lzo_neo 0.1.0

Pure Dart implementation of the LZO1X lossless compression algorithm, with liblzo2-compatible streams and zero native dependencies.

lzo_neo

Pure Dart implementation of the LZO compression algorithms. No native code, no FFI: the same code runs on the Dart VM, in AOT builds, and on the web.

LZO is a lossless block compressor optimised for decompression speed. LZO1X is the variant used by lzop, the Linux kernel, btrfs and SquashFS.

Status

Feature	Status
LZO1X decompress (safe, fully validating)	✅
LZO1X compress: lzo1x_1, 1_11, 1_12, 1_15	✅
LZO1X-999, LZO1Y, LZO1Z, LZO1B, LZO1C, LZO1F, LZO1, LZO1A, LZO2A encoders	planned for 0.1.1
lzo1x_optimize / in-place decompression	planned for 0.1.1
LZO-RLE, lzop container	planned for 0.1.1

Compressed LZO blocks carry no header and no original size, so decompression needs the caller to supply the output capacity, exactly like liblzo2.

Install

dependencies:
  lzo_neo: ^0.1.0

Usage

package:blit Bytes are zero-copy views, so slicing does not copy:

import 'package:blit/blit.dart';
import 'package:lzo_neo/lzo_neo.dart';

final codec = Lzo1x();
final original = Bytes.fromString('hello, lzo world!');
final packed = codec.compress(original);
final restored = codec.decompress(packed, original.length);

Zero-allocation operation on raw Uint8List buffers:

final output = Uint8List(codec.compressBound(input.length));
final compressedLength = codec.compressInto(input, output);

final decoded = Uint8List(originalLength);
final decodedLength = codec.decompressInto(output, decoded);

Reuse a codec instance to reuse its compression work memory (64 KiB for Lzo1xLevel.fast1, 8/16/128 KiB for fast11/fast12/fast15).

Safety

The decoder validates every instruction and every write. Malformed, truncated or oversized input throws LzoException with a liblzo2-compatible LzoErrorCode; it never reads out of bounds, writes out of bounds, or loops forever. No memory is allocated while decompressing.

Correctness

Streams are tested against vectors produced by the reference C implementation (liblzo2 2.10) and, in CI, differentially in both directions:

• liblzo2 compress → Dart decompress
• Dart compress → liblzo2 decompress
• Dart compress → Dart decompress

The LZO1X grammar follows liblzo2's src/lzo1x_d.ch and the format description in the Linux kernel (Documentation/staging/lzo.rst).

License

MIT. LZO itself is Copyright (C) Markus F. X. J. Oberhumer and is distributed under the GNU GPL; this package is an independent implementation of the published format.