Copy fbjni library from react-native

lib/fb/include/jni/WeakReference.h

@@ -0,0 +1,55 @@
+/*
+ * Copyright (c) 2015-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#pragma once
+#include <string>
+#include <jni.h>
+#include <fb/noncopyable.h>
+#include <fb/Countable.h>
+#include <fb/visibility.h>
+
+
+namespace facebook {
+namespace jni {
+
+class FBEXPORT WeakReference : public Countable {
+public:
+  typedef RefPtr<WeakReference> Ptr;
+  WeakReference(jobject strongRef);
+  ~WeakReference();
+  jweak weakRef() {
+    return m_weakReference;
+  }
+
+private:
+  jweak m_weakReference;
+};
+
+// This class is intended to take a weak reference and turn it into a strong
+// local reference. Consequently, it should only be allocated on the stack.
+class FBEXPORT ResolvedWeakReference : public noncopyable {
+public:
+  ResolvedWeakReference(jobject weakRef);
+  ResolvedWeakReference(const RefPtr<WeakReference>& weakRef);
+  ~ResolvedWeakReference();
+
+  operator jobject () {
+    return m_strongReference;
+  }
+
+  explicit operator bool () {
+    return m_strongReference != nullptr;
+  }
+
+private:
+  jobject m_strongReference;
+};
+
+} }
+