CRC.java

// SevenZip/CRC.java
package sevenzip;


public class CRC {

    static public int[] Table = new int[256];


    static {
        for (int i = 0; i<256; i++) {
            int r = i;
            for (int j = 0; j<8; j++) {
                if ((r&1)!=0) {
                    r = (r>>>1)^0xEDB88320;
                } else {
                    r >>>= 1;
                }
            }
            Table[i] = r;
        }
    }

    private int crcValue = -1;


    public void Init() {
        crcValue = -1;
    }


    public void Update(byte[] data, int offset, int size) {
        for (int i = 0; i<size; i++) {
            crcValue = Table[(crcValue^data[offset+i])&0xFF]^(crcValue>>>8);
        }
    }


    public void Update(byte[] data) {
        int size = data.length;
        for (int i = 0; i<size; i++) {
            crcValue = Table[(crcValue^data[i])&0xFF]^(crcValue>>>8);
        }
    }


    public void UpdateByte(int b) {
        crcValue = Table[(crcValue^b)&0xFF]^(crcValue>>>8);
    }


    public int GetDigest() {
        return crcValue^(-1);
    }

}