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"""Module for high-level communication over the FreeDesktop.org Bus (DBus)
DBus allows you to share and access remote objects between processes
running on the desktop, and also to access system services (such as
the print spool).
To use DBus, first get a Bus object, which provides a connection to one
of a few standard dbus-daemon instances that might be running. From the
Bus you can get a RemoteService. A service is provided by an application or
process connected to the Bus, and represents a set of objects. Once you
have a RemoteService you can get a RemoteObject that implements a specific interface
(an interface is just a standard group of member functions). Then you can call
those member functions directly.
You can think of a complete method call as looking something like:
Bus:SESSION -> Service:org.gnome.Evolution -> Object:/org/gnome/Evolution/Inbox -> Interface: org.gnome.Evolution.MailFolder -> Method: Forward('message1', 'seth@gnome.org')
This communicates over the SESSION Bus to the org.gnome.Evolution process to call the
Forward method of the /org/gnome/Evolution/Inbox object (which provides the
org.gnome.Evolution.MailFolder interface) with two string arguments.
For example, the dbus-daemon itself provides a service and some objects:
# Get a connection to the desktop-wide SESSION bus
bus = dbus.Bus(dbus.Bus.TYPE_SESSION)
# Get the service provided by the dbus-daemon named org.freedesktop.DBus
dbus_service = bus.get_service('org.freedesktop.DBus')
# Get a reference to the desktop bus' standard object, denoted
# by the path /org/freedesktop/DBus. The object /org/freedesktop/DBus
# implements the 'org.freedesktop.DBus' interface
dbus_object = dbus_service.get_object('/org/freedesktop/DBus',
'org.freedesktop.DBus')
# One of the member functions in the org.freedesktop.DBus interface
# is ListServices(), which provides a list of all the other services
# registered on this bus. Call it, and print the list.
print(dbus_object.ListServices())
"""
import dbus
import dbus_bindings
import weakref
from proxies import *
from exceptions import *
from matchrules import *
class Bus(object):
"""A connection to a DBus daemon.
One of three possible standard buses, the SESSION, SYSTEM,
or STARTER bus
"""
TYPE_SESSION = dbus_bindings.BUS_SESSION
TYPE_SYSTEM = dbus_bindings.BUS_SYSTEM
TYPE_STARTER = dbus_bindings.BUS_STARTER
"""bus_type=[Bus.TYPE_SESSION | Bus.TYPE_SYSTEM | Bus.TYPE_STARTER]
"""
ProxyObjectClass = ProxyObject
START_REPLY_SUCCESS = dbus_bindings.DBUS_START_REPLY_SUCCESS
START_REPLY_ALREADY_RUNNING = dbus_bindings.DBUS_START_REPLY_ALREADY_RUNNING
_shared_instances = weakref.WeakValueDictionary()
def __new__(cls, bus_type=TYPE_SESSION, use_default_mainloop=True, private=False):
if (not private and bus_type in cls._shared_instances):
return cls._shared_instances[bus_type]
# this is a bit odd, but we create instances of the subtypes
# so we can return the shared instances if someone tries to
# construct one of them (otherwise we'd eg try and return an
# instance of Bus from __new__ in SessionBus). why are there
# three ways to construct this class? we just don't know.
if bus_type == cls.TYPE_SESSION:
subclass = SessionBus
elif bus_type == cls.TYPE_SYSTEM:
subclass = SystemBus
elif bus_type == cls.TYPE_STARTER:
subclass = StarterBus
else:
raise ValueError('invalid bus_type %s' % bus_type)
bus = object.__new__(subclass)
bus._bus_type = bus_type
bus._bus_names = weakref.WeakValueDictionary()
bus._match_rule_tree = SignalMatchTree()
# FIXME: if you get a starter and a system/session bus connection
# in the same process, it's the same underlying connection that
# is returned by bus_get, but we initialise it twice
bus._connection = dbus_bindings.bus_get(bus_type, private)
bus._connection.add_filter(bus._signal_func)
if use_default_mainloop:
func = getattr(dbus, "_dbus_mainloop_setup_function", None)
if func:
func(bus)
if not private:
cls._shared_instances[bus_type] = bus
return bus
def __init__(self, *args, **keywords):
# do nothing here because this can get called multiple times on the
# same object if __new__ returns a shared instance
pass
def close(self):
self._connection.close()
def get_connection(self):
return self._connection
def get_session(private=False):
"""Static method that returns the session bus"""
return SessionBus(private=private)
get_session = staticmethod(get_session)
def get_system(private=False):
"""Static method that returns the system bus"""
return SystemBus(private=private)
get_system = staticmethod(get_system)
def get_starter(private=False):
"""Static method that returns the starter bus"""
return StarterBus(private=private)
get_starter = staticmethod(get_starter)
def get_object(self, named_service, object_path):
"""Get a proxy object to call over the bus"""
return self.ProxyObjectClass(self, named_service, object_path)
def _create_args_dict(self, keywords):
args_dict = None
for (key, value) in keywords.iteritems():
if key.startswith('arg'):
try:
snum = key[3:]
num = int(snum)
if not args_dict:
args_dict = {}
args_dict[num] = value
except ValueError:
raise TypeError("Invalid arg index %s"%snum)
elif key in ("sender_keyword", "path_keyword"):
pass
else:
raise TypeError("Unknown keyword %s"%(key))
return args_dict
def add_signal_receiver(self, handler_function,
signal_name=None,
dbus_interface=None,
named_service=None,
path=None,
**keywords):
args_dict = self._create_args_dict(keywords)
if (named_service and named_service[0] != ':'):
bus_object = self.get_object('org.freedesktop.DBus', '/org/freedesktop/DBus')
named_service = bus_object.GetNameOwner(named_service, dbus_interface='org.freedesktop.DBus')
match_rule = SignalMatchRule(signal_name, dbus_interface, named_service, path)
for kw in ("sender_keyword", "path_keyword"):
if kw in keywords:
setattr(match_rule, kw, keywords[kw])
else:
setattr(match_rule, kw, None)
if args_dict:
match_rule.add_args_match(args_dict)
match_rule.add_handler(handler_function)
self._match_rule_tree.add(match_rule)
dbus_bindings.bus_add_match(self._connection, repr(match_rule))
def remove_signal_receiver(self, handler_function,
signal_name=None,
dbus_interface=None,
named_service=None,
path=None,
**keywords):
args_dict = self._create_args_dict(keywords)
if (named_service and named_service[0] != ':'):
bus_object = self.get_object('org.freedesktop.DBus', '/org/freedesktop/DBus')
named_service = bus_object.GetNameOwner(named_service, dbus_interface='org.freedesktop.DBus')
match_rule = SignalMatchRule(signal_name, dbus_interface, named_service, path)
if (args_dict):
match_rule.add_args_match(args_dict)
if (handler_function):
match_rule.add_handler(handler_function)
self._match_rule_tree.remove(match_rule)
#TODO we leak match rules in the lower level bindings. We need to ref count them
def get_unix_user(self, named_service):
"""Get the unix user for the given named_service on this Bus"""
return dbus_bindings.bus_get_unix_user(self._connection, named_service)
def _signal_func(self, connection, message):
if (message.get_type() != dbus_bindings.MESSAGE_TYPE_SIGNAL):
return dbus_bindings.HANDLER_RESULT_NOT_YET_HANDLED
dbus_interface = message.get_interface()
named_service = message.get_sender()
path = message.get_path()
signal_name = message.get_member()
match_rule = SignalMatchRule(signal_name, dbus_interface, named_service, path)
self._match_rule_tree.exec_matches(match_rule, message)
def start_service_by_name(self, named_service):
return dbus_bindings.bus_start_service_by_name(self._connection, named_service)
def __repr__(self):
if self._bus_type == self.TYPE_SESSION:
name = 'SESSION'
elif self._bus_type == self.TYPE_SYSTEM:
name = 'SYSTEM'
elif self._bus_type == self.TYPE_STARTER:
name = 'STARTER'
else:
assert False, 'Unable to represent unknown bus type.'
return '<dbus.Bus on %s at %#x>' % (name, id(self))
__str__ = __repr__
class SystemBus(Bus):
"""The system-wide message bus
"""
def __new__(cls, use_default_mainloop=True, private=False):
return Bus.__new__(cls, Bus.TYPE_SYSTEM, use_default_mainloop, private)
class SessionBus(Bus):
"""The session (current login) message bus
"""
def __new__(cls, use_default_mainloop=True, private=False):
return Bus.__new__(cls, Bus.TYPE_SESSION, use_default_mainloop, private)
class StarterBus(Bus):
"""The bus that activated this process (if
this process was launched by DBus activation)
"""
def __new__(cls, use_default_mainloop=True, private=False):
return Bus.__new__(cls, Bus.TYPE_STARTER, use_default_mainloop, private)
class Interface:
"""An interface into a remote object
An Interface can be used to wrap ProxyObjects
so that calls can be routed to their correct
dbus interface
"""
def __init__(self, object, dbus_interface):
self._obj = object
self._dbus_interface = dbus_interface
def connect_to_signal(self, signal_name, handler_function, dbus_interface = None, **keywords):
if not dbus_interface:
dbus_interface = self._dbus_interface
self._obj.connect_to_signal(signal_name, handler_function, dbus_interface, **keywords)
def __getattr__(self, member, **keywords):
if (keywords.has_key('dbus_interface')):
_dbus_interface = keywords['dbus_interface']
else:
_dbus_interface = self._dbus_interface
if member == '__call__':
return object.__call__
else:
ret = self._obj.__getattr__(member, dbus_interface=_dbus_interface)
return ret
def __repr__(self):
return '<Interface %r implementing %r at %#x>'%(
self._obj, self._dbus_interface, id(self))
__str__ = __repr__
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