Function utf16ConcatMap

src/Strings.ts:43–74

(mapper: (utf16Unit: number) => string)

// FIXME: This is a copy of code in src/Data/String/Util.js
export function utf16ConcatMap(mapper: (utf16Unit: number) => string): (s: string) => string {
    const { charStringMap, charNoEscapeMap } = computeAsciiMap(mapper);

    return function stringConcatMap_inner(s: string): string {
        let cs: string[] | null = null;
        let start = 0;
        let i = 0;
        while (i < s.length) {
            const cc = s.charCodeAt(i);
            if (!charNoEscapeMap[cc]) {
                if (cs === null) cs = [];
                cs.push(s.substring(start, i));

                const str = charStringMap[cc];
                if (str === undefined) {
                    cs.push(mapper(s.charCodeAt(i)));
                } else {
                    cs.push(str);
                }

                start = i + 1;
            }
            i++;
        }

        if (cs === null) return s;

        cs.push(s.substring(start, i));

        return cs.join("");
    };
}

function isHighSurrogate(cc: number): boolean {
    return cc >= 0xd800 && cc <= 0xdbff;