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Contents
module Cuboid
module Support::Cache
# Least Cost Replacement cache implementation.
#
# Maintains 3 cost classes (low, medium, high) ) and discards entries from the
# lowest cost classes in order to make room for new ones.
#
# @author Tasos "Zapotek" Laskos <tasos.laskos@gmail.com>
class LeastCostReplacement < Base
VALID_COSTS = [ :low, :medium, :high ]
# @see Cuboid::Cache::Base#initialize
def initialize( * )
super
reset_costs
end
# Storage method
#
# @param [Object] k
# Entry key.
# @param [Object] v
# Object to store.
# @param [Symbol] cost
#
# @return [Object] `v`
#
# @see VALID_COSTS
def store( k, v, cost = :low )
fail( "invalid cost: #{cost}" ) if !valid_cost?( cost )
super( k, v )
ensure
@costs[cost] << k
end
# @see Cuboid::Cache::Base#clear
def clear
super
ensure
reset_costs
end
private
def reset_costs
@costs = {}
VALID_COSTS.each { |c| @costs[c] = [] }
end
def valid_cost?( cost )
VALID_COSTS.include?( cost )
end
def candidate_from_cost_class( cost_class )
return if (costs = @costs[cost_class]).empty?
costs.delete_at( rand( costs.size ) )
end
def prune_candidate
VALID_COSTS.each do |cost|
if c = candidate_from_cost_class( cost )
return c
end
end
end
def prune
delete( prune_candidate )
end
end
end
end
Version data entries
32 entries across 32 versions & 1 rubygems