Function utf32ConcatMap

src/Strings.ts:84–125

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

}

export function utf32ConcatMap(mapper: (codePoint: 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) {
            let cc = s.charCodeAt(i);
            if (!charNoEscapeMap[cc]) {
                if (cs === null) cs = [];
                cs.push(s.substring(start, i));

                if (isHighSurrogate(cc)) {
                    const highSurrogate = cc;
                    i++;
                    const lowSurrogate = s.charCodeAt(i);
                    assert(isLowSurrogate(lowSurrogate), "High surrogate not followed by low surrogate");
                    const highBits = highSurrogate - 0xd800;
                    const lowBits = lowSurrogate - 0xdc00;
                    cc = 0x10000 + lowBits + (highBits << 10);
                }

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

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

        if (cs === null) return s;

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

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

export function utf16LegalizeCharacters(isLegal: (utf16Unit: number) => boolean): (s: string) => string {
    return utf16ConcatMap(u => (isLegal(u) ? String.fromCharCode(u) : ""));