1 /* 2 * Copyright (C) 2014 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 ART_RUNTIME_INTERPRETER_SAFE_MATH_H_ 18 #define ART_RUNTIME_INTERPRETER_SAFE_MATH_H_ 19 20 #include <functional> 21 #include <type_traits> 22 23 namespace art { 24 namespace interpreter { 25 26 // Declares a type which is the larger in bit size of the two template parameters. 27 template <typename T1, typename T2> 28 struct select_bigger { 29 typedef typename std::conditional<sizeof(T1) >= sizeof(T2), T1, T2>::type type; 30 }; 31 32 // Perform signed arithmetic Op on 'a' and 'b' with defined wrapping behavior. 33 template<template <typename OpT> class Op, typename T1, typename T2> 34 static inline typename select_bigger<T1, T2>::type SafeMath(T1 a, T2 b) { 35 typedef typename select_bigger<T1, T2>::type biggest_T; 36 typedef typename std::make_unsigned<biggest_T>::type unsigned_biggest_T; 37 static_assert(std::is_signed<T1>::value, "Expected T1 to be signed"); 38 static_assert(std::is_signed<T2>::value, "Expected T2 to be signed"); 39 unsigned_biggest_T val1 = static_cast<unsigned_biggest_T>(static_cast<biggest_T>(a)); 40 unsigned_biggest_T val2 = static_cast<unsigned_biggest_T>(b); 41 return static_cast<biggest_T>(Op<unsigned_biggest_T>()(val1, val2)); 42 } 43 44 // Perform signed a signed add on 'a' and 'b' with defined wrapping behavior. 45 template<typename T1, typename T2> 46 static inline typename select_bigger<T1, T2>::type SafeAdd(T1 a, T2 b) { 47 return SafeMath<std::plus>(a, b); 48 } 49 50 // Perform signed a signed substract on 'a' and 'b' with defined wrapping behavior. 51 template<typename T1, typename T2> 52 static inline typename select_bigger<T1, T2>::type SafeSub(T1 a, T2 b) { 53 return SafeMath<std::minus>(a, b); 54 } 55 56 // Perform signed a signed multiply on 'a' and 'b' with defined wrapping behavior. 57 template<typename T1, typename T2> 58 static inline typename select_bigger<T1, T2>::type SafeMul(T1 a, T2 b) { 59 return SafeMath<std::multiplies>(a, b); 60 } 61 62 } // namespace interpreter 63 } // namespace art 64 65 #endif // ART_RUNTIME_INTERPRETER_SAFE_MATH_H_ 66
