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;
        }
    }
    
    int                 _value = -1;
    
    public void Init()
    {
        _value = -1;
    }
    
    public void Update(byte[] data, int offset, int size)
    {
        for (int i = 0; i < size; i++)
        {
            _value = Table[(_value ^ data[offset + i]) & 0xFF] ^ _value >>> 8;
        }
    }
    
    public void Update(byte[] data)
    {
        final int size = data.length;
        for (int i = 0; i < size; i++)
        {
            _value = Table[(_value ^ data[i]) & 0xFF] ^ _value >>> 8;
        }
    }
    
    public void UpdateByte(int b)
    {
        _value = Table[(_value ^ b) & 0xFF] ^ _value >>> 8;
    }
    
    public int GetDigest()
    {
        return _value ^ -1;
    }
}