baseimage-tutorial-framework/lib/tfw/networking/serialization.py

# Copyright (C) 2018 Avatao.com Innovative Learning Kft.
# All Rights Reserved. See LICENSE file for details.
"""
TFW JSON message format

message:
{
    "key":     string,    # addressing
    "data":    {...},     # payload
    "trigger": string     # FSM trigger
}

ZeroMQ's sub-pub sockets use enveloped messages
(http://zguide.zeromq.org/page:all#Pub-Sub-Message-Envelopes)
and TFW also uses them internally. This means that on ZMQ sockets
we always send the messages key separately and then the actual
message (which contains the key as well) like so:

socket.send_multipart([message['key'], message])

The purpose of this module is abstracting away this low level behaviour.
"""

import json


def validate_message(message):
    return 'key' in message


def serialize_tfw_msg(message):
    return _serialize_all(message['key'], message)


def deserialize_tfw_msg(*args):
    return _deserialize_all(*args)[1]


def _serialize_all(*args):
    return tuple(_serialize_single(arg) for arg in args)


def _deserialize_all(*args):
    return tuple(_deserialize_single(arg) for arg in args)


def _serialize_single(data):
    if not isinstance(data, str):
        data = json.dumps(data)
    return _encode_if_needed(data)


def _deserialize_single(data):
    try:
        return json.loads(data)
    except ValueError:
        return _decode_if_needed(data)


def _encode_if_needed(value):
    if isinstance(value, str):
        value = value.encode('utf-8')
    return value


def _decode_if_needed(value):
    if isinstance(value, (bytes, bytearray)):
        value = value.decode('utf-8')
    return value