Python encoding of "octal numbers" in tar files

tar_octal_ascii_number.py

import typing as t


@t.final
class TarOctalAsciiNumber(int):
    __slots__: t.Sequence[str] = ()

    def __new__(cls, value: int) -> t.Self:
        return super().__new__(cls, value)

    def to_octal_ascii(self, size: int) -> bytes:
        data = oct(self)[2:].encode("ascii") + b"\0"
        if len(data) > size:
            raise ValueError(f"Cannot fit {data} into {size} bytes")
        lpad = b"\0" * (len(data) - size)
        return lpad + data

    @classmethod
    def from_octal_ascii(cls, data: bytes) -> t.Self:
        string = data.strip(b" \0").decode("ascii")
        value = int(string, 8)
        return cls(value)

    def __repr__(self) -> str:
        return f"{type(self).__name__}(value={super()!r}}"