using System; 

using System.Collections.Generic;

using System.Runtime.InteropServices;   

​

public class Program

{

    public static void Main()

    {

        int offset = 0;

        short value = 394;

        int value2 = 230547;

        Memory<byte> val2 = new byte[7];

        MemoryExtensions2.WriteToBuffer(val2, value, ref offset);

        foreach(byte b in val2.Span)

        {

            Console.Write($"{b:X2} ");

        }

        Console.WriteLine();

        MemoryExtensions2.WriteToBuffer(val2, value2, ref offset);

        foreach(byte b in val2.Span)

        {

            Console.Write($"{b:X2} ");

        }

        Console.WriteLine();

        MemoryExtensions2.WriteToBuffer(val2, value, ref offset);

        foreach(byte b in val2.Span)

        {

            Console.Write($"{b:X2} ");

        }

        Console.WriteLine();

    }

}

public static class MemoryExtensions2

{

    public static void WriteToBuffer<T>(this Memory<byte> buffer, T value, ref int offset) where T : unmanaged

    {

        Span<T> span = MemoryMarshal.CreateSpan(ref value, 1);

        Span<byte> data = MemoryMarshal.AsBytes(span);

        int size = data.Length;

        data.CopyTo(buffer[offset .. (offset + size)].Span);

        for(int i = 0; i < size; i++)

        {

            if( data[i] == 0)

            {

                size = i;

                break;

            }

        }

        offset += size;

    }   

}