ZlibInStream::ZlibInStream(int bufSize_)
  : underlying(0), bufSize(bufSize_ ? bufSize_ : DEFAULT_BUF_SIZE), offset(0),
    zs(NULL), bytesIn(0)
{
  ptr = end = start = new U8[bufSize];
  init();
}
The software writes data past the end, or before the beginning, of the intended buffer.