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