# File lib/action_mailer/vendor/tmail-1.2.7/tmail/vendor/rchardet-1.3/lib/rchardet/charsetprober.rb, line 55
    def filter_high_bit_only(aBuf)
      # DO NOT USE `gsub!`
      # It will remove all characters from the buffer that is later used by
      # other probers.  This is because gsub! removes data from the instance variable
      # that will be passed to later probers, while gsub makes a new instance variable
      # that will not. 
      newBuf = aBuf.gsub(/([\x00-\x7F])+/, ' ')
      return newBuf
    end