MemoryMarshal.Cast challenge

memorymarshal_cast_utf8.cs

using System;
using System.Runtime.InteropServices;
using System.Text;

class Program
{
    static void Main(string[] args)
    {
        {
            // the text below is meaningless
            const string text = "abcdefg=䈀㰀笀稀瀀㸀㨀㴀椀栀最㬀昀㼀攀搀挀愀䀀䄀䈀㰀笀稀瀀㸀㨀㴀椀栀最㬀昀㼀攀搀挀愀䀀䄀䈀㰀";
            Console.WriteLine(text.ToString());
            Console.WriteLine($"UTF-16 length: {text.Length} chars"); // 50 chars
            Console.WriteLine($"UTF-8 length: {Encoding.UTF8.GetByteCount(text)} bytes"); // 134 bytes
            Console.WriteLine();

            Span<char> textAsSpan = text.ToCharArray();

            Console.WriteLine(textAsSpan.ToString());
            Console.WriteLine($"UTF-16 length: {textAsSpan.Length} chars");
            Console.WriteLine($"UTF-8 length: {Encoding.UTF8.GetByteCount(textAsSpan)} bytes");
            Console.WriteLine();
            
            textAsSpan = MemoryMarshal.Cast<byte, char>(new byte[4096].AsSpan(1));
            text.AsSpan().CopyTo(textAsSpan);
            textAsSpan = textAsSpan[0..text.Length];

            Console.WriteLine(textAsSpan.ToString());
            Console.WriteLine($"UTF-16 length: {textAsSpan.Length} chars");
            Console.WriteLine($"UTF-8 length: {Encoding.UTF8.GetByteCount(textAsSpan)} bytes");
            Console.WriteLine();
        }

        Console.WriteLine();

        {
            const string text = "The quick brown fox jumps over the lazy dog.";
            byte[] textAsUtf8 = Encoding.UTF8.GetBytes(text);

            Span<char> destination = new char[2048];
            int charsWritten = Encoding.UTF8.GetChars(textAsUtf8, destination);
            destination = destination[0..charsWritten];

            Console.WriteLine(destination.ToString());
            Console.WriteLine();

            destination = MemoryMarshal.Cast<byte, char>(new byte[4096].AsSpan(1));
            charsWritten = Encoding.UTF8.GetChars(textAsUtf8, destination);
            destination = destination[0..charsWritten];

            Console.WriteLine(destination.ToString());
            Console.WriteLine();
        }
    }
}