| # 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 time |
| |
| import pywintypes |
| import win32con |
| import win32file |
| |
| from oauth2client.contrib import locked_file |
| |
| |
| class _Win32Opener(locked_file._Opener): |
| """Open, lock, and unlock a file using windows primitives.""" |
| |
| # Error #33: |
| # 'The process cannot access the file because another process' |
| FILE_IN_USE_ERROR = 33 |
| |
| # Error #158: |
| # 'The segment is already unlocked.' |
| FILE_ALREADY_UNLOCKED_ERROR = 158 |
| |
| 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 == errno.EACCES: |
| self._fh = open(self._filename, self._fallback_mode) |
| return |
| |
| # We opened in _mode, try to lock the file. |
| while True: |
| try: |
| hfile = win32file._get_osfhandle(self._fh.fileno()) |
| win32file.LockFileEx( |
| hfile, |
| (win32con.LOCKFILE_FAIL_IMMEDIATELY | |
| win32con.LOCKFILE_EXCLUSIVE_LOCK), 0, -0x10000, |
| pywintypes.OVERLAPPED()) |
| self._locked = True |
| return |
| except pywintypes.error as e: |
| if timeout == 0: |
| raise |
| |
| # If the error is not that the file is already |
| # in use, raise. |
| if e[0] != _Win32Opener.FILE_IN_USE_ERROR: |
| 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 win32 primitive.""" |
| if self._locked: |
| try: |
| hfile = win32file._get_osfhandle(self._fh.fileno()) |
| win32file.UnlockFileEx(hfile, 0, -0x10000, |
| pywintypes.OVERLAPPED()) |
| except pywintypes.error as e: |
| if e[0] != _Win32Opener.FILE_ALREADY_UNLOCKED_ERROR: |
| raise |
| self._locked = False |
| if self._fh: |
| self._fh.close() |