sudachi_dart

A Flutter FFI plugin for Japanese morphological analysis using Sudachi. Wraps the Rust sudachi.rs library via a C FFI layer.

Platform support

Platform Supported
macOS ✓
Windows ✓
Linux ✗
iOS ✗
Android ✗

Requirements

  • Rust toolchain — the native library is built from source at compile time.
  • A Sudachi system dictionary (.dic file) — not bundled, see Dictionary below.

Usage

import 'package:sudachi_dart/sudachi_dart.dart';

final dict = SudachiDictionary()
await dict.init(
  configPath: '/path/to/sudachi.json',
  dictionaryPath: '/path/to/system_full.dic',
);

final tokenizer = SudachiTokenizer()
await tokenizer.init(dict);

final morphemes = await tokenizer.tokenize('東京都に住む', mode: Mode.c);

for (final m in morphemes) {
  print('${m.surface} [${m.readingForm}] ${m.partOfSpeech.take(2).join('-')}');
}

// Free native resources when done.
tokenizer.dispose();
dict.dispose();

Split modes

Mode Granularity
Mode.a Short / atomic units
Mode.b Middle
Mode.c Natural-language units (default)

Morpheme fields

Field Description
surface The original text span
dictionaryForm Base (dictionary) form
normalizedForm Normalized form
readingForm Yomi (reading) in katakana
partOfSpeech Six elements: [品詞, 品詞細分類1, 品詞細分類2, 品詞細分類3, 活用型, 活用形] — four POS levels, conjugation type, conjugation form. Non-applicable fields contain "*".

Dictionary

The system dictionary is not included in this package because of its size.

  1. Download the full dictionary from the SudachiDict releases — get the SudachiDict_full archive.
  2. Extract system_full.dic and place it somewhere accessible at runtime (e.g. copied to applicationSupportDirectory).
  3. Pass the path to SudachiDictionary.init(dictionaryPath: ...).

A ready-to-use sudachi.json config is included in the example at example/assets/sudachi/sudachi.json. Copy it alongside your dictionary and pass its path to configPath. The dictionary path is supplied separately via dictionaryPath, so no edits to the config file are needed.

Running the example

  1. Download the SudachiDict_full archive from SudachiDict releases.
  2. Extract system_full.dic and place it at: 
    example/assets/sudachi/system_full.dic
    The sudachi.json config is already in that folder.
  3. Run: 
    cd example
flutter run

The example app copies both files to the app's support directory on first launch, then loads the dictionary from there.

Project structure

src/                   C header + Rust source (sudachi_rs_wrapper)
lib/                   Dart API
hook/build.dart        Builds the Rust library at compile time
ffigen.yaml            Generates Dart FFI bindings from the C header

To regenerate the Dart FFI bindings after changing the C header:

dart run ffigen --config ffigen.yaml

See also

Credits & License

This Dart package is licensed under the Apache-2.0 License.

This project wraps and relies on sudachi.rs, developed by Works Applications Co., Ltd., which is licensed under the Apache License 2.0.

Libraries

sudachi_dart