Add PhantomRef based YogaNode subclass

Summary: Adds a subclass of `YogaNodeJNIBase` that uses `PhantomReference` for deallocating native memory rather than `Object#finalize()`. This should help making garbage collection more efficient.

Reviewed By: amir-shalem

Differential Revision: D16182667

fbshipit-source-id: d310fdb6af184168c43462b24f5e18ab5d0d7ad0

ReactAndroid/src/main/java/com/facebook/yoga/YogaNode.java

@@ -10,11 +10,11 @@
 
 public abstract class YogaNode {
   public static YogaNode create() {
-    return new YogaNodeJNIBase();
+    return new YogaNodeJNIFinalizer();
   }
 
   public static YogaNode create(YogaConfig config) {
-    return new YogaNodeJNIBase(config);
+    return new YogaNodeJNIFinalizer(config);
   }
 
   public abstract void reset();

ReactAndroid/src/main/java/com/facebook/yoga/YogaNodeJNIBase.java

@@ -12,7 +12,7 @@
 import javax.annotation.Nullable;
 
 @DoNotStrip
-public class YogaNodeJNIBase extends YogaNode implements Cloneable {
+public abstract class YogaNodeJNIBase extends YogaNode implements Cloneable {
 
   /* Those flags needs be in sync with YGJNI.cpp */
   private static final byte MARGIN = 1;
@@ -35,7 +35,7 @@ public class YogaNodeJNIBase extends YogaNode implements Cloneable {
   @Nullable private List<YogaNodeJNIBase> mChildren;
   @Nullable private YogaMeasureFunction mMeasureFunction;
   @Nullable private YogaBaselineFunction mBaselineFunction;
-  private long mNativePointer;
+  protected long mNativePointer;
   @Nullable private Object mData;
 
   @DoNotStrip
@@ -46,37 +46,21 @@ public class YogaNodeJNIBase extends YogaNode implements Cloneable {
 
   private boolean mHasNewLayout = true;
 
-  public YogaNodeJNIBase() {
-    mNativePointer = YogaNative.jni_YGNodeNew();
-    if (mNativePointer == 0) {
+  private YogaNodeJNIBase(long nativePointer) {
+    if (nativePointer == 0) {
       throw new IllegalStateException("Failed to allocate native memory");
     }
+    mNativePointer = nativePointer;
   }
 
-  public YogaNodeJNIBase(YogaConfig config) {
-    mNativePointer = YogaNative.jni_YGNodeNewWithConfig(config.mNativePointer);
-    if (mNativePointer == 0) {
-      throw new IllegalStateException("Failed to allocate native memory");
-    }
+  YogaNodeJNIBase() {
+    this(YogaNative.jni_YGNodeNew());
   }
 
-  @Override
-  protected void finalize() throws Throwable {
-    try {
-      freeNatives();
-    } finally {
-      super.finalize();
-    }
+  YogaNodeJNIBase(YogaConfig config) {
+    this(YogaNative.jni_YGNodeNewWithConfig(config.mNativePointer));
   }
 
-  /* frees the native underlying YGNode. Useful for testing. */
-  public void freeNatives() {
-    if (mNativePointer > 0) {
-      long nativePointer = mNativePointer;
-      mNativePointer = 0;
-      YogaNative.jni_YGNodeFree(nativePointer);
-    }
-  }
   public void reset() {
     mMeasureFunction = null;
     mBaselineFunction = null;

ReactAndroid/src/main/java/com/facebook/yoga/YogaNodeJNIFinalizer.java

@@ -0,0 +1,34 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the LICENSE
+ * file in the root directory of this source tree.
+ */
+package com.facebook.yoga;
+
+public class YogaNodeJNIFinalizer extends YogaNodeJNIBase {
+  public YogaNodeJNIFinalizer() {
+    super();
+  }
+
+  public YogaNodeJNIFinalizer(YogaConfig config) {
+    super(config);
+  }
+
+  @Override
+  protected void finalize() throws Throwable {
+    try {
+      freeNatives();
+    } finally {
+      super.finalize();
+    }
+   }
+
+  public void freeNatives() {
+    if (mNativePointer != 0) {
+      long nativePointer = mNativePointer;
+      mNativePointer = 0;
+      YogaNative.jni_YGNodeFree(nativePointer);
+    }
+  }
+}

ReactAndroid/src/main/java/com/facebook/yoga/YogaNodeJNIPhantomRefs.java

@@ -0,0 +1,41 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the LICENSE
+ * file in the root directory of this source tree.
+ */
+package com.facebook.yoga;
+
+import com.facebook.jni.DestructorThread;
+
+public class YogaNodeJNIPhantomRefs extends YogaNodeJNIBase {
+  public YogaNodeJNIPhantomRefs() {
+    super();
+    registerPhantomRef(this, mNativePointer);
+  }
+
+  public YogaNodeJNIPhantomRefs(YogaConfig config) {
+    super(config);
+    registerPhantomRef(this, mNativePointer);
+  }
+
+  @Override
+  public YogaNodeJNIPhantomRefs cloneWithoutChildren() {
+    YogaNodeJNIPhantomRefs clone = (YogaNodeJNIPhantomRefs) super.cloneWithoutChildren();
+    registerPhantomRef(clone, clone.mNativePointer);
+    return clone;
+  }
+
+  private static final void registerPhantomRef(YogaNode node, final long nativePointer) {
+    new DestructorThread.Destructor(node) {
+      private long mNativePointer = nativePointer;
+      @Override
+      protected void destruct() {
+        if (mNativePointer != 0) {
+          YogaNative.jni_YGNodeFree(mNativePointer);
+          mNativePointer = 0;
+        }
+      }
+    };
+  }
+}