Ferroni

Where Ferroni sits

Ferroni supplies the regex engine for Ferriki, whose Shiki-compatible highlighter uses TextMate grammars to tokenize code. Ferromark combines that highlighting with Markdown rendering. Each tool also works on its own.

A regular expression, run

A lookbehind selects the date; named groups return its parts. This is the committed output of the Rust example shown here.

Run the example: cargo run --example website_sample

use ferroni::prelude::*;

fn main() -> Result<(), RegexError> {
    let regex = Regex::new(r"(?<=Date: )(?<year>\d{4})-(?<month>\d{2})-(?<day>\d{2})")?;
    let text = "Date: 2026-09-26";
    let captures = regex.captures(text).expect("the sample date matches");

    println!("input: {text}");
    for name in ["year", "month", "day"] {
        let value = captures.name(name).expect("the named group exists");
        println!("{name}: {}", value.as_str());
    }
    Ok(())
}

use ferroni::prelude::*;

fn main() -> Result<(), RegexError> {
    let regex = Regex::new(r"(?<=Date: )(?<year>\d{4})-(?<month>\d{2})-(?<day>\d{2})")?;
    let text = "Date: 2026-09-26";
    let captures = regex.captures(text).expect("the sample date matches");

    println!("input: {text}");
    for name in ["year", "month", "day"] {
        let value = captures.name(name).expect("the named group exists");
        println!("{name}: {}", value.as_str());
    }
    Ok(())
}

input: Date: 2026-09-26
year: 2026
month: 09
day: 26

input: Date: 2026-09-26
year: 2026
month: 09
day: 26

Regex engine and scanner, one crate

Match with the idiomatic Regex API, or tokenize with the multi-pattern Scanner that TextMate grammars need. Both come with cargo add ferroni.

use ferroni::prelude::*;

fn main() -> Result<(), RegexError> {
    let re = Regex::new(r"(?<year>\d{4})-(?<month>\d{2})")?;

    let caps = re.captures("Date: 2026-02-12").unwrap();
    assert_eq!(caps.name("year").unwrap().as_str(), "2026");
    Ok(())
}

use ferroni::scanner::{Scanner, ScannerFindOptions};

let mut scanner = Scanner::new(&[
    r"\b(function|const|let|var)\b",
    r#""[^"]*""#,
    r"//.*$",
]).unwrap();

let m = scanner
    .find_next_match(r#"const x = "hello""#, 0, ScannerFindOptions::NONE)
    .unwrap();
assert_eq!(m.index, 0); // "const" matched first

What it covers

Ferroni ports ASCII and UTF-8, two of Oniguruma’s 29 encodings, and leaves out the POSIX and GNU APIs (ADR-003, ADR-012). For the projects built on Oniguruma’s syntax, that means:

• TextMate grammars, VS Code, ShikiCovered

  vscode-oniguruma compiles every pattern as UTF-8. Ferroni's scanner keeps its API shape and its UTF-16 offsets.

• jqCovered

  jq matches on UTF-8 text, which Ferroni handles in full.

• PHP mbregexUTF-8 only

  mb_ereg in Shift_JIS, EUC-JP or another non-UTF-8 encoding is not covered.

• RubyNot a target

  Ruby runs Onigmo, a fork of Oniguruma with its own history and encodings.