def peek(self, n=1):
        """Returns buffered bytes without advancing the position."""
        if n > len(self._readbuffer) - self._offset:
            chunk = self.read(n)
            if len(chunk) > self._offset:
                self._readbuffer = chunk + self._readbuffer[self._offset:]
                self._offset = 0
            else:
                self._offset -= len(chunk)

        # Return up to 512 bytes to reduce allocation overhead for tight loops.
        return self._readbuffer[self._offset: self._offset + 512]
Returns buffered bytes without advancing the position.