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 using type = std::conditional_t<sizeof(T1) >= sizeof(T2), T1, T2>;
30 };
31 template <typename T1, typename T2>
32 using select_bigger_t = typename select_bigger<T1, T2>::type;
33
34 // Perform signed arithmetic Op on 'a' and 'b' with defined wrapping behavior.
35 template<template <typename OpT> class Op, typename T1, typename T2>
SafeMath(T1 a,T2 b)36 static inline select_bigger_t<T1, T2> SafeMath(T1 a, T2 b) {
37 using biggest_T = select_bigger_t<T1, T2>;
38 using unsigned_biggest_T = std::make_unsigned_t<biggest_T>;
39 static_assert(std::is_signed_v<T1>, "Expected T1 to be signed");
40 static_assert(std::is_signed_v<T2>, "Expected T2 to be signed");
41 unsigned_biggest_T val1 = static_cast<unsigned_biggest_T>(static_cast<biggest_T>(a));
42 unsigned_biggest_T val2 = static_cast<unsigned_biggest_T>(b);
43 return static_cast<biggest_T>(Op<unsigned_biggest_T>()(val1, val2));
44 }
45
46 // Perform a signed add on 'a' and 'b' with defined wrapping behavior.
47 template<typename T1, typename T2>
SafeAdd(T1 a,T2 b)48 static inline select_bigger_t<T1, T2> SafeAdd(T1 a, T2 b) {
49 return SafeMath<std::plus>(a, b);
50 }
51
52 // Perform a signed substract on 'a' and 'b' with defined wrapping behavior.
53 template<typename T1, typename T2>
SafeSub(T1 a,T2 b)54 static inline select_bigger_t<T1, T2> SafeSub(T1 a, T2 b) {
55 return SafeMath<std::minus>(a, b);
56 }
57
58 // Perform a signed multiply on 'a' and 'b' with defined wrapping behavior.
59 template<typename T1, typename T2>
SafeMul(T1 a,T2 b)60 static inline select_bigger_t<T1, T2> SafeMul(T1 a, T2 b) {
61 return SafeMath<std::multiplies>(a, b);
62 }
63
64 } // namespace interpreter
65 } // namespace art
66
67 #endif // ART_RUNTIME_INTERPRETER_SAFE_MATH_H_
68