Class NBytesField

scapy/fields.py:1117–1158

class NBytesField(Field[int, List[int]]):
    def __init__(self, name, default, sz):
        # type: (str, Optional[int], int) -> None
        Field.__init__(self, name, default, "<" + "B" * sz)

    def i2m(self, pkt, x):
        # type: (Optional[Packet], Optional[int]) -> List[int]
        if x is None:
            return [0] * self.sz
        x2m = list()
        for _ in range(self.sz):
            x2m.append(x % 256)
            x //= 256
        return x2m[::-1]

    def m2i(self, pkt, x):
        # type: (Optional[Packet], Union[List[int], int]) -> int
        if isinstance(x, int):
            return x
        # x can be a tuple when coming from struct.unpack  (from getfield)
        if isinstance(x, (list, tuple)):
            return sum(d * (256 ** i) for i, d in enumerate(reversed(x)))
        return 0

    def i2repr(self, pkt, x):
        # type: (Optional[Packet], int) -> str
        if isinstance(x, int):
            return '%i' % x
        return super(NBytesField, self).i2repr(pkt, x)

    def addfield(self, pkt, s, val):
        # type: (Optional[Packet], bytes, Optional[int]) -> bytes
        return s + self.struct.pack(*self.i2m(pkt, val))

    def getfield(self, pkt, s):
        # type: (Optional[Packet], bytes) -> Tuple[bytes, int]
        return (s[self.sz:],
                self.m2i(pkt, self.struct.unpack(s[:self.sz])))  # type: ignore

    def randval(self):
        # type: () -> RandNum
        return RandNum(0, 2 ** (self.sz * 8) - 1)


class XNBytesField(NBytesField):