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bit_field.py
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bit_field.py
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# Copyright 2021 Jakub Kuczys (https://github.com/jack1142)
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# https://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
from __future__ import annotations
from typing import Any, ClassVar, Optional, Union, final, overload
__all__ = ("BitField", "bit")
class BitField:
"""Base class for all bit field classes."""
__slots__ = ("value",)
#: The mapping of the bit name to the bit value.
BITS: ClassVar[dict[str, int]]
#: The raw bit field value.
value: int
def __init__(self, value: int = 0, **kwargs: bool) -> None:
self.value = value
for bit_name, bit_value in kwargs.items():
if bit_name not in self.BITS:
raise TypeError(
f"{bit_name!r} is not a valid bit for {self.__class__.__name__}."
)
setattr(self, bit_name, bit_value)
def __init_subclass__(cls) -> None:
cls.BITS = {
attr_name: attr_value.bit_value
for base in reversed(cls.__mro__)
for attr_name, attr_value in base.__dict__.items()
if isinstance(attr_value, bit)
}
def __repr__(self) -> str:
return f"<{self.__class__.__name__} value={self.value}>"
def __eq__(self, other: Any) -> bool:
"""
Compare the bit fields for equality.
Parameters:
other:
The other bit field. This bit field needs to be of the same type to
compare equal.
"""
return isinstance(other, self.__class__) and self.value == other.value
def __ne__(self, other: Any) -> bool:
"""
Compare the bit fields for inequality.
Parameters:
other:
The other bit field. This bit field will also be considered unequal
if it is not of the same type.
"""
return not self.__eq__(other)
@final
class bit:
__slots__ = ("bit_value", "name")
name: str
def __init__(self, bit_value: int) -> None:
self.bit_value = bit_value
def __repr__(self) -> str:
return f"<{self.__class__.__name__} {self.name!r} value={self.bit_value}>"
def __set_name__(self, owner: type[BitField], name: str) -> None:
self.name = name
@overload
def __get__(self, instance: BitField, owner: type[BitField]) -> bool:
...
@overload
def __get__(self, instance: None, owner: type[BitField]) -> bit:
...
def __get__(
self, instance: Optional[BitField], owner: type[BitField]
) -> Union[bit, bool]:
if instance is None:
return self
return (instance.value & self.bit_value) == self.bit_value
def __set__(self, instance: BitField, value: bool) -> None:
if value is True:
instance.value |= self.bit_value
elif value is False:
instance.value &= ~self.bit_value
else:
raise TypeError("A bit can only be set to a bool.")