CRC Calculation(Groovy Language)

/************************************************************************************\
 * file name   : CRC.groovy                                                         *
 * description : this is a groovy-script file, used for crc-calculation             *
 * author      : [email protected]                                                     *
 * CAUTION     : the crc-remainder length must be multiple of 4: crc4/8/12/16, etc. *
\************************************************************************************/

class CRC
{
    static void main(args)
    {
        //application example
        //1. specify generator polynomial(hex format)
        def g_hex = "1021";
        
        //2. specify crc-ini data(hex format)
        def c_ini = "0000";
        
        //3. specify source data(hex format)
        def d_hex = "110210";
        
        //4. crc-calculate(hex format)
        def c_hex = "";
        //4-1 normal usage
        c_hex = CRC.crcCalc(g_hex, d_hex, c_ini);
        println(c_hex);
        
        //4-2 not-operation upon crc-result
        c_hex = CRC.hexBitNot(CRC.crcCalc(g_hex, d_hex, c_ini));
        println(c_hex);
        
        //4-3 byte-reverse upon source data
        c_hex = CRC.crcCalc(g_hex, CRC.hexByteRev(d_hex), c_ini);
        println(c_hex);
        
        //4-4 some other usages ...
    }

    //hex-str to bit-str
    def static String hexToBit(hex)
    { 
        def bit = '';
        for(c in hex)
            bit += String.format('%4s', Integer.toString(Integer.parseInt(c, 16), 2)).replace(' ', '0');
        return bit;
    }

    //bit-str to hex-str
    def static String bitToHex(bit)
    {   
        def hex = '';
        0.step(bit.length(), 4)
        {
            idx ->
            hex += Integer.toString(Integer.parseInt(bit[idx..idx+3], 2), 16).toUpperCase();
        }
        return hex;
    }

    //byte-reverse for hex-str
    def static String hexByteRev(hex)
    {
        assert hex.length()%2 == 0

        def hexRev = '';
        0.step(hex.length(), 2)
        {
            idx ->
            hexRev += bitToHex(hexToBit(hex[idx..idx+1]).reverse());
        }
        return hexRev;
    }

    //not-operation upon hex-str
    def static String hexBitNot(hex)
    {
        def hexNot = '';
        for(ch in hex)
            hexNot += Integer.toString((~Integer.parseInt(ch, 16)) & 0xF, 16).toUpperCase();
        return hexNot;
    }

    //crc-calculate
    def static String crcCalc(g_hex, d_hex, c_ini)
    {
        assert g_hex.length() == c_ini.length()

        def c_bitList = CRC.hexToBit(c_ini).toList();
        def g_bitList = CRC.hexToBit(g_hex).toList();

        for(ch in d_hex)
        {
            def d_bitList = CRC.hexToBit(ch).toList();
            for(bit in d_bitList)
            {
                def fed = c_bitList[0] as Integer ^
                          bit as Integer
                for(i in 0..g_bitList.size()-2) c_bitList[i] = c_bitList[i+1] as Integer ^
                                                               (g_bitList[i] as Integer & fed)
                c_bitList[g_bitList.size()-1] = fed
            }
        }

        def c_hex = CRC.bitToHex(c_bitList.join());
        return c_hex
    }
    
}