Move method split_path into oslo.utils

Method split_path was used in project keystonemiddleware, sahara.
So it's good to accept it by oslo.utils.

http://git.openstack.org/cgit/openstack/keystonemiddleware/tree/keystonemiddleware/s3_token.py#n50
http://git.openstack.org/cgit/openstack/sahara/tree/sahara/openstack/commons.py#n24

Change-Id: I8507a7c406d12e459809442601f3ecf919e62311

oslo_utils/strutils.py

@@ -22,6 +22,7 @@ import re
 import unicodedata
 
 import six
+from six.moves import urllib
 
 from oslo_utils._i18n import _
 from oslo_utils import encodeutils
@@ -412,3 +413,52 @@ def check_string_length(value, name=None, min_length=0, max_length=None):
                 "%(max_length)s.") % {'name': name, 'length': length,
                                       'max_length': max_length}
         raise ValueError(msg)
+
+
+def split_path(path, minsegs=1, maxsegs=None, rest_with_last=False):
+    """Validate and split the given HTTP request path.
+
+    **Examples**::
+
+        ['a'] = _split_path('/a')
+        ['a', None] = _split_path('/a', 1, 2)
+        ['a', 'c'] = _split_path('/a/c', 1, 2)
+        ['a', 'c', 'o/r'] = _split_path('/a/c/o/r', 1, 3, True)
+
+    :param path: HTTP Request path to be split
+    :param minsegs: Minimum number of segments to be extracted
+    :param maxsegs: Maximum number of segments to be extracted
+    :param rest_with_last: If True, trailing data will be returned as part
+                           of last segment.  If False, and there is
+                           trailing data, raises ValueError.
+    :returns: list of segments with a length of maxsegs (non-existent
+              segments will return as None)
+    :raises: ValueError if given an invalid path
+
+    .. versionadded:: 3.9
+    """
+    if not maxsegs:
+        maxsegs = minsegs
+    if minsegs > maxsegs:
+        raise ValueError(_('minsegs > maxsegs: %(min)d > %(max)d)') %
+                         {'min': minsegs, 'max': maxsegs})
+    if rest_with_last:
+        segs = path.split('/', maxsegs)
+        minsegs += 1
+        maxsegs += 1
+        count = len(segs)
+        if (segs[0] or count < minsegs or count > maxsegs or
+                '' in segs[1:minsegs]):
+            raise ValueError(_('Invalid path: %s') % urllib.parse.quote(path))
+    else:
+        minsegs += 1
+        maxsegs += 1
+        segs = path.split('/', maxsegs)
+        count = len(segs)
+        if (segs[0] or count < minsegs or count > maxsegs + 1 or
+                '' in segs[1:minsegs] or
+                (count == maxsegs + 1 and segs[maxsegs])):
+            raise ValueError(_('Invalid path: %s') % urllib.parse.quote(path))
+    segs = segs[1:maxsegs]
+    segs.extend([None] * (maxsegs - 1 - len(segs)))
+    return segs

oslo_utils/tests/test_strutils.py

@@ -694,3 +694,42 @@ class StringLengthTestCase(test_base.BaseTestCase):
         self.assertRaises(TypeError,
                           strutils.check_string_length,
                           dict(), max_length=255)
+
+
+class SplitPathTestCase(test_base.BaseTestCase):
+    def test_split_path_failed(self):
+        self.assertRaises(ValueError, strutils.split_path, '')
+        self.assertRaises(ValueError, strutils.split_path, '/')
+        self.assertRaises(ValueError, strutils.split_path, '//')
+        self.assertRaises(ValueError, strutils.split_path, '//a')
+        self.assertRaises(ValueError, strutils.split_path, '/a/c')
+        self.assertRaises(ValueError, strutils.split_path, '//c')
+        self.assertRaises(ValueError, strutils.split_path, '/a/c/')
+        self.assertRaises(ValueError, strutils.split_path, '/a//')
+        self.assertRaises(ValueError, strutils.split_path, '/a', 2)
+        self.assertRaises(ValueError, strutils.split_path, '/a', 2, 3)
+        self.assertRaises(ValueError, strutils.split_path, '/a', 2, 3, True)
+        self.assertRaises(ValueError, strutils.split_path, '/a/c/o/r', 3, 3)
+        self.assertRaises(ValueError, strutils.split_path, '/a', 5, 4)
+
+    def test_split_path_success(self):
+        self.assertEqual(strutils.split_path('/a'), ['a'])
+        self.assertEqual(strutils.split_path('/a/'), ['a'])
+        self.assertEqual(strutils.split_path('/a/c', 2), ['a', 'c'])
+        self.assertEqual(strutils.split_path('/a/c/o', 3), ['a', 'c', 'o'])
+        self.assertEqual(strutils.split_path('/a/c/o/r', 3, 3, True),
+                         ['a', 'c', 'o/r'])
+        self.assertEqual(strutils.split_path('/a/c', 2, 3, True),
+                         ['a', 'c', None])
+        self.assertEqual(strutils.split_path('/a/c/', 2), ['a', 'c'])
+        self.assertEqual(strutils.split_path('/a/c/', 2, 3), ['a', 'c', ''])
+
+    def test_split_path_invalid_path(self):
+        try:
+            strutils.split_path('o\nn e', 2)
+        except ValueError as err:
+            self.assertEqual(str(err), 'Invalid path: o%0An%20e')
+        try:
+            strutils.split_path('o\nn e', 2, 3, True)
+        except ValueError as err:
+            self.assertEqual(str(err), 'Invalid path: o%0An%20e')