Crc32.cs

namespace Waher.Content.Zip
{
    public static class Crc32
    {
        private static readonly uint[] table = CreateTable();
 
        private static uint[] CreateTable()
        {
            uint[] Result = new uint[256];
 
            for (uint i = 0; i < 256; i++)
            {
                uint c = i;
 
                for (int k = 0; k < 8; k++)
                    c = (c & 1) != 0 ? 0xedb88320u ^ (c >> 1) : c >> 1;
 
                Result[i] = c;
            }
 
            return Result;
        }
 
        public static uint Compute(byte[] Data)
        {
            uint Crc = 0xffffffff;
 
            foreach (byte b in Data)
                Crc = table[(byte)(Crc ^ b)] ^ (Crc >> 8);
 
            return ~Crc;
        }
 
        public static uint Update(uint Crc, byte Value)
        {
            return table[(byte)(Crc ^ Value)] ^ (Crc >> 8);
        }
 
    }
}