# File lib/CharDistributionAnalysis.rb, line 179
        def get_order(aStr)
            # for big5 encoding, we are interested 
            #   first  byte range: 0xa4 -- 0xfe
            #   second byte range: 0x40 -- 0x7e , 0xa1 -- 0xfe
            # no validation needed here. State machine has done that
            if aStr[0] >= 0xA4
                if aStr[1] >= 0xA1
                    return 157 * (aStr[0] - 0xA4) + aStr[1] - 0xA1 + 63
                else
                    return 157 * (aStr[0] - 0xA4) + aStr[1] - 0x40
                end
            else
                return -1
            end
        end