Add a method to check if a D-Bus service has an owner. Use it for mtpd.

dbus/object_proxy.cc

Index: dbus/object_proxy.cc
===================================================================
--- dbus/object_proxy.cc	(revision 197157)
+++ dbus/object_proxy.cc	(working copy)
@@ -18,6 +18,8 @@
 #include "dbus/object_proxy.h"
 #include "dbus/scoped_dbus_error.h"
 
+namespace dbus {
+
 namespace {
 
 const char kErrorServiceUnknown[] = "org.freedesktop.DBus.Error.ServiceUnknown";
@@ -28,6 +30,15 @@
 // The path of D-Bus Object sending NameOwnerChanged signal.
 const char kDBusSystemObjectPath[] = "/org/freedesktop/DBus";
 
+// The D-Bus Object interface.
+const char kDBusSystemObjectInterface[] = "org.freedesktop.DBus";
+
+// The D-Bus Object address.
+const char kDBusSystemObjectAddress[] = "org.freedesktop.DBus";
+
+// The NameOwnerChanged member in |kDBusSystemObjectInterface|.
+const char kNameOwnerChangedMember[] = "NameOwnerChanged";
+
 // Gets the absolute signal name by concatenating the interface name and
 // the signal name. Used for building keys for method_table_ in
 // ObjectProxy.
@@ -38,13 +49,54 @@
 }
 
 // An empty function used for ObjectProxy::EmptyResponseCallback().
-void EmptyResponseCallbackBody(dbus::Response* unused_response) {
+void EmptyResponseCallbackBody(Response* unused_response) {
 }
 
+// Gets the owner for |service_name| on |bus|. On success, returns true and
+// write the owner name to |service_name_owner|.
+// Set |suppress_errors| to true to avoid printing error messages.
+bool GetServiceOwner(Bus* bus,
+                     const std::string& service_name,
+                     bool suppress_errors,
+                     std::string* service_name_owner) {
+  bus->AssertOnDBusThread();
+
+  MethodCall get_name_owner_call(kDBusSystemObjectInterface, "GetNameOwner");
+  MessageWriter writer(&get_name_owner_call);
+  writer.AppendString(service_name);
+  VLOG(1) << "Method call: " << get_name_owner_call.ToString();
+
+  const ObjectPath obj_path(kDBusSystemObjectPath);
+  if (!get_name_owner_call.SetDestination(kDBusSystemObjectAddress) ||
+      !get_name_owner_call.SetPath(obj_path)) {
+    if (!suppress_errors)
+      LOG(ERROR) << "Failed to get name owner.";
+    return false;
+  }
+
+  ScopedDBusError error;
+  DBusMessage* response_message = bus->SendWithReplyAndBlock(
+      get_name_owner_call.raw_message(),
+      ObjectProxy::TIMEOUT_USE_DEFAULT,
+      error.get());
+  if (!response_message) {
+    if (!suppress_errors) {
+      LOG(ERROR) << "Failed to get name owner. Got " << error.name() << ": "
+                 << error.message();
+    }
+    return false;
+  }
+
+  scoped_ptr<Response> response(Response::FromRawMessage(response_message));
+  MessageReader reader(response.get());
+
+  if (!reader.PopString(service_name_owner))
+    service_name_owner->clear();
+  return true;
+}
+
 }  // namespace
 
-namespace dbus {
-
 ObjectProxy::ObjectProxy(Bus* bus,
                          const std::string& service_name,
                          const ObjectPath& object_path,
@@ -193,6 +245,18 @@
 }
 
 // static
+bool ObjectProxy::ServiceHasOwner(dbus::Bus* bus,
+                                  const std::string& service_name) {

[satorux1, 2013/04/30 01:53:10]

thread checking is missing. bus_->AssertOnDBusThread() ?

+  if (!bus->Connect())
+    return false;
+
+  std::string service_name_owner;
+  if (!GetServiceOwner(bus, service_name, true, &service_name_owner))
+    return false;
+  return !service_name_owner.empty();
+}
+
+// static
 ObjectProxy::ResponseCallback ObjectProxy::EmptyResponseCallback() {
   return base::Bind(&EmptyResponseCallbackBody);
 }
@@ -285,18 +349,17 @@
   } else if (dbus_message_get_type(response_message) ==
              DBUS_MESSAGE_TYPE_ERROR) {
     // This will take |response_message| and release (unref) it.
-    scoped_ptr<dbus::ErrorResponse> error_response(
-        dbus::ErrorResponse::FromRawMessage(response_message));
+    scoped_ptr<ErrorResponse> error_response(
+        ErrorResponse::FromRawMessage(response_message));
     error_callback.Run(error_response.get());
     // Delete the message  on the D-Bus thread. See below for why.
     bus_->PostTaskToDBusThread(
         FROM_HERE,
-        base::Bind(&base::DeletePointer<dbus::ErrorResponse>,
+        base::Bind(&base::DeletePointer<ErrorResponse>,
                    error_response.release()));
   } else {
     // This will take |response_message| and release (unref) it.
-    scoped_ptr<dbus::Response> response(
-        dbus::Response::FromRawMessage(response_message));
+    scoped_ptr<Response> response(Response::FromRawMessage(response_message));
     // The response is successfully received.
     response_callback.Run(response.get());
     // The message should be deleted on the D-Bus thread for a complicated
@@ -319,8 +382,7 @@
     // thread, not from the current thread here, which is likely UI thread.
     bus_->PostTaskToDBusThread(
         FROM_HERE,
-        base::Bind(&base::DeletePointer<dbus::Response>,
-                   response.release()));
+        base::Bind(&base::DeletePointer<Response>, response.release()));
 
     method_call_successful = true;
     // Record time spent for the method call. Don't include failures.
@@ -439,10 +501,10 @@
   // Verify the signal comes from the object we're proxying for, this is
   // our last chance to return DBUS_HANDLER_RESULT_NOT_YET_HANDLED and
   // allow other object proxies to handle instead.
-  const dbus::ObjectPath path = signal->GetPath();
+  const ObjectPath path = signal->GetPath();
   if (path != object_path_) {
     if (path.value() == kDBusSystemObjectPath &&
-        signal->GetMember() == "NameOwnerChanged") {
+        signal->GetMember() == kNameOwnerChangedMember) {
       // Handle NameOwnerChanged separately
       return HandleNameOwnerChanged(signal.Pass());
     }
@@ -507,7 +569,7 @@
   // RunResponseCallback().
   bus_->PostTaskToDBusThread(
       FROM_HERE,
-      base::Bind(&base::DeletePointer<dbus::Signal>, signal));
+      base::Bind(&base::DeletePointer<Signal>, signal));
 
   // Record time spent for handling the signal.
   UMA_HISTOGRAM_TIMES("DBus.SignalHandleTime",
@@ -541,7 +603,7 @@
                                     ErrorResponse* error_response) {
   if (error_response) {
     // Error message may contain the error message as string.
-    dbus::MessageReader reader(error_response);
+    MessageReader reader(error_response);
     std::string error_message;
     reader.PopString(&error_message);
     LogMethodCallFailure(interface_name,
@@ -564,8 +626,8 @@
     ScopedDBusError error;
     bus_->AddMatch(match_rule, error.get());
     if (error.is_set()) {
-      LOG(ERROR) << "Failed to add match rule \"" << match_rule << "\". Got " <<
-          error.name() << ": " << error.message();
+      LOG(ERROR) << "Failed to add match rule \"" << match_rule << "\". Got "
+                 << error.name() << ": " << error.message();
       return false;
     } else {
       // Store the match rule, so that we can remove this in Detach().
@@ -594,8 +656,8 @@
   ScopedDBusError error;
   bus_->AddMatch(match_rule, error.get());
   if (error.is_set()) {
-    LOG(ERROR) << "Failed to add match rule \"" << match_rule << "\". Got " <<
-        error.name() << ": " << error.message();
+    LOG(ERROR) << "Failed to add match rule \"" << match_rule << "\". Got "
+               << error.name() << ": " << error.message();
     return false;
   }
   // Store the match rule, so that we can remove this in Detach().
@@ -604,38 +666,7 @@
 }
 
 void ObjectProxy::UpdateNameOwnerAndBlock() {
-  bus_->AssertOnDBusThread();
-
-  MethodCall get_name_owner_call("org.freedesktop.DBus", "GetNameOwner");
-  MessageWriter writer(&get_name_owner_call);
-  writer.AppendString(service_name_);
-  VLOG(1) << "Method call: " << get_name_owner_call.ToString();
-
-  const dbus::ObjectPath obj_path("/org/freedesktop/DBus");
-  ScopedDBusError error;
-  if (!get_name_owner_call.SetDestination("org.freedesktop.DBus") ||
-      !get_name_owner_call.SetPath(obj_path)) {
-    LOG(ERROR) << "Failed to get name owner.";
-    return;
-  }
-
-  DBusMessage* response_message = bus_->SendWithReplyAndBlock(
-      get_name_owner_call.raw_message(),
-      TIMEOUT_USE_DEFAULT,
-      error.get());
-  if (!response_message) {
-    LOG(ERROR) << "Failed to get name owner. Got " << error.name() << ": " <<
-        error.message();
-    return;
-  }
-  scoped_ptr<Response> response(Response::FromRawMessage(response_message));
-  MessageReader reader(response.get());
-
-  std::string new_service_name_owner;
-  if (reader.PopString(&new_service_name_owner))
-    service_name_owner_ = new_service_name_owner;
-  else
-    service_name_owner_.clear();
+  GetServiceOwner(bus_, service_name_, false, &service_name_owner_);
 }
 
 DBusHandlerResult ObjectProxy::HandleNameOwnerChanged(
@@ -644,9 +675,9 @@
   bus_->AssertOnDBusThread();
 
   // Confirm the validity of the NameOwnerChanged signal.
-  if (signal->GetMember() == "NameOwnerChanged" &&
-      signal->GetInterface() == "org.freedesktop.DBus" &&
-      signal->GetSender() == "org.freedesktop.DBus") {
+  if (signal->GetMember() == kNameOwnerChangedMember &&
+      signal->GetInterface() == kDBusSystemObjectInterface &&
+      signal->GetSender() == kDBusSystemObjectAddress) {
     MessageReader reader(signal.get());
     std::string name, old_owner, new_owner;
     if (reader.PopString(&name) &&