using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace CksCalc
{
    //------------ crc32----------------------------------
    class CRC32
    {

        public UInt32 Calculate(byte[] Value, UInt32 ini)
        {
            UInt32[] CRCTable = new UInt32[256];
            for (int i = 0; i < 256; i++)
            {
                UInt32 entry = (UInt32)i;
                for (int j = 0; j < 8; j++)  //prepare to rotate 8bits
                    if ((entry & 1) == 1)
                        entry = (entry >> 1) ^ 0xEDB88320; //rotate and xor with polynomic 0xEDB88320
                    else
                        entry = entry >> 1; //rotate entry
                CRCTable[i] = entry;
            }

            UInt32 CRCVal = ini;
            for (int i = 0; i < Value.Length; i++)
            {
                CRCVal = (CRCVal >> 8) ^ CRCTable[(CRCVal & 0xff) ^ Value[i]];
                Console.WriteLine("CRCVal : " + i + " " + CRCTable[(CRCVal & 0xff) ^ Value[i]].ToString("X2") + " " + CRCVal  + " " + CRCVal.ToString("X2"));
            }
            CRCVal ^= 0xFFFFFFFF; // NOT
            UInt32 Result = CRCVal;

            Console.WriteLine("CRC32 Decimal: " + Result);
            Console.WriteLine("CRC32 Hex: " + Result.ToString("X2"));
            return Result;
        }


    }//------------ crc32- end---------------------------------
}