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

dbus/bus.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef DBUS_BUS_H_
 #define DBUS_BUS_H_
 
 #include <dbus/dbus.h>
 
 #include <map>
@@ skipping 143 matching lines @@
   // PRIVATE gives you a private connection, that won't be shared with
   // other Bus objects.
   //
   // SHARED gives you a connection shared among other Bus objects, which
   // is unsafe if the connection is shared with multiple threads.
   enum ConnectionType {
     PRIVATE,
     SHARED,
   };
 
+  // Specifies whether the GetServiceOwnerAndBlock call should report or
+  // suppress errors.
+  enum GetServiceOwnerOption {
+    REPORT_ERRORS,
+    SUPPRESS_ERRORS,
+  };
+
   // Options used to create a Bus object.
   struct CHROME_DBUS_EXPORT Options {
     Options();
     ~Options();
 
     BusType bus_type;  // SESSION by default.
     ConnectionType connection_type;  // PRIVATE by default.
     // If dbus_task_runner is set, the bus object will use that
     // task runner to process asynchronous operations.
     //
@@ skipping 30 matching lines @@
 
   // Creates a Bus object. The actual connection will be established when
   // Connect() is called.
   explicit Bus(const Options& options);
 
   // Called when an ownership request is complete.
   // Parameters:
   // - the requested service name.
   // - whether ownership has been obtained or not.
   typedef base::Callback<void (const std::string&, bool)> OnOwnershipCallback;
+
+  // Called when GetServiceOwner() completes.
+  // |service_owner| is the return value from GetServiceOwnerAndBlock().
+  typedef base::Callback<void (const std::string& service_owner)>
+      GetServiceOwnerCallback;
+
   // TODO(satorux): Remove the service name parameter as the caller of
   // RequestOwnership() knows the service name.
 
   // Gets the object proxy for the given service name and the object path.
   // The caller must not delete the returned object.
   //
   // Returns an existing object proxy if the bus object already owns the
   // object proxy for the given service name and the object path.
   // Never returns NULL.
   //
@@ skipping 299 matching lines @@
 
   // Check whether the current thread is on the origin thread (the thread
   // that created the bus). If not, DCHECK will fail.
   virtual void AssertOnOriginThread();
 
   // Check whether the current thread is on the D-Bus thread. If not,
   // DCHECK will fail. If the D-Bus thread is not supplied, it calls
   // AssertOnOriginThread().
   virtual void AssertOnDBusThread();
 
+  // Gets the owner for |service_name| via org.freedesktop.DBus.GetNameOwner.
+  // Returns the owner name, if any, or an empty string on failure.
+  // |options| specifies where to printing error messages or not.
+  //
+  // BLOCKING CALL.
+  virtual std::string GetServiceOwnerAndBlock(const std::string& service_name,
+                                              GetServiceOwnerOption options);
+
+  // A non-blocking version of GetServiceOwnerAndBlock().
+  // Must be called in the origin thread.
+  virtual void GetServiceOwner(const std::string& service_name,
+                               const GetServiceOwnerCallback& callback);
+
   // Returns true if the bus is connected to D-Bus.
   bool is_connected() { return connection_ != NULL; }
 
  protected:
   // This is protected, so we can define sub classes.
   virtual ~Bus();
 
  private:
   friend class base::RefCountedThreadSafe<Bus>;
 
   // Helper function used for RemoveObjectProxy().
   void RemoveObjectProxyInternal(scoped_refptr<dbus::ObjectProxy> object_proxy,
                                  const base::Closure& callback);
 
   // Helper function used for UnregisterExportedObject().
   void UnregisterExportedObjectInternal(
       scoped_refptr<dbus::ExportedObject> exported_object);
 
   // Helper function used for ShutdownOnDBusThreadAndBlock().
   void ShutdownOnDBusThreadAndBlockInternal();
 
   // Helper function used for RequestOwnership().
   void RequestOwnershipInternal(const std::string& service_name,
                                 OnOwnershipCallback on_ownership_callback);
 
+  // Helper function used for GetServiceOwner().
+  void GetServiceOwnerInternal(const std::string& service_name,
+                               const GetServiceOwnerCallback& callback);
+
   // Processes the all incoming data to the connection, if any.
   //
   // BLOCKING CALL.
   void ProcessAllIncomingDataIfAny();
 
   // Called when a watch object is added. Used to start monitoring the
   // file descriptor used for D-Bus communication.
   dbus_bool_t OnAddWatch(DBusWatch* raw_watch);
 
   // Called when a watch object is removed.
@@ skipping 89 matching lines @@
 
   std::string address_;
   base::Closure on_disconnected_closure_;
 
   DISALLOW_COPY_AND_ASSIGN(Bus);
 };
 
 }  // namespace dbus
 
 #endif  // DBUS_BUS_H_