Make a global enum to differentiate impl & proxy.

ppapi/shared_impl/resource.h

 // Copyright (c) 2012 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 PPAPI_SHARED_IMPL_RESOURCE_H_
 #define PPAPI_SHARED_IMPL_RESOURCE_H_
 
 #include <stddef.h>  // For NULL.
 
 #include <string>
@@ skipping 51 matching lines @@
 
 namespace ppapi {
 
 // Forward declare all the resource APIs.
 namespace thunk {
 #define DECLARE_RESOURCE_CLASS(RESOURCE) class RESOURCE;
 FOR_ALL_PPAPI_RESOURCE_APIS(DECLARE_RESOURCE_CLASS)
 #undef DECLARE_RESOURCE_CLASS
 }  // namespace thunk
 
+// Resources have slightly different registration behaviors when the're an
+// in-process ("impl") resource in the host (renderer) process, or when they're
+// a proxied resource in the plugin process. This enum differentiates those
+// cases.
+enum ResourceObjectType {
+  OBJECT_IS_IMPL,
+  OBJECT_IS_PROXY
+};
+
 class PPAPI_SHARED_EXPORT Resource : public base::RefCounted<Resource> {
  public:
-  // For constructing non-proxied objects. This just takes the associated
-  // instance, and generates a new resource ID. The host resource will be the
-  // same as the newly-generated resource ID.
-  explicit Resource(PP_Instance instance);
+  // Constructor for impl and non-proxied, instance-only objects.
+  //
+  // For constructing "impl" (non-proxied) objects, this just takes the
+  // associated instance, and generates a new resource ID. The host resource
+  // will be the same as the newly-generated resource ID. For all objects in
+  // the renderer (host) process, you'll use this constructor and call it with
+  // OBJECT_IS_IMPL.
+  //
+  // For proxied objects, this will create an "instance-only" object which
+  // lives only in the plugin and doesn't have a corresponding object in the
+  // host. If you have a host resource ID, use the constructor below which
+  // takes that HostResource value.
+  explicit Resource(ResourceObjectType type, PP_Instance instance);
 
-  // For constructing proxied objects. This takes the resource generated in
-  // the host side, stores it, and allocates a "local" resource ID for use in
-  // the current process.
-  explicit Resource(const HostResource& host_resource);
+  // For constructing given a host resource.
+  //
+  // For OBJECT_IS_PROXY objects, this takes the resource generated in the host
+  // side, stores it, and allocates a "local" resource ID for use in the
+  // current process.
+  //
+  // For OBJECT_IS_IMPL, the host resource ID must be 0, since there should be
+  // no host resource generated (impl objects should generate their own). The
+  // reason for supporting this constructor at all for the IMPL case is that
+  // some shared objects use a host resource for both modes to keep things the
+  // same.
+  explicit Resource(ResourceObjectType type,
+                    const HostResource& host_resource);

[dmichael (off chromium), 2012/02/13 22:24:40]

Will this one ever be called with OBJECT_IS_IMPL? If not, is it worth passing
the parameter at all? If you want to keep it for the fact that it makes the
call-point self documenting, maybe it would make sense to DCHECK it?

[brettw, 2012/02/13 22:28:28]

Yes, in ppb_file_ref_shared.cc. That class needs to use a HostResource to
identify itself so that the PPB_FileRef_CreateInfo& struct can be shared.

 
   virtual ~Resource();
 
   PP_Instance pp_instance() const { return host_resource_.instance(); }
 
   // Returns the resource ID for this object in the current process without
   // adjusting the refcount. See also GetReference().
   PP_Resource pp_resource() const { return pp_resource_; }
 
   // Returns the host resource which identifies the resource in the host side
@@ skipping 53 matching lines @@
 #define DEFINE_RESOURCE_CAST(RESOURCE) \
   template<> inline thunk::RESOURCE* Resource::GetAs() { \
     return As##RESOURCE(); \
   }
 FOR_ALL_PPAPI_RESOURCE_APIS(DEFINE_RESOURCE_CAST)
 #undef DEFINE_RESOURCE_CAST
 
 }  // namespace ppapi
 
 #endif  // PPAPI_SHARED_IMPL_RESOURCE_H_