Android Open Source - base_controller Husky Base Utils

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Java Source Code

package com.github.c77.base_driver.husky;
//from  w  ww  .j  a  va  2s . c o m
import org.apache.commons.codec.binary.Hex;

import java.util.Arrays;

 * @author (Julian Cerruti)
public class HuskyBaseUtils {

     * Calculates the checksum of a given command package.
     * It assumes the provided buffer has space for the checksum at the end (2 bytes) so those
     * two bytes are not included in the checksum calculation
     * See Appendix A of "clearpath control protocol" doc,to understand how to implement it
     * - Polynomial: x16+x12+x5+1 (0x1021)
     * - Initial value: 0xFFFF
     * - Check constant: 0x1D0F
    public static char checkSum(byte[] cmdPackage) {
        //CRC lookup table for polynomial 0x1021
        char table[] = {
                0x0, 0x1021, 0x2042, 0x3063, 0x4084, 0x50a5, 0x60c6, 0x70e7,
                0x8108, 0x9129, 0xa14a, 0xb16b, 0xc18c, 0xd1ad, 0xe1ce, 0xf1ef,
                0x1231, 0x210, 0x3273, 0x2252, 0x52b5, 0x4294, 0x72f7, 0x62d6,
                0x9339, 0x8318, 0xb37b, 0xa35a, 0xd3bd, 0xc39c, 0xf3ff, 0xe3de,
                0x2462, 0x3443, 0x420, 0x1401, 0x64e6, 0x74c7, 0x44a4, 0x5485,
                0xa56a, 0xb54b, 0x8528, 0x9509, 0xe5ee, 0xf5cf, 0xc5ac, 0xd58d,
                0x3653, 0x2672, 0x1611, 0x630, 0x76d7, 0x66f6, 0x5695, 0x46b4,
                0xb75b, 0xa77a, 0x9719, 0x8738, 0xf7df, 0xe7fe, 0xd79d, 0xc7bc,
                0x48c4, 0x58e5, 0x6886, 0x78a7, 0x840, 0x1861, 0x2802, 0x3823,
                0xc9cc, 0xd9ed, 0xe98e, 0xf9af, 0x8948, 0x9969, 0xa90a, 0xb92b,
                0x5af5, 0x4ad4, 0x7ab7, 0x6a96, 0x1a71, 0xa50, 0x3a33, 0x2a12,
                0xdbfd, 0xcbdc, 0xfbbf, 0xeb9e, 0x9b79, 0x8b58, 0xbb3b, 0xab1a,
                0x6ca6, 0x7c87, 0x4ce4, 0x5cc5, 0x2c22, 0x3c03, 0xc60, 0x1c41,
                0xedae, 0xfd8f, 0xcdec, 0xddcd, 0xad2a, 0xbd0b, 0x8d68, 0x9d49,
                0x7e97, 0x6eb6, 0x5ed5, 0x4ef4, 0x3e13, 0x2e32, 0x1e51, 0xe70,
                0xff9f, 0xefbe, 0xdfdd, 0xcffc, 0xbf1b, 0xaf3a, 0x9f59, 0x8f78,
                0x9188, 0x81a9, 0xb1ca, 0xa1eb, 0xd10c, 0xc12d, 0xf14e, 0xe16f,
                0x1080, 0xa1, 0x30c2, 0x20e3, 0x5004, 0x4025, 0x7046, 0x6067,
                0x83b9, 0x9398, 0xa3fb, 0xb3da, 0xc33d, 0xd31c, 0xe37f, 0xf35e,
                0x2b1, 0x1290, 0x22f3, 0x32d2, 0x4235, 0x5214, 0x6277, 0x7256,
                0xb5ea, 0xa5cb, 0x95a8, 0x8589, 0xf56e, 0xe54f, 0xd52c, 0xc50d,
                0x34e2, 0x24c3, 0x14a0, 0x481, 0x7466, 0x6447, 0x5424, 0x4405,
                0xa7db, 0xb7fa, 0x8799, 0x97b8, 0xe75f, 0xf77e, 0xc71d, 0xd73c,
                0x26d3, 0x36f2, 0x691, 0x16b0, 0x6657, 0x7676, 0x4615, 0x5634,
                0xd94c, 0xc96d, 0xf90e, 0xe92f, 0x99c8, 0x89e9, 0xb98a, 0xa9ab,
                0x5844, 0x4865, 0x7806, 0x6827, 0x18c0, 0x8e1, 0x3882, 0x28a3,
                0xcb7d, 0xdb5c, 0xeb3f, 0xfb1e, 0x8bf9, 0x9bd8, 0xabbb, 0xbb9a,
                0x4a75, 0x5a54, 0x6a37, 0x7a16, 0xaf1, 0x1ad0, 0x2ab3, 0x3a92,
                0xfd2e, 0xed0f, 0xdd6c, 0xcd4d, 0xbdaa, 0xad8b, 0x9de8, 0x8dc9,
                0x7c26, 0x6c07, 0x5c64, 0x4c45, 0x3ca2, 0x2c83, 0x1ce0, 0xcc1,
                0xef1f, 0xff3e, 0xcf5d, 0xdf7c, 0xaf9b, 0xbfba, 0x8fd9, 0x9ff8,
                0x6e17, 0x7e36, 0x4e55, 0x5e74, 0x2e93, 0x3eb2, 0xed1, 0x1ef0

        int size = cmdPackage.length - 2;
        char checksum = 0xFFFF;
        int counter = 0;
        while(counter < size) {
            checksum = (char) ((char)(checksum << 8) ^ table[((checksum >> 8)^cmdPackage[counter]) & 0xFF]);
        return checksum;

     * Allows running statically for very basic stand-alone testing
    public static void main(String args[]) throws Exception {
        System.out.println("--> " + HuskyBaseUtils.byteArrayToString(new byte[] {
                0x14, 0x24, 0x4A, 0x77

        // Test a couple of known checksum values
    public static void testChecksum(String inputString, String expectedSum) throws Exception {
        byte[] sample = Hex.decodeHex(inputString.toCharArray());
        byte[] sampleCheckSum = Hex.decodeHex(expectedSum.toCharArray());
        char checksum = checkSum(sample);
        byte[] result = {
                (byte)(checksum & 0xFF),
                (byte)((checksum >> 8) & 0xFF)
        System.out.println("Calculated checksum: " + byteArrayToString(result) + " vs expected: " + expectedSum);

        // Confirmation
        char checksumComp = (char)(checksum ^ 0xFFFF);
        byte verifySample[] = Arrays.copyOf(sample, sample.length + 2);
        verifySample[verifySample.length - 4] = (byte)(checksumComp & 0xFF);
        verifySample[verifySample.length - 3] = (byte)(checksumComp >> 8);
        char verifier = checkSum(verifySample);
        byte[] verifierResult = {
                (byte)(verifier & 0xFF),
                (byte)((verifier >> 8) & 0xFF)
        System.out.println("Verifier = " + byteArrayToString(verifierResult));

    // Memory-helper function, only used for debugging
    public static String byteArrayToString(byte[] data) {
        return new String(Hex.encodeHex(data));

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