问创建我自己的校验和算法

EN

private static double GetChecksum2(string file)
    {
        double checkSum = 0;

        var stream = File.OpenRead(file);

        // the bigger the chunck size the faster but the more memory usage by cpu
        // also when sending file over network it should not be that much more efficient

        int chunckSize = (int) Math.Pow(2,20); // 10 => kilobite   20 => megabite  30 => gigabite etc..
        byte[] buffer = new byte[chunckSize];

        int bytesRead = 0;

        while ( // while bytesRead > 0
            (bytesRead =
                (stream.Read(buffer, 0, buffer.Length)) // returns the number of bytes read or 0 if no bytes read
            ) > 0)
        {
            //buffer is now an array of size bytesRead

            // write those bytes to a file, perform checksum of file
            // etc...


            // temp check sum use a better algorithm I dont know if other computers will round 
            // doubles diferently

            for (int i = 0; i < bytesRead; i++)
            {
                checkSum = (((buffer[i] + i)/2 + checkSum))*.45;
            }


            //SHA256Managed sha = new SHA256Managed();
            //byte[] checksum = sha.ComputeHash(buffer);

        }

        return checkSum;
    }