Let's take a look at the Scapy code. Overload of special methods __div__, __getitem__ and so on.

Purpose

I have a little errand, for example, what does the Scapy code look like? What is Scapy? Scapy is a powerful Python-based interactive packet manipulation program and library. (Quote: https://pypi.org/project/scapy/)

Python layman? (I'm not familiar with it), but it was a pretty difficult code for me.

First, ** around the overload of special methods, the code I don't understand **, so I'll make a note of this article.

What I found

All quote codes are https://github.com/secdev/scapy From.

\ _ \ _ Div \ _ \ _ overload

How to use:

    a = IP(dst=dest) / TCP(flags="S", seq=i, sport=65000, dport=55556)
    b = IP(dst=dest)/ICMP()

Action: ** Attach objects with "/". ** **

It is overloaded with code that looks like this:

    def __div__(self, other):
        if isinstance(other, Packet):
            cloneA = self.copy()
            cloneB = other.copy()
            cloneA.add_payload(cloneB)
            return cloneA
        elif isinstance(other, (bytes, str)):
            return self / conf.raw_layer(load=other)
        else:
            return other.__rdiv__(self)

Overload of \ _ \ _ getitem \ _ \ _

How to use:

        seq = pkt[TCP].seq

Action: ** [] to take out a part. ** **

It is overloaded with code that looks like this:

    def __getitem__(self, cls):
        if isinstance(cls, slice):
            lname = cls.start
            if cls.stop:
                ret = self.getlayer(cls.start, nb=cls.stop, **(cls.step or {}))
            else:
                ret = self.getlayer(cls.start, **(cls.step or {}))
        else:
            lname = cls
            ret = self.getlayer(cls)
        if ret is None:
            if isinstance(lname, Packet_metaclass):
                lname = lname.__name__
            elif not isinstance(lname, bytes):
                lname = repr(lname)
            raise IndexError("Layer [%s] not found" % lname)
        return ret

Summary

The above overload looks useful, so it may be used in other modules as well. Information that may be useful is below.

If you have any comments, please let us know. : candy: There may be a lot of this kind of processing in other languages as well. .. I'm a little confused when the basic symbols (operators) are overloaded for me, who only knows about C.

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