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:
ScopedLocalRef(JNIEnv * env,T localRef)28     ScopedLocalRef(JNIEnv* env, T localRef) : mEnv(env), mLocalRef(localRef) {
29     }
30 
~ScopedLocalRef()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 
release()44     T release() __attribute__((warn_unused_result)) {
45         T localRef = mLocalRef;
46         mLocalRef = NULL;
47         return localRef;
48     }
49 
get()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