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class LoopbackFS(fuse.Fuse):

    '''Loopback filesystem with hooks for permission management'''

    def __init__(self, root, *args, **kwargs):

        super(LoopbackFS, self).__init__(*args, **kwargs)

        self._root = root

    @check_and_translate(os.R_OK)

    def getattr(self, path): return os.lstat(path)

    @check_and_translate(os.R_OK)

    def readlink(self, path): return os.readlink(path)

    @check_and_translate(os.W_OK)

    def mknod(self, path, mode, dev): os.mknod(path, mode, dev)

    @check_and_translate(os.W_OK)

    def mkdir(self, path, mode): os.mkdir(path, mode)

    @check_and_translate(os.W_OK)

    def unlink(self, path): os.unlink(path)

    @check_and_translate(None, os.W_OK)

    def symlink(self, target, name): os.symlink(target, name)

    @check_and_translate(os.R_OK|os.W_OK, os.R_OK|os.W_OK)

    def rename(self, old, new): os.rename(old, new)

    @check_and_translate(os.R_OK, os.W_OK)

    def link(self, src, dst): os.link(src, dst)

    @check_and_translate(None)

    def access(self, path, mode): return os.access(path, mode)

    def fsinit(self): pass

    def _to_global(self, path):

        return os.path.join(self._root, path)

    # @check_access(os.R_OK)

    # def readdir(self, path, offset):

    #     for e in os.listdir(self._to_global(path)):

    #         yield fuse.Direntry(e)

    # def rmdir(self, path):

    #     self._assert_access(path, os.W_OK)

    #     os.rmdir(self._to_global(path))

    # def chmod(self, path, mode):

    #     self._assert_access(path, os.W_OK)

    #     os.chmod(self._to_global(path), mode)

    # def chown(self, path, user, group):

    #     self._assert_access(path, os.W_OK)

    #     os.chown(self._to_global(path), user, group)

    # def truncate(self, path, len):

    #     self._assert_access(path, os.W_OK)

    #     f = open(self._to_global(path), "a")

    #     f.truncate(len)

    #     f.close()

    # def utime(self, path, times):

    #     os.utime(self._to_global(path), times)

    # def statfs(self):

    #     """

    #     Should return an object with statvfs attributes (f_bsize, f_frsize...).

    #     Eg., the return value of os.statvfs() is such a thing (since py 2.2).

    #     If you are not reusing an existing statvfs object, start with

    #     fuse.StatVFS(), and define the attributes.

    #     To provide usable information (ie., you want sensible df(1)

    #     output, you are suggested to specify the following attributes:

    #         - f_bsize - preferred size of file blocks, in bytes

    #         - f_frsize - fundamental size of file blcoks, in bytes

    #             [if you have no idea, use the same as blocksize]

    #         - f_blocks - total number of blocks in the filesystem

    #         - f_bfree - number of free blocks

    #         - f_files - total number of file inodes

    #         - f_ffree - nunber of free file inodes

    #     """

    #     return os.statvfs(".")

    # def make_file_class(self):

    #     class FSAccessFile(AccessFile):

    #         filesystem=self

    #     return FSAccessFile

class OverlayFS(fuse.Fuse):

    '''Filesystem that overlays a read-only GridFS on an existing filesystem'''

    def __init__(self, root, gfs, *args, **kwargs):

        super(OverlayFS, self).__init__(*args, **kwargs)

        self._root = root

        self._gfs = gfs