code: func utxoEntryHeaderCode(entry *UtxoEntry) (uint64, error) {
  	if entry.IsSpent() {
  		return 0, AssertError("attempt to serialize spent utxo header")
  	}
  
  	// As described in the serialization format comments, the header code
  	// encodes the height shifted over one bit and the coinbase flag in the
  	// lowest bit.
  	headerCode := uint64(entry.BlockHeight()) << 1
  	if entry.IsCoinBase() {
  		headerCode |= 0x01
  	}
  
  	return headerCode, nil
  }
docs: // utxoEntryHeaderCode returns the calculated header code to be used when
  // serializing the provided utxo entry.