octBits := uint(n-1) * 3
	return x >= 0 && (n >= 22 || x < 1<<octBits)
}

// parsePAXTime takes a string of the form %d.%d as described in the PAX
// specification. Note that this implementation allows for negative timestamps,
// which is allowed for by the PAX specification, but not always portable.
func parsePAXTime(s string) (time.Time, error) {
	const maxNanoSecondDigits = 9

		case paxGid:
			id64, err = strconv.ParseInt(v, 10, 64)
			hdr.Gid = int(id64) // Integer overflow possible
		case paxAtime:
			hdr.AccessTime, err = parsePAXTime(v)
		case paxMtime:
			hdr.ModTime, err = parsePAXTime(v)
		case paxCtime:
			hdr.ChangeTime, err = parsePAXTime(v)
		case paxSize:
			hdr.Size, err = strconv.ParseInt(v, 10, 64)
		default:
			if strings.HasPrefix(k, paxSchilyXattr) {
				if hdr.Xattrs == nil {