71 lines
1.7 KiB
Python
71 lines
1.7 KiB
Python
"""
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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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