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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_BYTES_H_included
     18 #define SCOPED_BYTES_H_included
     19 
     20 #include "JNIHelp.h"
     21 
     22 /**
     23  * ScopedBytesRO and ScopedBytesRW attempt to paper over the differences between byte[]s and
     24  * ByteBuffers. This in turn helps paper over the differences between non-direct ByteBuffers backed
     25  * by byte[]s, direct ByteBuffers backed by bytes[]s, and direct ByteBuffers not backed by byte[]s.
     26  * (On Android, this last group only contains MappedByteBuffers.)
     27  */
     28 template<bool readOnly>
     29 class ScopedBytes {
     30 public:
     31     ScopedBytes(JNIEnv* env, jobject object)
     32     : mEnv(env), mObject(object), mByteArray(NULL), mPtr(NULL)
     33     {
     34         if (mObject == NULL) {
     35             jniThrowNullPointerException(mEnv, NULL);
     36         } else if (mEnv->IsInstanceOf(mObject, JniConstants::byteArrayClass)) {
     37             mByteArray = reinterpret_cast<jbyteArray>(mObject);
     38             mPtr = mEnv->GetByteArrayElements(mByteArray, NULL);
     39         } else {
     40             mPtr = reinterpret_cast<jbyte*>(mEnv->GetDirectBufferAddress(mObject));
     41         }
     42     }
     43 
     44     ~ScopedBytes() {
     45         if (mByteArray != NULL) {
     46             mEnv->ReleaseByteArrayElements(mByteArray, mPtr, readOnly ? JNI_ABORT : 0);
     47         }
     48     }
     49 
     50 private:
     51     JNIEnv* mEnv;
     52     jobject mObject;
     53     jbyteArray mByteArray;
     54 
     55 protected:
     56     jbyte* mPtr;
     57 
     58 private:
     59     // Disallow copy and assignment.
     60     ScopedBytes(const ScopedBytes&);
     61     void operator=(const ScopedBytes&);
     62 };
     63 
     64 class ScopedBytesRO : public ScopedBytes<true> {
     65 public:
     66     ScopedBytesRO(JNIEnv* env, jobject object) : ScopedBytes<true>(env, object) {}
     67     const jbyte* get() const {
     68         return mPtr;
     69     }
     70 };
     71 
     72 class ScopedBytesRW : public ScopedBytes<false> {
     73 public:
     74     ScopedBytesRW(JNIEnv* env, jobject object) : ScopedBytes<false>(env, object) {}
     75     jbyte* get() {
     76         return mPtr;
     77     }
     78 };
     79 
     80 #endif  // SCOPED_BYTES_H_included
     81