pycborstream 0.0.4

Stream API using cbor2 to read and write CBOR data.

pycborstream

Simple python API to handle CBOR files as streams. It provides lazy methods to read and write huge CBOR data files saving memory: data can be treated on the fly without having to load the entire structure.

Pycborstream mimics the C++ QCborStreamReader Class and QCborStreamWriter Class API to read and write CBOR data. It uses cbor2 under the hood, and combines it to also read/write directly python dictionnaries and arrays.

Simple usage: write a CBOR data file

from io import BytesIO

from pycborstream import CborStreamEnc

cbor_out = "data.cbor"
with open(cbor_out, "wb") as fp:
    cbor_encoder = CborStreamEnc(fp)
    cbor_encoder.startMap(2)  # start a map containing 2 key/value pairs
    cbor_encoder.append("first_key")
    cbor_encoder.startArray(None)  # start an array of undefined length
    cbor_encoder.append(5)
    cbor_encoder.append(6)
    cbor_encoder.append(7)
    cbor_encoder.endArray()
    cbor_encoder.append("second_key")
    cbor_encoder.append("could be a new map or whatever")
    cbor_encoder.endMap()

Simple usage: read this CBOR data file

from io import BytesIO

from pycborstream import CborStreamDec

with open(cbor_out, "rb") as fp:
    cbor_decoder = CborStreamDec(fp)
    cbor_decoder.enter_container()  # enters the map (containing 2 keys)
    assert cbor_decoder.value() == "first_key"
    assert cbor_decoder.is_array()  # next value is an array
    assert cbor_decoder.length == None  # length of array is not known
    cbor_decoder.enter_container()
    while cbor_decoder.has_next():  # loop on elements in the array
        print(cbor_decoder.value())
    cbor_decoder.leave_container()  # we have to leave container to proceed
    assert cbor_decoder.value() == "second_key"
    assert cbor_decoder.value() == "could be a new map or whatever"