Mojo: Implement support for |Foo&| mojom syntax

mojo/public/cpp/bindings/interface_request.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_INTERFACE_REQUEST_H_
+#define MOJO_PUBLIC_CPP_BINDINGS_INTERFACE_REQUEST_H_
+
+#include "mojo/public/cpp/bindings/interface_ptr.h"
+
+namespace mojo {
+
+// Used in methods that return instances of remote objects.
+template <typename Interface>
+class InterfaceRequest {
+  MOJO_MOVE_ONLY_TYPE_FOR_CPP_03(InterfaceRequest, RValue)
+ public:
+  InterfaceRequest() {}
+
+  InterfaceRequest(RValue other) {
+    handle_ = other.object->handle_.Pass();
+  }
+  InterfaceRequest& operator=(RValue other) {
+    handle_ = other.object->handle_.Pass();
+    return *this;
+  }
+
+  // Returns true if the request has yet to be completed.
+  bool is_pending() const { return handle_.is_valid(); }
+
+  void Bind(ScopedMessagePipeHandle handle) {
+    handle_ = handle.Pass();
+  }
+
+  ScopedMessagePipeHandle PassMessagePipe() {
+    return handle_.Pass();
+  }
+
+ private:
+  ScopedMessagePipeHandle handle_;
+};
+
+template <typename Interface>
+InterfaceRequest<Interface> MakeRequest(ScopedMessagePipeHandle handle) {
+  InterfaceRequest<Interface> request;
+  request.Bind(handle.Pass());
+  return request.Pass();
+}
+
+// Used to construct a request that synchronously binds an InterfacePtr<..>,
+// making it immediately usable upon return. The resulting request object may
+// then be later bound to an InterfaceImpl<..> via BindToRequest.
+//
+// Given the following interface:
+//
+//   interface Foo {
+//     CreateBar(Bar& bar);
+//   }
+//
+// The caller of CreateBar would have code similar to the following:
+//
+//   InterfacePtr<Foo> foo = ...;
+//   InterfacePtr<Bar> bar;
+//   foo->CreateBar(Get(&bar));
+//
+// Upon return from CreateBar, |bar| is ready to have methods called on it.
+//
+template <typename Interface>
+InterfaceRequest<Interface> Get(InterfacePtr<Interface>* ptr) {
+  MessagePipe pipe;
+  ptr->Bind(pipe.handle0.Pass());
+  return MakeRequest<Interface>(pipe.handle1.Pass());
+}
+
+}  // namespace mojo
+
+#endif  // MOJO_PUBLIC_CPP_BINDINGS_INTERFACE_REQUEST_H_