From e5ef31bdaf494fbe042c102543c878eac4c7c16f Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Mon, 23 Feb 2026 21:11:00 +0000
Subject: [PATCH] Fix XZBlock exception when accessing Position on non-seekable
 streams

XZBlock accesses stream.Position in its constructor and SkipPadding(),
which throws NotSupportedException for non-seekable streams (e.g., HTTP).

Fix: XZStream now auto-wraps non-seekable streams with
SharpCompressStream.Create() to provide position tracking via ring buffer.

Add tests for raw non-seekable streams (sync and async).

Co-authored-by: adamhathcock <527620+adamhathcock@users.noreply.github.com>
---
 src/SharpCompress/Compressors/Xz/XZStream.cs  |  3 ++-
 .../Xz/XZStreamAsyncTests.cs                  | 20 +++++++++++++++++++
 tests/SharpCompress.Test/Xz/XZStreamTests.cs  | 20 +++++++++++++++++++
 3 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/src/SharpCompress/Compressors/Xz/XZStream.cs b/src/SharpCompress/Compressors/Xz/XZStream.cs
index ea193431..e4910993 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;
 
@@ -12,7 +13,7 @@ namespace SharpCompress.Compressors.Xz;
 public sealed partial class XZStream : XZReadOnlyStream
 {
     public XZStream(Stream baseStream)
-        : base(baseStream) { }
+        : base(baseStream.CanSeek ? baseStream : SharpCompressStream.Create(baseStream)) { }
 
     protected override void Dispose(bool disposing)
     {
diff --git a/tests/SharpCompress.Test/Xz/XZStreamAsyncTests.cs b/tests/SharpCompress.Test/Xz/XZStreamAsyncTests.cs
index 8f8e59b8..0da96e49 100644
--- a/tests/SharpCompress.Test/Xz/XZStreamAsyncTests.cs
+++ b/tests/SharpCompress.Test/Xz/XZStreamAsyncTests.cs
@@ -55,4 +55,24 @@ public class XzStreamAsyncTests : XzTestsBase
         var uncompressed = await sr.ReadToEndAsync().ConfigureAwait(false);
         Assert.Equal(OriginalEmpty, uncompressed);
     }
+
+    [Fact]
+    public async ValueTask CanReadRawNonSeekableStreamAsync()
+    {
+        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 CanReadRawNonSeekableEmptyStreamAsync()
+    {
+        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 80ad5dc3..75e6c189 100644
--- a/tests/SharpCompress.Test/Xz/XZStreamTests.cs
+++ b/tests/SharpCompress.Test/Xz/XZStreamTests.cs
@@ -54,4 +54,24 @@ public class XzStreamTests : XzTestsBase
         var uncompressed = sr.ReadToEnd();
         Assert.Equal(OriginalEmpty, uncompressed);
     }
+
+    [Fact]
+    public void CanReadRawNonSeekableStream()
+    {
+        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 CanReadRawNonSeekableEmptyStream()
+    {
+        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);
+    }
 }