Array pooling for InternalBitArray

benchmarks/Results.txt

@@ -9,9 +9,9 @@ Original:
 
 Revised:
 
-|   Method |        Job |       Runtime |       Mean |    Error |   StdDev |    Gen 0 |   Gen 1 | Allocated |
-|--------- |----------- |-------------- |-----------:|---------:|---------:|---------:|--------:|----------:|
-| LoadOnly | Job-TRPBVX |      .NET 6.0 |   708.2 us |  5.30 us |  4.95 us |  49.8047 | 10.7422 |    231 KB |
-| SaveOnly | Job-TRPBVX |      .NET 6.0 | 1,619.9 us | 21.20 us | 16.55 us | 312.5000 |  5.8594 |  1,438 KB |
-| LoadOnly | Job-SMJWQL | .NET Core 3.1 |   886.8 us |  6.18 us |  5.16 us |  49.8047 | 10.7422 |    231 KB |
-| SaveOnly | Job-SMJWQL | .NET Core 3.1 | 1,991.9 us | 39.51 us | 35.02 us | 312.5000 |  3.9063 |  1,438 KB |
+|   Method |        Job |       Runtime |       Mean |   Error |  StdDev |   Gen 0 |   Gen 1 | Allocated |
+|--------- |----------- |-------------- |-----------:|--------:|--------:|--------:|--------:|----------:|
+| LoadOnly | Job-MHBQCF |      .NET 6.0 |   735.6 us | 4.74 us | 4.20 us | 50.7813 | 11.7188 |    237 KB |
+| SaveOnly | Job-MHBQCF |      .NET 6.0 | 1,223.6 us | 7.57 us | 8.42 us | 44.9219 |       - |    215 KB |
+| LoadOnly | Job-OTQTAE | .NET Core 3.1 |   880.1 us | 3.63 us | 3.22 us | 50.7813 | 11.7188 |    237 KB |
+| SaveOnly | Job-OTQTAE | .NET Core 3.1 | 1,426.6 us | 8.43 us | 7.88 us | 44.9219 |       - |    215 KB |

src/IO/BitReader.cs

@@ -141,5 +141,5 @@ public string ReadString(int byteCount)
 
     public void Align() => Position = (Position + 7) & ~7;
 
-    public void Dispose() => _bits = null!;
+    public void Dispose() => Interlocked.Exchange(ref _bits!, null)?.Dispose();
 }

src/IO/BitWriter.cs

@@ -76,13 +76,13 @@ public void WriteBits(IList<bool> bits, int numberOfBits)
 
     public void WriteBytes(ReadOnlySpan<byte> value)
     {
-        var bits = new InternalBitArray(value);
+        using var bits = new InternalBitArray(value);
         WriteBits(bits);
     }
 
     public void WriteBytes(ReadOnlySpan<byte> value, int numberOfBits)
     {
-        var bits = new InternalBitArray(value) { Length = numberOfBits };
+        using var bits = new InternalBitArray(value) { Length = numberOfBits };
         WriteBits(bits, numberOfBits);
     }
 
@@ -174,5 +174,5 @@ private void InternalGetBytes(Span<byte> output)
     public void SeekBits(int bitPosition) => Position = bitPosition;
     public void Seek(int bytePostion) => SeekBits(bytePostion * 8);
     public void Align() => Position = (Position + 7) & ~7;
-    public void Dispose() => _bits = null!;
+    public void Dispose() => Interlocked.Exchange(ref _bits!, null)?.Dispose();
 }

src/IO/InternalBitArray.cs

@@ -4,6 +4,8 @@
 // Adapted from here, to allow for span-based constructor. Removed unused/unsafe code.
 // https://github.com/dotnet/runtime/blob/main/src/libraries/System.Collections/src/System/Collections/BitArray.cs
 
+using Microsoft.Toolkit.HighPerformance;
+using System.Buffers;
 using System.Buffers.Binary;
 using System.Collections;
 using System.Diagnostics;
@@ -13,7 +15,7 @@ namespace D2SLib.IO;
 
 // A vector of bits.  Use this to store bits efficiently
 [Serializable]
-internal sealed class InternalBitArray : IList<bool>, ICloneable
+internal sealed class InternalBitArray : IList<bool>, ICloneable, IDisposable
 {
     private int[] m_array; // Do not rename (binary serialization)
     private int m_length; // Do not rename (binary serialization)
@@ -45,18 +47,20 @@ public InternalBitArray(int length, bool defaultValue)
             throw new ArgumentOutOfRangeException(nameof(length), length, "Length must be non-negative");
         }
 
-        m_array = new int[GetInt32ArrayLengthFromBitLength(length)];
+        int arrayLength = GetInt32ArrayLengthFromBitLength(length);
+        m_array = ArrayPool<int>.Shared.Rent(arrayLength);
         m_length = length;
 
         if (defaultValue)
         {
-            Array.Fill(m_array, -1);
+            var span = m_array.AsSpan(0, arrayLength);
+            span.Fill(-1);
 
             // clear high bit values in the last int
             Div32Rem(length, out int extraBits);
             if (extraBits > 0)
             {
-                m_array[^1] = (1 << extraBits) - 1;
+                span[^1] = (1 << extraBits) - 1;
             }
         }
 
@@ -81,7 +85,7 @@ public InternalBitArray(ReadOnlySpan<byte> bytes)
             throw new ArgumentException("Too many bytes!", nameof(bytes));
         }
 
-        m_array = new int[GetInt32ArrayLengthFromByteLength(bytes.Length)];
+        m_array = ArrayPool<int>.Shared.Rent(GetInt32ArrayLengthFromByteLength(bytes.Length));
         m_length = bytes.Length * BitsPerByte;
 
         uint totalCount = (uint)bytes.Length / 4;
@@ -127,7 +131,7 @@ public InternalBitArray(InternalBitArray bits)
 
         int arrayLength = GetInt32ArrayLengthFromBitLength(bits.m_length);
 
-        m_array = new int[arrayLength];
+        m_array = ArrayPool<int>.Shared.Rent(arrayLength);
 
         Debug.Assert(bits.m_array.Length <= arrayLength);
 
@@ -237,7 +241,7 @@ public int Length
             if (newints > m_array.Length || newints + _ShrinkThreshold < m_array.Length)
             {
                 // grow or shrink (if wasting more than _ShrinkThreshold ints)
-                Array.Resize(ref m_array, newints);
+                ArrayPool<int>.Shared.Resize(ref m_array!, newints);
             }
 
             if (value > m_length)
@@ -333,6 +337,16 @@ private static int Div32Rem(int number, out int remainder)
     void ICollection<bool>.CopyTo(bool[] array, int arrayIndex) => throw new NotImplementedException();
     bool ICollection<bool>.Remove(bool item) => throw new NotImplementedException();
 
+    public void Dispose()
+    {
+        if (m_array.Length > 0)
+        {
+            ArrayPool<int>.Shared.Return(m_array);
+            m_array = Array.Empty<int>();
+            m_length = 0;
+        }
+    }
+
     private sealed class BitArrayEnumeratorSimple : IEnumerator<bool>, ICloneable
     {
         private readonly InternalBitArray _bitArray;

src/Model/Data/ItemsData.cs

@@ -17,7 +17,7 @@ public ItemsData(ArmorData armorData, WeaponsData weaponsData, MiscData miscData
     public MiscData MiscData { get; }
 
     private HuffmanTree? _itemCodeTree = null;
-    public HuffmanTree ItemCodeTree
+    internal HuffmanTree ItemCodeTree
     {
         get => _itemCodeTree ??= InitializeHuffmanTree();
         set => _itemCodeTree = value;

src/Model/Huffman/HuffmanTree.cs

@@ -1,10 +1,9 @@
 using D2SLib.IO;
-using System.Collections;
 
 namespace D2SLib.Model.Huffman;
 
 //hardcoded....
-public class HuffmanTree
+internal class HuffmanTree
 {
     public Node? Root { get; set; }
 
@@ -79,7 +78,7 @@ public void Build()
         }
     }
 
-    public IEnumerable<bool> EncodeChar(char source)
+    public InternalBitArray EncodeChar(char source)
     {
         var encodedSymbol = Root?.Traverse(source, new InternalBitArray(0));
         if (encodedSymbol is null)

src/Model/Huffman/Node.cs

@@ -2,7 +2,7 @@
 
 namespace D2SLib.Model.Huffman;
 
-public class Node
+internal class Node
 {
     public char Symbol { get; set; }
     public int Frequency { get; set; }
@@ -17,7 +17,6 @@ public class Node
         }
         else
         {
-
             if (Left is not null)
             {
                 data.Add(false);

src/Model/Save/Corpses.cs

@@ -2,7 +2,7 @@
 
 namespace D2SLib.Model.Save;
 
-public sealed class CorpseList
+public sealed class CorpseList : IDisposable
 {
     public CorpseList(ushort? header, ushort count)
     {
@@ -45,9 +45,18 @@ public static byte[] Write(CorpseList corpseList, uint version)
         corpseList.Write(writer, version);
         return writer.ToArray();
     }
+
+    public void Dispose()
+    {
+        foreach (var corpse in Corpses)
+        {
+            corpse?.Dispose();
+        }
+        Corpses.Clear();
+    }
 }
 
-public sealed class Corpse
+public sealed class Corpse : IDisposable
 {
     private Corpse(IBitReader reader, uint version)
     {
@@ -60,7 +69,7 @@ private Corpse(IBitReader reader, uint version)
     public uint? Unk0x0 { get; set; }
     public uint X { get; set; }
     public uint Y { get; set; }
-    public ItemList ItemList { get; set; }
+    public ItemList ItemList { get; }
 
     public void Write(IBitWriter writer, uint version)
     {
@@ -83,5 +92,7 @@ public static byte[] Write(Corpse corpse, uint version)
         corpse.Write(writer, version);
         return writer.ToArray();
     }
+
+    public void Dispose() => ItemList.Dispose();
 }
 

src/Model/Save/D2I.cs

@@ -2,7 +2,7 @@
 
 namespace D2SLib.Model.Save;
 
-public class D2I
+public sealed class D2I : IDisposable
 {
     private D2I(IBitReader reader, uint version)
     {
@@ -31,4 +31,5 @@ public static byte[] Write(D2I d2i, uint version)
         return writer.ToArray();
     }
 
+    public void Dispose() => ItemList?.Dispose();
 }

src/Model/Save/D2S.cs

@@ -5,7 +5,7 @@
 
 namespace D2SLib.Model.Save;
 
-public class D2S
+public sealed class D2S : IDisposable
 {
     private D2S(IBitReader reader)
     {
@@ -188,4 +188,14 @@ public static byte[] Write(D2S d2s)
         Header.Fix(bytes);
         return bytes;
     }
+
+    public void Dispose()
+    {
+        Waypoints.Dispose();
+        Status.Dispose();
+        Quests.Dispose();
+        PlayerItemList.Dispose();
+        PlayerCorpses.Dispose();
+        MercenaryItemList?.Dispose();
+    }
 }