code: def _view_area(stream=bytes(), index=0, count=0):
          
          # Byte stream size
          size = len(stream)
  
          # Start index of the viewing area
          start = max(min(index, size), -size)
          if start < 0:
              start += size
  
          # Stop index of the viewing area
          if not count:
              count = size
          if count > 0:
              stop = min(start + count, size)
          else:
              stop = size
  
          return start, stop
docs: Returns the (start, stop) index for the viewing area of the
          byte stream.
  
          :param int index: start index of the viewing area.
              Default is the begin of the stream.
          :param int count: number of bytes to view.
              Default is to the end of the stream.