code: private static void invertBuffer(char[] buffer,
                                       int start,
                                       int length) {
  
          for(int i = start, j = start + length - 1; i < j; i++, --j) {
              char temp = buffer[i];
              buffer[i] = buffer[j];
              buffer[j] = temp;
          }
      }
docs: /*
  Name    : invertBuffer
  Function: This function inverts the buffer, it's used
  in case the user specifies the buffer to be
  TEXT_DIRECTION_LOGICAL