code: private byte[] getDiskBytes(long offset)
        throws IOException {
      mappedFile.seek(dataOffset + offset);
  
      //Get size of data
      int size = LongPacker.unpackInt(mappedFile);
  
      //Create output bytes
      byte[] res = new byte[size];
  
      //Read data
      if (mappedFile.read(res) == -1) {
        throw new EOFException();
      }
  
      return res;
    }
docs: Get data from disk