Add Scoped Local and Global Ref

Summary: Add ScopedLocalRef, ScopedGlobalRef and some common methods to be used later.

Reviewed By: amir-shalem

Differential Revision: D17711284

fbshipit-source-id: be43d5e246bc2406765057783be11854877c41f1

java/jni/corefunctions.cpp

@@ -0,0 +1,74 @@
+/*
+ * 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 "corefunctions.h"
+#include "macros.h"
+
+namespace facebook {
+namespace yoga {
+namespace vanillajni {
+
+namespace {
+JavaVM* globalVm = NULL;
+struct JavaVMInitializer {
+  JavaVMInitializer(JavaVM* vm) {
+    if (!vm) {
+      logErrorMessageAndDie(
+          "You cannot pass a NULL JavaVM to ensureInitialized");
+    }
+    globalVm = vm;
+  }
+};
+} // namespace
+
+jint ensureInitialized(JNIEnv** env, JavaVM* vm) {
+  static JavaVMInitializer init(vm);
+
+  if (!env) {
+    logErrorMessageAndDie(
+        "Need to pass a valid JNIEnv pointer to vanillajni initialization "
+        "routine");
+  }
+
+  if (vm->GetEnv(reinterpret_cast<void**>(env), JNI_VERSION_1_6) != JNI_OK) {
+    logErrorMessageAndDie(
+        "Error retrieving JNIEnv during initialization of vanillajni");
+  }
+
+  return JNI_VERSION_1_6;
+}
+
+JNIEnv* getCurrentEnv() {
+  JNIEnv* env;
+  jint ret = globalVm->GetEnv((void**) &env, JNI_VERSION_1_6);
+  if (ret != JNI_OK) {
+    logErrorMessageAndDie(
+        "There was an error retrieving the current JNIEnv. Make sure the "
+        "current thread is attached");
+  }
+  return env;
+}
+
+void logErrorMessageAndDie(const char* message) {
+  VANILLAJNI_LOG_ERROR(
+      "VanillaJni",
+      "Aborting due to error detected in native code: %s",
+      message);
+  VANILLAJNI_DIE();
+}
+
+void assertNoPendingJniException(JNIEnv* env) {
+  // This method cannot call any other method of the library, since other
+  // methods of the library use it to check for exceptions too
+  if (env->ExceptionCheck()) {
+    env->ExceptionDescribe();
+    logErrorMessageAndDie("Aborting due to pending Java exception in JNI");
+  }
+}
+
+} // namespace vanillajni
+} // namespace yoga
+} // namespace facebook