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:
ScopedLocalRef(JNIEnv * env,T localRef)29     ScopedLocalRef(JNIEnv* env, T localRef) : mEnv(env), mLocalRef(localRef) {
30     }
31 
~ScopedLocalRef()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 
release()45     T release() __attribute__((warn_unused_result)) {
46         T localRef = mLocalRef;
47         mLocalRef = NULL;
48         return localRef;
49     }
50 
get()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