--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/web/lib/django/contrib/sessions/backends/cache.py	Wed Jan 20 00:34:04 2010 +0100
@@ -0,0 +1,56 @@
+from django.contrib.sessions.backends.base import SessionBase, CreateError
+from django.core.cache import cache
+
+class SessionStore(SessionBase):
+    """
+    A cache-based session store.
+    """
+    def __init__(self, session_key=None):
+        self._cache = cache
+        super(SessionStore, self).__init__(session_key)
+
+    def load(self):
+        session_data = self._cache.get(self.session_key)
+        if session_data is not None:
+            return session_data
+        self.create()
+        return {}
+
+    def create(self):
+        # Because a cache can fail silently (e.g. memcache), we don't know if
+        # we are failing to create a new session because of a key collision or
+        # because the cache is missing. So we try for a (large) number of times
+        # and then raise an exception. That's the risk you shoulder if using
+        # cache backing.
+        for i in xrange(10000):
+            self.session_key = self._get_new_session_key()
+            try:
+                self.save(must_create=True)
+            except CreateError:
+                continue
+            self.modified = True
+            return
+        raise RuntimeError("Unable to create a new session key.")
+
+    def save(self, must_create=False):
+        if must_create:
+            func = self._cache.add
+        else:
+            func = self._cache.set
+        result = func(self.session_key, self._get_session(no_load=must_create),
+                self.get_expiry_age())
+        if must_create and not result:
+            raise CreateError
+
+    def exists(self, session_key):
+        if self._cache.has_key(session_key):
+            return True
+        return False
+
+    def delete(self, session_key=None):
+        if session_key is None:
+            if self._session_key is None:
+                return
+            session_key = self._session_key
+        self._cache.delete(session_key)
+