Do output as a byproduct of calculating the diff.

This doesn't require keeping the whole diff in memory until the end.

ndiff/ndifftest.py

@@ -274,25 +274,58 @@ class service_test(unittest.TestCase):
         serv.extrainfo = u"misconfigured"
         self.assertEqual(serv.version_string(), u"%s %s (%s)" % (serv.product, serv.version, serv.extrainfo))
 
+class ScanDiffSub(ScanDiff):
+    """A subclass of ScanDiff that counts diffs for testing."""
+    def __init__(self, scan_a, scan_b, f = sys.stdout):
+        ScanDiff.__init__(self, scan_a, scan_b, f)
+        self.pre_script_result_diffs = []
+        self.post_script_result_diffs = []
+        self.host_diffs = []
+
+    def output_beginning(self):
+        pass
+
+    def output_pre_scripts(self, pre_script_result_diffs):
+        self.pre_script_result_diffs = pre_script_result_diffs
+
+    def output_post_scripts(self, post_script_result_diffs):
+        self.post_script_result_diffs = post_script_result_diffs
+
+    def output_host_diff(self, h_diff):
+        self.host_diffs.append(h_diff)
+
+    def output_ending(self):
+        pass
+
 class scan_diff_test(unittest.TestCase):
     """Test the ScanDiff class."""
+    def setUp(self):
+        self.blackhole = open("/dev/null", "w")
+
+    def tearDown(self):
+        self.blackhole.close()
+
     def test_self(self):
         scan = Scan()
         scan.load_from_file("test-scans/complex.xml")
-        diff = ScanDiff(scan, scan)
-        self.assertEqual(len(diff.host_diffs), 0)
-        self.assertEqual(set(diff.hosts), set(diff.host_diffs.keys()))
+        diff = ScanDiffText(scan, scan, self.blackhole)
+        cost = diff.output()
+        self.assertEqual(cost, 0)
+        diff = ScanDiffXML(scan, scan, self.blackhole)
+        cost = diff.output()
+        self.assertEqual(cost, 0)
 
     def test_unknown_up(self):
         a = Scan()
         a.load_from_file("test-scans/empty.xml")
         b = Scan()
         b.load_from_file("test-scans/simple.xml")
-        diff = ScanDiff(a, b)
-        self.assertTrue(len(diff.hosts) >= 1)
+        diff = ScanDiffSub(a, b, self.blackhole)
+        diff.output()
+        self.assertEqual(len(diff.pre_script_result_diffs), 0)
+        self.assertEqual(len(diff.post_script_result_diffs), 0)
         self.assertEqual(len(diff.host_diffs), 1)
-        self.assertEqual(set(diff.hosts), set(diff.host_diffs.keys()))
-        h_diff = diff.host_diffs.values()[0]
+        h_diff = diff.host_diffs[0]
         self.assertEqual(h_diff.host_a.state, None)
         self.assertEqual(h_diff.host_b.state, "up")
 
@@ -301,11 +334,12 @@ class scan_diff_test(unittest.TestCase):
         a.load_from_file("test-scans/simple.xml")
         b = Scan()
         b.load_from_file("test-scans/empty.xml")
-        diff = ScanDiff(a, b)
-        self.assertTrue(len(diff.hosts) >= 1)
+        diff = ScanDiffSub(a, b, self.blackhole)
+        diff.output()
+        self.assertEqual(len(diff.pre_script_result_diffs), 0)
+        self.assertEqual(len(diff.post_script_result_diffs), 0)
         self.assertEqual(len(diff.host_diffs), 1)
-        self.assertEqual(set(diff.hosts), set(diff.host_diffs.keys()))
-        h_diff = diff.host_diffs.values()[0]
+        h_diff = diff.host_diffs[0]
         self.assertEqual(h_diff.host_a.state, "up")
         self.assertEqual(h_diff.host_b.state, None)
 
@@ -327,11 +361,10 @@ class scan_diff_test(unittest.TestCase):
             a.load_from_file("test-scans/%s.xml" % pair[0])
             b = Scan()
             b.load_from_file("test-scans/%s.xml" % pair[1])
-            diff = ScanDiff(a, b)
+            diff = ScanDiffSub(a, b)
             scan_apply_diff(a, diff)
-            diff = ScanDiff(a, b)
-            self.assertEqual(diff.host_diffs, {})
-            self.assertEqual(set(diff.hosts), set(diff.host_diffs.keys()))
+            diff = ScanDiffSub(a, b)
+            self.assertEqual(diff.host_diffs, [])
 
 class host_diff_test(unittest.TestCase):
     """Test the HostDiff class."""
@@ -641,9 +674,9 @@ class scan_diff_xml_test(unittest.TestCase):
         a.load_from_file("test-scans/empty.xml")
         b = Scan()
         b.load_from_file("test-scans/simple.xml")
-        self.scan_diff = ScanDiff(a, b)
         f = StringIO.StringIO()
-        self.scan_diff.print_xml(f)
+        self.scan_diff = ScanDiffXML(a, b, f)
+        self.scan_diff.output()
         self.xml = f.getvalue()
         f.close()
 
@@ -655,10 +688,11 @@ class scan_diff_xml_test(unittest.TestCase):
 
 def scan_apply_diff(scan, diff):
     """Apply a scan diff to the given scan."""
-    for host in diff.hosts:
+    for h_diff in diff.host_diffs:
+        host = h_diff.host_a or h_diff.host_b
         if host not in scan.hosts:
             scan.hosts.append(host)
-        host_apply_diff(host, diff.host_diffs[host])
+        host_apply_diff(host, h_diff)
 
 def host_apply_diff(host, diff):
     """Apply a host diff to the given host."""