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