# File lib/cgi/session.rb, line 371
      def initialize(session, option={})
        dir = option['tmpdir'] || Dir::tmpdir
        prefix = option['prefix'] || ''
        suffix = option['suffix'] || ''
        id = session.session_id
        require 'digest/md5'
        md5 = Digest::MD5.hexdigest(id)[0,16]
        @path = dir+"/"+prefix+md5+suffix
        if File::exist? @path
          @hash = nil
        else
          unless session.new_session
            raise CGI::Session::NoSession, "uninitialized session"
          end
          @hash = {}
        end
      end