1 files changed, 46 insertions, 1 deletions
diff --git a/keystone-moon/keystone/common/driver_hints.py b/keystone-moon/keystone/common/driver_hints.py
index ff0a774c..e7c2f2ef 100644
--- a/keystone-moon/keystone/common/driver_hints.py
+++ b/keystone-moon/keystone/common/driver_hints.py
@@ -13,6 +13,50 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
+import functools
+
+from keystone import exception
+from keystone.i18n import _
+
+
+def truncated(f):
+    """Ensure list truncation is detected in Driver list entity methods.
+
+    This is designed to wrap Driver list_{entity} methods in order to
+    calculate if the resultant list has been truncated. Provided a limit dict
+    is found in the hints list, we increment the limit by one so as to ask the
+    wrapped function for one more entity than the limit, and then once the list
+    has been generated, we check to see if the original limit has been
+    exceeded, in which case we truncate back to that limit and set the
+    'truncated' boolean to 'true' in the hints limit dict.
+
+    """
+    @functools.wraps(f)
+    def wrapper(self, hints, *args, **kwargs):
+        if not hasattr(hints, 'limit'):
+            raise exception.UnexpectedError(
+                _('Cannot truncate a driver call without hints list as '
+                  'first parameter after self '))
+
+        if hints.limit is None:
+            return f(self, hints, *args, **kwargs)
+
+        # A limit is set, so ask for one more entry than we need
+        list_limit = hints.limit['limit']
+        hints.set_limit(list_limit + 1)
+        ref_list = f(self, hints, *args, **kwargs)
+
+        # If we got more than the original limit then trim back the list and
+        # mark it truncated.  In both cases, make sure we set the limit back
+        # to its original value.
+        if len(ref_list) > list_limit:
+            hints.set_limit(list_limit, truncated=True)
+            return ref_list[:list_limit]
+        else:
+            hints.set_limit(list_limit)
+            return ref_list
+    return wrapper
+
 
 class Hints(object):
     """Encapsulate driver hints for listing entities.
@@ -39,12 +83,13 @@ class Hints(object):
     * ``name``: the name of the attribute being matched
     * ``value``: the value against which it is being matched
     * ``comparator``: the operation, which can be one of ``equals``,
-                      ``startswith`` or ``endswith``
+                      ``contains``, ``startswith`` or ``endswith``
     * ``case_sensitive``: whether any comparison should take account of
                           case
     * ``type``: will always be 'filter'
 
     """
+
     def __init__(self):
         self.limit = None
         self.filters = list()