Lzip.Lib 1.1.41

Lzip.Lib

Pure-managed lzip (LZMA1) codec for .NET -- a fast, AOT/trim-friendly compressor and decompressor for the lzip container format, including multi-member files that are decoded in parallel. Output is read by the reference lzip binary. No external lzip binary required.

1.0 shipped the decoder; 1.1 adds the encoder (LZMA1 + lzip member framing + -b-style member splitting).

Install

dotnet add package Lzip.Lib

Usage

using SharpAstro.Lzip;

// From a byte array:
byte[] data = LzipDecoder.Decompress(File.ReadAllBytes("catalog.lz"));

// From a stream:
using var stream = File.OpenRead("catalog.lz");
byte[] fromStream = LzipDecoder.Decompress(stream);

// Lazily as a stream:
using var decompressed = LzipDecoder.DecompressToStream(File.OpenRead("catalog.lz"));

Multi-member lzip files (e.g. produced by lzip -b) are detected and decoded across cores automatically.

Compressing

using SharpAstro.Lzip;

// Best ratio (approximates `lzip -9`), single member:
byte[] lz = LzipEncoder.Compress(File.ReadAllBytes("catalog.json"));

// Choose a level (0..9) and split into independent members for parallel decode (like `lzip -b`):
byte[] chunked = LzipEncoder.Compress(data, new LzipOptions { Level = 9, MemberSize = 2 << 20 });

// Stream in / stream out:
using var input = File.OpenRead("catalog.json");
using var output = File.Create("catalog.json.lz");
LzipEncoder.Compress(input, output);

LzipOptions.Level (0..9) selects lzip's dictionary size and match-length limit; DictionarySize and MatchLenLimit override them; MemberSize (uncompressed bytes per member, 0 = single) enables -b-style splitting. The output is standard lzip -- verified against the reference lzip -t/-d.

Format notes

Each lzip member is a 6-byte header ("LZIP" magic + version + coded dictionary size) followed by an LZMA1 stream (fixed properties lc=3, lp=0, pb=2) and a 20-byte trailer (CRC32 of the uncompressed data + uncompressed size + member size). A multi-member file is simply independent members concatenated.

Attribution

The LZMA1 compression core (src/Lzip.Lib/Lzma/) is vendored from the public-domain 7-Zip LZMA SDK by Igor Pavlov (https://www.7-zip.org/sdk.html). The only edits vs upstream are a #nullable disable header and making the namespace-level types internal so Lzip.Lib's public API stays SharpAstro.Lzip.*. The decoder and the lzip container framing (LzipDecoder, LzipEncoder, LzipFraming) are original code. The lzip format itself was created by Antonio Diaz Diaz; this library was validated for compatibility against the reference lzip binary but contains no lzip (GPL) source.

License

MIT -- see LICENSE. The vendored LZMA SDK is public domain.