Added T[] and MemoryManager<T> owner types

Author: Sergio0694

Microsoft.Toolkit.HighPerformance/Streams/Sources/ArrayOwner.cs

@@ -0,0 +1,64 @@
+using System;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using Microsoft.Toolkit.HighPerformance.Extensions;
+
+namespace Microsoft.Toolkit.HighPerformance.Streams
+{
+    /// <summary>
+    /// An <see cref="ISpanOwner"/> implementation wrapping an array.
+    /// </summary>
+    internal readonly struct ArrayOwner : ISpanOwner
+    {
+        /// <summary>
+        /// The wrapped <see cref="byte"/> array.
+        /// </summary>
+        private readonly byte[] array;
+
+        /// <summary>
+        /// The starting offset within <see cref="array"/>.
+        /// </summary>
+        private readonly int offset;
+
+        /// <summary>
+        /// The usable length within <see cref="array"/>.
+        /// </summary>
+        private readonly int length;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="ArrayOwner"/> struct.
+        /// </summary>
+        /// <param name="array">The wrapped <see cref="byte"/> array.</param>
+        /// <param name="offset">The starting offset within <paramref name="array"/>.</param>
+        /// <param name="length">The usable length within <paramref name="array"/>.</param>
+        public ArrayOwner(byte[] array, int offset, int length)
+        {
+            this.array = array;
+            this.offset = offset;
+            this.length = length;
+        }
+
+        /// <inheritdoc/>
+        public int Length
+        {
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            get => this.length;
+        }
+
+        /// <inheritdoc/>
+        public Span<byte> Span
+        {
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            get
+            {
+#if SPAN_RUNTIME_SUPPORT
+                ref byte r0 = ref this.array.DangerousGetReferenceAt(this.offset);
+
+                return MemoryMarshal.CreateSpan(ref r0, this.length);
+#else
+                return this.array.AsSpan(this.offset, this.length);
+#endif
+            }
+        }
+    }
+}

Microsoft.Toolkit.HighPerformance/Streams/Sources/Interfaces/ISpanOwner.cs

@@ -0,0 +1,11 @@
+using System;
+
+namespace Microsoft.Toolkit.HighPerformance.Streams
+{
+    internal interface ISpanOwner
+    {
+        int Length { get; }
+
+        Span<byte> Span { get; }
+    }
+}

Microsoft.Toolkit.HighPerformance/Streams/Sources/MemoryManagerOwner.cs

@@ -0,0 +1,65 @@
+using System;
+using System.Buffers;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using Microsoft.Toolkit.HighPerformance.Extensions;
+
+namespace Microsoft.Toolkit.HighPerformance.Streams
+{
+    /// <summary>
+    /// An <see cref="ISpanOwner"/> implementation wrapping a <see cref="MemoryManager{T}"/> of <see cref="byte"/> instance.
+    /// </summary>
+    internal readonly struct MemoryManagerOwner : ISpanOwner
+    {
+        /// <summary>
+        /// The wrapped <see cref="MemoryManager{T}"/> instance.
+        /// </summary>
+        private readonly MemoryManager<byte> memoryManager;
+
+        /// <summary>
+        /// The starting offset within <see cref="memoryManager"/>.
+        /// </summary>
+        private readonly int offset;
+
+        /// <summary>
+        /// The usable length within <see cref="memoryManager"/>.
+        /// </summary>
+        private readonly int length;
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="MemoryManagerOwner"/> struct.
+        /// </summary>
+        /// <param name="memoryManager">The wrapped <see cref="MemoryManager{T}"/> instance.</param>
+        /// <param name="offset">The starting offset within <paramref name="memoryManager"/>.</param>
+        /// <param name="length">The usable length within <paramref name="memoryManager"/>.</param>
+        public MemoryManagerOwner(MemoryManager<byte> memoryManager, int offset, int length)
+        {
+            this.memoryManager = memoryManager;
+            this.offset = offset;
+            this.length = length;
+        }
+
+        /// <inheritdoc/>
+        public int Length
+        {
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            get => this.length;
+        }
+
+        /// <inheritdoc/>
+        public Span<byte> Span
+        {
+            [MethodImpl(MethodImplOptions.AggressiveInlining)]
+            get
+            {
+#if SPAN_RUNTIME_SUPPORT
+                ref byte r0 = ref this.memoryManager.GetSpan().DangerousGetReferenceAt(this.offset);
+
+                return MemoryMarshal.CreateSpan(ref r0, this.length);
+#else
+                return this.memoryManager.GetSpan();
+#endif
+            }
+        }
+    }
+}