needHeaderOffset := f.headerOffset == int64(^uint32(0))

	// Best effort to find what we need.
	// Other zip authors might not even follow the basic format,
	// and we'll just ignore the Extra content in that case.
	var modified time.Time
parseExtras:
	for extra := readBuf(f.Extra); len(extra) >= 4; { // need at least tag and size
		fieldTag := extra.uint16()
		fieldSize := int(extra.uint16())

	for {
		for i := 0; i < s.maxEntries(); i++ {
			// This termination condition is identical to GNU and BSD tar.
			if s.entry(i).offset()[0] == 0x00 {
				break // Don't return, need to process extended headers (even if empty)
			}
			offset := p.parseNumeric(s.entry(i).offset())
			length := p.parseNumeric(s.entry(i).length())
			if p.err != nil {
				return nil, p.err
			}