app/django/core/files/locks.py
author Sverre Rabbelier <srabbelier@gmail.com>
Fri, 23 Jan 2009 21:20:33 +0000
changeset 935 09f47e08f805
parent 323 ff1a9aa48cfd
permissions -rw-r--r--
Adust the as_table tag to render a pick link if appropriate The templates are adjusted to pass on a 'reference' value, which is the url_name of the view from which the entity should be picked. The as_table (and related) function(s) construct and then pass on this argument and enable takes_contex so that we have access to the context of the enclosing template. We only extract ReferenceProperties that end with '_link_id' since that is how all RP's are currently named. It is not possible to create a field with the same name as the RP, as GAE will try to interpret it's contents as the key of an entity before even calling any function we can override. 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