added LRU caching of skiplist results

[p2pool.git] / p2pool / util / memoize.py

diff --git a/p2pool/util/memoize.py b/p2pool/util/memoize.py
index 5cb07e5..4199ccb 100644 (file)
--- a/p2pool/util/memoize.py
+++ b/p2pool/util/memoize.py
@@ -1,6 +1,24 @@
+import itertools
+
+class LRUDict(object):
+    def __init__(self, n):
+        self.n = n
+        self.inner = {}
+        self.counter = itertools.count()
+    def get(self, key, default=None):
+        if key in self.inner:
+            x, value = self.inner[key]
+            self.inner[key] = self.counter.next(), value
+            return value
+        return default
+    def __setitem__(self, key, value):
+        self.inner[key] = self.counter.next(), value
+        while len(self.inner) > self.n:
+            self.inner.pop(min(self.inner, key=lambda k: self.inner[k][0]))
+
 _nothing = object()
 
-def memoize_with_backing(backing, inverse_of=None):
+def memoize_with_backing(backing, has_inverses=set()):
     def a(f):
         def b(*args):
             res = backing.get((f, args), _nothing)
@@ -10,11 +28,12 @@ def memoize_with_backing(backing, inverse_of=None):
             res = f(*args)
             
             backing[(f, args)] = res
-            if inverse_of is not None:
-                if len(args) != 1:
-                    raise ValueError('inverse_of can only be used for functions taking one argument')
-                backing[(inverse_of, (res,))] = args[0]
+            for inverse in has_inverses:
+                backing[(inverse, args[:-1] + (res,))] = args[-1]
             
             return res
         return b
     return a
+
+def memoize(f):
+    return memoize_with_backing({})(f)