dbus/service.py

   1 # Copyright (C) 2003, 2004, 2005, 2006 Red Hat Inc. <http://www.redhat.com/>
   2 # Copyright (C) 2003 David Zeuthen
   3 # Copyright (C) 2004 Rob Taylor
   4 # Copyright (C) 2005, 2006 Collabora Ltd. <http://www.collabora.co.uk/>
   5 #
   6 # Licensed under the Academic Free License version 2.1
   7 #
   8 # This program is free software; you can redistribute it and/or modify
   9 # it under the terms of the GNU General Public License as published by
  10 # the Free Software Foundation; either version 2 of the License, or
  11 # (at your option) any later version.
  12 #
  13 # This program is distributed in the hope that it will be useful,
  14 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 # GNU General Public License for more details.
  17 #
  18 # You should have received a copy of the GNU General Public License
  19 # along with this program; if not, write to the Free Software
  20 # Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  21
  22 __all__ = ('BusName', 'Object', 'method', 'signal')
  23 __docformat__ = 'restructuredtext'
  24
  25 import sys
  26 import logging
  27 import operator
  28 import traceback
  29 try:
  30     import thread
  31 except ImportError:
  32     import dummy_thread as thread
  33
  34 import _dbus_bindings
  35 from dbus import SessionBus
  36 from dbus.exceptions import DBusException, \
  37                             NameExistsException, \
  38                             UnknownMethodException
  39 from dbus.decorators import method
  40 from dbus.decorators import signal
  41 from dbus.proxies import LOCAL_PATH
  42
  43
  44 _logger = logging.getLogger('dbus.service')
  45
  46
  47 class _VariantSignature(object):
  48     """A fake method signature which, when iterated, yields an endless stream
  49     of 'v' characters representing variants (handy with zip()).
  50
  51     It has no string representation.
  52     """
  53     def __iter__(self):
  54         """Return self."""
  55         return self
  56
  57     def next(self):
  58         """Return 'v' whenever called."""
  59         return 'v'
  60
  61 class BusName(object):
  62     """A base class for exporting your own Named Services across the Bus.
  63
  64     When instantiated, objects of this class attempt to claim the given
  65     well-known name on the given bus for the current process. The name is
  66     released when the BusName object becomes unreferenced.
  67
  68     If a well-known name is requested multiple times, multiple references
  69     to the same BusName object will be returned.
  70
  71     Caveats
  72     -------
  73     - Assumes that named services are only ever requested using this class -
  74       if you request names from the bus directly, confusion may occur.
  75     - Does not handle queueing.
  76     """
  77     def __new__(cls, name, bus=None, allow_replacement=False , replace_existing=False, do_not_queue=False):
  78         """Constructor, which may either return an existing cached object
  79         or a new object.
  80
  81         :Parameters:
  82             `name` : str
  83                 The well-known name to be advertised
  84             `bus` : dbus.Bus
  85                 A Bus on which this service will be advertised; if None
  86                 (default) the session bus will be used
  87             `allow_replacement` : bool
  88                 If True, other processes trying to claim the same well-known
  89                 name will take precedence over this one.
  90             `replace_existing` : bool
  91                 If True, this process can take over the well-known name
  92                 from other processes already holding it.
  93             `do_not_queue` : bool
  94                 If True, this service will not be placed in the queue of
  95                 services waiting for the requested name if another service
  96                 already holds it.
  97         """
  98         _dbus_bindings.validate_bus_name(name, allow_well_known=True,
  99                                          allow_unique=False)
 100
 101         # get default bus
 102         if bus == None:
 103             bus = SessionBus()
 104
 105         # see if this name is already defined, return it if so
 106         # FIXME: accessing internals of Bus
 107         if name in bus._bus_names:
 108             return bus._bus_names[name]
 109
 110         # otherwise register the name
 111         name_flags = (
 112             (allow_replacement and _dbus_bindings.NAME_FLAG_ALLOW_REPLACEMENT or 0) |
 113             (replace_existing and _dbus_bindings.NAME_FLAG_REPLACE_EXISTING or 0) |
 114             (do_not_queue and _dbus_bindings.NAME_FLAG_DO_NOT_QUEUE or 0))
 115
 116         retval = bus.request_name(name, name_flags)
 117
 118         # TODO: more intelligent tracking of bus name states?
 119         if retval == _dbus_bindings.REQUEST_NAME_REPLY_PRIMARY_OWNER:
 120             pass
 121         elif retval == _dbus_bindings.REQUEST_NAME_REPLY_IN_QUEUE:
 122             # queueing can happen by default, maybe we should
 123             # track this better or let the user know if they're
 124             # queued or not?
 125             pass
 126         elif retval == _dbus_bindings.REQUEST_NAME_REPLY_EXISTS:
 127             raise NameExistsException(name)
 128         elif retval == _dbus_bindings.REQUEST_NAME_REPLY_ALREADY_OWNER:
 129             # if this is a shared bus which is being used by someone
 130             # else in this process, this can happen legitimately
 131             pass
 132         else:
 133             raise RuntimeError('requesting bus name %s returned unexpected value %s' % (name, retval))
 134
 135         # and create the object
 136         bus_name = object.__new__(cls)
 137         bus_name._bus = bus
 138         bus_name._name = name
 139
 140         # cache instance (weak ref only)
 141         # FIXME: accessing Bus internals again
 142         bus._bus_names[name] = bus_name
 143
 144         return bus_name
 145
 146     # do nothing because this is called whether or not the bus name
 147     # object was retrieved from the cache or created new
 148     def __init__(self, *args, **keywords):
 149         pass
 150
 151     # we can delete the low-level name here because these objects
 152     # are guaranteed to exist only once for each bus name
 153     def __del__(self):
 154         self._bus.release_name(self._name)
 155         pass
 156
 157     def get_bus(self):
 158         """Get the Bus this Service is on"""
 159         return self._bus
 160
 161     def get_name(self):
 162         """Get the name of this service"""
 163         return self._name
 164
 165     def __repr__(self):
 166         return '<dbus.service.BusName %s on %r at %#x>' % (self._name, self._bus, id(self))
 167     __str__ = __repr__
 168
 169
 170 def _method_lookup(self, method_name, dbus_interface):
 171     """Walks the Python MRO of the given class to find the method to invoke.
 172
 173     Returns two methods, the one to call, and the one it inherits from which
 174     defines its D-Bus interface name, signature, and attributes.
 175     """
 176     parent_method = None
 177     candidate_class = None
 178     successful = False
 179
 180     # split up the cases when we do and don't have an interface because the
 181     # latter is much simpler
 182     if dbus_interface:
 183         # search through the class hierarchy in python MRO order
 184         for cls in self.__class__.__mro__:
 185             # if we haven't got a candidate class yet, and we find a class with a
 186             # suitably named member, save this as a candidate class
 187             if (not candidate_class and method_name in cls.__dict__):
 188                 if ("_dbus_is_method" in cls.__dict__[method_name].__dict__
 189                     and "_dbus_interface" in cls.__dict__[method_name].__dict__):
 190                     # however if it is annotated for a different interface
 191                     # than we are looking for, it cannot be a candidate
 192                     if cls.__dict__[method_name]._dbus_interface == dbus_interface:
 193                         candidate_class = cls
 194                         parent_method = cls.__dict__[method_name]
 195                         successful = True
 196                         break
 197                     else:
 198                         pass
 199                 else:
 200                     candidate_class = cls
 201
 202             # if we have a candidate class, carry on checking this and all
 203             # superclasses for a method annoated as a dbus method
 204             # on the correct interface
 205             if (candidate_class and method_name in cls.__dict__
 206                 and "_dbus_is_method" in cls.__dict__[method_name].__dict__
 207                 and "_dbus_interface" in cls.__dict__[method_name].__dict__
 208                 and cls.__dict__[method_name]._dbus_interface == dbus_interface):
 209                 # the candidate class has a dbus method on the correct interface,
 210                 # or overrides a method that is, success!
 211                 parent_method = cls.__dict__[method_name]
 212                 successful = True
 213                 break
 214
 215     else:
 216         # simpler version of above
 217         for cls in self.__class__.__mro__:
 218             if (not candidate_class and method_name in cls.__dict__):
 219                 candidate_class = cls
 220
 221             if (candidate_class and method_name in cls.__dict__
 222                 and "_dbus_is_method" in cls.__dict__[method_name].__dict__):
 223                 parent_method = cls.__dict__[method_name]
 224                 successful = True
 225                 break
 226
 227     if successful:
 228         return (candidate_class.__dict__[method_name], parent_method)
 229     else:
 230         if dbus_interface:
 231             raise UnknownMethodException('%s is not a valid method of interface %s' % (method_name, dbus_interface))
 232         else:
 233             raise UnknownMethodException('%s is not a valid method' % method_name)
 234
 235
 236 def _method_reply_return(connection, message, method_name, signature, *retval):
 237     reply = _dbus_bindings.MethodReturnMessage(message)
 238     try:
 239         reply.append(signature=signature, *retval)
 240     except Exception, e:
 241         logging.basicConfig()
 242         if signature is None:
 243             try:
 244                 signature = reply.guess_signature(retval) + ' (guessed)'
 245             except Exception, e:
 246                 _logger.error('Unable to guess signature for arguments %r: '
 247                               '%s: %s', retval, e.__class__, e)
 248                 raise
 249         _logger.error('Unable to append %r to message with signature %s: '
 250                       '%s: %s', retval, signature, e.__class__, e)
 251         raise
 252
 253     connection.send_message(reply)
 254
 255
 256 def _method_reply_error(connection, message, exception):
 257     name = getattr(exception, '_dbus_error_name', None)
 258
 259     if name is not None:
 260         pass
 261     elif getattr(exception, '__module__', '') in ('', '__main__'):
 262         name = 'org.freedesktop.DBus.Python.%s' % exception.__class__.__name__
 263     else:
 264         name = 'org.freedesktop.DBus.Python.%s.%s' % (exception.__module__, exception.__class__.__name__)
 265
 266     contents = traceback.format_exc()
 267     reply = _dbus_bindings.ErrorMessage(message, name, contents)
 268
 269     connection.send_message(reply)
 270
 271
 272 class InterfaceType(type):
 273     def __init__(cls, name, bases, dct):
 274         # these attributes are shared between all instances of the Interface
 275         # object, so this has to be a dictionary that maps class names to
 276         # the per-class introspection/interface data
 277         class_table = getattr(cls, '_dbus_class_table', {})
 278         cls._dbus_class_table = class_table
 279         interface_table = class_table[cls.__module__ + '.' + name] = {}
 280
 281         # merge all the name -> method tables for all the interfaces
 282         # implemented by our base classes into our own
 283         for b in bases:
 284             base_name = b.__module__ + '.' + b.__name__
 285             if getattr(b, '_dbus_class_table', False):
 286                 for (interface, method_table) in class_table[base_name].iteritems():
 287                     our_method_table = interface_table.setdefault(interface, {})
 288                     our_method_table.update(method_table)
 289
 290         # add in all the name -> method entries for our own methods/signals
 291         for func in dct.values():
 292             if getattr(func, '_dbus_interface', False):
 293                 method_table = interface_table.setdefault(func._dbus_interface, {})
 294                 method_table[func.__name__] = func
 295
 296         super(InterfaceType, cls).__init__(name, bases, dct)
 297
 298     # methods are different to signals, so we have two functions... :)
 299     def _reflect_on_method(cls, func):
 300         args = func._dbus_args
 301
 302         if func._dbus_in_signature:
 303             # convert signature into a tuple so length refers to number of
 304             # types, not number of characters. the length is checked by
 305             # the decorator to make sure it matches the length of args.
 306             in_sig = tuple(_dbus_bindings.Signature(func._dbus_in_signature))
 307         else:
 308             # magic iterator which returns as many v's as we need
 309             in_sig = _VariantSignature()
 310
 311         if func._dbus_out_signature:
 312             out_sig = _dbus_bindings.Signature(func._dbus_out_signature)
 313         else:
 314             # its tempting to default to _dbus_bindings.Signature('v'), but
 315             # for methods that return nothing, providing incorrect
 316             # introspection data is worse than providing none at all
 317             out_sig = []
 318
 319         reflection_data = '    <method name="%s">\n' % (func.__name__)
 320         for pair in zip(in_sig, args):
 321             reflection_data += '      <arg direction="in"  type="%s" name="%s" />\n' % pair
 322         for type in out_sig:
 323             reflection_data += '      <arg direction="out" type="%s" />\n' % type
 324         reflection_data += '    </method>\n'
 325
 326         return reflection_data
 327
 328     def _reflect_on_signal(cls, func):
 329         args = func._dbus_args
 330
 331         if func._dbus_signature:
 332             # convert signature into a tuple so length refers to number of
 333             # types, not number of characters
 334             sig = tuple(_dbus_bindings.Signature(func._dbus_signature))
 335         else:
 336             # magic iterator which returns as many v's as we need
 337             sig = _VariantSignature()
 338
 339         reflection_data = '    <signal name="%s">\n' % (func.__name__)
 340         for pair in zip(sig, args):
 341             reflection_data = reflection_data + '      <arg type="%s" name="%s" />\n' % pair
 342         reflection_data = reflection_data + '    </signal>\n'
 343
 344         return reflection_data
 345
 346 class Interface(object):
 347     __metaclass__ = InterfaceType
 348
 349 #: A unique object used as the value of Object._object_path and
 350 #: Object._connection if it's actually in more than one place
 351 _MANY = object()
 352
 353 class Object(Interface):
 354     r"""A base class for exporting your own Objects across the Bus.
 355
 356     Just inherit from Object and mark exported methods with the
 357     @\ `dbus.service.method` or @\ `dbus.service.signal` decorator.
 358
 359     Example::
 360
 361         class Example(dbus.service.object):
 362             def __init__(self, object_path):
 363                 dbus.service.Object.__init__(self, dbus.SessionBus(), path)
 364                 self._last_input = None
 365
 366             @dbus.service.method(interface='com.example.Sample',
 367                                  in_signature='v', out_signature='s')
 368             def StringifyVariant(self, var):
 369                 self.LastInputChanged(var)      # emits the signal
 370                 return str(var)
 371
 372             @dbus.service.signal(interface='com.example.Sample',
 373                                  signature='v')
 374             def LastInputChanged(self, var):
 375                 # run just before the signal is actually emitted
 376                 # just put "pass" if nothing should happen
 377                 self._last_input = var
 378
 379             @dbus.service.method(interface='com.example.Sample',
 380                                  in_signature='', out_signature='v')
 381             def GetLastInput(self):
 382                 return self._last_input
 383     """
 384
 385     #: If True, this object can be made available at more than one object path.
 386     #: If True but `SUPPORTS_MULTIPLE_CONNECTIONS` is False, the object may
 387     #: handle more than one object path, but they must all be on the same
 388     #: connection.
 389     SUPPORTS_MULTIPLE_OBJECT_PATHS = False
 390
 391     #: If True, this object can be made available on more than one connection.
 392     #: If True but `SUPPORTS_MULTIPLE_OBJECT_PATHS` is False, the object must
 393     #: have the same object path on all its connections.
 394     SUPPORTS_MULTIPLE_CONNECTIONS = False
 395
 396     def __init__(self, conn=None, object_path=None, bus_name=None):
 397         """Constructor. Either conn or bus_name is required; object_path
 398         is also required.
 399
 400         :Parameters:
 401             `conn` : dbus.connection.Connection or None
 402                 The connection on which to export this object.
 403
 404                 If None, use the Bus associated with the given ``bus_name``.
 405                 If there is no ``bus_name`` either, the object is not
 406                 initially available on any Connection.
 407
 408                 For backwards compatibility, if an instance of
 409                 dbus.service.BusName is passed as the first parameter,
 410                 this is equivalent to passing its associated Bus as
 411                 ``conn``, and passing the BusName itself as ``bus_name``.
 412
 413             `object_path` : str or None
 414                 A D-Bus object path at which to make this Object available
 415                 immediately. If this is not None, a `conn` or `bus_name` must
 416                 also be provided.
 417
 418             `bus_name` : dbus.service.BusName or None
 419                 Represents a well-known name claimed by this process. A
 420                 reference to the BusName object will be held by this
 421                 Object, preventing the name from being released during this
 422                 Object's lifetime (unless it's released manually).
 423         """
 424         if object_path is not None:
 425             _dbus_bindings.validate_object_path(object_path)
 426
 427         if isinstance(conn, BusName):
 428             # someone's using the old API; don't gratuitously break them
 429             bus_name = conn
 430             conn = bus_name.get_bus()
 431         elif conn is None:
 432             if bus_name is not None:
 433                 # someone's using the old API but naming arguments, probably
 434                 conn = bus_name.get_bus()
 435
 436         #: Either an object path, None or _MANY
 437         self._object_path = None
 438         #: Either a dbus.connection.Connection, None or _MANY
 439         self._connection = None
 440         #: A list of tuples (Connection, object path, False) where the False
 441         #: is for future expansion (to support fallback paths)
 442         self._locations = []
 443         #: Lock protecting `_locations`, `_connection` and `_object_path`
 444         self._locations_lock = thread.allocate_lock()
 445
 446         #: True if this is a fallback object handling a whole subtree.
 447         self._fallback = False
 448
 449         self._name = bus_name
 450
 451         if conn is None and object_path is not None:
 452             raise TypeError('If object_path is given, either conn or bus_name '
 453                             'is required')
 454         if conn is not None and object_path is not None:
 455             self.add_to_connection(conn, object_path)
 456
 457     @property
 458     def __dbus_object_path__(self):
 459         """The object-path at which this object is available.
 460         Access raises AttributeError if there is no object path, or more than
 461         one object path.
 462         """
 463         if self._object_path is _MANY:
 464             raise AttributeError('Object %r has more than one object path: '
 465                                  'use Object.locations instead' % self)
 466         elif self._object_path is None:
 467             raise AttributeError('Object %r has no object path yet' % self)
 468         else:
 469             return self._object_path
 470
 471     @property
 472     def connection(self):
 473         """The Connection on which this object is available.
 474         Access raises AttributeError if there is no Connection, or more than
 475         one Connection.
 476         """
 477         if self._connection is _MANY:
 478             raise AttributeError('Object %r is on more than one Connection: '
 479                                  'use Object.locations instead' % self)
 480         elif self._connection is None:
 481             raise AttributeError('Object %r has no Connection yet' % self)
 482         else:
 483             return self._connection
 484
 485     @property
 486     def locations(self):
 487         """An iterable over tuples representing locations at which this
 488         object is available.
 489
 490         Each tuple has at least two items, but may have more in future
 491         versions of dbus-python, so do not rely on their exact length.
 492         The first two items are the dbus.connection.Connection and the object
 493         path.
 494         """
 495         return iter(self._locations)
 496
 497     def add_to_connection(self, connection, path):
 498         """Make this object accessible via the given D-Bus connection and
 499         object path.
 500
 501         :Parameters:
 502             `connection` : dbus.connection.Connection
 503                 Export the object on this connection. If the class attribute
 504                 SUPPORTS_MULTIPLE_CONNECTIONS is False (default), this object
 505                 can only be made available on one connection; if the class
 506                 attribute is set True by a subclass, the object can be made
 507                 available on more than one connection.
 508
 509             `path` : dbus.ObjectPath or other str
 510                 Place the object at this object path. If the class attribute
 511                 SUPPORTS_MULTIPLE_OBJECT_PATHS is False (default), this object
 512                 can only be made available at one object path; if the class
 513                 attribute is set True by a subclass, the object can be made
 514                 available with more than one object path.
 515         :Raises ValueError: if the object's class attributes do not allow the
 516             object to be exported in the desired way.
 517         """
 518         if path == LOCAL_PATH:
 519             raise ValueError('Objects may not be exported on the reserved '
 520                              'path %s' % LOCAL_PATH)
 521
 522         self._locations_lock.acquire()
 523         try:
 524             if (self._connection is not None and
 525                 self._connection is not connection and
 526                 not self.SUPPORTS_MULTIPLE_CONNECTIONS):
 527                 raise ValueError('%r is already exported on '
 528                                  'connection %r' % (self, self._connection))
 529
 530             if (self._object_path is not None and
 531                 not self.SUPPORTS_MULTIPLE_OBJECT_PATHS and
 532                 self._object_path != path):
 533                 raise ValueError('%r is already exported at object '
 534                                  'path %s' % (self, self._object_path))
 535
 536             connection._register_object_path(path, self._message_cb,
 537                                              self._unregister_cb,
 538                                              self._fallback)
 539
 540             if self._connection is None:
 541                 self._connection = connection
 542             elif self._connection is not connection:
 543                 self._connection = _MANY
 544
 545             if self._object_path is None:
 546                 self._object_path = path
 547             elif self._object_path != path:
 548                 self._object_path = _MANY
 549
 550             self._locations.append((connection, path, self._fallback))
 551         finally:
 552             self._locations_lock.release()
 553
 554     def remove_from_connection(self, connection=None, path=None):
 555         """Make this object inaccessible via the given D-Bus connection
 556         and object path. If no connection or path is specified,
 557         the object ceases to be accessible via any connection or path.
 558
 559         It's not currently possible to export an object on more than one
 560         connection or with more than one object-path, but this will be
 561         supported in future.
 562
 563         :Parameters:
 564             `connection` : dbus.connection.Connection or None
 565                 Only remove the object from this Connection. If None,
 566                 remove from all Connections on which it's exported.
 567             `path` : dbus.ObjectPath or other str, or None
 568                 Only remove the object from this object path. If None,
 569                 remove from all object paths.
 570         :Raises LookupError:
 571             if the object was not exported on the requested connection
 572             or path, or (if both are None) was not exported at all.
 573         """
 574         self._locations_lock.acquire()
 575         try:
 576             if self._object_path is None or self._connection is None:
 577                 raise LookupError('%r is not exported' % self)
 578
 579             if connection is not None or path is not None:
 580                 dropped = []
 581                 for location in self._locations:
 582                     if ((connection is None or location[0] is connection) and
 583                         (path is None or location[1] == path)):
 584                         dropped.append(location)
 585             else:
 586                 dropped = self._locations
 587                 self._locations = []
 588
 589             if not dropped:
 590                 raise LookupError('%r is not exported at a location matching '
 591                                   '(%r,%r)' % (self, connection, path))
 592
 593             for location in dropped:
 594                 try:
 595                     location[0]._unregister_object_path(location[1])
 596                 except LookupError:
 597                     pass
 598                 if self._locations:
 599                     try:
 600                         self._locations.remove(location)
 601                     except ValueError:
 602                         pass
 603         finally:
 604             self._locations_lock.release()
 605
 606     def _unregister_cb(self, connection):
 607         # there's not really enough information to do anything useful here
 608         _logger.info('Unregistering exported object %r from some path '
 609                      'on %r', self, connection)
 610
 611     def _message_cb(self, connection, message):
 612         try:
 613             # lookup candidate method and parent method
 614             method_name = message.get_member()
 615             interface_name = message.get_interface()
 616             (candidate_method, parent_method) = _method_lookup(self, method_name, interface_name)
 617
 618             # set up method call parameters
 619             args = message.get_args_list(**parent_method._dbus_get_args_options)
 620             keywords = {}
 621
 622             if parent_method._dbus_out_signature is not None:
 623                 signature = _dbus_bindings.Signature(parent_method._dbus_out_signature)
 624             else:
 625                 signature = None
 626
 627             # set up async callback functions
 628             if parent_method._dbus_async_callbacks:
 629                 (return_callback, error_callback) = parent_method._dbus_async_callbacks
 630                 keywords[return_callback] = lambda *retval: _method_reply_return(connection, message, method_name, signature, *retval)
 631                 keywords[error_callback] = lambda exception: _method_reply_error(connection, message, exception)
 632
 633             # include the sender etc. if desired
 634             if parent_method._dbus_sender_keyword:
 635                 keywords[parent_method._dbus_sender_keyword] = message.get_sender()
 636             if parent_method._dbus_path_keyword:
 637                 keywords[parent_method._dbus_path_keyword] = message.get_path()
 638             if parent_method._dbus_destination_keyword:
 639                 keywords[parent_method._dbus_destination_keyword] = message.get_destination()
 640             if parent_method._dbus_message_keyword:
 641                 keywords[parent_method._dbus_message_keyword] = message
 642             if parent_method._dbus_connection_keyword:
 643                 keywords[parent_method._dbus_connection_keyword] = connection
 644
 645             # call method
 646             retval = candidate_method(self, *args, **keywords)
 647
 648             # we're done - the method has got callback functions to reply with
 649             if parent_method._dbus_async_callbacks:
 650                 return
 651
 652             # otherwise we send the return values in a reply. if we have a
 653             # signature, use it to turn the return value into a tuple as
 654             # appropriate
 655             if signature is not None:
 656                 signature_tuple = tuple(signature)
 657                 # if we have zero or one return values we want make a tuple
 658                 # for the _method_reply_return function, otherwise we need
 659                 # to check we're passing it a sequence
 660                 if len(signature_tuple) == 0:
 661                     if retval == None:
 662                         retval = ()
 663                     else:
 664                         raise TypeError('%s has an empty output signature but did not return None' %
 665                             method_name)
 666                 elif len(signature_tuple) == 1:
 667                     retval = (retval,)
 668                 else:
 669                     if operator.isSequenceType(retval):
 670                         # multi-value signature, multi-value return... proceed unchanged
 671                         pass
 672                     else:
 673                         raise TypeError('%s has multiple output values in signature %s but did not return a sequence' %
 674                             (method_name, signature))
 675
 676             # no signature, so just turn the return into a tuple and send it as normal
 677             else:
 678                 if retval is None:
 679                     retval = ()
 680                 elif (isinstance(retval, tuple)
 681                       and not isinstance(retval, _dbus_bindings.Struct)):
 682                 # If the return is a tuple that is not a Struct, we use it
 683                 # as-is on the assumption that there are multiple return
 684                 # values - this is the usual Python idiom. (fd.o #10174)
 685                     pass
 686                 else:
 687                     retval = (retval,)
 688
 689             _method_reply_return(connection, message, method_name, signature, *retval)
 690         except Exception, exception:
 691             # send error reply
 692             _method_reply_error(connection, message, exception)
 693
 694     @method('org.freedesktop.DBus.Introspectable', in_signature='', out_signature='s')
 695     def Introspect(self):
 696         """Return a string of XML encoding this object's supported interfaces,
 697         methods and signals.
 698         """
 699         reflection_data = '<!DOCTYPE node PUBLIC "-//freedesktop//DTD D-BUS Object Introspection 1.0//EN" "http://www.freedesktop.org/standards/dbus/1.0/introspect.dtd">\n'
 700         reflection_data += '<node name="%s">\n' % (self._object_path)
 701
 702         interfaces = self._dbus_class_table[self.__class__.__module__ + '.' + self.__class__.__name__]
 703         for (name, funcs) in interfaces.iteritems():
 704             reflection_data += '  <interface name="%s">\n' % (name)
 705
 706             for func in funcs.values():
 707                 if getattr(func, '_dbus_is_method', False):
 708                     reflection_data += self.__class__._reflect_on_method(func)
 709                 elif getattr(func, '_dbus_is_signal', False):
 710                     reflection_data += self.__class__._reflect_on_signal(func)
 711
 712             reflection_data += '  </interface>\n'
 713
 714         for name in self._connection.list_exported_child_objects(
 715                 self._object_path):
 716             reflection_data += '  <node name="%s"/>\n' % name
 717
 718         reflection_data += '</node>\n'
 719
 720         return reflection_data
 721
 722     def __repr__(self):
 723         where = ''
 724         if (self._object_path is not _MANY
 725             and self._object_path is not None):
 726             where = ' at %s' % self._object_path
 727         return '<%s.%s%s at %#x>' % (self.__class__.__module__,
 728                                    self.__class__.__name__, where,
 729                                    id(self))
 730     __str__ = __repr__
 731
 732 class FallbackObject(Object):
 733     """An object that implements an entire subtree of the object-path
 734     tree."""
 735
 736     SUPPORTS_MULTIPLE_OBJECT_PATHS = True
 737
 738     def __init__(self, conn=None, object_path=None):
 739         """Constructor.
 740
 741         Note that the superclass' ``bus_name`` __init__ argument is not
 742         supported here.
 743
 744         :Parameters:
 745             `conn` : dbus.connection.Connection or None
 746                 The connection on which to export this object.
 747
 748                 If None, the object is not initially available on any
 749                 Connection.
 750
 751             `object_path` : str or None
 752                 A D-Bus object path at which to make this Object available
 753                 immediately. If this is not None, a `conn` or `bus_name` must
 754                 also be provided.
 755
 756                 This object will implements all object-paths in the subtree
 757                 starting at this object-path, except where a more specific
 758                 object has been added.
 759         """
 760         super(FallbackObject, self).__init__()
 761         self._fallback = True
 762
 763         if conn is None and object_path is not None:
 764             raise TypeError('If object_path is given, conn is required')
 765         if conn is not None and object_path is not None:
 766             self.add_to_connection(conn, object_path)