code: @Override
    public FSDataInputStream open(Path hadoopPath, int bufferSize) throws IOException {
      long startTime = System.nanoTime();
      Preconditions.checkArgument(hadoopPath != null, "hadoopPath must not be null");
  
      checkOpen();
  
      logger.atFine().log("GHFS.open: %s, bufferSize: %d (ignored)", hadoopPath, bufferSize);
      URI gcsPath = getGcsPath(hadoopPath);
      GoogleCloudStorageReadOptions readChannelOptions =
          getGcsFs().getOptions().getCloudStorageOptions().getReadChannelOptions();
      GoogleHadoopFSInputStream in =
          new GoogleHadoopFSInputStream(this, gcsPath, readChannelOptions, statistics);
  
      long duration = System.nanoTime() - startTime;
      increment(Counter.OPEN);
      increment(Counter.OPEN_TIME, duration);
      return new FSDataInputStream(in);
    }
docs: Opens the given file for reading.
  
  <p>Note: This function overrides the given bufferSize value with a higher number unless further
  overridden using configuration parameter {@code fs.gs.inputstream.buffer.size}.
  
  @param hadoopPath File to open.
  @param bufferSize Size of buffer to use for IO.
  @return A readable stream.
  @throws FileNotFoundException if the given path does not exist.
  @throws IOException if an error occurs.