re-implement thread safe fnmatch

fnmatch is not thread safe for versions <= 2.7.9. We have used
it in some projects without any lock for concurrency scenario. This patch
re-implements a thread safe fnmatch which is very similar to standard
nmatch.

Change-Id: I610ffcdf58d1590b8e0c0faefd8832563b33ab30
ref: https://bugs.python.org/issue23191

2 files changed, 106 insertions, 0 deletions

diff --git a/oslo_utils/fnmatch.py b/oslo_utils/fnmatch.py
new file mode 100644
index 0000000..8dd7aa0
--- /dev/null
+++ b/oslo_utils/fnmatch.py
@@ -0,0 +1,76 @@
+# 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.
+
+"""Thread safe fnmatch re-implementation.
+
+Standard library fnmatch in Python versions <= 2.7.9 has thread safe
+issue, this module is created for such case. see:
+https://bugs.python.org/issue23191
+"""
+
+from __future__ import absolute_import
+
+import fnmatch as standard_fnmatch
+import os
+import posixpath
+import re
+import sys
+
+
+if sys.version_info > (2, 7, 9):
+    fnmatch = standard_fnmatch.fnmatch
+    fnmatchcase = standard_fnmatch.fnmatchcase
+    filter = standard_fnmatch.filter
+    translate = standard_fnmatch.translate
+else:
+    _MATCH_CACHE = {}
+    _MATCH_CACHE_MAX = 100
+
+    translate = standard_fnmatch.translate
+
+    def _get_cached_pattern(pattern):
+        cached_pattern = _MATCH_CACHE.get(pattern)
+        if cached_pattern is None:
+            translated_pattern = translate(pattern)
+            cached_pattern = re.compile(translated_pattern)
+            if len(_MATCH_CACHE) >= _MATCH_CACHE_MAX:
+                _MATCH_CACHE.clear()
+            _MATCH_CACHE[pattern] = cached_pattern
+        return cached_pattern
+
+    def fnmatchcase(filename, pattern):
+        cached_pattern = _get_cached_pattern(pattern)
+        return cached_pattern.match(filename) is not None
+
+    def fnmatch(filename, pattern):
+        filename = os.path.normcase(filename)
+        pattern = os.path.normcase(pattern)
+        return fnmatchcase(filename, pattern)
+
+    def filter(filenames, pattern):
+        filtered_filenames = []
+
+        pattern = os.path.normcase(pattern)
+        cached_pattern = _get_cached_pattern(pattern)
+
+        if os.path is posixpath:
+            # normcase on posix is NOP. Optimize it away from the loop.
+            for filename in filenames:
+                if cached_pattern.match(filename):
+                    filtered_filenames.append(filename)
+        else:
+            for filename in filenames:
+                filename = os.path.normcase(filename)
+                if cached_pattern.match(filename):
+                    filtered_filenames.append(filename)
+
+        return filtered_filenames
diff --git a/oslo_utils/tests/test_fnmatch.py b/oslo_utils/tests/test_fnmatch.py
new file mode 100644
index 0000000..537d72a
--- /dev/null
+++ b/oslo_utils/tests/test_fnmatch.py
@@ -0,0 +1,30 @@
+# 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.
+
+import sys
+
+import mock
+from oslotest import base
+
+from oslo_utils import fnmatch
+
+
+class TestFnmatch(base.BaseTestCase):
+
+    @mock.patch.object(sys, 'version_info', new=(2, 7, 0))
+    def test_fnmatch(self):
+        self.assertFalse(fnmatch.fnmatch("tesX", "Test"))
+        self.assertTrue(fnmatch.fnmatch("test", "test"))
+        self.assertFalse(fnmatch.fnmatchcase("test", "Test"))
+        self.assertTrue(fnmatch.fnmatchcase("test", "test"))
+        self.assertTrue(fnmatch.fnmatch("testX", "test*"))
+        self.assertEqual(["test"], fnmatch.filter(["test", "testX"], "test"))