- Add following additional methods to the API to make returning values

runtime/vm/dart_api_impl.h

 // Copyright (c) 2011, 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.
 
 #ifndef VM_DART_API_IMPL_H_
 #define VM_DART_API_IMPL_H_
 
 #include "vm/allocation.h"
+#include "vm/native_arguments.h"
 #include "vm/object.h"
 
 namespace dart {
 
 class ApiLocalScope;
 class ApiState;
 class FinalizablePersistentHandle;
 class LocalHandle;
 class PersistentHandle;
 
@@ skipping 121 matching lines @@
   // Gets the handle which holds the pre-created acquired error object.
   static Dart_Handle AcquiredError(Isolate* isolate);
 
   // Returns true if the handle holds a Smi.
   static bool IsSmi(Dart_Handle handle) {
     // TODO(turnidge): Assumes RawObject* is at offset zero.  Fix.
     RawObject* raw = *(reinterpret_cast<RawObject**>(handle));
     return !raw->IsHeapObject();
   }
 
+  // Returns true if the handle holds a Dart Instance.
+  static bool IsInstance(Dart_Handle handle) {
+    return (ClassId(handle) >= kInstanceCid);
+  }
+
   // Returns the value of a Smi.
   static intptr_t SmiValue(Dart_Handle handle) {
     // TODO(turnidge): Assumes RawObject* is at offset zero.  Fix.
     uword value = *(reinterpret_cast<uword*>(handle));
     return Smi::ValueFromRaw(value);
   }
 
   static intptr_t ClassId(Dart_Handle handle) {
     // TODO(turnidge): Assumes RawObject* is at offset zero.  Fix.
     RawObject* raw = *(reinterpret_cast<RawObject**>(handle));
@@ skipping 20 matching lines @@
 
   // Performs one-time initialization needed by the API.
   static void InitOnce();
 
   // Allocates handles for objects in the VM isolate.
   static void InitHandles();
 
   // Helper function to get the peer value of an external string object.
   static bool ExternalStringGetPeerHelper(Dart_Handle object, void** peer);
 
+  // Helper function to set the return value of native functions.
+  static void SetReturnValue(NativeArguments* args, Dart_Handle retval) {
+    NoGCScope no_gc_scope;
+    args->SetReturnUnsafe(UnwrapHandle(retval));
+  }
+  static void SetSmiReturnValue(NativeArguments* args, intptr_t retval) {
+    NoGCScope no_gc_scope;
+    args->SetReturnUnsafe(Smi::New(retval));
+  }
+  static void SetIntegerReturnValue(NativeArguments* args, intptr_t retval) {
+    NoGCScope no_gc_scope;
+    args->SetReturnUnsafe(Integer::New(retval));
+  }
+  static void SetDoubleReturnValue(NativeArguments* args, double retval) {
+    NoGCScope no_gc_scope;
+    args->SetReturnUnsafe(Double::New(retval));
+  }
+
  private:
   // Thread local key used by the API. Currently holds the current
   // ApiNativeScope if any.
   static ThreadLocalKey api_native_key_;
   static Dart_Handle true_handle_;
   static Dart_Handle false_handle_;
   static Dart_Handle null_handle_;
 
   friend class ApiNativeScope;
 };
@@ skipping 18 matching lines @@
 
 // End a no Dart API call backs Scope.
 #define END_NO_CALLBACK_SCOPE(isolate)                                         \
   isolate->DecrementNoCallbackScopeDepth()
 
 #define CHECK_CALLBACK_STATE(isolate)                                          \
   if (isolate->no_callback_scope_depth() != 0) {                               \
     return reinterpret_cast<Dart_Handle>(Api::AcquiredError(isolate));         \
   }                                                                            \
 
+#define ASSERT_CALLBACK_STATE(isolate)                                         \
+  ASSERT(isolate->no_callback_scope_depth() == 0)
+
 }  // namespace dart.
 
 #endif  // VM_DART_API_IMPL_H_