tw.hdr.AccessTime = time.Time{}
		tw.hdr.ChangeTime = time.Time{}
	}

	allowedFormats, paxHdrs, err := tw.hdr.allowedFormats()
	switch {
	case allowedFormats.has(FormatUSTAR):
		tw.err = tw.writeUSTARHeader(&tw.hdr)
		return tw.err
	case allowedFormats.has(FormatPAX):
		tw.err = tw.writePAXHeader(&tw.hdr, paxHdrs)
		return tw.err
	case allowedFormats.has(FormatGNU):
		tw.err = tw.writeGNUHeader(&tw.hdr)
		return tw.err

	}}

	for i, v := range vectors {
		formats, paxHdrs, err := v.header.allowedFormats()
		if formats != v.formats {
			t.Errorf("test %d, allowedFormats(): got %v, want %v", i, formats, v.formats)
		}
		if formats&FormatPAX > 0 && !maps.Equal(paxHdrs, v.paxHdrs) && !(len(paxHdrs) == 0 && len(v.paxHdrs) == 0) {
			t.Errorf("test %d, allowedFormats():\ngot  %v\nwant %s", i, paxHdrs, v.paxHdrs)
		}

//
// Invariant: logicalRemaining >= physicalRemaining
type fileState interface {
	logicalRemaining() int64
	physicalRemaining() int64
}

// allowedFormats determines which formats can be used.
// The value returned is the logical OR of multiple possible formats.
// If the value is FormatUnknown, then the input Header cannot be encoded
// and an error is returned explaining why.