1 // SevenZip/CRC.java

     2 

     3 package SevenZip;

     4 

     5 public class CRC

     6 {

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

     8 	

     9 	static

    10 	{

    11 		for (int i = 0; i < 256; i++)

    12 		{

    13 			int r = i;

    14 			for (int j = 0; j < 8; j++)

    15 				if ((r & 1) != 0)

    16 					r = (r >>> 1) ^ 0xEDB88320;

    17 				else

    18 					r >>>= 1;

    19 			Table[i] = r;

    20 		}

    21 	}

    22 	

    23 	int _value = -1;

    24 	

    25 	public void Init()

    26 	{

    27 		_value = -1;

    28 	}

    29 	

    30 	public void Update(byte[] data, int offset, int size)

    31 	{

    32 		for (int i = 0; i < size; i++)

    33 			_value = Table[(_value ^ data[offset + i]) & 0xFF] ^ (_value >>> 8);

    34 	}

    35 	

    36 	public void Update(byte[] data)

    37 	{

    38 		int size = data.length;

    39 		for (int i = 0; i < size; i++)

    40 			_value = Table[(_value ^ data[i]) & 0xFF] ^ (_value >>> 8);

    41 	}

    42 	

    43 	public void UpdateByte(int b)

    44 	{

    45 		_value = Table[(_value ^ b) & 0xFF] ^ (_value >>> 8);

    46 	}

    47 	

    48 	public int GetDigest()

    49 	{

    50 		return _value ^ (-1);

    51 	}

    52 }