75 lines
2.3 KiB
C#
75 lines
2.3 KiB
C#
/* This file is part of SevenZipSharp.
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SevenZipSharp is free software: you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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SevenZipSharp is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with SevenZipSharp. If not, see <http://www.gnu.org/licenses/>.
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*/
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namespace SevenZip.Sdk
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{
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internal class CRC
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{
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public static readonly uint[] Table;
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private uint _value = 0xFFFFFFFF;
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static CRC()
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{
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Table = new uint[256];
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const uint kPoly = 0xEDB88320;
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for (uint i = 0; i < 256; i++)
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{
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uint r = i;
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for (int j = 0; j < 8; j++)
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if ((r & 1) != 0)
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r = (r >> 1) ^ kPoly;
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else
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r >>= 1;
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Table[i] = r;
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}
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}
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public void Init()
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{
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_value = 0xFFFFFFFF;
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}
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public void UpdateByte(byte b)
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{
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_value = Table[(((byte) (_value)) ^ b)] ^ (_value >> 8);
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}
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public void Update(byte[] data, uint offset, uint size)
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{
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for (uint i = 0; i < size; i++)
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_value = Table[(((byte) (_value)) ^ data[offset + i])] ^ (_value >> 8);
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}
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public uint GetDigest()
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{
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return _value ^ 0xFFFFFFFF;
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}
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private static uint CalculateDigest(byte[] data, uint offset, uint size)
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{
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var crc = new CRC();
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// crc.Init();
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crc.Update(data, offset, size);
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return crc.GetDigest();
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}
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private static bool VerifyDigest(uint digest, byte[] data, uint offset, uint size)
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{
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return (CalculateDigest(data, offset, size) == digest);
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}
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}
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} |