From 4a1f2c1ffb541da5bdc4f0130c26829919efb72a Mon Sep 17 00:00:00 2001
From: mlemanczyk <marek@lemanczyk.eu>
Date: Wed, 22 Mar 2023 00:00:41 +0100
Subject: [PATCH] Added rented array clearing if T is a reference type, as
 discussed in https://github.com/dotnet/runtime/issues/25378.

---
 Recyclable.Collections/RecyclableArrayList.cs   |  6 ++++--
 Recyclable.Collections/RecyclableList.cs        | 17 ++++++++++-------
 .../RecyclableListExtensions.cs                 |  4 ++--
 3 files changed, 16 insertions(+), 11 deletions(-)

diff --git a/Recyclable.Collections/RecyclableArrayList.cs b/Recyclable.Collections/RecyclableArrayList.cs
index d63bc23..561ac61 100644
--- a/Recyclable.Collections/RecyclableArrayList.cs
+++ b/Recyclable.Collections/RecyclableArrayList.cs
@@ -9,6 +9,8 @@ namespace Recyclable.Collections
 		private static readonly ArrayPool<T> _arrayPool = ArrayPool<T>.Create();
 		private static readonly IEqualityComparer<T> _equalityComparer = EqualityComparer<T>.Default;
 
+		protected static readonly bool NeedsClearing = !typeof(T).IsValueType;
+
 		protected T[] _memoryBlock;
 
 		private static void ThrowArgumentOutOfRangeException(in string message)
@@ -32,7 +34,7 @@ namespace Recyclable.Collections
 				sourceSpan.CopyTo(newArraySpan);
 				if (sourceLength >= RecyclableDefaults.MinPooledArrayLength)
 				{
-					arrayPool.Return(source!);
+					arrayPool.Return(source!, NeedsClearing);
 				}
 			}
 
@@ -464,7 +466,7 @@ namespace Recyclable.Collections
 			{
 				Clear();
 				_capacity = 0;
-				_memoryBlock.ReturnToPool(_arrayPool);
+				_memoryBlock.ReturnToPool(_arrayPool, NeedsClearing);
 				GC.SuppressFinalize(this);
 			}
 		}
diff --git a/Recyclable.Collections/RecyclableList.cs b/Recyclable.Collections/RecyclableList.cs
index aac2350..08cd2ef 100644
--- a/Recyclable.Collections/RecyclableList.cs
+++ b/Recyclable.Collections/RecyclableList.cs
@@ -5,7 +5,7 @@ using System.Runtime.CompilerServices;
 namespace Recyclable.Collections
 {
 	public class RecyclableList<T> : IDisposable, IList<T>
-	{
+	{		
 		private const int ItemNotFoundIndex = -1;
 		private const int BatchSize = 8;
 
@@ -18,6 +18,9 @@ namespace Recyclable.Collections
 		private int _blockSize;
 		private int _lastBlockIndex;
 		private int _nextItemIndex;
+
+		protected static readonly bool NeedsClearing = !typeof(T).IsValueType;
+
 		protected ArrayPool<T[]> _memoryBlocksPool;
 		protected ArrayPool<T> _blockArrayPool;
 		protected T[][] _memoryBlocks;
@@ -70,7 +73,7 @@ namespace Recyclable.Collections
 				T[][] memoryBlocks = list._memoryBlocks;
 				if (blockSize >= RecyclableDefaults.MinPooledArrayLength)
 				{
-					blockArrayPool.Return(memoryBlocks[list.ReservedBlockCount - 1]);
+					blockArrayPool.Return(memoryBlocks[list.ReservedBlockCount - 1], NeedsClearing);
 				}
 
 				list._capacity -= blockSize;
@@ -247,7 +250,7 @@ namespace Recyclable.Collections
 				sourceSpan.CopyTo(newMemoryBlocksSpan);
 				if (localInts[sourceBlockCount] >= RecyclableDefaults.MinPooledArrayLength)
 				{
-					memoryBlocksPool.Return(source!);
+					memoryBlocksPool.Return(source!, NeedsClearing);
 				}
 
 				newMemoryBlocksSpan = newMemoryBlocksSpan[localInts[sourceBlockCount]..];
@@ -648,7 +651,7 @@ namespace Recyclable.Collections
 			{
 				if (items.Count >= RecyclableDefaults.MinPooledArrayLength)
 				{
-					_blockArrayPool.Return(itemsBuffer);
+					_blockArrayPool.Return(itemsBuffer, NeedsClearing);
 				}
 			}
 		}
@@ -703,7 +706,7 @@ namespace Recyclable.Collections
 				ArrayPool<T> blockArrayPool = _blockArrayPool;
 				for (int toRemoveIdx = 0; toRemoveIdx < memoryBlocksCount; toRemoveIdx++)
 				{
-					blockArrayPool.Return(memoryBlocksSpan[toRemoveIdx]);
+					blockArrayPool.Return(memoryBlocksSpan[toRemoveIdx], NeedsClearing);
 				}
 			}
 
@@ -777,7 +780,7 @@ namespace Recyclable.Collections
 			}
 			else
 			{
-				_blockArrayPool.Return(_memoryBlocks[index]);
+				_blockArrayPool.Return(_memoryBlocks[index], NeedsClearing);
 			}
 
 			_capacity -= _blockSize;
@@ -810,7 +813,7 @@ namespace Recyclable.Collections
 				Clear();
 				if (_memoryBlocks.Length >= RecyclableDefaults.MinPooledArrayLength)
 				{
-					_memoryBlocksPool.Return(_memoryBlocks);
+					_memoryBlocksPool.Return(_memoryBlocks, NeedsClearing);
 				}
 
 				GC.SuppressFinalize(this);
diff --git a/Recyclable.Collections/RecyclableListExtensions.cs b/Recyclable.Collections/RecyclableListExtensions.cs
index 4b51d43..f976537 100644
--- a/Recyclable.Collections/RecyclableListExtensions.cs
+++ b/Recyclable.Collections/RecyclableListExtensions.cs
@@ -155,11 +155,11 @@ namespace Recyclable.Collections
 			: new T[minSize];
 
 		[MethodImpl(MethodImplOptions.AggressiveInlining)]
-		public static void ReturnToPool<T>(this T[] array, ArrayPool<T> arrayPool)
+		public static void ReturnToPool<T>(this T[] array, ArrayPool<T> arrayPool, bool needsClearing)
 		{
 			if (array.LongLength is > _minPooledArraySize and <= int.MaxValue)
 			{
-				arrayPool.Return(array);
+				arrayPool.Return(array, needsClearing);
 			}
 		}