lyra-wasm-scripting-test/dotnet-guest-test/ExampleWorldImpl.cs

namespace ExampleWorld;//.wit.exports.component.witguest;

using System.Diagnostics.CodeAnalysis;
using System.Runtime.InteropServices;
using ExampleWorld.wit.imports.lyra.api;

[StructLayout(LayoutKind.Sequential)]
struct Vec3(float x, float y, float z)
{
    public const ulong TypeId = 4124409524;
    public float X { get; set; } = x;
    public float Y { get; set; } = y;
    public float Z { get; set; } = z;

    public const ulong HostSize = sizeof(float) * 3;
}

public class ExampleWorldImpl : IExampleWorld
{
    internal struct AlignmentHelper<T> where T : unmanaged
    {
        public byte Padding;
        public T Target;
    }

    private static int AlignmentOf<T>() where T : unmanaged
    {
        return (int)Marshal.OffsetOf<AlignmentHelper<T>>(nameof(AlignmentHelper<T>.Target));
    }

    private static byte[] GetBytes<T>([DisallowNull] T data) {
        int size = Marshal.SizeOf(data);
        byte[] arr = new byte[size];

        IntPtr ptr = IntPtr.Zero;
        try
        {
            ptr = Marshal.AllocHGlobal(size);
            Marshal.StructureToPtr(data, ptr, true);
            Marshal.Copy(ptr, arr, 0, size);
        }
        finally
        {
            Marshal.FreeHGlobal(ptr);
        }
        return arr;
    }

    private static T? FromBytes<T>(byte[] data) where T : struct
    {
        var ptr = GCHandle.Alloc(data, GCHandleType.Pinned);
        try {
            var res = (T?) Marshal.PtrToStructure(ptr.AddrOfPinnedObject(), typeof(T));
            return res;
        } finally {
            ptr.Free();

        }
    }

    public static void OnInit(IEcs.EcsWorld gameWorld, IEcs.Entity owningEntity)
    {   
        var size = new IEcs.WasmTypeId((Vec3.TypeId, 0));
        var info = new IEcs.ComponentInfo("Vec3", (ulong) Marshal.SizeOf<Vec3>(), (ulong) AlignmentOf<Vec3>(), size);
        var pos = new Vec3(7.0f, 30.0f, 18.0f);
        var infos = new List<IEcs.ComponentInfo>
        {
            info
        };
        
        IEcs.Entity entity = gameWorld.Spawn(GetBytes(pos), infos);
        Console.WriteLine("C#:   Spawned {0}", entity.id.id);

        IEcs.EcsDynamicView res = gameWorld.View(infos);
        (IEcs.Entity, byte[])? row = res.Next();
        
        if (row.HasValue) {
            Console.WriteLine("C#:   Found position!!!");

            var en = row.Value.Item1;
            var comp = FromBytes<Vec3>(row.Value.Item2);

            Console.WriteLine("C#:   Found component at ({0}, {1}, {2})", comp?.X, comp?.Y, comp?.Z);
        } else {
            Console.WriteLine("C#:   Could not find position");
        }
    }

    public static void OnUpdate(IEcs.EcsWorld gameWorld, IEcs.Entity owningEntity)
    {
        throw new NotImplementedException();
    }
}