Add DictFS, for when the filesystem tree is known in advance

[invirt/packages/python-routefs.git] / routefs / __init__.py

diff --git a/routefs/__init__.py b/routefs/__init__.py
old mode 100755 (executable)
new mode 100644 (file)
index a230cd5..88b4f5c
--- a/routefs/__init__.py
+++ b/routefs/__init__.py
@@ -1,5 +1,173 @@
+"""
+RouteFS is a base class for developing read-only FUSE filesystems that
+lets you focus on the directory tree instead of the system calls.
+
+RouteFS uses the Routes library developed for Pylons. URLs were
+inspired by filesystems, and now you can have filesystems inspired by
+URLs.
+
+When developing a descendent of RouteFS, any methods defined in that
+class are considered "controllers", and receive any other parameters
+specified by the URL as keyword arguments.
+"""
+

 import fuse
 import fuse

-from fuse import Fuse
+import routes
+import errno
+import stat
+
+fuse.fuse_python_api = (0, 2)
+
+class RouteStat(fuse.Stat):
+    """
+    RouteStat is a descendent of fuse.Stat, defined to make sure that
+    all of the necessary attributes are always defined
+    """
+    def __init__(self):
+        self.st_mode = 0
+        self.st_ino = 0
+        self.st_dev = 0
+        self.st_nlink = 0
+        self.st_uid = 0
+        self.st_gid = 0
+        self.st_size = 0
+        self.st_atime = 0
+        self.st_mtime = 0
+        self.st_ctime = 0

 
 

-class RouteFS(Fuse):
+class RouteMeta(type):
+    """
+    Metaclass to calculate controller methods
+    
+    Routes needs to be pre-seeded with a list of "controllers". For
+    all descendents of RouteFS, the list of controllers is defined to
+    be any non-private methods of the class that were not in the
+    RouteFS class.
+    """
+    def __init__(cls, classname, bases, dict_):
+        super(RouteMeta, cls).__init__(classname, bases, dict_)
+        if bases != (fuse.Fuse,):
+            new_funcs = set(dict_.keys()).difference(dir(RouteFS))
+            cls.controllers([func for func in new_funcs \
+                                 if not func.startswith('_')])
+
+class RouteFS(fuse.Fuse):
+    """
+    RouteFS: Web 2.0 for filesystems
+    """
+    __metaclass__ = RouteMeta
+    def __init__(self, *args, **kwargs):
+        super(RouteFS, self).__init__(*args, **kwargs)
+        
+        self.map = self.make_map()
+        self.map.create_regs(self.controller_list)
+        
+    def make_map(self):
+        """
+        This method should be overridden by descendents of RouteFS to
+        define the routing for the filesystem
+        """
+        m = routes.Mapper()
+        
+        m.connect(':controller')
+        
+        return m
+    
+    @classmethod
+    def controllers(cls, lst):
+        cls.controller_list = lst
+    
+    def _get_file(self, path):
+        """
+        Find the filesystem entry object for a given path
+        """
+        match = self.map.match(path)
+        if match is None:
+            return
+        controller = match.pop('controller')
+        result = getattr(self, controller)(**match)
+        return result
+    
+    def readdir(self, path, offset):
+        """
+        If the path referred to is a directory, return the elements of
+        that diectory
+        """
+        obj = self._get_file(path)
+        if type(obj) is not Directory:
+            return
+        else:
+            for member in ['.', '..'] + obj:
+                yield fuse.Direntry(str(member))
+    
+    def getattr(self, path):
+        """
+        Return the stat information for a path
+        
+        The stat information for a directory, symlink, or file is
+        predetermined based on which it is.
+        """
+        obj = self._get_file(path)
+        if obj is None:
+            return -errno.ENOENT
+        
+        st = RouteStat()
+        if type(obj) is Directory:
+            st.st_mode = stat.S_IFDIR | 0755
+            st.st_nlink = 2
+        elif type(obj) is Symlink:
+            st.st_mode = stat.S_IFLNK | 0777
+            st.st_nlink = 1
+            st.st_size = len(obj)
+        else:
+            st.st_mode = stat.S_IFREG | 0444
+            st.st_nlink = 1
+            st.st_size = len(obj)
+        
+        return st
+    
+    def read(self, path, length, offset):
+        """
+        If the path specified is a file, return the requested portion
+        of the file
+        """
+        obj = self._get_file(path)
+        if obj is None:
+            return -errno.ENOENT
+        elif type(obj) in (Directory, Symlink):
+            return -errno.EINVAL
+        else:
+            return obj[offset:offset + length]
+    
+    def readlink(self, path):
+        """
+        If the path specified is a symlink, return the target
+        """
+        obj = self._get_file(path)
+        if type(obj) is not Symlink:
+            return -errno.EINVAL
+        else:
+            return obj
+
+class Directory(list):
+    """
+    A dummy class representing a filesystem entry that should be a
+    directory
+    """

     pass
     pass

+
+class Symlink(str):
+    """
+    A dummy class representing something that should be a symlink
+    """
+    pass
+
+def main(cls):
+    """
+    A convenience function for initializing a RouteFS filesystem
+    """
+    server = cls(version="%prog " + fuse.__version__,
+                 usage=fuse.Fuse.fusage,
+                 dash_s_do='setsingle')
+    server.parse(errex=1)
+    server.main()