Fix async LZMA extraction bug for 7Zip archives

AGENTS.md

@@ -28,11 +28,13 @@ SharpCompress is a pure C# compression library supporting multiple archive forma
 
 ## Code Formatting
 
+**Copilot agents: You MUST run the `format` task after making code changes to ensure consistency.**
+
 - Use CSharpier for code formatting to ensure consistent style across the project
 - CSharpier is configured as a local tool in `.config/dotnet-tools.json`
+- **To format code, run the task: `format` task (which runs `dotnet csharpier .` from project root)**
 - Restore tools with: `dotnet tool restore`
 - Format files from the project root with: `dotnet csharpier .`
-- **Run `dotnet csharpier .` from the project root after making code changes before committing**
 - Configure your IDE to format on save using CSharpier for the best experience
 - The project also uses `.editorconfig` for editor settings (indentation, encoding, etc.)
 - Let CSharpier handle code style while `.editorconfig` handles editor behavior

FORMATS.md

@@ -24,14 +24,26 @@
 1. SOLID Rars are only supported in the RarReader API.
 2. Zip format supports pkware and WinzipAES encryption. However, encrypted LZMA is not supported. Zip64 reading/writing is supported but only with seekable streams as the Zip spec doesn't support Zip64 data in post data descriptors. Deflate64 is only supported for reading. See [Zip Format Notes](#zip-format-notes) for details on multi-volume archives and streaming behavior.
 3. The Tar format requires a file size in the header. If no size is specified to the TarWriter and the stream is not seekable, then an exception will be thrown.
-4. The 7Zip format doesn't allow for reading as a forward-only stream so 7Zip is only supported through the Archive API
+4. The 7Zip format doesn't allow for reading as a forward-only stream so 7Zip is only supported through the Archive API. See [7Zip Format Notes](#7zip-format-notes) for details on async extraction behavior.
 5. LZip has no support for extra data like the file name or timestamp. There is a default filename used when looking at the entry Key on the archive.
 
 ### Zip Format Notes
 
 - Multi-volume/split ZIP archives require ZipArchive (seekable streams) as ZipReader cannot seek across volume files.
 - ZipReader processes entries from LocalEntry headers (which include directory entries ending with `/`) and intentionally skips DirectoryEntry headers from the central directory, as they are redundant in streaming mode - all entry data comes from LocalEntry headers which ZipReader has already processed.
 
+### 7Zip Format Notes
+
+- **Async Extraction Performance**: When using async extraction methods (e.g., `ExtractAllEntries()` with `MoveToNextEntryAsync()`), each file creates its own decompression stream to avoid state corruption in the LZMA decoder. This is less efficient than synchronous extraction, which can reuse a single decompression stream for multiple files in the same folder.
+
+  **Performance Impact**: For archives with many small files in the same compression folder, async extraction will be slower than synchronous extraction because it must:
+  1. Create a new LZMA decoder for each file
+  2. Skip through the decompressed data to reach each file's starting position
+
+  **Recommendation**: For best performance with 7Zip archives, use synchronous extraction methods (`MoveToNextEntry()` and `WriteEntryToDirectory()`) when possible. Use async methods only when you need to avoid blocking the thread (e.g., in UI applications or async-only contexts).
+
+  **Technical Details**: 7Zip archives group files into "folders" (compression units), where all files in a folder share one continuous LZMA-compressed stream. The LZMA decoder maintains internal state (dictionary window, decoder positions) that assumes sequential, non-interruptible processing. Async operations can yield control during awaits, which would corrupt this shared state. To avoid this, async extraction creates a fresh decoder stream for each file.
+
 ## Compression Streams
 
 For those who want to directly compress/decompress bits. The single file formats are represented here as well. However, BZip2, LZip and XZ have no metadata (GZip has a little) so using them without something like a Tar file makes little sense.

build/Program.cs

@@ -11,6 +11,7 @@
 const string Build = "build";
 const string Test = "test";
 const string Format = "format";
+const string CheckFormat = "check-format";
 const string Publish = "publish";
 
 Target(
@@ -42,12 +43,20 @@ void RemoveDirectory(string d)
 Target(
     Format,
     () =>
+    {
+        Run("dotnet", "tool restore");
+        Run("dotnet", "csharpier format .");
+    }
+);
+Target(
+    CheckFormat,
+    () =>
     {
         Run("dotnet", "tool restore");
         Run("dotnet", "csharpier check .");
     }
 );
-Target(Restore, [Format], () => Run("dotnet", "restore"));
+Target(Restore, [CheckFormat], () => Run("dotnet", "restore"));
 
 Target(
     Build,

src/SharpCompress/Archives/AbstractArchive.cs

@@ -8,7 +8,7 @@
 
 namespace SharpCompress.Archives;
 
-public abstract class AbstractArchive<TEntry, TVolume> : IArchive, IArchiveExtractionListener
+public abstract class AbstractArchive<TEntry, TVolume> : IArchive
     where TEntry : IArchiveEntry
     where TVolume : IVolume
 {
@@ -17,11 +17,6 @@ public abstract class AbstractArchive<TEntry, TVolume> : IArchive, IArchiveExtra
     private bool _disposed;
     private readonly SourceStream? _sourceStream;
 
-    public event EventHandler<ArchiveExtractionEventArgs<IArchiveEntry>>? EntryExtractionBegin;
-    public event EventHandler<ArchiveExtractionEventArgs<IArchiveEntry>>? EntryExtractionEnd;
-
-    public event EventHandler<CompressedBytesReadEventArgs>? CompressedBytesRead;
-    public event EventHandler<FilePartExtractionBeginEventArgs>? FilePartExtractionBegin;
     protected ReaderOptions ReaderOptions { get; }
 
     internal AbstractArchive(ArchiveType type, SourceStream sourceStream)
@@ -43,12 +38,6 @@ internal AbstractArchive(ArchiveType type)
 
     public ArchiveType Type { get; }
 
-    void IArchiveExtractionListener.FireEntryExtractionBegin(IArchiveEntry entry) =>
-        EntryExtractionBegin?.Invoke(this, new ArchiveExtractionEventArgs<IArchiveEntry>(entry));
-
-    void IArchiveExtractionListener.FireEntryExtractionEnd(IArchiveEntry entry) =>
-        EntryExtractionEnd?.Invoke(this, new ArchiveExtractionEventArgs<IArchiveEntry>(entry));
-
     private static Stream CheckStreams(Stream stream)
     {
         if (!stream.CanSeek || !stream.CanRead)
@@ -99,38 +88,12 @@ public virtual void Dispose()
         }
     }
 
-    void IArchiveExtractionListener.EnsureEntriesLoaded()
+    private void EnsureEntriesLoaded()
     {
         _lazyEntries.EnsureFullyLoaded();
         _lazyVolumes.EnsureFullyLoaded();
     }
 
-    void IExtractionListener.FireCompressedBytesRead(
-        long currentPartCompressedBytes,
-        long compressedReadBytes
-    ) =>
-        CompressedBytesRead?.Invoke(
-            this,
-            new CompressedBytesReadEventArgs(
-                currentFilePartCompressedBytesRead: currentPartCompressedBytes,
-                compressedBytesRead: compressedReadBytes
-            )
-        );
-
-    void IExtractionListener.FireFilePartExtractionBegin(
-        string name,
-        long size,
-        long compressedSize
-    ) =>
-        FilePartExtractionBegin?.Invoke(
-            this,
-            new FilePartExtractionBeginEventArgs(
-                compressedSize: compressedSize,
-                size: size,
-                name: name
-            )
-        );
-
     /// <summary>
     /// Use this method to extract all entries in an archive in order.
     /// This is primarily for SOLID Rar Archives or 7Zip Archives as they need to be
@@ -150,7 +113,7 @@ public IReader ExtractAllEntries()
                 "ExtractAllEntries can only be used on solid archives or 7Zip archives (which require random access)."
             );
         }
-        ((IArchiveExtractionListener)this).EnsureEntriesLoaded();
+        EnsureEntriesLoaded();
         return CreateReaderForSolidExtraction();
     }
 
@@ -173,7 +136,7 @@ public bool IsComplete
     {
         get
         {
-            ((IArchiveExtractionListener)this).EnsureEntriesLoaded();
+            EnsureEntriesLoaded();
             return Entries.All(x => x.IsComplete);
         }
     }

src/SharpCompress/Archives/IArchive.cs

@@ -7,12 +7,6 @@ namespace SharpCompress.Archives;
 
 public interface IArchive : IDisposable
 {
-    event EventHandler<ArchiveExtractionEventArgs<IArchiveEntry>> EntryExtractionBegin;
-    event EventHandler<ArchiveExtractionEventArgs<IArchiveEntry>> EntryExtractionEnd;
-
-    event EventHandler<CompressedBytesReadEventArgs> CompressedBytesRead;
-    event EventHandler<FilePartExtractionBeginEventArgs> FilePartExtractionBegin;
-
     IEnumerable<IArchiveEntry> Entries { get; }
     IEnumerable<IVolume> Volumes { get; }
 

src/SharpCompress/Archives/IArchiveEntryExtensions.cs

@@ -1,3 +1,4 @@
+using System;
 using System.IO;
 using System.Threading;
 using System.Threading.Tasks;
@@ -8,56 +9,89 @@ namespace SharpCompress.Archives;
 
 public static class IArchiveEntryExtensions
 {
-    public static void WriteTo(this IArchiveEntry archiveEntry, Stream streamToWriteTo)
+    private const int BufferSize = 81920;
+
+    /// <summary>
+    /// Extract entry to the specified stream.
+    /// </summary>
+    /// <param name="archiveEntry">The archive entry to extract.</param>
+    /// <param name="streamToWriteTo">The stream to write the entry content to.</param>
+    /// <param name="progress">Optional progress reporter for tracking extraction progress.</param>
+    public static void WriteTo(
+        this IArchiveEntry archiveEntry,
+        Stream streamToWriteTo,
+        IProgress<ProgressReport>? progress = null
+    )
     {
         if (archiveEntry.IsDirectory)
         {
             throw new ExtractionException("Entry is a file directory and cannot be extracted.");
         }
 
-        var streamListener = (IArchiveExtractionListener)archiveEntry.Archive;
-        streamListener.EnsureEntriesLoaded();
-        streamListener.FireEntryExtractionBegin(archiveEntry);
-        streamListener.FireFilePartExtractionBegin(
-            archiveEntry.Key ?? "Key",
-            archiveEntry.Size,
-            archiveEntry.CompressedSize
-        );
-        var entryStream = archiveEntry.OpenEntryStream();
-        using (entryStream)
-        {
-            using Stream s = new ListeningStream(streamListener, entryStream);
-            s.CopyTo(streamToWriteTo);
-        }
-        streamListener.FireEntryExtractionEnd(archiveEntry);
+        using var entryStream = archiveEntry.OpenEntryStream();
+        var sourceStream = WrapWithProgress(entryStream, archiveEntry, progress);
+        sourceStream.CopyTo(streamToWriteTo, BufferSize);
     }
 
+    /// <summary>
+    /// Extract entry to the specified stream asynchronously.
+    /// </summary>
+    /// <param name="archiveEntry">The archive entry to extract.</param>
+    /// <param name="streamToWriteTo">The stream to write the entry content to.</param>
+    /// <param name="cancellationToken">Cancellation token.</param>
+    /// <param name="progress">Optional progress reporter for tracking extraction progress.</param>
     public static async Task WriteToAsync(
         this IArchiveEntry archiveEntry,
         Stream streamToWriteTo,
-        CancellationToken cancellationToken = default
+        CancellationToken cancellationToken = default,
+        IProgress<ProgressReport>? progress = null
     )
     {
         if (archiveEntry.IsDirectory)
         {
             throw new ExtractionException("Entry is a file directory and cannot be extracted.");
         }
 
-        var streamListener = (IArchiveExtractionListener)archiveEntry.Archive;
-        streamListener.EnsureEntriesLoaded();
-        streamListener.FireEntryExtractionBegin(archiveEntry);
-        streamListener.FireFilePartExtractionBegin(
-            archiveEntry.Key ?? "Key",
-            archiveEntry.Size,
-            archiveEntry.CompressedSize
+        using var entryStream = archiveEntry.OpenEntryStream();
+        var sourceStream = WrapWithProgress(entryStream, archiveEntry, progress);
+        await sourceStream
+            .CopyToAsync(streamToWriteTo, BufferSize, cancellationToken)
+            .ConfigureAwait(false);
+    }
+
+    private static Stream WrapWithProgress(
+        Stream source,
+        IArchiveEntry entry,
+        IProgress<ProgressReport>? progress
+    )
+    {
+        if (progress is null)
+        {
+            return source;
+        }
+
+        var entryPath = entry.Key ?? string.Empty;
+        long? totalBytes = GetEntrySizeSafe(entry);
+        return new ProgressReportingStream(
+            source,
+            progress,
+            entryPath,
+            totalBytes,
+            leaveOpen: true
         );
-        var entryStream = archiveEntry.OpenEntryStream();
-        using (entryStream)
+    }
+
+    private static long? GetEntrySizeSafe(IArchiveEntry entry)
+    {
+        try
+        {
+            var size = entry.Size;
+            return size >= 0 ? size : null;
+        }
+        catch (NotImplementedException)
         {
-            using Stream s = new ListeningStream(streamListener, entryStream);
-            await s.CopyToAsync(streamToWriteTo, 81920, cancellationToken).ConfigureAwait(false);
+            return null;
         }
-        streamListener.FireEntryExtractionEnd(archiveEntry);
     }
 
     /// <summary>
@@ -127,7 +161,9 @@ public static Task WriteToFileAsync(
             async (x, fm) =>
             {
                 using var fs = File.Open(destinationFileName, fm);
-                await entry.WriteToAsync(fs, cancellationToken).ConfigureAwait(false);
+                await entry
+                    .WriteToAsync(fs, progress: null, cancellationToken: cancellationToken)
+                    .ConfigureAwait(false);
             },
             cancellationToken
         );

src/SharpCompress/Archives/Rar/RarArchiveEntry.cs

@@ -76,15 +76,15 @@ public Stream OpenEntryStream()
             stream = new RarStream(
                 archive.UnpackV1.Value,
                 FileHeader,
-                new MultiVolumeReadOnlyStream(Parts.Cast<RarFilePart>(), archive)
+                new MultiVolumeReadOnlyStream(Parts.Cast<RarFilePart>())
             );
         }
         else
         {
             stream = new RarStream(
                 archive.UnpackV2017.Value,
                 FileHeader,
-                new MultiVolumeReadOnlyStream(Parts.Cast<RarFilePart>(), archive)
+                new MultiVolumeReadOnlyStream(Parts.Cast<RarFilePart>())
             );
         }
 
@@ -100,15 +100,15 @@ public async Task<Stream> OpenEntryStreamAsync(CancellationToken cancellationTok
             stream = new RarStream(
                 archive.UnpackV1.Value,
                 FileHeader,
-                new MultiVolumeReadOnlyStream(Parts.Cast<RarFilePart>(), archive)
+                new MultiVolumeReadOnlyStream(Parts.Cast<RarFilePart>())
             );
         }
         else
         {
             stream = new RarStream(
                 archive.UnpackV2017.Value,
                 FileHeader,
-                new MultiVolumeReadOnlyStream(Parts.Cast<RarFilePart>(), archive)
+                new MultiVolumeReadOnlyStream(Parts.Cast<RarFilePart>())
             );
         }