Python fcntl.F_SETLKW Examples

The following are 1 code examples of fcntl.F_SETLKW(). You can vote up the ones you like or vote down the ones you don't like, and go to the original project or source file by following the links above each example. You may also want to check out all available functions/classes of the module fcntl , or try the search function .
Example #1
Source File: accessfs.py    From allura with Apache License 2.0 5 votes vote down vote up 
def lock(self, cmd, owner, **kw):
        # The code here is much rather just a demonstration of the locking
        # API than something which actually was seen to be useful.

        # Advisory file locking is pretty messy in Unix, and the Python
        # interface to this doesn't make it better.
        # We can't do fcntl(2)/F_GETLK from Python in a platfrom independent
        # way. The following implementation *might* work under Linux.
        #
        # if cmd == fcntl.F_GETLK:
        #     import struct
        #
        #     lockdata = struct.pack('hhQQi', kw['l_type'], os.SEEK_SET,
        #                            kw['l_start'], kw['l_len'], kw['l_pid'])
        #     ld2 = fcntl.fcntl(self.fd, fcntl.F_GETLK, lockdata)
        #     flockfields = ('l_type', 'l_whence', 'l_start', 'l_len', 'l_pid')
        #     uld2 = struct.unpack('hhQQi', ld2)
        #     res = {}
        #     for i in xrange(len(uld2)):
        #          res[flockfields[i]] = uld2[i]
        #
        #     return fuse.Flock(**res)

        # Convert fcntl-ish lock parameters to Python's weird
        # lockf(3)/flock(2) medley locking API...
        op = {fcntl.F_UNLCK: fcntl.LOCK_UN,
              fcntl.F_RDLCK: fcntl.LOCK_SH,
              fcntl.F_WRLCK: fcntl.LOCK_EX}[kw['l_type']]
        if cmd == fcntl.F_GETLK:
            return -errno.EOPNOTSUPP
        elif cmd == fcntl.F_SETLK:
            if op != fcntl.LOCK_UN:
                op |= fcntl.LOCK_NB
        elif cmd == fcntl.F_SETLKW:
            pass
        else:
            return -errno.EINVAL

        fcntl.lockf(self.fd, op, kw['l_start'], kw['l_len'])