Function getNextCodePoint

contributes/src/vs/base/common/strings.ts:477–486

(str: string, len: number, offset: number)

 * get the code point that begins at offset `offset`
 */
export function getNextCodePoint(str: string, len: number, offset: number): number {
	const charCode = str.charCodeAt(offset);
	if (isHighSurrogate(charCode) && offset + 1 < len) {
		const nextCharCode = str.charCodeAt(offset + 1);
		if (isLowSurrogate(nextCharCode)) {
			return computeCodePoint(charCode, nextCharCode);
		}
	}
	return charCode;
}

/**
 * get the code point that ends right before offset `offset`