Class PadField

scapy/fields.py:625–658

Add bytes after the proxified field so that it ends at the specified alignment from its beginning

class PadField(_FieldContainer):
    """Add bytes after the proxified field so that it ends at the specified
       alignment from its beginning"""
    __slots__ = ["fld", "_align", "_padwith"]

    def __init__(self, fld, align, padwith=None):
        # type: (AnyField, int, Optional[bytes]) -> None
        self.fld = fld
        self._align = align
        self._padwith = padwith or b"\x00"

    def padlen(self, flen, pkt):
        # type: (int, Packet) -> int
        return -flen % self._align

    def getfield(self,
                 pkt,  # type: Packet
                 s,  # type: bytes
                 ):
        # type: (...) -> Tuple[bytes, Any]
        remain, val = self.fld.getfield(pkt, s)
        padlen = self.padlen(len(s) - len(remain), pkt)
        return remain[padlen:], val

    def addfield(self,
                 pkt,  # type: Packet
                 s,  # type: bytes
                 val,  # type: Any
                 ):
        # type: (...) -> bytes
        sval = self.fld.addfield(pkt, b"", val)
        return s + sval + (
            self.padlen(len(sval), pkt) * self._padwith
        )


class ReversePadField(PadField):