libbrillo: Support custom D-Bus property handlers

This CL is to allow clients of DBusObject to implement their own custom
property method handlers (GetAll/Get/Set). Possible use cases include:
* handling Set method call to be forwarded to another D-Bus service
* handling Set method call to trigger some operation other than setting
  the property value itself.
* handling Get method call to return a value which is a function of
  other properties' values.

BUG=chromium:812468
TEST=Tested with Bluetooth daemon that forwards Set method call.

Change-Id: I8294dc46885b2105adceb9c144f4d603185e49ff
Reviewed-on: https://chromium-review.googlesource.com/939263
Commit-Ready: Sonny Sasaka <sonnysasaka@chromium.org>
Tested-by: Sonny Sasaka <sonnysasaka@chromium.org>
Reviewed-by: Ben Chan <benchan@chromium.org>

2 files changed, 49 insertions, 13 deletions

diff --git a/brillo/dbus/dbus_object.cc b/brillo/dbus/dbus_object.cc
index 5172dc6..15bcddd 100644
--- a/brillo/dbus/dbus_object.cc
+++ b/brillo/dbus/dbus_object.cc
@@ -16,6 +16,23 @@
 namespace brillo {
 namespace dbus_utils {
 
+namespace {
+
+void SetupDefaultPropertyHandlers(DBusInterface* prop_interface,
+                                  ExportedPropertySet* property_set) {
+  prop_interface->AddSimpleMethodHandler(dbus::kPropertiesGetAll,
+                                         base::Unretained(property_set),
+                                         &ExportedPropertySet::HandleGetAll);
+  prop_interface->AddSimpleMethodHandlerWithError(
+      dbus::kPropertiesGet, base::Unretained(property_set),
+      &ExportedPropertySet::HandleGet);
+  prop_interface->AddSimpleMethodHandlerWithError(
+      dbus::kPropertiesSet, base::Unretained(property_set),
+      &ExportedPropertySet::HandleSet);
+}
+
+}  // namespace
+
 //////////////////////////////////////////////////////////////////////////////
 
 DBusInterface::DBusInterface(DBusObject* dbus_object,
@@ -152,7 +169,21 @@ void DBusInterface::AddSignalImpl(
 DBusObject::DBusObject(ExportedObjectManager* object_manager,
                        const scoped_refptr<dbus::Bus>& bus,
                        const dbus::ObjectPath& object_path)
-    : property_set_(bus.get()), bus_(bus), object_path_(object_path) {
+    : DBusObject::DBusObject(object_manager,
+                             bus,
+                             object_path,
+                             base::Bind(&SetupDefaultPropertyHandlers)) {}
+
+DBusObject::DBusObject(
+    ExportedObjectManager* object_manager,
+    const scoped_refptr<dbus::Bus>& bus,
+    const dbus::ObjectPath& object_path,
+    PropertyHandlerSetupCallback property_handler_setup_callback)
+    : property_set_(bus.get()),
+      bus_(bus),
+      object_path_(object_path),
+      property_handler_setup_callback_(
+          std::move(property_handler_setup_callback)) {
   if (object_manager)
     object_manager_ = object_manager->AsWeakPtr();
 }
@@ -249,18 +280,7 @@ bool DBusObject::SendSignal(dbus::Signal* signal) {
 
 void DBusObject::RegisterPropertiesInterface() {
   DBusInterface* prop_interface = AddOrGetInterface(dbus::kPropertiesInterface);
-  prop_interface->AddSimpleMethodHandler(
-      dbus::kPropertiesGetAll,
-      base::Unretained(&property_set_),
-      &ExportedPropertySet::HandleGetAll);
-  prop_interface->AddSimpleMethodHandlerWithError(
-      dbus::kPropertiesGet,
-      base::Unretained(&property_set_),
-      &ExportedPropertySet::HandleGet);
-  prop_interface->AddSimpleMethodHandlerWithError(
-      dbus::kPropertiesSet,
-      base::Unretained(&property_set_),
-      &ExportedPropertySet::HandleSet);
+  property_handler_setup_callback_.Run(prop_interface, &property_set_);
   property_set_.OnPropertiesInterfaceExported(prop_interface);
 }
 
diff --git a/brillo/dbus/dbus_object.h b/brillo/dbus/dbus_object.h
index e7c59e3..48f09ff 100644
--- a/brillo/dbus/dbus_object.h
+++ b/brillo/dbus/dbus_object.h
@@ -507,6 +507,9 @@ class BRILLO_EXPORT DBusInterface final {
 // by this object.
 class BRILLO_EXPORT DBusObject {
  public:
+  using PropertyHandlerSetupCallback = base::Callback<void(
+      DBusInterface* prop_interface, ExportedPropertySet* property_set)>;
+
   // object_manager - ExportedObjectManager instance that notifies D-Bus
   //                  listeners of a new interface being claimed and property
   //                  changes on those interfaces.
@@ -514,6 +517,17 @@ class BRILLO_EXPORT DBusObject {
   DBusObject(ExportedObjectManager* object_manager,
              const scoped_refptr<dbus::Bus>& bus,
              const dbus::ObjectPath& object_path);
+
+  // property_handler_setup_callback - To be called when setting up property
+  //                                   method handlers. Clients can register
+  //                                   their own custom property method handlers
+  //                                   (GetAll/Get/Set) by passing in this
+  //                                   callback.
+  DBusObject(ExportedObjectManager* object_manager,
+             const scoped_refptr<dbus::Bus>& bus,
+             const dbus::ObjectPath& object_path,
+             PropertyHandlerSetupCallback property_handler_setup_callback);
+
   virtual ~DBusObject();
 
   // Returns an proxy handler for the interface |interface_name|. If the
@@ -571,6 +585,8 @@ class BRILLO_EXPORT DBusObject {
   dbus::ObjectPath object_path_;
   // D-Bus object instance once this object is successfully exported.
   dbus::ExportedObject* exported_object_ = nullptr;  // weak; owned by |bus_|.
+  // Sets up property method handlers.
+  PropertyHandlerSetupCallback property_handler_setup_callback_;
 
   friend class DBusInterface;
   DISALLOW_COPY_AND_ASSIGN(DBusObject);