API Reference

API Reference

Complete API documentation for ZArchiveSharp. All types are in the ZArchiveSharp namespace unless otherwise noted.

Namespaces

Namespace	Contents
ZArchiveSharp	Archive reader/writer, format structures, tool
ZArchiveSharp.Zstd	zstd encoder/decoder, compression options
ZArchiveSharp.Seekable	Seekable zstd format (Foot + Head)
ZArchiveSharp.Pipeline	Pipeline engine, batch operations, progress

---

ZArchiveWriter

Writes .zar archive files. Faithful port of zarchivewriter.cpp.

Constructors

// Stream-based (recommended)
public ZArchiveWriter(Stream output, IZarBlockCompressor? compressor = null)

// Callback-based (for advanced scenarios)
public ZArchiveWriter(
    Action<int> newOutputFile,
    Action<byte[], int, int> writeOutputData,
    IZarBlockCompressor? compressor = null)

Methods

StartNewFile

public void StartNewFile(string path)

Begins writing a new file entry. Path is relative to the archive root, using / or \ as separators.

Parameters:

• path — Relative file path (e.g., "readme.txt", "data/config.json")

Exceptions:

• InvalidOperationException — If already writing a file
• ArgumentException — If path is empty or invalid

AppendData

public void AppendData(ReadOnlySpan<byte> data)

Appends data to the current file. Data is buffered and compressed in 64 KiB blocks.

Parameters:

• data — Bytes to append

Exceptions:

• InvalidOperationException — If no file is being written

Finalize

public void Finalize()

Writes the archive footer and SHA-256 integrity hash. Must be called after all files are written.

Exceptions:

• InvalidOperationException — If already finalized

Dispose

public void Dispose()

Releases resources. Automatically calls Finalize() if not already done.

Example

using var output = File.Create("archive.zar");
using var writer = new ZArchiveWriter(output);

writer.StartNewFile("readme.txt");
writer.AppendData("Hello, World!"u8);

writer.StartNewFile("data/binary.dat");
writer.AppendData(binaryData);

writer.Finalize();

---

ZArchiveReader

Reads .zar archive files. Faithful port of zarchivereader.h.

Static Methods

TryOpen

public static ZArchiveReader? TryOpen(string path)
public static ZArchiveReader? TryOpen(Stream stream, bool leaveOpen = false)

Opens an archive. Returns null on invalid archives (never throws).

Parameters:

• path — Archive file path
• stream — Archive stream
• leaveOpen — Keep stream open after reader disposal

Returns: Reader instance, or null if invalid

Properties

Property	Type	Description
InvalidNode	uint	Constant 0xFFFFFFFF for path-not-found

Methods

FileExists

public bool FileExists(string path)

Checks if a file exists at the given path.

DirectoryExists

public bool DirectoryExists(string path)

Checks if a directory exists at the given path.

ReadFile

public byte[] ReadFile(string path)

Reads and decompresses an entire file.

Parameters:

• path — File path within the archive

Returns: File contents

Exceptions:

• FileNotFoundException — If file not found
• InvalidOperationException — If archive is corrupt

ReadFileRange

public byte[] ReadFileRange(string path, long offset, long length)

Reads a range of bytes from a file.

Parameters:

• path — File path within the archive
• offset — Byte offset within the file
• length — Number of bytes to read

Returns: Requested byte range

ReadDirectory

public IReadOnlyList<ZArchiveReader.DirEntry> ReadDirectory(string path)

Lists directory contents.

Parameters:

• path — Directory path within the archive

Returns: List of directory entries

GetName

public string GetName(uint nameIndex)

Retrieves a name by its index in the name table.

DirEntry Structure

public readonly struct DirEntry
{
    public string Name { get; }      // Entry name
    public bool IsFile { get; }      // True for files
    public bool IsDirectory { get; } // True for directories
    public ulong Size { get; }       // File size (0 for directories)
}

Thread Safety

The reader is thread-safe for concurrent reads (single lock, like the C++ mutex).

Example

using var reader = ZArchiveReader.TryOpen("archive.zar");
if (reader == null)
{
    Console.WriteLine("Invalid archive");
    return;
}

// List root directory
foreach (var entry in reader.ReadDirectory("/"))
{
    Console.WriteLine($"{entry.Name}: {(entry.IsFile ? $"{entry.Size} bytes" : "DIR")}");
}

// Read a file
byte[] data = reader.ReadFile("readme.txt");

---

ZArchiveTool

High-level pack/extract operations. Port of main.cpp CLI behavior.

Static Methods

Pack

public static void Pack(
    string inputDirectory,
    string? outputFile = null,
    Action<string>? progress = null,
    IZarBlockCompressor? compressor = null,
    bool deterministicOrder = true)

Packs a directory into a .zar file.

Parameters:

• inputDirectory — Directory to pack (recursively)
• outputFile — Destination path, or null for <stem>.zar
• progress — Optional per-file callback (relative path)
• compressor — Block compressor, or null for default (zstd level 6)
• deterministicOrder — true (default) sorts entries ordinally

Exceptions:

• IOException — On I/O errors or when refusing to overwrite
• InvalidOperationException — On archive structure errors

Extract

public static void Extract(string inputFile, string outputDirectory)

Extracts an archive to a directory.

Parameters:

• inputFile — Archive file path
• outputDirectory — Destination directory (created if needed)

Exceptions:

• IOException — On I/O errors
• InvalidOperationException — On corrupt archives

---

IZarBlockCompressor

Interface for custom block compressors.

public interface IZarBlockCompressor
{
    int Compress(ReadOnlySpan<byte> source, Span<byte> destination);
}

Returns: Compressed size, or -1 to store the block raw (uncompressed).

ZarRawCompressor

Built-in compressor that stores every block raw (no compression).

public sealed class ZarRawCompressor : IZarBlockCompressor

---

ZstdCompressionOptions (ZArchiveSharp.Zstd)

Options for the zstd compressor.

Properties

Property	Type	Default	Description
Level	int	6	Compression level (1–22)
ChecksumFlag	bool	false	Write 4-byte XXH64 content checksum

Static Methods

public static ZstdCompressionOptions FromLevel(int level)

Creates options for the specified level (1–22).

---

ZstdCompressor (ZArchiveSharp.Zstd)

Pure-C# zstd encoder. Implements IZarBlockCompressor.

Constructor

public ZstdCompressor(ZstdCompressionOptions? options = null)

Properties

Property	Type	Description
Options	ZstdCompressionOptions	Active options

Methods

Compress

public int Compress(ReadOnlySpan<byte> source, Span<byte> destination)

Compresses source as a single-shot frame. Returns frame size, or -1 when the frame would not fit or would not be smaller.

CompressBlock

public byte[] CompressBlock(ReadOnlySpan<byte> source)

Compresses and returns the frame as a new byte array.

GetCompressBound

public static int GetCompressBound(int sourceSize)

Returns the maximum possible compressed size for a given input size.

DecompressFrame

public static byte[] DecompressFrame(ReadOnlySpan<byte> src, int maxSize)

Decompresses a zstd frame.

Parameters:

• src — Frame bytes
• maxSize — Maximum allowed decompressed size

Returns: Decompressed data

---

ZstdStrategy (ZArchiveSharp.Zstd)

Compression strategy selector. Maps to libzstd's ZSTD_strategy.

Value	Name	Typical Levels
1	Fast	1
2	DoubleFast	2–3
3	Greedy	4–5
4	Lazy	6–7
5	Lazy2	8–9
6	BtLazy2	10–12
7	BtOpt	13–15
8	BtUltra	16–18
9	BtUltra2	19–22

---

SeekableWriter (ZArchiveSharp.Seekable)

Writes seekable zstd files with Foot/Head seek tables.

Constructor

public SeekableWriter(SeekableOptions? options = null)

Properties

Property	Type	Description
SeekTable	SeekTable	Current seek table (frames logged so far)

Methods

Write

public void Write(ReadOnlySpan<byte> data)

Appends data, emitting full frames as needed.

Finish

public byte[] Finish()

Finalizes and returns the complete seekable file bytes.

FinishHead

public byte[] FinishHead()

Returns just the seek table as a standalone Head frame.

---

SeekableReader (ZArchiveSharp.Seekable)

Reads seekable zstd files.

Constructors

// Parse embedded Foot table
public SeekableReader(byte[] data)

// Use external seek table (e.g., standalone Head)
public SeekableReader(byte[] data, SeekTable table)

Properties

Property	Type	Description
Table	SeekTable	Parsed seek table
DecompressedLength	long	Total decompressed size
FrameCount	int	Number of frames

Methods

DecompressAll

public byte[] DecompressAll()

Decompresses the entire payload.

DecompressRange

public byte[] DecompressRange(long offset, long length)

Decompresses a byte range, decoding only the frames the range touches.

---

Error Handling

Exception Types

Exception	Namespace	When Thrown
ZarArchiveOpenException	ZArchiveSharp.Pipeline	Archive fails to open
ZarInputOpenException	ZArchiveSharp.Pipeline	Input file cannot be opened
ZarEntryCreateException	ZArchiveSharp.Pipeline	Archive entry creation fails
ZstdException	ZArchiveSharp.Zstd	zstd decompression error
IOException	System	I/O errors
InvalidOperationException	System	Invalid state (corrupt archive, etc.)

Handling Corrupt Archives

try
{
    ZArchiveTool.Extract("corrupt.zar", "output");
}
catch (InvalidOperationException ex)
{
    Console.WriteLine($"Corrupt archive: {ex.Message}");
}
catch (IOException ex)
{
    Console.WriteLine($"I/O error: {ex.Message}");
}

Null-Safe Reader Pattern

// TryOpen never throws — returns null on invalid archives
using var reader = ZArchiveReader.TryOpen("maybe-valid.zar");
if (reader == null)
{
    Console.WriteLine("Invalid or corrupt archive");
    return;
}