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      1 /*
      2  * Copyright (C) 2017 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_NULLABLE_PRIMITIVE_ARRAY_H
     18 #define SCOPED_NULLABLE_PRIMITIVE_ARRAY_H
     19 
     20 #include <jni.h>
     21 
     22 namespace android {
     23 
     24 #define ARRAY_TRAITS(ARRAY_TYPE, POINTER_TYPE, NAME)                                  \
     25 class NAME ## ArrayTraits {                                                           \
     26 public:                                                                               \
     27     static constexpr void getArrayRegion(JNIEnv* env, ARRAY_TYPE array, size_t start, \
     28                                          size_t len, POINTER_TYPE out) {              \
     29         env->Get ## NAME ## ArrayRegion(array, start, len, out);                      \
     30     }                                                                                 \
     31                                                                                       \
     32     static constexpr POINTER_TYPE getArrayElements(JNIEnv* env, ARRAY_TYPE array) {   \
     33         return env->Get ## NAME ## ArrayElements(array, nullptr);                     \
     34     }                                                                                 \
     35                                                                                       \
     36     static constexpr void releaseArrayElements(JNIEnv* env, ARRAY_TYPE array,         \
     37                                                POINTER_TYPE buffer, jint mode) {      \
     38         env->Release ## NAME ## ArrayElements(array, buffer, mode);                   \
     39     }                                                                                 \
     40 };                                                                                    \
     41 
     42 ARRAY_TRAITS(jbooleanArray, jboolean*, Boolean)
     43 ARRAY_TRAITS(jbyteArray, jbyte*, Byte)
     44 ARRAY_TRAITS(jcharArray, jchar*, Char)
     45 ARRAY_TRAITS(jdoubleArray, jdouble*, Double)
     46 ARRAY_TRAITS(jfloatArray, jfloat*, Float)
     47 ARRAY_TRAITS(jintArray, jint*, Int)
     48 ARRAY_TRAITS(jlongArray, jlong*, Long)
     49 ARRAY_TRAITS(jshortArray, jshort*, Short)
     50 
     51 #undef ARRAY_TRAITS
     52 
     53 template<typename JavaArrayType, typename PrimitiveType, class Traits, size_t preallocSize = 10>
     54 class ScopedArrayRO {
     55 public:
     56     ScopedArrayRO(JNIEnv* env, JavaArrayType javaArray) : mEnv(env), mJavaArray(javaArray) {
     57         if (mJavaArray == nullptr) {
     58             mSize = 0;
     59             mRawArray = nullptr;
     60         } else {
     61             mSize = mEnv->GetArrayLength(mJavaArray);
     62             if (mSize <= preallocSize) {
     63                 Traits::getArrayRegion(mEnv, mJavaArray, 0, mSize, mBuffer);
     64                 mRawArray = mBuffer;
     65             } else {
     66                 mRawArray = Traits::getArrayElements(mEnv, mJavaArray);
     67             }
     68         }
     69     }
     70 
     71     ~ScopedArrayRO() {
     72         if (mRawArray != nullptr && mRawArray != mBuffer) {
     73             Traits::releaseArrayElements(mEnv, mJavaArray, mRawArray, JNI_ABORT);
     74         }
     75     }
     76 
     77     const PrimitiveType* get() const { return mRawArray; }
     78     const PrimitiveType& operator[](size_t n) const { return mRawArray[n]; }
     79     size_t size() const { return mSize; }
     80 
     81 private:
     82     JNIEnv* const mEnv;
     83     JavaArrayType mJavaArray;
     84     PrimitiveType* mRawArray;
     85     size_t mSize;
     86     PrimitiveType mBuffer[preallocSize];
     87     DISALLOW_COPY_AND_ASSIGN(ScopedArrayRO);
     88 };
     89 
     90 // ScopedNullable***ArrayRO provide convenient read-only access to Java array from JNI code.
     91 // These accept nullptr. In that case, get() returns nullptr and size() returns 0.
     92 using ScopedNullableBooleanArrayRO = ScopedArrayRO<jbooleanArray, jboolean, BooleanArrayTraits>;
     93 using ScopedNullableByteArrayRO = ScopedArrayRO<jbyteArray, jbyte, ByteArrayTraits>;
     94 using ScopedNullableCharArrayRO = ScopedArrayRO<jcharArray, jchar, CharArrayTraits>;
     95 using ScopedNullableDoubleArrayRO = ScopedArrayRO<jdoubleArray, jdouble, DoubleArrayTraits>;
     96 using ScopedNullableFloatArrayRO = ScopedArrayRO<jfloatArray, jfloat, FloatArrayTraits>;
     97 using ScopedNullableIntArrayRO = ScopedArrayRO<jintArray, jint, IntArrayTraits>;
     98 using ScopedNullableLongArrayRO = ScopedArrayRO<jlongArray, jlong, LongArrayTraits>;
     99 using ScopedNullableShortArrayRO = ScopedArrayRO<jshortArray, jshort, ShortArrayTraits>;
    100 
    101 }  // namespace android
    102 
    103 #endif  // SCOPED_NULLABLE_PRIMITIVE_ARRAY_H
    104