Reduce LZMA Allocations

src/SharpCompress/Common/Rar/RarCryptoWrapper.cs

@@ -63,9 +63,9 @@ public override Task<int> ReadAsync(
         int offset,
         int count,
         CancellationToken cancellationToken
-    ) => ReadAndDecryptAsync(buffer, offset, count, cancellationToken);
+    ) => ReadAndDecryptAsync(buffer, offset, count, cancellationToken).AsTask();
 
-    private async Task<int> ReadAndDecryptAsync(
+    private async ValueTask<int> ReadAndDecryptAsync(
         byte[] buffer,
         int offset,
         int count,

src/SharpCompress/Compressors/LZMA/LZ/LzBinTree.cs

@@ -1,6 +1,7 @@
 #nullable disable
 
 using System;
+using System.Buffers;
 using System.IO;
 
 namespace SharpCompress.Compressors.LZMA.LZ;
@@ -11,8 +12,8 @@ internal sealed class BinTree : InWindow
     private uint _cyclicBufferSize;
     private uint _matchMaxLen;
 
-    private uint[] _son;
-    private uint[] _hash;
+    private uint[] _son = [];
+    private uint[] _hash = [];
 
     private uint _cutValue = 0xFF;
     private uint _hashMask;
@@ -108,7 +109,12 @@ uint keepAddBufferAfter
         var cyclicBufferSize = historySize + 1;
         if (_cyclicBufferSize != cyclicBufferSize)
         {
-            _son = new uint[(_cyclicBufferSize = cyclicBufferSize) * 2];
+            if (_son.Length != 0)
+            {
+                ArrayPool<uint>.Shared.Return(_son);
+            }
+            _cyclicBufferSize = cyclicBufferSize;
+            _son = ArrayPool<uint>.Shared.Rent(checked((int)(_cyclicBufferSize * 2)));
         }
 
         var hs = K_BT2_HASH_SIZE;
@@ -132,7 +138,27 @@ uint keepAddBufferAfter
         }
         if (hs != _hashSizeSum)
         {
-            _hash = new uint[_hashSizeSum = hs];
+            if (_hash.Length != 0)
+            {
+                ArrayPool<uint>.Shared.Return(_hash);
+            }
+            _hashSizeSum = hs;
+            _hash = ArrayPool<uint>.Shared.Rent(checked((int)_hashSizeSum));
+        }
+    }
+
+    public override void Dispose()
+    {
+        base.Dispose();
+        if (_son.Length != 0)
+        {
+            ArrayPool<uint>.Shared.Return(_son);
+            _son = [];
+        }
+        if (_hash.Length != 0)
+        {
+            ArrayPool<uint>.Shared.Return(_hash);
+            _hash = [];
         }
     }
 

src/SharpCompress/Compressors/LZMA/LZ/LzInWindow.cs

@@ -1,10 +1,12 @@
 #nullable disable
 
+using System;
+using System.Buffers;
 using System.IO;
 
 namespace SharpCompress.Compressors.LZMA.LZ;
 
-internal class InWindow
+internal class InWindow : IDisposable
 {
     public byte[] _bufferBase; // pointer to buffer with data
     private Stream _stream;
@@ -78,7 +80,22 @@ public virtual void ReadBlock()
         }
     }
 
-    private void Free() => _bufferBase = null;
+    private void Free()
+    {
+        if (_bufferBase is null)
+        {
+            return;
+        }
+
+        ArrayPool<byte>.Shared.Return(_bufferBase);
+        _bufferBase = null;
+    }
+
+    public virtual void Dispose()
+    {
+        ReleaseStream();
+        Free();
+    }
 
     public void Create(uint keepSizeBefore, uint keepSizeAfter, uint keepSizeReserv)
     {
@@ -89,7 +106,7 @@ public void Create(uint keepSizeBefore, uint keepSizeAfter, uint keepSizeReserv)
         {
             Free();
             _blockSize = blockSize;
-            _bufferBase = new byte[_blockSize];
+            _bufferBase = ArrayPool<byte>.Shared.Rent(checked((int)_blockSize));
         }
         _pointerToLastSafePosition = _blockSize - keepSizeAfter;
         _streamEndWasReached = false;

src/SharpCompress/Compressors/LZMA/LZipStream.Async.cs

@@ -126,31 +126,40 @@ CancellationToken cancellationToken
     )
     {
         // Read the header
-        byte[] header = new byte[6];
-        var n = await stream
-            .ReadAsync(header, 0, header.Length, cancellationToken)
-            .ConfigureAwait(false);
+        var header = ArrayPool<byte>.Shared.Rent(6);
+        try
+        {
+            var n = await stream.ReadAsync(header, 0, 6, cancellationToken).ConfigureAwait(false);
 
-        // TODO: Handle reading only part of the header?
+            // TODO: Handle reading only part of the header?
 
-        if (n != 6)
-        {
-            return 0;
-        }
+            if (n != 6)
+            {
+                return 0;
+            }
 
-        if (
-            header[0] != 'L'
-            || header[1] != 'Z'
-            || header[2] != 'I'
-            || header[3] != 'P'
-            || header[4] != 1 /* version 1 */
-        )
+            if (
+                header[0] != 'L'
+                || header[1] != 'Z'
+                || header[2] != 'I'
+                || header[3] != 'P'
+                || header[4] != 1 /* version 1 */
+            )
+            {
+                return 0;
+            }
+            var basePower = header[5] & 0x1F;
+            var subtractionNumerator = (header[5] & 0xE0) >> 5;
+            if (basePower < 4 || basePower > 30)
+            {
+                return 0;
+            }
+            return (1 << basePower) - (subtractionNumerator * (1 << (basePower - 4)));
+        }
+        finally
         {
-            return 0;
+            ArrayPool<byte>.Shared.Return(header);
         }
-        var basePower = header[5] & 0x1F;
-        var subtractionNumerator = (header[5] & 0xE0) >> 5;
-        return (1 << basePower) - (subtractionNumerator * (1 << (basePower - 4)));
     }
 
 #if !LEGACY_DOTNET