test_socket.py 文件源码

def testCMSG_LEN(self):
        # Test CMSG_LEN() with various valid and invalid values,
        # checking the assumptions used by recvmsg() and sendmsg().
        toobig = self.socklen_t_limit - socket.CMSG_LEN(0) + 1
        values = list(range(257)) + list(range(toobig - 257, toobig))

        # struct cmsghdr has at least three members, two of which are ints
        self.assertGreater(socket.CMSG_LEN(0), array.array("i").itemsize * 2)
        for n in values:
            ret = socket.CMSG_LEN(n)
            # This is how recvmsg() calculates the data size
            self.assertEqual(ret - socket.CMSG_LEN(0), n)
            self.assertLessEqual(ret, self.socklen_t_limit)

        self.assertRaises(OverflowError, socket.CMSG_LEN, -1)
        # sendmsg() shares code with these functions, and requires
        # that it reject values over the limit.
        self.assertRaises(OverflowError, socket.CMSG_LEN, toobig)
        self.assertRaises(OverflowError, socket.CMSG_LEN, sys.maxsize)