56 lines
1.1 KiB
C#
56 lines
1.1 KiB
C#
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// Common/CRC.cs
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namespace SevenZip
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{
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class CRC
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{
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public static readonly uint[] Table;
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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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uint _value = 0xFFFFFFFF;
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public void Init() { _value = 0xFFFFFFFF; }
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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() { return _value ^ 0xFFFFFFFF; }
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static uint CalculateDigest(byte[] data, uint offset, uint size)
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{
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CRC 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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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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}
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