From 45eb0ef415049d0399435b7adeb7596ee8f9c680 Mon Sep 17 00:00:00 2001
From: Oliver Booth <me@olivr.me>
Date: Tue, 20 Jul 2021 17:18:15 +0100
Subject: [PATCH] Add IReadOnlyCollection<T>.Split(int)

Yields the same results as IEnumerable<T>.Split(int), except is able to
avoid a hidden allocation with the benefit of knowing the collection
size ahead of time
---
 .../CollectionExtensions.cs                   | 38 +++++++++++++++++++
 1 file changed, 38 insertions(+)
 create mode 100644 X10D/src/CollectionExtensions/CollectionExtensions.cs

diff --git a/X10D/src/CollectionExtensions/CollectionExtensions.cs b/X10D/src/CollectionExtensions/CollectionExtensions.cs
new file mode 100644
index 0000000..c10f765
--- /dev/null
+++ b/X10D/src/CollectionExtensions/CollectionExtensions.cs
@@ -0,0 +1,38 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace X10D
+{
+    /// <summary>
+    ///     Extension methods for <see cref="ICollection{T}" /> and <see cref="IReadOnlyCollection{T}" />.
+    /// </summary>
+    public static class CollectionExtensions
+    {
+        /// <summary>
+        ///     Splits <paramref name="value" /> into chunks of size <paramref name="chunkSize" />.
+        /// </summary>
+        /// <typeparam name="T">Any type.</typeparam>
+        /// <param name="value">The collection to split.</param>
+        /// <param name="chunkSize">The maximum length of the nested collection.</param>
+        /// <returns>
+        ///     An <see cref="IEnumerable{T}" /> containing an <see cref="IEnumerable{T}" /> of <typeparamref name="T" />
+        ///     whose lengths are no greater than <paramref name="chunkSize" />.
+        /// </returns>
+        public static IEnumerable<IReadOnlyCollection<T>> Split<T>(this IReadOnlyCollection<T> value, int chunkSize)
+        {
+            if (value is null)
+            {
+                throw new ArgumentNullException(nameof(value));
+            }
+
+            var count = value.Count;
+            chunkSize = chunkSize.Clamp(1, count);
+
+            for (var i = 0; i < count / chunkSize; i++)
+            {
+                yield return value.Skip(i * chunkSize).Take(chunkSize).ToArray();
+            }
+        }
+    }
+}