fieldBuf := extra.sub(fieldSize)

		switch fieldTag {
		case zip64ExtraID:
			f.zip64 = true

			// update directory values from the zip64 extra block.
			// They should only be consulted if the sizes read earlier
			// are maxed out.
			// See golang.org/issue/13367.
			if needUSize {
				needUSize = false
				if len(fieldBuf) < 8 {
					return ErrFormat
				}
				f.UncompressedSize64 = fieldBuf.uint64()
			}

		case TypeGNULongName, TypeGNULongLink:
			format.mayOnlyBe(FormatGNU)
			realname, err := readSpecialFile(tr)
			if err != nil {
				return nil, err
			}

			var p parser
			switch hdr.Typeflag {
			case TypeGNULongName:
				gnuLongName = p.parseString(realname)
			case TypeGNULongLink:
				gnuLongLink = p.parseString(realname)
			}