implement review suggestions

src/ImageSharp/Advanced/AdvancedImageExtensions.cs

@@ -61,7 +61,7 @@ namespace SixLabors.ImageSharp.Advanced
         /// </remarks>
         public static IMemoryGroup<TPixel> GetPixelMemoryGroup<TPixel>(this ImageFrame<TPixel> source)
             where TPixel : struct, IPixel<TPixel>
-            => source?.PixelBuffer.MemoryGroup.View ?? throw new ArgumentNullException(nameof(source));
+            => source?.PixelBuffer.FastMemoryGroup.View ?? throw new ArgumentNullException(nameof(source));
 
         /// <summary>
         /// Gets the representation of the pixels as a <see cref="IMemoryGroup{T}"/> containing the backing pixel data of the image

src/ImageSharp/Image.Decode.cs

@@ -36,7 +36,7 @@ namespace SixLabors.ImageSharp
         {
             Buffer2D<TPixel> uninitializedMemoryBuffer =
                 configuration.MemoryAllocator.Allocate2D<TPixel>(width, height);
-            return new Image<TPixel>(configuration, uninitializedMemoryBuffer.MemoryGroup, width, height, metadata);
+            return new Image<TPixel>(configuration, uninitializedMemoryBuffer.FastMemoryGroup, width, height, metadata);
         }
 
         /// <summary>

src/ImageSharp/Image.LoadPixelData.cs

@@ -120,7 +120,7 @@ namespace SixLabors.ImageSharp
 
             var image = new Image<TPixel>(config, width, height);
             data = data.Slice(0, count);
-            data.CopyTo(image.Frames.RootFrame.PixelBuffer.MemoryGroup);
+            data.CopyTo(image.Frames.RootFrame.PixelBuffer.FastMemoryGroup);
 
             return image;
         }

src/ImageSharp/ImageFrame.LoadPixelData.cs

@@ -45,7 +45,7 @@ namespace SixLabors.ImageSharp
             var image = new ImageFrame<TPixel>(configuration, width, height);
 
             data = data.Slice(0, count);
-            data.CopyTo(image.PixelBuffer.MemoryGroup);
+            data.CopyTo(image.PixelBuffer.FastMemoryGroup);
 
             return image;
         }

src/ImageSharp/ImageFrameCollection{TPixel}.cs

@@ -351,7 +351,7 @@ namespace SixLabors.ImageSharp
                 this.parent.GetConfiguration(),
                 source.Size(),
                 source.Metadata.DeepClone());
-            source.CopyPixelsTo(result.PixelBuffer.MemoryGroup);
+            source.CopyPixelsTo(result.PixelBuffer.FastMemoryGroup);
             return result;
         }
     }

src/ImageSharp/ImageFrame{TPixel}.cs

@@ -131,7 +131,7 @@ namespace SixLabors.ImageSharp
             Guard.NotNull(source, nameof(source));
 
             this.PixelBuffer = this.GetConfiguration().MemoryAllocator.Allocate2D<TPixel>(source.PixelBuffer.Width, source.PixelBuffer.Height);
-            source.PixelBuffer.MemoryGroup.CopyTo(this.PixelBuffer.MemoryGroup);
+            source.PixelBuffer.FastMemoryGroup.CopyTo(this.PixelBuffer.FastMemoryGroup);
         }
 
         /// <summary>
@@ -186,7 +186,7 @@ namespace SixLabors.ImageSharp
                 throw new ArgumentException("ImageFrame<TPixel>.CopyTo(): target must be of the same size!", nameof(target));
             }
 
-            this.PixelBuffer.MemoryGroup.CopyTo(target.MemoryGroup);
+            this.PixelBuffer.FastMemoryGroup.CopyTo(target.FastMemoryGroup);
         }
 
         /// <summary>
@@ -222,7 +222,7 @@ namespace SixLabors.ImageSharp
         {
             if (typeof(TPixel) == typeof(TDestinationPixel))
             {
-                this.PixelBuffer.MemoryGroup.TransformTo(destination, (s, d) =>
+                this.PixelBuffer.FastMemoryGroup.TransformTo(destination, (s, d) =>
                 {
                     Span<TPixel> d1 = MemoryMarshal.Cast<TDestinationPixel, TPixel>(d);
                     s.CopyTo(d1);
@@ -230,7 +230,7 @@ namespace SixLabors.ImageSharp
                 return;
             }
 
-            this.PixelBuffer.MemoryGroup.TransformTo(destination, (s, d) =>
+            this.PixelBuffer.FastMemoryGroup.TransformTo(destination, (s, d) =>
             {
                 PixelOperations<TPixel>.Instance.To(this.GetConfiguration(), s, d);
             });
@@ -291,7 +291,7 @@ namespace SixLabors.ImageSharp
         /// <param name="value">The value to initialize the bitmap with.</param>
         internal void Clear(TPixel value)
         {
-            MemoryGroup<TPixel> group = this.PixelBuffer.MemoryGroup;
+            MemoryGroup<TPixel> group = this.PixelBuffer.FastMemoryGroup;
 
             if (value.Equals(default))
             {

src/ImageSharp/Memory/Buffer2DExtensions.cs

@@ -24,7 +24,7 @@ namespace SixLabors.ImageSharp.Memory
             where T : struct
         {
             Guard.NotNull(buffer, nameof(buffer));
-            return buffer.MemoryGroup.View;
+            return buffer.FastMemoryGroup.View;
         }
 
         /// <summary>
@@ -42,12 +42,12 @@ namespace SixLabors.ImageSharp.Memory
             where T : struct
         {
             Guard.NotNull(buffer, nameof(buffer));
-            if (buffer.MemoryGroup.Count > 1)
+            if (buffer.FastMemoryGroup.Count > 1)
             {
                 throw new InvalidOperationException("GetSingleSpan is only valid for a single-buffer group!");
             }
 
-            return buffer.MemoryGroup.Single().Span;
+            return buffer.FastMemoryGroup.Single().Span;
         }
 
         /// <summary>
@@ -65,12 +65,12 @@ namespace SixLabors.ImageSharp.Memory
             where T : struct
         {
             Guard.NotNull(buffer, nameof(buffer));
-            if (buffer.MemoryGroup.Count > 1)
+            if (buffer.FastMemoryGroup.Count > 1)
             {
                 throw new InvalidOperationException("GetSingleMemory is only valid for a single-buffer group!");
             }
 
-            return buffer.MemoryGroup.Single();
+            return buffer.FastMemoryGroup.Single();
         }
 
         /// <summary>

src/ImageSharp/Memory/Buffer2D{T}.cs

@@ -28,7 +28,7 @@ namespace SixLabors.ImageSharp.Memory
         /// <param name="height">The number of rows.</param>
         internal Buffer2D(MemoryGroup<T> memoryGroup, int width, int height)
         {
-            this.MemoryGroup = memoryGroup;
+            this.FastMemoryGroup = memoryGroup;
             this.Width = width;
             this.Height = height;
 
@@ -49,14 +49,20 @@ namespace SixLabors.ImageSharp.Memory
         public int Height { get; private set; }
 
         /// <summary>
-        /// Gets the backing <see cref="MemoryGroup{T}"/>.
+        /// Gets the backing <see cref="IMemoryGroup{T}"/>.
+        /// </summary>
+        /// <returns>The MemoryGroup.</returns>
+        public IMemoryGroup<T> MemoryGroup => this.FastMemoryGroup.View;
+
+        /// <summary>
+        /// Gets the backing <see cref="MemoryGroup{T}"/> without the view abstraction.
         /// </summary>
         /// <remarks>
         /// This property has been kept internal intentionally.
-        /// It's public counterpart is <see cref="Buffer2DExtensions.GetMemoryGroup{T}"/>,
+        /// It's public counterpart is <see cref="MemoryGroup"/>,
         /// which only exposes the view of the MemoryGroup.
         /// </remarks>
-        internal MemoryGroup<T> MemoryGroup { get; }
+        internal MemoryGroup<T> FastMemoryGroup { get; }
 
         /// <summary>
         /// Gets a reference to the element at the specified position.
@@ -64,9 +70,10 @@ namespace SixLabors.ImageSharp.Memory
         /// <param name="x">The x coordinate (row)</param>
         /// <param name="y">The y coordinate (position at row)</param>
         /// <returns>A reference to the element.</returns>
-        internal ref T this[int x, int y]
+        /// <exception cref="IndexOutOfRangeException">When index is out of range of the buffer.</exception>
+        public ref T this[int x, int y]
         {
-            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            [MethodImpl(InliningOptions.ShortMethod)]
             get
             {
                 DebugGuard.MustBeGreaterThanOrEqualTo(x, 0, nameof(x));
@@ -83,7 +90,7 @@ namespace SixLabors.ImageSharp.Memory
         /// </summary>
         public void Dispose()
         {
-            this.MemoryGroup.Dispose();
+            this.FastMemoryGroup.Dispose();
             this.cachedMemory = default;
         }
 
@@ -148,7 +155,7 @@ namespace SixLabors.ImageSharp.Memory
         {
             DebugGuard.MustBeGreaterThanOrEqualTo(y, 0, nameof(y));
             DebugGuard.MustBeLessThan(y, this.Height, nameof(y));
-            return this.MemoryGroup.View.GetBoundedSlice(y * this.Width, this.Width);
+            return this.FastMemoryGroup.View.GetBoundedSlice(y * this.Width, this.Width);
         }
 
         /// <summary>
@@ -157,12 +164,12 @@ namespace SixLabors.ImageSharp.Memory
         /// </summary>
         internal static void SwapOrCopyContent(Buffer2D<T> destination, Buffer2D<T> source)
         {
-            bool swap = MemoryGroup<T>.SwapOrCopyContent(destination.MemoryGroup, source.MemoryGroup);
+            bool swap = MemoryGroup<T>.SwapOrCopyContent(destination.FastMemoryGroup, source.FastMemoryGroup);
             SwapOwnData(destination, source, swap);
         }
 
         [MethodImpl(InliningOptions.ColdPath)]
-        private Memory<T> GetRowMemorySlow(int y) => this.MemoryGroup.GetBoundedSlice(y * this.Width, this.Width);
+        private Memory<T> GetRowMemorySlow(int y) => this.FastMemoryGroup.GetBoundedSlice(y * this.Width, this.Width);
 
         [MethodImpl(InliningOptions.ColdPath)]
         private ref T GetElementSlow(int x, int y)

src/ImageSharp/Memory/BufferArea{T}.cs

@@ -94,7 +94,7 @@ namespace SixLabors.ImageSharp.Memory
             int xx = this.Rectangle.X;
             int width = this.Rectangle.Width;
 
-            return this.DestinationBuffer.MemoryGroup.GetBoundedSlice(yy + xx, width).Span;
+            return this.DestinationBuffer.FastMemoryGroup.GetBoundedSlice(yy + xx, width).Span;
         }
 
         /// <summary>
@@ -140,7 +140,7 @@ namespace SixLabors.ImageSharp.Memory
             // Optimization for when the size of the area is the same as the buffer size.
             if (this.IsFullBufferArea)
             {
-                this.DestinationBuffer.MemoryGroup.Clear();
+                this.DestinationBuffer.FastMemoryGroup.Clear();
                 return;
             }
 

src/ImageSharp/Memory/DiscontiguousBuffers/MemoryGroup{T}.Consumed.cs

@@ -11,7 +11,7 @@ namespace SixLabors.ImageSharp.Memory
     internal abstract partial class MemoryGroup<T>
     {
         // Analogous to the "consumed" variant of MemorySource
-        private class Consumed : MemoryGroup<T>
+        private sealed class Consumed : MemoryGroup<T>
         {
             private readonly Memory<T>[] source;
 

src/ImageSharp/Memory/DiscontiguousBuffers/MemoryGroup{T}.Owned.cs

@@ -11,7 +11,7 @@ namespace SixLabors.ImageSharp.Memory
     // Analogous to the "owned" variant of MemorySource
     internal abstract partial class MemoryGroup<T>
     {
-        private class Owned : MemoryGroup<T>
+        private sealed class Owned : MemoryGroup<T>
         {
             private IMemoryOwner<T>[] memoryOwners;
 
@@ -25,6 +25,8 @@ namespace SixLabors.ImageSharp.Memory
 
             public bool Swappable { get; }
 
+            private bool IsDisposed => this.memoryOwners == null;
+
             public override int Count
             {
                 get
@@ -51,7 +53,7 @@ namespace SixLabors.ImageSharp.Memory
 
             public override void Dispose()
             {
-                if (this.memoryOwners == null)
+                if (this.IsDisposed)
                 {
                     return;
                 }

tests/ImageSharp.Tests/Memory/Buffer2DTests.cs

@@ -46,8 +46,8 @@ namespace SixLabors.ImageSharp.Tests.Memory
             {
                 Assert.Equal(width, buffer.Width);
                 Assert.Equal(height, buffer.Height);
-                Assert.Equal(width * height, buffer.MemoryGroup.TotalLength);
+                Assert.Equal(width * height, buffer.FastMemoryGroup.TotalLength);
-                Assert.True(buffer.MemoryGroup.BufferLength % width == 0);
+                Assert.True(buffer.FastMemoryGroup.BufferLength % width == 0);
             }
         }
 
@@ -64,7 +64,7 @@ namespace SixLabors.ImageSharp.Tests.Memory
             {
                 Assert.Equal(width, buffer.Width);
                 Assert.Equal(height, buffer.Height);
-                Assert.Equal(0, buffer.MemoryGroup.TotalLength);
+                Assert.Equal(0, buffer.FastMemoryGroup.TotalLength);
                 Assert.Equal(0, buffer.GetSingleSpan().Length);
             }
         }
@@ -76,7 +76,7 @@ namespace SixLabors.ImageSharp.Tests.Memory
             this.MemoryAllocator.BufferCapacityInBytes = sizeof(int) * bufferCapacity;
 
             using Buffer2D<int> buffer = this.MemoryAllocator.Allocate2DOveraligned<int>(width, height, alignmentMultiplier);
-            MemoryGroup<int> memoryGroup = buffer.MemoryGroup;
+            MemoryGroup<int> memoryGroup = buffer.FastMemoryGroup;
             int expectedAlignment = width * alignmentMultiplier;
 
             Assert.Equal(expectedAlignment, memoryGroup.BufferLength);
@@ -113,8 +113,8 @@ namespace SixLabors.ImageSharp.Tests.Memory
 
                 Assert.Equal(width, span.Length);
 
-                int expectedSubBufferOffset = (width * y) - (expectedBufferIndex * buffer.MemoryGroup.BufferLength);
+                int expectedSubBufferOffset = (width * y) - (expectedBufferIndex * buffer.FastMemoryGroup.BufferLength);
-                Assert.SpanPointsTo(span, buffer.MemoryGroup[expectedBufferIndex], expectedSubBufferOffset);
+                Assert.SpanPointsTo(span, buffer.FastMemoryGroup[expectedBufferIndex], expectedSubBufferOffset);
             }
         }
 
@@ -172,10 +172,10 @@ namespace SixLabors.ImageSharp.Tests.Memory
 
             using (Buffer2D<TestStructs.Foo> buffer = this.MemoryAllocator.Allocate2D<TestStructs.Foo>(width, height))
             {
-                int bufferIndex = (width * y) / buffer.MemoryGroup.BufferLength;
+                int bufferIndex = (width * y) / buffer.FastMemoryGroup.BufferLength;
-                int subBufferStart = (width * y) - (bufferIndex * buffer.MemoryGroup.BufferLength);
+                int subBufferStart = (width * y) - (bufferIndex * buffer.FastMemoryGroup.BufferLength);
 
-                Span<TestStructs.Foo> span = buffer.MemoryGroup[bufferIndex].Span.Slice(subBufferStart);
+                Span<TestStructs.Foo> span = buffer.FastMemoryGroup[bufferIndex].Span.Slice(subBufferStart);
 
                 ref TestStructs.Foo actual = ref buffer[x, y];
 
@@ -194,13 +194,13 @@ namespace SixLabors.ImageSharp.Tests.Memory
                 a[1, 3] = 666;
                 b[1, 3] = 444;
 
-                Memory<int> aa = a.MemoryGroup.Single();
+                Memory<int> aa = a.FastMemoryGroup.Single();
-                Memory<int> bb = b.MemoryGroup.Single();
+                Memory<int> bb = b.FastMemoryGroup.Single();
 
                 Buffer2D<int>.SwapOrCopyContent(a, b);
 
-                Assert.Equal(bb, a.MemoryGroup.Single());
+                Assert.Equal(bb, a.FastMemoryGroup.Single());
-                Assert.Equal(aa, b.MemoryGroup.Single());
+                Assert.Equal(aa, b.FastMemoryGroup.Single());
 
                 Assert.Equal(new Size(3, 7), a.Size());
                 Assert.Equal(new Size(10, 5), b.Size());
@@ -287,5 +287,18 @@ namespace SixLabors.ImageSharp.Tests.Memory
                 }
             }
         }
+
+        [Fact]
+        public void PublicMemoryGroup_IsMemoryGroupView()
+        {
+            using Buffer2D<int> buffer1 = this.MemoryAllocator.Allocate2D<int>(10, 10);
+            using Buffer2D<int> buffer2 = this.MemoryAllocator.Allocate2D<int>(10, 10);
+            IMemoryGroup<int> mgBefore = buffer1.MemoryGroup;
+
+            Buffer2D<int>.SwapOrCopyContent(buffer1, buffer2);
+
+            Assert.False(mgBefore.IsValid);
+            Assert.NotSame(mgBefore, buffer1.MemoryGroup);
+        }
     }
 }

tests/ImageSharp.Tests/TestUtilities/ImageProviders/SolidProvider.cs

@@ -54,7 +54,7 @@ namespace SixLabors.ImageSharp.Tests
                 Image<TPixel> image = base.GetImage();
                 Color color = new Rgba32(this.r, this.g, this.b, this.a);
 
-                image.GetRootFramePixelBuffer().MemoryGroup.Fill(color.ToPixel<TPixel>());
+                image.GetRootFramePixelBuffer().FastMemoryGroup.Fill(color.ToPixel<TPixel>());
                 return image;
             }
 

tests/ImageSharp.Tests/TestUtilities/ReferenceCodecs/MagickReferenceDecoder.cs

@@ -54,7 +54,7 @@ namespace SixLabors.ImageSharp.Tests.TestUtilities.ReferenceCodecs
         {
             using var magickImage = new MagickImage(stream);
             var result = new Image<TPixel>(configuration, magickImage.Width, magickImage.Height);
-            MemoryGroup<TPixel> resultPixels = result.GetRootFramePixelBuffer().MemoryGroup;
+            MemoryGroup<TPixel> resultPixels = result.GetRootFramePixelBuffer().FastMemoryGroup;
 
             using (IPixelCollection pixels = magickImage.GetPixelsUnsafe())
             {