char-info/src/indicators.ts

Unicode character information library.

import type { Interval } from "node-interval-tree";
import type { CharClassIndicator } from "./indicator-type";
import type { UnicodeCharGroup } from "./unicode-lookup";

function binarySearchInIntervals(intervals: Interval[]) {
    return function bin(start: number, end: number, char: number) {
        if (start > end) {
            return false;
        }
        const mid = (start + end) >> 1;
        const midInterval = intervals[mid];
        if (midInterval.low > char) {
            return bin(start, mid - 1, char);
        }
        if (midInterval.high < char) {
            return bin(mid + 1, end, char);
        }
        return true;
    };
}

/** Basic implementation for the CharClassIndicator, using binary search in an array of ranges. */
export class BasicCharClassIndicator implements CharClassIndicator {
    _binarySearchInIntervals: (start: number, end: number, char: number) => boolean;

    constructor(private _group: UnicodeCharGroup) {
        const intervals = _group.intervals;
        this._binarySearchInIntervals = binarySearchInIntervals(intervals);
        this.char = this.char.bind(this);
        this.code = this.code.bind(this);
    }

    code(char: number) {
        const intervals = this._group.intervals;
        return this._binarySearchInIntervals(0, intervals.length - 1, char);
    }

    char(char: string) {
        if (char === "") return false;
        return this.code(char.codePointAt(0)!);
    }
}