A function that returns a 64-bit crc for string - Java Security

Java examples for Security:CRC

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Description

A function that returns a 64-bit crc for string

Demo Code


//package com.java2s;

public class Main {
    private static boolean init = false;
    private static long[] CRCTable = new long[256];
    private static final long POLY64REV = 0x95AC9329AC4BC9B5L;
    private static final long INITIALCRC = 0xFFFFFFFFFFFFFFFFL;

    /**/* ww w.  j a  va2s  . co  m*/
     * A function that returns a 64-bit crc for string
     * 
     * @param in input string
     * @return 64-bit crc value
     */
    public static final long crc64Long(String in) {
        if (in == null || in.length() == 0) {
            return 0;
        }
        // http://bioinf.cs.ucl.ac.uk/downloads/crc64/crc64.c
        long crc = INITIALCRC, part;
        if (!init) {
            for (int i = 0; i < 256; i++) {
                part = i;
                for (int j = 0; j < 8; j++) {
                    int value = ((int) part & 1);
                    if (value != 0) {
                        part = (part >> 1) ^ POLY64REV;
                    } else {
                        part >>= 1;
                    }
                }
                CRCTable[i] = part;
            }
            init = true;
        }
        int length = in.length();
        for (int k = 0; k < length; ++k) {
            char c = in.charAt(k);
            crc = CRCTable[(((int) crc) ^ c) & 0xff] ^ (crc >> 8);
        }
        return crc;
    }
}

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