code: func serializeAddrIndexEntry(blockID uint32, txLoc wire.TxLoc) []byte {
  	// Serialize the entry.
  	serialized := make([]byte, 12)
  	byteOrder.PutUint32(serialized, blockID)
  	byteOrder.PutUint32(serialized[4:], uint32(txLoc.TxStart))
  	byteOrder.PutUint32(serialized[8:], uint32(txLoc.TxLen))
  	return serialized
  }
docs: // serializeAddrIndexEntry serializes the provided block id and transaction
  // location according to the format described in detail above.