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.h

@@ -0,0 +1,51 @@
+/*
+ * 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.
+ */
+#pragma once
+
+#include <jni.h>
+#include <cstddef>
+
+namespace facebook {
+namespace yoga {
+namespace vanillajni {
+
+/**
+ * This method has to be called before using the vanillajni library. This method
+ * is typically called when doing initialization in the "on load" JNI hook of a
+ * particular library.
+ *
+ * This method is thread safe, and after the first time it's called it has no
+ * initialization effect.
+ *
+ * @param  env use this output parameter to get a JNIEnv to use for things such
+ * as registering native methods and such.
+ * @param  vm  the VM instance passed by JNI. This is usually the VM instance
+ * that is passed to the "on load" JNI hook.
+ * @return an integer value to return from the "on load" hook.
+ */
+jint ensureInitialized(JNIEnv** env, JavaVM* vm);
+
+/**
+ * Returns a JNIEnv* suitable for the current thread. If the current thread is
+ * not attached to the Java VM, this method aborts execution.
+ */
+JNIEnv* getCurrentEnv();
+
+/**
+ * Logs an error message and aborts the current process.
+ */
+void logErrorMessageAndDie(const char* message);
+
+/**
+ * Checks whether there is a pending JNI exception. If so, it logs an error
+ * message and aborts the current process. Otherwise it does nothing.
+ */
+void assertNoPendingJniException(JNIEnv* env);
+
+} // namespace vanillajni
+} // namespace yoga
+} // namespace facebook