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#------------------------------------------------------------------- |
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# |
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# Sub::Contract::Cache - Implement a subroutine's cache |
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# |
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# $Id: Cache.pm,v 1.3 2009/06/16 12:23:58 erwan_lemonnier Exp $ |
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# |
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package Sub::Contract::Cache; |
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use strict; |
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702
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use warnings; |
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use Carp qw(croak confess); |
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use Data::Dumper; |
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use Symbol; |
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our $VERSION = '0.12'; |
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# NOTE: to speed up things, we do very little sanity control of method |
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# arguments, so that a key can for example be undefined though it |
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# should be an error. This class is to be used internally by |
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# Sub::Contract only. If you attempt to use it directly for other |
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# purpose, make sure you really need to do that, and if so, don't rely |
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# on Sub::Contract::Cache to validate them for you. |
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sub new { |
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my ($class,%args) = @_; |
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$class = ref $class || $class; |
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my $size = delete $args{size} or croak "BUG: missing max_size"; |
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my $namespace = delete $args{namespace} or croak "BUG: missing namespace"; |
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croak "BUG: new() got unknown arguments: ".Dumper(%args) if (%args); |
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croak "BUG: size should be a number" if (!defined $size || $size !~ /^\d+$/); |
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# NOTE: $contract->reset() deletes this cache |
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# TODO: do we want to keep previous content of cache? |
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my $self = bless({},$class); |
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$self->{cache} = {}; |
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$self->{cache_max_size} = $size; |
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$self->{cache_size} = 0; |
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$self->{namespace} = $namespace; |
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return $self; |
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} |
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sub clear { |
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my $self = shift; |
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# a fast way to delete all keys in a hash |
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delete @{$self->{cache}}{keys %{$self->{cache}}}; |
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$self->{cache_size} = 0; |
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} |
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sub has { |
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my ($self,$key) = @_; |
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return exists $self->{cache}->{$key}; |
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} |
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sub set { |
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my ($self,$key,$value) = @_; |
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croak "BUG: undefined cache key".Dumper($key,$value) |
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if (!defined $key); |
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if ($self->{cache_size} >= $self->{cache_max_size}) { |
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$self->clear; |
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} |
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$self->{cache}->{$key} = $value; |
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$self->{cache_size}++; |
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} |
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sub get { |
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my ($self,$key) = @_; |
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return $self->{cache}->{$key}; |
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} |
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1; |
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=pod |
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=head1 NAME |
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Sub::Contract::Cache - A data cache |
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=head1 SYNOPSIS |
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my $cache = new Sub::Contract::Cache(max_size => 10000, namespace => 'foo'); |
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if ($cache->has($key)) { |
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return $cache->get($key); |
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} else { |
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my $value = foo(@args); |
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$cache->set($key,$value); |
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return $value; |
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} |
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=head1 DESCRIPTION |
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A Sub::Contract::Cache is just a data cache used by contracts to |
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memoize subroutine's results. Sub::Contract has its own cache |
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implementation for efficiency reasons. |
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=head1 API |
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=over 4 |
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=item C<< my $cache = new(max_size => $max_size, namespace => $name) >> |
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Return an empty cache object that may contain up to C<$max_size> |
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elements and caches results from the subroutine C<$name>. |
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=item C<< $contract->clear([size => $max_size]) >> |
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Empty this cache of all its elements. |
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=item C<< $contract->set($key,$ref_result) >> |
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Add a cache entry for the key C<$key> with result C<$result>. |
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=item C<< $contract->has($key) >> |
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Return true if the cache contains a result for this key, false if not. |
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=item C<< $contract->get($key) >> |
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Return the cached result associated with key C<$key>. You must call |
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C first to ensure that there really is a cached result for this |
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key. C on an unknown key will return undef and not fail. |
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=back |
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=head1 SEE ALSO |
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See 'Sub::Contract'. |
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=head1 VERSION |
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$Id: Cache.pm,v 1.3 2009/06/16 12:23:58 erwan_lemonnier Exp $ |
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=head1 AUTHOR |
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Erwan Lemonnier C<< >> |
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=head1 LICENSE |
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See Sub::Contract. |
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=cut |
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