app/django/core/files/locks.py
author Sverre Rabbelier <srabbelier@gmail.com>
Sun, 01 Feb 2009 22:48:48 +0000
changeset 1166 558bd62ee9d4
parent 323 ff1a9aa48cfd
permissions -rw-r--r--
Fix get args construction when there are multiple lists on the page It is now possible to go back and forward through the liast, and specify the limit (both offset and limit can be done per list). The JS driving the list boxes is buggy, if visiting an url like: http://localhost:8080/notification/list?limit_0=10 And then change the limit in the second checkbox, it directs to: http://localhost:8080/notification/list?limit_1=25 Whereas it should redirect to: http://localhost:8080/notification/list?limit_0=10&limit_1=25 The logic _does_ work properly when the limit of the changed list is already present in the url. Patch by: Sverre Rabbelier

"""
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