Class HPackStrLenField

scapy/contrib/http2.py:1194–1293

HPackStrLenField is a StrLenField variant specialized for HTTP/2 HPack This variant uses an internal representation that implements HPackStringsInterface. # noqa: E501

class HPackStrLenField(fields.Field):
    """ HPackStrLenField is a StrLenField variant specialized for HTTP/2 HPack

    This variant uses an internal representation that implements HPackStringsInterface.  # noqa: E501
    """
    __slots__ = ['_length_from', '_type_from']

    def __init__(self, name, default, length_from, type_from):
        # type: (str, HPackStringsInterface, Callable[[packet.Packet], int], str) -> None  # noqa: E501
        super(HPackStrLenField, self).__init__(name, default)
        self._length_from = length_from
        self._type_from = type_from

    def addfield(self, pkt, s, val):
        # type: (Optional[packet.Packet], str, HPackStringsInterface) -> str
        return s + self.i2m(pkt, val)

    @staticmethod
    def _parse(t, s):
        # type: (bool, str) -> HPackStringsInterface
        """
        :param bool t: whether this string is a huffman compressed string.
        :param str s: the string to parse.
        :return: HPackStringsInterface: either a HPackLiteralString or HPackZString, depending on t.  # noqa: E501
        :raises: InvalidEncodingException
        """
        if t:
            i, ibl = HPackZString.huffman_conv2bitstring(s)
            return HPackZString(HPackZString.huffman_decode(i, ibl))
        return HPackLiteralString(s)

    def getfield(self, pkt, s):
        # type: (packet.Packet, str) -> Tuple[str, HPackStringsInterface]
        """
        :param packet.Packet pkt: the packet instance containing this field instance.  # noqa: E501
        :param str s: the string to parse this field from.
        :return: (str, HPackStringsInterface): the remaining string after this field was carved out & the extracted  # noqa: E501
          value.
        :raises: KeyError if "type_from" is not a field of pkt or its payloads.
        :raises: InvalidEncodingException
        """
        tmp_len = self._length_from(pkt)
        t = pkt.getfieldval(self._type_from) == 1
        return s[tmp_len:], self._parse(t, s[:tmp_len])

    def i2h(self, pkt, x):
        # type: (Optional[packet.Packet], HPackStringsInterface) -> str
        fmt = ''
        if isinstance(x, HPackLiteralString):
            fmt = "HPackLiteralString({})"
        elif isinstance(x, HPackZString):
            fmt = "HPackZString({})"
        return fmt.format(x.origin())

    def h2i(self, pkt, x):
        # type: (packet.Packet, str) -> HPackStringsInterface
        return HPackLiteralString(x)