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 = 4.745;
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:	1.20
Committed:	Sun Aug 31 08:00:16 2008 UTC (15 years, 9 months ago) by root
Branch:	MAIN
Changes since 1.19:	+1 -1 lines
Log Message:	* empty log message *
#	Content
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	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	As it seems that Storable is not reentrant, this module also serialises
21	calls to freeze and thaw between coroutines as necessary (for this to work
22	reliably you always have to use this module, however).
23
24	=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	This works by calling C<Coro::cede> for every 4096 bytes read in.
35
36	=item $pst = freeze $ref
37
38	Freeze the given scalar into a Storable object. It uses the same format as
39	C<Storable::store_fd>.
40
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	=item $pst = nfreeze $ref
46
47	Same as C<freeze> but is compatible to C<Storable::nstore_fd> (note the
48	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	C<Storable::freeze> for this as Storable uses incompatible formats for
56	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	=item $guard = guard;
63
64	Acquire the Storable lock, for when you want to call Storable yourself.
65
66	=back
67
68	=cut
69
70	package Coro::Storable;
71
72	use strict;
73	no warnings;
74
75	use Coro ();
76	use Coro::Semaphore ();
77
78	BEGIN {
79	# suppress warnings
80	local $^W = 0;
81	require Storable;
82	}
83
84	use Storable;
85	use base "Exporter";
86
87	our $VERSION = 4.745;
88	our @EXPORT = qw(thaw freeze nfreeze blocking_thaw blocking_freeze blocking_nfreeze);
89
90	my $lock = new Coro::Semaphore;
91
92	sub guard {
93	$lock->guard
94	}
95
96	sub thaw($) {
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 $fh
102	}
103
104	sub freeze($) {
105	my $guard = $lock->guard;
106
107	open my $fh, ">:via(CoroCede)", \my $buf
108	or die "cannot open pst via CoroCede: $!";
109	Storable::store_fd $_[0], $fh;
110	$buf
111	}
112
113	sub nfreeze($) {
114	my $guard = $lock->guard;
115
116	open my $fh, ">:via(CoroCede)", \my $buf
117	or die "cannot open pst via CoroCede: $!";
118	Storable::nstore_fd $_[0], $fh;
119	$buf
120	}
121
122	sub blocking_thaw($) {
123	my $guard = $lock->guard;
124
125	open my $fh, "<", \$_[0]
126	or die "cannot open pst: $!";
127	Storable::fd_retrieve $fh
128	}
129
130	sub blocking_freeze($) {
131	my $guard = $lock->guard;
132
133	open my $fh, ">", \my $buf
134	or die "cannot open pst: $!";
135	Storable::store_fd $_[0], $fh;
136	close $fh;
137
138	$buf
139	}
140
141	sub blocking_nfreeze($) {
142	my $guard = $lock->guard;
143
144	open my $fh, ">", \my $buf
145	or die "cannot open pst: $!";
146	Storable::nstore_fd $_[0], $fh;
147	close $fh;
148
149	$buf
150	}
151
152	package PerlIO::via::CoroCede;
153
154	# generic cede-on-read/write filtering layer
155
156	use Time::HiRes ("time");
157
158	our $GRANULARITY = 0.001;
159
160	my $next_cede;
161
162	sub PUSHED {
163	__PACKAGE__
164	}
165
166	sub FILL {
167	if ($next_cede <= time) {
168	$next_cede = time + $GRANULARITY; # calling time() twice usually is a net win
169	Coro::cede ();
170	}
171
172	read $_[1], my $buf, 512
173	or return undef;
174
175	$buf
176	}
177
178	sub WRITE {
179	if ($next_cede <= (my $now = time)) {
180	Coro::cede ();
181	$next_cede = $now + $GRANULARITY;
182	}
183
184	(print {$_[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