xlHeaderVersion = 3
	xlMetaVersion   = 2
)

type xlHeaders struct {
	versions           int
	headerVer, metaVer uint
}

func decodeXLHeaders(buf []byte) (x xlHeaders, b []byte, err error) {
	x.headerVer, buf, err = msgp.ReadUintBytes(buf)
	if err != nil {
		return x, buf, err
	}
	x.metaVer, buf, err = msgp.ReadUintBytes(buf)
	if err != nil {
		return x, buf, err
	}
	if x.headerVer > xlHeaderVersion {