add LRUCache

shadowsocks/lru_cache.py

@@ -0,0 +1,62 @@
+#!/usr/bin/python
+# -*- coding: utf-8 -*-
+
+import collections
+import logging
+import heapq
+import time
+
+
+class LRUCache(collections.MutableMapping):
+    """This class is not thread safe"""
+
+    def __init__(self, timeout=60, *args, **kwargs):
+        self.timeout = timeout
+        self.store = {}
+        self.time_to_keys = collections.defaultdict(list)
+        self.last_visits = []
+        self.update(dict(*args, **kwargs))  # use the free update to set keys
+
+    def __getitem__(self, key):
+        "O(logm)"
+        t = time.time()
+        self.time_to_keys[t].append(key)
+        heapq.heappush(self.last_visits, t)
+        return self.store[key]
+
+    def __setitem__(self, key, value):
+        "O(logm)"
+        t = time.time()
+        self.store[key] = value
+        self.time_to_keys[t].append(key)
+        heapq.heappush(self.last_visits, t)
+
+    def __delitem__(self, key):
+        "O(1)"
+        del self.store[key]
+
+    def __iter__(self):
+        return iter(self.store)
+
+    def __len__(self):
+        return len(self.store)
+
+    def sweep(self):
+        "O(m)"
+        now = time.time()
+        c = 0
+        while len(self.last_visits) > 0:
+            least = self.last_visits[0]
+            if now - least <= self.timeout:
+                break
+            for key in self.time_to_keys[least]:
+                heapq.heappop(self.last_visits)
+                if self.store.__contains__(key):
+                    value = self.store[key]
+                    if hasattr(value, 'close'):
+                        value.close()
+                    del self.store[key]
+                    c += 1
+            del self.time_to_keys[least]
+        if c:
+            logging.debug('%d keys swept' % c)