code: function (start, end) {
      var offsetStart;
      var offsetEnd;
  
      loadBufferIfRequired(start, end);
  
      offsetStart = start - currentRange.start;
      offsetEnd = offsetStart + (end - start);
  
      return buffer.slice(offsetStart, offsetEnd);
    }
docs: Reads data range from the file into the buffer.
  @param {Number} start Absolute start position. Cannot be null.
  @param {Number} end Absolute end position. Cannot be null.