utils.py 文件源码

def __call__(cls, filename):
        """Creates a cls instance, use the `alternative` if that
        fails.

        """
        i = cls.__new__(cls, cls.__name__, cls.__bases__, cls.__dict__)
        filename, fdesc, magic = cls.open(filename)
        try:
            i.__init__(filename, fdesc, magic)
        except Scapy_Exception:
            if "alternative" in cls.__dict__:
                cls = cls.__dict__["alternative"]
                i = cls.__new__(cls, cls.__name__, cls.__bases__, cls.__dict__)
                try:
                    i.__init__(filename, fdesc, magic)
                except Scapy_Exception:
                    try:
                        self.f.seek(-4, 1)
                    except:
                        pass
                    raise Scapy_Exception("Not a supported capture file")

        return i