Add ImmutableArrayExtensions class

- Implement AsView methods to create ArrayView<T> over immutable arrays.

Author: rameel

Ramstack.Structures/Collections/ImmutableArrayExtensions.cs

@@ -0,0 +1,43 @@
+using System.Collections.Immutable;
+using System.Runtime.InteropServices;
+
+namespace Ramstack.Collections;
+
+/// <summary>
+/// Provides extension methods for the <see cref="ImmutableArray{T}"/> structure.
+/// </summary>
+public static class ImmutableArrayExtensions
+{
+    /// <summary>
+    /// Creates an <see cref="ArrayView{T}"/> over an immutable array.
+    /// </summary>
+    /// <param name="value">The immutable array to wrap.</param>
+    /// <returns>
+    /// The read-only view of the array.
+    /// </returns>
+    public static ArrayView<T> AsView<T>(this ImmutableArray<T> value) =>
+        ImmutableCollectionsMarshal.AsArray(value).AsView();
+
+    /// <summary>
+    /// Creates an <see cref="ArrayView{T}"/> over an immutable array starting at a specified position to the end of the array.
+    /// </summary>
+    /// <param name="value">The immutable array to wrap.</param>
+    /// <param name="index">The index at which to begin the array view.</param>
+    /// <returns>
+    /// The read-only view of the array.
+    /// </returns>
+    public static ArrayView<T> AsView<T>(this ImmutableArray<T> value, int index) =>
+        ImmutableCollectionsMarshal.AsArray(value).AsView(index);
+
+    /// <summary>
+    /// Creates an <see cref="ArrayView{T}"/> over an immutable array starting at a specified position for a specified length.
+    /// </summary>
+    /// <param name="value">The immutable array to wrap.</param>
+    /// <param name="index">The index at which to begin the array view.</param>
+    /// <param name="count">The number of items in the array view.</param>
+    /// <returns>
+    /// The read-only view of the array.
+    /// </returns>
+    public static ArrayView<T> AsView<T>(this ImmutableArray<T> value, int index, int count) =>
+        ImmutableCollectionsMarshal.AsArray(value).AsView(index, count);
+}