Get a EncodedU32 number.

def _get_struct_encodedu32(self):
        """Get a EncodedU32 number."""
        useful = []
        while True:
            byte = ord(self._src.read(1))
            useful.append(byte)
            if byte < 127:
                # got all the useful bytes
                break

        # transform into bits reordering the bytes
        useful = ['00000000' + bin(b)[2:] for b in useful[::-1]]

        # get the top 7 (*seven*, as the eight one is the flag) and convert
        return int(''.join([b[-7:] for b in useful]), 2)