Mojo: introducing a thread safe interface pointer.

mojo/public/cpp/bindings/lib/interface_ptr_state.h

 // Copyright 2014 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 MOJO_PUBLIC_CPP_BINDINGS_LIB_INTERFACE_PTR_STATE_H_
 #define MOJO_PUBLIC_CPP_BINDINGS_LIB_INTERFACE_PTR_STATE_H_
 
 #include <stdint.h>
 
 #include <algorithm>  // For |std::swap()|.
 #include <memory>
 #include <string>
 #include <utility>
 
 #include "base/bind.h"
 #include "base/callback_forward.h"
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
 #include "base/memory/ref_counted.h"
+#include "base/memory/weak_ptr.h"
 #include "base/single_thread_task_runner.h"
 #include "mojo/public/cpp/bindings/associated_group.h"
 #include "mojo/public/cpp/bindings/connection_error_callback.h"
 #include "mojo/public/cpp/bindings/filter_chain.h"
 #include "mojo/public/cpp/bindings/interface_endpoint_client.h"
 #include "mojo/public/cpp/bindings/interface_id.h"
 #include "mojo/public/cpp/bindings/interface_ptr_info.h"
 #include "mojo/public/cpp/bindings/lib/control_message_handler.h"
 #include "mojo/public/cpp/bindings/lib/control_message_proxy.h"
 #include "mojo/public/cpp/bindings/lib/multiplex_router.h"
@@ skipping 171 matching lines @@
   uint32_t version_;
 
   DISALLOW_COPY_AND_ASSIGN(InterfacePtrState);
 };
 
 // Uses a multiplexing router. If |Interface| has methods to pass associated
 // interface pointers or requests, this specialization should be used.
 template <typename Interface>
 class InterfacePtrState<Interface, true> {
  public:
-  InterfacePtrState() : version_(0u) {}
+  InterfacePtrState() : version_(0u), weak_ptr_factory_(this) {}
 
   ~InterfacePtrState() {
     endpoint_client_.reset();
     proxy_.reset();
     if (router_)
       router_->CloseMessagePipe();
   }
 
   Interface* instance() {
     ConfigureProxyIfNecessary();
@@ skipping 101 matching lines @@
   AssociatedGroup* associated_group() {
     ConfigureProxyIfNecessary();
     return endpoint_client_->associated_group();
   }
 
   void EnableTestingMode() {
     ConfigureProxyIfNecessary();
     router_->EnableTestingMode();
   }
 
+  base::Callback<void(Message)> GetThreadSafePtrAcceptCallback() {
+    return base::Bind(&InterfacePtrState::ForwardMessage,
+                      weak_ptr_factory_.GetWeakPtr());
+  }
+
+  base::Callback<void(Message, std::unique_ptr<MessageReceiver>)>
+  GetThreadSafePtrAcceptWithResponderCallback() {
+    return base::Bind(&InterfacePtrState::ForwardMessageWithResponder,
+                      weak_ptr_factory_.GetWeakPtr());
+  }
+
  private:
   using Proxy = typename Interface::Proxy_;
 
   void ConfigureProxyIfNecessary() {
     // The proxy has been configured.
     if (proxy_) {
       DCHECK(router_);
       DCHECK(endpoint_client_);
       return;
     }
@@ skipping 10 matching lines @@
     router_ = new MultiplexRouter(std::move(handle_), config, true, runner_);
     router_->SetMasterInterfaceName(Interface::Name_);
     endpoint_client_.reset(new InterfaceEndpointClient(
         router_->CreateLocalEndpointHandle(kMasterInterfaceId), nullptr,
         base::WrapUnique(new typename Interface::ResponseValidator_()), false,
         std::move(runner_),
         // The version is only queried from the client so the value passed here
         // will not be used.
         0u));
     proxy_.reset(new Proxy(endpoint_client_.get()));
-    if (Interface::PassesAssociatedKinds_) {
-      proxy_->serialization_context()->group_controller =
-          endpoint_client_->group_controller();
-    }
+    if (Interface::PassesAssociatedKinds_)
+      proxy_->set_group_controller(endpoint_client_->group_controller());
   }
 
   void OnQueryVersion(const base::Callback<void(uint32_t)>& callback,
                       uint32_t version) {
     version_ = version;
     callback.Run(version);
   }
 
+  void ForwardMessage(Message message) {
+    ConfigureProxyIfNecessary();
+    endpoint_client_->Accept(&message);
+  }
+
+  void ForwardMessageWithResponder(Message message,
+                                   std::unique_ptr<MessageReceiver> responder) {
+    ConfigureProxyIfNecessary();
+    endpoint_client_->AcceptWithResponder(&message, responder.release());
+  }
+
   scoped_refptr<MultiplexRouter> router_;
 
   std::unique_ptr<InterfaceEndpointClient> endpoint_client_;
   std::unique_ptr<Proxy> proxy_;
 
   // |router_| (as well as other members above) is not initialized until
   // read/write with the message pipe handle is needed. |handle_| is valid
   // between the Bind() call and the initialization of |router_|.
   ScopedMessagePipeHandle handle_;
   scoped_refptr<base::SingleThreadTaskRunner> runner_;
 
   uint32_t version_;
 
+  base::WeakPtrFactory<InterfacePtrState> weak_ptr_factory_;

[yzshen1, 2016/11/15 18:53:46]

It is not needed in the majority case. Does it make sense to only construct it
on demand?

[Jay Civelli, 2016/11/15 19:36:38]

On Linux the size of a WeakPtrFactory is 16 bytes vs 8 for a unique_ptr.
I am not sure it's worth adding more code that lazily instanciates for that, but
maybe you have other concerns? 

[yzshen1, 2016/11/15 20:26:15]

Just wanted to make sure that the size/init cost has been considered. I don't
have a very strong opinion.

+
   DISALLOW_COPY_AND_ASSIGN(InterfacePtrState);
 };
 
 }  // namespace internal
 }  // namespace mojo
 
 #endif  // MOJO_PUBLIC_CPP_BINDINGS_LIB_INTERFACE_PTR_STATE_H_