utils.py 文件源码

def read_packet(self, size=MTU):
        """return a single packet read from the file

        returns None when no more packets are available
        """
        hdr = self.f.read(16)
        if len(hdr) < 16:
            return None
        sec,usec,caplen,wirelen = struct.unpack(self.endian+"IIII", hdr)
        s = self.f.read(caplen)[:size]
        return s,(sec,usec,wirelen) # caplen = len(s)