func (f *formatter) formatNumeric(b []byte, x int64) {
	if fitsInOctal(len(b), x) {
		f.formatOctal(b, x)
		return
	}

	if fitsInBase256(len(b), x) {
		for i := len(b) - 1; i >= 0; i-- {
			b[i] = byte(x)
			x >>= 8
		}
		b[0] |= 0x80 // Highest bit indicates binary format
		return
	}

	f.formatOctal(b, 0) // Last resort, just write zero
	f.err = ErrFieldTooLong
}