Mojo C++ Bindings: Support custom impl ref types

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

 // Copyright 2015 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_BINDING_STATE_H_
 #define MOJO_PUBLIC_CPP_BINDINGS_LIB_BINDING_STATE_H_
 
 #include <memory>
 #include <string>
 #include <utility>
@@ skipping 74 matching lines @@
                     std::unique_ptr<MessageReceiver> request_validator,
                     bool has_sync_methods,
                     MessageReceiverWithResponderStatus* stub,
                     uint32_t interface_version);
 
   void DestroyRouter();
 
   internal::Router* router_ = nullptr;
 };
 
-template <typename Interface, bool use_multiplex_router>
+template <typename Interface, bool use_multiplex_router, typename ImplRefTraits>
 class BindingState;
 
 // Uses a single-threaded, dedicated router. If |Interface| doesn't have any
 // methods to pass associated interface pointers or requests, there won't be
 // multiple interfaces running on the underlying message pipe. In that case, we
 // can use this specialization to reduce cost.
-template <typename Interface>
-class BindingState<Interface, false> : public SimpleBindingState {
+template <typename Interface, typename ImplRefTraits>
+class BindingState<Interface, false, ImplRefTraits>
+    : public SimpleBindingState {
  public:
-  explicit BindingState(Interface* impl) : impl_(impl) {
-    stub_.set_sink(impl_);
-  }
+  using ImplPointerType = typename ImplRefTraits::PointerType;
+
+  explicit BindingState(ImplPointerType impl) { stub_.set_sink(impl); }
 
   ~BindingState() { Close(); }
 
   void Bind(ScopedMessagePipeHandle handle,
             scoped_refptr<base::SingleThreadTaskRunner> runner) {
     DCHECK(!router_);
     SimpleBindingState::BindInternal(
         std::move(handle), runner, Interface::Name_,
         base::MakeUnique<typename Interface::RequestValidator_>(),
         Interface::HasSyncMethods_, &stub_, Interface::Version_);
   }
 
   InterfaceRequest<Interface> Unbind() {
     InterfaceRequest<Interface> request =
         MakeRequest<Interface>(router_->PassMessagePipe());
     DestroyRouter();
     return std::move(request);
   }
 
-  Interface* impl() { return impl_; }
+  Interface* impl() { return ImplRefTraits::GetRawPointer(stub_.sink()); }
 
  private:
-  typename Interface::Stub_ stub_;
-  Interface* impl_;
+  typename Interface::template Stub_<ImplRefTraits> stub_;
 
   DISALLOW_COPY_AND_ASSIGN(BindingState);
 };
 
 // Base class used for templated binding primitives which may bind a pipe to
 // multiple interfaces.
 class MOJO_CPP_BINDINGS_EXPORT MultiplexedBindingState {
  public:
   MultiplexedBindingState();
   ~MultiplexedBindingState();
@@ skipping 46 matching lines @@
                     bool has_sync_methods,
                     MessageReceiverWithResponderStatus* stub,
                     uint32_t interface_version);
 
   scoped_refptr<internal::MultiplexRouter> router_;
   std::unique_ptr<InterfaceEndpointClient> endpoint_client_;
 };
 
 // Uses a multiplexing router. If |Interface| has methods to pass associated
 // interface pointers or requests, this specialization should be used.
-template <typename Interface>
-class BindingState<Interface, true> : public MultiplexedBindingState {
+template <typename Interface, typename ImplRefTraits>
+class BindingState<Interface, true, ImplRefTraits>
+    : public MultiplexedBindingState {
  public:
-  explicit BindingState(Interface* impl) : impl_(impl) {
-    stub_.set_sink(impl_);
-  }
+  using ImplPointerType = typename ImplRefTraits::PointerType;
+
+  explicit BindingState(ImplPointerType impl) { stub_.set_sink(impl); }
 
   ~BindingState() { Close(); }
 
   void Bind(ScopedMessagePipeHandle handle,
             scoped_refptr<base::SingleThreadTaskRunner> runner) {
     MultiplexedBindingState::BindInternal(
         std::move(handle), runner, Interface::Name_,
         base::MakeUnique<typename Interface::RequestValidator_>(),
         Interface::PassesAssociatedKinds_, Interface::HasSyncMethods_, &stub_,
         Interface::Version_);
     stub_.serialization_context()->group_controller = router_;
   }
 
   InterfaceRequest<Interface> Unbind() {
     endpoint_client_.reset();
     InterfaceRequest<Interface> request =
         MakeRequest<Interface>(router_->PassMessagePipe());
     router_ = nullptr;
     return request;
   }
 
-  Interface* impl() { return impl_; }
+  Interface* impl() { return ImplRefTraits::GetRawPointer(stub_.sink()); }
 
  private:
-  typename Interface::Stub_ stub_;
-  Interface* impl_;
+  typename Interface::template Stub_<ImplRefTraits> stub_;
 
   DISALLOW_COPY_AND_ASSIGN(BindingState);
 };
 
 }  // namesapce internal
 }  // namespace mojo
 
 #endif  // MOJO_PUBLIC_CPP_BINDINGS_LIB_BINDING_STATE_H_