use Storable;
use base "Exporter";

our $VERSION = 4.741;
our @EXPORT = qw(thaw freeze nfreeze blocking_thaw blocking_freeze blocking_nfreeze);

my $lock = new Coro::Semaphore;

sub guard {
   $lock->guard
}

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_thaw($) {
   my $guard = $lock->guard;

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

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

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

   $buf
}

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

   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:	1.16
Committed:	Fri May 30 21:34:52 2008 UTC (16 years, 1 month ago) by root
Branch:	MAIN
CVS Tags:	rel-4_741
Changes since 1.15:	+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	1.8	=item $guard = guard;
63
64			Acquire the Storable lock, for when you want to call Storable yourself.
65
66	root	1.1	=back
67
68			=cut
69
70			package Coro::Storable;
71
72			use strict;
73	root	1.13	no warnings;
74	root	1.1
75			use Coro ();
76	root	1.2	use Coro::Semaphore ();
77	root	1.1
78	root	1.13	BEGIN {
79			# suppress warnings
80			local $^W = 0;
81			require Storable;
82			}
83
84	root	1.1	use Storable;
85			use base "Exporter";
86
87	root	1.16	our $VERSION = 4.741;
88	root	1.9	our @EXPORT = qw(thaw freeze nfreeze blocking_thaw blocking_freeze blocking_nfreeze);
89	root	1.1
90	root	1.2	my $lock = new Coro::Semaphore;
91
92	root	1.8	sub guard {
93			$lock->guard
94			}
95
96	root	1.6	sub thaw($) {
97			my $guard = $lock->guard;
98
99			open my $fh, "<:via(CoroCede)", \$_[0]
100			or die "cannot open pst via CoroCede: $!";
101			Storable::fd_retrieve $fh
102			}
103
104	root	1.1	sub freeze($) {
105	root	1.2	my $guard = $lock->guard;
106
107	root	1.1	open my $fh, ">:via(CoroCede)", \my $buf
108			or die "cannot open pst via CoroCede: $!";
109	root	1.6	Storable::store_fd $_[0], $fh;
110	root	1.1	$buf
111			}
112
113	root	1.6	sub nfreeze($) {
114	root	1.2	my $guard = $lock->guard;
115
116	root	1.6	open my $fh, ">:via(CoroCede)", \my $buf
117	root	1.1	or die "cannot open pst via CoroCede: $!";
118	root	1.6	Storable::nstore_fd $_[0], $fh;
119			$buf
120			}
121
122	root	1.10	sub blocking_thaw($) {
123	root	1.9	my $guard = $lock->guard;
124
125			open my $fh, "<", \$_[0]
126			or die "cannot open pst: $!";
127			Storable::fd_retrieve $fh
128			}
129
130	root	1.10	sub blocking_freeze($) {
131	root	1.8	my $guard = $lock->guard;
132
133	root	1.6	open my $fh, ">", \my $buf
134			or die "cannot open pst: $!";
135			Storable::store_fd $_[0], $fh;
136			close $fh;
137
138			$buf
139			}
140
141	root	1.10	sub blocking_nfreeze($) {
142	root	1.8	my $guard = $lock->guard;
143
144	root	1.6	open my $fh, ">", \my $buf
145			or die "cannot open pst: $!";
146			Storable::nstore_fd $_[0], $fh;
147			close $fh;
148
149			$buf
150	root	1.1	}
151
152			package PerlIO::via::CoroCede;
153
154			# generic cede-on-read/write filtering layer
155
156	root	1.6	use Time::HiRes ("time");
157
158			our $GRANULARITY = 0.001;
159
160			my $next_cede;
161
162	root	1.1	sub PUSHED {
163			__PACKAGE__
164			}
165
166			sub FILL {
167	root	1.6	if ($next_cede <= time) {
168			$next_cede = time + $GRANULARITY; # calling time() twice usually is a net win
169	root	1.16	Coro::cede ();
170	root	1.6	}
171
172	root	1.5	read $_[1], my $buf, 512
173	root	1.3	or return undef;
174	root	1.6
175	root	1.1	$buf
176			}
177
178			sub WRITE {
179	root	1.6	if ($next_cede <= (my $now = time)) {
180			Coro::cede;
181			$next_cede = $now + $GRANULARITY;
182			}
183
184	root	1.1	(print {$_[2]} $_[1]) ? length $_[1] : -1
185			}
186
187			1;
188
189			=head1 AUTHOR
190
191			Marc Lehmann <schmorp@schmorp.de>
192			http://home.schmorp.de/
193
194			=cut
195
196