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

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"""
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
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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
from functools import wraps
def serialize_tfw_msg(message):
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"""
Create TFW multipart data from message dict
"""
return _serialize_all(message['key'], message)
def with_deserialize_tfw_msg(fun):
@wraps(fun)
def wrapper(message_parts):
message = deserialize_tfw_msg(*message_parts)
return fun(message)
return wrapper
def deserialize_tfw_msg(*args):
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"""
Return message from TFW multipart data
"""
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):
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"""
Return input as bytes
(serialize input if it is JSON)
"""
if not isinstance(data, str):
data = message_bytes(data)
return _encode_if_needed(data)
def message_bytes(message):
return json.dumps(message, sort_keys=True).encode()
def _deserialize_single(data):
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"""
Try parsing input as JSON, return it as
string if parsing fails.
"""
try:
return json.loads(data)
except ValueError:
return _decode_if_needed(data)
def _encode_if_needed(value):
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"""
Return input as bytes
(encode if input is string)
"""
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if isinstance(value, str):
value = value.encode('utf-8')
return value
def _decode_if_needed(value):
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"""
Return input as string
(decode if input is bytes)
"""
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if isinstance(value, (bytes, bytearray)):
value = value.decode('utf-8')
return value