code: @Override
  	public void open(FileInputSplit split) throws IOException {
  		super.open(split);
  		initBuffers();
  
  		this.offset = splitStart;
  		if (this.splitStart != 0) {
  			this.stream.seek(offset);
  			readLine();
  			// if the first partial record already pushes the stream over
  			// the limit of our split, then no record starts within this split
  			if (this.overLimit) {
  				this.end = true;
  			}
  		} else {
  			fillBuffer(0);
  		}
  	}
docs: Opens the given input split. This method opens the input stream to the specified file, allocates read buffers
  and positions the stream at the correct position, making sure that any partial record at the beginning is skipped.
  
  @param split The input split to open.
  
  @see org.apache.flink.api.common.io.FileInputFormat#open(org.apache.flink.core.fs.FileInputSplit)