text: /*
   * Copyright (C) 2010 The Android Open Source Project
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  #ifndef SCOPED_LOCAL_REF_H_
  #define SCOPED_LOCAL_REF_H_
  
  #include <cstddef>
  
  #include "jni.h"
  #include "nativehelper_utils.h"
  
  // A smart pointer that deletes a JNI local reference when it goes out of scope.
  template <typename T>
  class ScopedLocalRef {
  public:
      ScopedLocalRef(JNIEnv* env, T localRef) : mEnv(env), mLocalRef(localRef) {}
  
      ~ScopedLocalRef() { reset(); }
  
      void reset(T ptr = NULL) {
          if (ptr != mLocalRef) {
              if (mLocalRef != NULL) {
                  mEnv->DeleteLocalRef(mLocalRef);
              }
              mLocalRef = ptr;
          }
      }
  
      T release() __attribute__((warn_unused_result)) {
          T localRef = mLocalRef;
          mLocalRef = NULL;
          return localRef;
      }
  
      T get() const { return mLocalRef; }
  
  // Some better C++11 support.
  #if __cplusplus >= 201103L
      // Move constructor.
      ScopedLocalRef(ScopedLocalRef&& s) : mEnv(s.mEnv), mLocalRef(s.release()) {}
  
      explicit ScopedLocalRef(JNIEnv* env) : mEnv(env), mLocalRef(nullptr) {}
  
      // We do not expose an empty constructor as it can easily lead to errors
      // using common idioms, e.g.:
      //   ScopedLocalRef<...> ref;
      //   ref.reset(...);
  
      // Move assignment operator.
      ScopedLocalRef& operator=(ScopedLocalRef&& s) {
          reset(s.release());
          mEnv = s.mEnv;
          return *this;
      }
  
      // Allows "if (scoped_ref == nullptr)"
      bool operator==(std::nullptr_t) const { return mLocalRef == nullptr; }
  
      // Allows "if (scoped_ref != nullptr)"
      bool operator!=(std::nullptr_t) const { return mLocalRef != nullptr; }
  #endif
  
  private:
      JNIEnv* mEnv;
      T mLocalRef;
  
      DISALLOW_COPY_AND_ASSIGN(ScopedLocalRef);
  };
  
  #endif  // SCOPED_LOCAL_REF_H_
  