Add Dart_GetNativeReceiver to special case access to the native field

runtime/vm/dart_api_impl.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "include/dart_api.h"
 #include "include/dart_mirrors_api.h"
 #include "include/dart_native_api.h"
 
 #include "platform/assert.h"
 #include "vm/bigint_operations.h"
@@ skipping 3605 matching lines @@
         "%s: invalid index %d passed in to access native instance field",
         CURRENT_FUNC, fld_index);
   }
   if (value == NULL) {
     RETURN_NULL_ERROR(value);
   }
   *value = instance.GetNativeField(isolate, fld_index);
   return Api::Success();
 }
 
+DART_EXPORT Dart_Handle Dart_GetNativeReceiver(Dart_NativeArguments args,
+                                               intptr_t* value) {
+  NativeArguments* arguments = reinterpret_cast<NativeArguments*>(args);
+  Isolate* isolate = arguments->isolate();
+  DARTSCOPE(isolate);
+  const Object& obj = Object::Handle(isolate, arguments->NativeArgAt(0));
+  intptr_t cid = obj.GetClassId();
+  if (cid <= kNumPredefinedCids) {
+    if (cid == kNullCid) {
+      return Api::NewError("%s expects receiver argument to be non-null.",
+                           CURRENT_FUNC);
+    }
+    return Api::NewError("%s expects receiver argument to be of"
+                         " type Instance.", CURRENT_FUNC);
+  }
+  const Instance& instance = Instance::Cast(obj);
+  ASSERT(instance.IsValidNativeIndex(0));
+  if (value == NULL) {
+    RETURN_NULL_ERROR(value);
+  }
+  *value = instance.GetNativeField(isolate, 0);
+  return Api::Success();
+}
+
 
 DART_EXPORT void Dart_SetReturnValue(Dart_NativeArguments args,
                                      Dart_Handle retval) {
   NativeArguments* arguments = reinterpret_cast<NativeArguments*>(args);
   Isolate* isolate = arguments->isolate();
   CHECK_ISOLATE(isolate);
   if ((retval != Api::Null()) && (!Api::IsInstance(retval))) {
     const Object& ret_obj = Object::Handle(Api::UnwrapHandle(retval));
     FATAL1("Return value check failed: saw '%s' expected a dart Instance.",
            ret_obj.ToCString());
@@ skipping 506 matching lines @@
   }
   {
     NoGCScope no_gc;
     RawObject* raw_obj = obj.raw();
     isolate->heap()->SetPeer(raw_obj, peer);
   }
   return Api::Success();
 }
 
 }  // namespace dart