From 16903bdecbe1fa11e991e0919860bdeb4209c62a Mon Sep 17 00:00:00 2001
From: Adam Hathcock <adam@hathcock.uk>
Date: Thu, 2 Apr 2026 11:48:01 +0100
Subject: [PATCH] clean up shrink stream to ensure correctness

---
 .../Compressors/Shrink/ShrinkStream.Async.cs  | 24 +++------------
 .../Compressors/Shrink/ShrinkStream.cs        | 30 ++++++-------------
 .../Default/ShrinkCompressionProvider.cs      |  7 +----
 3 files changed, 14 insertions(+), 47 deletions(-)

diff --git a/src/SharpCompress/Compressors/Shrink/ShrinkStream.Async.cs b/src/SharpCompress/Compressors/Shrink/ShrinkStream.Async.cs
index ac296434..57342ebe 100644
--- a/src/SharpCompress/Compressors/Shrink/ShrinkStream.Async.cs
+++ b/src/SharpCompress/Compressors/Shrink/ShrinkStream.Async.cs
@@ -2,7 +2,6 @@ using System;
 using System.IO;
 using System.Threading;
 using System.Threading.Tasks;
-using SharpCompress.Common;
 
 namespace SharpCompress.Compressors.Shrink;
 
@@ -16,12 +15,7 @@ internal partial class ShrinkStream : Stream
         CancellationToken cancellationToken = default
     )
     {
-        var shrinkStream = new ShrinkStream(
-            stream,
-            compressionMode,
-            compressedSize,
-            uncompressedSize
-        );
+        var shrinkStream = new ShrinkStream(stream, uncompressedSize);
         await shrinkStream.DecompressAsync(cancellationToken).ConfigureAwait(false);
         return shrinkStream;
     }
@@ -33,26 +27,16 @@ internal partial class ShrinkStream : Stream
             return;
         }
 
-        // Read actual compressed data from stream rather than pre-allocating based on the
+        // Read actual compressed data from the stream rather than pre-allocating based on the
         // declared compressed size, which may be crafted to cause an OutOfMemoryException.
         // The stream is already bounded by ReadOnlySubStream in ZipFilePart.
         using var srcMs = new MemoryStream();
-        await inStream.CopyToAsync(srcMs, 81920, cancellationToken).ConfigureAwait(false);
+        await _inStream.CopyToAsync(srcMs, 81920, cancellationToken).ConfigureAwait(false);
         var src = srcMs.ToArray();
         var srcLen = src.Length;
 
         // Decompress synchronously (CPU-bound operation)
-        var srcUsed = 0;
-        var dstUsed = 0;
-
-        HwUnshrink.Unshrink(
-            src,
-            srcLen,
-            out srcUsed,
-            _byteOut,
-            (int)_uncompressedSize,
-            out dstUsed
-        );
+        HwUnshrink.Unshrink(src, srcLen, out _, _byteOut, (int)_uncompressedSize, out var dstUsed);
         _outBytesCount = dstUsed;
         _decompressed = true;
     }
diff --git a/src/SharpCompress/Compressors/Shrink/ShrinkStream.cs b/src/SharpCompress/Compressors/Shrink/ShrinkStream.cs
index a7055e93..b7831f45 100644
--- a/src/SharpCompress/Compressors/Shrink/ShrinkStream.cs
+++ b/src/SharpCompress/Compressors/Shrink/ShrinkStream.cs
@@ -5,33 +5,23 @@ namespace SharpCompress.Compressors.Shrink;
 
 internal partial class ShrinkStream : Stream
 {
-    private Stream inStream;
+    private readonly Stream _inStream;
 
-    private long _uncompressedSize;
-    private byte[] _byteOut;
+    private readonly long _uncompressedSize;
+    private readonly byte[] _byteOut;
     private long _outBytesCount;
     private bool _decompressed;
     private long _position;
 
-    public ShrinkStream(
-        Stream stream,
-        CompressionMode compressionMode,
-        long compressedSize,
-        long uncompressedSize
-    )
+    public ShrinkStream(Stream stream, long uncompressedSize)
     {
-        inStream = stream;
+        _inStream = stream;
 
         _uncompressedSize = uncompressedSize;
         _byteOut = new byte[_uncompressedSize];
         _outBytesCount = 0L;
     }
 
-    protected override void Dispose(bool disposing)
-    {
-        base.Dispose(disposing);
-    }
-
     public override bool CanRead => true;
 
     public override bool CanSeek => true;
@@ -52,23 +42,21 @@ internal partial class ShrinkStream : Stream
     {
         if (!_decompressed)
         {
-            // Read actual compressed data from stream rather than pre-allocating based on the
+            // Read actual compressed data from the stream rather than pre-allocating based on the
             // declared compressed size, which may be crafted to cause an OutOfMemoryException.
             // The stream is already bounded by ReadOnlySubStream in ZipFilePart.
             using var srcMs = new MemoryStream();
-            inStream.CopyTo(srcMs);
+            _inStream.CopyTo(srcMs);
             var src = srcMs.ToArray();
             var srcLen = src.Length;
-            var srcUsed = 0;
-            var dstUsed = 0;
 
             HwUnshrink.Unshrink(
                 src,
                 srcLen,
-                out srcUsed,
+                out _,
                 _byteOut,
                 (int)_uncompressedSize,
-                out dstUsed
+                out var dstUsed
             );
             _outBytesCount = dstUsed;
             _decompressed = true;
diff --git a/src/SharpCompress/Providers/Default/ShrinkCompressionProvider.cs b/src/SharpCompress/Providers/Default/ShrinkCompressionProvider.cs
index 2e26c7a7..95d0746a 100644
--- a/src/SharpCompress/Providers/Default/ShrinkCompressionProvider.cs
+++ b/src/SharpCompress/Providers/Default/ShrinkCompressionProvider.cs
@@ -27,12 +27,7 @@ public sealed class ShrinkCompressionProvider : ContextRequiredDecompressionProv
     {
         ValidateRequiredSizes(context, "Shrink");
 
-        return new ShrinkStream(
-            source,
-            CompressionMode.Decompress,
-            context.InputSize,
-            context.OutputSize
-        );
+        return new ShrinkStream(source, context.OutputSize);
     }
 
     public override async ValueTask<Stream> CreateDecompressStreamAsync(