1 files changed, 64 insertions, 0 deletions
diff --git a/src/cryptography/utils.py b/src/cryptography/utils.py
new file mode 100644
index 00000000..03c8c0e8
--- /dev/null
+++ b/src/cryptography/utils.py
@@ -0,0 +1,64 @@
+# 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.
+
+from __future__ import absolute_import, division, print_function
+
+import abc
+import inspect
+import sys
+
+
+DeprecatedIn06 = DeprecationWarning
+
+
+def register_interface(iface):
+    def register_decorator(klass):
+        verify_interface(iface, klass)
+        iface.register(klass)
+        return klass
+    return register_decorator
+
+
+def read_only_property(name):
+    return property(lambda self: getattr(self, name))
+
+
+class InterfaceNotImplemented(Exception):
+    pass
+
+
+def verify_interface(iface, klass):
+    for method in iface.__abstractmethods__:
+        if not hasattr(klass, method):
+            raise InterfaceNotImplemented(
+                "{0} is missing a {1!r} method".format(klass, method)
+            )
+        if isinstance(getattr(iface, method), abc.abstractproperty):
+            # Can't properly verify these yet.
+            continue
+        spec = inspect.getargspec(getattr(iface, method))
+        actual = inspect.getargspec(getattr(klass, method))
+        if spec != actual:
+            raise InterfaceNotImplemented(
+                "{0}.{1}'s signature differs from the expected. Expected: "
+                "{2!r}. Received: {3!r}".format(
+                    klass, method, spec, actual
+                )
+            )
+
+
+def bit_length(x):
+    if sys.version_info >= (2, 7):
+        return x.bit_length()
+    else:
+        return len(bin(x)) - (2 + (x <= 0))