code: protected function openFile($pFilename)
      {
          File::assertFile($pFilename);
  
          // Open file
          $this->fileHandle = fopen($pFilename, 'r');
          if ($this->fileHandle === false) {
              throw new Exception('Could not open file ' . $pFilename . ' for reading.');
          }
      }
docs: Open file for reading.
  
  @param string $pFilename
  
  @throws Exception