versionutils: add version convert helper methods

Nova[1] and Cinder[2] have same version convert methods. We can
put them in versionutils and make them don't maintain their version.

[1]https://github.com/openstack/nova/blob/master/nova/utils.py#L1044
[2]https://github.com/openstack/cinder/blob/master/cinder/utils.py#L789

Change-Id: I5a7e212bd0d661ce9ec89ae06a9f4c3bc7200d1e

doc/source/api/versionutils.rst

@@ -0,0 +1,6 @@
+==============
+ versionutils
+==============
+
+.. automodule:: oslo_utils.versionutils
+   :members:

doc/source/index.rst

@@ -30,6 +30,7 @@ API Documentation
    api/timeutils
    api/units
    api/uuidutils
+   api/versionutils
 
 Indices and tables
 ==================

oslo_utils/tests/test_versionutils.py

@@ -67,3 +67,19 @@ class IsCompatibleTestCase(test_base.BaseTestCase):
                                                    same_major=False))
         self.assertTrue(versionutils.is_compatible('1.0', '2.0',
                                                    same_major=False))
+
+    def test_convert_version_to_int(self):
+        self.assertEqual(6002000, versionutils.convert_version_to_int('6.2.0'))
+        self.assertEqual(6004003,
+                         versionutils.convert_version_to_int((6, 4, 3)))
+        self.assertEqual(5, versionutils.convert_version_to_int((5, )))
+        self.assertRaises(ValueError,
+                          versionutils.convert_version_to_int, '5a.6b')
+
+    def test_convert_version_to_string(self):
+        self.assertEqual('6.7.0', versionutils.convert_version_to_str(6007000))
+        self.assertEqual('4', versionutils.convert_version_to_str(4))
+
+    def test_convert_version_to_tuple(self):
+        self.assertEqual((6, 7, 0),
+                         versionutils.convert_version_to_tuple('6.7.0'))

oslo_utils/versionutils.py

@@ -19,7 +19,9 @@ Helpers for comparing version strings.
 
 import logging
 
+from oslo_utils._i18n import _
 import pkg_resources
+import six
 
 
 LOG = logging.getLogger(__name__)
@@ -46,3 +48,29 @@ def is_compatible(requested_version, current_version, same_major=True):
         return False
 
     return current_parts >= requested_parts
+
+
+def convert_version_to_int(version):
+    try:
+        if isinstance(version, six.string_types):
+            version = convert_version_to_tuple(version)
+        if isinstance(version, tuple):
+            return six.moves.reduce(lambda x, y: (x * 1000) + y, version)
+    except Exception as ex:
+        msg = _("Version %s is invalid.") % version
+        six.raise_from(ValueError(msg), ex)
+
+
+def convert_version_to_str(version_int):
+    version_numbers = []
+    factor = 1000
+    while version_int != 0:
+        version_number = version_int - (version_int // factor * factor)
+        version_numbers.insert(0, six.text_type(version_number))
+        version_int = version_int // factor
+
+    return '.'.join(map(str, version_numbers))
+
+
+def convert_version_to_tuple(version_str):
+    return tuple(int(part) for part in version_str.split('.'))