chrome: dbus: support asynchronous method replies

BUG=chromium-os:23241
TEST=Unit tests and manual testing on device.

Change-Id: Iab009ddbd12dea1e12299ae0ddccd4e430d9cf97


Review URL: http://codereview.chromium.org/8728020

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@112131 0039d316-1c4b-4281-b951-d872f2087c98

6 files changed, 117 insertions, 32 deletions

diff --git a/dbus/bus.h b/dbus/bus.h
index 89fba91..4af07ce 100644
--- a/dbus/bus.h
+++ b/dbus/bus.h
@@ -100,11 +100,15 @@ class ObjectProxy;
 //
 // Exporting a method:
 //
-//   Response* Echo(dbus::MethodCall* method_call) {
+//   void Echo(dbus::MethodCall* method_call,
+//             dbus::ExportedObject::ResponseSender response_sender) {
 //     // Do something with method_call.
 //     Response* response = Response::FromMethodCall(method_call);
 //     // Build response here.
-//     return response;
+//     // Can send an immediate response here to implement a synchronous service
+//     // or store the response_sender and send a response later to implement an
+//     // asynchronous service.
+//     response_sender.Run(response);
 //   }
 //
 //   void OnExported(const std::string& interface_name,
diff --git a/dbus/end_to_end_async_unittest.cc b/dbus/end_to_end_async_unittest.cc
index 2f486f4..5c98fe9 100644
--- a/dbus/end_to_end_async_unittest.cc
+++ b/dbus/end_to_end_async_unittest.cc
@@ -223,6 +223,24 @@ TEST_F(EndToEndAsyncTest, Timeout) {
   ASSERT_EQ("", response_strings_[0]);
 }
 
+// Tests calling a method that sends its reply asynchronously.
+TEST_F(EndToEndAsyncTest, AsyncEcho) {
+  const char* kHello = "hello";
+
+  // Create the method call.
+  dbus::MethodCall method_call("org.chromium.TestInterface", "AsyncEcho");
+  dbus::MessageWriter writer(&method_call);
+  writer.AppendString(kHello);
+
+  // Call the method.
+  const int timeout_ms = dbus::ObjectProxy::TIMEOUT_USE_DEFAULT;
+  CallMethod(&method_call, timeout_ms);
+
+  // Check the response.
+  WaitForResponses(1);
+  EXPECT_EQ(kHello, response_strings_[0]);
+}
+
 TEST_F(EndToEndAsyncTest, NonexistentMethod) {
   dbus::MethodCall method_call("org.chromium.TestInterface", "Nonexistent");
 
diff --git a/dbus/exported_object.cc b/dbus/exported_object.cc
index e4a1641..de25168 100644
--- a/dbus/exported_object.cc
+++ b/dbus/exported_object.cc
@@ -224,12 +224,13 @@ DBusHandlerResult ExportedObject::HandleMessage(
                                             method_call.release(),
                                             start_time));
   } else {
-    // If the D-Bus thread is not used, just call the method directly. We
-    // don't need the complicated logic to wait for the method call to be
-    // complete.
-    // |response| will be deleted in OnMethodCompleted().
-    Response* response = iter->second.Run(method_call.get());
-    OnMethodCompleted(method_call.release(), response, start_time);
+    // If the D-Bus thread is not used, just call the method directly.
+    MethodCall* released_method_call = method_call.release();
+    iter->second.Run(released_method_call,
+                     base::Bind(&ExportedObject::SendResponse,
+                                this,
+                                start_time,
+                                released_method_call));
   }
 
   // It's valid to say HANDLED here, and send a method response at a later
@@ -241,14 +242,27 @@ void ExportedObject::RunMethod(MethodCallCallback method_call_callback,
                                MethodCall* method_call,
                                base::TimeTicks start_time) {
   bus_->AssertOnOriginThread();
+  method_call_callback.Run(method_call,
+                           base::Bind(&ExportedObject::SendResponse,
+                                      this,
+                                      start_time,
+                                      method_call));
+}
 
-  Response* response = method_call_callback.Run(method_call);
-  bus_->PostTaskToDBusThread(FROM_HERE,
-                             base::Bind(&ExportedObject::OnMethodCompleted,
-                                        this,
-                                        method_call,
-                                        response,
-                                        start_time));
+void ExportedObject::SendResponse(base::TimeTicks start_time,
+                                  MethodCall* method_call,
+                                  Response* response) {
+  DCHECK(method_call);
+  if (bus_->HasDBusThread()) {
+    bus_->PostTaskToDBusThread(FROM_HERE,
+                               base::Bind(&ExportedObject::OnMethodCompleted,
+                                          this,
+                                          method_call,
+                                          response,
+                                          start_time));
+  } else {
+    OnMethodCompleted(method_call, response, start_time);
+  }
 }
 
 void ExportedObject::OnMethodCompleted(MethodCall* method_call,
diff --git a/dbus/exported_object.h b/dbus/exported_object.h
index bc67bcd..7ac2f88 100644
--- a/dbus/exported_object.h
+++ b/dbus/exported_object.h
@@ -38,9 +38,15 @@ class ExportedObject : public base::RefCountedThreadSafe<ExportedObject> {
                  const std::string& service_name,
                  const std::string& object_path);
 
+  // Called to send a response from an exported method. Response* is the
+  // response message. Callers should pass a NULL Response* in the event
+  // of an error that prevents the sending of a response.
+  typedef base::Callback<void (Response*)> ResponseSender;
+
   // Called when an exported method is called. MethodCall* is the request
-  // message.
-  typedef base::Callback<Response* (MethodCall*)> MethodCallCallback;
+  // message. ResponseSender is the callback that should be used to send a
+  // response.
+  typedef base::Callback<void (MethodCall*, ResponseSender)> MethodCallCallback;
 
   // Called when method exporting is done.
   // Parameters:
@@ -124,7 +130,14 @@ class ExportedObject : public base::RefCountedThreadSafe<ExportedObject> {
                  MethodCall* method_call,
                  base::TimeTicks start_time);
 
-  // Called on completion of the method run from RunMethod().
+  // Callback invoked by service provider to send a response to a method call.
+  // Can be called immediately from a MethodCallCallback to implement a
+  // synchronous service or called later to implement an asynchronous service.
+  void SendResponse(base::TimeTicks start_time,
+                    MethodCall* method_call,
+                    Response* response);
+
+  // Called on completion of the method run from SendResponse().
   // Takes ownership of |method_call| and |response|.
   void OnMethodCompleted(MethodCall* method_call,
                          Response* response,
diff --git a/dbus/test_service.cc b/dbus/test_service.cc
index b0207b0..ea8e360 100644
--- a/dbus/test_service.cc
+++ b/dbus/test_service.cc
@@ -13,8 +13,8 @@
 
 namespace dbus {
 
-// Echo, SlowEcho, BrokenMethod.
-const int TestService::kNumMethodsToExport = 3;
+// Echo, SlowEcho, AsyncEcho, BrokenMethod.
+const int TestService::kNumMethodsToExport = 4;
 
 TestService::Options::Options() {
 }
@@ -148,6 +148,15 @@ void TestService::Run(MessageLoop* message_loop) {
 
   exported_object_->ExportMethod(
       "org.chromium.TestInterface",
+      "AsyncEcho",
+      base::Bind(&TestService::AsyncEcho,
+                 base::Unretained(this)),
+      base::Bind(&TestService::OnExported,
+                 base::Unretained(this)));
+  ++num_methods;
+
+  exported_object_->ExportMethod(
+      "org.chromium.TestInterface",
       "BrokenMethod",
       base::Bind(&TestService::BrokenMethod,
                  base::Unretained(this)),
@@ -163,25 +172,44 @@ void TestService::Run(MessageLoop* message_loop) {
   message_loop->Run();
 }
 
-Response* TestService::Echo(MethodCall* method_call) {
+void TestService::Echo(MethodCall* method_call,
+                       dbus::ExportedObject::ResponseSender response_sender) {
   MessageReader reader(method_call);
   std::string text_message;
-  if (!reader.PopString(&text_message))
-    return NULL;
+  if (!reader.PopString(&text_message)) {
+    response_sender.Run(NULL);
+    return;
+  }
 
   Response* response = Response::FromMethodCall(method_call);
   MessageWriter writer(response);
   writer.AppendString(text_message);
-  return response;
+  response_sender.Run(response);
 }
 
-Response* TestService::SlowEcho(MethodCall* method_call) {
+void TestService::SlowEcho(
+    MethodCall* method_call,
+    dbus::ExportedObject::ResponseSender response_sender) {
   base::PlatformThread::Sleep(TestTimeouts::tiny_timeout_ms());
-  return Echo(method_call);
+  Echo(method_call, response_sender);
+}
+
+void TestService::AsyncEcho(
+    MethodCall* method_call,
+    dbus::ExportedObject::ResponseSender response_sender) {
+  // Schedule a call to Echo() to send an asynchronous response after we return.
+  message_loop()->PostDelayedTask(FROM_HERE,
+                                  base::Bind(&TestService::Echo,
+                                             base::Unretained(this),
+                                             method_call,
+                                             response_sender),
+                                  TestTimeouts::tiny_timeout_ms());
 }
 
-Response* TestService::BrokenMethod(MethodCall* method_call) {
-  return NULL;
+void TestService::BrokenMethod(
+    MethodCall* method_call,
+    dbus::ExportedObject::ResponseSender response_sender) {
+  response_sender.Run(NULL);
 }
 
 }  // namespace dbus
diff --git a/dbus/test_service.h b/dbus/test_service.h
index 153613e..ea3e5ad 100644
--- a/dbus/test_service.h
+++ b/dbus/test_service.h
@@ -10,6 +10,7 @@
 #include "base/memory/ref_counted.h"
 #include "base/threading/thread.h"
 #include "base/synchronization/waitable_event.h"
+#include "dbus/exported_object.h"
 
 namespace base {
 class MessageLoopProxy;
@@ -18,7 +19,6 @@ class MessageLoopProxy;
 namespace dbus {
 
 class Bus;
-class ExportedObject;
 class MethodCall;
 class Response;
 
@@ -89,14 +89,22 @@ class TestService : public base::Thread {
   //
 
   // Echos the text message received from the method call.
-  Response* Echo(MethodCall* method_call);
+  void Echo(MethodCall* method_call,
+            dbus::ExportedObject::ResponseSender response_sender);
 
   // Echos the text message received from the method call, but sleeps for
   // TestTimeouts::tiny_timeout_ms() before returning the response.
-  Response* SlowEcho(MethodCall* method_call);
+  void SlowEcho(MethodCall* method_call,
+                dbus::ExportedObject::ResponseSender response_sender);
+
+  // Echos the text message received from the method call, but sends its
+  // response asynchronously after this callback has returned.
+  void AsyncEcho(MethodCall* method_call,
+                 dbus::ExportedObject::ResponseSender response_sender);
 
   // Returns NULL, instead of a valid Response.
-  Response* BrokenMethod(MethodCall* method_call);
+  void BrokenMethod(MethodCall* method_call,
+                    dbus::ExportedObject::ResponseSender response_sender);
 
   scoped_refptr<base::MessageLoopProxy> dbus_thread_message_loop_proxy_;
   base::WaitableEvent on_all_methods_exported_;