| // Copyright 2013 Cloudera, Inc. |
| // |
| // Licensed 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 |