code: private List<DomainControllerData> readFromFile(String directoryName) {
          List<DomainControllerData> data = new ArrayList<DomainControllerData>();
          if (directoryName == null) {
              return data;
          }
  
          if (conn == null) {
              init();
          }
  
          try {
              if (usingPreSignedUrls()) {
                  PreSignedUrlParser parsedPut = new PreSignedUrlParser(pre_signed_put_url);
                  directoryName = parsedPut.getPrefix();
              }
              String key = S3Util.sanitize(directoryName) + "/" + S3Util.sanitize(DC_FILE_NAME);
              GetResponse val = conn.get(location, key, null);
              if (val.object != null) {
                  byte[] buf = val.object.data;
                  if (buf != null && buf.length > 0) {
                      try {
                          data = S3Util.domainControllerDataFromByteBuffer(buf);
                      } catch (Exception e) {
                          throw HostControllerLogger.ROOT_LOGGER.failedMarshallingDomainControllerData();
                      }
                  }
              }
              return data;
          } catch (IOException e) {
              throw HostControllerLogger.ROOT_LOGGER.cannotAccessS3File(e.getLocalizedMessage());
          }
      }
docs: Read the domain controller data from an S3 file.
  
  @param directoryName the name of the directory in the bucket that contains the S3 file
  @return the domain controller data