Added following dart API changes to enable more efficient access based

runtime/vm/reusable_handles.h

+// 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.
+
+#ifndef VM_REUSABLE_HANDLES_H_
+#define VM_REUSABLE_HANDLES_H_
+
+#include "vm/allocation.h"
+#include "vm/handles.h"
+#include "vm/object.h"
+
+namespace dart {
+
+// The class ReusableHandleScope is used in regions of the
+// virtual machine where isolate specific reusable handles are used.
+// This class asserts that we do not add code that will result in recursive
+// uses of reusable handles.
+// It is used as follows:
+// {
+//   ReusableHandleScope reused_handles(isolate);
+//   ....
+//   .....
+//   code that uses isolate specific reusable handles.
+//   Array& funcs = reused_handles.ArrayHandle();
+//   ....
+// }
+#if defined(DEBUG)
+class ReusableObjectHandleScope : public StackResource {
+ public:
+  explicit ReusableObjectHandleScope(Isolate* isolate)
+      : StackResource(isolate), isolate_(isolate) {
+    ASSERT(!isolate->reusable_handle_scope_active());
+    isolate->set_reusable_handle_scope_active(true);
+  }
+  ReusableObjectHandleScope()
+      : StackResource(Isolate::Current()), isolate_(Isolate::Current()) {
+    ASSERT(!isolate()->reusable_handle_scope_active());
+    isolate()->set_reusable_handle_scope_active(true);
+  }
+  ~ReusableObjectHandleScope() {
+    ASSERT(isolate()->reusable_handle_scope_active());
+    isolate()->set_reusable_handle_scope_active(false);
+    Handle().raw_ = Object::null();
+  }
+  Object& Handle() {
+    ASSERT(isolate_->Object_handle_ != NULL);
+    return *isolate_->Object_handle_;
+  }
+
+ private:
+  Isolate* isolate_;
+  DISALLOW_COPY_AND_ASSIGN(ReusableObjectHandleScope);
+};
+
+
+class ReusableHandleScope : public StackResource {
+ public:
+  explicit ReusableHandleScope(Isolate* isolate)
+      : StackResource(isolate), isolate_(isolate) {
+    ASSERT(!isolate->reusable_handle_scope_active());
+    isolate->set_reusable_handle_scope_active(true);
+  }
+  ReusableHandleScope()
+      : StackResource(Isolate::Current()), isolate_(Isolate::Current()) {
+    ASSERT(!isolate()->reusable_handle_scope_active());
+    isolate()->set_reusable_handle_scope_active(true);
+  }
+  ~ReusableHandleScope() {
+    ASSERT(isolate()->reusable_handle_scope_active());
+    isolate()->set_reusable_handle_scope_active(false);
+#define CLEAR_REUSABLE_HANDLE(object)                                          \
+    object##Handle().raw_ = Object::null();                                    \
+
+    REUSABLE_HANDLE_LIST(CLEAR_REUSABLE_HANDLE);
+  }
+
+#define REUSABLE_HANDLE_ACCESSORS(object)                                      \
+  object& object##Handle() {                                                   \
+    ASSERT(isolate_->object##_handle_ != NULL);                                \
+    return *isolate_->object##_handle_;                                        \
+  }                                                                            \
+
+  REUSABLE_HANDLE_LIST(REUSABLE_HANDLE_ACCESSORS)
+#undef REUSABLE_HANDLE_ACCESSORS
+
+ private:
+  void ResetHandles();
+  Isolate* isolate_;
+  DISALLOW_COPY_AND_ASSIGN(ReusableHandleScope);
+};
+#else
+class ReusableObjectHandleScope : public ValueObject {
+ public:
+  explicit ReusableObjectHandleScope(Isolate* isolate)
+      : handle_(isolate->Object_handle_) {
+  }
+  ReusableObjectHandleScope() : handle_(Isolate::Current()->Object_handle_) {
+  }
+  ~ReusableObjectHandleScope() {
+    handle_->raw_ = Object::null();
+  }
+  Object& Handle() {
+    ASSERT(handle_ != NULL);
+    return *handle_;
+  }
+
+ private:
+  Object* handle_;
+  DISALLOW_COPY_AND_ASSIGN(ReusableObjectHandleScope);
+};
+
+
+class ReusableHandleScope : public ValueObject {
+ public:
+  explicit ReusableHandleScope(Isolate* isolate) : isolate_(isolate) {
+  }
+  ReusableHandleScope() : isolate_(Isolate::Current()) {
+  }
+  ~ReusableHandleScope() {
+#define CLEAR_REUSABLE_HANDLE(object)                                          \
+    object##Handle().raw_ = Object::null();                                    \
+
+    REUSABLE_HANDLE_LIST(CLEAR_REUSABLE_HANDLE);
+  }
+
+#define REUSABLE_HANDLE_ACCESSORS(object)                                      \
+  object& object##Handle() {                                                   \
+    ASSERT(isolate_->object##_handle_ != NULL);                                \
+    return *isolate_->object##_handle_;                                        \
+  }                                                                            \
+
+  REUSABLE_HANDLE_LIST(REUSABLE_HANDLE_ACCESSORS)
+#undef REUSABLE_HANDLE_ACCESSORS
+
+ private:
+  void ResetHandles();
+  Isolate* isolate_;
+  DISALLOW_COPY_AND_ASSIGN(ReusableHandleScope);
+};
+#endif  // defined(DEBUG)
+
+}  // namespace dart
+
+#endif  // VM_REUSABLE_HANDLES_H_