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