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