solve 'edge' case and pass cancellation token

Infra/Buffers/ImmovableMemory.cs

@@ -4,34 +4,48 @@ using System.Runtime.InteropServices;
 
 namespace StitchATon2.Infra.Buffers;
 
-internal sealed unsafe class ImmovableMemory<T> : MemoryManager<T> where T : unmanaged
+internal sealed unsafe class ImmovableMemory<T> : MemoryManager<T>, IBuffer<T> where T : unmanaged
 {
-    private readonly T* _pointer;
-    private readonly int _length;
+    internal readonly T* Pointer;
     private bool _disposed;
 
-    public ImmovableMemory(int count)
+    public ImmovableMemory(int length)
     {
-        _pointer = (T*)NativeMemory.Alloc((nuint)count, (nuint)Unsafe.SizeOf<T>());
-        _length = count;
+        Pointer = (T*)NativeMemory.Alloc((nuint)length, (nuint)Unsafe.SizeOf<T>());
+        Length = length;
     }
     
     protected override void Dispose(bool disposing)
     {
-        if (!_disposed)
-        {
-            NativeMemory.Free(_pointer);
-            _disposed = true;
-        }
+        if (_disposed) return;
+        NativeMemory.Free(Pointer);
+        _disposed = true;
     }
 
     public override Span<T> GetSpan()
-        => new(_pointer, _length);
+        => _disposed 
+            ? throw new ObjectDisposedException(nameof(ImmovableMemory<T>)) 
+            : new Span<T>(Pointer, Length);
 
     public override MemoryHandle Pin(int elementIndex = 0)
-        => new(_pointer + elementIndex);
+        => _disposed
+            ? throw new ObjectDisposedException(nameof(ImmovableMemory<T>))
+            : new MemoryHandle(Pointer + elementIndex);
 
     public override void Unpin()
     {
     }
+
+    public ref T this[int index]
+    {
+        get
+        {
+            if (_disposed) throw new ObjectDisposedException(nameof(ImmovableMemory<T>));
+            return ref Unsafe.AsRef<T>(Pointer + index);
+        }
+    }
+
+    public Span<T> Span => GetSpan();
+    
+    public int Length { get; }
 }