Merge pull request #1393 from adamhathcock/adam/flat-gzip-fix-stream-rewind

Fix SeekableSharpCompressStream.StopRecording() to rewind to recorded…

src/SharpCompress/IO/SeekableSharpCompressStream.cs

@@ -83,7 +83,16 @@ internal sealed partial class SeekableSharpCompressStream : SharpCompressStream
     public override void StartRecording(int? minBufferSize = null) =>
         _recordedPosition = _stream.Position;
 
-    public override void StopRecording() => _recordedPosition = null;
+    public override void StopRecording()
+    {
+        if (_recordedPosition.HasValue)
+        {
+            // Seek back to the recording anchor position, matching the behavior of the
+            // non-seekable SharpCompressStream.StopRecording() which rewinds _logicalPosition.
+            _stream.Seek(_recordedPosition.Value, SeekOrigin.Begin);
+        }
+        _recordedPosition = null;
+    }
 
     protected override void Dispose(bool disposing)
     {

tests/SharpCompress.Test/GZip/GZipReaderAsyncTests.cs

@@ -1,4 +1,5 @@
 using System.IO;
+using System.IO.Compression;
 using System.Threading.Tasks;
 using SharpCompress.Common;
 using SharpCompress.IO;
@@ -37,4 +38,33 @@ public class GZipReaderAsyncTests : ReaderTests
             }
         }
     }
+
+    [Fact]
+    public async ValueTask GZip_ReaderFactory_FlatGZip_Async()
+    {
+        var source = new byte[2048];
+        for (var i = 0; i < source.Length; i++)
+        {
+            source[i] = 0xFF;
+        }
+
+        var gzipPath = Path.Combine(SCRATCH_FILES_PATH, "Flat.bin.gz");
+        using (var output = File.Create(gzipPath))
+        using (var gzip = new GZipStream(output, CompressionMode.Compress))
+        {
+            await gzip.WriteAsync(source, 0, source.Length);
+        }
+
+        using Stream stream = File.OpenRead(gzipPath);
+        await using var reader = await ReaderFactory.OpenAsyncReader(stream);
+        Assert.IsType<GZipReader>(reader);
+        Assert.True(await reader.MoveToNextEntryAsync());
+
+        using var ms = new MemoryStream();
+        await reader.WriteEntryToAsync(ms);
+        Assert.Equal(source.Length, ms.Length);
+        Assert.Equal(source, ms.ToArray());
+
+        Assert.False(await reader.MoveToNextEntryAsync());
+    }
 }

tests/SharpCompress.Test/GZip/GZipReaderTests.cs

@@ -48,6 +48,12 @@ public class GZipReaderTests : ReaderTests
         using var reader = ReaderFactory.OpenReader(stream);
         Assert.IsType<GZipReader>(reader);
         Assert.True(reader.MoveToNextEntry());
+
+        using var ms = new MemoryStream();
+        reader.WriteEntryTo(ms);
+        Assert.Equal(source.Length, ms.Length);
+        Assert.Equal(source, ms.ToArray());
+
         Assert.False(reader.MoveToNextEntry());
     }
 }