BizHawk/BizHawk.Emulation/Database/CRC32.cs

namespace BizHawk
{
 	public static class CRC32 
    {
		// Lookup table for speed.
		private static uint[] CRC32Table;

		static CRC32() 
        {
			CRC32Table = new uint[256];
		    for (uint i = 0; i < 256; ++i) 
            {
				uint crc = i;
				for (int j = 8; j > 0; --j) 
                {
					if ((crc & 1) == 1)
						crc = ((crc >> 1) ^ 0xEDB88320);
				    else
						crc >>= 1;
				}
				CRC32Table[i] = crc;
			}
		}

        public static int Calculate(byte[] data) 
        {
		    uint Result = 0xFFFFFFFF;
			foreach (var b in data) 
                Result = (((Result) >> 8) ^ CRC32Table[b ^ ((Result) & 0xFF)]);				
			return (int)~Result;
		}
	}
}