C byte array and class mutual conversion

When doing serial communication , Encountered a very interesting way of writing
The serial port information here is not a string , But a class represented by a byte array
Note that this is not json character string , It's an array of bytes
The idea is to open up a piece of memory in memory , Insert byte array into memory , Then encapsulate this memory as an object of the corresponding class
The code is as follows
Need to quote

using System.Runtime.InteropServices;

        /// <summary>
        ///  Byte to byte RtuAck Structure 
        /// </summary>
        /// <param name="arr"></param>
        public RtuAck Bytes2Ack(byte[] arr)
        {
    
            RtuAck ack = new RtuAck();

            int size = Marshal.SizeOf(ack);
            IntPtr ptr = Marshal.AllocHGlobal(size); // Declare an unmanaged memory , To hold arr

            Marshal.Copy(arr, 0, ptr, size);// take arr Stored in the declared memory 

            ack = (RtuAck)Marshal.PtrToStructure(ptr, ack.GetType());//  Turn this memory into ack type 
            Marshal.FreeHGlobal(ptr);// Release the unmanaged memory just declared 

            return ack;
        }

conversely , The code for transferring from class object to byte array is as follows

        public byte[] Ack2Bytes(RtuAck ack)
        {
    
            int size = Marshal.SizeOf(ack);
            byte[] arr = new byte[size];
            IntPtr ptr = Marshal.AllocHGlobal(size);
            Marshal.StructureToPtr(ack, ptr, true);
            Marshal.Copy(ptr, arr, 0, size);
            Marshal.FreeHGlobal(ptr);
            return arr;
        }