1 files changed, 102 insertions, 0 deletions
diff --git a/ryu/services/protocols/bgp/utils/internable.py b/ryu/services/protocols/bgp/utils/internable.py
new file mode 100644
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--- /dev/null
+++ b/ryu/services/protocols/bgp/utils/internable.py
@@ -0,0 +1,102 @@
+# Copyright (C) 2014 Nippon Telegraph and Telephone Corporation.
+#
+# 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.
+
+import weakref
+
+dict_name = intern('_internable_dict')
+
+
+#
+# Internable
+#
+class Internable(object):
+    """Class that allows instances to be 'interned'. That is, given an
+    instance of this class, one can obtain a canonical (interned)
+    copy.
+
+    This saves memory when there are likely to be many identical
+    instances of the class -- users hold references to a single
+    interned object instead of references to different objects that
+    are identical.
+
+    The interned version of a given instance is created on demand if
+    necessary, and automatically cleaned up when nobody holds a
+    reference to it.
+
+    Instances of sub-classes must be usable as dictionary keys for
+    Internable to work.
+    """
+
+    class Stats(object):
+
+        def __init__(self):
+            self.d = {}
+
+        def incr(self, name):
+            self.d[name] = self.d.get(name, 0) + 1
+
+        def __repr__(self):
+            return repr(self.d)
+
+        def __str__(self):
+            return str(self.d)
+
+    @classmethod
+    def _internable_init(kls):
+        # Objects to be interned are held as keys in a dictionary that
+        # only holds weak references to keys. As a result, when the
+        # last reference to an interned object goes away, the object
+        # will be removed from the dictionary.
+        kls._internable_dict = weakref.WeakKeyDictionary()
+        kls._internable_stats = Internable.Stats()
+
+    @classmethod
+    def intern_stats(kls):
+        return kls._internable_stats
+
+    def intern(self):
+        """Returns either itself or a canonical copy of itself."""
+
+        # If this is an interned object, return it
+        if hasattr(self, '_interned'):
+            return self._internable_stats.incr('self')
+
+        #
+        # Got to find or create an interned object identical to this
+        # one. Auto-initialize the class if need be.
+        #
+        kls = self.__class__
+
+        if not hasattr(kls, dict_name):
+            kls._internable_init()
+
+        obj = kls._internable_dict.get(self)
+        if (obj):
+            # Found an interned copy.
+            kls._internable_stats.incr('found')
+            return obj
+
+        # Create an interned copy. Take care to only keep a weak
+        # reference to the object itself.
+        def object_collected(obj):
+            kls._internable_stats.incr('collected')
+            # print("Object %s garbage collected" % obj)
+            pass
+
+        ref = weakref.ref(self, object_collected)
+        kls._internable_dict[self] = ref
+        self._interned = True
+        kls._internable_stats.incr('inserted')
+        return self