Skip to content

News

louis-rs Release 0.3.0

22 Sep 2026 - louis-rs

Version 0.3.0 of louis-rs, the from-scratch Rust reimplementation of liblouis, is now available on crates.io.

Where it stands. 98.6% of the liblouis test suite passes — some 2.2 million assertions, forward and backward combined. All but one of the 458 table files under tables/ compile.

What works today:

  • Translation in both directions, full multi-stage pipeline: correct before the main stage, pass2–pass4 after.
  • Contractions and the whole word family, word, begword, midword, endword, midendword, prfword, sufword, partword, begmidword with their before/after class constraints.
  • match and context rules through a purpose-built regexp VM that compiles patterns at table load and matches in linear time.
  • Braille indicators: number sign, capitalisation at all three tiers including caps passages, letter sign, nocontract, and the generic begmode/endmode family.
  • Emphasis: begemph/endemph and the word/symbol tiers.
  • Computer braille as a full pipeline feature — comp6, compbrl, begcomp/endcomp.
  • Backward indication for capsletter, begcapsword/endcapsword, numsign/nonumsign and the no-contract family.
  • Position mapping: inputPos, outputPos and cursorPos, composed across every pipeline stage in both directions.
  • Hyphenation natively: liblouis .dic files parsed directly, no external crate, no conversion step.
  • Display tables as a pipeline stage, --display on the CLI.
  • Translator::with_search_path for host applications that manage their own table locations.
  • A CLI: parse, translate, trace, check, query.

Care for a taste test? louis trace shows every rule that fired, in order, with the stage it fired in:

$ export LOUIS_TABLE_PATH=/usr/share/liblouis/tables
$ louis trace en-us-g2.ctb "Mother's Day"
⠠⠐⠍⠄⠎⠀⠠⠐⠙
┌───┬────────┬────┬──────────────────┬───────┐
│   │ From   │ To │ Rule             │ Stage │
├───┼────────┼────┼──────────────────┼───────┤
│ 1 │        │ ⠠  │ capsletter ⠠     │ Main  │
│ 2 │ mother │ ⠐⠍ │ always mother ⠐⠍ │ Main  │
│ 3 │ 's     │ ⠄⠎ │ endword 's ⠄⠎    │ Main  │
│ 4 │        │ ⠀  │ space   ⠀        │ Main  │
│ 5 │        │ ⠠  │ capsletter ⠠     │ Main  │
│ 6 │ day    │ ⠐⠙ │ always day ⠐⠙    │ Main  │
└───┴────────┴────┴──────────────────┴───────┘

louis check runs your YAML specs, --summary gives a per-file table, and louis query finds tables by language and grade.

Security. This release fixes three findings from Shielder’s security audit for OSTIF: a stack overflow on a crafted include chain, exponential blowup on nested quantifiers in match/context patterns (the engine is now a linear-time Pike VM), and a panic on double negation. Worth noting that all three are logic bugs — stack depth, algorithmic blowup, an unhandled case — rather than the memory corruption that the C implementation’s CVEs keep coming back to.

Python. Leonard de Ruijter has written PyO3 bindings: liblouis/louis-py.

What it isn’t yet. This is not a 100% replacement for liblouis yet. The library API is not stable. No C ABI. partialTrans and compbrlAtCursor/compbrlLeftCursor aren’t implemented. Back-translation returns text but not typeform. Have a look at the parity report for the remaining issues, if you want somewhere to start contributing.

Installation:

cargo install louis-rs

The source is at liblouis/louis-rs, licensed LGPL-2.1-or-later.

Older news