From ee98b5565b0df3d91ed972bdb02358388f64d685 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Fri, 13 Feb 2026 15:49:14 +0000
Subject: [PATCH] Fix XZStream to support non-seekable streams

Co-authored-by: adamhathcock <527620+adamhathcock@users.noreply.github.com>
---
 src/SharpCompress/Compressors/Xz/XZStream.cs  | 17 +++++++++++++--
 src/SharpCompress/packages.lock.json          | 12 +++++------
 .../Xz/XZStreamAsyncTests.cs                  | 20 ++++++++++++++++++
 tests/SharpCompress.Test/Xz/XZStreamTests.cs  | 21 +++++++++++++++++++
 4 files changed, 62 insertions(+), 8 deletions(-)

diff --git a/src/SharpCompress/Compressors/Xz/XZStream.cs b/src/SharpCompress/Compressors/Xz/XZStream.cs
index 489b449a..dff04464 100644
--- a/src/SharpCompress/Compressors/Xz/XZStream.cs
+++ b/src/SharpCompress/Compressors/Xz/XZStream.cs
@@ -5,6 +5,7 @@ using System.IO;
 using System.Threading;
 using System.Threading.Tasks;
 using SharpCompress.Common;
+using SharpCompress.IO;
 
 namespace SharpCompress.Compressors.Xz;
 
@@ -12,9 +13,21 @@ namespace SharpCompress.Compressors.Xz;
 public sealed partial class XZStream : XZReadOnlyStream
 {
     public XZStream(Stream baseStream)
-        : base(baseStream)
+        : base(WrapIfNeeded(baseStream))
     {
-        _baseStream = baseStream;
+        _baseStream = BaseStream;
+    }
+
+    private static Stream WrapIfNeeded(Stream stream)
+    {
+        // XZ format requires position tracking for padding calculations.
+        // For non-seekable streams, wrap with SharpCompressStream which provides
+        // limited backward seeking via a ring buffer.
+        if (!stream.CanSeek)
+        {
+            return SharpCompressStream.Create(stream);
+        }
+        return stream;
     }
 
     protected override void Dispose(bool disposing)
diff --git a/src/SharpCompress/packages.lock.json b/src/SharpCompress/packages.lock.json
index 29e7a1bd..27e9e496 100644
--- a/src/SharpCompress/packages.lock.json
+++ b/src/SharpCompress/packages.lock.json
@@ -216,9 +216,9 @@
     "net10.0": {
       "Microsoft.NET.ILLink.Tasks": {
         "type": "Direct",
-        "requested": "[10.0.0, )",
-        "resolved": "10.0.0",
-        "contentHash": "kICGrGYEzCNI3wPzfEXcwNHgTvlvVn9yJDhSdRK+oZQy4jvYH529u7O0xf5ocQKzOMjfS07+3z9PKRIjrFMJDA=="
+        "requested": "[10.0.2, )",
+        "resolved": "10.0.2",
+        "contentHash": "sXdDtMf2qcnbygw9OdE535c2lxSxrZP8gO4UhDJ0xiJbl1wIqXS1OTcTDFTIJPOFd6Mhcm8gPEthqWGUxBsTqw=="
       },
       "Microsoft.NETFramework.ReferenceAssemblies": {
         "type": "Direct",
@@ -264,9 +264,9 @@
     "net8.0": {
       "Microsoft.NET.ILLink.Tasks": {
         "type": "Direct",
-        "requested": "[8.0.22, )",
-        "resolved": "8.0.22",
-        "contentHash": "MhcMithKEiyyNkD2ZfbDZPmcOdi0GheGfg8saEIIEfD/fol3iHmcV8TsZkD4ZYz5gdUuoX4YtlVySUU7Sxl9SQ=="
+        "requested": "[8.0.23, )",
+        "resolved": "8.0.23",
+        "contentHash": "GqHiB1HbbODWPbY/lc5xLQH8siEEhNA0ptpJCC6X6adtAYNEzu5ZlqV3YHA3Gh7fuEwgA8XqVwMtH2KNtuQM1Q=="
       },
       "Microsoft.NETFramework.ReferenceAssemblies": {
         "type": "Direct",
diff --git a/tests/SharpCompress.Test/Xz/XZStreamAsyncTests.cs b/tests/SharpCompress.Test/Xz/XZStreamAsyncTests.cs
index a2276602..96074f64 100644
--- a/tests/SharpCompress.Test/Xz/XZStreamAsyncTests.cs
+++ b/tests/SharpCompress.Test/Xz/XZStreamAsyncTests.cs
@@ -34,4 +34,24 @@ public class XzStreamAsyncTests : XzTestsBase
         var uncompressed = await sr.ReadToEndAsync().ConfigureAwait(false);
         Assert.Equal(OriginalIndexed, uncompressed);
     }
+
+    [Fact]
+    public async ValueTask CanReadNonSeekableStreamAsync()
+    {
+        var nonSeekable = new ForwardOnlyStream(new MemoryStream(Compressed));
+        var xz = new XZStream(nonSeekable);
+        using var sr = new StreamReader(new AsyncOnlyStream(xz));
+        var uncompressed = await sr.ReadToEndAsync().ConfigureAwait(false);
+        Assert.Equal(Original, uncompressed);
+    }
+
+    [Fact]
+    public async ValueTask CanReadNonSeekableEmptyStreamAsync()
+    {
+        var nonSeekable = new ForwardOnlyStream(new MemoryStream(CompressedEmpty));
+        var xz = new XZStream(nonSeekable);
+        using var sr = new StreamReader(new AsyncOnlyStream(xz));
+        var uncompressed = await sr.ReadToEndAsync().ConfigureAwait(false);
+        Assert.Equal(OriginalEmpty, uncompressed);
+    }
 }
diff --git a/tests/SharpCompress.Test/Xz/XZStreamTests.cs b/tests/SharpCompress.Test/Xz/XZStreamTests.cs
index 02c5020c..8b175a8c 100644
--- a/tests/SharpCompress.Test/Xz/XZStreamTests.cs
+++ b/tests/SharpCompress.Test/Xz/XZStreamTests.cs
@@ -1,5 +1,6 @@
 using System.IO;
 using SharpCompress.Compressors.Xz;
+using SharpCompress.Test.Mocks;
 using Xunit;
 
 namespace SharpCompress.Test.Xz;
@@ -32,4 +33,24 @@ public class XzStreamTests : XzTestsBase
         var uncompressed = sr.ReadToEnd();
         Assert.Equal(OriginalIndexed, uncompressed);
     }
+
+    [Fact]
+    public void CanReadNonSeekableStream()
+    {
+        var nonSeekable = new ForwardOnlyStream(new MemoryStream(Compressed));
+        var xz = new XZStream(nonSeekable);
+        using var sr = new StreamReader(xz);
+        var uncompressed = sr.ReadToEnd();
+        Assert.Equal(Original, uncompressed);
+    }
+
+    [Fact]
+    public void CanReadNonSeekableEmptyStream()
+    {
+        var nonSeekable = new ForwardOnlyStream(new MemoryStream(CompressedEmpty));
+        var xz = new XZStream(nonSeekable);
+        using var sr = new StreamReader(xz);
+        var uncompressed = sr.ReadToEnd();
+        Assert.Equal(OriginalEmpty, uncompressed);
+    }
 }