public ReaderContextBuilder withFileSystemAndPath(FileSystem fs, Path filePath)
    throws IOException {
    this.withFileSystem(fs).withFilePath(filePath).withFileSize(fs.getFileStatus(filePath).getLen())
      .withInputStreamWrapper(new FSDataInputStreamWrapper(fs, filePath));
    return this;
  }
A builder that helps in building up the ReaderContext
hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/ReaderContextBuilder.java