misc/libphysfs/lzma/CS/7zip/Common/CRC.cs
author nemo
Mon, 10 Apr 2017 12:06:43 -0400
changeset 12218 bb5522e88ab2
permissions -rw-r--r--
bulk copy of latest physfs to our misc/libphysfs since this seems to fix an off-by-1 error reliably hit in readln read of 1 byte probably introduced in the addition of the buffered read. Whether this is excessive or whether libphysfs should even be maintained by us is another matter. But at least we shouldn't crash

// 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);
		}
	}
}