1 /* 2 * Copyright (C) 2019 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 UTIL_CHRE_NESTED_DATA_PTR_H_ 18 #define UTIL_CHRE_NESTED_DATA_PTR_H_ 19 20 namespace chre { 21 22 /** 23 * A template that provides the ability to store data inside of a void pointer 24 * to avoid allocating space on the heap in the case where the data is smaller 25 * than the size of a void pointer. 26 */ 27 template <typename DataType> 28 union NestedDataPtr { NestedDataPtr(DataType nestedData)29 NestedDataPtr(DataType nestedData) : data(nestedData) { 30 assertSize(); 31 } 32 NestedDataPtr()33 explicit NestedDataPtr() { 34 assertSize(); 35 } 36 void *dataPtr; 37 DataType data; 38 39 private: 40 /** 41 * Ensures both constructors make the same assertion about the size of the 42 * struct. 43 */ assertSize()44 void assertSize() { 45 static_assert(sizeof(NestedDataPtr<DataType>) == sizeof(void *), 46 "Size of NestedDataPtr must be equal to that of void *"); 47 } 48 }; 49 50 } // namespace chre 51 52 #endif // UTIL_CHRE_NESTED_DATA_PTR_H_