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- // Common/CRC.cs
- namespace SevenZip
- {
- class CRC
- {
- public static readonly uint[] Table;
- static CRC()
- {
- Table = new uint[256];
- const uint kPoly = 0xEDB88320;
- for (uint i = 0; i < 256; i++)
- {
- uint r = i;
- for (int j = 0; j < 8; j++)
- if ((r & 1) != 0)
- r = (r >> 1) ^ kPoly;
- else
- r >>= 1;
- Table[i] = r;
- }
- }
- uint _value = 0xFFFFFFFF;
- public void Init() { _value = 0xFFFFFFFF; }
- public void UpdateByte(byte b)
- {
- _value = Table[(((byte)(_value)) ^ b)] ^ (_value >> 8);
- }
- public void Update(byte[] data, uint offset, uint size)
- {
- for (uint i = 0; i < size; i++)
- _value = Table[(((byte)(_value)) ^ data[offset + i])] ^ (_value >> 8);
- }
- public uint GetDigest() { return _value ^ 0xFFFFFFFF; }
- static uint CalculateDigest(byte[] data, uint offset, uint size)
- {
- CRC crc = new CRC();
- // crc.Init();
- crc.Update(data, offset, size);
- return crc.GetDigest();
- }
- static bool VerifyDigest(uint digest, byte[] data, uint offset, uint size)
- {
- return (CalculateDigest(data, offset, size) == digest);
- }
- }
- }
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