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/* This file is part of SevenZipSharp.
SevenZipSharp is free software: you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
SevenZipSharp is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with SevenZipSharp. If not, see <http://www.gnu.org/licenses/>.
*/
namespace SevenZip.Sdk
{
internal class CRC
{
public static readonly uint[] Table;
private uint _value = 0xFFFFFFFF;
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;
}
}
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;
}
private static uint CalculateDigest(byte[] data, uint offset, uint size)
{
var crc = new CRC();
// crc.Init();
crc.Update(data, offset, size);
return crc.GetDigest();
}
private static bool VerifyDigest(uint digest, byte[] data, uint offset, uint size)
{
return (CalculateDigest(data, offset, size) == digest);
}
}
}
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