Add method validate_integer

Method validate_integer() is used in Cinder[1], Nova[2] and
Masakari[3].
So it's a good candidate to add this method in Oslo.utils.

[1] https://github.com/openstack/cinder/blob/master/cinder/utils.py#L1032
[2] https://github.com/openstack/nova/blob/master/nova/utils.py#L846
[3] https://github.com/openstack/masakari/blob/master/masakari/utils.py#L244

Change-Id: I9086b9057e24aa4747a81507ab14aad60e39ab40

oslo_utils/strutils.py

@@ -438,6 +438,35 @@ def check_string_length(value, name=None, min_length=0, max_length=None):
         raise ValueError(msg)
 
 
+def validate_integer(value, name, min_value=None, max_value=None):
+    """Make sure that value is a valid integer, potentially within range.
+
+    :param value: value of the integer
+    :param name: name of the integer
+    :param min_value: min_value of the integer
+    :param max_value: max_value of the integer
+    :returns: integer
+    """
+    try:
+        value = int(str(value))
+    except (ValueError, UnicodeEncodeError):
+        msg = _('%(value_name)s must be an integer'
+                ) % {'value_name': name}
+        raise ValueError(msg)
+
+    if min_value is not None and value < min_value:
+        msg = _('%(value_name)s must be >= %(min_value)d'
+                ) % {'value_name': name, 'min_value': min_value}
+        raise ValueError(msg)
+
+    if max_value is not None and value > max_value:
+        msg = _('%(value_name)s must be <= %(max_value)d'
+                ) % {'value_name': name, 'max_value': max_value}
+        raise ValueError(msg)
+
+    return value
+
+
 def split_path(path, minsegs=1, maxsegs=None, rest_with_last=False):
     """Validate and split the given HTTP request path.
 

oslo_utils/tests/test_strutils.py

@@ -18,6 +18,7 @@
 import copy
 import math
 
+import ddt
 import mock
 from oslotest import base as test_base
 import six
@@ -804,3 +805,35 @@ class SplitByCommas(test_base.BaseTestCase):
 
     def test_with_escaped_quotes_in_row_inside_quoted(self):
         self.check(['a"b""c', 'd'], r'"a\"b\"\"c",d')
+
+
+@ddt.ddt
+class ValidateIntegerTestCase(test_base.BaseTestCase):
+
+    @ddt.unpack
+    @ddt.data({"value": 42, "name": "answer", "output": 42},
+              {"value": "42", "name": "answer", "output": 42},
+              {"value": "7", "name": "lucky", "output": 7,
+               "min_value": 7, "max_value": 8},
+              {"value": 7, "name": "lucky", "output": 7,
+               "min_value": 6, "max_value": 7},
+              {"value": 300, "name": "Spartaaa!!!", "output": 300,
+               "min_value": 300},
+              {"value": "300", "name": "Spartaaa!!!", "output": 300,
+               "max_value": 300})
+    def test_valid_inputs(self, output, value, name, **kwargs):
+        self.assertEqual(strutils.validate_integer(value, name,
+                                                   **kwargs), output)
+
+    @ddt.unpack
+    @ddt.data({"value": "im-not-an-int", "name": ''},
+              {"value": 3.14, "name": "Pie"},
+              {"value": "299", "name": "Sparta no-show",
+               "min_value": 300, "max_value": 300},
+              {"value": 55, "name": "doing 55 in a 54",
+               "max_value": 54},
+              {"value": six.unichr(129), "name": "UnicodeError",
+               "max_value": 1000})
+    def test_invalid_inputs(self, value, name, **kwargs):
+        self.assertRaises(ValueError, strutils.validate_integer,
+                          value, name, **kwargs)

test-requirements.txt

@@ -10,6 +10,7 @@ testrepository>=0.0.18 # Apache-2.0/BSD
 testscenarios>=0.4 # Apache-2.0/BSD
 testtools>=1.4.0 # MIT
 oslotest>=1.10.0 # Apache-2.0
+ddt>=1.0.1 # MIT
 
 # when we can require tox>= 1.4, this can go into tox.ini:
 #  [testenv:cover]