cache MIB columnar objects instance ID <-> symbolic representation mapping

for performance reasons

1 files changed, 37 insertions, 0 deletions

diff --git a/pysnmp/cache.py b/pysnmp/cache.py
new file mode 100644
index 00000000..4023c460
--- /dev/null
+++ b/pysnmp/cache.py
@@ -0,0 +1,37 @@
+# Limited-size dictionary class to use for caches
+
+class Cache:
+    def __init__(self, maxSize=256):
+        self.__maxSize = maxSize
+        self.__size = 0
+        self.__chopSize = maxSize/10
+        self.__chopSize = self.__chopSize and self.__chopSize or 1
+        self.__cache = {}
+        self.__usage = {}
+
+    def __contains__(self, k): return k in self.__cache
+
+    def __getitem__(self, k):
+        self.__usage[k] = self.__usage[k] + 1
+        return self.__cache[k]
+
+    def __len__(self): return self.__size
+        
+    def __setitem__(self, k, v):
+        if self.__size >= self.__maxSize:
+            keys = self.__usage.keys()
+            keys.sort(lambda x,y,d=self.__usage: cmp(d[x],d[y]))
+            print keys[:self.__chopSize]
+            for _k in keys[:self.__chopSize]:
+                del self.__cache[_k]
+                del self.__usage[_k]
+            self.__size = self.__size - self.__chopSize
+        if k not in self.__cache:
+            self.__size = self.__size + 1
+            self.__usage[k] = 0L
+        self.__cache[k] = v
+
+    def __delitem__(self, k):
+        del self.__cache[k]
+        del self.__usage[k]
+        self.__size = self.__size - 1