def robotsrulesetOfDomain(self, domain):
		'''检查domain是否在数据库中,
			否 --> (False, None)
			是 --> (True, 数据库中存储的robots.txt内容)
		'''
		exist = False
		cur = self.conn.cursor()
		# 是否存在
		cur.execute("SELECT 1 FROM Domains WHERE domain=?", (domain,))
		if cur.fetchone() :
			exist = True
		# 存在的话,结果是什么
		cur.execute("SELECT rules FROM Domains,Rulesets "
			"WHERE domain=? AND Domains.did=Rulesets.did"
			,(domain,) )
		ruleset = cur.fetchone()
		return (exist, ruleset)
def test_struct_alignment(self):
        class X(Structure):
            _fields_ = [("x", c_char * 3)]
        self.assertEqual(alignment(X), calcsize("s"))
        self.assertEqual(sizeof(X), calcsize("3s"))

        class Y(Structure):
            _fields_ = [("x", c_char * 3),
                        ("y", c_int)]
        self.assertEqual(alignment(Y), calcsize("i"))
        self.assertEqual(sizeof(Y), calcsize("3si"))

        class SI(Structure):
            _fields_ = [("a", X),
                        ("b", Y)]
        self.assertEqual(alignment(SI), max(alignment(Y), alignment(X)))
        self.assertEqual(sizeof(SI), calcsize("3s0i 3si 0i"))

        class IS(Structure):
            _fields_ = [("b", Y),
                        ("a", X)]

        self.assertEqual(alignment(SI), max(alignment(X), alignment(Y)))
        self.assertEqual(sizeof(IS), calcsize("3si 3s 0i"))

        class XX(Structure):
            _fields_ = [("a", X),
                        ("b", X)]
        self.assertEqual(alignment(XX), alignment(X))
        self.assertEqual(sizeof(XX), calcsize("3s 3s 0s"))