class ActiveSupport::Cache::FileStore

def normalize_key(key, options)
  key = super
  fname = URI.encode_www_form_component(key)
  if fname.size > FILEPATH_MAX_SIZE
    fname = ActiveSupport::Digest.hexdigest(key)
  end
  hash = Zlib.adler32(fname)
  hash, dir_1 = hash.divmod(0x1000)
  dir_2 = hash.modulo(0x1000)
  # Make sure file name doesn't exceed file system limits.
  if fname.length < FILENAME_MAX_SIZE
    fname_paths = fname
  else
    fname_paths = []
    begin
      fname_paths << fname[0, FILENAME_MAX_SIZE]
      fname = fname[FILENAME_MAX_SIZE..-1]
    end until fname.blank?
  end
  File.join(cache_path, DIR_FORMATTER % dir_1, DIR_FORMATTER % dir_2, fname_paths)
end