""" The MIT License (MIT) Copyright (c) 2023 Arduino SA Copyright (c) 2018 KPN (Jan Bogaerts) Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. """ import io import struct class CBORDecodeError(Exception): """Raised when an error occurs deserializing a CBOR datastream.""" break_marker = object() class CBORSimpleValue(object): """ Represents a CBOR "simple value". :param int value: the value (0-255) """ def __init__(self, value): if value < 0 or value > 255: raise TypeError("simple value too big") self.value = value def __eq__(self, other): if isinstance(other, CBORSimpleValue): return self.value == other.value elif isinstance(other, int): return self.value == other return NotImplemented def __repr__(self): return "CBORSimpleValue({self.value})".format(self=self) def decode_uint(decoder, subtype, allow_indefinite=False): # Major tag 0 if subtype < 24: return subtype elif subtype == 24: return struct.unpack(">B", decoder.read(1))[0] elif subtype == 25: return struct.unpack(">H", decoder.read(2))[0] elif subtype == 26: return struct.unpack(">L", decoder.read(4))[0] elif subtype == 27: return struct.unpack(">Q", decoder.read(8))[0] elif subtype == 31 and allow_indefinite: return None else: raise CBORDecodeError("unknown unsigned integer subtype 0x%x" % subtype) def decode_negint(decoder, subtype): # Major tag 1 uint = decode_uint(decoder, subtype) return -uint - 1 def decode_bytestring(decoder, subtype): # Major tag 2 length = decode_uint(decoder, subtype, allow_indefinite=True) if length is None: # Indefinite length buf = bytearray() while True: initial_byte = decoder.read(1)[0] if initial_byte == 255: return buf else: length = decode_uint(decoder, initial_byte & 31) value = decoder.read(length) buf.extend(value) else: return decoder.read(length) def decode_string(decoder, subtype): # Major tag 3 return decode_bytestring(decoder, subtype).decode("utf-8") def decode_array(decoder, subtype): # Major tag 4 items = [] length = decode_uint(decoder, subtype, allow_indefinite=True) if length is None: # Indefinite length while True: value = decoder.decode() if value is break_marker: break else: items.append(value) else: for _ in range(length): item = decoder.decode() items.append(item) return items def decode_map(decoder, subtype): # Major tag 5 dictionary = {} length = decode_uint(decoder, subtype, allow_indefinite=True) if length is None: # Indefinite length while True: key = decoder.decode() if key is break_marker: break else: value = decoder.decode() dictionary[key] = value else: for _ in range(length): key = decoder.decode() value = decoder.decode() dictionary[key] = value return dictionary def decode_special(decoder, subtype): # Simple value if subtype < 20: return CBORSimpleValue(subtype) # Major tag 7 return special_decoders[subtype](decoder) def decode_simple_value(decoder): return CBORSimpleValue(struct.unpack(">B", decoder.read(1))[0]) def decode_float16(decoder): payload = decoder.read(2) raise NotImplementedError # no float16 unpack function def decode_float32(decoder): return struct.unpack(">f", decoder.read(4))[0] def decode_float64(decoder): return struct.unpack(">d", decoder.read(8))[0] major_decoders = { 0: decode_uint, 1: decode_negint, 2: decode_bytestring, 3: decode_string, 4: decode_array, 5: decode_map, 7: decode_special, } special_decoders = { 20: lambda self: False, 21: lambda self: True, 22: lambda self: None, # 23 is undefined 24: decode_simple_value, 25: decode_float16, 26: decode_float32, 27: decode_float64, 31: lambda self: break_marker, } class CBORDecoder(object): """ Deserializes a CBOR encoded byte stream. """ def __init__(self, fp): self.fp = fp def read(self, amount): """ Read bytes from the data stream. :param int amount: the number of bytes to read """ data = self.fp.read(amount) if len(data) < amount: raise CBORDecodeError( "premature end of stream (expected to read {} bytes, got {} instead)".format( amount, len(data) ) ) return data def decode(self): """ Decode the next value from the stream. :raises CBORDecodeError: if there is any problem decoding the stream """ try: initial_byte = self.fp.read(1)[0] major_type = initial_byte >> 5 subtype = initial_byte & 31 except Exception as e: raise CBORDecodeError( "error reading major type at index {}: {}".format(self.fp.tell(), e) ) decoder = major_decoders[major_type] try: return decoder(self, subtype) except CBORDecodeError: raise except Exception as e: raise CBORDecodeError( "error decoding value {}".format(e) ) # tell doesn't work on micropython at the moment def loads(payload, **kwargs): """ Deserialize an object from a bytestring. :param bytes payload: the bytestring to serialize :param kwargs: keyword arguments passed to :class:`~.CBORDecoder` :return: the deserialized object """ fp = io.BytesIO(payload) return CBORDecoder(fp, **kwargs).decode() def load(fp, **kwargs): """ Deserialize an object from an open file. :param fp: the input file (any file-like object) :param kwargs: keyword arguments passed to :class:`~.CBORDecoder` :return: the deserialized object """ return CBORDecoder(fp, **kwargs).decode()