Implement weak persistent handles in the Dart API.

runtime/vm/dart_api_impl_test.cc

 // 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.
 
 #include "include/dart_api.h"
 
 #include "vm/assert.h"
 #include "vm/dart_api_impl.h"
 #include "vm/dart_api_state.h"
 #include "vm/thread.h"
@@ skipping 746 matching lines @@
 
   // Make sure that the value transferred.
   EXPECT(Dart_IsBoolean(obj2));
   bool value = false;
   Dart_Handle result = Dart_BooleanValue(obj2, &value);
   EXPECT_VALID(result);
   EXPECT(value);
 }
 
 
+TEST_CASE(WeakPersistentHandle) {
+  Dart_Handle weak_new_ref = Dart_Null();
+  EXPECT(Dart_IsNull(weak_new_ref));
+
+  Dart_Handle weak_old_ref = Dart_Null();
+  EXPECT(Dart_IsNull(weak_old_ref));
+
+  {
+    Dart_EnterScope();
+
+    // create an object in new space
+    Dart_Handle new_ref = Dart_NewString("new string");
+    EXPECT_VALID(new_ref);
+
+    // create an object in old space
+    Dart_Handle old_ref;
+    {
+      DARTSCOPE(Isolate::Current());
+      const String& str =
+          String::Handle(String::New("old string", Heap::kOld));
+      old_ref = Api::NewLocalHandle(str);
+      EXPECT_VALID(old_ref);
+    }
+
+    // create a weak ref to the new space object
+    weak_new_ref = Dart_NewWeakPersistentHandle(new_ref);
+    EXPECT_VALID(weak_new_ref);
+    EXPECT(!Dart_IsNull(weak_new_ref));
+
+    // create a weak ref to the old space object
+    weak_old_ref = Dart_NewWeakPersistentHandle(old_ref);
+    EXPECT_VALID(weak_old_ref);
+    EXPECT(!Dart_IsNull(weak_old_ref));
+
+    // garbage collect new space
+    Isolate::Current()->heap()->CollectGarbage(Heap::kNew);
+
+    // nothing should be invalidated or cleared

[Ivan Posva, 2011/12/19 22:41:36]

Also the weak and non-weak handles should still be pointing to the same object?

[cshapiro, 2011/12/20 00:58:57]

Sounds good.  Done.

+    EXPECT_VALID(new_ref);
+    EXPECT(!Dart_IsNull(new_ref));
+    EXPECT_VALID(old_ref);
+    EXPECT(!Dart_IsNull(old_ref));
+    EXPECT_VALID(weak_new_ref);
+    EXPECT(!Dart_IsNull(weak_new_ref));
+    EXPECT_VALID(weak_old_ref);
+    EXPECT(!Dart_IsNull(weak_old_ref));
+
+    // garbage collect old space
+    Isolate::Current()->heap()->CollectGarbage(Heap::kOld);
+
+    // nothing should be invalidated or cleared

[Ivan Posva, 2011/12/19 22:41:36]

ditto.

[cshapiro, 2011/12/20 00:58:57]

Done.

+    EXPECT_VALID(new_ref);
+    EXPECT(!Dart_IsNull(new_ref));
+    EXPECT_VALID(old_ref);
+    EXPECT(!Dart_IsNull(old_ref));
+    EXPECT_VALID(weak_new_ref);
+    EXPECT(!Dart_IsNull(weak_new_ref));
+    EXPECT_VALID(weak_old_ref);
+    EXPECT(!Dart_IsNull(weak_old_ref));
+
+    // delete local (strong) references
+    Dart_ExitScope();
+  }
+
+  // garbage collect new space again
+  Isolate::Current()->heap()->CollectGarbage(Heap::kNew);
+
+  // weak ref to new space object should now be cleared
+  EXPECT_VALID(weak_new_ref);
+  EXPECT(Dart_IsNull(weak_new_ref));
+  EXPECT_VALID(weak_old_ref);
+  EXPECT(!Dart_IsNull(weak_old_ref));
+
+  // garbage collect old space again
+  Isolate::Current()->heap()->CollectGarbage(Heap::kOld);
+
+  // weak ref to old space object should now be cleared
+  EXPECT_VALID(weak_new_ref);
+  EXPECT(Dart_IsNull(weak_new_ref));
+  EXPECT_VALID(weak_old_ref);
+  EXPECT(Dart_IsNull(weak_old_ref));
+}
+
+
 // Unit test for creating multiple scopes and local handles within them.
 // Ensure that the local handles get all cleaned out when exiting the
 // scope.
 UNIT_TEST_CASE(LocalHandles) {
   TestCase::CreateTestIsolate();
   Isolate* isolate = Isolate::Current();
   EXPECT(isolate != NULL);
   ApiState* state = isolate->api_state();
   EXPECT(state != NULL);
   ApiLocalScope* scope = state->top_scope();
@@ skipping 2189 matching lines @@
   EXPECT_EQ(3, interrupt_count);
 
   // Give the spawned thread enough time to properly exit.
   OS::Sleep(20);
   Isolate::SetInterruptCallback(saved);
 }
 
 #endif  // TARGET_ARCH_IA32.
 
 }  // namespace dart