activesupport/lib/active_support/weak_hash.rb


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module ActiveSupport
  class WeakHash
    def initialize(cache = Hash.new)
      @cache = cache
      @key_map = {}
      @rev_cache = Hash.new{|h,k| h[k] = {}}
      @reclaim_value = lambda do |value_id|
        if value = @rev_cache.delete(value_id)
          value.each_key{|key| @cache.delete key}
        end
      end
    end

    def [](key)
      value_id = @cache[key]
      value_id && ObjectSpace._id2ref(value_id)
    rescue RangeError
      nil
    end

    def []=(key, value)
      key2 = case key
             when Fixnum, Symbol, true, false, nil
               key
             else
               key.dup
             end

      @rev_cache[value.object_id][key2] = true
      @cache[key2] = value.object_id
      @key_map[key.object_id] = key2

      ObjectSpace.define_finalizer(value, @reclaim_value)
    end

    def clear
      @cache.clear
    end

    def delete(key)
      @cache.delete(key)
    end
  end
end

ActiveSupport::WeakHash = ::Weakling::WeakHash if defined?(RUBY_ENGINE) && RUBY_ENGINE == 'jruby'