// Add leading zeros, but leave room for a NUL.
	if n := len(b) - len(s) - 1; n > 0 {
		s = strings.Repeat("0", n) + s
	}
	f.formatString(b, s)
}

// fitsInOctal reports whether the integer x fits in a field n-bytes long
// using octal encoding with the appropriate NUL terminator.
func fitsInOctal(n int, x int64) bool {
	octBits := uint(n-1) * 3
	return x >= 0 && (n >= 22 || x < 1<<octBits)
}