Current File : //usr/share/perl5/vendor_perl/Cache/SizeAwareCache.pm
######################################################################
# $Id: SizeAwareCache.pm,v 1.10 2002/04/07 17:04:46 dclinton Exp $
# Copyright (C) 2001-2003 DeWitt Clinton All Rights Reserved
#
# Software distributed under the License is distributed on an "AS
# IS" basis, WITHOUT WARRANTY OF ANY KIND, either expressed or
# implied. See the License for the specific language governing
# rights and limitations under the License.
######################################################################
package Cache::SizeAwareCache;
use strict;
use Cache::Cache;
use vars qw( @ISA @EXPORT_OK $EXPIRES_NOW $EXPIRES_NEVER $NO_MAX_SIZE );
use Exporter;
@ISA = qw( Cache::Cache Exporter );
@EXPORT_OK = qw( $EXPIRES_NOW $EXPIRES_NEVER $NO_MAX_SIZE );
$EXPIRES_NOW = $Cache::Cache::EXPIRES_NOW;
$EXPIRES_NEVER = $Cache::Cache::EXPIRES_NEVER;
$NO_MAX_SIZE = -1;
sub limit_size;
sub get_max_size;
sub set_max_size;
1;
__END__
=pod
=head1 NAME
Cache::SizeAwareCache -- extends the Cache interface.
=head1 DESCRIPTION
The SizeAwareCache interface is implemented by classes that support
all of the Cache::Cache interface in addition to the limit_size and
max_size features of a size aware cache.
The default cache size limiting algorithm works by removing cache
objects in the following order until the desired limit is reached:
1) objects that have expired
2) objects that are least recently accessed
3) objects that that expire next
=head1 SYNOPSIS
use Cache::SizeAwareCache;
use vars qw( @ISA );
@ISA = qw( Cache::SizeAwareCache );
=head1 CONSTANTS
Please see Cache::Cache for standard constants
=over
=item I<$NO_MAX_SIZE>
The cache has no size restrictions
=back
=head1 METHODS
Please see Cache::Cache for the standard methods
=over
=item B<limit_size( $new_size )>
Attempt to resize the cache such that the total disk usage is under
the I<$new_size> parameter. I<$new_size> represents t size (in bytes)
that the cache should be limited to. Note that this is only a one
time adjustment. To maintain the cache size, consider using the
I<max_size> option, although it is considered very expensive, and can
often be better achieved by peridocally calling I<limit_size>.
=back
=head1 OPTIONS
Please see Cache::Cache for the standard options
=over
=item I<max_size>
Sets the max_size property (size in bytes), which is described in
detail below. Defaults to I<$NO_MAX_SIZE>.
=back
=head1 PROPERTIES
Please see Cache::Cache for standard properties
=over
=item B<(get|set)_max_size>
If this property is set, then the cache will try not to exceed the max
size value (in bytes) specified. NOTE: This causes the size of the
cache to be checked on every set, and can be considered *very*
expensive in some implementations. A good alternative approach is
leave max_size as $NO_MAX_SIZE and to periodically limit the size of
the cache by calling the limit_size( $size ) method.
=back
=head1 SEE ALSO
Cache::Cache
=head1 AUTHOR
Original author: DeWitt Clinton <dewitt@unto.net>
Last author: $Author: dclinton $
Copyright (C) 2001-2003 DeWitt Clinton
=cut
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