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# Example File System

The following is an example of a very simple in-memry file system based on LLFUSE (this example is also included in the LLFUSE tarball as `examples/tmpfs.py`).

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    from __future__ import division, print_function, absolute_import

    import os
    import sys

    # We are running from the llfuse source directory, make sure
    # that we use modules from this directory
    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.pyx'))):
        sys.path = [os.path.join(basedir, 'src')] + sys.path

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

    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     REAL NOT NULL,
                atime     REAL NOT NULL,
                ctime     REAL 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
            self.cursor.execute("INSERT INTO inodes (id,mode,uid,gid,mtime,atime,ctime) "
                                "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(), time(),
                                  time(), time()))
            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):
            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)

        def getattr(self, inode):
            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 = row['atime']
            entry.st_mtime = row['mtime']
            entry.st_ctime = row['ctime']

            return entry

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

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

            if attr.st_size is not None:
                data = self.get_row('SELECT data FROM inodes WHERE id=?', (inode,))[0]
                if data is None:
                    data = ''
                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 attr.st_mode is not None:
                self.cursor.execute('UPDATE inodes SET mode=? WHERE id=?',
                                    (attr.st_mode, inode))

            if attr.st_uid is not None:
                self.cursor.execute('UPDATE inodes SET uid=? WHERE id=?',
                                    (attr.st_uid, inode))

            if attr.st_gid is not None:
                self.cursor.execute('UPDATE inodes SET gid=? WHERE id=?',
                                    (attr.st_gid, inode))

            if attr.st_rdev is not None:
                self.cursor.execute('UPDATE inodes SET rdev=? WHERE id=?',
                                    (attr.st_rdev, inode))

            if attr.st_atime is not None:
                self.cursor.execute('UPDATE inodes SET atime=? WHERE id=?',
                                    (attr.st_atime, inode))

            if attr.st_mtime is not None:
                self.cursor.execute('UPDATE inodes SET mtime=? WHERE id=?',
                                    (attr.st_mtime, inode))

            if attr.st_ctime is not None:
                self.cursor.execute('UPDATE inodes SET ctime=? WHERE id=?',
                                    (attr.st_ctime, 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):
            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):
            # 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)

            self.cursor.execute('INSERT INTO inodes (uid, gid, mode, mtime, atime, '
                                'ctime, target, rdev) VALUES(?, ?, ?, ?, ?, ?, ?, ?)',
                                (ctx.uid, ctx.gid, mode, time(), time(), time(), 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():
        formatter = logging.Formatter('%(message)s')
        handler = logging.StreamHandler()
        handler.setFormatter(formatter)
        handler.setLevel(logging.INFO)
        log.setLevel(logging.INFO)
        log.addHandler(handler)

    if __name__ == '__main__':

        if len(sys.argv) != 2:
            raise SystemExit('Usage: %s <mountpoint>' % sys.argv[0])

        init_logging()
        mountpoint = sys.argv[1]
        operations = Operations()

        llfuse.init(operations, mountpoint,
                    [  'fsname=tmpfs', "nonempty" ])

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

        llfuse.close()

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