Add a lru cache class

tests/util/test_lrucache.py

@@ -0,0 +1,56 @@
+# -*- coding: utf-8 -*-
+# Copyright 2015 OpenMarket Ltd
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+
+from .. import unittest
+
+from synapse.util.lrucache import LruCache
+
+class LruCacheTestCase(unittest.TestCase):
+
+    def test_get_set(self):
+        cache = LruCache(1)
+        cache["key"] = "value"
+        self.assertEquals(cache.get("key"), "value")
+        self.assertEquals(cache["key"], "value")
+
+    def test_eviction(self):
+        cache = LruCache(2)
+        cache[1] = 1
+        cache[2] = 2
+
+        self.assertEquals(cache.get(1), 1)
+        self.assertEquals(cache.get(2), 2)
+
+        cache[3] = 3
+
+        self.assertEquals(cache.get(1), None)
+        self.assertEquals(cache.get(2), 2)
+        self.assertEquals(cache.get(3), 3)
+
+    def test_setdefault(self):
+        cache = LruCache(1)
+        self.assertEquals(cache.setdefault("key", 1), 1)
+        self.assertEquals(cache.get("key"), 1)
+        self.assertEquals(cache.setdefault("key", 2), 1)
+        self.assertEquals(cache.get("key"), 1)
+
+    def test_pop(self):
+        cache = LruCache(1)
+        cache["key"] = 1
+        self.assertEquals(cache.pop("key"), 1)
+        self.assertEquals(cache.pop("key"), None)
+
+