n, perr := strconv.ParseInt(nStr, 10, 0) // Intentionally parse as native int
	if perr != nil || n < 5 || n > int64(len(s)) {
		return "", "", s, ErrHeader
	}
	n -= int64(len(nStr) + 1) // convert from index in s to index in rest
	if n <= 0 {
		return "", "", s, ErrHeader
	}

	// Extract everything between the space and the final newline.
	rec, nl, rem := rest[:n-1], rest[n-1:n], rest[n:]
	if nl != "\n" {