1 files changed, 81 insertions, 0 deletions
diff --git a/oauth2client/contrib/_fcntl_opener.py b/oauth2client/contrib/_fcntl_opener.py
new file mode 100644
index 0000000..ae6c85b
--- /dev/null
+++ b/oauth2client/contrib/_fcntl_opener.py
@@ -0,0 +1,81 @@
+# Copyright 2016 Google Inc. All rights reserved.
+#
+# 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 errno
+import fcntl
+import time
+
+from oauth2client.contrib import locked_file
+
+
+class _FcntlOpener(locked_file._Opener):
+    """Open, lock, and unlock a file using fcntl.lockf."""
+
+    def open_and_lock(self, timeout, delay):
+        """Open the file and lock it.
+
+        Args:
+            timeout: float, How long to try to lock for.
+            delay: float, How long to wait between retries
+
+        Raises:
+            AlreadyLockedException: if the lock is already acquired.
+            IOError: if the open fails.
+            CredentialsFileSymbolicLinkError: if the file is a symbolic
+                                              link.
+        """
+        if self._locked:
+            raise locked_file.AlreadyLockedException(
+                'File {0} is already locked'.format(self._filename))
+        start_time = time.time()
+
+        locked_file.validate_file(self._filename)
+        try:
+            self._fh = open(self._filename, self._mode)
+        except IOError as e:
+            # If we can't access with _mode, try _fallback_mode and
+            # don't lock.
+            if e.errno in (errno.EPERM, errno.EACCES):
+                self._fh = open(self._filename, self._fallback_mode)
+                return
+
+        # We opened in _mode, try to lock the file.
+        while True:
+            try:
+                fcntl.lockf(self._fh.fileno(), fcntl.LOCK_EX)
+                self._locked = True
+                return
+            except IOError as e:
+                # If not retrying, then just pass on the error.
+                if timeout == 0:
+                    raise
+                if e.errno != errno.EACCES:
+                    raise
+                # We could not acquire the lock. Try again.
+                if (time.time() - start_time) >= timeout:
+                    locked_file.logger.warn('Could not lock %s in %s seconds',
+                                            self._filename, timeout)
+                    if self._fh:
+                        self._fh.close()
+                    self._fh = open(self._filename, self._fallback_mode)
+                    return
+                time.sleep(delay)
+
+    def unlock_and_close(self):
+        """Close and unlock the file using the fcntl.lockf primitive."""
+        if self._locked:
+            fcntl.lockf(self._fh.fileno(), fcntl.LOCK_UN)
+        self._locked = False
+        if self._fh:
+            self._fh.close()