code: public IndexOffset get(int pos) {
          int i = pos << 3;
          int index = _buffer.getInt(i);
          int offset = _buffer.getInt(i+4);
          return new IndexOffset(index, offset);
      }
docs: Gets the pair of index and offset at the specified <code>pos</code>
  
  @param pos - the position to SegmentIndexBuffer
  @throws IndexOutOfBoundsException if the specified <code>pos</code> is no smaller than the known size.