Add Array.AsReadOnly and Array.Clear

Tests were added, implementation was missing

X10D/src/ArrayExtensions/ArrayExtensions.cs

@@ -0,0 +1,89 @@
+namespace X10D;
+
+/// <summary>
+///     Extension methods for <see cref="Array" />.
+/// </summary>
+public static class ArrayExtensions
+{
+    /// <summary>
+    ///     Returns a read-only wrapper for the array.
+    /// </summary>
+    /// <param name="array">The one-dimensional, zero-based array to wrap in a read-only wrapper.</param>
+    /// <typeparam name="T">The type of the elements in the array.</typeparam>
+    /// <returns>A <see cref="IReadOnlyCollection{T}" /> wrapper for the specified array.</returns>
+    /// <exception cref="ArgumentNullException"><paramref name="array" /> is <see langword="null" />.</exception>
+    public static IReadOnlyCollection<T> AsReadOnly<T>(this T[] array)
+    {
+        if (array is null)
+        {
+            throw new ArgumentNullException(nameof(array));
+        }
+
+        return Array.AsReadOnly(array);
+    }
+
+    /// <summary>
+    ///     Clears the contents of an array.
+    /// </summary>
+    /// <param name="array">The array to clear.</param>
+    /// <typeparam name="T">The type of the elements in the array.</typeparam>
+    /// <exception cref="ArgumentNullException"><paramref name="array" /> is <see langword="null" />.</exception>
+    public static void Clear<T>(this T?[] array)
+    {
+        array.Clear(..);
+    }
+
+    /// <summary>
+    ///     Sets a range of elements in an array to the default value of each element type.
+    /// </summary>
+    /// <param name="array">The array whose elements need to be cleared.</param>
+    /// <param name="range">A range defining the start index and number of elements to clear.</param>
+    /// <typeparam name="T">The type of the elements in the array.</typeparam>
+    /// <exception cref="ArgumentNullException"><paramref name="array" /> is <see langword="null" />.</exception>
+    public static void Clear<T>(this T?[] array, Range range)
+    {
+        if (array is null)
+        {
+            throw new ArgumentNullException(nameof(array));
+        }
+
+        int index = range.Start.Value;
+        int end = range.End.Value;
+        if (range.End.IsFromEnd)
+        {
+            end = array.Length - end;
+        }
+        
+        array.Clear(index, end - index);
+    }
+
+    /// <summary>
+    ///     Sets a range of elements in an array to the default value of each element type.
+    /// </summary>
+    /// <param name="array">The array whose elements need to be cleared.</param>
+    /// <param name="index">The starting index of the range of elements to clear.</param>
+    /// <param name="length">The number of elements to clear.</param>
+    /// <typeparam name="T">The type of the elements in the array.</typeparam>
+    /// <exception cref="ArgumentNullException"><paramref name="array" /> is <see langword="null" />.</exception>
+    /// <exception cref="ArgumentOutOfRangeException">
+    ///     <para><paramref name="index" /> is less than the lower bound of <paramref name="array" />.</para>
+    ///     -or-
+    ///     <para><paramref name="length" /> is less zero.</para>
+    ///     -or-
+    ///     <para>The sum of <paramref name="index" /> and <paramref name="length"/> is greater than the size of array.</para>
+    /// </exception>
+    public static void Clear<T>(this T?[] array, int index, int length)
+    {
+        if (array is null)
+        {
+            throw new ArgumentNullException(nameof(array));
+        }
+
+        if (length == 0 || array.Length == 0)
+        {
+            return;
+        }
+
+        Array.Clear(array, index, length);
+    }
+}