trackdb: Give TrackAllocators a len() function

Signed-off-by: Anna Schumaker <Anna@NoWheyCreamery.com>

trackdb/allocator.py

@@ -28,6 +28,10 @@ class TrackAllocator:
             return { "tracks" : self.tracks,
                      "nextid" : self.nextid }
 
+    def __len__(self):
+        with self.lock:
+            return len(self.tracks)
+
     def __setstate__(self, state):
         self.__dict__.update(state)
         self.lock = threading.Lock()

trackdb/test_allocator.py

@@ -36,6 +36,7 @@ class TestTrackAllocator(unittest.TestCase):
         track = alloc.allocate(lib, test_tracks / "01 - Test Track.ogg")
         self.assertEqual(alloc.tracks[0], track)
         self.assertEqual(alloc[0], track)
+        self.assertEqual(len(alloc), 1)
         self.assertEqual(alloc.nextid, 1)
         self.assertEqual(track.trackid, 0)
         self.assertEqual(self.added, track)
@@ -43,6 +44,7 @@ class TestTrackAllocator(unittest.TestCase):
         track2 = alloc.allocate(lib, test_tracks / "02 - Test {Disc 2}.ogg")
         self.assertEqual(alloc.tracks[1], track2)
         self.assertEqual(alloc[1], track2)
+        self.assertEqual(len(alloc), 2)
 
         self.assertIsNone(alloc.allocate(lib, test_tracks / "No Such File"))
         self.assertEqual(self.added, track2)