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
  30 import _dbus_bindings
  31 from dbus import SessionBus
  32 from dbus.exceptions import DBusException, \
  33                             NameExistsException, \
  34                             UnknownMethodException
  35 from dbus.decorators import method
  36 from dbus.decorators import signal
  37 from dbus.proxies import LOCAL_PATH
  38
  39
  40 _logger = logging.getLogger('dbus.service')
  41
  42
  43 class _VariantSignature(object):
  44     """A fake method signature which, when iterated, yields an endless stream
  45     of 'v' characters representing variants (handy with zip()).
  46
  47     It has no string representation.
  48     """
  49     def __iter__(self):
  50         """Return self."""
  51         return self
  52
  53     def next(self):
  54         """Return 'v' whenever called."""
  55         return 'v'
  56
  57 class BusName(object):
  58     """A base class for exporting your own Named Services across the Bus.
  59
  60     When instantiated, objects of this class attempt to claim the given
  61     well-known name on the given bus for the current process. The name is
  62     released when the BusName object becomes unreferenced.
  63
  64     If a well-known name is requested multiple times, multiple references
  65     to the same BusName object will be returned.
  66
  67     Caveats
  68     -------
  69     - Assumes that named services are only ever requested using this class -
  70       if you request names from the bus directly, confusion may occur.
  71     - Does not handle queueing.
  72     """
  73     def __new__(cls, name, bus=None, allow_replacement=False , replace_existing=False, do_not_queue=False):
  74         """Constructor, which may either return an existing cached object
  75         or a new object.
  76
  77         :Parameters:
  78             `name` : str
  79                 The well-known name to be advertised
  80             `bus` : dbus.Bus
  81                 A Bus on which this service will be advertised; if None
  82                 (default) the session bus will be used
  83             `allow_replacement` : bool
  84                 If True, other processes trying to claim the same well-known
  85                 name will take precedence over this one.
  86             `replace_existing` : bool
  87                 If True, this process can take over the well-known name
  88                 from other processes already holding it.
  89             `do_not_queue` : bool
  90                 If True, this service will not be placed in the queue of
  91                 services waiting for the requested name if another service
  92                 already holds it.
  93         """
  94         _dbus_bindings.validate_bus_name(name, allow_well_known=True,
  95                                          allow_unique=False)
  96
  97         # get default bus
  98         if bus == None:
  99             bus = SessionBus()
 100
 101         # see if this name is already defined, return it if so
 102         # FIXME: accessing internals of Bus
 103         if name in bus._bus_names:
 104             return bus._bus_names[name]
 105
 106         # otherwise register the name
 107         name_flags = (
 108             (allow_replacement and _dbus_bindings.NAME_FLAG_ALLOW_REPLACEMENT or 0) |
 109             (replace_existing and _dbus_bindings.NAME_FLAG_REPLACE_EXISTING or 0) |
 110             (do_not_queue and _dbus_bindings.NAME_FLAG_DO_NOT_QUEUE or 0))
 111
 112         retval = bus.request_name(name, name_flags)
 113
 114         # TODO: more intelligent tracking of bus name states?
 115         if retval == _dbus_bindings.REQUEST_NAME_REPLY_PRIMARY_OWNER:
 116             pass
 117         elif retval == _dbus_bindings.REQUEST_NAME_REPLY_IN_QUEUE:
 118             # queueing can happen by default, maybe we should
 119             # track this better or let the user know if they're
 120             # queued or not?
 121             pass
 122         elif retval == _dbus_bindings.REQUEST_NAME_REPLY_EXISTS:
 123             raise NameExistsException(name)
 124         elif retval == _dbus_bindings.REQUEST_NAME_REPLY_ALREADY_OWNER:
 125             # if this is a shared bus which is being used by someone
 126             # else in this process, this can happen legitimately
 127             pass
 128         else:
 129             raise RuntimeError('requesting bus name %s returned unexpected value %s' % (name, retval))
 130
 131         # and create the object
 132         bus_name = object.__new__(cls)
 133         bus_name._bus = bus
 134         bus_name._name = name
 135
 136         # cache instance (weak ref only)
 137         # FIXME: accessing Bus internals again
 138         bus._bus_names[name] = bus_name
 139
 140         return bus_name
 141
 142     # do nothing because this is called whether or not the bus name
 143     # object was retrieved from the cache or created new
 144     def __init__(self, *args, **keywords):
 145         pass
 146
 147     # we can delete the low-level name here because these objects
 148     # are guaranteed to exist only once for each bus name
 149     def __del__(self):
 150         self._bus.release_name(self._name)
 151         pass
 152
 153     def get_bus(self):
 154         """Get the Bus this Service is on"""
 155         return self._bus
 156
 157     def get_name(self):
 158         """Get the name of this service"""
 159         return self._name
 160
 161     def __repr__(self):
 162         return '<dbus.service.BusName %s on %r at %#x>' % (self._name, self._bus, id(self))
 163     __str__ = __repr__
 164
 165
 166 def _method_lookup(self, method_name, dbus_interface):
 167     """Walks the Python MRO of the given class to find the method to invoke.
 168
 169     Returns two methods, the one to call, and the one it inherits from which
 170     defines its D-Bus interface name, signature, and attributes.
 171     """
 172     parent_method = None
 173     candidate_class = None
 174     successful = False
 175
 176     # split up the cases when we do and don't have an interface because the
 177     # latter is much simpler
 178     if dbus_interface:
 179         # search through the class hierarchy in python MRO order
 180         for cls in self.__class__.__mro__:
 181             # if we haven't got a candidate class yet, and we find a class with a
 182             # suitably named member, save this as a candidate class
 183             if (not candidate_class and method_name in cls.__dict__):
 184                 if ("_dbus_is_method" in cls.__dict__[method_name].__dict__
 185                     and "_dbus_interface" in cls.__dict__[method_name].__dict__):
 186                     # however if it is annotated for a different interface
 187                     # than we are looking for, it cannot be a candidate
 188                     if cls.__dict__[method_name]._dbus_interface == dbus_interface:
 189                         candidate_class = cls
 190                         parent_method = cls.__dict__[method_name]
 191                         successful = True
 192                         break
 193                     else:
 194                         pass
 195                 else:
 196                     candidate_class = cls
 197
 198             # if we have a candidate class, carry on checking this and all
 199             # superclasses for a method annoated as a dbus method
 200             # on the correct interface
 201             if (candidate_class and method_name in cls.__dict__
 202                 and "_dbus_is_method" in cls.__dict__[method_name].__dict__
 203                 and "_dbus_interface" in cls.__dict__[method_name].__dict__
 204                 and cls.__dict__[method_name]._dbus_interface == dbus_interface):
 205                 # the candidate class has a dbus method on the correct interface,
 206                 # or overrides a method that is, success!
 207                 parent_method = cls.__dict__[method_name]
 208                 successful = True
 209                 break
 210
 211     else:
 212         # simpler version of above
 213         for cls in self.__class__.__mro__:
 214             if (not candidate_class and method_name in cls.__dict__):
 215                 candidate_class = cls
 216
 217             if (candidate_class and method_name in cls.__dict__
 218                 and "_dbus_is_method" in cls.__dict__[method_name].__dict__):
 219                 parent_method = cls.__dict__[method_name]
 220                 successful = True
 221                 break
 222
 223     if successful:
 224         return (candidate_class.__dict__[method_name], parent_method)
 225     else:
 226         if dbus_interface:
 227             raise UnknownMethodException('%s is not a valid method of interface %s' % (method_name, dbus_interface))
 228         else:
 229             raise UnknownMethodException('%s is not a valid method' % method_name)
 230
 231
 232 def _method_reply_return(connection, message, method_name, signature, *retval):
 233     reply = _dbus_bindings.MethodReturnMessage(message)
 234     try:
 235         reply.append(signature=signature, *retval)
 236     except Exception, e:
 237         logging.basicConfig()
 238         if signature is None:
 239             try:
 240                 signature = reply.guess_signature(retval) + ' (guessed)'
 241             except Exception, e:
 242                 _logger.error('Unable to guess signature for arguments %r: '
 243                               '%s: %s', retval, e.__class__, e)
 244                 raise
 245         _logger.error('Unable to append %r to message with signature %s: '
 246                       '%s: %s', retval, signature, e.__class__, e)
 247         raise
 248
 249     connection.send_message(reply)
 250
 251
 252 def _method_reply_error(connection, message, exception):
 253     name = getattr(exception, '_dbus_error_name', None)
 254
 255     if name is not None:
 256         pass
 257     elif getattr(exception, '__module__', '') in ('', '__main__'):
 258         name = 'org.freedesktop.DBus.Python.%s' % exception.__class__.__name__
 259     else:
 260         name = 'org.freedesktop.DBus.Python.%s.%s' % (exception.__module__, exception.__class__.__name__)
 261
 262     contents = traceback.format_exc()
 263     reply = _dbus_bindings.ErrorMessage(message, name, contents)
 264
 265     connection.send_message(reply)
 266
 267
 268 class InterfaceType(type):
 269     def __init__(cls, name, bases, dct):
 270         # these attributes are shared between all instances of the Interface
 271         # object, so this has to be a dictionary that maps class names to
 272         # the per-class introspection/interface data
 273         class_table = getattr(cls, '_dbus_class_table', {})
 274         cls._dbus_class_table = class_table
 275         interface_table = class_table[cls.__module__ + '.' + name] = {}
 276
 277         # merge all the name -> method tables for all the interfaces
 278         # implemented by our base classes into our own
 279         for b in bases:
 280             base_name = b.__module__ + '.' + b.__name__
 281             if getattr(b, '_dbus_class_table', False):
 282                 for (interface, method_table) in class_table[base_name].iteritems():
 283                     our_method_table = interface_table.setdefault(interface, {})
 284                     our_method_table.update(method_table)
 285
 286         # add in all the name -> method entries for our own methods/signals
 287         for func in dct.values():
 288             if getattr(func, '_dbus_interface', False):
 289                 method_table = interface_table.setdefault(func._dbus_interface, {})
 290                 method_table[func.__name__] = func
 291
 292         super(InterfaceType, cls).__init__(name, bases, dct)
 293
 294     # methods are different to signals, so we have two functions... :)
 295     def _reflect_on_method(cls, func):
 296         args = func._dbus_args
 297
 298         if func._dbus_in_signature:
 299             # convert signature into a tuple so length refers to number of
 300             # types, not number of characters. the length is checked by
 301             # the decorator to make sure it matches the length of args.
 302             in_sig = tuple(_dbus_bindings.Signature(func._dbus_in_signature))
 303         else:
 304             # magic iterator which returns as many v's as we need
 305             in_sig = _VariantSignature()
 306
 307         if func._dbus_out_signature:
 308             out_sig = _dbus_bindings.Signature(func._dbus_out_signature)
 309         else:
 310             # its tempting to default to _dbus_bindings.Signature('v'), but
 311             # for methods that return nothing, providing incorrect
 312             # introspection data is worse than providing none at all
 313             out_sig = []
 314
 315         reflection_data = '    <method name="%s">\n' % (func.__name__)
 316         for pair in zip(in_sig, args):
 317             reflection_data += '      <arg direction="in"  type="%s" name="%s" />\n' % pair
 318         for type in out_sig:
 319             reflection_data += '      <arg direction="out" type="%s" />\n' % type
 320         reflection_data += '    </method>\n'
 321
 322         return reflection_data
 323
 324     def _reflect_on_signal(cls, func):
 325         args = func._dbus_args
 326
 327         if func._dbus_signature:
 328             # convert signature into a tuple so length refers to number of
 329             # types, not number of characters
 330             sig = tuple(_dbus_bindings.Signature(func._dbus_signature))
 331         else:
 332             # magic iterator which returns as many v's as we need
 333             sig = _VariantSignature()
 334
 335         reflection_data = '    <signal name="%s">\n' % (func.__name__)
 336         for pair in zip(sig, args):
 337             reflection_data = reflection_data + '      <arg type="%s" name="%s" />\n' % pair
 338         reflection_data = reflection_data + '    </signal>\n'
 339
 340         return reflection_data
 341
 342 class Interface(object):
 343     __metaclass__ = InterfaceType
 344
 345 class Object(Interface):
 346     r"""A base class for exporting your own Objects across the Bus.
 347
 348     Just inherit from Object and mark exported methods with the
 349     @\ `dbus.service.method` or @\ `dbus.service.signal` decorator.
 350
 351     Example::
 352
 353         class Example(dbus.service.object):
 354             def __init__(self, object_path):
 355                 dbus.service.Object.__init__(self, dbus.SessionBus(), path)
 356                 self._last_input = None
 357
 358             @dbus.service.method(interface='com.example.Sample',
 359                                  in_signature='v', out_signature='s')
 360             def StringifyVariant(self, var):
 361                 self.LastInputChanged(var)      # emits the signal
 362                 return str(var)
 363
 364             @dbus.service.signal(interface='com.example.Sample',
 365                                  signature='v')
 366             def LastInputChanged(self, var):
 367                 # run just before the signal is actually emitted
 368                 # just put "pass" if nothing should happen
 369                 self._last_input = var
 370
 371             @dbus.service.method(interface='com.example.Sample',
 372                                  in_signature='', out_signature='v')
 373             def GetLastInput(self):
 374                 return self._last_input
 375     """
 376
 377     # the signature of __init__ is a bit mad, for backwards compatibility
 378     def __init__(self, conn=None, object_path=None, bus_name=None):
 379         """Constructor. Either conn or bus_name is required; object_path
 380         is also required.
 381
 382         :Parameters:
 383             `conn` : dbus.Connection
 384                 The connection on which to export this object.
 385
 386                 If None, use the Bus associated with the given ``bus_name``,
 387                 or raise TypeError if there is no ``bus_name`` either.
 388
 389                 For backwards compatibility, if an instance of
 390                 dbus.service.BusName is passed as the first parameter,
 391                 this is equivalent to passing its associated Bus as
 392                 ``conn``, and passing the BusName itself as ``bus_name``.
 393
 394             `object_path` : str
 395                 The D-Bus object path at which to export this Object.
 396
 397             `bus_name` : dbus.service.BusName
 398                 Represents a well-known name claimed by this process. A
 399                 reference to the BusName object will be held by this
 400                 Object, preventing the name from being released during this
 401                 Object's lifetime (unless it's released manually).
 402         """
 403         if object_path is None:
 404             raise TypeError('The object_path argument is required')
 405         _dbus_bindings.validate_object_path(object_path)
 406         if object_path == LOCAL_PATH:
 407             raise DBusException('Objects may not be exported on the reserved '
 408                                 'path %s' % LOCAL_PATH)
 409
 410         if isinstance(conn, BusName):
 411             # someone's using the old API; don't gratuitously break them
 412             bus_name = conn
 413             conn = bus_name.get_bus()
 414         elif conn is None:
 415             # someone's using the old API but naming arguments, probably
 416             if bus_name is None:
 417                 raise TypeError('Either conn or bus_name is required')
 418             conn = bus_name.get_bus()
 419
 420         self._object_path = object_path
 421         self._name = bus_name
 422         self._connection = conn
 423
 424         self._connection._register_object_path(object_path, self._message_cb, self._unregister_cb)
 425
 426     __dbus_object_path__ = property(lambda self: self._object_path, None, None,
 427                                     "The D-Bus object path of this object")
 428
 429     def _unregister_cb(self, connection):
 430         _logger.info('Unregistering exported object %r', self)
 431
 432     def _message_cb(self, connection, message):
 433         try:
 434             # lookup candidate method and parent method
 435             method_name = message.get_member()
 436             interface_name = message.get_interface()
 437             (candidate_method, parent_method) = _method_lookup(self, method_name, interface_name)
 438
 439             # set up method call parameters
 440             args = message.get_args_list(**parent_method._dbus_get_args_options)
 441             keywords = {}
 442
 443             if parent_method._dbus_out_signature is not None:
 444                 signature = _dbus_bindings.Signature(parent_method._dbus_out_signature)
 445             else:
 446                 signature = None
 447
 448             # set up async callback functions
 449             if parent_method._dbus_async_callbacks:
 450                 (return_callback, error_callback) = parent_method._dbus_async_callbacks
 451                 keywords[return_callback] = lambda *retval: _method_reply_return(connection, message, method_name, signature, *retval)
 452                 keywords[error_callback] = lambda exception: _method_reply_error(connection, message, exception)
 453
 454             # include the sender etc. if desired
 455             if parent_method._dbus_sender_keyword:
 456                 keywords[parent_method._dbus_sender_keyword] = message.get_sender()
 457             if parent_method._dbus_path_keyword:
 458                 keywords[parent_method._dbus_path_keyword] = message.get_path()
 459             if parent_method._dbus_destination_keyword:
 460                 keywords[parent_method._dbus_destination_keyword] = message.get_destination()
 461             if parent_method._dbus_message_keyword:
 462                 keywords[parent_method._dbus_message_keyword] = message
 463
 464             # call method
 465             retval = candidate_method(self, *args, **keywords)
 466
 467             # we're done - the method has got callback functions to reply with
 468             if parent_method._dbus_async_callbacks:
 469                 return
 470
 471             # otherwise we send the return values in a reply. if we have a
 472             # signature, use it to turn the return value into a tuple as
 473             # appropriate
 474             if signature is not None:
 475                 signature_tuple = tuple(signature)
 476                 # if we have zero or one return values we want make a tuple
 477                 # for the _method_reply_return function, otherwise we need
 478                 # to check we're passing it a sequence
 479                 if len(signature_tuple) == 0:
 480                     if retval == None:
 481                         retval = ()
 482                     else:
 483                         raise TypeError('%s has an empty output signature but did not return None' %
 484                             method_name)
 485                 elif len(signature_tuple) == 1:
 486                     retval = (retval,)
 487                 else:
 488                     if operator.isSequenceType(retval):
 489                         # multi-value signature, multi-value return... proceed unchanged
 490                         pass
 491                     else:
 492                         raise TypeError('%s has multiple output values in signature %s but did not return a sequence' %
 493                             (method_name, signature))
 494
 495             # no signature, so just turn the return into a tuple and send it as normal
 496             else:
 497                 if retval is None:
 498                     retval = ()
 499                 elif (isinstance(retval, tuple)
 500                       and not isinstance(retval, _dbus_bindings.Struct)):
 501                 # If the return is a tuple that is not a Struct, we use it
 502                 # as-is on the assumption that there are multiple return
 503                 # values - this is the usual Python idiom. (fd.o #10174)
 504                     pass
 505                 else:
 506                     retval = (retval,)
 507
 508             _method_reply_return(connection, message, method_name, signature, *retval)
 509         except Exception, exception:
 510             # send error reply
 511             _method_reply_error(connection, message, exception)
 512
 513     @method('org.freedesktop.DBus.Introspectable', in_signature='', out_signature='s')
 514     def Introspect(self):
 515         """Return a string of XML encoding this object's supported interfaces,
 516         methods and signals.
 517         """
 518         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'
 519         reflection_data += '<node name="%s">\n' % (self._object_path)
 520
 521         interfaces = self._dbus_class_table[self.__class__.__module__ + '.' + self.__class__.__name__]
 522         for (name, funcs) in interfaces.iteritems():
 523             reflection_data += '  <interface name="%s">\n' % (name)
 524
 525             for func in funcs.values():
 526                 if getattr(func, '_dbus_is_method', False):
 527                     reflection_data += self.__class__._reflect_on_method(func)
 528                 elif getattr(func, '_dbus_is_signal', False):
 529                     reflection_data += self.__class__._reflect_on_signal(func)
 530
 531             reflection_data += '  </interface>\n'
 532
 533         reflection_data += '</node>\n'
 534
 535         return reflection_data
 536
 537     def __repr__(self):
 538         return '<dbus.service.Object %s on %r at %#x>' % (self._object_path, self._name, id(self))
 539     __str__ = __repr__
 540