docs: public final int toCodePoints(char[] src, int srcOff, int srcLen, int[] dest, int destOff) {
      if (srcLen < 0) {
        throw new IllegalArgumentException("srcLen must be >= 0");
      }
      int codePointCount = 0;
      for (int i = 0; i < srcLen; ) {
        final int cp = codePointAt(src, srcOff + i, srcOff + srcLen);
        final int charCount = Character.charCount(cp);
        dest[destOff + codePointCount++] = cp;
        i += charCount;
      }
      return codePointCount;
    }