1 // Copyright 2014 The Chromium OS Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 #ifndef LIBBRILLO_BRILLO_DBUS_DBUS_SIGNAL_HANDLER_H_
6 #define LIBBRILLO_BRILLO_DBUS_DBUS_SIGNAL_HANDLER_H_
7
8 #include <string>
9
10 #include <brillo/bind_lambda.h>
11 #include <brillo/dbus/dbus_param_reader.h>
12 #include <dbus/message.h>
13 #include <dbus/object_proxy.h>
14
15 namespace brillo {
16 namespace dbus_utils {
17
18 // brillo::dbus_utils::ConnectToSignal() is a helper function similar to
19 // dbus::ObjectProxy::ConnectToSignal() but the |signal_callback| is an actual
20 // C++ signal handler with expected signal parameters as native method args.
21 //
22 // brillo::dbus_utils::ConnectToSignal() actually registers a stub signal
23 // handler with D-Bus which has a standard signature that matches
24 // dbus::ObjectProxy::SignalCallback.
25 //
26 // When a D-Bus signal is emitted, the stub handler is invoked, which unpacks
27 // the expected parameters from dbus::Signal message and then calls
28 // |signal_callback| with unpacked arguments.
29 //
30 // If the signal message doesn't contain correct number or types of arguments,
31 // an error message is logged to the system log and the signal is ignored
32 // (|signal_callback| is not invoked).
33 template<typename... Args>
ConnectToSignal(dbus::ObjectProxy * object_proxy,const std::string & interface_name,const std::string & signal_name,base::Callback<void (Args...)> signal_callback,dbus::ObjectProxy::OnConnectedCallback on_connected_callback)34 void ConnectToSignal(
35 dbus::ObjectProxy* object_proxy,
36 const std::string& interface_name,
37 const std::string& signal_name,
38 base::Callback<void(Args...)> signal_callback,
39 dbus::ObjectProxy::OnConnectedCallback on_connected_callback) {
40 // DBusParamReader::Invoke() needs a functor object, not a base::Callback.
41 // Wrap the callback with lambda so we can redirect the call.
42 auto signal_callback_wrapper = [signal_callback](const Args&... args) {
43 if (!signal_callback.is_null()) {
44 signal_callback.Run(args...);
45 }
46 };
47
48 // Raw signal handler stub method. When called, unpacks the signal arguments
49 // from |signal| message buffer and redirects the call to
50 // |signal_callback_wrapper| which, in turn, would call the user-provided
51 // |signal_callback|.
52 auto dbus_signal_callback = [signal_callback_wrapper](dbus::Signal* signal) {
53 dbus::MessageReader reader(signal);
54 DBusParamReader<false, Args...>::Invoke(
55 signal_callback_wrapper, &reader, nullptr);
56 };
57
58 // Register our stub handler with D-Bus ObjectProxy.
59 object_proxy->ConnectToSignal(interface_name,
60 signal_name,
61 base::Bind(dbus_signal_callback),
62 on_connected_callback);
63 }
64
65 } // namespace dbus_utils
66 } // namespace brillo
67
68 #endif // LIBBRILLO_BRILLO_DBUS_DBUS_SIGNAL_HANDLER_H_
69