loopback.py

#!/usr/bin/env python
"""A simple FUSE filesystem which just mirrors a given directory."""

import errno
import os
import os.path
import threading

import fuse


class Loopback(fuse.Operations):
    """A simple FUSE-py class for doing a loopback FS."""
    def __init__(self, root):
        self.root = os.path.realpath(root)
        self.rwlock = threading.Lock()

    def __call__(self, op, path, *args):
        return super(Loopback, self).__call__(op, self.root + path, *args)

    def access(self, path, mode):
        if not os.access(path, mode):
            raise fuse.FuseOSError(errno.EACCES)

    chmod = os.chmod
    chown = os.chown

    def create(self, path, mode):
        return os.open(path, os.O_WRONLY | os.O_CREAT, mode)

    def flush(self, path, fh):
        return os.fsync(fh)

    def fsync(self, path, datasync, fh):
        return os.fsync(fh)

    def getattr(self, path, fh=None):
        st = os.lstat(path)
        keys = (
            'st_atime',
            'st_ctime',
            'st_gid',
            'st_mode',
            'st_mtime',
            'st_nlink',
            'st_size',
            'st_uid',
        )
        return dict((key, getattr(st, key)) for key in keys)

    getxattr = None

    def link(self, target, source):
        return os.link(source, target)

    listxattr = None
    mkdir = os.mkdir
    mknod = os.mknod
    open = os.open

    def read(self, path, size, offset, fh):
        with self.rwlock:
            os.lseek(fh, offset, 0)
            return os.read(fh, size)

    def readdir(self, path, fh):
        return ['.', '..'] + os.listdir(path)

    readlink = os.readlink

    def release(self, path, fh):
        return os.close(fh)

    def rename(self, old, new):
        return os.rename(old, self.root + new)

    rmdir = os.rmdir

    def statfs(self, path):
        stv = os.statvfs(path)
        keys = (
            'f_bavail',
            'f_bfree',
            'f_blocks',
            'f_bsize',
            'f_favail',
            'f_ffree',
            'f_files',
            'f_flag',
            'f_frsize',
            'f_namemax',
        )
        return dict((key, getattr(stv, key)) for key in keys)

    def symlink(self, target, source):
        return os.symlink(source, target)

    def truncate(self, path, length, fh=None):
        with open(path, 'r+') as f:
            f.truncate(length)

    unlink = os.unlink
    utimens = os.utime

    def write(self, path, data, offset, fh):
        with self.rwlock:
            os.lseek(fh, offset, 0)
            return os.write(fh, data)