Update archtype ecs

Ghost.ArcEntities/Entity.cs

@@ -0,0 +1,81 @@
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+
+namespace Ghost.ArcEntities;
+
+[StructLayout(LayoutKind.Sequential, Size = 8)]
+public struct Entity : IEquatable<Entity>, IComparable<Entity>
+{
+    public const EntityID INVALID_ID = -1;
+
+    private EntityID _id;
+    private GenerationID _generation;
+
+    public readonly EntityID ID
+    {
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        get => _id;
+    }
+
+    public readonly GenerationID Generation
+    {
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        get => _generation;
+    }
+
+    public readonly bool IsValid
+    {
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        get => ID != INVALID_ID;
+    }
+
+    public static Entity Invalid
+    {
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        get => new(INVALID_ID, GenerationID.MaxValue);
+    }
+
+    internal Entity(EntityID id, GenerationID generation)
+    {
+        _id = id;
+        _generation = generation;
+    }
+
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    internal void IncrementGeneration() => _generation++;
+
+    public readonly bool Equals(Entity other)
+    {
+        return _id == other._id && _generation == other._generation;
+    }
+
+    public readonly int CompareTo(Entity other)
+    {
+        return _id.CompareTo(other._id);
+    }
+
+    public override readonly bool Equals(object? obj)
+    {
+        return obj is Entity other && Equals(other);
+    }
+
+    public override readonly int GetHashCode()
+    {
+        return _id.GetHashCode();
+    }
+
+    public static bool operator ==(Entity left, Entity right)
+    {
+        return left.Equals(right);
+    }
+
+    public static bool operator !=(Entity left, Entity right)
+    {
+        return !(left == right);
+    }
+
+    public override readonly string ToString()
+    {
+        return $"Entity {{ Index: {ID}, Generation: {Generation} }}";
+    }
+}