Lzma.Net 5.8.3.2

Lzma.Net

A native C# implementation of the XZ/LZMA2/LZMA compression format. No native binaries, no P/Invoke, no liblzma dependency — just pure managed C# code that runs anywhere .NET runs.

Features

• 100% managed C# — zero native dependencies, works on any platform .NET supports
• XZ format — full read/write support for the .xz container format (spec)
• LZMA2 codec — chunked LZMA compression with automatic dictionary resets
• Streaming API — XzCompressStream and XzDecompressStream for processing data without loading it all into memory
• One-shot API — XzCompressor.Compress / Decompress for simple byte-array operations
• Async API — CompressAsync / DecompressAsync and async stream methods for non-blocking I/O
• Multi-threaded compression — parallel block compression via the Threads option
• Presets 0–9 — matching xz CLI compression levels and dictionary sizes
• Extreme mode — equivalent to xz -e, spends more CPU time for better compression
• Integrity checks — CRC32, CRC64, SHA-256, or no check
• Concatenated streams — reads multiple XZ streams appended back-to-back
• Zero-copy design — uses Span<T>, ReadOnlySpan<T>, ArrayPool<T>, and stackalloc throughout
• .NET 8 / 9 / 10 — multi-target support

Installation

dotnet add package LzmaNet

Quick Start

Compress and decompress a byte array

using LzmaNet;

byte[] original = File.ReadAllBytes("data.bin");

// Compress with default settings (preset 6, CRC64)
byte[] compressed = XzCompressor.Compress(original);

// Decompress
byte[] restored = XzCompressor.Decompress(compressed);

Compress with options

using LzmaNet;

var options = new XzCompressOptions
{
    Preset  = 9,       // Maximum compression
    Extreme = true,    // Spend more CPU for slightly better ratio
    Threads = 0,       // Use all available CPUs
};

byte[] compressed = XzCompressor.Compress(data, options);

Stream API — compress a file

using LzmaNet;

using var input  = File.OpenRead("data.bin");
using var output = File.Create("data.xz");
using (var xz = new XzCompressStream(output))
{
    input.CopyTo(xz);
}

Stream API — decompress a file

using LzmaNet;

using var input  = File.OpenRead("data.xz");
using var output = File.Create("data.bin");
using var xz = new XzDecompressStream(input);
xz.CopyTo(output);

Async — compress and decompress

using LzmaNet;

// One-shot async
byte[] compressed = await XzCompressor.CompressAsync(data);
byte[] restored   = await XzCompressor.DecompressAsync(compressed);

Async — stream API

using LzmaNet;

using var input  = File.OpenRead("data.bin");
using var output = File.Create("data.xz");
await using (var xz = new XzCompressStream(output))
{
    await input.CopyToAsync(xz);
}

ASP.NET — decompress an upload on the fly

app.MapPost("/upload", async (HttpRequest request) =>
{
    using var xz = new XzDecompressStream(request.Body);
    using var output = File.Create("uploaded.bin");
    await xz.CopyToAsync(output);
});

Compression Options

All tuning knobs are exposed through the XzCompressOptions class:

Preset dictionary sizes

Benchmarks

See BENCHMARK.md for detailed performance comparisons against native liblzma.

Quick summary (16 MB data, preset 6, single-threaded):

LzmaNet is faster at compression; liblzma is faster at decompression due to decades of hand-optimized C in the range decoder.

Interoperability

Output is fully compatible with the standard xz tool and any other XZ-compliant decoder. The test suite validates round-trip interoperability with the xz CLI in both directions.

Architecture

LzmaNet is structured as a set of layered codecs, all implemented in pure C#:

XzCompressor / XzCompressStream / XzDecompressStream   (public API)
  └─ XZ container format   (header, block, index, footer)
       └─ LZMA2 codec      (chunked wrapper over LZMA)
            └─ LZMA codec  (LZ77 + adaptive range coding)
                 ├─ HC4 match finder (hash-chain, 4-byte hashing)
                 ├─ Range encoder / decoder
                 └─ CRC32 / CRC64 integrity checks

Acknowledgments

This implementation is based on the algorithms and file format from XZ Utils 5.8.3, originally created by Lasse Collin and maintained by the Tukaani Project. The BCJ filter implementations are ported from the liblzma C source.

Special thanks to:

• Lasse Collin — original author of liblzma and the XZ file format
• Jia Tan and other contributors to the Tukaani Project
• Igor Pavlov — creator of the LZMA algorithm and 7-Zip

License

0BSD — free for any use, no attribution required.