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>
SafeMath(T1 a,T2 b)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>
SafeAdd(T1 a,T2 b)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>
SafeSub(T1 a,T2 b)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>
SafeMul(T1 a,T2 b)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