Add a new way of using ServiceProviderImpl without InterfaceFactory.

mojo/public/cpp/application/service_provider_impl.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_APPLICATION_SERVICE_PROVIDER_IMPL_H_
 #define MOJO_PUBLIC_APPLICATION_SERVICE_PROVIDER_IMPL_H_
 
+#include <functional>
 #include <string>
 
+#include "mojo/public/cpp/application/application_connection.h"
+#include "mojo/public/cpp/application/connection_context.h"
 #include "mojo/public/cpp/application/lib/interface_factory_connector.h"
 #include "mojo/public/cpp/application/lib/service_connector_registry.h"
+#include "mojo/public/cpp/application/service_connector.h"
 #include "mojo/public/cpp/bindings/binding.h"
 #include "mojo/public/interfaces/application/service_provider.mojom.h"
 
 namespace mojo {
 
-// Implements a registry that can be used to expose services to another app.
+// An implementation of |ServiceProvider|, which can be customized appropriately
+// (to select what services it provides).
 class ServiceProviderImpl : public ServiceProvider {
  public:
+  // A |RequestHandler<Interface>| is simply a function that handles a request
+  // for |Interface|. If it determines (e.g., based on the given
+  // |ConnectionContext|) that the request should be "accepted", then it should
+  // "connect" ("take ownership of") request. Otherwise, it can simply drop
+  // |request| (as implied  by the interface).
+  template <typename Interface>
+  using RequestHandler =

[vardhan, 2016/05/11 23:09:35]

nit: more specific typename? (sorry!)

+      std::function<void(const ConnectionContext& connection_context,
+                         InterfaceRequest<Interface> request)>;
+
+  // Constructs this service provider implementation in an unbound state.
   ServiceProviderImpl();
+
+  // Constructs this service provider implementation, binding it to the given
+  // interface request.
+  // TODO(vtl): This should take a |ConnectionContext|, to provide
+  // |RequestHandler<I>|s.
   explicit ServiceProviderImpl(InterfaceRequest<ServiceProvider> request);
+
   ~ServiceProviderImpl() override;
 
+  // Binds this service provider implementation to the given interface request.
+  // This may only be called if this object is unbound.
+  // TODO(vtl): This should take a |ConnectionContext|, to provide
+  // |RequestHandler<I>|s.
   void Bind(InterfaceRequest<ServiceProvider> request);
-  // Disconnect this service provider and put it in a state where it can be
-  // rebound to a new request.
+
+  // Disconnect this service provider implementation and put it in a state where
+  // it can be rebound to a new request (i.e., restores this object to an
+  // unbound state). This may be called even if this object is already unbound.
   void Close();
 
+  // TODO(vtl): Remove this.
   template <typename Interface>
   void AddService(InterfaceFactory<Interface>* factory,
                   const std::string& interface_name = Interface::Name_) {
     service_connector_registry_.SetServiceConnectorForName(
         std::unique_ptr<ServiceConnector>(
             new internal::InterfaceFactoryConnector<Interface>(factory)),
         interface_name);
   }
 
-  // ServiceProviderImpl uses the fallback_service_provider_ whenever someone
-  // asks a service that doesn't exist in the service_connector_registry_.
-  //
-  // Note: ServiceProviderImpl does not take ownership of |fallback|. The caller
-  //       must ensure that |fallback| outlives the ServiceProviderImpl.
-  //
-  void set_fallback_service_provider(ServiceProvider* fallback) {
-    fallback_service_provider_ = fallback;
+  // Adds a supported service with the given |name|, using the given
+  // |request_handler| (see above for information about
+  // |RequestHandler<Interface>|). |request_handler| should remain valid for the
+  // lifetime of this object.
+  // TODO(vtl): Remove the AddService() above and rename this to AddService().
+  template <typename Interface>
+  void AddServiceNew(RequestHandler<Interface> request_handler,
+                     const std::string& name = Interface::Name_) {
+    service_connector_registry_.SetServiceConnectorForName(
+        std::unique_ptr<ServiceConnector>(
+            new ServiceConnectorImpl<Interface>(std::move(request_handler))),
+        name);
+  }
+
+  // This uses the provided |fallback_service_provider| for connection requests
+  // for services that are not known (haven't been added). (Set it to null to
+  // not have any fallback.) A fallback must outlive this object (or until it is
+  // "cleared" or replaced by a different fallback.
+  void set_fallback_service_provider(
+      ServiceProvider* fallback_service_provider) {
+    fallback_service_provider_ = fallback_service_provider;
   }
 
  private:
-  // Overridden from ServiceProvider:
+  // Objects of this class are used to adapt a generic (untyped) connection
+  // request (i.e., |ServiceConnector::ConnectToService()|) to the type-safe
+  // |RequestHandler<Interface>|.
+  template <typename Interface>
+  class ServiceConnectorImpl : public ServiceConnector {
+   public:
+    explicit ServiceConnectorImpl(RequestHandler<Interface> request_handler)
+        : request_handler_(std::move(request_handler)) {}
+    ~ServiceConnectorImpl() override {}
+
+    void ConnectToService(ApplicationConnection* application_connection,
+                          const std::string& interface_name,
+                          ScopedMessagePipeHandle client_handle) override {
+      // TODO(vtl): This should be given a |const ConnectionContext&|, instead
+      // of an |ApplicationConnection*| -- which may be null!
+      request_handler_(application_connection
+                           ? application_connection->GetConnectionContext()
+                           : ConnectionContext(),
+                       InterfaceRequest<Interface>(client_handle.Pass()));
+    }
+
+   private:
+    const RequestHandler<Interface> request_handler_;
+
+    MOJO_DISALLOW_COPY_AND_ASSIGN(ServiceConnectorImpl);
+  };
+
+  // Overridden from |ServiceProvider|:
   void ConnectToService(const String& service_name,
                         ScopedMessagePipeHandle client_handle) override;
 
   Binding<ServiceProvider> binding_;
 
   internal::ServiceConnectorRegistry service_connector_registry_;
   ServiceProvider* fallback_service_provider_;
 
   MOJO_DISALLOW_COPY_AND_ASSIGN(ServiceProviderImpl);
 };
 
 }  // namespace mojo
 
 #endif  // MOJO_PUBLIC_APPLICATION_SERVICE_PROVIDER_IMPL_H_