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
22namespace android {
23
24#define ARRAY_TRAITS(ARRAY_TYPE, POINTER_TYPE, NAME)                                  \
25class NAME ## ArrayTraits {                                                           \
26public:                                                                               \
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
42ARRAY_TRAITS(jbooleanArray, jboolean*, Boolean)
43ARRAY_TRAITS(jbyteArray, jbyte*, Byte)
44ARRAY_TRAITS(jcharArray, jchar*, Char)
45ARRAY_TRAITS(jdoubleArray, jdouble*, Double)
46ARRAY_TRAITS(jfloatArray, jfloat*, Float)
47ARRAY_TRAITS(jintArray, jint*, Int)
48ARRAY_TRAITS(jlongArray, jlong*, Long)
49ARRAY_TRAITS(jshortArray, jshort*, Short)
50
51#undef ARRAY_TRAITS
52
53template<typename JavaArrayType, typename PrimitiveType, class Traits, size_t preallocSize = 10>
54class ScopedArrayRO {
55public:
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
81private:
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.
92using ScopedNullableBooleanArrayRO = ScopedArrayRO<jbooleanArray, jboolean, BooleanArrayTraits>;
93using ScopedNullableByteArrayRO = ScopedArrayRO<jbyteArray, jbyte, ByteArrayTraits>;
94using ScopedNullableCharArrayRO = ScopedArrayRO<jcharArray, jchar, CharArrayTraits>;
95using ScopedNullableDoubleArrayRO = ScopedArrayRO<jdoubleArray, jdouble, DoubleArrayTraits>;
96using ScopedNullableFloatArrayRO = ScopedArrayRO<jfloatArray, jfloat, FloatArrayTraits>;
97using ScopedNullableIntArrayRO = ScopedArrayRO<jintArray, jint, IntArrayTraits>;
98using ScopedNullableLongArrayRO = ScopedArrayRO<jlongArray, jlong, LongArrayTraits>;
99using ScopedNullableShortArrayRO = ScopedArrayRO<jshortArray, jshort, ShortArrayTraits>;
100
101}  // namespace android
102
103#endif  // SCOPED_NULLABLE_PRIMITIVE_ARRAY_H
104