just_zstd 0.2.0

A pure Dart implementation of the Zstandard (RFC 8878) decompression algorithm. Lightweight, dependency-free decoder for zstd compressed data.

Changelog

0.2.0 - 2026-04-22

Added

• ZstdEncoder — Zstandard frame encoder producing raw (uncompressed) blocks.
  • encode(List<int>) and encodeBytes(Uint8List) for creating valid Zstandard frames.
  • Frame header generation: magic number, frame descriptor, content size, and block headers.
  • Raw block encoding for O(n) performance with minimal overhead.
  • Output is fully compatible with ZstdDecoder.

0.1.0 - 2026-03-15

Added

• ZstdDecoder — main decompressor implementing the Zstandard (RFC 8878) frame format.
  • decode(List<int>) and decodeBytes(Uint8List) for decompressing Zstandard frames.
  • Frame header parsing: magic number validation, frame descriptor, window size, optional dictionary ID and content checksum flags.
  • Three block types: raw (direct copy), RLE (run-length), and compressed (entropy-coded).
  • Skippable frame support (0x184D2A50–0x184D2A5F).
  • Descriptive FormatException on malformed input.
• BitReader — LSB-first bit-level stream reader.
  • readBits(), readBit(), readByte(), readBytes(), readUint32LE(), readUint16LE().
  • Byte/bit position tracking, alignment helpers, and buffer-overrun guards.
• FseTable / FseEntry — tANS (table-based Asymmetric Numeral Systems) entropy decoder.
  • FseTable.build() constructs a decoding table from a normalised probability distribution.
  • readNormalizedDistribution() reads the compressed distribution header from the bitstream.
  • Used for literal-length, match-length, and offset codes in compressed blocks.
• HuffmanTable / HuffmanEntry — canonical Huffman decoder for the literals section.
  • HuffmanTable.fromWeights() builds the table from symbol weights.
  • readWeights() supports both FSE-compressed and direct weight header formats.
• Pure Dart implementation — no dart:ffi, no native extensions, no external dependencies.
• Unit tests for BitReader and ZstdDecoder error handling.
• Example usage in example/just_zstd_example.dart.