Function decode_signed_value

python/python3/tornado/web.py:3470–3498

(
    secret: _CookieSecretTypes,
    name: str,
    value: Union[None, str, bytes],
    max_age_days: float = 31,
    clock: Optional[Callable[[], float]] = None,
    min_version: Optional[int] = None,
)

def decode_signed_value(
    secret: _CookieSecretTypes,
    name: str,
    value: Union[None, str, bytes],
    max_age_days: float = 31,
    clock: Optional[Callable[[], float]] = None,
    min_version: Optional[int] = None,
) -> Optional[bytes]:
    if clock is None:
        clock = time.time
    if min_version is None:
        min_version = DEFAULT_SIGNED_VALUE_MIN_VERSION
    if min_version > 2:
        raise ValueError("Unsupported min_version %d" % min_version)
    if not value:
        return None

    value = utf8(value)
    version = _get_version(value)

    if version < min_version:
        return None
    if version == 1:
        assert not isinstance(secret, dict)
        return _decode_signed_value_v1(secret, name, value, max_age_days, clock)
    elif version == 2:
        return _decode_signed_value_v2(secret, name, value, max_age_days, clock)
    else:
        return None


def _decode_signed_value_v1(