CRC.java revision baa3858d3f5d128a5c8466b700098109edcad5f2 
1// SevenZip/CRC.java
2
3package SevenZip;
4
5public 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}
53