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      1 /*
      2  * Copyright (C) 2010 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 #ifndef SCOPED_LOCAL_REF_H_included
     18 #define SCOPED_LOCAL_REF_H_included
     19 
     20 #include "jni.h"
     21 
     22 #include <stddef.h>
     23 
     24 // A smart pointer that deletes a JNI local reference when it goes out of scope.
     25 template<typename T>
     26 class ScopedLocalRef {
     27 public:
     28     ScopedLocalRef(JNIEnv* env, T localRef) : mEnv(env), mLocalRef(localRef) {
     29     }
     30 
     31     ~ScopedLocalRef() {
     32         reset();
     33     }
     34 
     35     void reset(T ptr = NULL) {
     36         if (ptr != mLocalRef) {
     37             if (mLocalRef != NULL) {
     38                 mEnv->DeleteLocalRef(mLocalRef);
     39             }
     40             mLocalRef = ptr;
     41         }
     42     }
     43 
     44     T release() __attribute__((warn_unused_result)) {
     45         T localRef = mLocalRef;
     46         mLocalRef = NULL;
     47         return localRef;
     48     }
     49 
     50     T get() const {
     51         return mLocalRef;
     52     }
     53 
     54 private:
     55     JNIEnv* mEnv;
     56     T mLocalRef;
     57 
     58     // Disallow copy and assignment.
     59     ScopedLocalRef(const ScopedLocalRef&);
     60     void operator=(const ScopedLocalRef&);
     61 };
     62 
     63 #endif  // SCOPED_LOCAL_REF_H_included
     64