Protobuf lengths

pblength.py

from google.protobuf.internal.decoder import _DecodeVarint
from google.protobuf.internal.encoder import _VarintBytes
import datapoint_pb2

def read_message(buf): # buf is a bytestring
    pos = 0 # Start of varint32
    value, new_pos = _DecodeVarint(buf, pos)
    
    msg = datapoint_pb2.DataPoint()
    msg.ParseFromString(buf[new_pos:new_pos+value])
    
    return msg

def write_message(msg, stream):
    message = msg.SerializeToString()
    delimiter = _VarintBytes(len(message))
    stream.write(delimter + message)