def _shrinkBuffer(self):
        if self._pos >= self._shrinkThreshold:
            self._buf = self._buf[self._pos:]
            self._avail -= self._pos
            self._pos = 0
Gets rid of already read data (since we can't rewind).
dataset/ETHPy150Open kdart/pycopia/core/pycopia/inet/fcgi.py/InputStream._shrinkBuffer