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import abc
import struct
import re
from typing import Optional, Tuple
class MQTTPayload(abc.ABC):
FORMAT = ''
PACKER = {}
UNPACKER = {}
def __init__(self, **kwargs):
for field in self.__class__.__annotations__:
setattr(self, field, kwargs[field])
def pack(self):
args = []
bf_number = -1
bf_arg = 0
bf_progress = 0
for field, field_type in self.__class__.__annotations__.items():
bfp = _bit_field_params(field_type)
if bfp:
n, s, b = bfp
if n != bf_number:
if bf_number != -1:
args.append(bf_arg)
bf_number = n
bf_progress = 0
bf_arg = 0
bf_arg |= (getattr(self, field) & (2 ** b - 1)) << bf_progress
bf_progress += b
else:
if bf_number != -1:
args.append(bf_arg)
bf_number = -1
bf_progress = 0
bf_arg = 0
args.append(self._pack_field(field))
if bf_number != -1:
args.append(bf_arg)
return struct.pack(self.FORMAT, *args)
@classmethod
def unpack(cls, buf: bytes):
data = struct.unpack(cls.FORMAT, buf)
kwargs = {}
i = 0
bf_number = -1
bf_progress = 0
for field, field_type in cls.__annotations__.items():
bfp = _bit_field_params(field_type)
if bfp:
n, s, b = bfp
if n != bf_number:
bf_number = n
bf_progress = 0
kwargs[field] = (data[i] >> bf_progress) & (2 ** b - 1)
bf_progress += b
continue # don't increment i
if bf_number != -1:
bf_number = -1
i += 1
if issubclass(field_type, MQTTPayloadCustomField):
kwargs[field] = field_type.unpack(data[i])
else:
kwargs[field] = cls._unpack_field(field, data[i])
i += 1
return cls(**kwargs)
def _pack_field(self, name):
val = getattr(self, name)
if self.PACKER and name in self.PACKER:
return self.PACKER[name](val)
else:
return val
@classmethod
def _unpack_field(cls, name, val):
if isinstance(val, MQTTPayloadCustomField):
return
if cls.UNPACKER and name in cls.UNPACKER:
return cls.UNPACKER[name](val)
else:
return val
class MQTTPayloadCustomField(abc.ABC):
def __init__(self, **kwargs):
for field in self.__class__.__annotations__:
setattr(self, field, kwargs[field])
@abc.abstractmethod
def __index__(self):
pass
@classmethod
@abc.abstractmethod
def unpack(cls, *args, **kwargs):
pass
def bit_field(seq_no: int, total_bits: int, bits: int):
return type(f'MQTTPayloadBitField_{seq_no}_{total_bits}_{bits}', (object,), {
'seq_no': seq_no,
'total_bits': total_bits,
'bits': bits
})
def _bit_field_params(cl) -> Optional[Tuple[int, ...]]:
match = re.match(r'MQTTPayloadBitField_(\d+)_(\d+)_(\d)$', cl.__name__)
if match is not None:
return tuple([int(match.group(i)) for i in range(1, 4)])
return None
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