decoder.py 文件源码

def _size_from_ctrl_byte(self, ctrl_byte, offset, type_num):
        size = ctrl_byte & 0x1f
        if type_num == 1:
            return size, offset
        bytes_to_read = 0 if size < 29 else size - 28

        new_offset = offset + bytes_to_read
        size_bytes = self._buffer[offset:new_offset]

        # Using unpack rather than int_from_bytes as it is about 200 lookups
        # per second faster here.
        if size == 29:
            size = 29 + struct.unpack(b'!B', size_bytes)[0]
        elif size == 30:
            size = 285 + struct.unpack(b'!H', size_bytes)[0]
        elif size > 30:
            size = struct.unpack(
                b'!I', size_bytes.rjust(4, b'\x00'))[0] + 65821

        return size, new_offset