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# Example File Systems

Python-LLFUSE comes with several example file systems in the `examples` directory of the release tarball. For completeness, these examples are also included here.

## Single-file, Read-only File System

(shipped as `examples/lltest.py`)

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    #!/usr/bin/env python3
    # -*- coding: utf-8 -*-
    '''
    lltest.py - Example file system for Python-LLFUSE.

    This program presents a static file system containing a single file. It is
    compatible with both Python 2.x and 3.x. Based on an example from Gerion Entrup.

    Copyright © 2015 Nikolaus Rath <Nikolaus.org>
    Copyright © 2015 Gerion Entrup.

    Permission is hereby granted, free of charge, to any person obtaining a copy of
    this software and associated documentation files (the "Software"), to deal in
    the Software without restriction, including without limitation the rights to
    use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
    the Software, and to permit persons to whom the Software is furnished to do so.

    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
    FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
    COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
    IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
    CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
    '''

    from __future__ import division, print_function, absolute_import

    import os
    import sys

    # We are running from the Python-LLFUSE source directory, put it
    # into the Python path.
    basedir = os.path.abspath(os.path.join(os.path.dirname(sys.argv[0]), '..'))
    if (os.path.exists(os.path.join(basedir, 'setup.py')) and
        os.path.exists(os.path.join(basedir, 'src', 'llfuse'))):
        sys.path.append(os.path.join(basedir, 'src'))

    from argparse import ArgumentParser
    import stat
    import logging
    import errno
    import llfuse

    try:
        import faulthandler
    except ImportError:
        pass
    else:
        faulthandler.enable()

    log = logging.getLogger(__name__)

    class TestFs(llfuse.Operations):
        def __init__(self):
            super(TestFs, self).__init__()
            self.hello_name = b"message"
            self.hello_inode = llfuse.ROOT_INODE+1
            self.hello_data = b"hello world\n"

        def getattr(self, inode, ctx=None):
            entry = llfuse.EntryAttributes()
            if inode == llfuse.ROOT_INODE:
                entry.st_mode = (stat.S_IFDIR | 0o755)
                entry.st_size = 0
            elif inode == self.hello_inode:
                entry.st_mode = (stat.S_IFREG | 0o644)
                entry.st_size = len(self.hello_data)
            else:
                raise llfuse.FUSEError(errno.ENOENT)

            stamp = int(1438467123.985654 * 1e9)
            entry.st_atime_ns = stamp
            entry.st_ctime_ns = stamp
            entry.st_mtime_ns = stamp
            entry.st_gid = os.getgid()
            entry.st_uid = os.getuid()
            entry.st_ino = inode

            return entry

        def lookup(self, parent_inode, name, ctx=None):
            if parent_inode != llfuse.ROOT_INODE or name != self.hello_name:
                raise llfuse.FUSEError(errno.ENOENT)
            return self.getattr(self.hello_inode)

        def opendir(self, inode, ctx):
            if inode != llfuse.ROOT_INODE:
                raise llfuse.FUSEError(errno.ENOENT)
            return inode

        def readdir(self, fh, off):
            assert fh == llfuse.ROOT_INODE

            # only one entry
            if off == 0:
                yield (self.hello_name, self.getattr(self.hello_inode), 1)

        def open(self, inode, flags, ctx):
            if inode != self.hello_inode:
                raise llfuse.FUSEError(errno.ENOENT)
            if flags & os.O_RDWR or flags & os.O_WRONLY:
                raise llfuse.FUSEError(errno.EPERM)
            return inode

        def read(self, fh, off, size):
            assert fh == self.hello_inode
            return self.hello_data[off:off+size]

    def init_logging(debug=False):
        formatter = logging.Formatter('%(asctime)s.%(msecs)03d %(threadName)s: '
                                      '[%(name)s] %(message)s', datefmt="%Y-%m-%d %H:%M:%S")
        handler = logging.StreamHandler()
        handler.setFormatter(formatter)
        root_logger = logging.getLogger()
        if debug:
            handler.setLevel(logging.DEBUG)
            root_logger.setLevel(logging.DEBUG)
        else:
            handler.setLevel(logging.INFO)
            root_logger.setLevel(logging.INFO)
        root_logger.addHandler(handler)

    def parse_args():
        '''Parse command line'''

        parser = ArgumentParser()

        parser.add_argument('mountpoint', type=str,
                            help='Where to mount the file system')
        parser.add_argument('--debug', action='store_true', default=False,
                            help='Enable debugging output')
        parser.add_argument('--debug-fuse', action='store_true', default=False,
                            help='Enable FUSE debugging output')
        return parser.parse_args()

    def main():
        options = parse_args()
        init_logging(options.debug)

        testfs = TestFs()
        fuse_options = set(llfuse.default_options)
        fuse_options.add('fsname=lltest')
        if options.debug_fuse:
            fuse_options.add('debug')
        llfuse.init(testfs, options.mountpoint, fuse_options)
        try:
            llfuse.main(workers=1)
        except:
            llfuse.close(unmount=False)
            raise

        llfuse.close()

    if __name__ == '__main__':
        main()

## In-memory File System

(shipped as `examples/tmpfs.py`)

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    #!/usr/bin/env python3
    # -*- coding: utf-8 -*-
    '''
    tmpfs.py - Example file system for Python-LLFUSE.

    This file system stores all data in memory. It is compatible with both Python
    2.x and 3.x.

    Copyright © 2013 Nikolaus Rath <Nikolaus.org>

    Permission is hereby granted, free of charge, to any person obtaining a copy of
    this software and associated documentation files (the "Software"), to deal in
    the Software without restriction, including without limitation the rights to
    use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
    the Software, and to permit persons to whom the Software is furnished to do so.

    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
    FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
    COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
    IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
    CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
    '''

    from __future__ import division, print_function, absolute_import

    import os
    import sys

    # We are running from the Python-LLFUSE source directory, put it
    # into the Python path.
    basedir = os.path.abspath(os.path.join(os.path.dirname(sys.argv[0]), '..'))
    if (os.path.exists(os.path.join(basedir, 'setup.py')) and
        os.path.exists(os.path.join(basedir, 'src', 'llfuse'))):
        sys.path.append(os.path.join(basedir, 'src'))

    import llfuse
    import errno
    import stat
    from time import time
    import sqlite3
    import logging
    from collections import defaultdict
    from llfuse import FUSEError
    from argparse import ArgumentParser

    try:
        import faulthandler
    except ImportError:
        pass
    else:
        faulthandler.enable()

    log = logging.getLogger()

    # For Python 2 + 3 compatibility
    if sys.version_info[0] == 2:
        def next(it):
            return it.next()
    else:
        buffer = memoryview

    class Operations(llfuse.Operations):
        '''An example filesystem that stores all data in memory

        This is a very simple implementation with terrible performance.
        Don't try to store significant amounts of data. Also, there are
        some other flaws that have not been fixed to keep the code easier
        to understand:

        * atime, mtime and ctime are not updated
        * generation numbers are not supported
        '''

        def __init__(self):
            super(Operations, self).__init__()
            self.db = sqlite3.connect(':memory:')
            self.db.text_factory = str
            self.db.row_factory = sqlite3.Row
            self.cursor = self.db.cursor()
            self.inode_open_count = defaultdict(int)
            self.init_tables()

        def init_tables(self):
            '''Initialize file system tables'''

            self.cursor.execute("""
            CREATE TABLE inodes (
                id        INTEGER PRIMARY KEY,
                uid       INT NOT NULL,
                gid       INT NOT NULL,
                mode      INT NOT NULL,
                mtime_ns  INT NOT NULL,
                atime_ns  INT NOT NULL,
                ctime_ns  INT NOT NULL,
                target    BLOB(256) ,
                size      INT NOT NULL DEFAULT 0,
                rdev      INT NOT NULL DEFAULT 0,
                data      BLOB
            )
            """)

            self.cursor.execute("""
            CREATE TABLE contents (
                rowid     INTEGER PRIMARY KEY AUTOINCREMENT,
                name      BLOB(256) NOT NULL,
                inode     INT NOT NULL REFERENCES inodes(id),
                parent_inode INT NOT NULL REFERENCES inodes(id),

                UNIQUE (name, parent_inode)
            )""")

            # Insert root directory
            now_ns = int(time() * 1e9)
            self.cursor.execute("INSERT INTO inodes (id,mode,uid,gid,mtime_ns,atime_ns,ctime_ns) "
                                "VALUES (?,?,?,?,?,?,?)",
                                (llfuse.ROOT_INODE, stat.S_IFDIR | stat.S_IRUSR | stat.S_IWUSR
                                  | stat.S_IXUSR | stat.S_IRGRP | stat.S_IXGRP | stat.S_IROTH
                                  | stat.S_IXOTH, os.getuid(), os.getgid(), now_ns, now_ns, now_ns))
            self.cursor.execute("INSERT INTO contents (name, parent_inode, inode) VALUES (?,?,?)",
                                (b'..', llfuse.ROOT_INODE, llfuse.ROOT_INODE))

        def get_row(self, *a, **kw):
            self.cursor.execute(*a, **kw)
            try:
                row = next(self.cursor)
            except StopIteration:
                raise NoSuchRowError()
            try:
                next(self.cursor)
            except StopIteration:
                pass
            else:
                raise NoUniqueValueError()

            return row

        def lookup(self, inode_p, name, ctx=None):
            if name == '.':
                inode = inode_p
            elif name == '..':
                inode = self.get_row("SELECT * FROM contents WHERE inode=?",
                                     (inode_p,))['parent_inode']
            else:
                try:
                    inode = self.get_row("SELECT * FROM contents WHERE name=? AND parent_inode=?",
                                         (name, inode_p))['inode']
                except NoSuchRowError:
                    raise(llfuse.FUSEError(errno.ENOENT))

            return self.getattr(inode, ctx)

        def getattr(self, inode, ctx=None):
            row = self.get_row('SELECT * FROM inodes WHERE id=?', (inode,))

            entry = llfuse.EntryAttributes()
            entry.st_ino = inode
            entry.generation = 0
            entry.entry_timeout = 300
            entry.attr_timeout = 300
            entry.st_mode = row['mode']
            entry.st_nlink = self.get_row("SELECT COUNT(inode) FROM contents WHERE inode=?",
                                         (inode,))[0]
            entry.st_uid = row['uid']
            entry.st_gid = row['gid']
            entry.st_rdev = row['rdev']
            entry.st_size = row['size']

            entry.st_blksize = 512
            entry.st_blocks = 1
            entry.st_atime_ns = row['atime_ns']
            entry.st_mtime_ns = row['mtime_ns']
            entry.st_ctime_ns = row['ctime_ns']

            return entry

        def readlink(self, inode, ctx):
            return self.get_row('SELECT * FROM inodes WHERE id=?', (inode,))['target']

        def opendir(self, inode, ctx):
            return inode

        def readdir(self, inode, off):
            if off == 0:
                off = -1

            cursor2 = self.db.cursor()
            cursor2.execute("SELECT * FROM contents WHERE parent_inode=? "
                            'AND rowid > ? ORDER BY rowid', (inode, off))

            for row in cursor2:
                yield (row['name'], self.getattr(row['inode']), row['rowid'])

        def unlink(self, inode_p, name,ctx):
            entry = self.lookup(inode_p, name)

            if stat.S_ISDIR(entry.st_mode):
                raise llfuse.FUSEError(errno.EISDIR)

            self._remove(inode_p, name, entry)

        def rmdir(self, inode_p, name, ctx):
            entry = self.lookup(inode_p, name)

            if not stat.S_ISDIR(entry.st_mode):
                raise llfuse.FUSEError(errno.ENOTDIR)

            self._remove(inode_p, name, entry)

        def _remove(self, inode_p, name, entry):
            if self.get_row("SELECT COUNT(inode) FROM contents WHERE parent_inode=?",
                            (entry.st_ino,))[0] > 0:
                raise llfuse.FUSEError(errno.ENOTEMPTY)

            self.cursor.execute("DELETE FROM contents WHERE name=? AND parent_inode=?",
                            (name, inode_p))

            if entry.st_nlink == 1 and entry.st_ino not in self.inode_open_count:
                self.cursor.execute("DELETE FROM inodes WHERE id=?", (entry.st_ino,))

        def symlink(self, inode_p, name, target, ctx):
            mode = (stat.S_IFLNK | stat.S_IRUSR | stat.S_IWUSR | stat.S_IXUSR |
                    stat.S_IRGRP | stat.S_IWGRP | stat.S_IXGRP |
                    stat.S_IROTH | stat.S_IWOTH | stat.S_IXOTH)
            return self._create(inode_p, name, mode, ctx, target=target)

        def rename(self, inode_p_old, name_old, inode_p_new, name_new, ctx):
            entry_old = self.lookup(inode_p_old, name_old)

            try:
                entry_new = self.lookup(inode_p_new, name_new)
            except llfuse.FUSEError as exc:
                if exc.errno != errno.ENOENT:
                    raise
                target_exists = False
            else:
                target_exists = True

            if target_exists:
                self._replace(inode_p_old, name_old, inode_p_new, name_new,
                              entry_old, entry_new)
            else:
                self.cursor.execute("UPDATE contents SET name=?, parent_inode=? WHERE name=? "
                                    "AND parent_inode=?", (name_new, inode_p_new,
                                                           name_old, inode_p_old))

        def _replace(self, inode_p_old, name_old, inode_p_new, name_new,
                     entry_old, entry_new):

            if self.get_row("SELECT COUNT(inode) FROM contents WHERE parent_inode=?",
                            (entry_new.st_ino,))[0] > 0:
                raise llfuse.FUSEError(errno.ENOTEMPTY)

            self.cursor.execute("UPDATE contents SET inode=? WHERE name=? AND parent_inode=?",
                                (entry_old.st_ino, name_new, inode_p_new))
            self.db.execute('DELETE FROM contents WHERE name=? AND parent_inode=?',
                            (name_old, inode_p_old))

            if entry_new.st_nlink == 1 and entry_new.st_ino not in self.inode_open_count:
                self.cursor.execute("DELETE FROM inodes WHERE id=?", (entry_new.st_ino,))

        def link(self, inode, new_inode_p, new_name, ctx):
            entry_p = self.getattr(new_inode_p)
            if entry_p.st_nlink == 0:
                log.warn('Attempted to create entry %s with unlinked parent %d',
                         new_name, new_inode_p)
                raise FUSEError(errno.EINVAL)

            self.cursor.execute("INSERT INTO contents (name, inode, parent_inode) VALUES(?,?,?)",
                                (new_name, inode, new_inode_p))

            return self.getattr(inode)

        def setattr(self, inode, attr, fields, fh, ctx):

            if fields.update_size:
                data = self.get_row('SELECT data FROM inodes WHERE id=?', (inode,))[0]
                if data is None:
                    data = b''
                if len(data) < attr.st_size:
                    data = data + b'\0' * (attr.st_size - len(data))
                else:
                    data = data[:attr.st_size]
                self.cursor.execute('UPDATE inodes SET data=?, size=? WHERE id=?',
                                    (buffer(data), attr.st_size, inode))
            if fields.update_mode:
                self.cursor.execute('UPDATE inodes SET mode=? WHERE id=?',
                                    (attr.st_mode, inode))

            if fields.update_uid:
                self.cursor.execute('UPDATE inodes SET uid=? WHERE id=?',
                                    (attr.st_uid, inode))

            if fields.update_gid:
                self.cursor.execute('UPDATE inodes SET gid=? WHERE id=?',
                                    (attr.st_gid, inode))

            if fields.update_atime:
                self.cursor.execute('UPDATE inodes SET atime_ns=? WHERE id=?',
                                    (attr.st_atime_ns, inode))

            if fields.update_mtime:
                self.cursor.execute('UPDATE inodes SET mtime_ns=? WHERE id=?',
                                    (attr.st_mtime_ns, inode))

            return self.getattr(inode)

        def mknod(self, inode_p, name, mode, rdev, ctx):
            return self._create(inode_p, name, mode, ctx, rdev=rdev)

        def mkdir(self, inode_p, name, mode, ctx):
            return self._create(inode_p, name, mode, ctx)

        def statfs(self, ctx):
            stat_ = llfuse.StatvfsData()

            stat_.f_bsize = 512
            stat_.f_frsize = 512

            size = self.get_row('SELECT SUM(size) FROM inodes')[0]
            stat_.f_blocks = size // stat_.f_frsize
            stat_.f_bfree = max(size // stat_.f_frsize, 1024)
            stat_.f_bavail = stat_.f_bfree

            inodes = self.get_row('SELECT COUNT(id) FROM inodes')[0]
            stat_.f_files = inodes
            stat_.f_ffree = max(inodes , 100)
            stat_.f_favail = stat_.f_ffree

            return stat_

        def open(self, inode, flags, ctx):
            # Yeah, unused arguments
            #pylint: disable=W0613
            self.inode_open_count[inode] += 1

            # Use inodes as a file handles
            return inode

        def access(self, inode, mode, ctx):
            # Yeah, could be a function and has unused arguments
            #pylint: disable=R0201,W0613
            return True

        def create(self, inode_parent, name, mode, flags, ctx):
            #pylint: disable=W0612
            entry = self._create(inode_parent, name, mode, ctx)
            self.inode_open_count[entry.st_ino] += 1
            return (entry.st_ino, entry)

        def _create(self, inode_p, name, mode, ctx, rdev=0, target=None):
            if self.getattr(inode_p).st_nlink == 0:
                log.warn('Attempted to create entry %s with unlinked parent %d',
                         name, inode_p)
                raise FUSEError(errno.EINVAL)

            now_ns = int(time() * 1e9)
            self.cursor.execute('INSERT INTO inodes (uid, gid, mode, mtime_ns, atime_ns, '
                                'ctime_ns, target, rdev) VALUES(?, ?, ?, ?, ?, ?, ?, ?)',
                                (ctx.uid, ctx.gid, mode, now_ns, now_ns, now_ns, target, rdev))

            inode = self.cursor.lastrowid
            self.db.execute("INSERT INTO contents(name, inode, parent_inode) VALUES(?,?,?)",
                            (name, inode, inode_p))
            return self.getattr(inode)

        def read(self, fh, offset, length):
            data = self.get_row('SELECT data FROM inodes WHERE id=?', (fh,))[0]
            if data is None:
                data = b''
            return data[offset:offset+length]

        def write(self, fh, offset, buf):
            data = self.get_row('SELECT data FROM inodes WHERE id=?', (fh,))[0]
            if data is None:
                data = b''
            data = data[:offset] + buf + data[offset+len(buf):]

            self.cursor.execute('UPDATE inodes SET data=?, size=? WHERE id=?',
                                (buffer(data), len(data), fh))
            return len(buf)

        def release(self, fh):
            self.inode_open_count[fh] -= 1

            if self.inode_open_count[fh] == 0:
                del self.inode_open_count[fh]
                if self.getattr(fh).st_nlink == 0:
                    self.cursor.execute("DELETE FROM inodes WHERE id=?", (fh,))

    class NoUniqueValueError(Exception):
        def __str__(self):
            return 'Query generated more than 1 result row'

    class NoSuchRowError(Exception):
        def __str__(self):
            return 'Query produced 0 result rows'

    def init_logging(debug=False):
        formatter = logging.Formatter('%(asctime)s.%(msecs)03d %(threadName)s: '
                                      '[%(name)s] %(message)s', datefmt="%Y-%m-%d %H:%M:%S")
        handler = logging.StreamHandler()
        handler.setFormatter(formatter)
        root_logger = logging.getLogger()
        if debug:
            handler.setLevel(logging.DEBUG)
            root_logger.setLevel(logging.DEBUG)
        else:
            handler.setLevel(logging.INFO)
            root_logger.setLevel(logging.INFO)
        root_logger.addHandler(handler)

    def parse_args():
        '''Parse command line'''

        parser = ArgumentParser()

        parser.add_argument('mountpoint', type=str,
                            help='Where to mount the file system')
        parser.add_argument('--debug', action='store_true', default=False,
                            help='Enable debugging output')
        parser.add_argument('--debug-fuse', action='store_true', default=False,
                            help='Enable FUSE debugging output')

        return parser.parse_args()

    if __name__ == '__main__':

        options = parse_args()
        init_logging(options.debug)
        operations = Operations()

        fuse_options = set(llfuse.default_options)
        fuse_options.add('fsname=tmpfs')
        fuse_options.discard('default_permissions')
        if options.debug_fuse:
            fuse_options.add('debug')
        llfuse.init(operations, options.mountpoint, fuse_options)

        # sqlite3 does not support multithreading
        try:
            llfuse.main(workers=1)
        except:
            llfuse.close(unmount=False)
            raise

        llfuse.close()

## Passthrough / Overlay File System

(shipped as `examples/passthroughfs.py`)

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    #!/usr/bin/env python3
    '''
    passthroughfs.py - Example file system for Python-LLFUSE

    This file system mirrors the contents of a specified directory tree. It requires
    Python 3.3 (since Python 2.x does not support the follow_symlinks parameters for
    os.* functions).

    Caveats:

     * Inode generation numbers are not passed through but set to zero.

     * Block size (st_blksize) and number of allocated blocks (st_blocks) are not
       passed through.

     * Performance for large directories is not good, because the directory
       is always read completely.

     * There may be a way to break-out of the directory tree.

     * The readdir implementation is not fully POSIX compliant. If a directory
       contains hardlinks and is modified during a readdir call, readdir()
       may return some of the hardlinked files twice or omit them completely.

     * If you delete or rename files in the underlying file system, the
       passthrough file system will get confused.

    Copyright ©  Nikolaus Rath <Nikolaus.org>

    Permission is hereby granted, free of charge, to any person obtaining a copy of
    this software and associated documentation files (the "Software"), to deal in
    the Software without restriction, including without limitation the rights to
    use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
    the Software, and to permit persons to whom the Software is furnished to do so.

    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
    IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
    FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
    COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
    IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
    CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
    '''

    import os
    import sys

    # We are running from the Python-LLFUSE source directory, put it
    # into the Python path.
    basedir = os.path.abspath(os.path.join(os.path.dirname(sys.argv[0]), '..'))
    if (os.path.exists(os.path.join(basedir, 'setup.py')) and
        os.path.exists(os.path.join(basedir, 'src', 'llfuse'))):
        sys.path.append(os.path.join(basedir, 'src'))

    import llfuse
    from argparse import ArgumentParser
    import errno
    import logging
    import stat as stat_m
    from llfuse import FUSEError
    from os import fsencode, fsdecode
    from collections import defaultdict

    import faulthandler
    faulthandler.enable()

    log = logging.getLogger(__name__)

    class Operations(llfuse.Operations):

        def __init__(self, source):
            super().__init__()
            self._inode_path_map = { llfuse.ROOT_INODE: source }
            self._lookup_cnt = defaultdict(lambda : 0)
            self._fd_inode_map = dict()
            self._inode_fd_map = dict()
            self._fd_open_count = dict()

        def _inode_to_path(self, inode):
            try:
                val = self._inode_path_map[inode]
            except KeyError:
                raise FUSEError(errno.ENOENT)

            if isinstance(val, set):
                # In case of hardlinks, pick any path
                val = next(iter(val))
            return val

        def _add_path(self, inode, path):
            log.debug('_add_path for %d, %s', inode, path)
            self._lookup_cnt[inode] += 1

            # With hardlinks, one inode may map to multiple paths.
            if inode not in self._inode_path_map:
                self._inode_path_map[inode] = path
                return

            val = self._inode_path_map[inode]
            if isinstance(val, set):
                val.add(path)
            elif val != path:
                self._inode_path_map[inode] = { path, val }

        def forget(self, inode_list):
            for (inode, nlookup) in inode_list:
                if self._lookup_cnt[inode] > nlookup:
                    self._lookup_cnt[inode] -= nlookup
                    continue
                log.debug('forgetting about inode %d', inode)
                assert inode not in self._inode_fd_map
                del self._lookup_cnt[inode]
                try:
                    del self._inode_path_map[inode]
                except KeyError: # may have been deleted
                    pass

        def lookup(self, inode_p, name, ctx=None):
            name = fsdecode(name)
            log.debug('lookup for %s in %d', name, inode_p)
            path = os.path.join(self._inode_to_path(inode_p), name)
            attr = self._getattr(path=path)
            if name != '.' and name != '..':
                self._add_path(attr.st_ino, path)
            return attr

        def getattr(self, inode, ctx=None):
            if inode in self._inode_fd_map:
                return self._getattr(fd=self._inode_fd_map[inode])
            else:
                return self._getattr(path=self._inode_to_path(inode))

        def _getattr(self, path=None, fd=None):
            assert fd is None or path is None
            assert not(fd is None and path is None)
            try:
                if fd is None:
                    stat = os.lstat(path)
                else:
                    stat = os.fstat(fd)
            except OSError as exc:
                raise FUSEError(exc.errno)

            entry = llfuse.EntryAttributes()
            for attr in ('st_ino', 'st_mode', 'st_nlink', 'st_uid', 'st_gid',
                         'st_rdev', 'st_size', 'st_atime_ns', 'st_mtime_ns',
                         'st_ctime_ns'):
                setattr(entry, attr, getattr(stat, attr))
            entry.generation = 0
            entry.entry_timeout = 5
            entry.attr_timeout = 5
            entry.st_blksize = 512
            entry.st_blocks = ((entry.st_size+entry.st_blksize-1) // entry.st_blksize)

            return entry

        def readlink(self, inode, ctx):
            path = self._inode_to_path(inode)
            try:
                target = os.readlink(path)
            except OSError as exc:
                raise FUSEError(exc.errno)
            return fsencode(target)

        def opendir(self, inode, ctx):
            return inode

        def readdir(self, inode, off):
            path = self._inode_to_path(inode)
            log.debug('reading %s', path)
            entries = []
            for name in os.listdir(path):
                attr = self._getattr(path=os.path.join(path, name))
                entries.append((attr.st_ino, name, attr))

            log.debug('read %d entries, starting at %d', len(entries), off)

            # This is not fully posix compatible. If there are hardlinks
            # (two names with the same inode), we don't have a unique
            # offset to start in between them. Note that we cannot simply
            # count entries, because then we would skip over entries
            # (or return them more than once) if the number of directory
            # entries changes between two calls to readdir().
            for (ino, name, attr) in sorted(entries):
                if ino <= off:
                    continue
                yield (fsencode(name), attr, ino)

        def unlink(self, inode_p, name, ctx):
            name = fsdecode(name)
            parent = self._inode_to_path(inode_p)
            path = os.path.join(parent, name)
            try:
                inode = os.lstat(path).st_ino
                os.unlink(path)
            except OSError as exc:
                raise FUSEError(exc.errno)
            if inode in self._lookup_cnt:
                self._forget_path(inode, path)

        def rmdir(self, inode_p, name, ctx):
            name = fsdecode(name)
            parent = self._inode_to_path(inode_p)
            path = os.path.join(parent, name)
            try:
                inode = os.lstat(path).st_ino
                os.rmdir(path)
            except OSError as exc:
                raise FUSEError(exc.errno)
            if inode in self._lookup_cnt:
                self._forget_path(inode, path)

        def _forget_path(self, inode, path):
            log.debug('forget %s for %d', path, inode)
            val = self._inode_path_map[inode]
            if isinstance(val, set):
                val.remove(path)
                if len(val) == 1:
                    self._inode_path_map[inode] = next(iter(val))
            else:
                del self._inode_path_map[inode]

        def symlink(self, inode_p, name, target, ctx):
            name = fsdecode(name)
            target = fsdecode(target)
            parent = self._inode_to_path(inode_p)
            path = os.path.join(parent, name)
            try:
                os.symlink(target, path)
            except OSError as exc:
                raise FUSEError(exc.errno)
            stat = os.lstat(path)
            self._add_path(stat.st_ino, path)
            return self.getattr(stat.st_ino)

        def rename(self, inode_p_old, name_old, inode_p_new, name_new, ctx):
            name_old = fsdecode(name_old)
            name_new = fsdecode(name_new)
            parent_old = self._inode_to_path(inode_p_old)
            parent_new = self._inode_to_path(inode_p_new)
            path_old = os.path.join(parent_old, name_old)
            path_new = os.path.join(parent_new, name_new)
            try:
                os.rename(path_old, path_new)
                inode = os.lstat(path_new).st_ino
            except OSError as exc:
                raise FUSEError(exc.errno)
            if inode not in self._lookup_cnt:
                return

            val = self._inode_path_map[inode]
            if isinstance(val, set):
                assert len(val) > 1
                set.add(path_new)
                set.remove(path_old)
            else:
                assert val == path_old
                self._inode_path_map[inode] = path_new

        def link(self, inode, new_inode_p, new_name, ctx):
            new_name = fsdecode(new_name)
            parent = self._inode_to_path(new_inode_p)
            path = os.path.join(parent, new_name)
            try:
                os.link(self._inode_to_path(inode), path, follow_symlinks=False)
            except OSError as exc:
                raise FUSEError(exc.errno)
            self._add_path(inode, path)
            return self.getattr(inode)

        def setattr(self, inode, attr, fields, fh, ctx):
            # We use the f* functions if possible so that we can handle
            # a setattr() call for an inode without associated directory
            # handle.
            if fh is None:
                path_or_fh = self._inode_to_path(inode)
                truncate = os.truncate
                chmod = os.chmod
                chown = os.chown
            else:
                path_or_fh = fh
                truncate = os.ftruncate
                chmod = os.fchmod
                chown = os.fchown

            try:
                if fields.update_size:
                    truncate(path_or_fh, attr.st_size)

                if fields.update_mode:
                    chmod(path_or_fh, ~stat_m.S_IFMT & attr.st_mode,
                          follow_symlinks=False)

                if fields.update_uid or fields.update_gid:
                    chown(path_or_fh, attr.st_uid, attr.st_gid,
                          follow_symlinks=False)

                if fields.update_atime or fields.update_mtime:
                    # utime accepts both paths and file descriptiors
                    os.utime(path_or_fh, None, follow_symlinks=False,
                             ns=(attr.st_atime_ns, attr.st_mtime_ns))

            except OSError as exc:
                raise FUSEError(exc.errno)

            return self.getattr(inode)

        def mknod(self, inode_p, name, mode, rdev, ctx):
            path = os.path.join(self._inode_to_path(inode_p), fsdecode(name))
            try:
                os.mknod(path, mode=(mode & ~ctx.umask), device=rdev)
                os.chown(path, ctx.uid, ctx.gid)
            except OSError as exc:
                raise FUSEError(exc.errno)
            attr = self._getattr(path=path)
            self._add_path(attr.st_ino, path)
            return attr

        def mkdir(self, inode_p, name, mode, ctx):
            path = os.path.join(self._inode_to_path(inode_p), fsdecode(name))
            try:
                os.mkdir(path, mode=(mode & ~ctx.umask))
                os.chown(path, ctx.uid, ctx.gid)
            except OSError as exc:
                raise FUSEError(exc.errno)
            attr = self._getattr(path=path)
            self._add_path(attr.st_ino, path)
            return attr

        def statfs(self, ctx):
            stat_ = llfuse.StatvfsData()
            try:
                statfs = os.statvfs(self._inode_path_map[llfuse.ROOT_INODE])
            except OSError as exc:
                raise FUSEError(exc.errno)
            for attr in ('f_bsize', 'f_frsize', 'f_blocks', 'f_bfree', 'f_bavail',
                         'f_files', 'f_ffree', 'f_favail'):
                setattr(stat_, attr, getattr(statfs, attr))
            return stat_

        def open(self, inode, flags, ctx):
            if inode in self._inode_fd_map:
                fd = self._inode_fd_map[inode]
                self._fd_open_count[fd] += 1
                return fd
            assert flags & os.O_CREAT == 0
            try:
                fd = os.open(self._inode_to_path(inode), flags)
            except OSError as exc:
                raise FUSEError(exc.errno)
            self._inode_fd_map[inode] = fd
            self._fd_inode_map[fd] = inode
            self._fd_open_count[fd] = 1
            return fd

        def create(self, inode_p, name, mode, flags, ctx):
            path = os.path.join(self._inode_to_path(inode_p), fsdecode(name))
            try:
                fd = os.open(path, flags | os.O_CREAT | os.O_TRUNC)
            except OSError as exc:
                raise FUSEError(exc.errno)
            attr = self._getattr(fd=fd)
            self._add_path(attr.st_ino, path)
            self._inode_fd_map[attr.st_ino] = fd
            self._fd_inode_map[fd] = attr.st_ino
            self._fd_open_count[fd] = 1
            return (fd, attr)

        def read(self, fd, offset, length):
            os.lseek(fd, offset, os.SEEK_SET)
            return os.read(fd, length)

        def write(self, fd, offset, buf):
            os.lseek(fd, offset, os.SEEK_SET)
            return os.write(fd, buf)

        def release(self, fd):
            if self._fd_open_count[fd] > 1:
                self._fd_open_count[fd] -= 1
                return

            del self._fd_open_count[fd]
            inode = self._fd_inode_map[fd]
            del self._inode_fd_map[inode]
            del self._fd_inode_map[fd]
            try:
                os.close(fd)
            except OSError as exc:
                raise FUSEError(exc.errno)

    def init_logging(debug=False):
        formatter = logging.Formatter('%(asctime)s.%(msecs)03d %(threadName)s: '
                                      '[%(name)s] %(message)s', datefmt="%Y-%m-%d %H:%M:%S")
        handler = logging.StreamHandler()
        handler.setFormatter(formatter)
        root_logger = logging.getLogger()
        if debug:
            handler.setLevel(logging.DEBUG)
            root_logger.setLevel(logging.DEBUG)
        else:
            handler.setLevel(logging.INFO)
            root_logger.setLevel(logging.INFO)
        root_logger.addHandler(handler)

    def parse_args(args):
        '''Parse command line'''

        parser = ArgumentParser()

        parser.add_argument('source', type=str,
                            help='Directory tree to mirror')
        parser.add_argument('mountpoint', type=str,
                            help='Where to mount the file system')
        parser.add_argument('--single', action='store_true', default=False,
                            help='Run single threaded')
        parser.add_argument('--debug', action='store_true', default=False,
                            help='Enable debugging output')
        parser.add_argument('--debug-fuse', action='store_true', default=False,
                            help='Enable FUSE debugging output')

        return parser.parse_args(args)

    def main():
        options = parse_args(sys.argv[1:])
        init_logging(options.debug)
        operations = Operations(options.source)

        log.debug('Mounting...')
        fuse_options = set(llfuse.default_options)
        fuse_options.add('fsname=passthroughfs')
        fuse_options.add('default_permissions')
        if options.debug_fuse:
            fuse_options.add('debug')
        llfuse.init(operations, options.mountpoint, fuse_options)

        try:
            log.debug('Entering main loop..')
            if options.single:
                llfuse.main(workers=1)
            else:
                llfuse.main()
        except:
            llfuse.close(unmount=False)
            raise

        log.debug('Unmounting..')
        llfuse.close()

    if __name__ == '__main__':
        main()

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