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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 #include "JNIHelp.h"  // for DISALLOW_COPY_AND_ASSIGN.
     24 
     25 // A smart pointer that deletes a JNI local reference when it goes out of scope.
     26 template<typename T>
     27 class ScopedLocalRef {
     28 public:
     29     ScopedLocalRef(JNIEnv* env, T localRef) : mEnv(env), mLocalRef(localRef) {
     30     }
     31 
     32     ~ScopedLocalRef() {
     33         reset();
     34     }
     35 
     36     void reset(T ptr = NULL) {
     37         if (ptr != mLocalRef) {
     38             if (mLocalRef != NULL) {
     39                 mEnv->DeleteLocalRef(mLocalRef);
     40             }
     41             mLocalRef = ptr;
     42         }
     43     }
     44 
     45     T release() __attribute__((warn_unused_result)) {
     46         T localRef = mLocalRef;
     47         mLocalRef = NULL;
     48         return localRef;
     49     }
     50 
     51     T get() const {
     52         return mLocalRef;
     53     }
     54 
     55 private:
     56     JNIEnv* const mEnv;
     57     T mLocalRef;
     58 
     59     DISALLOW_COPY_AND_ASSIGN(ScopedLocalRef);
     60 };
     61 
     62 #endif  // SCOPED_LOCAL_REF_H_included
     63