| """ |
| Portable file locking utilities. |
| |
| Based partially on example by Jonathan Feignberg <jdf@pobox.com> in the Python |
| Cookbook, licensed under the Python Software License. |
| |
| http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/65203 |
| |
| Example Usage:: |
| |
| >>> from django.core.files import locks |
| >>> f = open('./file', 'wb') |
| >>> locks.lock(f, locks.LOCK_EX) |
| >>> f.write('Django') |
| >>> f.close() |
| """ |
| |
| __all__ = ('LOCK_EX','LOCK_SH','LOCK_NB','lock','unlock') |
| |
| system_type = None |
| |
| try: |
| import win32con |
| import win32file |
| import pywintypes |
| LOCK_EX = win32con.LOCKFILE_EXCLUSIVE_LOCK |
| LOCK_SH = 0 |
| LOCK_NB = win32con.LOCKFILE_FAIL_IMMEDIATELY |
| __overlapped = pywintypes.OVERLAPPED() |
| system_type = 'nt' |
| except (ImportError, AttributeError): |
| pass |
| |
| try: |
| import fcntl |
| LOCK_EX = fcntl.LOCK_EX |
| LOCK_SH = fcntl.LOCK_SH |
| LOCK_NB = fcntl.LOCK_NB |
| system_type = 'posix' |
| except (ImportError, AttributeError): |
| pass |
| |
| def fd(f): |
| """Get a filedescriptor from something which could be a file or an fd.""" |
| return hasattr(f, 'fileno') and f.fileno() or f |
| |
| if system_type == 'nt': |
| def lock(file, flags): |
| hfile = win32file._get_osfhandle(fd(file)) |
| win32file.LockFileEx(hfile, flags, 0, -0x10000, __overlapped) |
| |
| def unlock(file): |
| hfile = win32file._get_osfhandle(fd(file)) |
| win32file.UnlockFileEx(hfile, 0, -0x10000, __overlapped) |
| elif system_type == 'posix': |
| def lock(file, flags): |
| fcntl.lockf(fd(file), flags) |
| |
| def unlock(file): |
| fcntl.lockf(fd(file), fcntl.LOCK_UN) |
| else: |
| # File locking is not supported. |
| LOCK_EX = LOCK_SH = LOCK_NB = None |
| |
| # Dummy functions that don't do anything. |
| def lock(file, flags): |
| pass |
| |
| def unlock(file): |
| pass |