Moved base backend code

Base class is now abstract using abc.

Change-Id: I6113b50c8f641a043ea149984293b617cbc8adb1

cloudkitty/backend/__init__.py

@@ -0,0 +1,71 @@
+# -*- coding: utf-8 -*-
+# Copyright 2014 Objectif Libre
+#
+#    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.
+#
+# @author: Stéphane Albert
+#
+import abc
+
+import six
+
+
+@six.add_metaclass(abc.ABCMeta)
+class BaseIOBackend(object):
+    def __init__(self, path):
+        self.open(path)
+
+    @abc.abstractmethod
+    def open(self, path):
+        """Open the connection/file on the backend.
+
+        """
+
+    @abc.abstractmethod
+    def tell(self):
+        """Current position on the backend.
+
+        """
+
+    @abc.abstractmethod
+    def seek(self, offset, from_what=0):
+        # 0 beg, 1 cur, 2 end
+        """Change position in the backend
+
+        """
+
+    @abc.abstractmethod
+    def flush(self):
+        """Force write informations on the backend.
+
+        """
+
+    @abc.abstractmethod
+    def write(self, data):
+        """Writer data on the backend.
+
+        :param data: Data to be written on the backend.
+        """
+
+    @abc.abstractmethod
+    def read(self):
+        """Read data from the backend
+
+        :return str: Data read from the backend.
+        """
+
+    @abc.abstractmethod
+    def close(self):
+        """Close the connection/file on the backend.
+
+        """

cloudkitty/backend/base.py

@@ -1,44 +0,0 @@
-# -*- coding: utf-8 -*-
-# Copyright 2014 Objectif Libre
-#
-#    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.
-#
-# @author: Stéphane Albert
-#
-
-
-class BaseIOBackend(object):
-    def __init__(self, path):
-        self.open(path)
-
-    def open(self, path):
-        raise NotImplementedError
-
-    def tell(self):
-        raise NotImplementedError
-
-    def seek(self, offset, from_what=0):
-        # 0 beg, 1 cur, 2 end
-        raise NotImplementedError
-
-    def flush(self):
-        raise NotImplementedError
-
-    def write(self, data):
-        raise NotImplementedError
-
-    def read(self):
-        raise NotImplementedError
-
-    def close(self):
-        raise NotImplementedError