| // Licensed to the Apache Software Foundation (ASF) under one |
| // or more contributor license agreements. See the NOTICE file |
| // distributed with this work for additional information |
| // regarding copyright ownership. The ASF licenses this file |
| // to you under the Apache License, Version 2.0 (the |
| // "License"); you may not use this file except in compliance |
| // with the License. You may obtain a copy of the License at |
| // |
| // http://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, |
| // software distributed under the License is distributed on an |
| // "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| // KIND, either express or implied. See the License for the |
| // specific language governing permissions and limitations |
| // under the License. |
| // |
| // Inline functions for doing overflow-safe operations on integers. |
| // These should be used when doing bounds checks on user-provided data, |
| // for example. |
| // See also: https://www.securecoding.cert.org/confluence/display/cplusplus/INT32-CPP.+Ensure+that+operations+on+signed+integers+do+not+result+in+overflow |
| #ifndef KUDU_UTIL_SAFE_MATH_H |
| #define KUDU_UTIL_SAFE_MATH_H |
| |
| #include "kudu/gutil/mathlimits.h" |
| |
| namespace kudu { |
| |
| namespace safe_math_internal { |
| |
| // Template which is specialized for signed and unsigned types separately. |
| template<typename Type, bool is_signed> |
| struct WithOverflowCheck { |
| }; |
| |
| |
| // Specialization for signed types. |
| template<typename Type> |
| struct WithOverflowCheck<Type, true> { |
| static inline Type Add(Type a, Type b, bool *overflowed) { |
| // Implementation from the CERT article referenced in the file header. |
| *overflowed = (((a > 0) && (b > 0) && (a > (MathLimits<Type>::kMax - b))) || |
| ((a < 0) && (b < 0) && (a < (MathLimits<Type>::kMin - b)))); |
| return a + b; |
| } |
| }; |
| |
| // Specialization for unsigned types. |
| template<typename Type> |
| struct WithOverflowCheck<Type, false> { |
| static inline Type Add(Type a, Type b, bool *overflowed) { |
| Type ret = a + b; |
| *overflowed = ret < a; |
| return a + b; |
| } |
| }; |
| |
| } // namespace safe_math_internal |
| |
| // Add 'a' and 'b', and set *overflowed to true if overflow occured. |
| template<typename Type> |
| inline Type AddWithOverflowCheck(Type a, Type b, bool *overflowed) { |
| // Pick the right specialization based on whether Type is signed. |
| typedef safe_math_internal::WithOverflowCheck<Type, MathLimits<Type>::kIsSigned> my_struct; |
| return my_struct::Add(a, b, overflowed); |
| } |
| |
| } // namespace kudu |
| #endif |