func (itm *Item) Bytes() (bs []byte) {
	l := itm.dataLen
	dataOffset := uintptr(unsafe.Pointer(itm)) + itemHeaderSize

	hdr := (*reflect.SliceHeader)(unsafe.Pointer(&bs))
	hdr.Data = dataOffset
	hdr.Len = int(l)
	hdr.Cap = hdr.Len
	return
}
func (itm *Item) Bytes() (bs []byte) {
	l := itm.dataLen
	dataOffset := uintptr(unsafe.Pointer(itm)) + itemHeaderSize

	hdr := (*reflect.SliceHeader)(unsafe.Pointer(&bs))
	hdr.Data = dataOffset
	hdr.Len = int(l)
	hdr.Cap = hdr.Len
	return
}
// Bytes return item data bytes