Move calculate layout method to vanilla JNI

Summary: Using vanilla JNI for calculate layout

Reviewed By: amir-shalem

Differential Revision: D17714219

fbshipit-source-id: bb05de4a0112eefc2b731997a4c1ecef5c0c7361

java/jni/YGJTypesVanilla.h

@@ -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.
+ */
+#include "jni.h"
+#include <yoga/YGValue.h>
+#include <yoga/Yoga.h>
+#include <map>
+#include "common.h"
+
+using namespace facebook::yoga::vanillajni;
+using namespace std;
+
+class PtrJNodeMap {
+  std::map<YGNodeRef, size_t> ptrsToIdxs_;
+  jobjectArray javaNodes_;
+
+public:
+  PtrJNodeMap() : ptrsToIdxs_{}, javaNodes_{} {}
+  PtrJNodeMap(
+      jlong* nativePointers,
+      size_t nativePointersSize,
+      jobjectArray javaNodes)
+      : javaNodes_{javaNodes} {
+    for (size_t i = 0; i < nativePointersSize; ++i) {
+      ptrsToIdxs_[(YGNodeRef) nativePointers[i]] = i;
+    }
+  }
+
+  ScopedLocalRef<jobject> ref(JNIEnv* env, YGNodeRef node) {
+    auto idx = ptrsToIdxs_.find(node);
+    if (idx == ptrsToIdxs_.end()) {
+      return ScopedLocalRef<jobject>(env);
+    } else {
+      return make_local_ref(
+          env, env->GetObjectArrayElement(javaNodes_, idx->second));
+    }
+  }
+};