Fix AV when indexing a sliced Memory2D<T> backed by custom MemoryManager<T>

src/CommunityToolkit.HighPerformance/Buffers/Internals/ArrayMemoryManager{TFrom,TTo}.cs

@@ -75,15 +75,15 @@ public override unsafe MemoryHandle Pin(int elementIndex = 0)
             ThrowArgumentOutOfRangeExceptionForInvalidIndex();
         }
 
-        int bytePrefix = this.offset * sizeof(TFrom);
-        int byteSuffix = elementIndex * sizeof(TTo);
-        int byteOffset = bytePrefix + byteSuffix;
+        nint bytePrefix = this.offset * sizeof(TFrom);
+        nint byteSuffix = elementIndex * sizeof(TTo);
+        nint byteOffset = bytePrefix + byteSuffix;
 
         GCHandle handle = GCHandle.Alloc(this.array, GCHandleType.Pinned);
 
         ref TFrom r0 = ref this.array.DangerousGetReference();
         ref byte r1 = ref Unsafe.As<TFrom, byte>(ref r0);
-        ref byte r2 = ref Unsafe.Add(ref r1, byteOffset);
+        ref byte r2 = ref Unsafe.AddByteOffset(ref r1, byteOffset);
         void* pi = Unsafe.AsPointer(ref r2);
 
         return new(pi, handle);

src/CommunityToolkit.HighPerformance/Buffers/Internals/StringMemoryManager{TTo}.cs

@@ -71,15 +71,15 @@ public override unsafe MemoryHandle Pin(int elementIndex = 0)
             ThrowArgumentOutOfRangeExceptionForInvalidIndex();
         }
 
-        int bytePrefix = this.offset * sizeof(char);
-        int byteSuffix = elementIndex * sizeof(TTo);
-        int byteOffset = bytePrefix + byteSuffix;
+        nint bytePrefix = this.offset * sizeof(char);
+        nint byteSuffix = elementIndex * sizeof(TTo);
+        nint byteOffset = bytePrefix + byteSuffix;
 
         GCHandle handle = GCHandle.Alloc(this.text, GCHandleType.Pinned);
 
         ref char r0 = ref this.text.DangerousGetReference();
         ref byte r1 = ref Unsafe.As<char, byte>(ref r0);
-        ref byte r2 = ref Unsafe.Add(ref r1, byteOffset);
+        ref byte r2 = ref Unsafe.AddByteOffset(ref r1, byteOffset);
         void* pi = Unsafe.AsPointer(ref r2);
 
         return new(pi, handle);

src/CommunityToolkit.HighPerformance/Memory/Memory2D{T}.cs

@@ -37,9 +37,9 @@ namespace CommunityToolkit.HighPerformance;
     private readonly object? instance;
 
     /// <summary>
-    /// The initial offset within <see cref="instance"/>.
+    /// The initial byte offset within <see cref="instance"/>.
     /// </summary>
-    private readonly IntPtr offset;
+    private readonly nint offset;
 
     /// <summary>
     /// The height of the specified 2D region.
@@ -603,7 +603,7 @@ public Span2D<T> Span
                 if (this.instance is MemoryManager<T> memoryManager)
                 {
                     ref T r0 = ref memoryManager.GetSpan().DangerousGetReference();
-                    ref T r1 = ref Unsafe.Add(ref r0, this.offset);
+                    ref T r1 = ref Unsafe.AddByteOffset(ref r0, this.offset);
 
                     return new(ref r1, this.height, this.width, this.pitch);
                 }

src/CommunityToolkit.HighPerformance/Memory/ReadOnlyMemory2D{T}.cs

@@ -34,9 +34,9 @@ namespace CommunityToolkit.HighPerformance;
     private readonly object? instance;
 
     /// <summary>
-    /// The initial offset within <see cref="instance"/>.
+    /// The initial byte offset within <see cref="instance"/>.
     /// </summary>
-    private readonly IntPtr offset;
+    private readonly nint offset;
 
     /// <summary>
     /// The height of the specified 2D region.
@@ -615,7 +615,7 @@ public ReadOnlySpan2D<T> Span
                 if (this.instance is MemoryManager<T> memoryManager)
                 {
                     ref T r0 = ref memoryManager.GetSpan().DangerousGetReference();
-                    ref T r1 = ref Unsafe.Add(ref r0, this.offset);
+                    ref T r1 = ref Unsafe.AddByteOffset(ref r0, this.offset);
 
                     return new(in r1, this.height, this.width, this.pitch);
                 }

src/CommunityToolkit.HighPerformance/Memory/ReadOnlySpan2D{T}.Enumerator.cs

@@ -109,9 +109,9 @@ public ref struct Enumerator
         private readonly object? instance;
 
         /// <summary>
-        /// The initial offset within <see cref="instance"/>.
+        /// The initial byte offset within <see cref="instance"/>.
         /// </summary>
-        private readonly IntPtr offset;
+        private readonly nint offset;
 
         /// <summary>
         /// The height of the specified 2D region.

src/CommunityToolkit.HighPerformance/Memory/ReadOnlySpan2D{T}.cs

@@ -50,9 +50,9 @@ public readonly ref partial struct ReadOnlySpan2D<T>
     private readonly object? instance;
 
     /// <summary>
-    /// The initial offset within <see cref="instance"/>.
+    /// The initial byte offset within <see cref="instance"/>.
     /// </summary>
-    private readonly IntPtr offset;
+    private readonly nint offset;
 
     /// <summary>
     /// The height of the specified 2D region.

src/CommunityToolkit.HighPerformance/Memory/Span2D{T}.Enumerator.cs

@@ -109,9 +109,9 @@ public ref struct Enumerator
         private readonly object? instance;
 
         /// <summary>
-        /// The initial offset within <see cref="instance"/>.
+        /// The initial byte offset within <see cref="instance"/>.
         /// </summary>
-        private readonly IntPtr offset;
+        private readonly nint offset;
 
         /// <summary>
         /// The height of the specified 2D region.

src/CommunityToolkit.HighPerformance/Memory/Span2D{T}.cs

@@ -82,9 +82,9 @@ public readonly ref partial struct Span2D<T>
     internal readonly object? Instance;
 
     /// <summary>
-    /// The initial offset within <see cref="Instance"/>.
+    /// The initial byte offset within <see cref="Instance"/>.
     /// </summary>
-    internal readonly IntPtr Offset;
+    internal readonly nint Offset;
 
     /// <summary>
     /// The height of the specified 2D region.

tests/CommunityToolkit.HighPerformance.UnitTests/Memory/Test_Memory2D{T}.cs

@@ -516,4 +516,29 @@ public void Test_Memory2DT_ToString()
 
         Assert.AreEqual(text, expected);
     }
+
+#if NET6_0_OR_GREATER
+    // See https://github.com/CommunityToolkit/WindowsCommunityToolkit/issues/3536
+    [TestMethod]
+    [DataRow(720, 1280)]
+    public void Test_Memory2DT_CastAndSlice_WorksCorrectly(int height, int width)
+    {
+        Memory2D<int> data =
+            new byte[width * height * sizeof(int)]
+            .AsMemory()
+            .Cast<byte, int>()
+            .AsMemory2D(height: height, width: width);
+
+        Memory2D<int> slice = data.Slice(
+            row: height / 2,
+            column: 0,
+            height: height / 2,
+            width: width);
+
+        Assert.IsTrue(Unsafe.AreSame(ref data.Span[height / 2, 0], ref slice.Span[0, 0]));
+        Assert.IsTrue(Unsafe.AreSame(ref data.Span[height / 2, width - 1], ref slice.Span[0, width - 1]));
+        Assert.IsTrue(Unsafe.AreSame(ref data.Span[height - 1, 0], ref slice.Span[(height / 2) - 1, 0]));
+        Assert.IsTrue(Unsafe.AreSame(ref data.Span[height - 1, width - 1], ref slice.Span[(height / 2) - 1, width - 1]));
+    }
+#endif
 }

tests/CommunityToolkit.HighPerformance.UnitTests/Memory/Test_ReadOnlyMemory2D{T}.cs

@@ -464,4 +464,29 @@ public void Test_ReadOnlyMemory2DT_ToString()
 
         Assert.AreEqual(text, expected);
     }
+
+#if NET6_0_OR_GREATER
+    // See https://github.com/CommunityToolkit/WindowsCommunityToolkit/issues/3536
+    [TestMethod]
+    [DataRow(720, 1280)]
+    public void Test_ReadOnlyMemory2DT_CastAndSlice_WorksCorrectly(int height, int width)
+    {
+        ReadOnlyMemory2D<int> data =
+            new byte[width * height * sizeof(int)]
+            .AsMemory()
+            .Cast<byte, int>()
+            .AsMemory2D(height: height, width: width);
+
+        ReadOnlyMemory2D<int> slice = data.Slice(
+            row: height / 2,
+            column: 0,
+            height: height / 2,
+            width: width);
+
+        Assert.IsTrue(Unsafe.AreSame(ref Unsafe.AsRef(in data.Span[height / 2, 0]), ref Unsafe.AsRef(in slice.Span[0, 0])));
+        Assert.IsTrue(Unsafe.AreSame(ref Unsafe.AsRef(in data.Span[height / 2, width - 1]), ref Unsafe.AsRef(in slice.Span[0, width - 1])));
+        Assert.IsTrue(Unsafe.AreSame(ref Unsafe.AsRef(in data.Span[height - 1, 0]), ref Unsafe.AsRef(in slice.Span[(height / 2) - 1, 0])));
+        Assert.IsTrue(Unsafe.AreSame(ref Unsafe.AsRef(in data.Span[height - 1, width - 1]), ref Unsafe.AsRef(in slice.Span[(height / 2) - 1, width - 1])));
+    }
+#endif
 }