Adds a method to check if an object has been set weak

Uses V8 to determine if setWeak has been called on this Object. This
change-set also changes the way `setWeak` works. `setWeak` now returns
this, so object chaining can be used.

Finally, V8#referenceCounts have been updated to include a count
of Weak objects. That is, if an object is marked weak, it should
not count towards the Object count.

Change-Id: I28d9023add2ff7e180bd30356665b9055df9cd38

Author: irbull

jni/com_eclipsesource_v8_V8Impl.cpp

@@ -1698,6 +1698,12 @@ JNIEXPORT void JNICALL Java_com_eclipsesource_v8_V8__1setWeak
     }, WeakCallbackType::kFinalizer);
 }
 
+JNIEXPORT jboolean JNICALL Java_com_eclipsesource_v8_V8__1isWeak
+  (JNIEnv * env, jobject, jlong v8RuntimePtr, jlong objectHandle) {
+    Isolate* isolate = SETUP(env, v8RuntimePtr, 0);
+    return reinterpret_cast<Persistent<Object>*>(objectHandle)->IsWeak();
+}
+
 JNIEXPORT jlong JNICALL Java_com_eclipsesource_v8_V8__1registerJavaMethod
 (JNIEnv *env, jobject, jlong v8RuntimePtr, jlong objectHandle, jstring functionName, jboolean voidMethod) {
   Isolate* isolate = SETUP(env, v8RuntimePtr, 0);

jni/com_eclipsesource_v8_V8Impl.h

@@ -296,7 +296,7 @@ public static int getActiveRuntimes() {
      * @return The number of Object References on this runtime.
      */
     public long getObjectReferenceCount() {
-        return objectReferences;
+        return objectReferences - v8WeakReferences.size();
     }
 
     protected long getV8RuntimePtr() {
@@ -370,7 +370,7 @@ public void release(final boolean reportMemoryLeaks) {
             _releaseRuntime(v8RuntimePtr);
             v8RuntimePtr = 0L;
             released = true;
-            if (reportMemoryLeaks && ((objectReferences - v8WeakReferences.size()) > 0)) {
+            if (reportMemoryLeaks && (getObjectReferenceCount() > 0)) {
                 throw new IllegalStateException(objectReferences + " Object(s) still exist in runtime");
             }
         }
@@ -1055,6 +1055,10 @@ protected void setWeak(final long v8RuntimePtr, final long objectHandle) {
         _setWeak(v8RuntimePtr, objectHandle);
     }
 
+    protected boolean isWeak(final long v8RuntimePtr, final long objectHandle) {
+        return _isWeak(v8RuntimePtr, objectHandle);
+    }
+
     protected void release(final long v8RuntimePtr, final long objectHandle) {
         _release(v8RuntimePtr, objectHandle);
     }
@@ -1523,6 +1527,8 @@ protected void releaseMethodDescriptor(final long v8RuntimePtr, final long metho
 
     private native void _setWeak(long runtimePtr, long objectHandle);
 
+    private native boolean _isWeak(long runtimePtr, long objectHandle);
+
     private native ByteBuffer _createV8ArrayBufferBackingStore(final long v8RuntimePtr, final long objectHandle, final int capacity);
 
     private native static String _getVersion();

src/main/java/com/eclipsesource/v8/V8.java

@@ -212,11 +212,24 @@ public V8Value twin() {
      * the object will be released, so this should only be used if there is no
      * other way to track object usage.
      */
-    public void setWeak() {
+    public V8Value setWeak() {
         v8.checkThread();
         v8.checkReleased();
         v8.v8WeakReferences.put(getHandle(), this);
         v8.setWeak(v8.getV8RuntimePtr(), getHandle());
+        return this;
+    }
+
+    /**
+     * If {@link V8Value#setWeak()} has been called on this Object, this method
+     * will return true. Otherwise it will return false.
+     *
+     * @return Returns true if this object has been set 'Weak', return false otherwise.
+     */
+    public boolean isWeak() {
+        v8.checkThread();
+        v8.checkReleased();
+        return v8.isWeak(v8.getV8RuntimePtr(), getHandle());
     }
 
     /**

src/main/java/com/eclipsesource/v8/V8Value.java

@@ -1733,4 +1733,18 @@ public void testGetType_Undefined() {
         assertEquals(V8Value.UNDEFINED, V8.getUndefined().getV8Type());
     }
 
+    @Test
+    public void testWeakReferenceReducesObjectCount() {
+        new V8Object(v8).setWeak();
+
+        assertEquals(0, v8.getObjectReferenceCount());
+    }
+
+    @Test
+    public void setWeakMakesObjectWeak() {
+        V8Value object = new V8Object(v8).setWeak();
+
+        assertTrue(object.isWeak());
+    }
+
 }