System.Buffers.MemoryManager<T> is adapted

src/ImageSharp/Memory/ArrayPoolMemoryManager.Buffer{T}.cs

@@ -15,7 +15,7 @@ namespace SixLabors.ImageSharp.Memory
         /// <summary>
         /// The buffer implementation of <see cref="ArrayPoolMemoryManager"/>
         /// </summary>
-        private class Buffer<T> : IBuffer<T>
+        private class Buffer<T> : ManagedBufferBase<T>, IBuffer<T>
             where T : struct
         {
             /// <summary>
@@ -45,12 +45,9 @@ namespace SixLabors.ImageSharp.Memory
             protected byte[] Data { get; private set; }
 
             /// <inheritdoc />
-            public Span<T> GetSpan() => MemoryMarshal.Cast<byte, T>(this.Data.AsSpan()).Slice(0, this.length);
-
-            /// <inheritdoc />
-            public void Dispose()
+            protected override void Dispose(bool disposing)
             {
-                if (this.Data == null || this.sourcePoolReference == null)
+                if (!disposing || this.Data == null || this.sourcePoolReference == null)
                 {
                     return;
                 }
@@ -63,6 +60,10 @@ namespace SixLabors.ImageSharp.Memory
                 this.sourcePoolReference = null;
                 this.Data = null;
             }
+
+            public override Span<T> GetSpan() => MemoryMarshal.Cast<byte, T>(this.Data.AsSpan()).Slice(0, this.length);
+
+            protected override object GetPinnableObject() => this.Data;
         }
 
         /// <summary>

src/ImageSharp/Memory/BasicArrayBuffer.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Buffers;
 using System.Runtime.CompilerServices;
 
 namespace SixLabors.ImageSharp.Memory
@@ -6,7 +7,7 @@ namespace SixLabors.ImageSharp.Memory
     /// <summary>
     /// Exposes an array through the <see cref="IBuffer{T}"/> interface.
     /// </summary>
-    internal class BasicArrayBuffer<T> : IBuffer<T>
+    internal class BasicArrayBuffer<T> : ManagedBufferBase<T>, IBuffer<T>
         where T : struct
     {
         public BasicArrayBuffer(T[] array, int length)
@@ -42,11 +43,15 @@ namespace SixLabors.ImageSharp.Memory
             }
         }
 
-        /// <inheritdoc />
-        public Span<T> GetSpan() => this.Array.AsSpan(0, this.Length);
+        protected override void Dispose(bool disposing)
+        {
+        }
+
+        public override Span<T> GetSpan() => this.Array.AsSpan(0, this.Length);
 
-        public void Dispose()
+        protected override object GetPinnableObject()
         {
+            return this.Array;
         }
     }
 }

src/ImageSharp/Memory/BufferExtensions.cs

@@ -10,6 +10,22 @@ namespace SixLabors.ImageSharp.Memory
 {
     internal static class BufferExtensions
     {
+        public static Memory<T> GetMemory<T>(this IBuffer<T> buffer)
+            where T : struct
+        {
+            System.Buffers.MemoryManager<T> bufferManager = buffer as System.Buffers.MemoryManager<T>;
+
+            if (bufferManager == null)
+            {
+                // TODO: We need a better way to integrate IBuffer<T> with MemoryManager<T>. The prior should probably entirely replace the latter!
+                throw new ArgumentException(
+                    "BufferExtensions.GetMemory<T>(buffer): buffer should be convertable to System.Buffers.MemoryManager<T>!",
+                    nameof(buffer));
+            }
+
+            return bufferManager.Memory;
+        }
+
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static int Length<T>(this IBuffer<T> buffer)
             where T : struct => buffer.GetSpan().Length;

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

@@ -8,6 +8,7 @@ namespace SixLabors.ImageSharp.Memory
     /// <inheritdoc />
     /// <summary>
     /// Represents a contigous memory buffer of value-type items "promising" a <see cref="Span{T}"/>
+    /// A proper im
     /// </summary>
     /// <typeparam name="T">The value type</typeparam>
     internal interface IBuffer<T> : IDisposable

src/ImageSharp/Memory/ManagedBufferBase.cs

@@ -0,0 +1,40 @@
+// Copyright (c) Six Labors and contributors.
+// Licensed under the Apache License, Version 2.0.
+
+using System.Buffers;
+using System.Runtime.InteropServices;
+
+namespace SixLabors.ImageSharp.Memory
+{
+    /// <summary>
+    /// Provides a base class for <see cref="IBuffer{T}"/> implementations by implementing pinning logic for <see cref="MemoryManager{T}"/> adaption.
+    /// </summary>
+    internal abstract class ManagedBufferBase<T> : System.Buffers.MemoryManager<T>
+    {
+        private GCHandle pinHandle;
+
+        /// <summary>
+        /// Gets the object that should be pinned.
+        /// </summary>
+        protected abstract object GetPinnableObject();
+
+        public override unsafe MemoryHandle Pin(int elementIndex = 0)
+        {
+            if (!this.pinHandle.IsAllocated)
+            {
+                this.pinHandle = GCHandle.Alloc(this.GetPinnableObject(), GCHandleType.Pinned);
+            }
+
+            void* ptr = (void*)this.pinHandle.AddrOfPinnedObject();
+            return new MemoryHandle(ptr, this.pinHandle);
+        }
+
+        public override void Unpin()
+        {
+            if (this.pinHandle.IsAllocated)
+            {
+                this.pinHandle.Free();
+            }
+        }
+    }
+}

tests/ImageSharp.Tests/Memory/BufferTestSuite.cs

@@ -10,7 +10,7 @@ using Xunit;
 
 namespace SixLabors.ImageSharp.Tests.Memory
 {
-    
+    using System.Buffers;
 
     /// <summary>
     /// Inherit this class to test an <see cref="IBuffer{T}"/> implementation (provided by <see cref="MemoryManager"/>).
@@ -282,5 +282,40 @@ namespace SixLabors.ImageSharp.Tests.Memory
                 Assert.True(buffer.Array.Length >= buffer.GetSpan().Length);
             }
         }
+
+        [Fact]
+        public void GetMemory_ReturnsValidMemory()
+        {
+            using (IBuffer<CustomStruct> buffer = this.MemoryManager.Allocate<CustomStruct>(42))
+            {
+                Span<CustomStruct> span0 = buffer.GetSpan();
+                span0[10].A = 30;
+                Memory<CustomStruct> memory = buffer.GetMemory();
+                
+                Assert.Equal(42, memory.Length);
+                Span<CustomStruct> span1 = memory.Span;
+
+                Assert.Equal(42, span1.Length);
+                Assert.Equal(30, span1[10].A);
+            }
+        }
+
+        [Fact]
+        public unsafe void GetMemory_ResultIsPinnable()
+        {
+            using (IBuffer<int> buffer = this.MemoryManager.Allocate<int>(42))
+            {
+                Span<int> span0 = buffer.GetSpan();
+                span0[10] = 30;
+
+                Memory<int> memory = buffer.GetMemory();
+
+                using (MemoryHandle h = memory.Pin())
+                {
+                    int* ptr = (int*) h.Pointer;
+                    Assert.Equal(30, ptr[10]);
+                }
+            }
+        }
     }
 }