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
ARRAY_TRAITS(jbooleanArray,jboolean *,Boolean)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