instance method get_confidence

# File actionmailer/lib/action_mailer/vendor/tmail-1.2.7/tmail/vendor/rchardet-1.3/lib/rchardet/chardistribution.rb, line 69
    def get_confidence
      # """return confidence based on existing data"""
      # if we didn't receive any character in our consideration range, return negative answer
      if @_mTotalChars <= 0
        return SURE_NO
      end

      if @_mTotalChars != @_mFreqChars
        r = @_mFreqChars / ((@_mTotalChars - @_mFreqChars) * @_mTypicalDistributionRatio)
        if r < SURE_YES
          return r
        end
      end

      # normalize confidence (we don't want to be 100% sure)
      return SURE_YES
    end