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# encoding: utf-8
module Memoizable
# Storage for memoized methods
class Memory
# Initialize the memory storage for memoized methods
#
# @param [ThreadSafe::Cache] memory
#
# @return [undefined]
#
# @api private
def initialize
@memory = ThreadSafe::Cache.new
@monitor = Monitor.new
freeze
end
# Get the value from memory
#
# @param [Symbol] name
#
# @return [Object]
#
# @api public
def [](name)
@memory.fetch(name) do
fail NameError, "No method #{name} is memoized"
end
end
# Store the value in memory
#
# @param [Symbol] name
# @param [Object] value
#
# @return [undefined]
#
# @api public
def []=(name, value)
memoized = true
@memory.compute_if_absent(name) do
memoized = false
value
end
fail ArgumentError, "The method #{name} is already memoized" if memoized
end
# Fetch the value from memory, or store it if it does not exist
#
# @param [Symbol] name
#
# @yieldreturn [Object]
# the value to memoize
#
# @api public
def fetch(name)
@memory.fetch(name) do # check for the key
@monitor.synchronize do # acquire a lock if the key is not found
@memory.fetch(name) do # recheck under lock
self[name] = yield # set the value
end
end
end
end
# Test if the name has a value in memory
#
# @param [Symbol] name
#
# @return [Boolean]
#
# @api public
def key?(name)
@memory.key?(name)
end
# A hook that allows Marshal to dump the object
#
# @return [Hash]
# A hash used to populate the internal memory
#
# @api public
def marshal_dump
@memory.marshal_dump
end
# A hook that allows Marshal to load the object
#
# @param [Hash] hash
# A hash used to populate the internal memory
#
# @return [undefined]
#
# @api public
def marshal_load(hash)
initialize
@memory.marshal_load(hash)
end
end # Memory
end # Memoizable
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