code: public function truncate()
  	{
  		if (\is_resource($this->resFile))
  		{
  			ftruncate($this->resFile, 0);
  			rewind($this->resFile);
  		}
  
  		return $this->write('');
  	}
docs: Truncate the file and reset the file pointer
  
  @return boolean True if the operation was successful