def _encode_fixed_header(self, data):
buffer = bytearray(1)
buffer[0] |= self.type << 4
buffer[0] |= (self.dup or 0) << 3
buffer[0] |= (self.qos or 0) << 1
buffer[0] |= self.retain or 0
if not data:
buffer.extend(MQTTUtils.encode_length(0))
else:
buffer.extend(MQTTUtils.encode_length(len(data)))
return bytearray(buffer)
