#unicode #generate #character #table #fst

app yeslogic-ucd-generate

A program for generating packed representations of the Unicode character database that can be efficiently searched with support for additional tables

5 unstable releases

0.5.0 Jun 4, 2021
0.4.2 Nov 17, 2020
0.4.1 Nov 13, 2020
0.4.0 Nov 13, 2020
0.3.0 Jan 9, 2020

#37 in Text processing

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6.5K SLoC


A command line tool to generate Unicode tables in Rust source code. Tables can typically be generated in one of three formats: a sorted sequence of character ranges, a finite state transducer or a compressed trie. Full support for name canonicalization is also provided. This tool also supports serializing regular expressions as DFAs using the regex-automata crate.

This version of ucd-generate adds the following on top of BurntSushi's version:

  • joining-group sub-command. #32
  • canonical-combining-class sub-command. #45


Since this is mostly intended as a developer tool for use while writing Rust programs, the principle method of installation is from crates.io:

$ cargo install yeslogic-ucd-generate
yeslogic-ucd-generate --help


This somewhat arbitrary example shows the output of generating tables for three properties, and representing them as normal Rust character literal ranges.

To run the example, you need to download the Unicode Character Database (UCD):

$ mkdir /tmp/ucd-13.0.0
$ cd /tmp/ucd-13.0.0
$ curl -LO https://www.unicode.org/Public/zipped/13.0.0/UCD.zip
$ unzip UCD.zip

Note that prior to version 13.0.0, emoji/emoji-data.txt file was distributed separate from the UCD bundle. For these versions, you may need to download this file from https://unicode.org/Public/emoji in order to generate certain tables.

Now tell ucd-generate what you want and point it to the directory created above:

$ ucd-generate property-bool /tmp/ucd-13.0.0 --include Hyphen,Dash,Quotation_Mark --chars

And the output, which is valid Rust source code:

//  ucd-generate property-bool /tmp/ucd-13.0.0 --include Hyphen,Dash,Quotation_Mark --chars
// ucd-generate is available on crates.io.

pub const BY_NAME: &'static [(&'static str, &'static [(char, char)])] = &[
  ("Dash", DASH), ("Hyphen", HYPHEN), ("Quotation_Mark", QUOTATION_MARK),

pub const DASH: &'static [(char, char)] = &[
  ('-', '-'), ('֊', '֊'), ('־', '־'), ('', ''), ('', ''),
  ('', ''), ('', ''), ('', ''), ('', ''),
  ('', ''), ('', ''), ('', ''), ('', ''),
  ('', ''), ('', ''), ('', ''), ('', ''),
  ('', ''), ('', ''), ('', ''), ('', ''),

pub const HYPHEN: &'static [(char, char)] = &[
  ('-', '-'), ('\u{ad}', '\u{ad}'), ('֊', '֊'), ('', ''),
  ('', ''), ('', ''), ('', ''), ('', ''),
  ('', ''), ('', ''),

pub const QUOTATION_MARK: &'static [(char, char)] = &[
  ('\"', '\"'), ('\'', '\''), ('«', '«'), ('»', '»'), ('', ''),
  ('', ''), ('', ''), ('', ''), ('', ''),
  ('', ''), ('', ''), ('', ''), ('', ''),


The ucd-generate tool doesn't have any specific design goals, other than to collect Unicode table generation tasks. If you need ucd-generate to do something and it's reasonably straight-forward to add, then just submitting a PR would be great. Otherwise, file an issue and we can discuss.

Future work

This tool is by no means is exhaustive. In fact, it's not even close to exhaustive, and it may never be. For the most part, the intent of this tool is to collect virtually any kind of Unicode generation task. In theory, this would ideally replace the hodge podge collection of Python programs that is responsible for this task today in various Unicode crates.

It is likely, and perhaps desirable, that this tool will eventually be deprecated in favor of a more complete project like UNIC. The ucd-generate tool was born out of desire to add more principled Unicode support to Rust's regex crate, and it was much easier to develop this out-of-band for my specific requirements.

Finally, the structures generated by this tool may not be optimal. In particular, I strongly suspect that the trie set generator could be improved dramatically.


This repository is home to three sub-crates:

  • ucd-parse - A crate for parsing UCD files into structured data.
  • ucd-trie - Auxiliary type for handling the trie set table format emitted by ucd-generate. This crate has a no_std mode.
  • ucd-util - A purposely small crate for Unicode auxiliary functions. This includes things like symbol or character name canonicalization, ideograph name generation and helper functions for searching property name and value tables.


This project is licensed under either of


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